• Low Level Gamma Radiation

    From Mike Monett@21:1/5 to All on Sun Jun 5 23:07:15 2022
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks





    --
    MRM

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  • From bitrex@21:1/5 to bitrex on Sun Jun 5 21:25:10 2022
    On 6/5/2022 9:24 PM, bitrex wrote:
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level
    background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick
    drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    There's a long decay chain from naturally-occurring thallium 232

    Er, Thorium 232, not thallium

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  • From bitrex@21:1/5 to Mike Monett on Sun Jun 5 21:24:32 2022
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick drop near zero. Scouring google, I was unable to find any source that explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    There's a long decay chain from naturally-occurring thallium 232 and
    uranium 238 down to stable lead, and a number of steps in the chain
    produce a gamma photon

    --- SoupGate-Win32 v1.05
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  • From Ricky@21:1/5 to Mike Monett on Sun Jun 5 18:56:58 2022
    On Sunday, June 5, 2022 at 7:07:22 PM UTC-4, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick drop near zero. Scouring google, I was unable to find any source that explained it. What mechanism could produce such weak gamma or x-rays?

    What do you know of the calibration of the unit itself? Does it have the equivalent of frequency response?

    --

    Rick C.

    - Get 1,000 miles of free Supercharging
    - Tesla referral code - https://ts.la/richard11209

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  • From Ricky@21:1/5 to bitrex on Sun Jun 5 19:12:59 2022
    On Sunday, June 5, 2022 at 9:25:18 PM UTC-4, bitrex wrote:
    On 6/5/2022 9:24 PM, bitrex wrote:
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level
    background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick
    drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    There's a long decay chain from naturally-occurring thallium 232
    Er, Thorium 232, not thallium

    When I look at the decay chain, I don't see any gamma emissions. Is this in a more rare decay event?

    --

    Rick C.

    + Get 1,000 miles of free Supercharging
    + Tesla referral code - https://ts.la/richard11209

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  • From bitrex@21:1/5 to Ricky on Sun Jun 5 22:35:45 2022
    On 6/5/2022 10:12 PM, Ricky wrote:
    On Sunday, June 5, 2022 at 9:25:18 PM UTC-4, bitrex wrote:
    On 6/5/2022 9:24 PM, bitrex wrote:
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level
    background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick
    drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    There's a long decay chain from naturally-occurring thallium 232
    Er, Thorium 232, not thallium

    When I look at the decay chain, I don't see any gamma emissions. Is this in a more rare decay event?


    For thorium the gory details are here:

    <https://pubs.usgs.gov/of/2004/1050/thorium.htm>

    --- SoupGate-Win32 v1.05
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  • From bitrex@21:1/5 to Ricky on Sun Jun 5 22:40:46 2022
    On 6/5/2022 9:56 PM, Ricky wrote:
    On Sunday, June 5, 2022 at 7:07:22 PM UTC-4, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I >> was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level >> background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick >> drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    What do you know of the calibration of the unit itself? Does it have the equivalent of frequency response?


    For his device it looks like the plot is a histogram of absorbed energy,
    and can be set on the 1 MeV, 2 MeV and 3 MeV scales, see top of page 19:

    <https://scan-electronics.com/files/EN/RadiaCode/SFX/RC-101_Device_Manual.pdf>

    If the widget is set on the 1 MeV scale and the left extreme of the X
    axis is about 100 keV and the right hand extreme is about 1 MeV, and the amplitude on a log plot it seems somewhat congruent with page 4 here:

    <https://arxiv.org/ftp/arxiv/papers/1305/1305.2572.pdf>

    Seems to be detecting background radiation if that's how it's set up,
    situation normal I think?

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  • From Anthony William Sloman@21:1/5 to Mike Monett on Sun Jun 5 21:54:20 2022
    On Monday, June 6, 2022 at 1:07:22 AM UTC+2, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick drop near zero. Scouring google, I was unable to find any source that explained it. What mechanism could produce such weak gamma or x-rays?

    How about

    https://en.wikipedia.org/wiki/Potassium-40

    I seem to remember that it is the most important gamma ray source in regular terrestrial environments.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
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  • From whit3rd@21:1/5 to Mike Monett on Sun Jun 5 23:06:04 2022
    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick drop near zero. Scouring google, I was unable to find any source that explained it. What mechanism could produce such weak gamma or x-rays?

    As a general rule, X-rays excite fluorescences in lots of materials; unless you have only low-atomic-number elements around, some of those
    fluuorescences will be in the low X-ray region, and would presumably be
    a low-energy high-count source that penetrates the window of your sensor (whatever the sensor is). For some sources, secondary radiation
    is the easiest to detect (a detector can be transparent to high energy photons).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to whit3rd@gmail.com on Mon Jun 6 09:36:43 2022
    whit3rd <whit3rd@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick drop near zero. Scouring google, I was unable to find any source
    that explained it. What mechanism could produce such weak gamma or
    x-rays?

    As a general rule, X-rays excite fluorescences in lots of materials;
    unless you have only low-atomic-number elements around, some of those fluuorescences will be in the low X-ray region, and would presumably be
    a low-energy high-count source that penetrates the window of your
    sensor (whatever the sensor is). For some sources, secondary radiation
    is the easiest to detect (a detector can be transparent to high energy photons).

    Thanks for your reply. As a beginner, it is easy to get confused. I'm
    confused.

    To get more information, I decided to get the spectrum of Potassium-40 by extending the scale of the Radiacode to 3MV, and sitting it on 3 jars of Windsor Salt Free shown here:

    https://windsorsalt.com/product/salt-free/

    Wikipedia gives the following information on Potassium-40 decay:

    Potassium-40 is a rare example of a nuclide that undergoes both
    types of beta decay. In about 89.28% of events, it decays to
    calcium-40 (40Ca) with emission of a beta particle (an electron)
    with a maximum energy of 1.31 MeV and an antineutrino. In about
    10.72% of events, it decays to argon-40 (40Ar) by electron capture
    (EC), with the emission of a neutrino and then a 1.460 MeV gamma
    ray.[1] The radioactive decay of this particular isotope explains
    the large abundance of argon (nearly 1%) in the Earth's atmosphere,
    as well as prevalence of 40Ar over other isotopes. Very rarely
    (0.001% of events), it decays to 40Ar by emitting a positron (?+)
    and a neutrino.[2]

    https://en.wikipedia.org/wiki/Potassium-40

    The detector in the Radiacode is a 1 cm cube of Thallium Doped Caesium
    Iodide (CsI:TI). This is a very popular scintillation detector and has good performance when coupled to a avalanch diode.

    The Potassium-40 spectrum is here:

    https://www.mrmonett.com/POTASS40.JPG

    You can see a slight hump at 1.31 MeV and a clearer hump at 1.46 MeV. This
    is very satisfying, but it's not clear how the hump at 1.31 MeV is
    produced. Is the Radiacode sensitive to beta decay?

    Also notice the shelf extending back to zero energy. Where does this come
    from?

    You mentioned above "X-rays excite fluorescences in lots of materials".

    But the sources are presumably beta and gamma. Where is the fluorescence
    coming from?

    Thanks for your help!


    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From Anthony William Sloman@21:1/5 to Mike Monett on Mon Jun 6 03:38:12 2022
    On Monday, June 6, 2022 at 11:36:51 AM UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick drop near zero. Scouring google, I was unable to find any source
    that explained it. What mechanism could produce such weak gamma or
    x-rays?

    As a general rule, X-rays excite fluorescences in lots of materials;
    unless you have only low-atomic-number elements around, some of those fluuorescences will be in the low X-ray region, and would presumably be
    a low-energy high-count source that penetrates the window of your
    sensor (whatever the sensor is). For some sources, secondary radiation
    is the easiest to detect (a detector can be transparent to high energy photons).
    Thanks for your reply. As a beginner, it is easy to get confused. I'm confused.

    To get more information, I decided to get the spectrum of Potassium-40 by extending the scale of the Radiacode to 3MV, and sitting it on 3 jars of Windsor Salt Free shown here:

    https://windsorsalt.com/product/salt-free/

    Wikipedia gives the following information on Potassium-40 decay:

    Potassium-40 is a rare example of a nuclide that undergoes both
    types of beta decay. In about 89.28% of events, it decays to
    calcium-40 (40Ca) with emission of a beta particle (an electron)
    with a maximum energy of 1.31 MeV and an antineutrino. In about
    10.72% of events, it decays to argon-40 (40Ar) by electron capture
    (EC), with the emission of a neutrino and then a 1.460 MeV gamma
    ray.[1] The radioactive decay of this particular isotope explains
    the large abundance of argon (nearly 1%) in the Earth's atmosphere,
    as well as prevalence of 40Ar over other isotopes. Very rarely
    (0.001% of events), it decays to 40Ar by emitting a positron (?+)
    and a neutrino.[2]

    https://en.wikipedia.org/wiki/Potassium-40

    The detector in the Radiacode is a 1 cm cube of Thallium Doped Caesium
    Iodide (CsI:TI). This is a very popular scintillation detector and has good performance when coupled to a avalanch diode.

    The Potassium-40 spectrum is here:

    https://www.mrmonett.com/POTASS40.JPG

    You can see a slight hump at 1.31 MeV and a clearer hump at 1.46 MeV. This
    is very satisfying, but it's not clear how the hump at 1.31 MeV is
    produced. Is the Radiacode sensitive to beta decay?

    Also notice the shelf extending back to zero energy. Where does this come from?

    ""In about 89.28% of events, it decays to calcium-40 (40Ca) with emission of a beta particle (an electron) with a maximum energy of 1.31 MeV and an antineutrino."

    The neutrino was pretty much invented to explain why the electron came out with a range of energies - the neutrino carried away the rest of the energy.

    You mentioned above "X-rays excite fluorescences in lots of materials".

    But the sources are presumably beta and gamma. Where is the fluorescence coming from?

    Fluorescence can also be excited by energetic electrons - "beta rays". Gamma ray is just another name for an X-ray. It took a while for us to understand that they were both energetic photons.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to Anthony William Sloman on Mon Jun 6 08:49:26 2022
    On 6/6/2022 6:38 AM, Anthony William Sloman wrote:
    On Monday, June 6, 2022 at 11:36:51 AM UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick drop near zero. Scouring google, I was unable to find any source >>>> that explained it. What mechanism could produce such weak gamma or
    x-rays?

    As a general rule, X-rays excite fluorescences in lots of materials;
    unless you have only low-atomic-number elements around, some of those
    fluuorescences will be in the low X-ray region, and would presumably be
    a low-energy high-count source that penetrates the window of your
    sensor (whatever the sensor is). For some sources, secondary radiation
    is the easiest to detect (a detector can be transparent to high energy
    photons).
    Thanks for your reply. As a beginner, it is easy to get confused. I'm
    confused.

    To get more information, I decided to get the spectrum of Potassium-40 by
    extending the scale of the Radiacode to 3MV, and sitting it on 3 jars of
    Windsor Salt Free shown here:

    https://windsorsalt.com/product/salt-free/

    Wikipedia gives the following information on Potassium-40 decay:

    Potassium-40 is a rare example of a nuclide that undergoes both
    types of beta decay. In about 89.28% of events, it decays to
    calcium-40 (40Ca) with emission of a beta particle (an electron)
    with a maximum energy of 1.31 MeV and an antineutrino. In about
    10.72% of events, it decays to argon-40 (40Ar) by electron capture
    (EC), with the emission of a neutrino and then a 1.460 MeV gamma
    ray.[1] The radioactive decay of this particular isotope explains
    the large abundance of argon (nearly 1%) in the Earth's atmosphere,
    as well as prevalence of 40Ar over other isotopes. Very rarely
    (0.001% of events), it decays to 40Ar by emitting a positron (?+)
    and a neutrino.[2]

    https://en.wikipedia.org/wiki/Potassium-40

    The detector in the Radiacode is a 1 cm cube of Thallium Doped Caesium
    Iodide (CsI:TI). This is a very popular scintillation detector and has good >> performance when coupled to a avalanch diode.

    The Potassium-40 spectrum is here:

    https://www.mrmonett.com/POTASS40.JPG

    You can see a slight hump at 1.31 MeV and a clearer hump at 1.46 MeV. This >> is very satisfying, but it's not clear how the hump at 1.31 MeV is
    produced. Is the Radiacode sensitive to beta decay?

    Also notice the shelf extending back to zero energy. Where does this come
    from?

    ""In about 89.28% of events, it decays to calcium-40 (40Ca) with emission of a beta particle (an electron) with a maximum energy of 1.31 MeV and an antineutrino."

    The neutrino was pretty much invented to explain why the electron came out with a range of energies - the neutrino carried away the rest of the energy.

    And in the more modern physics it helps conserve spin and lepton
    number/flavor, they're on the lookout for something like muon ->
    electron + gamma where the energies are correct but lepton flavor
    conservation is violated. Haven't seen it yet AFAIK

    You mentioned above "X-rays excite fluorescences in lots of materials".

    But the sources are presumably beta and gamma. Where is the fluorescence coming from?

    Fluorescence can also be excited by energetic electrons - "beta rays". Gamma ray is just another name for an X-ray. It took a while for us to understand that they were both energetic photons.


    I think in particle physics all photons that come from decay tend to be
    called "gamma" even if they overlap with the X-ray's domain below about
    100 keV.

    At the bottom of page 4:

    <http://www-odp.tamu.edu/publications/tnotes/tn26/CHAP5.PDF>

    "About 90% of the counts come from the low-energy part of the
    spectrum, which is degraded by Compton scattering." I think this means
    the area around 100 keV in the background radiation is very noisy with contributions from the scattered photons of lots of stuff.

    --- SoupGate-Win32 v1.05
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  • From Martin Brown@21:1/5 to Ricky on Mon Jun 6 14:01:37 2022
    On 06/06/2022 03:12, Ricky wrote:
    On Sunday, June 5, 2022 at 9:25:18 PM UTC-4, bitrex wrote:
    On 6/5/2022 9:24 PM, bitrex wrote:
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level
    background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick
    drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    Energy I presume. There will be a mix of elements contributing to the background and some will have characteristic lines. Potassium nitrate or instant coffee may have enough K40 in to allow some calibration.

    https://gammaspectacular.com/blue/k-40-gamma-spectrum#

    There's a long decay chain from naturally-occurring thallium 232
    Er, Thorium 232, not thallium

    When I look at the decay chain, I don't see any gamma emissions. Is this in a more rare decay event?

    No they are common but they occur in conjunction (shortly after) either
    an alpha or beta decay due to the recoil and necessary rearrangement of
    the remaining components of the atomic nucleus.

    Just after the alpha or beta particle escapes the nucleus is in an
    excited state with a hole in it where the emitted particle once sat.
    Gamma ray(s) get emitted as it rearranges back to its new ground state.

    Only emissions that alter the atomic number and/or mass are normally
    shown on decay chain diagrams.

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
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  • From Dimiter_Popoff@21:1/5 to bitrex on Mon Jun 6 16:50:30 2022
    On 6/6/2022 4:24, bitrex wrote:
    On 6/5/2022 7:07 PM, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I
    was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low
    level
    background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and
    quick
    drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    Thanks

    What does the X axis represent?

    There's a long decay chain from naturally-occurring thallium 232 and
    uranium 238 down to stable lead, and a number of steps in the chain
    produce a gamma photon





    X-axis should be energy, the spectrum looks right for it to be that.
    Clearly with such a device you won't see much energy resolution,
    probably the 1461 keV line of 40K won't be visible even if it were
    within the energy range of the device (probably not, by the size of it
    the detector would be too small for that; buy a kilogram of bananas and
    measure it to see if that's the case).
    Here is what the 40K peak looks like (the marker, a red X, is on top
    of it): http://tgi-sci.com/tgi/nmc3spc.htm#nmc3demo

    If the banana pack yields higher counts per second and no visible peak
    (which is what I expect you will see) it will be due to Compton etc.,
    others may be more familiar with the details, I just design the
    spectrometers and have learnt only as much as it takes to do the
    measurement and the evaluation of the spectra....

    ======================================================
    Dimiter Popoff, TGI http://www.tgi-sci.com ====================================================== http://www.flickr.com/photos/didi_tgi/

    --- SoupGate-Win32 v1.05
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  • From Dave Platt@21:1/5 to All on Mon Jun 6 15:08:47 2022
    In article <d14769a6-4607-49b7-b2c3-0f9e5312bacen@googlegroups.com>,

    I wonder what the spectrum curve is saying, particularly the rise and quick >> drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?

    As a general rule, X-rays excite fluorescences in lots of materials; unless you
    have only low-atomic-number elements around, some of those
    fluuorescences will be in the low X-ray region, and would presumably be
    a low-energy high-count source that penetrates the window of your sensor >(whatever the sensor is).

    Correct. In fact, when building high-quality isolation chambers for
    measuring gamma specta (the gamma equivalent of a Faraday cage, in
    effect) it's necessary to use a layered approach. The outer layer is
    usually lead, but when gammas from outside hit the lead it will
    fluoresce in the X-ray spectrum. So, inside the lead, you have
    another layer which effectively absorbs those X-rays... and *it* may
    fluoresce at a lower-energy X-ray frequency, so you may need a third
    layer of yet another material.

    I've used a home-made gamma spectrometer (NaI crystal, a PMT, and my
    own electronics) to look at some naturally-occurring radioactive
    materials. One interesting source is some monazite sand from a local
    beach - it has a significant amount of thorium in the mix and I get an appreciable count rate if I lower the sensor down onto a big box of
    the stuff.

    The spectrum does show the expected gamma-ray peaks for thorium, but
    they're not as "clean" as for a purer thorium sample and there's a
    strong continuum of lower-energy gamma/X-rays just as the OP's photo
    showed. My understanding is that this is "degraded" gamma - in other
    words, gamma-induced fluorescence occurring within the sample itself.
    Reducing or eliminating this requires flattening out the sample (so
    that there's a better chance for a thorium-generated gamma to hit the
    NaI sensor before it hits an atom of the sand and causes
    fluorescence).

    One spectrum I looked at was that of a "quantum energy pendant" that
    can be bought inexpensively on eBay and elsewhere. It's supposedly a
    natural negative-ion source with semi-mystical healing powers. What
    it actually seems to be is a pendant made from a natural ore rich in
    thorium. It emits "negative ions" in the form of beta-decay
    electrons, and reportedly its emission rates are high enough that if
    you wear it next to your skin every day you'd exceed certain government
    safety limits for ionizing-radiation exposure in that area (possible
    cancer risk or a localized radiation burn).

    http://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    The green trace is the background radiation level in my work
    area. The purple trace is from sampling for the same amount
    of time, with the pendant in contact with the NaI sensor. The
    thorium-228 peak is clear, there's another from lead and radium
    decay daughters, and the actinium-228 peak is also visible.

    With another sensor and voltage setting, the background signal
    from potassium-40 is visible... and bringing a bottle of
    Morton "lite salt" or a bag of water-softener potassium
    chloride around the sensor really makes it obvious!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From amdx@21:1/5 to Anthony William Sloman on Tue Jun 7 12:36:32 2022
    On 6/5/2022 11:54 PM, Anthony William Sloman wrote:
    On Monday, June 6, 2022 at 1:07:22 AM UTC+2, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I >> was surprised to see it made it.

    After learning how to operate it, I began to be curious about the low level >> background radiation. This is shown in the photo at

    https://www.mrmonett.com/RADIACOD.JPG

    I wonder what the spectrum curve is saying, particularly the rise and quick >> drop near zero. Scouring google, I was unable to find any source that
    explained it. What mechanism could produce such weak gamma or x-rays?
    How about

    https://en.wikipedia.org/wiki/Potassium-40

    I seem to remember that it is the most important gamma ray source in regular terrestrial environments.

      Yep, used to built bore hole equipment that explored what layers were below.
    One piece was a gamma ray detector. This description doesn't mean much
    to me anymore,
    if it ever did, but but here are some down hole gamma graphs.
    https://www.kgs.ku.edu/Publications/Bulletins/LA/03_gamma.html

                                   Mikek


    --
    This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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  • From John Miles, KE5FX@21:1/5 to Mike Monett on Sun Jun 12 12:19:21 2022
    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

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  • From Dimiter_Popoff@21:1/5 to All on Sun Jun 12 23:06:28 2022
    On 6/12/2022 22:19, John Miles, KE5FX wrote:
    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the sanctions, I >> was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

    This is incredibly cheap indeed. I thought even Hamamatsu can't make
    PMT-s that small :). (4 years ago they sold us some of their R12421 at
    450 euro each IIRC).
    But just the scintillation crystal would probably cost much more,
    let alone the PMT at Hamamtsu.... No idea how they manage that.

    --- SoupGate-Win32 v1.05
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  • From Mike Monett@21:1/5 to jmiles@gmail.com on Sat Jun 25 18:16:39 2022
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and mail it
    to me? I can pay you via Paypal. Thanks.



    --
    MRM

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  • From Jan Panteltje@21:1/5 to spamme@not.com on Sun Jun 26 13:29:08 2022
    On a sunny day (Sat, 25 Jun 2022 18:16:39 -0000 (UTC)) it happened Mike Monett <spamme@not.com> wrote in <XnsAEC1913D785B5idtokenpost@144.76.35.252>:

    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and mail it >to me? I can pay you via Paypal. Thanks.

    I just found this on tomshardware.com:
    https://www.tomshardware.com/news/raspberry-pi-pico-detects-radiation
    nice spectra (github link) https://github.com/Open-Gamma-Project/Open-Gamma-Detector

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  • From John Miles, KE5FX@21:1/5 to Mike Monett on Sun Jun 26 15:53:09 2022
    On Saturday, June 25, 2022 at 11:16:45 AM UTC-7, Mike Monett wrote:
    I tried to order one. Does not ship to Canada. Can you order one and mail it to me? I can pay you via Paypal. Thanks.

    Maybe. I'll have to surf through the Commerce and ITAR lists to see if there's a reason why the seller doesn't ship to Canada. Shifty folk, Canadians.

    (It'll be a few days before I have time to deal with it, for various reasons.)

    -- john, KE5FX

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  • From Mike Monett@21:1/5 to jmiles@gmail.com on Mon Jun 27 00:23:35 2022
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Saturday, June 25, 2022 at 11:16:45 AM UTC-7, Mike Monett wrote:
    I tried to order one. Does not ship to Canada. Can you order one and
    mail it to me? I can pay you via Paypal. Thanks.

    Maybe. I'll have to surf through the Commerce and ITAR lists to see if there's a reason why the seller doesn't ship to Canada. Shifty folk, Canadians.

    (It'll be a few days before I have time to deal with it, for various reasons.)

    -- john, KE5FX

    That's fantastic. Thanks.

    A lot of US vendors don't want to ship to Canada. But the majority do ship
    with no problem. Spending time to find out why may give mixed results. I
    can probably ask the vendor what his reasons are. In the meantime, my main
    goal is to get a copy of his model before he runs out or gives up.

    I will send my name and address to your gmail address. Again, thanks.

    Mike



    --
    MRM

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  • From Phil Hobbs@21:1/5 to Mike Monett on Mon Jun 27 07:42:23 2022
    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and mail it to me? I can pay you via Paypal. Thanks.

    For any serious use, I'd budget for a replacement PMT. They age out
    after several years, which is probably why these assemblies were
    replaced. They also wear out on account of photocurrent--the usual rule
    is that you can get an integrated anode charge of about 1000 C/cm**2 of photocathode area before the gain drops by ~half.

    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate)
    you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or something.

    Using an air gap between scintillator and tube allows you to keep the
    anode near ground, which is much more convenient, but costs you about
    half your light. (The collection efficiency goes like the etendue,
    which has a factor of n**2 in it.)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Mon Jun 27 22:01:42 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly
    in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and
    mail it to me? I can pay you via Paypal. Thanks.

    For any serious use, I'd budget for a replacement PMT. They age out
    after several years, which is probably why these assemblies were
    replaced. They also wear out on account of photocurrent--the usual rule
    is that you can get an integrated anode charge of about 1000 C/cm**2 of photocathode area before the gain drops by ~half.

    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate) you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or something.

    Using an air gap between scintillator and tube allows you to keep the
    anode near ground, which is much more convenient, but costs you about
    half your light. (The collection efficiency goes like the etendue,
    which has a factor of n**2 in it.)

    Cheers

    Phil Hobbs

    Good information. Thanks.

    I'm not planning on heavy use. The idea is to compare the scintillator
    againt the Radiacode, and try to measure any Radon gas in the basement.
    Then it will probably go into storage.



    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From Chris Jones@21:1/5 to Mike Monett on Tue Jun 28 13:31:26 2022
    On 28/06/2022 08:01, Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly >>>> in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and
    mail it to me? I can pay you via Paypal. Thanks.

    For any serious use, I'd budget for a replacement PMT. They age out
    after several years, which is probably why these assemblies were
    replaced. They also wear out on account of photocurrent--the usual rule
    is that you can get an integrated anode charge of about 1000 C/cm**2 of
    photocathode area before the gain drops by ~half.

    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate)
    you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or
    something.

    Using an air gap between scintillator and tube allows you to keep the
    anode near ground, which is much more convenient, but costs you about
    half your light. (The collection efficiency goes like the etendue,
    which has a factor of n**2 in it.)

    Cheers

    Phil Hobbs

    Good information. Thanks.

    I'm not planning on heavy use. The idea is to compare the scintillator
    againt the Radiacode, and try to measure any Radon gas in the basement.
    Then it will probably go into storage.


    If you have radon, try running a CRT television for a few hours and then
    wipe down the screen with a damp piece of tissue that has been folded to
    about the size of your geiger tube (or its end window if it has one). I
    find the dust on my CRT screen is quite radioactive but it has a short half-life. I'm guessing it is some polonium isotopes. The dust that
    collects on the screen doesn't end up in my lungs, so perhaps CRTs are healthier to have in the house than flatscreens.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Clifford Heath@21:1/5 to Chris Jones on Tue Jun 28 17:03:04 2022
    On 28/6/22 13:31, Chris Jones wrote:
    If you have radon, try running a CRT television for a few hours and then
    ... The dust that
    collects on the screen doesn't end up in my lungs, so perhaps CRTs are healthier to have in the house than flatscreens.

    Not as healthy as having no TV. That crap bypasses the lungs and goes
    straight to the brain

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to no_spam@please.net on Tue Jun 28 07:59:27 2022
    On a sunny day (Tue, 28 Jun 2022 17:03:04 +1000) it happened Clifford Heath <no_spam@please.net> wrote in <16fcb6d40dd74681$1$391142$70dd7a6b@news.thecubenet.com>:

    On 28/6/22 13:31, Chris Jones wrote:
    If you have radon, try running a CRT television for a few hours and then
    ... The dust that
    collects on the screen doesn't end up in my lungs, so perhaps CRTs are
    healthier to have in the house than flatscreens.

    Not as healthy as having no TV. That crap bypasses the lungs and goes >straight to the brain

    There are some informative science related programs on (sat) TV Astra1
    and there is (at least on the continent) tetelext / ceefax / videotext
    Caesar: give the people bread and TeeFee
    or was it games? :-)

    Its a shame UK dropped Ceefax. no way to see the program schedule other then internet, talk about a DANGEROUS medium ? Just read this group!

    Radon detectors and test kits are 14 USD upwards on Amazon...

    I was looking for a sold state PMT diode .. for that tomshardware link I gave, delivery November, about 56 Euro 1 piece

    I will hang on to my good old PMTs for now, have also many plastic scintillators.
    Big PMT will likely last to WW3 (2024??). After that all lights up in the dark anyways

    BTW I have a nice scintillation screen too.

    --- SoupGate-Win32 v1.05
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  • From Jan Panteltje@21:1/5 to lugnut808@spam.yahoo.com on Tue Jun 28 07:46:19 2022
    On a sunny day (Tue, 28 Jun 2022 13:31:26 +1000) it happened Chris Jones <lugnut808@spam.yahoo.com> wrote in <eCuuK.190184$pqD1.30751@fx01.ams4>:

    If you have radon, try running a CRT television for a few hours and then
    wipe down the screen with a damp piece of tissue that has been folded to >about the size of your geiger tube (or its end window if it has one). I
    find the dust on my CRT screen is quite radioactive but it has a short >half-life. I'm guessing it is some polonium isotopes. The dust that
    collects on the screen doesn't end up in my lungs, so perhaps CRTs are >healthier to have in the house than flatscreens.

    Some CRTs from sets that came in for repair had collected tar from smokers.. nicotine.
    Wiping clean with alcohol increased brightness considerably :-)
    So yes, functioned as air filter ;-)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Tue Jun 28 12:25:47 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 5, 2022 at 4:07:22 PM UTC-7, Mike Monett wrote:
    My Radiascan Radiacode finally arrived from Russia. After the
    sanctions, I was surprised to see it made it.

    This listing is also very interesting:

    https://www.ebay.com/itm/194659036410

    Basically 2000+ PMT+CsI(Tl) assemblies for sale at around $20 each.
    Wonder how they'd compare to the solid-state CsI(Tl) detector assembly >>>> in the Radiacode unit?

    -- john, KE5FX

    I tried to order one. Does not ship to Canada. Can you order one and
    mail it to me? I can pay you via Paypal. Thanks.

    For any serious use, I'd budget for a replacement PMT. They age out
    after several years, which is probably why these assemblies were
    replaced. They also wear out on account of photocurrent--the usual rule
    is that you can get an integrated anode charge of about 1000 C/cm**2 of
    photocathode area before the gain drops by ~half.

    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate)
    you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or
    something.

    Using an air gap between scintillator and tube allows you to keep the
    anode near ground, which is much more convenient, but costs you about
    half your light. (The collection efficiency goes like the etendue,
    which has a factor of n**2 in it.)


    Good information. Thanks.

    I'm not planning on heavy use. The idea is to compare the scintillator
    againt the Radiacode, and try to measure any Radon gas in the basement.
    Then it will probably go into storage.

    It ought to work fine for light-duty use like that, though you'll need
    the PMT supply and bias string. If you know the tube P/N, I can
    probably tell you what to use.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Tue Jun 28 18:19:32 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:

    [...]

    I'm not planning on heavy use. The idea is to compare the scintillator
    againt the Radiacode, and try to measure any Radon gas in the basement.
    Then it will probably go into storage.

    It ought to work fine for light-duty use like that, though you'll need
    the PMT supply and bias string. If you know the tube P/N, I can
    probably tell you what to use.

    Cheers

    Phil Hobbs

    I don't think the PMT P/N is available. I also assume the bias string is
    buried inside the assembly. I'll probably have to find the operating voltage
    by experimenting, a time-honored tradition among hackers.



    --
    MRM

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  • From Phil Hobbs@21:1/5 to Mike Monett on Wed Jun 29 10:25:37 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:

    [...]

    I'm not planning on heavy use. The idea is to compare the scintillator
    againt the Radiacode, and try to measure any Radon gas in the basement.
    Then it will probably go into storage.

    It ought to work fine for light-duty use like that, though you'll need
    the PMT supply and bias string. If you know the tube P/N, I can
    probably tell you what to use.

    Cheers

    Phil Hobbs

    I don't think the PMT P/N is available. I also assume the bias string is buried inside the assembly. I'll probably have to find the operating voltage by experimenting, a time-honored tradition among hackers.


    Turns out the p/n is (more or less) in the listing title: it's some
    flavour of R7400, whose datasheet is here, courtesy of Jeroen & Co: <https://ctf3-tbts.web.cern.ch/instr/PMT/R7400U_TPMH1204E07.pdf>.

    CsI(Tl) emits in the visible (the peak is around 550 nm), so the tube is probably an R7400-02 or -20.

    It's an 8-stage tube that likes about 75-100V per stage, and is
    interestingly fast at 800 ps FWHM. That's fast like an APD, and much
    faster than a SiPM/MPPC. I ordered a few of them to try out, probably
    without the scintillator.

    For scintillation counting, you don't need brilliant linearity, so a
    resistor string is probably fine for the dynode bias. I'd start with a current-limited -1 kV variable supply and some 1M resistors, with a
    2.2-nF cap across each of the bottom two or three resistors. That way,
    at 800V you'll be dissipating about 80 mW.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Wed Jun 29 16:32:06 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Turns out the p/n is (more or less) in the listing title: it's some
    flavour of R7400, whose datasheet is here, courtesy of Jeroen & Co: <https://ctf3-tbts.web.cern.ch/instr/PMT/R7400U_TPMH1204E07.pdf>.

    CsI(Tl) emits in the visible (the peak is around 550 nm), so the tube is probably an R7400-02 or -20.

    It's an 8-stage tube that likes about 75-100V per stage, and is
    interestingly fast at 800 ps FWHM. That's fast like an APD, and much
    faster than a SiPM/MPPC. I ordered a few of them to try out, probably without the scintillator.

    For scintillation counting, you don't need brilliant linearity, so a
    resistor string is probably fine for the dynode bias. I'd start with a current-limited -1 kV variable supply and some 1M resistors, with a
    2.2-nF cap across each of the bottom two or three resistors. That way,
    at 800V you'll be dissipating about 80 mW.

    Cheers

    Phil Hobbs

    Very valuable information. Thanks.



    --
    MRM

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  • From John Miles, KE5FX@21:1/5 to Mike Monett on Sat Jul 16 00:26:53 2022
    On Sunday, June 26, 2022 at 5:23:43 PM UTC-7, Mike Monett wrote:
    I will send my name and address to your gmail address. Again, thanks.

    Go ahead and send your address to me at john (at) miles.io if you'd
    still like one, and I'll throw one in a padded envelope next time I go to
    the post office. My GMail account is almost unusable due to people
    confusing their email address with mine and signing me up for
    all kinds of junk mail. Right now there are 217,959 unread messages
    and I don't see yours anywhere. :(

    I powered one up just now and took a video:

    http://www.ke5fx.com/r7400u.htm

    Hopefully I'm looking at a lot of dark counts or other PMT artifacts,
    because jeez, that sure seems like a lot of pulses.

    -- john, KE5FX

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  • From Mike Monett@21:1/5 to jmiles@gmail.com on Sat Jul 16 10:24:59 2022
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Sunday, June 26, 2022 at 5:23:43 PM UTC-7, Mike Monett wrote:
    I will send my name and address to your gmail address. Again, thanks.

    Go ahead and send your address to me at john (at) miles.io if you'd
    still like one, and I'll throw one in a padded envelope next time I go to
    the post office. My GMail account is almost unusable due to people
    confusing their email address with mine and signing me up for
    all kinds of junk mail. Right now there are 217,959 unread messages
    and I don't see yours anywhere. :(

    I powered one up just now and took a video:

    http://www.ke5fx.com/r7400u.htm

    Hopefully I'm looking at a lot of dark counts or other PMT artifacts,
    because jeez, that sure seems like a lot of pulses.

    -- john, KE5FX

    Hi John,

    Very nice page !

    That is a very nice offer. Thanks.

    Various sources say the PMT voltage is critical and must be adjusted individually for each PMT. One way to do this is to find a known
    radioactive source and generate a spectrum, then adjust the PMT voltage so
    the source lines up with the known energies in KeV or Mev.

    Getting samples of thorium has turned out to be impossible, except for
    traces in welding rods. However, radium is readily available in the form of watch hands painted with radium. These are for sale extremely cheap on
    Ebay.

    The watch hands no longer glow in the dark since the phosphor will have
    worn out. However, the radium will still be active since it has a half-life
    of 1600 years. Below is the radioactive series of radium-226. You can see
    the first step is radon, which releases alpha particles and gamma
    radiation:

    https://www.ld-
    didactic.de/software/524221en/Content/Appendix/Ra226Series.htm

    Radon gas is extremely dangerous. There is a small amount in every
    basement. You breath it into your lungs, where it emits alpha particles,
    which are the nucleus of helium-4. This causes lung cancer and you die.

    We need to be able to monitor the amount of radon in our basements and be certain it doesn't increase, such as during the winter when most
    ventilation is shut off.

    So it pays to learn a bit about gamma spectrometers to be able to protect yourself and your family.

    Regular radon detectors are very expensive, but gamma spectrometers can be quite modest in cost. You can get the Radiacode, which is a very nice unit,
    or build the Hamamatsu R7400U PMT version as a backup and verification.



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to Mike Monett on Sat Jul 16 05:38:39 2022
    On Saturday, July 16, 2022 at 8:25:08 PM UTC+10, Mike Monett wrote:
    "John Miles, KE5FX" <jmi...@gmail.com> wrote:
    On Sunday, June 26, 2022 at 5:23:43 PM UTC-7, Mike Monett wrote:
    I will send my name and address to your gmail address. Again, thanks.

    Go ahead and send your address to me at john (at) miles.io if you'd
    still like one, and I'll throw one in a padded envelope next time I go to the post office. My GMail account is almost unusable due to people confusing their email address with mine and signing me up for
    all kinds of junk mail. Right now there are 217,959 unread messages
    and I don't see yours anywhere. :(

    I powered one up just now and took a video:

    http://www.ke5fx.com/r7400u.htm

    Hopefully I'm looking at a lot of dark counts or other PMT artifacts, because jeez, that sure seems like a lot of pulses.

    Very nice page !

    That is a very nice offer. Thanks.

    Various sources say the PMT voltage is critical and must be adjusted individually for each PMT. One way to do this is to find a known
    radioactive source and generate a spectrum, then adjust the PMT voltage so the source lines up with the known energies in KeV or Mev.

    The photomultiplier voltage just adjusts the gain of the photomultiplier tube - photons hitting the photocathode produce electrons in the cathode space, and the voltage drop across the dynode chain just adjusts the number of electrons that each electron
    hitting the first dynode ends up delivering to the anode.

    Getting the energy of individual particles coming out of the radiation source takes rather more than fiddling with the gain of the electron multiplication stages inside the photomultiplier tube. Because you've got a lot of stages of multiplication -
    anything from 10 to 14 - you can vary that gain a lot.

    Getting samples of thorium has turned out to be impossible, except for traces in welding rods. However, radium is readily available in the form of watch hands painted with radium. These are for sale extremely cheap on
    Ebay.

    The watch hands no longer glow in the dark since the phosphor will have
    worn out. However, the radium will still be active since it has a half-life of 1600 years. Below is the radioactive series of radium-226. You can see the first step is radon, which releases alpha particles and gamma
    radiation:

    https://www.ld- didactic.de/software/524221en/Content/Appendix/Ra226Series.htm

    Radon gas is extremely dangerous. There is a small amount in every
    basement.

    If your house is built above granite rocks, or any other kind of rock that contains uranium, you can get radon gas leaking into the basement. If it is, put in an extractor fan to move it out before it can drift up to diffuse through the floor into the
    rest of the house.

    You breath it into your lungs, where it emits alpha particles, which are the nucleus of helium-4. This causes lung cancer and you die.

    Helium four won't do any damage at all, but energetic alpha particles can cause mutations in any cell that they hit, and some mutations can make cell cancerous

    We need to be able to monitor the amount of radon in our basements and be certain it doesn't increase, such as during the winter when most
    ventilation is shut off.

    If there's uranium - or the like - in the rocks under your basement it makes sense to monitor for radon. If there is, it makes sense to ventilate that space, even in winter.

    So it pays to learn a bit about gamma spectrometers to be able to protect yourself and your family.

    Learning about geology is cheaper.

    Regular radon detectors are very expensive, but gamma spectrometers can be quite modest in cost. You can get the Radiacode, which is a very nice unit, or build the Hamamatsu R7400U PMT version as a backup and verification.

    Radon itself decays by emitting a 4.6 Mev alpha particle. This isn't any kind of gamma ray, but it is energetic enough that if it hits an adjacent atom it may generate a gamma ray (an energetic photon) which is likely to have a longer range.

    The Radiacode 101 monitor uses a scintillation detector - the chunk of thallium doped cesium iodide - which produces a flash of light when hit by a gamma ray photon (or anything else that can get at it).

    > crystal CsI (Tl) of cesium iodide doped with thallium in a sealed container;
    > silicon photomultiplier;

    Also called an avalanche photodiode.

    > optical interface between scintillator and photomultiplier;

    A window, so the photons emerging from the transparent can get at the sensitive face of the photodiode

    > precision temperature-compensated power supply for photomultiplier;

    Avalanche photodiodes are tricky to bias.

    > high-speed analog-digital circuit for processing pulses from a photomultiplier.

    The pulses do tend to be narrow. You need fast op amps and comparators, but they are widely available and not that expensive.

    https://ctf3-tbts.web.cern.ch/instr/pmt/r7400u_tpmh1204e07.pdf

    The minature Hamamatsu R7400U photomultiplier tubes are pretty compact (but not as compacts as an avalanche photodode) and need a higher voltage supply, but they aren't quite as tricky to bias as an avalanche photodiode.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dave Platt@21:1/5 to spamme@not.com on Sat Jul 16 07:14:52 2022
    In article <XnsAED63FC6A8982idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:
    Getting samples of thorium has turned out to be impossible, except for
    traces in welding rods. However, radium is readily available in the form of >watch hands painted with radium. These are for sale extremely cheap on
    Ebay.

    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.

    They do generate "negative ions", in the form of beta-decay
    electrons... these are not your gentle after-the-rainstorm negative
    ions by any means!

    By one report the radiation level is high enough that wearing one next
    to the skin for a year can exceed safe exposure levels and might even
    cause a mild radiation burn. I understand that Singapore has banned
    the import of such products for this reason.

    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    Another useful calibration source (for higher-energy gammas from
    potassium-40) is a sack of potassium chloride water-softener recharge
    crystals from your local big-box home/hardware store (or, on a smaller
    scale, a box of Morton "Lite Salt" which is about half potassium
    chloride).

    And, one can still find orange Fiestaware and green uranium glass at
    the occasional estate or garage sale or antique store.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to Dave Platt on Sat Jul 16 09:55:46 2022
    On Saturday, 16 July 2022 at 16:16:38 UTC+2, Dave Platt wrote:
    In article <XnsAED63FC6A8...@88.198.57.247>,
    Mike Monett <spa...@not.com> wrote:
    Getting samples of thorium has turned out to be impossible, except for >traces in welding rods. However, radium is readily available in the form of >watch hands painted with radium. These are for sale extremely cheap on >Ebay.
    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.

    They do generate "negative ions", in the form of beta-decay
    electrons... these are not your gentle after-the-rainstorm negative
    ions by any means!

    By one report the radiation level is high enough that wearing one next
    to the skin for a year can exceed safe exposure levels and might even
    cause a mild radiation burn. I understand that Singapore has banned
    the import of such products for this reason.

    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    Another useful calibration source (for higher-energy gammas from potassium-40) is a sack of potassium chloride water-softener recharge crystals from your local big-box home/hardware store (or, on a smaller
    scale, a box of Morton "Lite Salt" which is about half potassium
    chloride).

    And, one can still find orange Fiestaware and green uranium glass at
    the occasional estate or garage sale or antique store.
    -Low Level Gamma Radiation is all fake

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Miles, KE5FX@21:1/5 to Dave Platt on Sat Jul 16 11:43:24 2022
    On Saturday, July 16, 2022 at 7:16:38 AM UTC-7, Dave Platt wrote:
    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.pn

    Resolution of that setup looks really good -- is it written up anywhere?

    -- john, KE5FX

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sjouke Burry@21:1/5 to All on Sat Jul 16 20:52:27 2022
    On 16.07.22 20:43, John Miles, KE5FX wrote:
    On Saturday, July 16, 2022 at 7:16:38 AM UTC-7, Dave Platt wrote:
    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.pn

    Resolution of that setup looks really good -- is it written up anywhere?

    -- john, KE5FX

    why did somebody snip off the last letter of .PNG????

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Dave Platt on Sat Jul 16 18:48:41 2022
    dplatt@coop.radagast.org (Dave Platt) wrote:

    In article <XnsAED63FC6A8982idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:
    Getting samples of thorium has turned out to be impossible, except for >>traces in welding rods. However, radium is readily available in the form
    of watch hands painted with radium. These are for sale extremely cheap
    on Ebay.

    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.

    They do generate "negative ions", in the form of beta-decay
    electrons... these are not your gentle after-the-rainstorm negative
    ions by any means!

    By one report the radiation level is high enough that wearing one next
    to the skin for a year can exceed safe exposure levels and might even
    cause a mild radiation burn. I understand that Singapore has banned
    the import of such products for this reason.

    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    Another useful calibration source (for higher-energy gammas from potassium-40) is a sack of potassium chloride water-softener recharge crystals from your local big-box home/hardware store (or, on a smaller
    scale, a box of Morton "Lite Salt" which is about half potassium
    chloride).

    And, one can still find orange Fiestaware and green uranium glass at
    the occasional estate or garage sale or antique store.

    Thanks for the information. I will try to find the black volcanic rock products. I recall an article describing these that got them kicked off
    Amazon (I think).

    Your gamma spectrometry system sounds very interesting. Can you supply more information, such as what kind of scintillator crystal do you use, how big
    is it, and do you use a PMT or diode for the detector, what software do you
    use to generate the spectrum, how do you drive it, and any other details
    that might be interesting.

    I use pure potassium chloride (KCl) in the form of Windsor Salt Free
    seasoning, but my Radiacode is not sensitive enough to detect the decay products. I left it sitting on three containers for several days but had no luck. I need a more sensitive detector, which is why yours is so
    interesting.

    On a related topic, I have been trying to find out why the background gamma spectrum has a sharp rise at low energies, and where does it come from? Do
    you have any ideas?

    Thanks,

    Mike



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Mike Monett on Sat Jul 16 19:25:08 2022
    Mike Monett <spamme@not.com> wrote:

    dplatt@coop.radagast.org (Dave Platt) wrote:

    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.

    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    Thanks for the information. I will try to find the black volcanic rock products. I recall an article describing these that got them kicked off Amazon (I think).

    Thanks,

    Mike

    Ebay was a bust. Quantum Energy turned out to be a fishing reel. Scalar
    energy was some patterns on a piece of paper.

    However, Amazon turned up lots of volcanic rock emi protectors. I got one titled

    "Volcanic Stone Pendant,Energy Necklace Fashionable Health Care for Women
    for Daily Wear Quantum Science Scalar Energy Necklace Round Pendant for Men Woman Tourmaline Volcanic Stone Jewelry",

    $15.86 FREE delivery August 22 - September 16

    https://www.amazon.ca/gp/product/B09V9Y7359/

    This one sounds like it will do the job. Thanks.

    Mike


    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to Mike Monett on Sat Jul 16 13:55:26 2022
    On Saturday, 16 July 2022 at 21:25:19 UTC+2, Mike Monett wrote:
    Mike Monett <spa...@not.com> wrote:
    dpl...@coop.radagast.org (Dave Platt) wrote:

    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.
    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png
    Thanks for the information. I will try to find the black volcanic rock products. I recall an article describing these that got them kicked off Amazon (I think).
    Thanks,

    Mike

    Ebay was a bust. Quantum Energy turned out to be a fishing reel. Scalar energy was some patterns on a piece of paper.

    However, Amazon turned up lots of volcanic rock emi protectors. I got one titled

    "Volcanic Stone Pendant,Energy Necklace Fashionable Health Care for Women
    for Daily Wear Quantum Science Scalar Energy Necklace Round Pendant for Men Woman Tourmaline Volcanic Stone Jewelry",

    $15.86 FREE delivery August 22 - September 16

    https://www.amazon.ca/gp/product/B09V9Y7359/

    This one sounds like it will do the job. Thanks.

    Mike


    --
    MRM
    Gamma Radiation is never Low Level
    beware of cancer

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dave Platt@21:1/5 to jmiles@gmail.com on Sat Jul 16 17:22:04 2022
    In article <7cc8f810-1325-4542-bda7-63c76d4195a0n@googlegroups.com>,
    John Miles, KE5FX <jmiles@gmail.com> wrote:
    On Saturday, July 16, 2022 at 7:16:38 AM UTC-7, Dave Platt wrote:
    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.pn

    Resolution of that setup looks really good -- is it written up anywhere?

    I don't think I've written up anything in detail - it's been a few
    years since I played with it much.

    I have a couple of probes, both built with surplus commercial PMTs,
    one with a NaI(Tl) crystal and another with a BGO crystal.

    The signal processing uses a charge-sensitive amplifier with some
    pulse shaping built in (I like the CSA architecture because it's not particularly sensitive to the cable length and capacitance). The
    original design was done by Richard Hester; I did some tweaks for my
    version and did a custom board layout. The files are in the https://www.radagast.org/~dplatt/gamma/ directory.

    The biggest disadvantage to this circuit is that if I forget, and
    connect or disconnect the probe cable with the power on (or without
    letting it discharge to zero) the spike usually blows out the
    front-end JFET, and I have to cuss and pull it out of the
    air-wire socket and replace it :-)

    The high-voltage supply is based on a flyback with diode voltage
    multiplier, based on a circuit I found some years ago intended for
    use with GM tubes.

    The output of the CSA goes into a moderately-priced USB sound card
    line input.

    I wrote the pulse detection and filtering code myself. The first
    version was strictly command-line (record audio to a .WAV file, then post-process to detect and bin the pulses and generate data files which
    could be fed to gnuplot). I then wrote a Linux GUI based on the FLTK
    toolkit which can read/process/display in real time.

    The trickiest part was handling high pulse rates, where one pulse
    starts while the CSA is still recovering from the previous one.
    At some point I may sit down and try writing some DSP code to
    de-convolve the CSA's pulse shaping and turn the signal back
    into narrow impulses.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dave Platt@21:1/5 to spamme@not.com on Sat Jul 16 17:36:04 2022
    In article <XnsAED696ABEA7D1idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:

    On a related topic, I have been trying to find out why the background gamma >spectrum has a sharp rise at low energies, and where does it come from? Do >you have any ideas?

    As I understand it, you're seeing is largely Compton radiation and
    X-ray fluorescence. When naturally occurring gammas (from K40 decay, transuranincs, and cosmic rays) smack into atmosphere or into solid
    matter, the energy of the gamma is scattered... it's dissipated a bit
    at a time as the gamma photon interacts with electrons or the nucleus
    of the impacted materials.

    If a gamma scatters off of an electron, some of the energy is
    transferred to the electron. If the electron is bumped up to a
    higher-energy orbital and then decays back to its ground state, the
    decay can cause the emission of an X-ray photon - fluorescence. This necessarily has a lower energy than the gamma, and its energy will
    depend on just what element was involved in the scattering. The
    original scattered gamma will have less energy than it did before, of
    course.

    So, the rise you see in the spectrum is probably the sum of a whole
    bunch of Compton scattering events which involved gammas that were
    originally of higher energy.

    From what I've read, skyglow (gammas and X-rays originating from
    cosmic-ray impacts on the atmosphere) is a big part of this.
    NORM is another big part.

    A few years ago I collected a box of monazite sand from a local
    beach. It definitely shows a thorium signature, but the peaks are
    nowhere near as sharp as the ones in the "quantum pendant" data.
    I believe this is because the thorium is diffused throughout a
    much larger amount of base material (I have to use a couple of
    pounds of it to get a good reading) and most of the decay gammas
    end up Compton-scattering at least once as they work their way
    through the sand to the sensor crystal. As a result, the
    sharp peaks from the original decay events are weakened, and
    blurred by the Compton scattering effect.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Sat Jul 16 17:24:41 2022
    On Sat, 16 Jul 2022 18:48:41 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    dplatt@coop.radagast.org (Dave Platt) wrote:

    In article <XnsAED63FC6A8982idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:
    Getting samples of thorium has turned out to be impossible, except for >>>traces in welding rods. However, radium is readily available in the form >>>of watch hands painted with radium. These are for sale extremely cheap
    on Ebay.

    Also on eBay, you can find "quantum energy" or "scalar energy" or
    "negative ion" pendants made out of a black volcanic rock. They're
    often touted as a way of protecting oneself from the (supposed)
    harmful effects of electromagnetic radiation.

    They do generate "negative ions", in the form of beta-decay
    electrons... these are not your gentle after-the-rainstorm negative
    ions by any means!

    By one report the radiation level is high enough that wearing one next
    to the skin for a year can exceed safe exposure levels and might even
    cause a mild radiation burn. I understand that Singapore has banned
    the import of such products for this reason.

    The rock from which they are made appears to be rich in thorium and
    its decay products (perhaps something like monazite?).

    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.png

    Another useful calibration source (for higher-energy gammas from
    potassium-40) is a sack of potassium chloride water-softener recharge
    crystals from your local big-box home/hardware store (or, on a smaller
    scale, a box of Morton "Lite Salt" which is about half potassium
    chloride).

    And, one can still find orange Fiestaware and green uranium glass at
    the occasional estate or garage sale or antique store.

    Thanks for the information. I will try to find the black volcanic rock >products. I recall an article describing these that got them kicked off >Amazon (I think).

    Your gamma spectrometry system sounds very interesting. Can you supply more >information, such as what kind of scintillator crystal do you use, how big
    is it, and do you use a PMT or diode for the detector, what software do you >use to generate the spectrum, how do you drive it, and any other details
    that might be interesting.

    I use pure potassium chloride (KCl) in the form of Windsor Salt Free >seasoning, but my Radiacode is not sensitive enough to detect the decay >products. I left it sitting on three containers for several days but had no >luck. I need a more sensitive detector, which is why yours is so
    interesting.

    On a related topic, I have been trying to find out why the background gamma >spectrum has a sharp rise at low energies, and where does it come from? Do >you have any ideas?

    Thanks,

    Mike

    The classic radiation test source was a thoriated Coleman lantern
    mantle.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Dave Platt on Sun Jul 17 09:26:12 2022
    dplatt@coop.radagast.org (Dave Platt) wrote:

    In article <7cc8f810-1325-4542-bda7-63c76d4195a0n@googlegroups.com>,
    John Miles, KE5FX <jmiles@gmail.com> wrote:
    On Saturday, July 16, 2022 at 7:16:38 AM UTC-7, Dave Platt wrote:
    I measured one on my home-made gamma spectrometry system and got
    a very recognizable thorium-decay signature (the isotope markers
    are from a best-efforts calibration).

    https://www.radagast.org/~dplatt/gamma/quantum-pendant.pn

    Resolution of that setup looks really good -- is it written up anywhere?

    I don't think I've written up anything in detail - it's been a few
    years since I played with it much.

    I have a couple of probes, both built with surplus commercial PMTs,
    one with a NaI(Tl) crystal and another with a BGO crystal.

    How big are the crystals?



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to Dave Platt on Sun Jul 17 02:33:22 2022
    On Saturday, July 16, 2022 at 5:38:44 PM UTC-7, Dave Platt wrote:

    The trickiest part was handling high pulse rates, where one pulse
    starts while the CSA is still recovering from the previous one.
    At some point I may sit down and try writing some DSP code to
    de-convolve the CSA's pulse shaping and turn the signal back
    into narrow impulses.

    The analog-days solution was a delay line amplifier; the long recovery tail
    is exponential, so a difference amplification of V(t) - (1+epsilon)V(t-s) flattens the recovery when (1+epsilon) equals the diminution of the signal during 's' seconds. The infinite-impulse response or FIR filter is relatively easy
    work to do that.

    Some good info here: <https://www.ortec-online.com/-/media/ametekortec/manuals/4/460-mnl.pdf>

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to All on Sun Jul 17 10:17:32 2022
    Thanks to Phil and John, I will soon have a PMT gamma detector to compare
    with the Radiacode. Hopefully, it will be more sensitive so I can be more certain of measuring Radon in the basement as well as other radiation
    sources.

    Assembling the electronics turned out to be much easier than some DIY pages describe on the web. There is a company in Israel that supplies complete
    Gamma Spectroscopy electronics. The company is RH-Electronics at

    http://rhelectronics.net

    I got the PIC18 MCA Module for $95.00 plus shipping at $17.95:

    https://www.rhelectronics.store/diy-pic18-mca-kit-for-gamma-spectroscopy

    Generating the high voltage for the PMT turned out to be easy. Amazon sells CCFL inverter boards very cheap. I got one for $13.46 at

    https://www.amazon.ca/gp/product/B07YM68GVM/

    The last item is a fast high voltage diode to supply the PMT. This turned
    out to be the hardest problem until I found Dean Technology in Dallas,
    Texas, 75370

    They sell a 5KV 100ns diode for a couple of bucks:

    https://www.deantechnology.com/products/hl500

    The total price is CDN $95.00 + $17.95 + $13.46 + $2.50 = $128.91, not including the PMT that the seller refuses to sell to Canada.

    The US price is about $120 USD including the PMT, so nobody has any excuse
    for not being able to detect radon in their basement.





    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Dave Platt on Sun Jul 17 18:01:45 2022
    dplatt@coop.radagast.org (Dave Platt) wrote:

    In article <XnsAED696ABEA7D1idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:

    On a related topic, I have been trying to find out why the background
    gamma spectrum has a sharp rise at low energies, and where does it come >>from? Do you have any ideas?

    As I understand it, you're seeing is largely Compton radiation and
    X-ray fluorescence. When naturally occurring gammas (from K40 decay, transuranincs, and cosmic rays) smack into atmosphere or into solid
    matter, the energy of the gamma is scattered... it's dissipated a bit
    at a time as the gamma photon interacts with electrons or the nucleus
    of the impacted materials.

    If a gamma scatters off of an electron, some of the energy is
    transferred to the electron. If the electron is bumped up to a
    higher-energy orbital and then decays back to its ground state, the
    decay can cause the emission of an X-ray photon - fluorescence. This necessarily has a lower energy than the gamma, and its energy will
    depend on just what element was involved in the scattering. The
    original scattered gamma will have less energy than it did before, of
    course.

    So, the rise you see in the spectrum is probably the sum of a whole
    bunch of Compton scattering events which involved gammas that were
    originally of higher energy.

    From what I've read, skyglow (gammas and X-rays originating from
    cosmic-ray impacts on the atmosphere) is a big part of this.
    NORM is another big part.

    A few years ago I collected a box of monazite sand from a local
    beach. It definitely shows a thorium signature, but the peaks are
    nowhere near as sharp as the ones in the "quantum pendant" data.
    I believe this is because the thorium is diffused throughout a
    much larger amount of base material (I have to use a couple of
    pounds of it to get a good reading) and most of the decay gammas
    end up Compton-scattering at least once as they work their way
    through the sand to the sensor crystal. As a result, the
    sharp peaks from the original decay events are weakened, and
    blurred by the Compton scattering effect.

    A very lucid explanation. Thanks.

    I was able to find out what NORM is without having to ask you: "Naturally ocurring radioactive materials." I'm so proud of myself:)

    How big are your scintillator crystals?



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to Mike Monett on Sun Jul 17 12:59:57 2022
    On Sunday, 17 July 2022 at 20:01:52 UTC+2, Mike Monett wrote:
    dpl...@coop.radagast.org (Dave Platt) wrote:

    In article <XnsAED696ABEA...@88.198.57.247>,
    Mike Monett <spa...@not.com> wrote:

    On a related topic, I have been trying to find out why the background >>gamma spectrum has a sharp rise at low energies, and where does it come >>from? Do you have any ideas?

    As I understand it, you're seeing is largely Compton radiation and
    X-ray fluorescence. When naturally occurring gammas (from K40 decay, transuranincs, and cosmic rays) smack into atmosphere or into solid
    matter, the energy of the gamma is scattered... it's dissipated a bit
    at a time as the gamma photon interacts with electrons or the nucleus
    of the impacted materials.

    If a gamma scatters off of an electron, some of the energy is
    transferred to the electron. If the electron is bumped up to a higher-energy orbital and then decays back to its ground state, the
    decay can cause the emission of an X-ray photon - fluorescence. This necessarily has a lower energy than the gamma, and its energy will
    depend on just what element was involved in the scattering. The
    original scattered gamma will have less energy than it did before, of course.

    So, the rise you see in the spectrum is probably the sum of a whole
    bunch of Compton scattering events which involved gammas that were originally of higher energy.

    From what I've read, skyglow (gammas and X-rays originating from
    cosmic-ray impacts on the atmosphere) is a big part of this.
    NORM is another big part.

    A few years ago I collected a box of monazite sand from a local
    beach. It definitely shows a thorium signature, but the peaks are
    nowhere near as sharp as the ones in the "quantum pendant" data.
    I believe this is because the thorium is diffused throughout a
    much larger amount of base material (I have to use a couple of
    pounds of it to get a good reading) and most of the decay gammas
    end up Compton-scattering at least once as they work their way
    through the sand to the sensor crystal. As a result, the
    sharp peaks from the original decay events are weakened, and
    blurred by the Compton scattering effect.
    A very lucid explanation. Thanks.

    I was able to find out what NORM is without having to ask you: "Naturally ocurring radioactive materials." I'm so proud of myself:)

    How big are your scintillator crystals?



    --
    MRM
    Gamma Radiation is never Low Level
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation
    so
    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to a a on Sun Jul 17 15:34:02 2022
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs
    and gamma radiation includes energies that go right through a human
    body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to All on Sun Jul 17 16:00:04 2022
    On Monday, 18 July 2022 at 00:34:05 UTC+2, whit3rd wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level
    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation
    Not at all; for human health, what matters is the generation of ion pairs and gamma radiation includes energies that go right through a human
    body without much likelihood of interaction.
    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation
    That's just nonsense; word salad, plus some capitalizations.
    you are exactly stupid dog

    --
    Gamma Radiation Sterilization: What You Need to Know https://int-enviroguard.com/blog/what-is-the-gamma...

    Gamma Radiation Sterilization ExplainedAdvantages of Gamma Radiation SterilizationDisadvantages of Gamma Radiation Sterilization

    Image
    As the name implies, this is a sterilization process, and it's commonly used to kill bacteria and microorganisms that may be living on the surface of products, packaging, or goods. Powered by Cobalt-60, the low-dose process is administered when high-
    energy photons are emitted from a radiation source, which works to io…

    ---
    Gamma Radiation - an overview | ScienceDirect Topics https://www.sciencedirect.com/.../gamma-radiation

    Gamma rays are a form of electromagnetic radiation, whereby gamma radiation kills microorganisms by destroying cellular nucleic acid [1]. The use of gamma irradiation is relatively widespread and was first described in the British Pharmacopeia in 1963
    and in the


    ---

    What are gamma rays and how dangerous are they?
    Gamma rays are ionizing radiation and are thus biologically hazardous. Due to their high penetration power, they can damage bone marrow and internal organs. Unlike alpha and beta rays, they pass easily through the body and thus pose a formidable
    radiation protection challenge.


    ---

    Gamma Radiation: A brief background Gamma particles consist of energy photons and were discovered by Paul Villard in 1900 when he was researching gamma radiation that comes from radium. These particles are a form of ionizing radiation and can be
    dangerous to humans, animals and plant life.
  • From Mike Monett@21:1/5 to whit3rd@gmail.com on Mon Jul 18 02:12:05 2022
    whit3rd <whit3rd@gmail.com> wrote:

    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs
    and gamma radiation includes energies that go right through a human
    body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.

    Ignore him. I PLONKED him long ago as soon as he appeared.




    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to Mike Monett on Mon Jul 18 03:10:19 2022
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs and gamma radiation includes energies that go right through a human
    body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.
    Ignore him. I PLONKED him long ago as soon as he appeared.




    --
    MRM
    Gamma Radiation

    Gamma radiation (7.5Gy) resulted in a significant decrease in body weight, tissue weight, testis: body weight ratio (the gonadosomatic index (GSI)) and tubular diameter up to 15 days of irradiation.

    https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/gamma-radiation

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to a a on Mon Jul 18 03:29:54 2022
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs and gamma radiation includes energies that go right through a human
    body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.
    Ignore him. I PLONKED him long ago as soon as he appeared.

    Gamma Radiation

    Gamma radiation (7.5Gy) resulted in a significant decrease in body weight, tissue weight, testis: body weight ratio (the gonadosomatic index (GSI)) and tubular diameter up to 15 days of irradiation.

    https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/gamma-radiation

    A a really doesn't know what he is talking about.

    https://en.wikipedia.org/wiki/Rad_(unit)

    The Gy - or Gray - is defined in terms of the energy absorbed - in Joules per kilogram - by the object being irradiated. Gamma rays - higher energy X-rays - go straight through human flesh, so the amount of energy deposited is a bit uncertain.

    What is certain is that it is the energy deposited that matters. and a a doesn't seem to know enough to understand this.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to bill....@ieee.org on Mon Jul 18 04:40:15 2022
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs
    and gamma radiation includes energies that go right through a human body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.
    Ignore him. I PLONKED him long ago as soon as he appeared.

    Gamma Radiation

    Gamma radiation (7.5Gy) resulted in a significant decrease in body weight, tissue weight, testis: body weight ratio (the gonadosomatic index (GSI)) and tubular diameter up to 15 days of irradiation.

    https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/gamma-radiation
    A a really doesn't know what he is talking about.

    https://en.wikipedia.org/wiki/Rad_(unit)

    The Gy - or Gray - is defined in terms of the energy absorbed - in Joules per kilogram - by the object being irradiated. Gamma rays - higher energy X-rays - go straight through human flesh, so the amount of energy deposited is a bit uncertain.

    What is certain is that it is the energy deposited that matters. and a a doesn't seem to know enough to understand this.

    --
    Bill Sloman, Sydney
    @BillSydneyLowScience
    stop fooling us


    IEEE NSW Section’s Committee Members (2021)

    Section Section Chair Colin Elston
    Section Vice Chair Sudipta Chakraborty
    Section Past Chair Sasha Nikolic
    Section Treasury Bill Sloman
    Section Assistant Treasurer
    Section Secretary Dushmantha Thalakotuna
    Section Assistant Secretary sherry.moghadassi
    Section Nominations Mahmoud Elkhodr
    Section eNotice Coordinator sanjib.choudhury
    Section Government Liaison & Industry Relations
    Section Webmaster Syed Muzahir Abbas
    Section Professional Activities Colin Elston
    Section Young Professional Chair Hijab Zahra
    Section Young Professional Vice Chair Naila Mukhtar
    Section Student Activities Chair Arslan Kiyani
    Section Student Activities Vice Chair
    Section Student Representative Luke Wicent Sy,
    Section NSW Section Mentor Chair Mohamad Awdallah
    Section Educational Activities & TISP Graeme B Gwilliam
    Section Membership Development Bruce Poon
    Section WIE Chair Naila Mukhtar
    Section WIE Vice Chair Helen Lu
    Section Awards and Recognition Committee Chair Antony Zaglas
    Section Conference Coordinator David Tien
    Section Historian Ramutis Zakarevicius
    Section Distribution Lists Dushmantha Thalakotuna
    Section Social Implications of Tech NSW Kayleen Manwaring Section Fellows Activties Coordinator Karu Esselle
    Section Circuit Editor Bill Sloman


    Welcome to the IEEE NSW Section (REGION 10)

    The IEEE New South Wales (NSW) Section provides local activities and services to IEEE members who live, work and visit us in New South Wales, Australia. The NSW Section is member of the IEEE Australia Council and is located within the Asia-Pacific region
    of the IEEE, known as Region 10. The NSW Section has in excess of 3,000 members (Feb-19) that work together to advance technology for the benefit of humanity. This is done through a variety of local student branches, technical chapters and groups. IEEE
    NSW is the oldest Section in Australia.

    If you reside in NSW you automatically become a member of the NSW Section. One to two emails are sent to members each month outlining all the upcoming events and latest news. To receive this information you must have selected in your IEEE account
    settings the option to receive local communication.

    The NSW Section Committee meets at 7.00pm on the first Monday of every month. Members looking to provide input or looking to volunteer are invited to attend and engage at the committee meeting. Being a volunteer unlocks access to a worldwide network. We
    are always looking for members that are looking to give back.


    About
    IEEE is the trusted voice for engineering, computing, and technology information around the globe

    So IEEE is not science body, organization at all

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Walliker@21:1/5 to bill....@ieee.org on Mon Jul 18 05:22:21 2022
    On Monday, 18 July 2022 at 11:29:57 UTC+1, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:

    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    Gamma Radiation is never Low Level

    False, of course.
    since
    what matters is
    long-term exposure to cancerogenic Gamma Radiation

    Not at all; for human health, what matters is the generation of ion pairs
    and gamma radiation includes energies that go right through a human body without much likelihood of interaction.

    Long-term Low Level exposure
    turns into
    High Level Gamma Radiation

    That's just nonsense; word salad, plus some capitalizations.
    Ignore him. I PLONKED him long ago as soon as he appeared.

    Gamma Radiation

    Gamma radiation (7.5Gy) resulted in a significant decrease in body weight, tissue weight, testis: body weight ratio (the gonadosomatic index (GSI)) and tubular diameter up to 15 days of irradiation.

    https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/gamma-radiation
    A a really doesn't know what he is talking about.

    https://en.wikipedia.org/wiki/Rad_(unit)

    The Gy - or Gray - is defined in terms of the energy absorbed - in Joules per kilogram - by the object being irradiated. Gamma rays - higher energy X-rays - go straight through human flesh, so the amount of energy deposited is a bit uncertain.

    What is certain is that it is the energy deposited that matters. and a a doesn't seem to know enough to understand this.

    A simple way of checking whether it is even worth worrying about radon is to look it up!

    https://www.ukradon.org/radonmaps/

    https://www.epa.gov/sites/default/files/2015-07/documents/zonemapcolor.pdf

    https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/radon-map

    There are similar maps for lots of other countries.

    John

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to a a on Mon Jul 18 05:36:31 2022
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    <snip>

    So IEEE is not science body, organization at all.

    If a a knew what he was talking about, he'd know that the main function of the IEEE is to publish a large collection of high-impact peer-reviewed scientific journals that deal with the science that underlies electronics. That is what science is about,
    even if a a doesn't have a clue about it.

    That's why I joined the organisation back around 1980. It's not all that obvious the current activities of the NSW Branch, but that's where the serious effort goes , and where the serious money gets spent.

    I've got just one short comment in that literature

    Sloman, A.W. "Comment on 'Computer aided simulation study of photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38 679-680 (1991).

    Because I mostly worked in the UK I published more the UK Institute of Physics journals, but there aren't as many of them, and Americans do tend to ignore them.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to bill....@ieee.org on Mon Jul 18 05:58:37 2022
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:
    <snip>

    So IEEE is not science body, organization at all.

    If a a knew what he was talking about, he'd know that the main function of the IEEE is to publish a large collection of high-impact peer-reviewed scientific journals that deal with the science that underlies electronics. That is what science is about,
    even if a a doesn't have a clue about it.

    That's why I joined the organisation back around 1980. It's not all that obvious the current activities of the NSW Branch, but that's where the serious effort goes , and where the serious money gets spent.

    I've got just one short comment in that literature

    Sloman, A.W. "Comment on 'Computer aided simulation study of photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38 679-680 (1991).

    Because I mostly worked in the UK I published more the UK Institute of Physics journals, but there aren't as many of them, and Americans do tend to ignore them.

    --
    Bill Sloman, Sydney
    ok, ok, stop your delusiones and day dreaming

    IEEE lives on Facebook

    IEEE is the world's largest technical professional organization dedicated to advancing technological innovation and excellence for the benefit of humanity.
    IEEE has offices in China, India, Japan, Singapore, and in the United
    States (California, New Jersey, New York, Washington, D.C.)
    3,409,150 people like this
    3,426,770 people follow this
    2,463 people checked in here
    http://www.ieee.org/
    +1 800-678-4333
    Send message
    contactcenter@ieee.org
    Educational Research Center · Engineering Service · Nonprofit Organization Privacy Policy

    https://www.facebook.com/IEEE.org/

    just visit and find me a single thread or comment, having anything to do with science or research

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dimiter_Popoff@21:1/5 to a a on Mon Jul 18 16:34:14 2022
    On 7/18/2022 15:58, a a wrote:
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:
    <snip>

    So IEEE is not science body, organization at all.

    If a a knew what he was talking about, he'd know that the main function of the IEEE is to publish a large collection of high-impact peer-reviewed scientific journals that deal with the science that underlies electronics. That is what science is about,
    even if a a doesn't have a clue about it.

    That's why I joined the organisation back around 1980. It's not all that obvious the current activities of the NSW Branch, but that's where the serious effort goes , and where the serious money gets spent.

    I've got just one short comment in that literature

    Sloman, A.W. "Comment on 'Computer aided simulation study of photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38 679-680 (1991).

    Because I mostly worked in the UK I published more the UK Institute of Physics journals, but there aren't as many of them, and Americans do tend to ignore them.

    --
    Bill Sloman, Sydney
    ok, ok, stop your delusiones and day dreaming

    IEEE lives on Facebook

    IEEE is the world's largest technical professional organization dedicated to advancing technological innovation and excellence for the benefit of humanity.
    IEEE has offices in China, India, Japan, Singapore, and in the United
    States (California, New Jersey, New York, Washington, D.C.)
    3,409,150 people like this
    3,426,770 people follow this
    2,463 people checked in here
    http://www.ieee.org/
    +1 800-678-4333
    Send message
    contactcenter@ieee.org
    Educational Research Center · Engineering Service · Nonprofit Organization Privacy Policy

    https://www.facebook.com/IEEE.org/

    just visit and find me a single thread or comment, having anything to do with science or research

    Oh God. Is this "a a" a new troll or a renamed version of the old ones.
    Perhaps new, some of the old ones at least knew to not be too loud
    on topics other than politics. Perhaps posting utterly illiterate
    claims is a technique to engage us, who knows. Like I do at the moment,
    what am I thinking....

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From a a@21:1/5 to Dimiter Popoff on Mon Jul 18 06:38:52 2022
    On Monday, 18 July 2022 at 15:34:22 UTC+2, Dimiter Popoff wrote:
    On 7/18/2022 15:58, a a wrote:
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:
    <snip>

    So IEEE is not science body, organization at all.

    If a a knew what he was talking about, he'd know that the main function of the IEEE is to publish a large collection of high-impact peer-reviewed scientific journals that deal with the science that underlies electronics. That is what science is
    about, even if a a doesn't have a clue about it.

    That's why I joined the organisation back around 1980. It's not all that obvious the current activities of the NSW Branch, but that's where the serious effort goes , and where the serious money gets spent.

    I've got just one short comment in that literature

    Sloman, A.W. "Comment on 'Computer aided simulation study of photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38 679-680 (1991).

    Because I mostly worked in the UK I published more the UK Institute of Physics journals, but there aren't as many of them, and Americans do tend to ignore them.

    --
    Bill Sloman, Sydney
    --ok, ok, stop your delusiones and day dreaming

    -- IEEE lives on Facebook

    --IEEE is the world's largest technical professional organization dedicated to advancing technological innovation and excellence for the benefit of humanity.
    --IEEE has offices in China, India, Japan, Singapore, and in the United
    States (California, New Jersey, New York, Washington, D.C.)
    3,409,150 people like this
    3,426,770 people follow this
    2,463 people checked in here
    http://www.ieee.org/
    +1 800-678-4333
    -- Send message
    contac...@ieee.org
    Educational Research Center · Engineering Service · Nonprofit Organization
    Privacy Policy

    -- https://www.facebook.com/IEEE.org/

    --just visit and find me a single thread or comment, having anything to do with science or research

    @Dimiter Popoff’s profile photo
    @Dimiter Popoff
    we all love your fake

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to a a on Mon Jul 18 06:41:32 2022
    On Monday, July 18, 2022 at 10:58:40 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    <snip>

    just visit and find me a single thread or comment, having anything to do with science or research

    The tricky bit would be finding something that you would comprehend as having anything to do with science or research.

    The comment that I published in the IEEE Transactions on Electron Devices and listed above - which you have snipped - had a quite a lot to do with research - it cited a bunch of references on photomultiplier non-linearity which are relevant to anybody
    doing serious research that exploits photomultipliers. So you've already had what you asked for, but failed to recognise it, which is exactly how you have always performed ever since you started posting your inanities here.

    --
    Bill sloman, Sydney

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  • From a a@21:1/5 to bill....@ieee.org on Mon Jul 18 06:57:52 2022
    On Monday, 18 July 2022 at 15:41:36 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 10:58:40 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:

    <snip>
    just visit and find me a single thread or comment, having anything to do with science or research

    you are stupid dog

    and your comments exactly represent media standards by IEEE.org
    since you use official email by IEEE.org

    listen me once again
    visit IEEE.org on Facebook
    and find a single thread, comment having anything to do with science or research

    https://www.facebook.com/IEEE.org/

    I am really not interested in your delusiones and day dreaming

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dimiter_Popoff@21:1/5 to a a on Mon Jul 18 16:59:44 2022
    On 7/18/2022 16:38, a a wrote:
    On Monday, 18 July 2022 at 15:34:22 UTC+2, Dimiter Popoff wrote:
    On 7/18/2022 15:58, a a wrote:
    On Monday, 18 July 2022 at 14:36:34 UTC+2, bill....@ieee.org wrote:
    On Monday, July 18, 2022 at 9:40:19 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 12:29:57 UTC+2, bill....@ieee.org wrote: >>>>>> On Monday, July 18, 2022 at 8:10:23 PM UTC+10, a a wrote:
    On Monday, 18 July 2022 at 04:12:12 UTC+2, Mike Monett wrote:
    whit3rd <whi...@gmail.com> wrote:
    On Sunday, July 17, 2022 at 1:00:00 PM UTC-7, a a wrote:
    <snip>

    So IEEE is not science body, organization at all.

    If a a knew what he was talking about, he'd know that the main function of the IEEE is to publish a large collection of high-impact peer-reviewed scientific journals that deal with the science that underlies electronics. That is what science is
    about, even if a a doesn't have a clue about it.

    That's why I joined the organisation back around 1980. It's not all that obvious the current activities of the NSW Branch, but that's where the serious effort goes , and where the serious money gets spent.

    I've got just one short comment in that literature

    Sloman, A.W. "Comment on 'Computer aided simulation study of photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38 679-680 (1991).

    Because I mostly worked in the UK I published more the UK Institute of Physics journals, but there aren't as many of them, and Americans do tend to ignore them.

    --
    Bill Sloman, Sydney
    --ok, ok, stop your delusiones and day dreaming

    -- IEEE lives on Facebook

    --IEEE is the world's largest technical professional organization dedicated to advancing technological innovation and excellence for the benefit of humanity.
    --IEEE has offices in China, India, Japan, Singapore, and in the United
    States (California, New Jersey, New York, Washington, D.C.)
    3,409,150 people like this
    3,426,770 people follow this
    2,463 people checked in here
    http://www.ieee.org/
    +1 800-678-4333
    -- Send message
    contac...@ieee.org
    Educational Research Center · Engineering Service · Nonprofit Organization
    Privacy Policy

    -- https://www.facebook.com/IEEE.org/

    --just visit and find me a single thread or comment, having anything to do with science or research

    @Dimiter Popoff’s profile photo
    @Dimiter Popoff
    we all love your fake

    Oh dear. if you are to be a troll at least learn how to post.
    Finding me/my photos is about the easiest thing to find on the net,
    at least learn how to do it. Better, instead of trolling invest
    your time into learning how to do something useful.

    ======================================================
    Dimiter Popoff, TGI http://www.tgi-sci.com ====================================================== http://www.flickr.com/photos/didi_tgi/

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  • From Dave Platt@21:1/5 to whit3rd@gmail.com on Mon Jul 18 09:05:27 2022
    In article <7cce474a-9b26-43bc-8fab-17f97e2bc1b1n@googlegroups.com>,
    whit3rd <whit3rd@gmail.com> wrote:
    On Saturday, July 16, 2022 at 5:38:44 PM UTC-7, Dave Platt wrote:

    The trickiest part was handling high pulse rates, where one pulse
    starts while the CSA is still recovering from the previous one.
    At some point I may sit down and try writing some DSP code to
    de-convolve the CSA's pulse shaping and turn the signal back
    into narrow impulses.

    The analog-days solution was a delay line amplifier; the long recovery tail >is exponential, so a difference amplification of V(t) - (1+epsilon)V(t-s) >flattens the recovery when (1+epsilon) equals the diminution of the signal >during 's' seconds. The infinite-impulse response or FIR filter is relatively easy
    work to do that.

    Yes, that would be pretty easy to code.

    Part of the complexity is that the signal chain in my setup is
    AC-coupled, so the strong positive-going pulse and its
    exponential-decay recovery are followed by a "sag" down into negative
    voltages, which then recovers exponentially to zero. If a second
    pulse hits before this recovery-to-DC is complete, the second
    pulse's peak will be offset downwards and a naive measure of its
    height will underestimate its energy.

    https://www.radagast.org/~dplatt/gamma/pulses.png is a screen-shot from
    my software's GUI when running in the "look at the signal" mode.

    What I did in my pulse-detection software was to use a state-machine
    approach, modeling the pulse in phases - waiting to trigger (blue),
    rising (green), falling back to the DC baseline (yellow), falling down
    below DC (orange), and then exponential recovery back upwards to
    baseline (red). For the latter I have a model for how long it
    _should_ take to recover back to DC (white), and I hold off further
    triggers until the estimated recovery time is complete. If the
    software sees a sudden rise in the signal during any of the
    post-peak phases, it's interpreted as a second pulse "too soon"
    and is discarded.

    Another approach I've been musing about, would be to use correlation - correlate the incoming pulse train with a known-good sample of the
    system's impulse response. I could capture one good clean pulse (or a
    few, and then average them) to create a reference... this would
    accurately model the impulse response of the crystal/PMT/amplifier as
    actually built. Then, simply run a multiply-and-add correlation to
    the samples as they come in during a measuring run. This ought to
    give me a nice, clean, fairly narrow (and close-to-symmetrical)
    detection pulse for each incoming pulse from the amplifer. This would
    give my state-machine pulse detector and input with the pulses
    more cleanly separated.

    The data rate is low enough and the pulses are short enough that it's
    probably cheaper to do it through brute-force multiply-and-add, rather
    than coding it as an FFT/multiply/iFFT.

    Some good info here: ><https://www.ortec-online.com/-/media/ametekortec/manuals/4/460-mnl.pdf>

    Thanks!

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  • From Dave Platt@21:1/5 to spamme@not.com on Mon Jul 18 08:42:05 2022
    In article <XnsAED78EB5BEF31idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:

    A very lucid explanation. Thanks.

    Quite welcome!

    I was able to find out what NORM is without having to ask you: "Naturally >ocurring radioactive materials." I'm so proud of myself:)

    :-)

    The next step in the obsession is to find NORM sources for yourself.
    Government and business buildings with granite facades are one
    source.

    How big are your scintillator crystals?

    Ugh... it's been years since I built the probes so I don't recall the
    exact size. I think they're both about 1" in diameter and an inch or
    two long.

    I also experimented with using one or more small LYSO crystals, as are
    used in PET scanners. They do work, but the lutetium is itself
    slightly radioactive and there's a constant flux of pulses from gammas generated within the crystal itself. Commercial PET scanners deal
    with this by ignoring (filtering out) pulses of the specific height corresponding to this gamma energy. That approach doesn't seem to
    work as well (for me at least) for doing gamma spectroscopy of low-
    level sources since the lutetium gammas still generate a broad
    Comptom continuum which tends to obscure the features I'm looking for.

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  • From Mike Monett@21:1/5 to Dave Platt on Mon Jul 18 17:41:11 2022
    dplatt@coop.radagast.org (Dave Platt) wrote:

    In article <XnsAED78EB5BEF31idtokenpost@88.198.57.247>,
    Mike Monett <spamme@not.com> wrote:

    A very lucid explanation. Thanks.

    Quite welcome!

    I was able to find out what NORM is without having to ask you: "Naturally >>ocurring radioactive materials." I'm so proud of myself:)

    :-)

    The next step in the obsession is to find NORM sources for yourself. Government and business buildings with granite facades are one
    source.

    How big are your scintillator crystals?

    Ugh... it's been years since I built the probes so I don't recall the
    exact size. I think they're both about 1" in diameter and an inch or
    two long.

    Wow! That's big. That's why your detectors are so sensitive.

    I found some sources for crystals. The smaller ones are not too expensive:

    1. https://www.gammaspectacular.com/blue/nai-tl-crystals

    2. Saint-Gobain has a lot of papers as well as crystals:

    https://www.crystals.saint-gobain.com/radiation-detection- scintillators/crystal-scintillators/lanthanum-bromide-labr3

    3. Hiler has more info on crystals. Quotes on request:

    https://www.hilger-crystals.co.uk/guide-to-inorganic-scintillator-crystals/

    4. More info:

    https://www.mirion.com/learning-center/lab-experiments/gamma-ray-detection- with-scintillators-lab-experiment

    5. Berkeley has a wide variety of detectors:

    https://www.berkeleynucleonics.com/scintillation-crystals-and-detectors

    Wow! You could get really deep into this topic. And spend 11,780 bazillion dollars.

    Thanks,

    Mike



    --
    MRM

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  • From John Miles, KE5FX@21:1/5 to Phil Hobbs on Tue Jul 19 18:04:25 2022
    On Monday, June 27, 2022 at 4:42:33 AM UTC-7, Phil Hobbs wrote:
    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate) you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or something.

    Phil, can you elaborate on this point? If the crystal and PMT are well- insulated from their surroundings, which they are, what mechanism
    would cause noticeable amounts of ion migration?

    It's definitely more convenient to run these with negative HV than it would be with positive HV, where you not only have to worry about DC blocking but
    also ripple. The latter seems to be a big deal, going by the Theremino
    docs and other sources.

    -- john, KE5FX

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  • From Anthony William Sloman@21:1/5 to All on Tue Jul 19 19:01:43 2022
    On Wednesday, July 20, 2022 at 11:04:28 AM UTC+10, John Miles, KE5FX wrote:
    On Monday, June 27, 2022 at 4:42:33 AM UTC-7, Phil Hobbs wrote:

    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate) you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at high voltage and coupling the pulses out with a cap or transformer or something.

    Phil, can you elaborate on this point? If the crystal and PMT are well- insulated from their surroundings, which they are, what mechanism
    would cause noticeable amounts of ion migration?

    It's definitely more convenient to run these with negative HV than it would be
    with positive HV, where you not only have to worry about DC blocking but
    also ripple. The latter seems to be a big deal, going by the Theremino
    docs and other sources.

    A high voltage across a photomultiplier faceplate will do it.

    At Cambridge Instruments, the photomultipliers we bought were selected to deliver the gain we needed with less than 1kV across the tube - which is to say across the glass faceplate.

    A quartz - silicon-dioxide - face-plate might have been expected to be immune, but they needed an expensive graded seal to couple them onto the glass body of the photopmultiplier tube

    Quite how 1kV got to be selected as the cut-off point was never revealed to me, but it was embedded in our purchasing specification.

    The tubes themselves were mounted hard up against a glass window in the (grounded metal) specimen chamber, so that they could detect the flashes of light coming of the scintillator in the Everhart-Thornley secondary electron detection system.

    Regular glass seems to contain enough metal ions for ionic migration to be a problem under kilo-volt potential differences.

    --
    Bill Sloman, Sydney

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  • From John Miles, KE5FX@21:1/5 to bill....@ieee.org on Tue Jul 19 21:10:59 2022
    On Tuesday, July 19, 2022 at 7:01:46 PM UTC-7, bill....@ieee.org wrote:
    A quartz - silicon-dioxide - face-plate might have been expected to be immune, but they needed an expensive graded seal to couple them
    onto the glass body of the photomultiplier tube

    I see, so the issue is the potential difference between the photocathode
    and the exterior metalwork. They seem to have thought of that, as the
    tube's metal frame is tied to the cathode pin.

    -- john, KE5FX

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  • From Anthony William Sloman@21:1/5 to All on Tue Jul 19 23:02:19 2022
    On Wednesday, July 20, 2022 at 2:11:03 PM UTC+10, John Miles, KE5FX wrote:
    On Tuesday, July 19, 2022 at 7:01:46 PM UTC-7, bill....@ieee.org wrote:
    A quartz - silicon-dioxide - face-plate might have been expected to be immune, but they needed an expensive graded seal to couple them
    onto the glass body of the photomultiplier tube

    I see, so the issue is the potential difference between the photocathode
    and the exterior metalwork. They seem to have thought of that, as the
    tube's metal frame is tied to the cathode pin.

    Some of it is. The anode isn't and none of the dynodes are, and every last one of them it is tied to a metal pin coming out of the base.

    --
    Bill Sloman, Sydney

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  • From John Miles, KE5FX@21:1/5 to bill....@ieee.org on Tue Jul 19 23:08:43 2022
    On Tuesday, July 19, 2022 at 11:02:22 PM UTC-7, bill....@ieee.org wrote:
    Some of it is. The anode isn't and none of the dynodes are, and every
    last one of them it is tied to a metal pin coming out of the base.

    Right, I'm talking about the metal frame that would be the other electrode
    in any ion-migration scenario involving the photocathode. You can see it
    in the photo at http://www.ke5fx.com/tube.png where the seller sacrificed
    one of the units for disassembly.

    That metal frame is at the same potential as the photocathode, so
    nothing is going to migrate across the faceplate.

    -- john, KE5FX

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  • From Phil Hobbs@21:1/5 to All on Wed Jul 20 07:40:14 2022
    John Miles, KE5FX wrote:
    On Monday, June 27, 2022 at 4:42:33 AM UTC-7, Phil Hobbs wrote:
    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the faceplate)
    you'll need to keep the cathode near ground to avoid ions migrating
    through the glass and corroding the PC. That means running the anode at
    high voltage and coupling the pulses out with a cap or transformer or
    something.

    Phil, can you elaborate on this point? If the crystal and PMT are well- insulated from their surroundings, which they are, what mechanism
    would cause noticeable amounts of ion migration?

    It's definitely more convenient to run these with negative HV than it would be
    with positive HV, where you not only have to worry about DC blocking but
    also ripple. The latter seems to be a big deal, going by the Theremino
    docs and other sources.

    -- john, KE5FX


    It's just ion migration through the glass envelope. I don't know if
    folks have found a good solution to it, but BITD this was a serious
    limitation.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Mike Monett@21:1/5 to Mike Monett on Wed Jul 20 14:11:07 2022
    Mike Monett <spamme@not.com> wrote:

    Mike Monett <spamme@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.

    And the positive anode should eliminate any ion migration through the glass.

    --
    MRM

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  • From Mike Monett@21:1/5 to Phil Hobbs on Wed Jul 20 13:46:35 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    John Miles, KE5FX wrote:
    On Monday, June 27, 2022 at 4:42:33 AM UTC-7, Phil Hobbs wrote:
    If you're going to use an ionic scintillator in contact with an end-on
    PMT (one where the photocathode is deposited directly on the
    faceplate) you'll need to keep the cathode near ground to avoid ions
    migrating through the glass and corroding the PC. That means running
    the anode at high voltage and coupling the pulses out with a cap or
    transformer or something.

    Phil, can you elaborate on this point? If the crystal and PMT are
    well- insulated from their surroundings, which they are, what mechanism
    would cause noticeable amounts of ion migration?

    It's definitely more convenient to run these with negative HV than it
    would be with positive HV, where you not only have to worry about DC
    blocking but also ripple. The latter seems to be a big deal, going by
    the Theremino docs and other sources.

    -- john, KE5FX


    It's just ion migration through the glass envelope. I don't know if
    folks have found a good solution to it, but BITD this was a serious limitation.

    Cheers

    Phil Hobbs

    RH Electronics doesn't seem worried:

    https://www.rhelectronics.store/diy-pic18-mca-kit-for-gamma-spectroscopy

    Here they show the output of the PMT and the pulse stretcher:

    https://static.wixstatic.com/media/e43988 _a63520f4ed07436a843ddc1be0fda46a~mv2.jpg

    Here they show the pulses from random gamma rays:

    https://video.wixstatic.com/video/e43988_ 8006efb319884c72b9d7f7418abdfa97/720p/mp4/file.mp4

    I guess it may take years for ion migration to show up. It probably depends
    on the type of glass, the thickness, the type of ion, any separating
    material, and the applied voltage. 800 Volts is not much.

    It should be easy to add a simple inverter and ground the cathode.

    Hamamatsu shows several types of cathodes:

    What is a photocathode?

    A thin photosensitive film formed on the inner side (vacuum) of the light
    input window. It converts light entering through the light input window
    into photoelectrons.

    - I didn't know that. Near infrared is 0.75 to 1.3 microns, so the file
    doesn't have to be very thick.

    Types of photocathode

    Bialkali photocathode for visible light region

    Multialkali photocathode with sensitivity extending to near infrared
    region

    Alkali-halide photocathode for UV light detection

    GaAs, InGaAs (group III-V compound semiconductors) with sensitivity from
    UV to near infrared region

    https://www.hamamatsu.com/us/en/product/optical-sensors/pmt/about_pmts.html




    --
    MRM

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  • From Mike Monett@21:1/5 to Mike Monett on Wed Jul 20 14:00:02 2022
    Mike Monett <spamme@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.
    --
    MRM

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  • From John Walliker@21:1/5 to Mike Monett on Wed Jul 20 07:45:08 2022
    On Wednesday, 20 July 2022 at 15:11:13 UTC+1, Mike Monett wrote:
    Mike Monett <spa...@not.com> wrote:

    Mike Monett <spa...@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.
    And the positive anode should eliminate any ion migration through the glass.


    Well, there are both positive and negative ions in the crystal, so reversing the
    polarity would just change the nature of what migrates.

    John

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  • From jlarkin@highlandsniptechnology.com@21:1/5 to jrwalliker@gmail.com on Wed Jul 20 08:18:17 2022
    On Wed, 20 Jul 2022 07:45:08 -0700 (PDT), John Walliker
    <jrwalliker@gmail.com> wrote:

    On Wednesday, 20 July 2022 at 15:11:13 UTC+1, Mike Monett wrote:
    Mike Monett <spa...@not.com> wrote:

    Mike Monett <spa...@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.
    And the positive anode should eliminate any ion migration through the glass. >>

    Well, there are both positive and negative ions in the crystal, so reversing the
    polarity would just change the nature of what migrates.

    John

    Migration after 10 dynodes of gain is better than migration at the
    photocathode where every electron literally counts.

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  • From Phil Hobbs@21:1/5 to Mike Monett on Wed Jul 20 15:53:02 2022
    Mike Monett wrote:
    Mike Monett <spamme@not.com> wrote:

    Mike Monett <spamme@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.

    And the positive anode should eliminate any ion migration through the glass.


    The anode isn't vulnerable to corrosion because it's not deposited on
    the glass, and it's a nice beefy piece of metal, compared with the very
    thin transparent photocathode.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Phil Hobbs@21:1/5 to Mike Monett on Wed Jul 20 15:51:40 2022
    Mike Monett wrote:
    Mike Monett <spamme@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.


    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Miles, KE5FX@21:1/5 to Phil Hobbs on Wed Jul 20 17:55:00 2022
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to All on Wed Jul 20 23:36:29 2022
    On Wednesday, July 20, 2022 at 5:55:04 PM UTC-7, John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.
    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply...

    Photomultipliers are current sources; the current gain is 'exposed to
    ripple from the PMT supply', so that isn't a design feature from which to expect
    any difference at all. If the pulses are short, filtering against the ripple (longer duration
    than the pulses) might not be difficult. You'll be rejecting dark current either way.

    I'd think transformer-coupling would be a natural way to capture pulses while rejecting lower
    frequency ripple and DC. In my experience with PMTs we used good regulated DC power.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to All on Thu Jul 21 12:36:00 2022
    On 21/07/2022 07:36, whit3rd wrote:
    On Wednesday, July 20, 2022 at 5:55:04 PM UTC-7, John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.
    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply...

    Photomultipliers are current sources; the current gain is 'exposed to
    ripple from the PMT supply', so that isn't a design feature from which to expect
    any difference at all. If the pulses are short, filtering against the ripple (longer duration
    than the pulses) might not be difficult. You'll be rejecting dark current either way.

    PMTs were mostly used in pulse counting mode for astronomy. Height of
    the pulse doesn't matter provided that there is one (or not).

    Image Photon Counting System, IPCS from Imperial College being the first
    new generation microchannel plate based imaging device in the 1980's.

    https://www.ing.iac.es/PR/wht_info/ipcs.html

    For the time it was incredibly sensitive (when compared to film or
    CCDs). CCDs improved very rapidly in the following decades.

    I'd think transformer-coupling would be a natural way to capture pulses while rejecting lower
    frequency ripple and DC. In my experience with PMTs we used good regulated DC power.

    My own experience was mostly of ion counting mass spec systems rather
    than photon counting. Deconstructed PMT in a hard vacuum and ion beams
    rather than light. We had to do some elaborate ion optics to provide a
    photon stop to prevent light from the plasma reaching the detector.

    Hard vacuum requires stainless steel and no paint so an effective photon
    stop is harder to make than it sounds.

    ISTR that in pulse counting mode it needed dead time correction once the
    count rate got high and that there was a cute way to run it in analogue
    mode by dropping the supply voltage and monitoring the current.

    In both cases the supply voltages were as stable as we could reasonably
    make them (more so for the analogue mode). Cross calibrating the
    analogue to pulse counting modes as a function of mass was quite bad for
    the detector but essential if the results were to be meaningful.

    https://en.wikipedia.org/wiki/Electron_multiplier

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to All on Thu Jul 21 09:14:23 2022
    John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    Right, as far as that goes.

    The photocathode is the high-Z end of the photomultiplier, and so most naturally goes furthest from ground. In free-space applications, we run
    the anode near ground and the photocathode at -1 to -2 kV, because the
    PC end doesn't draw any cuarrent to speak of.

    That makes it easy to get the (largish) anode current out into normal low-voltage circuitry. (*)

    The large scintillator crystal is out there where you can touch it, so
    for safety reasons it's good if it's kept near ground.

    It's important for sensitivity reasons that the scintillator crystal be connected to the PMT faceplate through a continuous path with refractive
    index at least as large as the glass of the PMT envelope.

    The reason is that a major fraction of the light from the scintillator
    is incident on its exit facet from angles beyond the critical angle for
    CsI -> air.

    I suspect that this is where the difficulty lies: If you have diffuse
    light in a medium of refractive index n, and want to couple the light efficiently into air, it turns out that your maximum efficiency is
    1/n**2, even with an arbitrarily good AR coating, That's usually a problem.

    Sooooo, to avoid losing signal, you want to avoid coupling light from
    your scintillator into air.

    The most straightforward way to avoid that is to optically-couple the scintillator to the PMT faceplate, either by direct contact or using
    some sort of index oil or gel. OK so far?
    It's also good if your detector survives use, though. Putting the
    scintillator at ground and the photocathode at -1 kV Photocathode
    corrosion due to halide ions drifting through the glass faceplate has
    been a real issue for a long time, and the saPower supply ripple is an easily-soluble problem, especially since a scintillation event is very
    bright in PMT terms--you aren't trying to do photon counting.

    I've used cascades of PNP cap multipliers to do some pretty fun things
    with PMTs, including getting (to me) impressive linearity for analogue
    RF modulated detection.

    Usually it's important for safety reasons that the metal housing for the
    big ugly scintillator crystal is near ground.

    Overall, for slowish counting applications, floating the PMT anode is a win.

    Cheers

    Phil Hobbs

    (*) That approach is also a good match to the (IME badly overrated) Cockroft_Walton scheme, where you run each dynode off a tap of a C-W multiplier. The C-W approach naturally gives you vaguely equally-spaced
    taps, and the high-Z end of the C_W matches the high-Z end of the PMT.
    It's superficially neat, but has serious problems with linearity and
    noise (especially at lower gain), not to mention the super ugly supply
    ripple effects.

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Martin Brown on Thu Jul 21 09:19:45 2022
    Martin Brown wrote:
    On 21/07/2022 07:36, whit3rd wrote:
    On Wednesday, July 20, 2022 at 5:55:04 PM UTC-7, John Miles, KE5FX wrote: >>> On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.
    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply...

    Photomultipliers are current sources; the current gain is 'exposed to
    ripple from the PMT supply', so that isn't a design feature from which
    to expect
    any difference at all.   If the pulses are short, filtering against
    the ripple (longer duration
    than the pulses) might not be difficult.   You'll be  rejecting dark
    current either way.

    PMTs were mostly used in pulse counting mode for astronomy. Height of
    the pulse doesn't matter provided that there is one (or not).

    Image Photon Counting System, IPCS from Imperial College being the first
    new generation microchannel plate based imaging device in the 1980's.

    https://www.ing.iac.es/PR/wht_info/ipcs.html

    For the time it was incredibly sensitive (when compared to film or
    CCDs). CCDs improved very rapidly in the following decades.

    I'd think transformer-coupling would be a natural way to capture
    pulses while rejecting lower
    frequency ripple and DC.   In my experience with PMTs  we used good
    regulated DC power.

    My own experience was mostly of ion counting mass spec systems rather
    than photon counting. Deconstructed PMT in a hard vacuum and ion beams
    rather than light. We had to do some elaborate ion optics to provide a
    photon stop to prevent light from the plasma reaching the detector.

    Hard vacuum requires stainless steel and no paint so an effective photon
    stop is harder to make than it sounds.

    You can use black chrome, though, no?


    ISTR that in pulse counting mode it needed dead time correction once the count rate got high and that there was a cute way to run it in analogue
    mode by dropping the supply voltage and monitoring the current.

    In both cases the supply voltages were as stable as we could reasonably
    make them (more so for the analogue mode). Cross calibrating the
    analogue to pulse counting modes as a function of mass was quite bad for
    the detector but essential if the results were to be meaningful.

    https://en.wikipedia.org/wiki/Electron_multiplier


    Yup. The microchannel plate is basically a massively-parallel version
    of the Channeltron electron multiplier.

    I was looking at Photonis's MCP page the other day, and they were all
    smug about nobody using curved or chevron-shaped channels anymore, just
    their original version.

    The reason for the curved channels, of course, was to force ions to hit
    the walls instead of being accelerated directly at the photocathode,
    damaging it and causing very very bright ion events.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to All on Thu Jul 21 09:24:19 2022
    John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    [fixed a few editing scars]

    Right, as far as that goes.

    The photocathode is the high-Z end of the photomultiplier, and so most naturally goes furthest from ground. In free-space applications, we run
    the anode near ground and the photocathode at -1 to -2 kV, because the
    PC end doesn't draw any cuarrent to speak of.

    That makes it easy to get the (largish) anode current out into normal low-voltage circuitry. (*)

    The large scintillator crystal is out there where you can touch it, so
    for safety reasons it's good if it's kept near ground.

    It's important for sensitivity reasons that the scintillator crystal be connected to the PMT faceplate through a continuous path with refractive
    index at least as large as the glass of the PMT envelope.

    The reason is that a major fraction of the light from the scintillator
    is incident on its exit facet from angles beyond the critical angle for
    CsI -> air.

    I suspect that this is where the difficulty lies: If you have diffuse
    light in a medium of refractive index n, and want to couple the light efficiently into air, it turns out that your maximum efficiency is
    1/n**2, even with an arbitrarily good AR coating, That's usually a problem.

    Sooooo, to avoid losing signal, you want to avoid coupling light from
    your scintillator into air.

    The most straightforward way to avoid that is to optically-couple the scintillator to the PMT faceplate, either by direct contact or using
    some sort of index oil or gel. OK so far?

    It's also good if your detector survives use, though. Putting the
    scintillator at ground and the photocathode at -1 kV

    |doesn't work well, it turns out.

    Photocathode corrosion due to halide ions drifting through the glass faceplate has been a real issue for a long time, and
    | I don't know whether improved faceplate materials have helped that much.

    Power supply ripple is an easily-soluble problem, especially since a scintillation event is very bright in PMT terms--you aren't trying to do
    photon counting.

    I've used cascades of PNP cap multipliers to do some pretty fun things
    with PMTs, including getting (to me) impressive linearity for analogue
    RF modulated detection.

    Usually it's important for safety reasons that the metal housing for the
    big ugly scintillator crystal is near ground.

    Overall, for slowish counting applications, floating the PMT anode is a win.

    Cheers

    Phil Hobbs

    (*) That approach is also a good match to the (IME badly overrated) Cockroft_Walton scheme, where you run each dynode off a tap of a C-W multiplier. The C-W approach naturally gives you vaguely equally-spaced
    taps, and the high-Z end of the C_W matches the high-Z end of the PMT.
    It's superficially neat, but has serious problems with linearity and
    noise (especially at lower gain), not to mention the super ugly supply
    ripple effects.

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to '''newspam'''@nonad.co.uk on Thu Jul 21 07:25:38 2022
    On Thu, 21 Jul 2022 12:36:00 +0100, Martin Brown
    <'''newspam'''@nonad.co.uk> wrote:

    On 21/07/2022 07:36, whit3rd wrote:
    On Wednesday, July 20, 2022 at 5:55:04 PM UTC-7, John Miles, KE5FX wrote: >>> On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.
    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply...

    Photomultipliers are current sources; the current gain is 'exposed to
    ripple from the PMT supply', so that isn't a design feature from which to expect
    any difference at all. If the pulses are short, filtering against the ripple (longer duration
    than the pulses) might not be difficult. You'll be rejecting dark current either way.

    PMTs were mostly used in pulse counting mode for astronomy. Height of
    the pulse doesn't matter provided that there is one (or not).

    Image Photon Counting System, IPCS from Imperial College being the first
    new generation microchannel plate based imaging device in the 1980's.

    https://www.ing.iac.es/PR/wht_info/ipcs.html

    For the time it was incredibly sensitive (when compared to film or
    CCDs). CCDs improved very rapidly in the following decades.

    I'd think transformer-coupling would be a natural way to capture pulses while rejecting lower
    frequency ripple and DC. In my experience with PMTs we used good regulated DC power.

    My own experience was mostly of ion counting mass spec systems rather
    than photon counting. Deconstructed PMT in a hard vacuum and ion beams
    rather than light. We had to do some elaborate ion optics to provide a
    photon stop to prevent light from the plasma reaching the detector.

    Hard vacuum requires stainless steel and no paint so an effective photon
    stop is harder to make than it sounds.


    We had the opposite problem: detecting the light from a plasma but
    blocking the ions that would darken our window. I wanted to do a thing
    with angled slats to bounce the light forward but that the ions would
    impact, but the semi company stuck with a plate with tiny holes, to
    let a little light and a few ions through.

    Bad idea, but then they stole our detector circuit so I hope their
    windows all darken.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Phil Hobbs on Thu Jul 21 10:31:00 2022
    Phil Hobbs wrote:
    John Miles, KE5FX wrote:
    <snip long explanation>

    I should add, of course, that having a huge E field inside the glass is
    bound to reduce the photocathode quantum yield despite the shielding
    effect of the PC itself.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Thu Jul 21 07:30:56 2022
    On Thu, 21 Jul 2022 09:14:23 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    Right, as far as that goes.

    The photocathode is the high-Z end of the photomultiplier, and so most >naturally goes furthest from ground. In free-space applications, we run
    the anode near ground and the photocathode at -1 to -2 kV, because the
    PC end doesn't draw any cuarrent to speak of.

    That makes it easy to get the (largish) anode current out into normal >low-voltage circuitry. (*)

    The large scintillator crystal is out there where you can touch it, so
    for safety reasons it's good if it's kept near ground.

    It's important for sensitivity reasons that the scintillator crystal be >connected to the PMT faceplate through a continuous path with refractive >index at least as large as the glass of the PMT envelope.

    The reason is that a major fraction of the light from the scintillator
    is incident on its exit facet from angles beyond the critical angle for
    CsI -> air.

    I suspect that this is where the difficulty lies: If you have diffuse
    light in a medium of refractive index n, and want to couple the light >efficiently into air, it turns out that your maximum efficiency is
    1/n**2, even with an arbitrarily good AR coating, That's usually a problem.

    Sooooo, to avoid losing signal, you want to avoid coupling light from
    your scintillator into air.

    The most straightforward way to avoid that is to optically-couple the >scintillator to the PMT faceplate, either by direct contact or using
    some sort of index oil or gel. OK so far?
    It's also good if your detector survives use, though. Putting the >scintillator at ground and the photocathode at -1 kV Photocathode
    corrosion due to halide ions drifting through the glass faceplate has
    been a real issue for a long time, and the saPower supply ripple is an >easily-soluble problem, especially since a scintillation event is very
    bright in PMT terms--you aren't trying to do photon counting.

    I've used cascades of PNP cap multipliers to do some pretty fun things
    with PMTs, including getting (to me) impressive linearity for analogue
    RF modulated detection.

    Usually it's important for safety reasons that the metal housing for the
    big ugly scintillator crystal is near ground.

    Overall, for slowish counting applications, floating the PMT anode is a win.

    Cheers

    Phil Hobbs

    (*) That approach is also a good match to the (IME badly overrated) >Cockroft_Walton scheme, where you run each dynode off a tap of a C-W >multiplier. The C-W approach naturally gives you vaguely equally-spaced >taps, and the high-Z end of the C_W matches the high-Z end of the PMT.
    It's superficially neat, but has serious problems with linearity and
    noise (especially at lower gain), not to mention the super ugly supply
    ripple effects.

    There is the idea of an active capacitor for an RC lowpass filter,
    nanely a modest-sized cap whose low end is intelligently driven by an
    amp, so it looks like a much bigger cap on the top end.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to jlarkin@highlandsniptechnology.com on Thu Jul 21 10:47:08 2022
    jlarkin@highlandsniptechnology.com wrote:
    On Thu, 21 Jul 2022 09:14:23 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    John Miles, KE5FX wrote:
    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    Right, as far as that goes.

    The photocathode is the high-Z end of the photomultiplier, and so most
    naturally goes furthest from ground. In free-space applications, we run
    the anode near ground and the photocathode at -1 to -2 kV, because the
    PC end doesn't draw any cuarrent to speak of.

    That makes it easy to get the (largish) anode current out into normal
    low-voltage circuitry. (*)

    The large scintillator crystal is out there where you can touch it, so
    for safety reasons it's good if it's kept near ground.

    It's important for sensitivity reasons that the scintillator crystal be
    connected to the PMT faceplate through a continuous path with refractive
    index at least as large as the glass of the PMT envelope.

    The reason is that a major fraction of the light from the scintillator
    is incident on its exit facet from angles beyond the critical angle for
    CsI -> air.

    I suspect that this is where the difficulty lies: If you have diffuse
    light in a medium of refractive index n, and want to couple the light
    efficiently into air, it turns out that your maximum efficiency is
    1/n**2, even with an arbitrarily good AR coating, That's usually a problem. >>
    Sooooo, to avoid losing signal, you want to avoid coupling light from
    your scintillator into air.

    The most straightforward way to avoid that is to optically-couple the
    scintillator to the PMT faceplate, either by direct contact or using
    some sort of index oil or gel. OK so far?
    It's also good if your detector survives use, though. Putting the
    scintillator at ground and the photocathode at -1 kV Photocathode
    corrosion due to halide ions drifting through the glass faceplate has
    been a real issue for a long time, and the saPower supply ripple is an
    easily-soluble problem, especially since a scintillation event is very
    bright in PMT terms--you aren't trying to do photon counting.

    I've used cascades of PNP cap multipliers to do some pretty fun things
    with PMTs, including getting (to me) impressive linearity for analogue
    RF modulated detection.

    Usually it's important for safety reasons that the metal housing for the
    big ugly scintillator crystal is near ground.

    Overall, for slowish counting applications, floating the PMT anode is a win. >>
    Cheers

    Phil Hobbs

    (*) That approach is also a good match to the (IME badly overrated)
    Cockroft_Walton scheme, where you run each dynode off a tap of a C-W
    multiplier. The C-W approach naturally gives you vaguely equally-spaced
    taps, and the high-Z end of the C_W matches the high-Z end of the PMT.
    It's superficially neat, but has serious problems with linearity and
    noise (especially at lower gain), not to mention the super ugly supply
    ripple effects.

    There is the idea of an active capacitor for an RC lowpass filter,
    nanely a modest-sized cap whose low end is intelligently driven by an
    amp, so it looks like a much bigger cap on the top end.

    Yup. Back in the long ago (1984ish), I built a power supply filter that
    got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some piezo
    stacks. It worked by lifting the cold end, sensing the hot end via a
    100 nF, 3 kV film cap, and wiggling the cold end to keep it still. (It
    had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with that feedforward trick of Woodward's, where you use another op amp to measure
    the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end of
    the cap with some super beefy amplifier to make the top stay still.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Martin Brown on Thu Jul 21 13:23:16 2022
    Martin Brown wrote:
    On 21/07/2022 15:25, jlarkin@highlandsniptechnology.com wrote:

    We had the opposite problem: detecting the light from a plasma but
    blocking the ions that would darken our window. I wanted to do a thing
    with angled slats to bounce the light forward but that the ions would
    impact, but the semi company stuck with a plate with tiny holes, to
    let a little light and a few ions through.

    Simplest solution to stop ions going in straight lines (but not
    neutrals) is a local magnetic field and some drift length.

    Bad idea, but then they stole our detector circuit so I hope their
    windows all darken.

    There is usually plenty of light (and heat) from a 8000K plasma (at
    least one at 1 bar like ours). There is a pinhole sampling cone into it.

    Protecting the instrument from coolant failure and the hard vacuum from plasma flame out was a major part of the safety critical side of things.
    It was worse in the early days when the vacuum pumps were diffusion. Any
    sort of cock up and you had hot silicone oil all over the place.


    Yeah, I used to own a Denton 502 bell-jar evaporator that had an oil
    diffusion pump. Getting that sucker cleaned up after a roughing-pump
    incident was a huge pain.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to jlarkin@highlandsniptechnology.com on Thu Jul 21 18:19:21 2022
    On 21/07/2022 15:25, jlarkin@highlandsniptechnology.com wrote:

    We had the opposite problem: detecting the light from a plasma but
    blocking the ions that would darken our window. I wanted to do a thing
    with angled slats to bounce the light forward but that the ions would
    impact, but the semi company stuck with a plate with tiny holes, to
    let a little light and a few ions through.

    Simplest solution to stop ions going in straight lines (but not
    neutrals) is a local magnetic field and some drift length.

    Bad idea, but then they stole our detector circuit so I hope their
    windows all darken.

    There is usually plenty of light (and heat) from a 8000K plasma (at
    least one at 1 bar like ours). There is a pinhole sampling cone into it.

    Protecting the instrument from coolant failure and the hard vacuum from
    plasma flame out was a major part of the safety critical side of things.
    It was worse in the early days when the vacuum pumps were diffusion. Any
    sort of cock up and you had hot silicone oil all over the place.

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Miles, KE5FX@21:1/5 to Phil Hobbs on Thu Jul 21 14:40:41 2022
    On Thursday, July 21, 2022 at 7:31:07 AM UTC-7, Phil Hobbs wrote:
    I should add, of course, that having a huge E field inside the glass is
    bound to reduce the photocathode quantum yield despite the shielding
    effect of the PC itself.

    Yep, I think it's clear enough that allowing the faceplate to act as an
    HV dielectric is a Bad Idea. But it also seems easier to avoid doing
    that by tying the exterior frame to the cathode as the manufacturer has
    done here, than to swap the polarity and deal with the HV at the
    other end where the signal is extracted.

    As far as the need to insulate the crystal is concerned, you'll need to
    do that anyway to avoid exposing the user to thallium, I'd imagine. :-P

    The question of whether it makes a difference in terms of ripple
    is worth thinking through a little further. I see whit3rd's point, but
    the effect of stray C seems worth considering before concluding that
    the polarity doesn't make a difference.

    -- john, KE5FX

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to jmiles@gmail.com on Thu Jul 21 22:50:34 2022
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    The capacitor will have high voltage on it. This could destroy any electroncs that inadvertently got connected badly.

    You don't need to couple to the anode. Just take the signal off the cathode like the old cathode followers of yesteryear.

    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Thu Jul 21 22:44:08 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Mike Monett <spamme@not.com> wrote:

    Mike Monett <spamme@not.com> wrote:

    [...]

    It should be easy to add a simple inverter and ground the cathode.

    Oops - it is already grounded.

    And the positive anode should eliminate any ion migration through the
    glass.


    The anode isn't vulnerable to corrosion because it's not deposited on
    the glass, and it's a nice beefy piece of metal, compared with the very
    thin transparent photocathode.

    Cheers

    Phil Hobbs

    The anode pin goes through the glass. Metal ions are positively charged, so they are repelled by the positive anode. This eliminates any metal ion migration through the glass.




    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Thu Jul 21 19:00:20 2022
    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    The capacitor will have high voltage on it. This could destroy any electroncs that inadvertently got connected badly.

    You don't need to couple to the anode. Just take the signal off the cathode like the old cathode followers of yesteryear.


    There's no signal at the cathode to speak of--almost all the anode
    current comes in via the dynodes.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to Mike Monett on Thu Jul 21 16:08:42 2022
    On Thursday, July 21, 2022 at 3:50:40 PM UTC-7, Mike Monett wrote:
    "John Miles, KE5FX" <jmi...@gmail.com> wrote:

    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple...

    The capacitor will have high voltage on it. This could destroy any electroncs that inadvertently got connected badly.

    You don't need to couple to the anode. Just take the signal off the cathode like the old cathode followers of yesteryear.

    A PMT cathode is typically a multialkali evaporated coating on the end of the tube, has
    significant stray capacitance, and the signal there is weak (un-multiplied, no benefit
    from the PMT gain).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Thu Jul 21 23:09:12 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter that
    got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some piezo
    stacks. It worked by lifting the cold end, sensing the hot end via a
    100 nF, 3 kV film cap, and wiggling the cold end to keep it still. (It
    had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with that feedforward trick of Woodward's, where you use another op amp to measure
    the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end of
    the cap with some super beefy amplifier to make the top stay still.

    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 Ohm
    load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.





    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Fri Jul 22 00:05:42 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    "John Miles, KE5FX" <jmiles@gmail.com> wrote:

    On Wednesday, July 20, 2022 at 12:51:46 PM UTC-7, Phil Hobbs wrote:
    Yup. Grounded-cathode is the usual method with scintillators. You
    couple the pulses out with a capacitor, so it's not that big a deal.

    I seriously do not understand this. With a grounded cathode, the
    signal you're extracting at the anode end is exposed to ripple from
    the PMT supply, without benefit of a multi-megohm divider chain.
    There's also the need to use a DC restorer of some sort to figure out
    where the baseline is. Both of these problems go away with a
    grounded anode. Seems like a no-brainer.

    -- john, KE5FX

    The capacitor will have high voltage on it. This could destroy any
    electroncs that inadvertently got connected badly.

    You don't need to couple to the anode. Just take the signal off the
    cathode like the old cathode followers of yesteryear.


    There's no signal at the cathode to speak of--almost all the anode
    current comes in via the dynodes.

    Cheers

    Phil Hobbs

    Right. I got derailed by the positive pulses from the RH Electronics MCA.

    Got to find out how they do that.



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Thu Jul 21 19:23:03 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter that
    got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some piezo
    stacks. It worked by lifting the cold end, sensing the hot end via a
    100 nF, 3 kV film cap, and wiggling the cold end to keep it still. (It
    had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with that
    feedforward trick of Woodward's, where you use another op amp to measure
    the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end of
    the cap with some super beefy amplifier to make the top stay still.

    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to
    couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Thu Jul 21 23:53:53 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter
    that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some
    piezo stacks. It worked by lifting the cold end, sensing the hot end
    via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it
    still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with
    that feedforward trick of Woodward's, where you use another op amp to
    measure the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end
    of the cap with some super beefy amplifier to make the top stay still.

    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6
    Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to
    couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These
    won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~ mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7 20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Larkin@21:1/5 to All on Thu Jul 21 17:17:38 2022
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter
    that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some
    piezo stacks. It worked by lifting the cold end, sensing the hot end
    via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it
    still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with
    that feedforward trick of Woodward's, where you use another op amp to
    measure the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end
    of the cap with some super beefy amplifier to make the top stay still. >>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6
    Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to
    couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~ >mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7 >20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Thu Jul 21 20:35:52 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter
    that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some
    piezo stacks. It worked by lifting the cold end, sensing the hot end
    via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it
    still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in
    pretty handy. I could probably have done considerably better with
    that feedforward trick of Woodward's, where you use another op amp to
    measure the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end
    of the cap with some super beefy amplifier to make the top stay still. >>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6
    Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to
    couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~ mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7 20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    Probably from a TIA.

    One approach is to use an old-fashioned low-gain MMIC--most are
    basically Darlingtons with resistive feedback, so they invert.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Carl@21:1/5 to Martin Brown on Thu Jul 21 22:49:00 2022
    On 7/21/22 13:19, Martin Brown wrote:

    Protecting the instrument from coolant failure and the hard vacuum from plasma flame out was a major part of the safety critical side of things.
    It was worse in the early days when the vacuum pumps were diffusion. Any
    sort of cock up and you had hot silicone oil all over the place.

    Why weren't you running Santovac 5 instead of silicone oil? Same base
    pressure as dc705 and no worries about insulating films from ion
    bombardment if a little didn't get cleaned up after a backstreaming
    incident :-).

    --
    Regards,
    Carl

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dimiter_Popoff@21:1/5 to John Larkin on Fri Jul 22 12:30:37 2022
    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter
    that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some
    piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it
    still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>> pretty handy. I could probably have done considerably better with
    that feedforward trick of Woodward's, where you use another op amp to >>>>> measure the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name.
    That's the trick where you use an RC lowpass, and drive the cold end >>>>> of the cap with some super beefy amplifier to make the top stay still. >>>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6
    Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to
    couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These
    won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~ >> mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7 >> 20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to Carl on Fri Jul 22 10:38:04 2022
    On 22/07/2022 03:49, Carl wrote:
    On 7/21/22 13:19, Martin Brown wrote:

    Protecting the instrument from coolant failure and the hard vacuum
    from plasma flame out was a major part of the safety critical side of
    things. It was worse in the early days when the vacuum pumps were
    diffusion. Any sort of cock up and you had hot silicone oil all over
    the place.

    Why weren't you running Santovac 5 instead of silicone oil?  Same base pressure as dc705 and no worries about insulating films from ion
    bombardment if a little didn't get cleaned up after a backstreaming
    incident :-).

    They might have been for all I know. I did the software and firmware for
    the embedded control system. I wasn't involved with the actual filling
    of the diffusion pumps with whatever gunk they used. All I knew about it
    was that on flame out we had to close the gate valve very quickly or it
    would be a painful strip down and clean operation for some unlucky
    technician. Mostly it worked fast enough but not always.

    Life improved considerably when they moved onto turbo-molecular pumps
    and for a while performance was improved even more by maglev ones.

    Then one day an earthquake in Tokyo suddenly moved the Earth sideways by
    an inch instantaneously and every damn one of them was destroyed. I
    remember it well since in the quiet of the evening I heard the
    earthquake coming (I have no idea how but I was wondering about the
    strange train like sound outside when the jolt suddenly arrived).

    We were busy doing turbo pump swaps for weeks and after that
    conventional bearings were specified for earthquake zones.

    The maglevs had been out in the field for a couple of years before this
    rather nasty vulnerability became apparent.

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Fri Jul 22 12:56:05 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]
    I shall write them and ask where they get those positive pulses.

    Probably from a TIA.

    One approach is to use an old-fashioned low-gain MMIC--most are
    basically Darlingtons with resistive feedback, so they invert.

    Cheers

    Phil Hobbs

    I begin to suspect a simple inverter. This shows the schematic of the
    Theremino about 1/3 of the way down. 100 Meg feedback to a flyback HV generator, 2 Meg PMT load, grounded cathode, pulse-shaping network to a grounded emitter inverter. No concern about linearity. One thing I don't understand is a 1N4148 connected betwen the base and ground to catch
    negative pulses. I wonder if this is a cheap log converter:

    https://physicsopenlab.org/2016/01/26/diy-gamma-spectrometry/

    I think I'll run mine with a negative cathode to avoid mistakes wiping out
    the preamplifier. It's not going to be in operation long enough to worry
    about ion migration. Then find out how RH inverts their pulses.


    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Martin Brown on Fri Jul 22 09:07:32 2022
    Martin Brown wrote:
    On 22/07/2022 03:49, Carl wrote:
    On 7/21/22 13:19, Martin Brown wrote:

    Protecting the instrument from coolant failure and the hard vacuum
    from plasma flame out was a major part of the safety critical side of
    things. It was worse in the early days when the vacuum pumps were
    diffusion. Any sort of cock up and you had hot silicone oil all over
    the place.

    Why weren't you running Santovac 5 instead of silicone oil?  Same base
    pressure as dc705 and no worries about insulating films from ion
    bombardment if a little didn't get cleaned up after a backstreaming
    incident :-).

    They might have been for all I know. I did the software and firmware for
    the embedded control system. I wasn't involved with the actual filling
    of the diffusion pumps with whatever gunk they used. All I knew about it
    was that on flame out we had to close the gate valve very quickly or it
    would be a painful strip down and clean operation for some unlucky technician. Mostly it worked fast enough but not always.

    Life improved considerably when they moved onto turbo-molecular pumps
    and for a while performance was improved even more by maglev ones.

    Then one day an earthquake in Tokyo suddenly moved the Earth sideways by
    an inch instantaneously and every damn one of them was destroyed. I
    remember it well since in the quiet of the evening I heard the
    earthquake coming (I have no idea how but I was wondering about the
    strange train like sound outside when the jolt suddenly arrived).

    We were busy doing turbo pump swaps for weeks and after that
    conventional bearings were specified for earthquake zones.

    The maglevs had been out in the field for a couple of years before this rather nasty vulnerability became apparent.


    Did any of the casings let go?

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Fri Jul 22 09:15:55 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]
    I shall write them and ask where they get those positive pulses.

    Probably from a TIA.

    One approach is to use an old-fashioned low-gain MMIC--most are
    basically Darlingtons with resistive feedback, so they invert.

    Cheers

    Phil Hobbs

    I begin to suspect a simple inverter. This shows the schematic of the Theremino about 1/3 of the way down. 100 Meg feedback to a flyback HV generator, 2 Meg PMT load, grounded cathode, pulse-shaping network to a grounded emitter inverter. No concern about linearity. One thing I don't understand is a 1N4148 connected betwen the base and ground to catch
    negative pulses. I wonder if this is a cheap log converter:

    https://physicsopenlab.org/2016/01/26/diy-gamma-spectrometry/

    I think I'll run mine with a negative cathode to avoid mistakes wiping out the preamplifier. It's not going to be in operation long enough to worry about ion migration. Then find out how RH inverts their pulses.



    Looks like it's for short circuit protection. A spark across the output terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Fri Jul 22 13:50:57 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Looks like it's for short circuit protection. A spark across the output terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    That is precisely why I do not want to run mine with 800 Volts on the anode.



    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Fri Jul 22 07:11:24 2022
    On Fri, 22 Jul 2022 12:30:37 +0300, Dimiter_Popoff <dp@tgi-sci.com>
    wrote:

    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter >>>>>> that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some
    piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it
    still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>>> pretty handy. I could probably have done considerably better with >>>>>> that feedforward trick of Woodward's, where you use another op amp to >>>>>> measure the error voltage of the main one, and add in its output.

    Another approach like that is the Kanner Kap, which wasn't first
    invented by Kanner, but he now owns it on account of the cute name. >>>>>> That's the trick where you use an RC lowpass, and drive the cold end >>>>>> of the cap with some super beefy amplifier to make the top stay still. >>>>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 >>>>> Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to >>>> couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >>> won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~ >>> mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7 >>> 20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Fri Jul 22 08:40:36 2022
    On Fri, 22 Jul 2022 09:15:55 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]
    I shall write them and ask where they get those positive pulses.

    Probably from a TIA.

    One approach is to use an old-fashioned low-gain MMIC--most are
    basically Darlingtons with resistive feedback, so they invert.

    Cheers

    Phil Hobbs

    I begin to suspect a simple inverter. This shows the schematic of the
    Theremino about 1/3 of the way down. 100 Meg feedback to a flyback HV
    generator, 2 Meg PMT load, grounded cathode, pulse-shaping network to a
    grounded emitter inverter. No concern about linearity. One thing I don't
    understand is a 1N4148 connected betwen the base and ground to catch
    negative pulses. I wonder if this is a cheap log converter:

    https://physicsopenlab.org/2016/01/26/diy-gamma-spectrometry/

    I think I'll run mine with a negative cathode to avoid mistakes wiping out >> the preamplifier. It's not going to be in operation long enough to worry
    about ion migration. Then find out how RH inverts their pulses.



    Looks like it's for short circuit protection. A spark across the output >terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    T3 looks well protected to me. The problem is that it should be Q3. T
    means transformer.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Tauno Voipio@21:1/5 to Mike Monett on Fri Jul 22 18:54:56 2022
    On 22.7.22 15.56, Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]
    I shall write them and ask where they get those positive pulses.

    Probably from a TIA.

    One approach is to use an old-fashioned low-gain MMIC--most are
    basically Darlingtons with resistive feedback, so they invert.

    Cheers

    Phil Hobbs

    I begin to suspect a simple inverter. This shows the schematic of the Theremino about 1/3 of the way down. 100 Meg feedback to a flyback HV generator, 2 Meg PMT load, grounded cathode, pulse-shaping network to a grounded emitter inverter. No concern about linearity. One thing I don't understand is a 1N4148 connected betwen the base and ground to catch
    negative pulses. I wonder if this is a cheap log converter:

    https://physicsopenlab.org/2016/01/26/diy-gamma-spectrometry/

    I think I'll run mine with a negative cathode to avoid mistakes wiping out the preamplifier. It's not going to be in operation long enough to worry about ion migration. Then find out how RH inverts their pulses.


    The diode is there to prevent the base-emitter diode from zenering,
    and also to protect from large negative pulses.

    --

    -TV

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dimiter_Popoff@21:1/5 to jlarkin@highlandsniptechnology.com on Fri Jul 22 20:06:24 2022
    On 7/22/2022 17:11, jlarkin@highlandsniptechnology.com wrote:
    On Fri, 22 Jul 2022 12:30:37 +0300, Dimiter_Popoff <dp@tgi-sci.com>
    wrote:

    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter >>>>>>> that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some >>>>>>> piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it >>>>>>> still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>>>> pretty handy. I could probably have done considerably better with >>>>>>> that feedforward trick of Woodward's, where you use another op amp to >>>>>>> measure the error voltage of the main one, and add in its output. >>>>>>>
    Another approach like that is the Kanner Kap, which wasn't first >>>>>>> invented by Kanner, but he now owns it on account of the cute name. >>>>>>> That's the trick where you use an RC lowpass, and drive the cold end >>>>>>> of the cap with some super beefy amplifier to make the top stay still. >>>>>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 >>>>>> Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to >>>>> couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >>>> won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~
    mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7
    20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.


    No need to do it that complicated, there just is no energy resolution to
    worry about too much. They measure it in %, FWHM at the 661.6 137Cs peak divided by 661.6. NaI detectors can go down to around 6%, usually 8 or
    even 10 is still acceptable. This is 40keV FWHM at best, out of a
    spectrum well within 2 MeV, more like 1.5. People often measure
    1k spectra with NaI where clearly 128 channels would be plenty.
    (Compare that to something like 1.3keV FWHM for the 137Cs line
    with a Ge detector, with these you need 8 or 16k to get the full
    picture).

    I did a PMT circuit for photon counting a few years ago for a TLD
    reader I designed, http://tgi-sci.com/tgi/tld/index.htm (no PHA).
    Since the PMT glass hangs in the air there was no issue biasing it
    negatively and coupling the anode into one of the modern day fast
    opamps ADI make, works pretty well - throughput being around 22
    million photons/second.

    But my first MCA card for NaI - designed >30 years ago, the so called
    TISA card - was expecting only detectors with negative bias. I had no
    idea what detectors could be etc., I just designed the MCA card - and
    it had to deliver up to 3 mA as the detectors it must have been meant
    for had a preamp bleeding the HV for power.... (it could do up
    to 1200V/3mA, programmable).

    More recently I had a customer who wanted to connect an NaI
    detector to one of our netMCA-s. The detector had just one BNC,
    for both +HV in and signal out. So I had to build a tiny splitter
    box for it... Clearly one gets one more pole in such a configuration
    but it is too slow and is practically immaterial. Worked with the
    standard netMCA HV configuration (up to 5kV for Ge), though the
    HV had to be set to something like 2kV to compensate for the drop
    over around 30 megaohm in the output filter (Ge detectors consume
    practically no current).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Mike Monett on Fri Jul 22 18:23:16 2022
    Mike Monett <spamme@not.com> wrote:

    [..]

    I think I'll run mine with a negative cathode to avoid mistakes wiping
    out the preamplifier. It's not going to be in operation long enough to
    worry about ion migration. Then find out how RH inverts their pulses.

    Got a reply from RH. They don't. You do:

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Hello Mike,

    To flip the pulse polarity you can use a classic inverting OP-AMP circuit.

    The chip op-amp you will use has to be able to process fast PMT pulses.
    Usually 10MHz chip is enough in most cases with NaI(Tl) probe.

    Please note, the MCA input specifications require for input signal
    amplitude of 0mV-3300mV

    Thank you
    Alex
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Now I have to figure out the input impedance of the inverter. I'll have to
    fire up the PMT and see what amplitude the pulses are.

    Fortunately, my Radium order just arrived so I will have some signals.

    Unfortunately the decay steps are alpha and beta. The scintillator is
    gamma, so I don't think Ra will help, but it drives my Radiacode crazy.
    First time I have heard the alarm. No wonder it made the girls who painted
    it on their bodies glow in the dark.

    I have some volcanic rock on order. I'll have to bug John and Dave and find
    out where they got their sources. This stuff is tough to find. They think
    you want to make a bomb or something.





    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to jlarkin@highlandsniptechnology.com on Fri Jul 22 16:48:16 2022
    jlarkin@highlandsniptechnology.com wrote:
    On Fri, 22 Jul 2022 12:30:37 +0300, Dimiter_Popoff <dp@tgi-sci.com>
    wrote:

    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter >>>>>>> that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some >>>>>>> piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it >>>>>>> still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>>>> pretty handy. I could probably have done considerably better with >>>>>>> that feedforward trick of Woodward's, where you use another op amp to >>>>>>> measure the error voltage of the main one, and add in its output. >>>>>>>
    Another approach like that is the Kanner Kap, which wasn't first >>>>>>> invented by Kanner, but he now owns it on account of the cute name. >>>>>>> That's the trick where you use an RC lowpass, and drive the cold end >>>>>>> of the cap with some super beefy amplifier to make the top stay still. >>>>>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 >>>>>> Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to >>>>> couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >>>> won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~
    mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7
    20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.
    n

    Well, the PMT has a gain of a million already. ;)

    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Fri Jul 22 16:51:04 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Looks like it's for short circuit protection. A spark across the output
    terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    That is precisely why I do not want to run mine with 800 Volts on the anode.



    Why? It's super easy to protect against. There's no energy involved to
    speak of.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Fri Jul 22 14:24:44 2022
    On Fri, 22 Jul 2022 16:48:16 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    jlarkin@highlandsniptechnology.com wrote:
    On Fri, 22 Jul 2022 12:30:37 +0300, Dimiter_Popoff <dp@tgi-sci.com>
    wrote:

    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com> >>>> wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter >>>>>>>> that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some >>>>>>>> piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it >>>>>>>> still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>>>>> pretty handy. I could probably have done considerably better with >>>>>>>> that feedforward trick of Woodward's, where you use another op amp to >>>>>>>> measure the error voltage of the main one, and add in its output. >>>>>>>>
    Another approach like that is the Kanner Kap, which wasn't first >>>>>>>> invented by Kanner, but he now owns it on account of the cute name. >>>>>>>> That's the trick where you use an RC lowpass, and drive the cold end >>>>>>>> of the cap with some super beefy amplifier to make the top stay still. >>>>>>>>
    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 >>>>>>> Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to >>>>>> couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >>>>> won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~
    mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7
    20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.
    n

    Well, the PMT has a gain of a million already. ;)

    Don't the dynodes wear out after some numbers of coulombs?


    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    I made it to the Louisiana State Science Fair with an alpha
    scintillator, a 931A in a pipe with a bit of glow paint scraped from a
    clock. First Place in Physics! The competition was mediocre.

    The alphas made giant pulses, way above background.

    Next year I made it to the Nationals in Baltimore with a CRT thing.
    Didn't win anything but hung out with Amory Lovins.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Fri Jul 22 23:39:20 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Looks like it's for short circuit protection. A spark across the
    output terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    That is precisely why I do not want to run mine with 800 Volts on the
    anode.



    Why? It's super easy to protect against. There's no energy involved to
    speak of.

    Cheers

    Phil Hobbs

    Personal preference. I don't like the idea of feeding 800 volts into electronics. Caps break down, pc traces arc from moisture or dirt, things
    spark over as you mentioned earlier.

    I'll run my cathode at -800 volts where nothing can be damaged.

    Incidentally, a 10nF cap discharges from 800V to zero in about 50ms.

    People say modern leds are crazy brilliant. I wonder if one will glow at
    90uA to make a safety warning light that high voltage is present.

    People often complain about leds staying lit on leakage currents in wiring,
    but nobody measures the current.





    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to John Larkin on Fri Jul 22 21:05:52 2022
    John Larkin wrote:
    On Fri, 22 Jul 2022 16:48:16 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    jlarkin@highlandsniptechnology.com wrote:
    On Fri, 22 Jul 2022 12:30:37 +0300, Dimiter_Popoff <dp@tgi-sci.com>
    wrote:

    On 7/22/2022 3:17, John Larkin wrote:
    On Thu, 21 Jul 2022 23:53:53 -0000 (UTC), Mike Monett <spamme@not.com> >>>>> wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Yup. Back in the long ago (1984ish), I built a power supply filter >>>>>>>>> that got rid of 10 Vpp of 120 Hz ripple on a 2 kV supply for some >>>>>>>>> piezo stacks. It worked by lifting the cold end, sensing the hot end >>>>>>>>> via a 100 nF, 3 kV film cap, and wiggling the cold end to keep it >>>>>>>>> still. (It had some TVS protection too, obviously.)

    With an LF356 op amp, I got 100 dB of ripple rejection, which came in >>>>>>>>> pretty handy. I could probably have done considerably better with >>>>>>>>> that feedforward trick of Woodward's, where you use another op amp to >>>>>>>>> measure the error voltage of the main one, and add in its output. >>>>>>>>>
    Another approach like that is the Kanner Kap, which wasn't first >>>>>>>>> invented by Kanner, but he now owns it on account of the cute name. >>>>>>>>> That's the trick where you use an RC lowpass, and drive the cold end >>>>>>>>> of the cap with some super beefy amplifier to make the top stay still.

    Cheers

    Phil Hobbs

    The CCFL inverter I got from Amazon runs at 40KHz.

    A simple half-wave rectifier running at 40 KHz with a 1nF cap and 9e6 >>>>>>>> Ohm load will produce about 2V sawtooth ripple.

    This is about 2/800 = 0.0025 * 100 = 0.25% ripple.

    That should be good enough.

    Totally. You can probably use one of the HV caps that came with it to >>>>>>> couple the anode pulses to the outside world.

    Cheers

    Phil Hobbs

    That is a problem. The RH Electronics MCA expects positive pulses. These >>>>>> won't come from the anode.

    https://static.wixstatic.com/media/e43988_a63520f4ed07436a843ddc1be0fda46a~
    mv2.jpg

    https://video.wixstatic.com/video/e43988_8006efb319884c72b9d7f7418abdfa97/7
    20p/mp4/file.mp4

    I shall write them and ask where they get those positive pulses.

    A transformer could invert pulses and take out the HV and the HV
    ripple. You'd need to take out ps ripple for pulse height analysis.


    Never thought of doing it like this but sounds reasonable.
    OTOH for PHA with a scintillator there is not much energy resolution
    to speak of so just about any shaping method you come up with will do.

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.
    n

    Well, the PMT has a gain of a million already. ;)

    Don't the dynodes wear out after some numbers of coulombs?

    About 1000 coulombs per square centimeter of photocathode, give or take.
    They also age out after five years or so because all the volatile
    stuff like caesium metal migrates around inside. If a gamma counter
    gets up to 1000 C/cm**2, I suspect Mike would have other problems. ;)



    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    I made it to the Louisiana State Science Fair with an alpha
    scintillator, a 931A in a pipe with a bit of glow paint scraped from a
    clock. First Place in Physics! The competition was mediocre.

    Fun.


    The alphas made giant pulses, way above background.

    Yup.


    Next year I made it to the Nationals in Baltimore with a CRT thing.
    Didn't win anything but hung out with Amory Lovins.

    Don't know him.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Mike Monett on Sat Jul 23 06:36:16 2022
    Mike Monett <spamme@not.com> wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Why? It's super easy to protect against. There's no energy involved to
    speak of.

    Cheers

    Phil Hobbs

    Personal preference. I don't like the idea of feeding 800 volts into electronics. Caps break down, pc traces arc from moisture or dirt,
    things spark over as you mentioned earlier.

    It doesn't matter which end gets the high voltage. Why take chances by
    putting the high voltage on the anode. It works just as well by putting the voltage on the cathode. I'm not going to be using it long enough to worry
    about ion migration.

    Toyota Principle. Poka-Yoke: Catch mistakes before they occur.



    --
    MRM

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mike Monett@21:1/5 to Phil Hobbs on Sat Jul 23 07:30:37 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    jlarkin@highlandsniptechnology.com wrote:

    [...]

    One could also hang an opamp on the anode to get some gain before AC
    coupling down to ground. A clever circuit would subtract out the power
    supply ripple up there, or couple into a grounded diffamp. There are
    some cheap, low-capacitance dc/dc converters to power the opamp.

    Well, the PMT has a gain of a million already. ;)

    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    Cheers

    Phil Hobbs

    The high sensitivity means the HV supply has to be well regulated.

    One site mentioned the HV has to be adjusted for each PMT to get the
    spectrum lines to align with the corresponding MeV values, which makes
    sense. I suppose the system would have to be recalibrated as the PMT ages.



    --
    MRM

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  • From Mike Monett@21:1/5 to Phil Hobbs on Sat Jul 23 08:14:52 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    Cheers

    Phil Hobbs

    I wonder if that is because of the mechanism of operation, and the large
    number of cascaded sections.

    As I understand it, electrons hit a dynode and eject a number of electrons. These electrons accelerated under the influence of the voltage between electrodes, the same as in the old vacuum tubes. They hit the next
    electrode and eject more electrons. The number of electrons depends on the impact velocity, so the higher the voltage, the more electrons you get.

    This process is repeated for each dynode, so the effect is multiplied each time. This is why the PMT is so sensitive to the applied voltage.

    And this is why it is so difficult to keep the spectrum aligned with the
    known energy levels.




    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From Martin Brown@21:1/5 to Phil Hobbs on Sat Jul 23 09:30:52 2022
    On 22/07/2022 14:07, Phil Hobbs wrote:
    Martin Brown wrote:

    Life improved considerably when they moved onto turbo-molecular pumps
    and for a while performance was improved even more by maglev ones.

    Then one day an earthquake in Tokyo suddenly moved the Earth sideways
    by an inch instantaneously and every damn one of them was destroyed. I
    remember it well since in the quiet of the evening I heard the
    earthquake coming (I have no idea how but I was wondering about the
    strange train like sound outside when the jolt suddenly arrived).

    We were busy doing turbo pump swaps for weeks and after that
    conventional bearings were specified for earthquake zones.

    The maglevs had been out in the field for a couple of years before
    this rather nasty vulnerability became apparent.


    Did any of the casings let go?

    No. By then they had failure modes well under control.

    The only time I have ever known it happen was with a much bigger high
    power early model turbo pump (one of the largest available at the time). Fortunately it failed at lunchtime and there was no-one in the lab. It
    was pumping a big chamber about 1m^3 and something went horribly wrong.
    The academic experimental setup was intrinsically not fail safe.

    It shredded the blackout curtains, imploded the lab windows and doors.
    The bang was heard all over the site and people went running to see what
    had happened. Titanium rotor blades were stuck about 2" into concrete,
    and went through breezeblock walls in a worryingly large kill zone. Some
    were also stuck in the casing walls. Miraculously no-one was harmed.

    The replacement included external Kevlar armour and a host of other
    safety measures to prevent a recurrence from harming experimenters.

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Sat Jul 23 11:58:16 2022
    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    Cheers

    Phil Hobbs

    I wonder if that is because of the mechanism of operation, and the
    large number of cascaded sections.


    As I understand it, electrons hit a dynode and eject a number of
    electrons. These electrons accelerated under the influence of the
    voltage between electrodes, the same as in the old vacuum tubes. They
    hit the next electrode and eject more electrons. The number of
    electrons depends on the impact velocity, so the higher the voltage,
    the more electrons you get.

    This process is repeated for each dynode, so the effect is
    multiplied each time. This is why the PMT is so sensitive to the
    applied voltage.

    Yes, that's right. The secondary yield generally isn't quite
    proportional to the bias per stage, because at higher bias the incident electrons penetrate deeper, so that their secondaries have to make their
    way out through a thicker layer of material on average, and still have
    enough energy to escape when they hit the surface.

    There are negative electron affinity (NEA) photocathodes, where
    essentially any free electron that reaches the surface will escape.
    They have higher quantum yield, as you'd expect, but are also slower
    because it takes awhile for all those low-energy secondaries to bounce
    around before reaching the surface. I'd expect tubes with NEA dynodes
    to follow the power law more closely.


    And this is why it is so difficult to keep the spectrum aligned with
    the known energy levels.

    Well, and the fact that the energy resolution of CsI is the pits
    compared with something like intrinsic germanium. On the plus side,
    it's cheap and doesn't need liquid nitrogen.

    Back in the days before really pure silicon and germanium crystals were available, they used to be "lithium drifted", i.e. lithium interstitials
    were introduced to bind to impurity trap states. Those ones had to be
    kept at 77K continuously, or else they'd be spoiled in a few days.

    Cheers

    Phil Hobbs


    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    i

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Mike Monett on Sat Jul 23 11:59:08 2022
    Mike Monett wrote:
    Mike Monett <spamme@not.com> wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Why? It's super easy to protect against. There's no energy involved to
    speak of.

    Cheers

    Phil Hobbs

    Personal preference. I don't like the idea of feeding 800 volts into
    electronics. Caps break down, pc traces arc from moisture or dirt,
    things spark over as you mentioned earlier.

    It doesn't matter which end gets the high voltage. Why take chances by putting the high voltage on the anode. It works just as well by putting the voltage on the cathode. I'm not going to be using it long enough to worry about ion migration.

    Toyota Principle. Poka-Yoke: Catch mistakes before they occur.



    Provided you can insulate the can from the photocathode.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Sat Jul 23 09:12:52 2022
    On Sat, 23 Jul 2022 08:14:52 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    BTW the gain of a PMT goes as some high power (like 8 or 11 or
    something) of the bias voltage.

    Cheers

    Phil Hobbs

    I wonder if that is because of the mechanism of operation, and the large >number of cascaded sections.

    As I understand it, electrons hit a dynode and eject a number of electrons. >These electrons accelerated under the influence of the voltage between >electrodes, the same as in the old vacuum tubes. They hit the next
    electrode and eject more electrons. The number of electrons depends on the >impact velocity, so the higher the voltage, the more electrons you get.

    This process is repeated for each dynode, so the effect is multiplied each >time. This is why the PMT is so sensitive to the applied voltage.

    And this is why it is so difficult to keep the spectrum aligned with the >known energy levels.

    Add some source with a known narrow line, and servo on that.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Martin Brown on Sat Jul 23 12:40:30 2022
    Martin Brown wrote:
    On 22/07/2022 14:07, Phil Hobbs wrote:
    Martin Brown wrote:

    Life improved considerably when they moved onto turbo-molecular pumps
    and for a while performance was improved even more by maglev ones.

    Then one day an earthquake in Tokyo suddenly moved the Earth sideways
    by an inch instantaneously and every damn one of them was destroyed.
    I remember it well since in the quiet of the evening I heard the
    earthquake coming (I have no idea how but I was wondering about the
    strange train like sound outside when the jolt suddenly arrived).

    We were busy doing turbo pump swaps for weeks and after that
    conventional bearings were specified for earthquake zones.

    The maglevs had been out in the field for a couple of years before
    this rather nasty vulnerability became apparent.


    Did any of the casings let go?

    No. By then they had failure modes well under control.

    The only time I have ever known it happen was with a much bigger high
    power early model turbo pump (one of the largest available at the time). Fortunately it failed at lunchtime and there was no-one in the lab. It
    was pumping a big chamber about 1m^3 and something went horribly wrong.
    The academic experimental setup was intrinsically not fail safe.

    It shredded the blackout curtains, imploded the lab windows and doors.
    The bang was heard all over the site and people went running to see what
    had happened. Titanium rotor blades were stuck about 2" into concrete,
    and went through breezeblock walls in a worryingly large kill zone. Some
    were also stuck in the casing walls. Miraculously no-one was harmed.

    The replacement included external Kevlar armour and a host of other
    safety measures to prevent a recurrence from harming experimenters.

    Yikes.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Dimiter_Popoff@21:1/5 to Martin Brown on Sat Jul 23 21:07:34 2022
    On 7/23/2022 11:30, Martin Brown wrote:
    On 22/07/2022 14:07, Phil Hobbs wrote:
    Martin Brown wrote:

    Life improved considerably when they moved onto turbo-molecular pumps
    and for a while performance was improved even more by maglev ones.

    Then one day an earthquake in Tokyo suddenly moved the Earth sideways
    by an inch instantaneously and every damn one of them was destroyed.
    I remember it well since in the quiet of the evening I heard the
    earthquake coming (I have no idea how but I was wondering about the
    strange train like sound outside when the jolt suddenly arrived).

    We were busy doing turbo pump swaps for weeks and after that
    conventional bearings were specified for earthquake zones.

    The maglevs had been out in the field for a couple of years before
    this rather nasty vulnerability became apparent.


    Did any of the casings let go?

    No. By then they had failure modes well under control.

    The only time I have ever known it happen was with a much bigger high
    power early model turbo pump (one of the largest available at the time). Fortunately it failed at lunchtime and there was no-one in the lab. It
    was pumping a big chamber about 1m^3 and something went horribly wrong.
    The academic experimental setup was intrinsically not fail safe.

    It shredded the blackout curtains, imploded the lab windows and doors.
    The bang was heard all over the site and people went running to see what
    had happened. Titanium rotor blades were stuck about 2" into concrete,
    and went through breezeblock walls in a worryingly large kill zone. Some
    were also stuck in the casing walls. Miraculously no-one was harmed.

    The replacement included external Kevlar armour and a host of other
    safety measures to prevent a recurrence from harming experimenters.


    Whoa! Having no people in the room makes that a fun story, the imploded windows, shredded curtains etc. - hard to match. My closest electronics
    related event compares to that like stumbling in the street to a plane
    crash, I am somewhat envious :).
    [Once, almost 30 years ago, I reversed the power on a new board with
    plenty of tantalum caps which exploded machine-gun like, pretty loud at
    that. Lucy was in the next room and had frozen thinking she might have
    lost me; unfroze with a huge sigh of relief some 10 seconds later when I grasped what had happened and started to chain-swear].

    --- SoupGate-Win32 v1.05
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  • From Mike Monett@21:1/5 to Phil Hobbs on Sat Jul 23 18:31:19 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Cheers

    Phil Hobbs

    Thanks very much for the lucid explanation.



    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From Mike Monett@21:1/5 to Phil Hobbs on Sat Jul 23 18:32:08 2022
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Mike Monett <spamme@not.com> wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Why? It's super easy to protect against. There's no energy involved
    to speak of.

    Cheers

    Phil Hobbs

    Personal preference. I don't like the idea of feeding 800 volts into
    electronics. Caps break down, pc traces arc from moisture or dirt,
    things spark over as you mentioned earlier.

    It doesn't matter which end gets the high voltage. Why take chances by
    putting the high voltage on the anode. It works just as well by putting
    the voltage on the cathode. I'm not going to be using it long enough to
    worry about ion migration.

    Toyota Principle. Poka-Yoke: Catch mistakes before they occur.



    Provided you can insulate the can from the photocathode.

    Cheers

    Phil Hobbs

    I'll find out soon. Thanks



    --
    MRM

    --- SoupGate-Win32 v1.05
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  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Mon Jul 25 18:57:17 2022
    On Fri, 22 Jul 2022 23:39:20 -0000 (UTC), Mike Monett <spamme@not.com>
    wrote:

    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Mike Monett wrote:
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    [...]

    Looks like it's for short circuit protection. A spark across the
    output terminals could be quite unpleasant for T3 otherwise.

    Cheers

    Phil Hobbs

    That is precisely why I do not want to run mine with 800 Volts on the
    anode.



    Why? It's super easy to protect against. There's no energy involved to
    speak of.

    Cheers

    Phil Hobbs

    Personal preference. I don't like the idea of feeding 800 volts into >electronics. Caps break down, pc traces arc from moisture or dirt, things >spark over as you mentioned earlier.

    I'll run my cathode at -800 volts where nothing can be damaged.

    Incidentally, a 10nF cap discharges from 800V to zero in about 50ms.

    People say modern leds are crazy brilliant. I wonder if one will glow at
    90uA to make a safety warning light that high voltage is present.

    People often complain about leds staying lit on leakage currents in wiring, >but nobody measures the current.

    90 uA should be pretty visible into a decent LED. Some are visible in
    room light at 1 uA.

    Here is my high-voltage blinker:

    https://www.dropbox.com/s/53vtce00svlwur4/Blink_1.jpg?raw=1

    It makes bright flashes.

    --- SoupGate-Win32 v1.05
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