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

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)

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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.

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So IEEE is not science body, organization at all

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

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

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....

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

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

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/

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!

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.

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

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

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

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

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

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

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

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

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

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.

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

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

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

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.

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