Gamma spectrometry using eV CZT and PRA10

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pietkuip
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Re: Gamma spectrometry using eV CZT and PRA10

Post by pietkuip » 25 Jan 2016, 08:25

Nice. I did a test with our AmpTek diode detector if PRA would be able to achieve the resolution. I posted the comparison with the Amptek Pocket MCA a while ago: viewtopic.php?f=14&t=75&p=367#p338
About 1 % in both cases.

But I have not always been able to get this resolution. It depends a bit on what computer or audio-input device I use.
Pieter Kuiper, Växjö (Sweden)
Course lab: 3 mCi neutron source; five 3" NaI(Tl) detectors, CdZnTe detector (Amptek); lead bricks, two GDM 20

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Steven Sesselmann
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Re: Gamma spectrometry using eV CZT and PRA10

Post by Steven Sesselmann » 25 Jan 2016, 13:23

Nice, glad to see you you were able to get some results. It is a while since I experimented with these, but one of the spectra I did was Ba133 and you can see it here. http://www.gammaspectacular.com/gamma_s ... 3-spectrum

PRA is certainly capable of 1% resolution if your detector can do it, because when I calibrate the GS-PRO drivers I no longer use radioactive sources, instead I have built an electronic pulser, which imitates a Cs137 pulse, except it does it so much better, the resulution from the simulator in PRA is 0.5%.

The eV-CZT is microphonic, so much of the baseline disturbances come from sounds in the room, that said, PRA is not susceptible to large baseline movements, as long as the changes in the baseline are on a much longer time scale than the pulse.

I also found with CZT a tendency for the photo peak to be asymmetrical, rising slowly on the left and falling off rather rapidly on the right, this effect can be dramatically improved using the Tolerance Coprrection in PRA, it straightens up the peak and improves the resolution.

Steven

luuk
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Re: Gamma spectrometry using eV CZT and PRA10

Post by luuk » 26 Jan 2016, 06:21

Hallo Alfred,
Nice result you got there,a pity that they are so small!
Groet,
Luuk

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Nephrondoctor
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Re: Gamma spectrometry using eV CZT and PRA10

Post by Nephrondoctor » 26 Jan 2016, 07:25

pietkuip wrote:Nice. I did a test with our AmpTek diode detector if PRA would be able to achieve the resolution. I posted the comparison with the Amptek Pocket MCA a while ago: viewtopic.php?f=14&t=75&p=367#p338
About 1 % in both cases.

But I have not always been able to get this resolution. It depends a bit on what computer or audio-input device I use.
Hi Pieter, very nice resolution of this PIN diode in the low energy range. I tested PRA with an electronic pulse generator and found a resolution better than 1%, and luckily your field test confirms this. Are you aware of PIN diode types which are suitable for hobby gamma spectrometry ?

Regards, Alfred

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Nephrondoctor
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Re: Gamma spectrometry using eV CZT and PRA10

Post by Nephrondoctor » 26 Jan 2016, 07:40

Steven Sesselmann wrote:Nice, glad to see you you were able to get some results. It is a while since I experimented with these, but one of the spectra I did was Ba133 and you can see it here. http://www.gammaspectacular.com/gamma_s ... 3-spectrum

PRA is certainly capable of 1% resolution if your detector can do it, because when I calibrate the GS-PRO drivers I no longer use radioactive sources, instead I have built an electronic pulser, which imitates a Cs137 pulse, except it does it so much better, the resulution from the simulator in PRA is 0.5%.

The eV-CZT is microphonic, so much of the baseline disturbances come from sounds in the room, that said, PRA is not susceptible to large baseline movements, as long as the changes in the baseline are on a much longer time scale than the pulse.

I also found with CZT a tendency for the photo peak to be asymmetrical, rising slowly on the left and falling off rather rapidly on the right, this effect can be dramatically improved using the Tolerance Coprrection in PRA, it straightens up the peak and improves the resolution.

Steven

Hi Steven,

Thanks for your comment. A few years ago I also tested PRA with a pulse generator and found a better than roughly 1% resolution at 662 . With respect to the asymmetry, I had similar findings. I tried tolerance correction but was not able to correct the asymmetry completely.
I will also try higher HV if I can find a more stable HV supply, since the unit nominally wants 500-1000 V HV input. There are several 10 Mohm resistors in series with the crystal. At 160 V HV, I measured around 70 V voltage drop on one of the 10MOhm resistors. Perhaps performance is better at higher HV. The unit handled 900 V without a problem, however, due to lack of stability, baseline fluctuations were more pronounced than at lower HV. Regards, Alfred

pietkuip
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Re: Gamma spectrometry using eV CZT and PRA10

Post by pietkuip » 26 Jan 2016, 09:40

Nephrondoctor wrote:Are you aware of PIN diode types which are suitable for hobby gamma spectrometry ?
It is difficult. I thought I had found something when I saw the spectrum on this page: http://www.carroll-ramsey.com/detect.htm
So I wrote to them and they told me that it had been _very_ difficult to get that spectrum. They made me an offer. Much less expensive than Amptek, but still pricy. And not quite a turnkey system.
Pieter Kuiper, Växjö (Sweden)
Course lab: 3 mCi neutron source; five 3" NaI(Tl) detectors, CdZnTe detector (Amptek); lead bricks, two GDM 20

lodovico
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Re: Gamma spectrometry using eV CZT and PRA10

Post by lodovico » 27 Jan 2016, 18:56

Alfred,
very Interesting the use of the sensor ev CZT. What about the low energy gammas ? Did you try with Americium ?
Lodovico

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Nephrondoctor
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Re: Gamma spectrometry using eV CZT and PRA10

Post by Nephrondoctor » 28 Jan 2016, 01:05

lodovico wrote:Alfred,
very Interesting the use of the sensor ev CZT. What about the low energy gammas ? Did you try with Americium ?
Lodovico
Yes, I tested Am241 too, but I am not sure which files I saved. I am now at work, will look into it this evening. Regards, Alfred

Andrew Seltzman
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Re: Gamma spectrometry using eV CZT and PRA10

Post by Andrew Seltzman » 02 Feb 2016, 07:27

Steven sent me a few of these detectors as well, here is what I'm seeing from Am241 using 100v bias and 9v power. Average of 512 captures

512 averages
am241-good-detector-b2145.png
am241-good-detector-b2145.png (12.91 KiB) Viewed 5788 times
Un-averaged
am241-good-detector-no-avg-b2145.png
am241-good-detector-no-avg-b2145.png (82.16 KiB) Viewed 5788 times
Here is the raw data from the scope capture
am241-czt-9v-100v-good-b2145.zip
(2.91 KiB) Downloaded 154 times

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