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AD-25-500 Russian alpha particle detector

Posted: Wed Nov 14, 2018 12:58 pm
by Chris Mullins
In my search for a Canberra PIPS detector, I ran across an ebay listing for AD-25-500 (PDF datasheet here: https://scintillators.ru/datasheet/Alph ... 25-500.pdf) for $250, or for $350 you also get a charge amplifier (the a-CSA: https://scintillators.ru/index_en_products.htm). There's even an online review of it: http://physicsopenlab.org/2018/10/08/al ... od-csa-sa/.

Has anyone run across this before? If it looks legit, I'll get one and try to use it with the Canberra 7401 acquired at the last HEAS, and/or the CSA they also sell.

Re: AD-25-500 Russian alpha particle detector

Posted: Thu Nov 22, 2018 5:07 pm
by Chris Mullins
Well, looks like no one's got any background on it. I'm going to get one, and I'll post any results here. Estimated delivery is January, so it will be a while ....

Re: AD-25-500 Russian alpha particle detector

Posted: Thu Nov 22, 2018 7:24 pm
by Richard Hull
It looks like you will be the pioneer here. Let us know how it goes and what your results are with this unknown.

Richard Hull

Re: AD-25-500 Russian alpha particle detector

Posted: Fri Jan 04, 2019 2:03 am
by Chris Mullins
Well, it arrived (early actually). The ebay seller has been very responsive with some questions I had. I haven't had time to do anything serious with it yet, but I did hook the detector to the CSA/shaper board and fired it up. I taped the detector to a KF25 weld flange to make a small shielded "chamber" that I could place over a radioactive sample. For this quickie test I didn't put it under vacuum.

Alpha detector attached to KF25 flange, uranium ore in the background:
IMG_9577_sm.jpg
CSA board and detector, with ground strap around KF16 flange, 50V bias from 9V batteries
IMG_9578_sm.jpg
Scope shot of pulse shaper (top yellow trace) and raw CSA output (bottom purple trace):
IMG_9579_sm.jpg

I was getting anywhere from 5-20 pulses per minute (no vacuum), depending on how close the uranium was to the detector. Next steps are to put the whole thing under vacuum, then run the output into the Theremino MCA system (https://www.theremino.com/en/downloads/radioactivity).

I have a couple of other radiation sources I can try too. Any other suggestions to fully test it?

Re: AD-25-500 Russian alpha particle detector

Posted: Sun Jan 06, 2019 5:55 pm
by Chris Mullins
I made some more progress exploring the AD-25-500 detector. Now the detector is under vacuum, and to avoid noise problems, I put the entire CSA board in the chamber too. Only power, ground, detector bias, and pulse shaper output go outside the chamber.

CSA board (covered with black tape on both sides, to avoid shorts) on the bottom of the chamber, alpha detector mounted to top of KF25 flange over it):
IMG_9590_sm.jpg
Entire system (roughing pump, chamber, MKS 901p to confirm vacuum):
IMG_9589_sm.jpg
I ran the CSA output into the mic input of my laptop (after attenuating with a 10K pot), and ran the Theremino MCA software, using a fresh Am241 sample. The Am241 (ex-smoke detector) is about 1 inch from the detector. With normal air pressure, the detector gave around 160 counts/minute, with average pulse height around 350 mV. Under 50-100 micron vacuum, I estimate around 55k counts/minute, 1.4V average pulse height. The Theremino software count was much less - it's missing a lot of the pulses, either due to sampling rate issues, the software itself not keeping up, or user error (likely).
am243b.png
The laptop mic input samples at 96 kHz, so it's not really adequate for these pulses. One A/D sample is about the same width as the pulse itself (~15 us). You can see the resulting shape in the Theremino window - it's basically the impulse response of the sound ADC system rather than the original pulse as seen in the scope trace in the last post. But the overall sampled height seems to be roughly proportional, so it's not 100% worthless.

Anyway, still playing around with it, and open to further suggestions! I may try to hotwire the detector into the 7401 NIM alpha spectrometer module I got from Richard at the last HEAS. I don't have a NIM crate to power it up, so I'd have to hotwire that too.

Re: AD-25-500 Russian alpha particle detector

Posted: Sun Jan 06, 2019 8:08 pm
by Richard Hull
Good work, Chris! Work arounds are key to adapting things and getting them to work. Keep up the good work and reporting.

Richard Hull