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Discriminating neutron peaks from electrical noise peaks

Posted: Mon Jan 13, 2020 6:51 pm
by Dan Knapp
As discussed here previously, and in my own experience as well, counting neutrons using a Helium-3 detector is fraught with difficulty due to electrical pulses from arcing in a fusor. There are sophisticated methods to do peak discrimination, but I just came across a clever solution that makes use of the pulse width triggering capability of a digital oscilloscope. I was reading a recent thesis from Khachan’s group in Sydney by Richard Bowden-Reid (https://ses.library.usyd.edu.au/handle/2123/21070) and noted that he connected his preamp output to a Rigol 1074Z oscilloscope set to trigger on pulses 2-5 microseconds in duration. He then simply connected a digital counter to the oscilloscope’s TTL trigger output to count neutrons. I was excited to try this until I discovered my Tektronix scope does not have a TTL trigger output. Given that Chinese digital scopes are available at very good prices, it could be worth buying one solely for this function.

Re: Discriminating neutron peaks from electrical noise peaks

Posted: Tue Jan 14, 2020 2:06 am
by Richard Hull
True, trigger gate outputs are not common on most scopes. There are NIM modules that can discriminate on windowed pulse width's. Some few spectrometer amp NIM modules combine pulse height discrimination with pulse width discrimination.

Richard Hull

Re: Discriminating neutron peaks from electrical noise peaks

Posted: Tue Jan 14, 2020 5:00 pm
by Dan Knapp
Richard, do you know a specific model number NIM module that will do pulse width detection? I am not familiar with one that has this specific function.

Re: Discriminating neutron peaks from electrical noise peaks

Posted: Tue Jan 14, 2020 5:29 pm
by Richard Hull
I have seen them in NIM bins in labs and chatted with one specific user about them. I think I may have one. Let me check my stock of modules. I'll get back with you.

Richard Hull