Discriminating neutron peaks from electrical noise peaks

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Post Reply
Dan Knapp
Posts: 341
Joined: Wed Aug 06, 2008 12:34 pm
Real name: Dan Knapp

Discriminating neutron peaks from electrical noise peaks

Post by Dan Knapp » Mon Jan 13, 2020 6:51 pm

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.

User avatar
Richard Hull
Moderator
Posts: 12184
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Discriminating neutron peaks from electrical noise peaks

Post by Richard Hull » Tue Jan 14, 2020 2:06 am

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
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Dan Knapp
Posts: 341
Joined: Wed Aug 06, 2008 12:34 pm
Real name: Dan Knapp

Re: Discriminating neutron peaks from electrical noise peaks

Post by Dan Knapp » Tue Jan 14, 2020 5:00 pm

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.

User avatar
Richard Hull
Moderator
Posts: 12184
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Discriminating neutron peaks from electrical noise peaks

Post by Richard Hull » Tue Jan 14, 2020 5:29 pm

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
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Post Reply