Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: New neutron counter
Date: Sep 13, 10:51 am
Poster: Richard Hull

On Sep 13, 10:51 am, Richard Hull wrote:


I just recently picked up a nice, new, inbox, Hammatsu, 10 stage, 5" photomultiplier tube! This was a real find indeed.

I need a neutron counter with a bit more sensitivity which will defeat the low end barrier a bit more. This new system should allow a low end, minimum count of 1000 neutrons per second to come into view with statistical certainty.

The tube cost me $50.00, but the required 5" diameter Bicron BC-720 scintillator just flattened me for about $475.00! Ouch again!.....But, hey, you can't take money to the grave with you!

While it is on order, (about an 8 Week lead time as it is made up), I am working on the dynode string and preamp, and finally, the special housing that will be required.

For those interested, the 5" diameter detection volume placed against a fusor will intercept a great deal more neutrons sending the statistical data into new regions, where only noise existed before.

Of all nuclear radiations, fast neutrons are the most difficult and costly to detect. As I have said before, it is really an art.

Rolling one's own neutron counter is not for the beginner in electronics. Non-electronics types must usually do without. Knoll's book on radiation detection is one of the best references I have on the subject. Too bad it is out of print.

I had once held the illusion of using Indium foil and neutron activation to get at the count rate for a non-electronic solution, but the flux is so low from the low end amateur fusor that such methods would demand even more sophisticated and costly instruments than a full blown neutron detector. The indium foil, even then, might only offer a crude order of magnitude idea about the neutron yield.

Richard Hull