BF3 Neutron Spark Counter (blind to 500r/hr gammas)

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Mark Rowley
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BF3 Neutron Spark Counter (blind to 500r/hr gammas)

Post by Mark Rowley »

Since neutron detection is paramount when it comes to proving fusion, this old design from 1957 looks quite interesting. Gamma blindness beyond 500r/hr is most impressive. Home construction of the hardware is basic however obtaining BF3 will prove to be difficult if not impossible. Posted mainly for historical appreciation.

In the following pdf, a non-BF3 version using a boron plate appears to have notable gamma blindness as well:
https://fusionforum.net/forum/viewtopic.php?t=692

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Richard Hull
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Re: BF3 Neutron Spark Counter (blind to 500r/hr gammas)

Post by Richard Hull »

BF3 neutron counting systems beat, by an order of magnitude, even the 3He's high gamma immunity. That is why this early neutron detection method is still widely used. Of course, for us, with only 40-80kv x-rays to worry about, power grade reactor, high energy gammas, just are not present at all. Thanks a lot for presenting this very interesting and unusual type of counter to us and me in particular. I thought I had seen them all. I have a made a crude wire type spark wire device for atmospheric alpha detection, and our HEAS fine instrument maker, Tim Raney, has built a superb one in all brass. As most all BF3 neutron counters are at atmosphere or below, this might be an easy build for someone who is willing to work with the highly toxic and poisonous gas. It can be generated chemically in a home lab, but is fraught with many dangers.

With a claimed slow neutron detection efficiency of only 0.6% it would not be worth the effort to construct one as modern BF3 tubes are about 30% or more efficient. for a look at the historical images of BF3 counters check out

https://www.orau.org/health-physics-mus ... index.html

I note the paper was co-authored by Nicholas Anton at Anton laboratories. Anton labs was the LND of its day! They turned out many nuclear detectors for years and had a long running government contract for the manufacture of the famous yellow civil defense GM counters of the 1950s.

Leona Woods, a PhD chemist and friend of Fermi at the University of Chicago actually hand crafted some of the Manhattan project's early BF3 tubes, as well as GM tubes until the project needed them is some quantity as the program expanded and regular manufacture could produce them. We tend to think of just going out and buying GM and neutron detection tubes, but until mid-war in the 1940's, real specialized nuclear researchers were often forced to "roll their own".

https://en.wikipedia.org/wiki/Leona_Woods

I read her book, The Uranium People, about her role in the Manhattan project. A fabulous look at the project from a scientific woman's perspective. I highly recommend it for those of a historical bent on early nuclear work during WWII.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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