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: Re: Fusion detection
Date: Dec 26, 9:55 am
Poster: Richard Hull
On Dec 26, 9:55 am, Richard Hull wrote:
Actually the protons you are looking for in the cloud chamber, are those produced just at the back edge of the block. The mean free path of protns in the plastic is measured in a fraction of a mm.
The bulk of the plastic moderates the neutrons a bit and once moderated, the proton recoil rate increases dramatically.
As it turns out the BC-720 is ideally designed and honed after years of study and upgrading. Bicron did not invent the process, but purchased it from a competitor.
The bad part about the proton recoil in plastics is that without calibration and constants of production, (read efficiency), the thing is only a test of neutron production, with no meaningful data available.
Again, the idea of using common BC-100 plastic coupled to normal plastic is that the detection is limited to the virtual junction of the two pieces. Add to this the fact that the remainder of the BC-100 scintillator is now sensitive to gamma and other particles (which the BC-720 is not), and you will play hell trying to sort things out.
The BC-100 in thick slabs will detect neuts just fine, but the noise window to all paticles is wide open and would be like two orders of magnitude above the BC-720. The BC-720 is also about one order of magnitude higher in light output due to the (Ag)ZnS internal structure.
With very low neutron production in amateur devices, the BC-100 would be all noise and no signal.
P.S. I have tried it! I immediately purcahsed the BC-720 and never looked back.
Oh, I would leave the detector outside the chamber. The neuts we are making will no be attenuated one Iota, by the .060 or even 0.10 walls. According to two of my neutron physics texts. 6" of solid steel will stop less than half of the neuts at 2-3mev. The walls will indeed stop 100% of the electrons, deuerons, and other charged particles nicely. I place my detector just on the outside wall with about 1/2" airspace to avoid the wall heat during operation. BF3 tubes are really sensitive to delta temps, that is why I shun them.
- Re: Fusion detection - Tom Ligon Dec 27, 11:28 pm