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: Re: NeutronDetector Guts
Date: Nov 12, 5:40 pm
Poster: Richard Hull

On Nov 12, 5:40 pm, Richard Hull wrote:

>Has anyone opened up their neutron detector and looked at the guts of the preamp? I'd be interested to know if the BF3/He3 tubes used with these detectors operate in the ionization chamber or proportional counter region,(or geiger?), and what sort of preamp and HV regulator circuits they use.

The BF3 uses a very high gain, very fast, low noise preamp. It operates in the proportional region of the gas regime. The high voltge supply must be absolutley noise free (no ripple or hash). You are in effect listening in on a line for a one millivolt pulse that has about 1500 volts on it all the time!

Obviously, the signal is taken off the central electrode using a superior, low value capacitor of 2-3kv rating.

There have been ionization and proportional chambers based on proton recoil and other schemes other than the BF3 used for counting neutrons, but they are for intense flux measurement.

Special fission chambers have been made using U238 coated electrodes for counting fast neutrons.

Good luck in your effort.

Richard Hull

Richard Hull