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 13, 7:39 pm
Poster: Richard HesterOn Nov 13, 7:39 pm, Richard Hester wrote:
I intend to try detecting protons from the D-D reaction. I have a semiconductor detector that might make the nut, but an alternative could be an ionzation or proportional counter. Protons are as good as alphas at ionizing the matter they hit(maybe better, as they have a higher charge to mass ratio). If the electrons are deflected away from the detector uing a magnetic field, a relatively short ionization/proportional counter should be able to differentiate via pulse height between background x-rays (relatively low ionization efficiency) and high energy protons. A multichannel analyzer should be able to sort out the relative energies, and a single channel device may be all that is necessary.
Since one is looking for ionization events (very likely if the proton gets into the chamber) instead of a boron-neutron reaction or a proton recoil that may or may not occur, the detection efficiency should be fairly high.
There is not a lot of information around on detecting protons at a few MeV, since almost all radionucleides would rather spit out anything but a proton. That leaves the accelerator people, who are generally looking at much higher energies, and folks like us....
Richard Hester
>>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.
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>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!
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>Obviously, the signal is taken off the central electrode using a superior, low value capacitor of 2-3kv rating.
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>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.
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>Special fission chambers have been made using U238 coated electrodes for counting fast neutrons.
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>Good luck in your effort.
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>Richard Hull
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>Richard Hull
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