Semiconductor Counters

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Semiconductor Counters

Post by teslapark » Mon Jul 23, 2001 10:14 pm

I'll do my best to explain this, as I just read about it myself.

In chapter 4 of a book entitled: "Progress in Fast Neutron Physics" (Philips, Marion, Risser) a device is described that counts fast neutrons with a semiconductor junction.

Instread of garbling the info in my own words, I will quote a few lines:

"The simplest adaptation of a semiconductor juntion counter to the detection of fast neutrons is to mount on the face of it a thin hydrogenous radiator, such as polyethylene, from which recoil protons may enter the counter with a 2pi geometry. Since all the protons can be recorded and the cross section is high, the efficiency of such as system may be relatively large, on the order of 10e-3."

"For neutron flux measurement this method has certain advantages. The proton recoil cross section is well known over a wide reange of neutron energies, the thickness of the hydrogenous foil and its constitution can be accurately measured, and, since the geometry is will defined, and absolute neutron flix count can be made."

It also mentions how this device is very small and can be placed close the the flux source and very little scattering of the neutron flux is encountered.

This counter is not expected to receive damage below 10e11 fast neutrons/cm3 integrated dose.

There are also neutron reactions (n,p) (n,alpha) that can take place in the silicon itself, and that background must be corrected.

Si28 seems to be the most common isotope for this type of counter. Anyone else heard of this?

Adam Parker

Tom Dressel
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Re: Semiconductor Counters

Post by Tom Dressel » Tue Jul 24, 2001 1:51 am

Go to The info is on the SLAC lectures section.

Tom Dressel


Re: Semiconductor Counters

Post by guest » Tue Jul 24, 2001 2:43 am

If you don't mind introducing the detector to vacuum, you can count the proton yield from the D-D reaction directly with a semiconductor detector and get both efficiency and energy resolution, This is what the folks ay U. Wisconsin do. This approach has also been discussed here before.

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Richard Hull
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Re: Semiconductor Counters

Post by Richard Hull » Tue Jul 24, 2001 3:10 pm

Before getting too excited, that 10e-3 efficiency is one in 1000 neuts counted. The BC720 bicron scintillator counts 1 in 144 and the average BF3 tube in a good moderator can count 1 in 100.

The semiconductor doesn't sound all that good as presented by Marion, who, by the way, is the Author of the superb two volume set "Fast Neutron Physics"

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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