Semiconductor Fast Neutron Detectors

The application of semiconductor junction detectors to spectroscopy and flux monitoring for fast neutrons is discussed in terms of energy resolution and efficiency. The most useful forms of counter appear to be the proton-recoil and He3 filled detector arrangements, and the construction, performance and applications of such devices are described. A He3 filled detector has given an energy resolution of 150 keV for neutrons of 2-4 MeV with an efficiency approaching 10-5. Measurements are being made of the cross-sections for reactions induced in the silicon of the detectors by fast neutrons, an effect which limits the range of neutron energies for which the counters can be used. Radiation damage to detectors is briefly discussed.