High-energy resolution spectrometer with proportional counter and Si-detector telescope type for 14 MeV neutrons in plasma diagnostics

A new type of fast neutron spectrometer composed of a CH4 proportional counter and a Si semiconductor detector which is called the counter telescope type was constructed for plasma-temperature diagnostics. The counting gas CH4 is used as a converter of neutrons to protons. Since the energy loss of the proton in the converter CH4 can be fairly precisely measured with the proportional counter, the energy resolution for the proton is high, so that a good energy resolution for neutrons is obtained. The energy resolution of the spectrometer itself excluding the energy spread of the D–T 14 MeV neutrons was 1.7% which seems to be the best so far, and the detection efficiency was 1×10−6. If better energy resolution is preferable, even 0.5% is obtained and the efficiency in this case is 4×10−8.