Characteristics of a new type of spectrometer for measuring intermediate neutrons

A new type of spectrometer for measuring intermediate energy neutrons has been designed to exclude contributions by unwanted γ-rays. The detector assembly consists of a H₂ gas proportional counter surrounded by six ³He gas proportional counters. The spectrometer is operated in principle by using successive double pulses produced by a proton recoil in the inner H₂ counter at first and then by a neutron capture in one of the outer counters. The response function, the energy distribution of scattered neutrons coming into the ³He counters and the time distribution between the proton recoil and the neutron capture were calculated by using the modified NRESP Monte Carlo code. The results showed that the response has a characteristic peak corresponding to the incident neutron energy. The double pulse measuring technique will provide excellent features relevant to the measurement of intermediate neutrons existing together with γ-rays