Characteristics of a new type of spectrometer for measuring intermediate neutrons

A new type of spectrometer for measuring intermediate energy neutrons has been designed for 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