Development of a portable high-energy neutron spectrometer

The design of a portable high-energy (20–800 MeV) neutron spectrometer based on CsI or BaF2 is described. The particle discrimination properties of these scintillators allow the light-ion spallation products (p, d, t and α) from neutron interactions to be identified uniquely. One or more of the resulting pulse-height spectra can be unfolded to reveal the incident neutron spectrum. Dosimetric quantities can then be calculated based on the unfolded spectrum. Due to the high stopping power of these scintillators, modest-sized crystals are suitable for this application. Combined with advances in electronics, a lightweight instrument capable of on-line particle discrimination with a real-time display of neutron-induced count rate is feasible. Preliminary experimental data are presented, and the importance of validating MCNPX-generated response functions is discussed. A brief discussion on future work follows.