UC Berkeley

The neutron flux of three neutron beam experiments was measured using a novel neutron spectrometer system, referred to as a Scatter Time-of-Flight (STOF) spectrometer. The neutron beam was generated via the nuclear breakup of 14 and 23 MeV deuteron beams on a thick natural carbon target at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). The system is shown to be capable of measuring the energy-dependent neutron flux on a per-experiment basis. Furthermore, the resulting neutron flux was unfolded using experimentally determined activation foil reaction rates and a maximum entropy spectral unfolding algorithm. The spectrum unfolding was needed to determine the STOF efficiency as a function of neutron energy. The modular nature of the system allows for it to work in low and high-intensity fluxes, broad energy ranges, and various experimental configurations. The STOF spectrometer, in conjunction with activation foils and spectral unfolding techniques, provides a powerful, high-efficiency capability to noninvasively monitor neutron spectra at experimental facilities like GENESIS where a high beam repetition rate makes traditional time-of-flight techniques not possible due to knowledge of the appropriate start time.