Reproduction of neutron fluence by unfolding method with an NE213 scintillator

The reproduction of neutron fluence derived by the unfolding method was confirmed by simulating an experiment at Cern High energy AcceleRator Mixed field facility (CHARM). Fluences on an NE213 scintillator located at positions surrounded with shields were calculated using PHITS. A neutron light output spectrum and response matrix were calculated according to the calculated fluence. Furthermore, response matrices with simple distributions of neutron incident position and direction on the scintillator were also prepared because a response matrix with guessed distributions is used in measurements. In spite of using response matrices with different distributions, the unfolded fluence agreed with each other, unless the distribution was focused on a position. The agreement of the fluences enables us to measure the fluence at various positions even though the distributions are experimentally unknown. Finally, experimental fluences were obtained under the same conditions, and were compared with the simulation results.