Monte Carlo simulation of gamma-ray response functions for a proportional counter used for neutron measurement

It is often required in neutron calibration fields to determine the dose of gamma-rays produced in a neutron source and in the surroundings, because s ome neutron detectors are sensitive both to neutrons and gamma-rays. As a f irst step estimating neutron and gamma-ray energy spectra and fluences simu ltaneously in a neutron field, the gamma-ray response function for a He-3 p roportional counter was calculated using EGS4/PRESTA code. In the simulatio n, the gas multiplication factor, which depends on the detection position i n the gas region along an anode wire, was taken into account to obtain the precise response function. For comparison, we measured response functions u sing different reference gamma-ray sources such as Am-241, Cs-137, and Co-6 0, which were located vertically 55 mm away from the center of the anode wi re. Calculated response functions agreed well with experimental ones. Monte Carlo code EGS4 is thus useful for the simulation of gamma response functi ons for neutron counters. (C) 2000 Elsevier Science Ltd. All rights reserve d.