Response of 3He Proportional Neutron Detectors in Mixed Gamma and Neutron Fields

Neutron detectors with various sensitivities are necessary to detect illicit, possibly shielded neutron sources with low neutron fluxes. Under these conditions, detectors will produce low neutron count rates and may be overwhelmed by background gamma radiation. The purpose of the work described here is to demonstrate the gamma-ray response of GE Energy’s Reuter Stokes 3He neutron detectors in mixed neutron and gamma-ray environments representative of a low neutron count rate scenario. The gammaray sensitivity, energy spectra and effect of gamma pile-up are determined for these detectors. The study also demonstrates the benefit of using short time constants for enhanced discrimination against gammarays. 60Co was the primary gamma-ray source.