A layered 6Li foil multi-wire proportional counter

The shortage of ³He gas for neutron detection has led to alternative technologies for large-area high-efficiency neutron detectors. Large area sheets of ⁶Li foils covering more than 625 cm² were positioned 1.6 cm apart in a multi-wire proportional counter each with an anode wire bank positioned on each side of the absorber sheet. The intrinsic neutron detection efficiency was measured at P-10 pressures of 1.1,1.5,2.0, and 2.8 atm, using ²⁵²Cf as the neutron source, and was calculated to be approximately 18% at all pressures. Additionally, the intrinsic thermal neutron detection efficiency was measured to be greater than 50% for a detector with four ⁶Li foil layers. The gamma-ray sensitivity, measured with the same gas pressures, was determined with a ¹³⁷CS source positioned at a distance to yield an average field strength of 60 mRlhr. The relatively high gamma-ray exposure rate had minimal impact on the neutron measurements, as evidenced from the pulse-height spectra.