Development of neutron detector using the surface barrier sensor with polyethylene (n, p) and B-10 (n,alpha) converters

A Si semiconductor detector, surface barrier type, with a slim film of a co nverter material, capable to produce charged particles, was used as a senso r of neutrons to be used in an environment of a zero power reactor. Two typ es of converters were used to improve the detection efficiency: (1) polyeth ylene. n(CH2), which produces recoil protons from the (n.p) interaction and , (2) B-10 which generates ex particles from the (n,cx) reaction. The optim al thickness of these converters was determined experimentally. Specificall y for the polyethylene, a mathematical model was developed to fit the exper imental data. For an AmBe source the optimum polyethylene converter thickne ss was of 5.8 x 10(-2) cm (61.64 mg cm(-2)), while for the B-10 it was equa l to 6.55 x 10(-4) cm (1.54 mg cm(-2)). The converters of polyethylene and B-10 improved the detection efficiency to a factor of 4.7 and 3.0, respecti vely, compared to measurements without converter. Comparing the three spect ra of the background radiation, the polyethylene recoil protons and the B-1 0 alpha radiation, it was concluded that the polyethylene presented better performance than the B-10 converter. (C) 2001 Elsevier Science B.V. All rig hts reserved.