Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector

The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a ²⁵²Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10^?4, whereas three-fold greater efficiency was obtained for a ²⁴¹AmBe neutron spectrum.