GAMBE: Thermal Neutron Detector for Directional Measurement of Neutron Flux

A novel approach for the determination of the direction of a neutron flux is presented. This approach based on the combination of a solid-state neutron capture detector with neutron moderators and reflectors such as high-density polyethylene (HDPE) and lead respectively. This detector has a sandwich configuration of two silicon sensors of 1 cm $^{2}$ active area and a layer of $^{6}$ LiF (1.5 ± 0.6) mg/cm$^{2}$ thick. It has been fixed at the center of an aluminium enclosure (inner dimension 60 mm ×50 mm ×30 mm) for eliminating photoelectric noise. HDPE sheets encircle the entire detector from all directions except one, which faces a 1 Ci Am-Be neutron source where lead blocks 5 cm thick have been used for suppression of gammaray background. Thermal neutron detection efficiency has been estimated according to different setups where the whole system is rotated by an angle of $90 ^{circ}$ in front of Am-Be neutron source. The variation of thermal neutron detection efficiency due to the rotation process provides an evaluation about the location of the utilised neutron source. This location is identified by the maximum thermal neutron detection efficiency, which is achieved and the lowest count rate of gamma-rays where the lead window faces the neutron source. Theoretical investigation using MCNP4C code approved the variation of thermal neutron flux through $^{6}$ LiF film according to the rotational angle.