Semi-insulating GaAs detectors with HDPE layer for detection of fast neutrons from D–T nuclear reaction

Abstract

Bulk semi-insulating (SI) GaAs detectors optimized for fast-neutron detection were examined using mono-energetic neutrons. The detectors have an active area of 7.36 mm 2 defined by a multipixel structure of a AuZn Schottky contact allowing a relatively high breakdown voltage (300 V) sufficient for full depletion of the detector structure. The Schottky contact is covered by a HDPE (high density polyethylene) conversion layer, where neutrons transfer their kinetic energy to hydrogen atoms through elastic nuclear collisions. The detectors were exposed to mono-energetic neutrons generated by a deuterium (D)-tritium (T) nuclear reaction at a Van A. Sagatova et al. 1660233-2Neutrons reached a kinetic energy of 16.8 MeV when deuterons were accelerated by 1 MV potential. The influence of the HDPE layer thickness on the detection efficiency of the fast neutrons was studied. The thickness of the conversion layer varied from 50 μm to 1300 μm. The increase of the HDPE layer thickness led to a higher detection efficiency due to higher conversion efficiency of the HDPE layer. The effect of the active detector thickness modified by the detector reverse bias voltage on the detection efficiency was also evaluated. By increasing the detector reverse voltage, the detector active volume expands to the depth and also to the sides, slightly increasing the neutron detection efficiency.

Semi-insulating GaAs based detector of fast neutrons produced by D–T nuclear reaction

“…However, the 239 Pu-Be neutron source is also a source of gamma-rays, which might have affected the results. Later, in [11] we have tested the same type of GaAs detectors by 16.755 MeV neutrons from deuterium -tritium nuclear reaction, using HDPE conversion layers of various thicknesses in the range from 50 to 1300 µm. The experimental detection efficiency was increasing with the thickness of HDPE layer from 0.03% up to 0.24%.…”