Investigation of enhancement in planar fast neutron detector efficiency with stacked structure using Geant4

Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide (SiC)-based semiconductor fast neutron detector with the stacked structure. A proton recoil detector was simulated, which consists of hydrogenous converter, i.e., high-density polyethylene (HDPE) for generating recoil protons by means of neutron elastic scattering (n, p) reaction and semiconductor material SiC, for generating a detectable electrical signal upon transport of recoil protons through it. SiC is considered in order to overcome the various factors associated with conventional Si-based devices such as operability in a harsh radiation environment, as often encountered in nuclear facilities. Converter layer thickness is optimized by considering 10⁹ neutron events of different monoenergetic neutron sources as well as ²⁴¹Am-Be neutron spectrum. It is found that the optimized thickness for neutron energy range of 1-10 MeV is 400 μm. However, the efficiency of fast neutron detection is estimated to be only 0.112%, which is considered very low for meaningful and reliable detection of neutrons. To overcome this problem, a stacked juxtaposition of converter layer between SiC layers has been analyzed in order to achieve high efficiency. It is noted that a tenfold efficiency improvement has been obtained-1.04% for 10 layers stacked configuration vis-à-vis 0.112% of single converter layer detector. Further simulation of the stacked detector with respect to variable converter thickness has been performed to achieve the efficiency as high as 3.85% with up to 50 stacks. (authors)