Simulation studies for optimization of geometrical parameters of 3D neutron detectors

There is an increased demand of neutron detectors for security applications requiring detection of special nuclear materials (SNMs) to prevent proliferation and illegitimate trafficking, for monitoring neutron beams, etc. Commonly, ³He and BF₃ gas detectors are being used for such applications due their high efficiencies. However, these detectors suffer from certain issues such as global shortage of ³He, toxicity of BF₃, portability, etc.. Therefore, in recent years, there has been a significant interest in the development of semiconductor based, mainly silicon based thermal neutron detectors as an alternative to these gas filled detectors. Silicon detectors have advantages of compactness, low operating voltage requirement and low cost due to well established fabrication technology and possibility of large-scale production. Simulation results as presented in this work, show that for Type II structure, there is no significant increase of neutron detection efficiency as the trench cross section is reduced. Compared to Type II structure, Type I structure has more efficiency. In this structure, significant increase in the efficiency can be obtained by reducing the cross section of pillars. Based on these simulation studies and fabrication process limitations, a few designs have been finalized for the fabrication of 3D thermal neutron detectors