Monte Carlo simulations of a microstructured silicon detector with high efficiency for thermal neutrons

In this work we present a design optimization of a high efficiency neutron detector with MCNPX simulations. The detector is based on a silicon structure incorporating a boron-based converter to detect thermal neutrons by means of the super(10)B(n, alpha ) super(7)Li nuclear reaction. In order to improve the efficiency of planar detectors, limited to 5%, we have designed a perforated detector based on microstructures etched inside the silicon bulk, which would considerably increase this value. Each one of these microstructures is a micro-channel filled with the converter that provides a high surface-volume contact ratio between the converter and the sensitive silicon bulk. The main parameters optimized with the simulations are micro-channel width and depth, width of the silicon wall between micro-channels, and converter density, all comprised within technologically viable ranges. The results show that the detector could achieve up to 50% thermal neutron efficiency for a realistic prototype that can be produced with MEMS fabrication techniques.