Simulating the performance of a 3D silicon sensor for neutron detection

Neutron imaging offers additional information compared to X-ray imaging and finds widespread applications in various fields, including nuclear engineering, non-destructive industrial diagnostics, homeland security, archaeology, and cultural heritage preservation. Drawing on extensive expertise in 3D sensor technology, a 3D micro-structured sensor for thermal neutron detection and imaging is under study. These devices, named HYDE2, are crafted through a simplified fabrication process, featuring planar n-on-p pixels on the front side. On the back side, Deep Reactive Ion Etching selectively etches deep and narrow cavities, subsequently filled with appropriate converting materials such as 6LiF or 10B. The sensor is composed of 256x256 pixels of 55x55 μm2 size and is coupled with a Timepix read-out chip. In this work, GEANT4 simulations were conducted to investigate the thermal neutron absorption and conversion into charged particles, considering different geometries of the cavities and different conversion materials. Using Synopsys TCAD, the electric field map inside the sensor was determined, and aspects of charge generation, diffusion, and collection-which can degrade efficiency and diminish imaging performance due to charge loss and charge sharing events-were considered. This paper presents the primary outcomes of Monte Carlo and TCAD simulations, providing a more accurate estimate of the detection performance with this sensor type. These findings can prove highly beneficial for future research and the development of innovative 3D silicon detectors for neutron imaging.