Neutron detection using large area silicon detectors

We present large-area silicon detectors for neutron detection. To detect neutrons, the silicon is coated with a thin reactive layer, such as 10B or 6Li, which has a high probability of interacting with incident thermal neutrons. Each neutron interaction in the reactive layer results in an alpha particle to be detected by the semiconductor, plus a recoil nucleus. A large-area thermal neutron detector of this type was recently constructed at the Naval Research Laboratory by coating a 9.5 cm×9.5 cm, 0.5 mm thick silicon strip detector with a thin (1.5 μm) layer of 10B. This device was used to detect the 1.47 and 1.78 MeV alpha particles that result from the interaction of incident thermal neutrons with 10B. The device also detected tritons when coated with 6LiF. This has prompted the development of a custom large-area thermal neutron detector. This design is fabricated using Silicon-on-Insulator (SOI) wafers, potentially enabling low-cost and high-volume manufacture of the detector arrays. Furthermore, the SOI technology allows for thinner (7 μm) silicon layers that significantly reduce the instrumentʹs sensitivity to gamma ray backgrounds.