Thermal neutron detector for mixed neutron and gamma beams using a commercial, boron-coated, CMOS image sensor

We present the detection of thermal neutrons using a Back Side Illuminated CMOS image sensor covered with a converter layer of sodium borate with a thickness of (20±5) μm. Events caused by neutrons are distinguished from events caused by gamma photons by a charge threshold and geometrical considerations. The detector was irradiated in the BNCT radial beam of the RA6 reactor to prove its potential use in mixed neutron-gamma beams.