Thermal and fast neutron detection through high-purity single-crystal CVD diamonds

Highlights: • Neutron detectors were developed for the detection of thermal and fast neutrons. • The electrode of the diamond plate of the fast neutron detector is 100-nm thick Ag and that of the thermal neutron detector is approximately 5-μm thick Gd. • In test on a cyclotron, the Ag electrode detector measured fast neutrons and gamma rays and Gd electrode detector measured thermal neutron as well as fast neutrons and gamma rays. - Abstract: We developed neutron detectors for detecting thermal and fast neutrons. The sensing element of the neutron detector uses a high-purity chemical-vapor-deposited (CVD) diamond plate, with a size of 3 mm × 3 mm × 0.5 mm, and the ø5 mm detector is sealed for use in the reactor as a small tube by using laser micro welding. The electrodes of the fast and thermal neutron detectors are made up of Ag and Gd with approximately 100-nm and 5 μm thicknesses, respectively. The deposition method of the electrode uses the RF plasma sputtering system. The developed neutron detectors were tested on a 30-MeV cyclotron, which generates fast neutrons and gamma rays. High-density polyethylene plates, Cd plates, and Pb bricks were used for the moderator and shielding. The Ag electrode detector measured the current generated by fast neutrons and gamma rays. Although the sensitivity of the Gd electrode detector is smaller than that of the Ag electrode detector, it measured the current generated by thermal neutrons as well as fast neutrons and gamma rays.