On neutron detection with silicon carbide and its resistance to large accumulated fluence

Within the framework of the ENTER_BNCT INFN project, commercially available silicon carbide sensors with 1 mm(2) area were made sensitive to thermal neutrons. Two different thermal neutron radiators were exploited, leading to different measurement sensitivities and degrees of radiation resistance: (1) a 6LiF coating on the sensor or (2) the air volume between the sensor surface and the walls of the package. Thermal neutron sensitivity and radiation resistance were assessed in the well-controlled thermal neutron beam produced in the thermal column of the TRIGA reactor at LENA Pavia. The sensors were connected to a nuclear spectroscopy system and irradiated up to an accumulated fluence of 5.6x10(13) cm(-2) distributed in nine steps, ranging from 1012 cm(-2) to 1013 cm(-2) each, with the reactor operating at the maximum power of 250 kW. After each damaging step, the reactor power was lowered to 100 W, and the pulse height distribution of the detectors was recorded. This allowed to observe the effects of the progressive damage by inspecting the puls e height distribution. These effects were evident in the (LiF)-Li-6-coated detector and fairly observable in the air-type one. To interpret the spectra, a specific Monte Carlo code was written to model the neutron interaction in both detectors, achieving very satisfactory agreement with the experiment.