Characterization of 14 MeV Neutron Detectors made with Polycrystalline CVD Diamond Films

Polycrystalline chemical vapor deposited (CVD) diamond detectors are of great interest in harsh environments due to their capability to operate even at high temperature and to withstand great neutron fluencies. Their use is of interest in many fields including the nuclear fusion reactors. In this paper the successful characterization of polycrystalline CVD diamond detectors as 14 MeV neutron monitors is reported. Two polycrystalline CVD diamond detectors of 96 mum and 126 mum thickness respectively were used. The detectors´ count rate versus neutron flux was studied for various applied electric fields, showing that these detectors have a linear behavior in the flux range explored. The detector efficiency was also derived resulting in stable behavior vs. the neutron flux. The low sensitivity to gamma-ray field and the possibility to reject the counts due to gamma-rays was also assessed. The time dependent neutron emission from the 14 MeV Frascati Neutron Generator (FNG) was recorded with CVD diamond detectors. The data for diamonds were compared with that recorded by the standard monitors available at FNG showing good agreement. Good stability and capability to operate (with negligible pile-up effect) with neutron flux up to 3times10⁸ n cm^-2 s^-1 was observed. Following this characterization one diamond detector was installed at JET and successfully operated during the trace tritium experiment campaign as a flux monitor of the 14 MeV neutron emission from JET