NEUTRON DAMAGE OF CVD DIAMOND

CVD diamond is being evaluated for the vertex detectors in the Large H adron Collider. At the positions where diamond detectors would be loca ted, the dose of high energy particles is expected to be equivalent to 10(15) cm(-2) 1-MeV neutrons year(-1). Three diamond films have been irradiated with 6 x 10(15) neutrons cm(-2). Before and after the full dose of irradiation, their cathodoluminescence and absorption spectra were recorded. The resistivity and the signal detected due to minimum ionising beta particles was measured before and after irradiation and at five intermediate doses. We estimated the concentration of vacancie s from the absorption spectra. The production rate for single neutral vacancies was about 0.5 per neutron cm(-1). The signal detected when a minimum ionising beta passes through the diamonds increases with dose by about 40% after 10(15) neutrons cm(-2). It decreases to below its initial value after the final dose. These results show definitively th at CVD diamond detectors will operate with little degradation for 10 y ears in the high radiation zones of the Large Hadron Collider. (C) 199 7 Elsevier Science S.A.