High temperature operation of single crystal diamond detectors

Diamond is studied since many years as potential radiation detector material. In the last years, there has been an increasing interest about the capability of diamond to withstand harsh working conditions including high temperature. The latter capability depending upon the large band gap and the excellent thermal properties of diamond. At ENEA C.R. Frascati, diamond detectors operating at high temperature are studied since many years as candidate neutron monitors for nuclear fusion reactors. Diamond metallization was realized using different metals deposited on commercial diamond films, 100 or 500 μm thick. This paper reports the results for two detectors made with metal Cr and Ag contacts, respectively. The maximum working temperature under 14 MeV neutron irradiation, while operating the detector in spectrometric mode, was in the range 220-240 °C. The best performance was obtained using Ag metal contacts. It was also observed that once cooled down below the maximum working temperature the detector performances are recovered. Furthermore, it was observed that metallization can be damaged after long lasting operation at high temperature. In the attempt to overcame this issue a new detector was realized made with one Schottky Cr-diamond metal contact on one side and an ohmic, not metallic, contact on the other side. A commercial film 100 micron thick was used. This detector shown excellent performances well above 300°C.