The effect of fast neutron irradiation on the performance of synthetic single crystal diamond particle detectors

Abstract

Diamond is known for its extreme hardness which may allow it to operate as a particle detector in high fluence environments even after absorption of large radiation doses. We present a study of the deterioration of the charge collection efficiency ( CCE) due to neutrons produced by 235U fission, with irradiation fluences up to 1 × 10 16 n cm − 2. The planar devices were fabricated by thermal evaporation of Au onto approx. 300 μm thick high purity chemical vapour deposited diamond produced by Element Six Ltd., UK. The detector performance was investigated as a function of bias voltage at room temperature using 241Am α-particles and minimum ionising particles (MIPs) of a 90Sr source. At low fluences up to 2 × 10 13 n cm − 2 , the detectors reach the initial saturated signal amplitude after irradiation. However, the signal is less stable and deteriorates due to polarisation. This effect can be reduced by initial priming with X-rays. No peak could be distinguished in the detector response in the unprimed state after 10 16 n cm − 2 with bias voltages up to 1000 V (equivalent to 32 kV cm − 1). However, a peak at about 18% CCE could be recovered after priming.