Electrical and dosimetric characterization of a CVD diamond detector with high sensitivity

A prototype detector has been built using commercial high quality single crystal epitaxial diamond and novel electrical contacts resulting in two asymmetric Schottky junctions able to operate the detector at zero bias like a photodiode. Aiming at evaluating the detector suitability for radiotherapy applications we report on results related to signal dynamics, linearity with the dose and dose rate, signal stability and measurement repeatability determined in a Co-60 reference beam. In addition, we measured the detector sensitivity and its dependence on the applied bias voltage. The detector has a wide active volume leading to high current signal values. The signal dynamics is wide, with a dark current of 3.2 10 14 A at zero bias and a current of 6.8 1010 A under irradiation with a dose rate of 0.95 Gy min1. The sensitivity to ionizing radiation increases with the bias voltage and values up to 104 nC Gy1 mm3 have been evaluated at 300 V. When operated at 5 V, the detector shows a linear response on a wide range of Co-60 dose rates from 1.3 103 Gy min1 to 1.2 Gy min1 following the Fowler’s power law with a coefficient D ¼ 0.99 0.01. The device also shows rise and fall times of less than 1.0 s with a stability of the signal under irradiation better than 0.3%. The characteristics of the detector, as determined in the Co- 60 beam, appear suitable for radiotherapy dosimetry,