Characterization of the ADII‐33 diamond detector

Abstract

Dosimetry characteristics of the ADII-33 diamond detector were investigated. Sensitivity, stability, bias voltage, hardening, dose rate, energy dependence, and spatial resolution were examined. Current generated in the detector was found to be proportional to the bias voltage applied to the detector with stability degrading as a function of the bias voltage. The average current increased with increasing bias voltage. The statistical fluctuation in current was less than 0.3% regardless of the applied bias voltage. The optimal bias voltage, at which the current uncertainty is negligible, was found to be 125+/-25 V. The detector was hardened up to 85 kGy without significant degradation in output signal. A sub-linearity in the current as a function of dose rate was observed when the dose rate varied from 600.0 to 11.1 cGy/min. A fitting parameter of delta=0.978 was observed in the power relationship of IinfinityDdelta. When comparing the diamond detector readings to corrected ion chamber readings over a wide energy range of electron beams, differences of only 0.2% were observed suggesting no energy dependence for electron beam. PDD curves for a 10 x 10 cm2 field for 6 and 20 MV photon beams measured with the diamond detector and the farmer type ion chamber were also compared and they closely agreed up to a depth of 14 cm. Beyond a depth of 14 cm, diamond detector starts to overestimate the PDD curve reaching difference of 1.90% and 1.0% at 18 cm depth for 6 and 20 MV, respectively, to those values measured with the ion chamber. The diamond detector presents slightly better spatial resolution than the Exradin A16 microchamber. We conclude that at the optimal bias voltage, this new diamond detector is stable and the uncertainties in the current will not affect its suitability for clinical use. If compared against a calibrated ion chamber to correct any energy and dose rate dependence and considering any radiation damage effect, this diamond detector can be used to measure absolute and relative dose.