Investigation of the suitability of commercially available CVD diamond for megavoltage X-ray dosimetry

Sandwich-type X-ray detectors were fabricated on commercially available chemical vapour deposition diamond sourced from three manufacturers: Diamond Materials GmbH, Diamonex, and Element Six. These devices were investigated using Raman spectroscopy and 6 MV photons from a clinical linear accelerator. Parameters such as the level of the dark (leakage) current and photocurrent, necessary priming dose, linearity of photocurrent with dose rate, and device sensitivity were considered. Device characteristics vary considerably. Devices fabricated using Diamonex material required high priming doses, and displayed high dark currents, low photocurrents (and hence low X-ray sensitivity), and non-linear dose rate responses. In contrast, devices fabricated from Diamond Materials and Element Six material required lower priming doses, and displayed ‘zero’ dark currents (beyond the detection limit), higher photocurrents, and linear dose rate responses. In addition, the Element Six devices exhibited less variation in response when irradiated at different angles of incidence.