Photon and electron beam dosimetry with a CVD diamond detector

The performance of a radiation detector based on a 43 μm thick polycrystalline diamond film, obtained by hot filament CVD has been tested under realistic clinical conditions of irradiation generated by conventional photon and electron beams generally used for radiotherapy purposes. The linearity of the collected charge with the dose was verified and the sensitivity per unit of the detector sensitive volume was evaluated to be 20 nC Gy-1 mm-3 with an applied electric field of 23 kV/cm. This value is of the same order as that reported for PTW natural diamond detectors (50-135 nC Gy-1 mm-3). A correction factor Δ=0.94 was found for the detector current dependence on the dose rate working under the conditions of maximum signal-to-noise ratio. However, even a Δ=1.00 may be obtained when working with higher polarization electric field but at the expense of a lower signal-to-noise ratio. When the diamond detector signals were corrected for the dose rate dependence, the Percentage Depth Signal and the Output Factor values were in agreement with the results obtained with an ionization chamber well within the experimental uncertainty (1% 1σ)