Production and testing of a synthetic diamond film radiation dosimeter for radiotherapy

A detector, constituted by a polycrystalline chemical vapor deposited diamond film, has been made for on-line radiotherapy beam analysis in terms of dose distributions in water equivalent material. Preliminary results are reported which evidence that the leakage current can be a limiting parameter for an efficient collection of the charge carriers produced by the ionizing radiation. A signal to noise ratio near to 100 has been obtained. A priming effect similar to that found in natural diamond devices has also been evidenced, and a stable detector response was obtained after an accumulated dose of 5 Gy. The linearity has been achieved between the detector reading and the dose. The detector sensitivity resulted was equal to 77 nC/Gy per mm3 of detector sensitive volume. A power law with exponent Δ less than one has been found between detector reading and dose rate. However, when the dose rate dependence was corrected, the percentage depth doses, along an X-ray beam central axis, was in agreement with those obtained by an ionization chamber.