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 mm(3) of detector sensitive volume. A power law with exponent Delta 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. (C) 2002 Elsevier Science B.V. All rights reserved.