CVD diamond for thermoluminescence dosimetry: optimisation of the readout process and application

Abstract

Diamond is known to be an extremely attractive material for dosimetry applications due to its intrinsic properties: tissue equivalence, physically robust, chemically inert and safe for in vivo use. Polycrystalline diamond substrates exhibit defective levels which trapped population is of major importance for the fabrication of radiation detectors based on diamond ionisation chambers or thermoluminescent dosimeter. The thermoluminescence (TL) is based on the measurement of the population that has been trapped during irradiation. Several problems however have been reported, namely fading of the TL signal when the device is exposed to light, poor linearity with respect to the absorbed dose and often poor reproducibility of the measurements. To address this we have set up a technique that enables irradiation and sample probing in the same apparatus. Irradiation was performed using an X-ray source with 50 kV accelerating voltage. Simultaneous measurements of TL and thermally stimulated currents (TSC) were performed. This way the fine control of the parameters (including temporal aspects) known to affect the reproducibility of the measurement could be varied, and a procedure for improving the linearity factor (TL signal with respect to the dose) of the diamond TL detectors was optimised. The technique was implemented on a set of CVD films to compare in a reproducible way the material properties according to their growth characteristics. (C) 2003 Elsevier B.V. All rights reserved.