S. Gastélum

Dose rate effects on the thermoluminescence properties of MWCVD diamond films

Synthetic CVD diamond, being non-toxic and tissue equivalent, has been proposed as a ionizing radiation passive dosimeter with relevant applications in radiotherapy and clinical dosimetry. In the present work, the thermoluminescence (TL) properties of microwave-assisted chemical vapor deposition (MWCVD) diamond, 6 μm thick film grown on (100) silicon substrates, were studied after room temperature γ-irradiation for 2.4, 3.1, 5.94, 13.1, 20.67, 43.4 and 81.11 Gy min−1 dose rates in the range of 0.05–10 kGy. At fixed irradiation dose the TL efficiency increases as the dose rate increases. As the dose increases the peak temperature at the maximum intensity of the TL glow curve is shifted about 10 K degrees toward the lower temperature side. The TL glow curve shape resembles first-order kinetics for low-radiation doses and second-order kinetics for higher doses. Linear dose behavior was found for doses below 200 Gy and supralinear for higher doses; respectively, with a significant dependence on the dose rate, reaching saturation for higher doses around 2.0 kGy. Due to the dose rate dependence of the TL properties of the CVD diamond sample, it is necessary to take these effects into consideration for dosimetric applications involving synthetic CVD diamond.

Thermoluminescence kinetic parameters of microwave chemically vapour-deposited diamond films at different gamma dose rates

Microwave chemically vapour-deposited (MWCVD) diamond films have been successfully used in dosimetric applications including radiotherapy and industrial dose assessments. The thermoluminescence (TL) properties and dose response, in a suitable MWCVD diamond film thermoluminescent dosimeter, should be independent of the irradiation dose rate used. Dose rate effects have been reported to exist, affecting the TL performance of polycrystalline CVD diamond. In the present work, dose rate effects on the TL kinetic parameters of two MWCVD diamond films of 6 and 12 μm thickness, exposed to 60Co gamma dose rates of 2.4, 5.94 and 13.1 Gy/min, were investigated using a computerised glow curve deconvolution method. The TL glow curves featured a single TL peak at different dose rates, which were best fitted with a first-order kinetic curve having 2–3% figure of merit. No significant dose rate effects on the TL kinetic properties of the studied samples were observed. †Paper presented as a contribution to the 10th International Symposium on Solid State Dosimetry, Mexico City (24–28 September 2007).