Comparative study of thermoluminescent responses of diverse CVD diamonds

The thermoluminescent properties of two types of transparent polycrystalline chemical vapour deposition (CVD) diamonds, and of a non-transparent freestanding CVD cutting material, type CVDITE-CDM, were investigated to be used as detectors of X-rays. The reproducibility in TL response of both types of diamonds was measured with the use of radiation emitted from the 55Fe and 137Cs radioisotopes. A significant change of TL sensitivity after the repeated irradiation/readout cycles and of annealing procedures of the transparent CVD diamonds was observed. In contrast to it, the CVDITE-CDM samples containing a non-diamond component show reproducible TL properties. The sublinear TL response of CVDITE-CDM diamonds for doses higher than 1.5 Gy is presented. It is demonstrated that the influence of daylight on their TL response sensitivity can be eliminated by preheating at 250 °C for 30 s. The Raman and photoluminescence spectra of the samples at room temperature are analyzed. The content of the non-diamond component in different CVD diamond samples estimated by these methods is correlated to the relevance of a TL peak at a temperature of ≈ 310 °C.