Graphite-mixed CaSo4: Dy teflon TLD discs for beta dosimetry.

The thickness of commonly employed thermoluminescent dosemeters (TLDS) is responsible for the problem of energy dependence in beta dose estimation in situations where this thickness is comparable to the range of beta particles in the TLD material. The effective thickness of solid TLD discs can, however, be reduced by use of some additives which would reduce their transparency to the TL light. The incorporation of various amounts of graphite powder into 0-8 mm thick CaSO4: Dy Teflon TLD discs has been investigated. This has considerably reduced their energy dependence for beta rays with Emax values ranging from 0-4 MeV to 2-27 MeV. Addition of graphite also results in sharp glow curves thereby minimizing the heating time during TL measurements. Significantly, graphite was also found to reduce the non-radiation-induced TL signal and this helps in low dose measurements.