Response of thermoluminescence dosemeters to beta radiation and skin dose assessment

The response of a TL dosemeter to beta radiation is heavily influenced by the absorption of the radiation in the dosemeter thickness. As a consequence, the assessment of skin dose depends either on the execution of a calibration with a beta field of the same characteristics as that to be monitored or on the knowledge of depth-dose distribution in the dosemeter. Depth-dose distributions have been experimentally estimated for optically transparent dosemeters in a number of irradiation geometries and with sources of different configuration and energy. General algorithms based on the point-source function of Loevinger have been developed, by which the response of TL dosemeters can be evaluated and skin dose correction factors derived. TLD responses to beta radiation calculated by the present method are in sound agreement with other author's measurements. The dependence of beta ray absorption on the configuration of source and the source-to-detector distance has been picked up. Variations of source-to-detector distance as large as 30% of the maximum beta range account for differences up to 40% in the skin dose correction factors for a 200 mg cm-2 thick dosemeter. The proposed scheme results in a useful tool in skin beta dosimetry using multiple TLDs behind different absorbers. In practical applications thick dosemeters may be used properly only in well-known radiation fields. Conversely, the described method allows an acceptable estimate of the skin dose error.