COMPARISON OF TWO EXTREMITY DOSEMETERS BASED ON LiF:Mg,Cu,P THIN DETECTORS FOR MIXED BETA-GAMMA FIELDS

摘要

Two types of thin LiF:Mg,Cu,P detectors, GR-200F and MCP-Ns, have been characterised for use in the design of an extremity dosemeter for mixed beta-photon radiation fields. Both detectors consist of an extremely thin layer of sensitive material with effective thicknesses of 5 and 8 mg cm~(-2), respectively, held in a 5 mg cm~(-2) PVC ring holder. Dosimetric performance was analysed according to the ISO 12794 standard and compared with 240 mg cm~(-2) TLD-100 measurements. In particular, the energy response was obtained for ISO narrow X-ray spectra, ~(137)Cs, ~(60)Co, ~(204)Tl and ~(90)Sr/~(90)Y. From these measurements a mean calibration factor was calculated to estimate H_(p)(0.07). Subsequently, the performance of the dosemeters was checked for a set of 10 different mixed photon and beta-photon fields. The study shows that the proposed dosemeters can estimate H_(p)(0.07) in a wide range of mixed beta-photon fields with a maximum deviation from the given dose of 30percent and an overall uncertainty of the order of 25percent (k velence 1). However, the results also highlight a large variability among the different thin detectors and, thus, the standard TLD-100 material is recommended whenever the workplace does not include low-energy beta radiation.