Measurements of low photon doses using LiF:Mg,Cu,P and CaF2:Cu dosimeters

The new thermoluminophors LiF:Mg, Cu, P and CaF2:Cu in form of pellets exhibit a significantly higher TL-response than the well-known dosimeters of the types TLD-100 (LiF:Mg, Ti), TLD-400 (CaF2:Mn), TLD-900 (CaSO4:Dy), etc. Furthermore, the thermoluminophor LiF:Mg, Cu, P shows besides its high sensitivity a good tissue equivalence and therefore, only a small variation of the dose response with the photon energy. The lower limits of detection of these new materials are about 5 μGy and 0.2 μGy resp. Therefore, short term measurements of absorbed dose can be realised in radiation fields at very low dose rates (environmental radiation, scattering radiation at medical equipment's etc.) with an accuracy of ±10%. In the field of environmental monitoring the period of exposure can be limited to about 10 days. Using CaF2:Cu detectors an exposure of 24 hours is sufficient for dose measurements with lower accuracy. The reusability of CaF2:Cu pellets is guaranteed without loss of sensitivity independently of the application of different reading and annealing procedures. In the case of LiF:Mg, Cu, P detectors special procedures are needed in order to keep constant TL-properties. The results of dose measurements at low dose levels in different radiation fields demonstrate the advantages of these detector types. (orig.)