Use of Chinese LiF:Mg,Cu,P (GR-200) TL detectors at therapy-level absorbed doses

The objective was to find out whether or not the highly radiation-sensitive Chinese thermoluminescent (TL) LiF:Mg,Cu,P (GR-200) detector pellets can be used in therapy-level dosimetry. For this purpose the precision was investigated at an absorbed dose level of 1 Gy using a commercial TL read-out instrument. Relative standard deviations, sigma rel, of the individual calibration factors were found to be in the range between 0.2% and 0.6% from 30 randomly selected detectors, with the mean at 0.37%. Apart, linearity checks between 1 and 6 Gy resulted into a sublinear response of up to -4% which was successfully corrected for by a third-order polynomial curve fit. The residual signal turned out to be about 0.1% after one annealing cycle almost independent of the applied dose, and this figure could be reduced by two more decades after repeated annealing cycles.