Relative thermoluminescent efficiency of LiF detectors for proton radiation: Batch variability and energy dependence

The available experimental data on the relative thermoluminescent efficiency of the LiF:Mg,Ti dosimetric peaks for protons are contradictory. There are several reports showing that the efficiency exceeds unity by even more than 30%, however, many others show the efficiency close to unity or even lower. These contradictory data might be a result of the real variability of TLD properties or of not perfectly reproduced experimental conditions.In an attempt to resolve this issue, the efficiency of 16 batches of LiF:Mg,Ti (MTS) detectors for 60 MeV protons produced at the IFJ Kraków over the last 20 years was measured. All values of the relative TL efficiency were found to exceed unity significantly, with an average of 1.09. Dispersion between different batches was very low, all data were within 4% of the mean value.In second part of experiment the dependence of the relative efficiency of LiF:Mg,Ti and LiF:Mg,Cu,P detectors on proton energy was determined. The efficiency for LiF:Mg,Ti dosimetric peaks was found to have a maximum of 1.20 at about 20 MeV. For LiF:Mg,Cu,P the relative efficiency decreases systematically with decreasing proton energy, from 0.96 at 56 MeV, to 0.61 at 11 MeV.

► We compared the relative TL efficiency to protons of 16 different LiF:Mg,Ti batches.
► Efficiency values are larger than 1 and show only minimal scatter between batches.
► LiF:Mg,Ti efficiency shows a maximum of 1.2 for about 20 MeV protons.
► LiF:Mg,Cu,P efficiency decreases with decreasing proton energy.