Sensitivity loss and recovery for individual TL peaks in LiF:Mg,Ti and LiF:Mg,Cu,P after high-dose irradiation

Radiation-induced sensitivity loss of LiF:Mg,Ti and LiF:Mg,Cu,P has been studied for individually deconvoluted peaks over the dose range 1-5000 Gy. The recovery of LiF:Mg,Ti sensitivity by extending the Lime of annealing at 400 degrees C was also investigated. The main peaks 4 and 5 of LiF:Mg,Ti were found to be the most resistant to radiation, with no loss of sensitivity observed up to doses of 10 Gy. At the highest dose of 5 kGy and following the standard annealing procedure of 1 h at 400 degrees C, the sensitivity is reduced to less than half of the value at low doses, for all peaks. Extending the annealing time leads to partial recovery of detector sensitivity. Again, this effect is the strongest for peaks 4 and 5, which restored completely their sensitivity after 11 h of annealing at 400 degrees C. Sensitivity loss after doses higher than 100 Gy appears to be irreversible and even 21 h of annealing at 400 degrees C did not recover the original sensitivity. For LiF:Mg,Cu,P the 270 degrees C/10 min +240 degrees C/60 ruin annealing cycle was applied. Surprisingly, we found that LiF:Mg,Cu,P is more resistant to radiation than LiF:Mg,Ti-we observed no decrease of sensitivity after pre-doses of up to 100 Gy. Moreover, we observed no change of the glow-curve shape after pre-doses of up to 1 kGy, suggesting that the loss of sensitivity is not a result of radiation damage of trapping centres, but some other processes. (C) 2007 Elsevier Ltd. All rights reserved.