Cooling rate effects in thermoluminescence dosimetry grade lithium fluoride. Implications for practical dosimetry

Abstract

A systematic investigation of the effects of cooling rates in the range of 10(-1) to 2 X 10(5) degrees C min-1 applied to TLD-700, LiF thermoluminescence dosemeters has shown that the 'transfer sensitivity' effect observed by Booth, Johnson and Attix (1972) is only of importance for cooling rates greater than 10(3) degrees C min-1. Although it is concluded that for practical dosimetry purposes the effect may be ignored it is not clear why Booth et al. observed such large changes and until this discrepancy is explained it is recommended that a low temperature pre-irradiation anneal should be used.

AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs

“…To maintain the same sensitivities for the detectors, it is critical to follow a consistent annealing procedure. The general consensus on the optimal annealing procedure for LiF,Mg,Ti is to anneal for 1 h at 400°C followed by 16–24 h at 80°C, although shorter annealing periods may suffice The high‐temperature component eliminates the previous dose information while the low‐temperature component restores the original shape of the glow curve thus maintaining the sensitivity of the TLD. With careful annealing, the sensitivity of each TLD will change minimally, including both the average sensitivity of the TLDs and the relative sensitivity of each element ( k s,i ).…”