Low temperature thermoluminescence of annealed LiF:Mg, Cu, P

Abstract

Two main thermoluminescence peaks at 123 and 135K, plus some weaker features near 65, 95, 242 and 265K, have been observed in LiF:Mg, Cu, P dosimeter samples that had been annealed at 240°C. The photon wavelengths in the main peaks span the spectral range from 250 to 470nm and the maximum intensity is near 310nm. The origin of these main TL peaks at 123 and 135K are discussed in terms of a range of defect complexes linked to intrinsic defects. In particular the temperatures match the annealing stages for defect perturbed F–H and VK–e type recombination, respectively. The 65K feature is considered as the result of electron–hole recombination via relaxed exciton decay. These models suggest reasons for the differences between the various emission bands and the longer wavelength emission linked to high temperature electron decay processes.High temperature annealing modifies the component low temperature TL features with annealing up to ∼300°C resulting in low temperature TL signal loss, but with partial recovery found for all the low temperature TL peaks when the samples were annealed at higher temperatures up to 390°C. It is suggested that the intensity loss and the recovery are the summation of numerous effects from a wide range of defect complex variations which exist in these heavily doped materials. The low temperature data offer further insights into the changes which occur in the structures related to optimising the high temperature TL dosimetry.