Thermoluminescent response of LiF (TLD-100) to 5-30 keV electrons and the effect of annealing in various atmospheres.

The response of single crystal and extruded ribbons of TLD-100 to 5-30 keV electrons was investigated. If annealing is done in a vacuum, the sensitivity of TLD-100 single crystals to these electrons and the resultant glow curve are essentially the same as when irradiation are carried out with 137Cs gamma rays. All discrepancies in sensitivity can then be accounted for by the higher LET of electrons. The commonly used 'standard annealing' at 400 degrees C for one hour produced a change in the glow curve shape and a loss in sensitivity in contrast to the vacuum anneal results. Diffusion of hydroxyl ions into the sample during air annealing is believed to be the primary cause for this change. These results explain the source of the 'dead layer' proposed to explain the variation with particle size of the luminescent efficiency of X-ray irradiated TLD-100 powder and the low TL efficiency from low energy electron irradiations. With the use of the vacuum annealing procedure, the same sensitivity and reproducibility can be achieved for the dosimetry of low energy electrons and other shallowly penetrating radiation as is currently achieved for the dosimetry of X-rays.