High-exposure dosimetry with LiF (TLD-100) by photo-acoustic spectrometry

Optical absorption of LiF:Mg, Ti (TLD-100) as-received and annealed powders was investigated in the 300-700 nm range by photo-acoustic spectrometry (PAS). Near-logarithmic behaviour was found between 3 kGy and 1 MGy for the observed absorption peaks at 380, 444 and 547 nm. Optical bleaching properties were studied with white light and monochromatic irradiations at 254 and 366 nm. Fading characteristics were determined. It is shown that PAS is an appropriate tool for measuring doses on powders, especially in the high-dose range. Suggestions are made for extending the dose range to lower levels. In this way LiF TLD-100 powder may be used continuously from the mu Gy (by thermoluminescent methods) to the MGy (by PAS) range.