Gamma dosimetry with A1203 thermoluminescent phosphor

Preparation of thermoluminescence (TL) dosimetric grade Al203 powder and pellets five times more sensitive than TLD-100 is described. Glow peaks at 50, 125, 250, 325, 475 and 6250C with emission in the blue region have been observed; Si and Ti have been identified as the impurities for TL in this phosphor. Studies of the TL growth rate with exposure showed that the 2500C peak grew linearly up to 400 R and then at a supralinear rate of (exposure)sup(1.4). The growth of the 4750C peak was almost linear at the rate of (exposure)sup(1.05), while that for the 6250C peak was sublinear at (exposure)sup(0.85). The 250 and 4750C peaks together show a linear response up to 40,000 R. The phosphor had no light sensitivity and is very well suited for gamma dosimetry as pellets or powder. Studies of sensitization and supralinearity, with sensitizing exposure, sensitizing anneal temperature and test gamma and alpha exposures are reported. Initially filled 6250C TL related traps were found to be essential for sensitization. Supralinearity and sensitization in Al203 phosphor could be consistently explained by the deep trap model. (author)