Gamma dosimetry with Al2O3 thermoluminescent phosphor

Preparation of thermoluminscence (TL) dosimetric grade A12O3 powder and pellets five times more sensitive than TLD-100 is described. Glow peaks at 50, 125, 250, 325, 475 and 625 degrees C with emission in the blue region have been observed; Si and Ti have been identified as the impurities responsible for TL in this phosphor. Studies of the TL growth rate with exposure showed that the 250 degrees c peak grew linearly up to 400 R and then at a supralinear rate of (exposure). The growth of the 475 degrees c peak was almost linear at a rate of (exposure) 1-05, while that for the 625 degrees C peak was sublinear at (exposure) 0-85. The 250 and 475 degrees 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 625 degrees C TL related traps were found to be essential for sensitizaiton. Supralinearity and sensitization in Al2O3 phosphor could be consistently explained by the deep trap model.