THERMOLUMINESCENCE OF BRAZILIAN TOPAZ

Thermoluminiscence measurements were performed on samples of yellowish Brazilian Topaz from Acari, MG. Virgin samples revealed peaks 2 and 4 at about 150 and 300 degrees C, respectively, while in samples with e xtra dose of gamma-rays, we observed another peak at 80 degrees C. Whe n topaz samples were thermally treated, peak 4 vanished and peak 3 at about 180 degrees C, became visible. Isothermal decay of peak 2 perfor med on virgin samples showed that peak 3 is present on this samples to o. The spectra of the first 3 peaks are very similar in the range of 3 50 to 500 nm indicating that the recombination processes related to th ese 3 peaks could be the same. The dose dependency of the TL intensity of the first 3 peaks was mesured from 0.5 to 400 Gy and it seems to s tart saturating above 400 Gy.