Dosimetric properties of natural Brazilian topaz: A thermally stimulated exoeletronic emission and thermoluminescence study

The dosimetric properties of natural colourless Brazilian topaz were studie d via thermally stimulated exoeletronic emission (TSEE) and thermoluminesce nce (TL) techniques. The samples were prepared in three ways: (i) powdered samples with grain sizes from 0.75 to 0.150 mm, (ii) pellets prepared with powdered topaz mixed with Teflon in the 1/2 ratio (wt), and (iii) crystals sizing about 5.0x5.0x3.0 mm(3). The TSEE curves displayed a peak at 190 deg rees C and the area under this peak increases sublinearly with the dose ran ge from 10(-1) to 10(2) Gy, for irradiations with X-rays and gamma-rays fro m a Co-60 source. The dependence of the TSEE with the energy of the X-rays indicates that the TSEE intensity increases as the energy of the photon inc reases. The TL emission curves of topaz samples both as pellets and powder were measured using a home made TL reader. The glow curves were composed by three main peaks at 100 degrees C, 180 degrees C and 210 degrees C, The em ission spectra were obtained from 300 to 580 nm in steps of 10 nm. All thre e peaks have the same spectra with main emissions centred at 390, 430 and 4 60 nm. The dose dependence of the TL curves up to 500 Gy of gamma-rays from the Co-60 source indicates that all the TL peaks increases non-linearly as the dose increases. The results were compared with the well known CaSO4:Dy and LiF dosimeters and it was possible to conclude that the colourless nat ural Brazilian topaz is a suitable material for dosimetric applications. (C ) 2000 Elsevier Science B.V. All rights reserved.