Evaluation of the thermally and optically stimulated response of as Italian Silicate irradiated in 60Co beams

Abstract

In this work, pellets were manufactured in a proportion of 2:1 of powdered samples of Obsidian black:Teflon (dimensions of 6.0 mm in diameter and 0.8 mm in thickness). The pellets were irradiated using a Gamma-Cell 220 System, model 200, Atomic Energy of Canada LTD (60Co). The TL and OSL responses were analyzed using the reader system composed by the TL/OSL meter Risø, model TL/OSL-DA-20, and the TSEE response was obtained using a homemade reader system developed at the Calibration Laboratory, at IPEN. After the TL, OSL and TSEE measurements, the pellets were thermally treated at 400 °C during 1 h, for reutilization. The physical and chemical characterization of powdered Obsidian was also investigated using the X-ray diffraction, XRD (using a diffractometer Equinox 1000, Inel), scanning electron microscope, SEM, and energy dispersive X-ray spectroscopy, EDX (the last two using a scanning electron microscope with an energy dispersive X-ray microanalyser Vega 3 SEM, Tescon) techniques. The results proved, basically, that Obsidian is a natural glass and composed mainly of silica (82.4%). The TL glow curve revealed a dosimetric peak at the temperature of 220 °C, and the TSEE emission curve showed a peak at about 300 °C. The results obtained in the reproducibility of response test were: 2.9% (TL), 3.0% (TSEE) and 3.1% (OSL). The lower detection limits were: 48.1 Gy (TL), 18.1 Gy (TSEE) and 79.3 Gy (OSL). The dose-response curves showed, in the case of TL, a supralinearity behavior between only 500 Gy and 2 kGy with a following saturation of the response. For the TSEE response, a sublinearity was seen with a following saturation of the response. For the OSL technique, linearity could be observed in the interval from 500 Gy to 2 kGy and then a tendency to saturation.