Study of non-exponential OSL decay curve within critical physical conditions of synthetic quartz material and their resolution by selection of suitable protocol

Abstract

Researchers had reported that synthetic quartz which was annealed either at 400 °C irradiated by 75.6 Gy beta doses or at 600 °C irradiated by 25.2 Gy beta doses showed better rise in OSL intensity at room temperature depicting the change from non-exponential to exponential shape of the decay curve. Under these conditions, the non-exponential shape of decay curve with weaker OSL intensity was observed. It was due to re-trapping of optically released electrons by shallow traps corresponding to 110 °C TL glow peak and it was later verified by ESR spectra.In order to eliminate the non-exponential behaviour of decay curve, the researchers suggested OSL measurement at elevated temperature so as to further remove the contribution of shallow traps. However, in the present work, the OSL decay curves are recorded at 160 °C for 400 °C and 600 °C annealed samples irradiated by 2.52 Gy, 5.04 Gy, 25.2 Gy and 75.6 Gy beta doses. Both the samples show non-exponential shape of OSL decay curve up to 25.2 Gy beta doses. However, it gradually changes to exponential shape with better OSL intensity at higher beta doses. Additionally, few attempts were made to examine the non-exponential pattern of OSL decay at room temperature as well as elevated temperature within respective critical conditions by using fitting equations. It reports that various mode of non-exponential patterns of curve and their changes were influenced by strength of physical conditions. Further, a new protocol of cyclic sequence of doses, pre-heat up to 200 °C, test dose and stimulation at 125 °C for 40 s stimulation time was implemented to identical treated samples. It shows disappearance of non-exponential shape of OSL decay by growth in OSL intensity. These changes in OSL pattern were further justified by the contribution of annealing, irradiation, thermal transfer and thermal assistance process and TL measurements before and after OSL.