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Some novel features of post-500°C heating blue stimulated OSL emission of fired natural quartz

Koul D. K., Soni A., Datta D.

Geochronometria

2017

Vol. 44, no. 1

287--298

In this study, some novel features of the post 500°C blue stimulated optically stimulated luminescence (OSL) of fired geological quartz are reported. Different observations (i) pulse annealing and (ii) impact of bleaching on high temperature TL glow peak suggested 510°C (heating rate of 2°C/s) TL peak trap to be responsible for the observed emission. The dosimetric properties of this emission were seen to make its applicability for dose assessment till kGy range. The signal was seen to be easily bleachable, reaching background value within 100 s with blue light at 125°C. The signal qualified all the tests (i) reproducibility, (ii) negligible recuperation and (iii) accuracy of dose recovery needed for reliable assessment of the radiation dose with modified Single aliquot regenerative (SAR) protocol. Considering the bleachability and high dynamic dose range of this signal, it has the potential to stretch the upper dose limit of dating by one order of magnitude than possible with conventional OSL, corresponding to 325°C TL trap. So, combining all the results, the signal reported here could be very useful for dosimetric applications involving measurement of high radiation dose, like dating.

Thermally assisted OSL: a potent tool for improvement in minimum detectable dose and extension of dose range of Al2O3:C

Soni A., Mishra D. R., Bhatt B. C., Gupta S. K., Rawat N. S., Kulkarni M. S., Sharma D. N.

Geochronometria

2013

Vol. 40, no. 4

258--265

The influence of electron-phonon interaction on the shape of the optically stimulated lumi-nescence decay curve of Al2O3:C has been studied using thermally assisted optically stimulated lumi-nescence (TA-OSL). The minimum detectable dose (MDD) of a phosphor depends on the standard deviation of the background signal which affects the signal-to-noise ratio. The standard deviation of the background signal reduces at lower stimulation light intensity while the readout time increases. Further, measurement at higher temperature enhances the OSL signal with faster decay due to the temperature dependence of photo-ionization cross-section. To achieve the same decay constant and more signal, the temperature of measurement was raised. As a result of lowering the stimulation in-tensity at higher temperature (85°C) the overall MDD of α-Al2O3:C was found to improve by 1.8 times. For extension of dose linearity in higher range, deeper traps were studied by simultaneous ap-plication of CW-OSL and thermal stimulation up to 400°C, using a linear heating rate of 4K/s. By us-ing this method, two well defined peaks at 121°C and 232°C were observed. These TA-OSL peaks have been correlated with two deeper defects which can be thermally bleached at 650°C and 900°C respectively. These deeper defects are stable up to 500°C, so they can store absorbed dose infor-mation even if the sample is inadvertently exposed to light or heat. The dose vs. TA-OSL response from deep traps of α-Al2O3:C was found to be linear up to 10 kGy, thus extending its application for high dose dosimetry.