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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.

Investigation on resonant laser ablation spectrum of Fe in 281.5-285.5 nm wavelength region

Ma J., Ji X., Cui Z.

Optica Applicata

2008

Vol. 38, nr 2

405-411

Laser ablation of solid Ti samples has been studied using a tunable pulsed dye laser. Six resonant laser ablation (RLA) spectral lines of Fe in the Ti sample are firstly measured in the 281.5-285.5 nm wavelength region. The initial state of the RLA spectral lines is a5F, the resonant states are z5H0, x5P0 and y5G0, respectively. The influence of laser power density on the intensities of RLA spectrum is discussed. The relationship between the laser wavelength and the photo-ionization cross sections of the resonant state 5G0 is analyzed.