Thermoluminescence study of Pink Himalayan salt from Khewra mines, Pakistan

Abstract

In this study thermoluminescence characteristics of the pink Himalayan salt has been studied. For this purpose, pellets of pink Himalayan salt weighing 40 mg were prepared. The ICP-OES and EDX analytical techniques were used to find the elemental composition of the sample. It confirms the presence of Al, Mg, Ca, Sr, S, Zn, K, Mn and Fe etc. along with the main matrix. The XRD analysis shows that the salt has face centered cubic (FCC) structure with average crystallite size of 70.6 nm. The scanning electron microscope (SEM) was used for surface morphology. To investigate the thermoluminescence properties, the pellets were irradiated with 137Cs source in the dose range of 1–5000 mGy. The glow curve indicated the presence of three peaks namely P1, P2 & P3 with two very prominent peaks occurring at 135 °C and 260 °C. The Tmax-Tstop procedure revealed the coinciding peaks in the glow curve and their relative positions. The trapping/kinetic parameters, such as electron trap depth (E), order of kinetic (b) and frequency factor (s) were explored by employing CGCD technique. The values of figures of merit (FOM) calculated at different doses (500 mGy, 1 Gy, 2 Gy & 5 Gy) were found to be 1.14%, 1.24%, 1.11% and 1.13% respectively. This indicates excellent agreement between the experimental and theoretical fitting. The post irradiation fading of the sample pellets were studied at dose of 500 mGy for different time intervals up to 8 week and 30% loss in TL signal was observed within first 24 h which becomes stable after 2 week. On the basis of these results it can be concluded that pink Himalayan salt has a potential to be used in radiation dosimetry.