Thermoluminescence and infrared light stimulated luminescence of limestone (CaCO₃) and its dosimetric features

Thermoluminescence (TL) and infrared light stimulated luminescence (IRSL) of limestone (CaCO₃) collected from the Mawsmai Cave, India is reported. Structural and compositional analyses show that the sample has a rhombohedral crystal structure and contains 33.45% of CaO. TL measured at 1 °C/s from a sample irradiated to 600 Gy produces three composite glow peaks P1, P2 and P3 at 92, 165 and 239 °C respectively. The nature of the glow peaks is suggestive of the presence of a continuum trap distribution with activation energy between 0.40 eV and 1.12 eV. As regards to dose response, the TL intensity of P1 increases at a uniform rate with dose between 10 and 1000 Gy. Interestingly, the intensity of P3 increases with dose through two uniform regions, one within 10-100 Gy and the other between 100 and 1000 Gy. The IRSL measurement produces ill-shaped decay curves. The IRSL intensity also increases with dose at two different uniform rates within 10-100 Gy and 100-1000 Gy. Residual TL recorded after each IRSL measurement shows similar dose response as that under the conventional TL. Regarding fading, P1 fades by 88% and P3 by 14% within 12 h of irradiation.