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.