A new thermostimulated luminescence phosphor based on CaSO 4 : Ag,Tm for applications in radiation dosimetry

Abstract

A new sensitive thermostimulated luminescence (TSL) phosphor CaSO 4 : Ag,Tm has been developed. Its features are: (i) a major glow peak at ∼375°C, (ii) sensitivity comparable to that of CaSO 4 : Tm with a detection threshold of 0.87 mR (0.224 μC kg −1), (iii) linear response with γ-ray dose upto 100 Gy and (iv) post-irradiation stability upto 280°C. These features show that it can be used for the measurement of low levels of radiation exposures even at elevated irradiation temperatures. The hole trap in this phosphor is characteristic of Ag + ion. Its TSL, photoluminescence (PL) and X-ray induced luminescence (XIL) emission spectra are characteristic of Tm 3+ similar to CaSO 4 : Tm. γ-ray irradiation results in a drastic reduction in the PL emission due to the reduction of Tm 3+ which restores only partially even after annealing at 700°C. A γ-ray induced metal to metal (Ag + to Tm 3+) charge transfer is proposed in this regard. Restoration of TSL sensitivity during the above treatment, however, is complete which indicates that the electron traps involved in TSL are different. The XIL intensities in Tm and Ag,Tm doped CaSO 4 remain nearly constant over 100–600 K. However, their thermostimulated exoelectron emissions are insignificant.