Thermoluminescence (TL) related to [SiO4/M]° defects (M = Li or Na) in quartz

The dose dependence of the 190 and 200 K TL peaks of Al-Li and Al-Na containing quartz (TL(M), M = Li or Na) is described. The TL(M) peaks were excited by two X-irradiations at 80 K with warming to 250 K between the two irradiations. The dose dependence was examined separately as a function of the time of the first irradiation (t₁ ) and of the second irradiation (t₂). Slopes between 0 and 1.15 were obtained, depending on thermal and radiation pretreatments of the samples. The variations in slope are shown to be related to the filling of deeper traps competing with the [SiO₄M]⁺ traps related to the TL(M) peaks. A first irradiation of only 2 s was found to release M-ions and produce [SiO₄/M]⁺ electron traps at a concentration which took about one hour of the second irradiation to fill them. With all competing traps stable at 250 K full, and keeping t₁ constant, the dependence of TL(M) on t₂ started with a slope of 1.0. The curves then reached a maximum near t₂ = 1500 s and decreased for longer t₂ values. This decrease gives support to a hypothesis according to which many M-ions get trapped at unidentified X_i defects during long irradiations, and are lost for the production of TL(M)