THERMOLUMINESCENCE CHARACTERISTICS OF LOCAL NATURAL CALCIUM FLUORIDE AFTER GAMMA RADIATION EXPOSURE

Thermoluminescence (tl) studies of some natural calcium fluoride (caf2) are presented in this work. the glow curves of the materials under investigation show 4 main glow peaks. the third one (p3) at 180 °c is considered as dosimetry peak with calculated activation energy 1.5 ev. the optimum heat treatment annealing at 450 °c for 30 minutes is found to obtain maximum tl intensity with low zero dose response (i.e. b.g. of tld). the dose response with the tl intensity (tl area at each glow peak) is evaluated and found linear at the beginning of build up with gamma radiation dose to certain limit, then start to show supralinear trend. the fading effect at ambient temperature up to 120 days storage time is evaluated. in the first few days high fading is noted and farther become less. for high temperature peaks this effect does not exceed 5%. it is also concluded that the peak shifts to higher direction by about 5oc due to storage for about 4 months. also the heating rate effects as well as the grain size of the powder of the sample particles have been studied in some details.