VARIATION IN RESPONSE AND PHYSICAL PROPERTIES OF SOME COMMERCIAL THERMOLUMINESCENT DOSIMETERS LiF (TLD-100), CaF2: Dy (TLD-200) and CaSO4: Dy (TLD-900) AFTER GAMMA IRRADIATION

For routine dosimetry, several TLD materials have been used, each having itsown definite properties. In this paper, the physical TL properties of the three usedcommercial thermoluminescent (TL) materials, [ LiF (TLD-100), CaF2:Dy (TLD-200)and CaSO4:Dy (TLD-900) ], have been studied in order to identify the efficiency of theoptimum material for gamma radiation measurements. The main investigateddosimetric properties are glow curve structure, sensitivity, dose response, fading,memory effects and sensitization.The experimental results show that the glow curve structure of the , TLD-100includes 4 glow peaks at 135, 182, 210 & 230 oC , TLD-200 includes 2 peaks at 179& 240 oC and TLD-900 includes 3 peaks at 123, 220 & 338 oC. The sensitivity ofTLD-200 was found to be 9-20 times greater than the standard one (TLD-100), butfor TLD-900, it was found 8-13 times greater than the standard one. It was found thatthe TL response of the three phosphors fit to a straight line in the logarithmic scalefrom, 50 μGy – 5 Gy , 50 μGy – 10 Gy and 5 μGy – 10 Gy, respectively. The fadingvalues were found to be ≈ 7.5 & 20.1 %, 14 & 32% and 10.4 & 12 % for the threephosphors, respectively, after the storage for 3 months at 25 & 50 oC, respectively.From the results which previously mentioned, calcium Sulphate doped by dysprosiumhas been selected for local preparation.