REPRODUCIBILITY AND EFFECT OF DELAYED READOUT ON LiF: Mg, Ti TLD TREATED WITH DIFFERENT PREHEAT TIME TECHNIQUES: A GLOW CURVE STUDY
The glow curve in TLD-100 was compared by applying long preheat time, short preheat time techniques and without preheat technique before the TLD readout. Fading effect of the TLD signal upon certain storage time with long preheat time (100°C, 10 minutes using the oven) and short preheat time techniques (100°C, 10 seconds using the reader) were also studied. 15 TLD-100 chips were used with 3 of the TLD chips were used for measuring background radiation. 12 TLD chips were annealed, irradiated, preheated long and short preheat time techniques) and analyzed. The TL signals output from TLD chips of without preheated were used as the control. Two sets of data were taken using TLD chips irradiated with 6 MV and 10 MV photon beams. TL signal output was recorded the highest for short preheat time, followed by long preheat time and no preheating. The TL signal loss upon certain storage time was also reduced when short preheat time technique was applied. By applying long preheat time technique the low temperature peak in the glow curve was completely removed for both energies. Whereas, TLD chips exposed to 6 MV and with short preheat time technique the low temperature peak did not disappear completely but decreased in intensity as compared to the control data by 19.80%, 37.69%, 48.19% and 100% at 24, 48, 72 and 96 hours after exposure prior to readout, respectively. Meanwhile, for 10 MV photon beam with short preheat time, the small peak intensity was reduced by 19.58% for readout at 24 hours after irradiation and 100% for 48,72 and 96 hours delayed time prior to readout. It was observed that the TLD-100 was highly dependent on preheat heating time before readout. Short preheat time technique was able to reduce post irradiation fading of TLD-100 dosimeters.