Study of CaSO4:Dy and LiF:Mg,Ti detectors TL response to electron radiation using a SW Solid Water phantom

The TL response to electron-radiation is known to be dependent on the electron energy and the dosimeter thickness, justifying the present study of LiF:Mg,Ti (TLD-100, Harshaw) and CaSO4:Dy (developed and produced at the Dosimetric Materials Laboratory of the Radiation Metrology Centre) TL responses to electron radiation using a SW Solid Water phantom. Dosimeters were previously divided in groups according to their individual sensitivities to 60Co gamma-radiation in air and electronic equilibrium conditions. The electron beams of different energies were provided by a Varian Clinac 2100C linear accelerator and the dosimeters were set at the depth of maximum dose of each beam over 5g/cm2 of the SW Solid Water phantom made of 30×30cm2 plates of different thickness. The irradiations with doses ranging from 0.01 to 3.25 Gy delivered at 4 Gy/min were carried out with the electron focus at 100 cm of the phantom surface in a 10×10cm2 field. The TLD signal was always read in a Harshaw 3500-QS reader 36 h after the irradiation and each value is the average of five readings. The dose-response of both materials presented a linear behavior for doses ranging from 0.05 to 1.25 Gy in all studied energies; however, the CaSO4:Dy TL sensitivities are 17.8-21.5 times greater than the ones presented by the LiF:Mg,Ti. The lower detection limit calculated for the LiF:Mg,Ti is 8.49-11.84 times greater than the ones obtained for the CaSO4:Dy. Due to these facts, CaSO4:Dy dosimeters may constitute one more option for applications in the radiation therapy area in the studied energies and doses, even considering that both CaSO4:Dy and LiF:Mg,Ti TL responses were altered by the electron-radiation energy.