Response of CaSO4:Dy based TL dosemeter system to high-energy photon beams: theoretical simulation

Response of thermoluminescence (TL) discs under different filter regions of a CaSO(4):Dy based TL dosemeter system was simulated to high-energy photon beams in the energy range of 1.25 MeV to 24 MV ( approximately 9 MeV). This was done using FLUKA Monte Carlo code and also experimentally verified for some energy points. Response of disc D1 under metal filter combination was found to increase with photon energy, whereas that for the discs under polystyrene filter and open window regions of the dosemeter decreases continuously. The changes in the response of the discs under polystyrene filter and open window were attributed to the lack of build-up material. The increase in the response of disc D1 was due to the contribution from secondary electrons produced through Compton and pair production processes mainly arising out from the metal filter combination. The knowledge of the change in the response of individual discs and the ratio of discs' responses under different filter regions of the dosemeter system could be used for the measurement of energy of bremsstrahlung radiation that exists in and around high-energy electron accelerator and could be used for accurate evaluation of personal dose equivalent in high-energy photon field.