Response of CaSO4:Dy Teflon embedded thermoluminescent dosimeter badge on different ISO phantoms for photons and beta sources using FLUKA and GEANT4

In this study, Monte Carlo codes FLUKA and GEANT4 were used to assess the angular variation in the response of CaSO4:Dy Teflon disc based TLD badge. These badges were positioned on various ISO phantoms to simulate the angular exposures ranging from 0° to 60° for photons within the energy range of 12.3 keV to 1.25 MeV, as well as for 90Sr/90Y and 106Rh/106Ru beta sources. Plots showing the TL response of the discs in terms of Hp(10), Hp(3), and Hp(0.07) as a function of photon energy were obtained for ISO slab, cylindrical, and pillar phantoms, respectively. Additionally, the study estimated the angular variation in the response of disc ratios (R12 and R32) with respect to both photon and beta energies. The simulation results revealed that the response of the open disc (D3) was higher for lower X-ray energies, attributed to an increase in the photoelectric effect. Conversely, the response of the disc under the metal filter (D1) was observed to increase with the angle, indicating the Compton scattering from the cassette body and phantom, especially at lower X-ray energies. Beta response of both disc D2 (under PMMA filter) and D3 found to be decreasing with the angle of incidence while R32 ratio found to be increasing with the angle of incidence for both 90Sr/90Y and 106Rh/106Ru beta sources. Notably, the simulated results demonstrated good agreement with experimental observations, reinforcing the reliability of the Monte Carlo simulations for complex interactions and responses of TLD badges under different irradiation conditions.