Photon energy response of silicon dioxide fibre optic and TLD 100 using Monte Carlo simulation

Abstract

Even though there are other methods in detecting and measuring radiation, thermoluminescence (TL) is still the main choice in many areas of ionizing radiation dosimetry. This fact leads to the countless investigation of other materials to be used as TL phosphor. Recent material being recognised and investigated as a TL phosphor is silicon dioxide fibre optic. This study focuses on the energy response of silicon dioxide fibre optics and TLD 100 subjected to photon irradiation. The TL responses for photon energies, ranging from 20 keV to 20 MeV, were investigated as energy absorbed in the TL materials. The simulation was performed using Monte Carlo NParticle transport code version 5 (MCNP5). The input parameters included in this study are geometry specification, source information, material information and tallies. Tally F6 was used to obtain average fraction of energy deposited by TL materials in the simulation. Comparisons of energy responses were made between calculated, simulation and previous experiment. For TLD 100, calculation results show an over responses at below 100 keV while the simulation and experiment results shows over response at below 150 keV. In terms of energy dependence, TLD 100 has a relatively flat response since its response lies within ANSI acceptable range. Unlike TLD 100, fibre optic had a limited range of flat response. A flat response can only be seen at energy range of 200 keV to 10 MeV. Although simulation results exhibit similar pattern of energy responses, the values are slightly higher when compared to calculated and experiment results, especially at lower energy (< 100 keV). The effect of different dopant concentrations on the energy responses were also analysed and discussed. Result from simulation shows no apparent effect of different dopant concentration on the energy response.