The attenuation of thermoluminescence light in TLD-400

TLD-400 chips were chosen for the measurements of gamma-ray doses in BNCT mixed-field beams in this work because of their negligible thermal neutron sensitivity. Each TLD-400 chip was treated as an individual detector with a given ID number and denoted orientation to improve the measurement uncertainty. We proposed an in situ calibration of the TLD-400 chips by using small laboratory sources in direct contact with the TLD chips. The attenuation effect of the TL lights has been determined by using a simplified attenuation model in couple with the energy deposition distribution acquired from Monte Carlo code simulations. Since the energy deposition distribution is highly non-uniform, it has been demonstrated that a correction of the TL light attenuation plays a critical role for the proposed in situ calibration to be feasible and effective.