Heat transfer during the readout process of a Thermoluminescent Dosimeter (TLD)

A Thermoluminescent Dosimeter (TLD) is a commonly used passive device to ensure radiation safety in multiple environments. TLDs are commonly deployed in medical and nuclear facilities to protect personnel from radiation exposure, as well as in aviation to measure exposure to cosmic radiation at high altitudes. Additionally, TLDs also play a crucial role in radiative safety during space travel by monitoring both cosmic radiation and radiation from on-board nuclear reactors. Radiation readout of a TLD involves rapid heating of the device comprising an encapsulated radio-sensitive crystal. Understanding the nature of transient heat transfer during this process is critical for efficient and accurate sensing. While this problem has been studied in the past through numerical simulations, this work presents a comprehensive analytical heat transfer model to predict the transient temperature distribution, and, therefore, the detection effectiveness during jet impingement based TLD heating. The analytical model accounts for the two-dimensional two-material geometry of the TLD, as well as the spatially varying convective heat transfer caused by the impinging hot jet. Temperature field computed from the analytical model is shown to agree well with numerical simulations. It is shown that thermal performance of the TLD is very sensitive to the encapsulant thickness and thermal conductivity, whereas the jet speed is found to have limited impact on the rate of heating. Several practical insights into thermally optimal design of the TLD are discussed. These results expand the fundamental understanding of heat transfer in a TLD, and may help improve the effectiveness of an important nuclear safety device.