Chapter 3 - Microdosimetric Interpretation of Photon Energy Response in TL Systems

Abstract

This chapter discusses a microdosimetric interpretation of photon energy response in thermoluminescence (TL) systems. Most of the radiation sources used in radiotherapy and medical diagnostics or those considered in radiation protection emit photons in the energy range from a few keV to 50 MeV. It is desirable for a TL detector to have a linear response with absorbed dose over a wide range of levels of dose; the measured response of real detectors is usually linear in only a limited dose range. The deviation of the detector's response from linearity at dose levels different from the calibration level is usually described by the linearity index. In the multihit model it is assumed that the detector contains one type of hypothetical target. It is found that when energy of ionizing radiation is deposited inside the target volume, there is a certain probability to produce some changes at the molecular level. The outcome of these changes is the macroscopically observed effect, such as the emission of TL light or changing of the EPR signal. It is observed that one of the most significant successes of the microdosimetric one-hit model is the explanation of the anomalous photon-energy response of the high sensitivity LiF:Mg,Cu,P detectors.