Excitation density dependence in radiation detection

The effects of excitation density or linear energy transfer (LET) on the response of radiation detectors, in particular for phosphor-based detectors, are overviewed, with an emphasis on the cases for heavy charged particles. The energy deposition density and its distribution by the heavy charged particles is introduced in comparison to the cases of low-LET radiations (high-energy photons and electrons) and photoexcitation. Subsequently, sources of the heavy charged particles are briefly introduced. Regarding to the phosphors for radiation detection, a conventional phenomenological model for LET-dependent scintillation light yield, i.e., Birks model, is discussed in detail. An alternative kinetic approach for the quantitative analysis of the LET effects is presented. Furthermore, some dynamical aspects of the dense excited states in the LET effects are discussed on the basis of experimental results. (author)