Numerical modelling of tissue-equivalent proportional counters

In this paper a survey is given particles inside a TEPC. The first parr is devoted to the description of the general concept of particle transport calculations. Thereafter, the different methods available to study transport phenomena and energy deposition in the sensitive volume and in counter walls are described. Finally, the basic ionisation mechanisms which may occur in a counter are described, and the nonequilibrium phenomena which play an important role mainly for counters that are to be used in measurements at the nanodosemeter level are studied.