"Trion" code for radiation action calculations and its application in microdosimetry and radiobiology.

A code for calculations of electron, ion and photon radiation action on tissue-equivalent matter (water vapor) by the Monte Carlo technique is presented. The new "fluctuation detector" method is efficient in evaluating of probability distributions and moments of absorbed energy and number of ionizations in small sites. Spatial and energy distributions of particles fluences and fluctuation characteristics of radiation action on spherical and thread-like sites of nanometer diameter are compared with various experimental and theoretical data and discussed. Non-equivalence of energy absorption and ionization events and consequences of that non-equivalence are numerically analysed. As an example of radiobiological application the yield of single- and double-strand breaks of DNA is calculated in a threshold model.