LABORATORI NAZIONALI DI LEGNARO
AIT Austrian Institute of Technology, Department Health and Environment, A-1220 Vienna, Austria Radiation-induced damage to living cells or genes is governed, to the greater part, by the clustering of inelastic interactions of ionizing particles in sub-cellular targets (segments of the DNA, nucleosomes, or segments of the chromosome fibre). The effectiveness of ionizing radiation for damaging is, therefore, directly related to the track structure of ionizing radiation in matter, which cannot be described satisfactorily by macroscopic quantities like absorbed dose and linear energy transfer (LET). To facilitate the understanding of radiation induced damage to nanometre sized target volumes from the physical point of view, general properties of particle track structure are discussed in the framework of the properties of Coulomb interactions in matter. Here, particular emphasis is laid on ionization clustering due to electrons, protons, 4He-ions, 12C-ions, and 20Ne-ions in liquid water as a substitute of biological material.