IONIZATION MEASUREMENTS IN SMALL GAS SAMPLES BY SINGLE-ION COUNTING

A new method for highly efficient measurements of the ionization stati stics in small, wall-less, well-defined low density gas samples is pro posed. It is based on counting ions, induced by radiation in a sensiti ve gas volume. The high resolution permits the measurement of spatial correlations between the number of ions induced in two distanced small sensitive volumes. Using tissue- or solid-equivalent gases, the metho d allows the accurate determination of the ionization statistics in th e corresponding sub-nanometer volume of condensed matter. These data a re of relevance to the modeling of microscopic phenomena related to th e interaction of radiation with matter, such as in nanodosimetry and s tudies of radiation damage to solid state devices.