Digital characterisation of particle tracks for microdosimetry

Work is in progress to develop a digital approach to microdosimetry and to construct a prototype instrument to obtain digital information about charged particle tracks. The objective of such a device is to measure the numbers of electrons produced in various sub-volumes of a chamber gas along a particle's path. Results of Monte Carlo calculations of charged particle tracks in a cubical time-projection ionisation chamber containing methane are presented. Results are presented to show the effects of electron diffusion during charge collection. The calculations indicate that the optimum ratio of field strength and pressure is about 0.6 V.cm-1 tor-1. Examples of proton, carbon ion, and electron tracks are shown. (author)