Characterisation of an ultra-miniature counter for Microdosimetric measurements in a therapeutic 400 MeV/A Carbon beam.

Single event spectra of a clinical carbon beam have been measured by an ultra-miniature tissure-equivalent proportional counter (UMC). In order to cover the energy range of the Bragg peak, the incident energy of the carbon beam was degraded by aluminium plates. Single event spectra for carbon-events incident to the UMC were analysed and selected at several carbon energies using thin scintillation counters. It was found that the dose weighted lineal energy distributions have a doublet peak structure due to incident carbon beam and fragment contributions