Track-structure investigations: A supplement to microdosimetry

We conceived and developed an experimental apparatus able to measure the track structure (the spatial distribution of the points of ionizing collisions) of light ions, allowing the investigation of the track-core and penumbra regions separately. The device is based on single-electron counting technique, and simulates a target volume V of about 20 nm in diameter that can be moved with respect to a narrow primary particle beam, allowing the measurement of the ionization-cluster-size distribution as a function of the impact parameter. The experimental set up is mounted at the Tandem-Alpi LNL particle accelerator complex. The goal of the experiment is to investigate the formation of ionization-cluster-size distributions caused in a nanometre-sized volume by different light ions of medical interest (protons, lithium ions and carbon ions), when penetrating through or passing by the target volume at a specified distance.