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The STARTRACK experiment : first measurements

STARTRACK experiment (acronym of STructure of hAdRonic TRACK) aims to measure ionisation cluster distributions in nanometric sites placed at different distances from an accelerated charged particle track. STARTRACK uses a 20 nm wall-less detector [1], already used for studying the nanometric track structure of a Cm alpha particle [2], and then it will use a new detector designed for measuring ionisation clusters in 10 nm sites. The experiment is mounted at the beam line of the Tandem-Alpi accelerator facility of Legnaro Laboratories, which supplies ion beams from hydrogen to gold in the energy range of 7-28 MeV/amu. Track nanodosimetry aims to measure ionisation clusters along and aside the ion track down to occurrence probability of 10. To reach such an aim at least 10 events have to be collected and the cluster pile-up probability reduced to less than 10. By using a beam profile detector, which is sensible to very weak currents, and an event rejector counter, such an aim is feasible. This paper is concerned with the preliminary measurements achieved with the new apparatus.