The Leak Microstructure detector as trigger and particle rejector of the STARTRACK experiment.

STARTRACK is a track nanodosimetry experiment the installation of which is in progress by the Legnaro Laboratories. The experiment aims to measure the ionisation cluster distributions occurring in a nanometric site placed at a given distance from single charged particle track. Therefore, the accuracy of STARTRACK experimental data depends on the possibility of rejecting with high efficiency ionisation events due to more than I primary particle. To accomplish this task, an efficient particle detection system made of a trigger and a rejector is necessary. As the simulation of nanometric sites is performed working at very low gas pressure (a few mbar), the trigger and the rejector operate at the same low gas pressure. In order to see if a Leak Microstructure (LM) detector can be used as rejector as well as trigger of STARTRACK, alpha particle detection measurements have been performed at low gas pressure (2-3 mbar) of propane. Experimental data shows that the LM detector works in proportional mode down to 2 mbar of propane with high gas gain. The gas gain is high enough to allow for measuring single electron events due to the passage of low-ionising charged particles.