High granularity tracker based on a Triple-GEM optically read by a CMOS-based camera

摘要

The detection of photons produced during the avalanche development in gaschambers has been the subject of detailed studies in the past. The greatprogresses achieved in last years in the performance of micro-pattern gasdetectors on one side and of photo-sensors on the other provide the possibilityof making high granularity and very sensitive particle trackers. In this paper,the results obtained with a triple-GEM structure read-out by a CMOS basedsensor are described. The use of an He/CF$_4$ (60/40) gas mixture and adetailed optimization of the electric fields made possible to obtain and veryhigh GEM light yield. About 80 photons per primary electron were detected bythe sensor resulting in a very good capability of tracking both muons fromcosmic rays and electrons from natural radioactivity.