Robustness test of a system of MSGC plus GEM detectors at the cyclotron facility of the Paul Scherrer institute

A system of detector modules consisting of a large size Gas Electron Multip lier (GEM), coupled to Micro Strip Gas Counters (MSGC, has been exposed to a pion beam at the Paul Scherrer Institute Cyclotron facility. As part of a CMS tracker milestone, the aim of this test was to investigate the robustn ess of such detectors when exposed to experimental conditions close to what is expected at the Large Hadron Collider (LHC) of CERN. Eighteen detector modules have been operated at voltage settings corresponding to 98% detecti on efficiency for Minimum Ionizing Particles during a period of 5 weeks. Sp arking rates and strip losses have been monitored throughout the exposure. An operation margin of at least a factor of three with respect to the requi red gas gain has been demonstrated. (C) 2001 Elsevier Science B.V. All righ ts reserved.