The LHCb triple-GEM detector for the inner region of the first station of the muon system: construction and module-0 performance

A triple-gas electron multiplier (GEM) detector, operated with the gas mixture Ar/CO
₂
/CF
₄
(45/15/40), is going to equip station M1, region R1 of the LHCb muon system. A Module-0 of this detector, with full area (20 cmtimes24 cm) GEM foils, was recently built and tested. In this paper, new measurements of efficiency and pad multiplicity are presented. These new measurements were very important to select of the final pad board configuration. The sensitivity to discharges is a very important issue in this type of detector; we discuss here new measurements of the maximum number of discharges that a triple-GEM detector can stand before breakdown, and we show that detector operation in LHCb is safe from this point of view. We also discuss new measurements of the time performance of the detector in the presence of background radiation, indicating that no significant deterioration of the performances is expected in the LHCb environment