Report on the CMS forward–backward MSGC milestone

The CMS MF1 milestone was set in order to evaluate system aspects of the CMS forward–backward MSGC tracker, to check the design and feasibility of mass production and to set up all assembly and test procedures. We describe the construction and the experiences gained with the operation of a complete system of 38 MSGC detectors assembled in six multi-substrate detector modules corresponding to the geometry of the forward–backward MSGC tracker in CMS. Corresponding to various possible designs, the detector modules were equipped with MSGCs mounted side by side without dead space (wall less ϕ crack) forming a continuous detector surface of about 0.2 m2. Operation conditions for these 38 MSGCs are reported from an exposure to a muon beam at the CERN SPS. Gain uniformity along the wedge-shaped strip pattern and across the detector modules will be shown.