Operation of a large GEM-MSGC detector in a high intensity hadronic test beam using fully pipelined readout electronics

98-060 In a recent test beam experiment at PSI a new tracking device for very high particle fluxes consisting of a low gain micro strip gas chamber (MSGC) combined with a gas electron multiplier (GEM) foil has been run under beam conditions similar to those foreseen in the HERA-B experiment [1], where such devices are being installed for the inner tracker. They are also being evaluated for the LHCb experiment [2]. In both detectors very high, mainly hadronic particle densities (up to 10 4 mm -2 sec -1) are expected, while the momentum resolution of the magnetic spectrometers foreseen in the two experiments is limited by multiple scattering. Also photon conversions represent a significant background source and therefore a minimal thickness in terms of radiation length is important, while position resolution requirements are moderate (typically 300 mu m pitch is sufficient). This paper describes the detailed construction of this novel detector, the test beam configuration and some of the data taken using the full HERA-B readout electronics.