Large scale test of MSGC+GEM detectors in a high intensity hadron beam

A large array of MSGC+GEM detector modules with a total area of 0.72 m2 has been exposed to a beam of 350 MeV/c pions at an intensity of at least 4×103 Hz/mm2 during 490 h. Eighteen detector modules have been operated at voltage settings corresponding to a 98% detection efficiency for Minimum Ionizing Particles (MIPS) with signal to noise ratio above 34. Discharges induced on MSGC substrates and GEM by heavily ionizing particles were recorded at a tolerable rate. They lead to the loss of 22 channels out of 16 384. At the end of the test the detectors were brought to a S/N⩾100 without significant increase of the sparking rate.