Performance of large pixelised Micromegas detectors in the COMPASS environment

New large-size Micromegas detectors are being developed forthe future physics program of the COMPASS experiment at CERN. Thesedetectors will have a pixelised readout in their center to detectparticles in the beam region, where the particle flux can reachseveral MHz/cm2 in nominal conditions, and will have to handlehigh intensity hadron beams (up to a few 107 hadrons/s) with adischarge rate lower than 0.01 to 0.001 discharge/s. Severalprototypes with two different discharge rate reduction technologies(preamplification stage with a GEM foil and resistive readout withburied resistors) have been studied in the COMPASS beam since 2010.Four of them have been included in the spectrometer since 2012, andhave been used for the track reconstruction. Their performance(detection efficiency, space and time resolutions, and dischargerates) for different beam intensities and magnetic fieldsenvironments are presented. These detectors play an important rolein the track reconstruction at very small angle; their impact ispresented, with a particular emphasis on the effect of thebackground reduction due to an improved cluster selection.