Performance of large pixelised Micromegas detectors in the COMPASS environment
Résumé
New large-size Micromegas detectors are being developed for the future physics program
of the COMPASS experiment at CERN. These detectors will have a pixelised readout in their
center to detect particles in the beam region, where the particle flux can reach several MHz/cm2 in
nominal conditions, and will have to handle high intensity hadron beams (up to a few 107 hadrons/s)
with a discharge rate lower than 0.01 to 0.001 discharge/s. Several prototypes with two different
discharge rate reduction technologies (preamplification stage with a GEM foil and resistive readout
with buried resistors) have been studied in the COMPASS beam since 2010. Four of them
have been included in the spectrometer since 2012, and have been used for the track reconstruction.
Their performance (detection efficiency, space and time resolutions, and discharge rates) for
different beam intensities and magnetic fields environments are presented. These detectors play
an important role in the track reconstruction at very small angle; their impact is presented, with a
particular emphasis on the effect of the background reduction due to an improved cluster selection.