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  • Micromegas as a large micro...
    Thers, D; Abbon, Ph; Ball, J; Bedfer, Y; Bernet, C; Carasco, C; Delagnes, E; Durand, D; Faivre, J.-C; Fonvieille, H; Giganon, A; Kunne, F; Goff, J.-M.Le; Lehar, F; Magnon, A; Neyret, D; Pasquetto, E; Pereira, H; Platchkov, S; Poisson, E; Rebourgeard, Ph

    Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 08/2001, Volume: 469, Issue: 2
    Journal Article

    Recent results on the gaseous microstrip detector Micromegas which will be used to track particles in the COMPASS experiment at CERN are presented. Developments concerning its mechanical and electrical design, associated readout electronics and gas mixture were carried out. Particular attention was paid to the discharge phenomenon which affects this type of microstrip detector. The adequacy of the options finally retained, especially the SFE16 readout and the use of a Ne–C 2H 6–CF 4 gas mixture, was demonstrated in a set of beam tests performed on a 26×36 cm 2 prototype. Operating at a gain of ∼6400, full efficiency is reached along with a spatial resolution of ∼50 μm and a timing accuracy of 8.5 ns . Discharges are kept at a low rate, less than one per SPS spill in a COMPASS-like environment. Via a decoupling of the strips through individual capacitors their impact is greatly reduced. They generate a dead time on the full detector of ∼ 3 ms , affecting marginally the detection efficiency given their rate. The probability of discharge, at a given value of efficiency, is found to decrease with the mean value of the gas mixture atomic number. In view of these results, the commissioning of Micromegas for COMPASS is foreseen in the near future.