Author/Authors :
Thers، نويسنده , , D and Abbon، نويسنده , , Ph. and Ball، نويسنده , , J and Bedfer، نويسنده , , Y and Bernet، نويسنده , , C and Carasco، نويسنده , , C and Delagnes، نويسنده , , E and Durand، نويسنده , , D and Faivre، نويسنده , , J.-C and Fonvieille، نويسنده , , H and Giganon، نويسنده , , A and Kunne، نويسنده , , F and Goff، نويسنده , , J.M.Le and Lehar، نويسنده , , F and Magnon، نويسنده , , A and Neyret، نويسنده , , D and Pasquetto، نويسنده , , E and Pereira، نويسنده , , H and Platchkov، نويسنده , , S and Poisson، نويسنده , , E and Rebourgeard، نويسنده , , Ph، نويسنده ,
Abstract :
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–C2H6–CF4 gas mixture, was demonstrated in a set of beam tests performed on a 26×36 cm2 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.
