FIRST BEAM TEST-RESULTS WITH MICROMEGAS, A HIGH-RATE, HIGH-RESOLUTIONDETECTOR

We present particle beam test results using a high-rate, high-position and high-time-resolution gaseous detector, 'Micromegas', of 15 x 15 c m(2). The rate capability was measured with 10 MeV protons from a TAND EM accelerator. No effect on gain was observed at particle rates up to 10(9) mm(-2) s(-1). With an argon and DME filling the gain was stable up to 50 mC total charge on a 3 mm(2) area. With minimum-ionizing par ticles in a CERN beam a high efficiency, close to 100%, was measured, under stable conditions. A first space-resolution measurement of 50 mu m +/- 20 mu m was obtained. The operation of the chamber shows that i t is possible to optimize the geometrical parameters in order to impro ve the space resolution and bring the time resolution low enough to co ntain the events of each beam crossing (every 25 ns) in the European L arge Hadron Collider. Further work in this direction is being actively pursued. (C) 1998 Published by Elsevier Science B.V. All rights reser ved.