CONSTRUCTION, TEST AND OPERATION IN A HIGH-INTENSITY BEAM OF A SMALL SYSTEM OF MICRO-STRIP GAS-CHAMBERS

We describe the construction, test and installation procedures, and th e experience gained with the operation of a small but complete system of high-rate Micro-Strip Gas Chambers, made on thin borosilicate glass with a diamond-like coating with chromium or gold strips. A set of de tectors, fully equipped with read-out electronics and each with an act ive area of 100 x 100 mm(2), was exposed during six months to a high-i ntensity muon beam at CERN with a peak intensity of similar to 10(4) m m(-2) s(-1). Continuous monitoring of the performance of the chambers during the beam runs allowed the evaluation of detection efficiency an d the monitoring of accidental rates, as well as the study of ambient induced variations and aging in realistic beam conditions. No signific ant difference has been found in the operation of under-and over-coate d plates. Efficiencies could reach similar to 98% in best operating co nditions, although local lower values were often observed due to missi ng channels (open strips, broken bonds and dead electronic channels). The long-term operation of the chambers has been more difficult than e xpected, with the appearance of break-downs and loss of efficiency in some detectors, possibly induced by the presence of small gas leaks, t o water permeation or to residual reactivity of the quencher gas (dime thylether). (C) 1998 Elsevier Science B.V. All rights reserved.