DIAMOND OVER-COATED MICROSTRIP GAS-CHAMBERS FOR HIGH-RATE OPERATION

We describe recent developments on diamond-like carbon (DLC) over-coat ed Microstrip Gas Chambers made on bore-silicate drawn glass substrate s. MSGC surface coating with thin DLC layer of stable and controlled r esistivity was proposed to overcome the limitation of detector operati on due to surface charging-up under avalanches. This brings also advan tages for the detector manufacturing technology. The thin layer, depos ited on top of a manufactured MSGC (over-coating), demonstrates excell ent mechanical properties and very good stability. We report on recent measurements with DLC over-coated MSGCs of various surface resistivit ies (ranging from 10(13) Ohm/square to 10(16)Ohm/square) on D-263 and AF45 glass substrates. Over-coated MSGCs with resistivity of the surfa ce around 10(15) Ohm/square exhibit a stable charge gain up to radiati on rates in excess of 10(6) Hz/mm(2). Stable long-term operation up to 50 mC/cm of accumulated charge from avalanches has been demonstrated.