DEVELOPMENT OF MICROSTRIP GAS-CHAMBERS ON SUBSTRATA WITH ELECTRONIC CONDUCTIVITY

This paper describes several recent developments on Microstrip Gas Cha mbers (MSGCs). We have studied the operating behaviour of the detector s in different gas mixtures; maximum stable gains have been achieved i n mixtures of argon and dimethyl-ether (DME) in almost equal proportio ns. Using detectors manufactured on semi-conducting glass substrates, capable of withstanding very high rates (above 10(6) mm-2s-1), we have demonstrated extended lifetime without gain modifications up to a col lected charge of 130 mC cm-1 in clean laboratory operating conditions. We have also verified that relaxing the requirements on cleanness con ditions, either in the gas mixing system or in the detector constructi on, may result in fast ageing of the devices under irradiation. As an alternative to the semi-conducting glass, we have developed a novel te chnique to coat regular glass with a thin lead silicate layer having e lectron conductivity; a new development consisting in coating already manufactured MSGCs with the thin semi-conducting layer is also describ ed. The preliminary results show an excellent rate capability for this kind of devices, intrinsically simpler to manufacture.