A new multi-grid type MSGC with pad readout

Abstract

Recently, a new multi-grid type MSGC has been proposed. Between the anode and the cathode, additional grid strips are placed in this new type of MSGC. Gaps between these strips are chosen to be around 10 μm which assure efficient removal of surface charges which even do not need the lower surface resistivity and bare glass can be used up to 10 6 cps/ mm 2 . Another feature of the MSGC is its high gain capability. Owing to the existence of other strips of lower potentials, the field strength around the opposing grid to the anode strip is not so high as conventional small gap detectors. Furthermore, the contribution of the surface streamer is greatly suppressed because the electric field parallel to the surface is screened by the intermediate grid electrodes. However, the existence of additional electrodes also screens all the electric field upper than the substrate and we cannot observe induced signals from backside of the substrate. To overcome the difficulty, we propose another signal readout method using patterning approach. Floating pads are placed close to the cathode strip on the surface of the M-MSGC and induced charges are read out via the pads. If the area of pads is sufficiently large and the positive charges are moving toward the pads, backside electrodes can sense the induced charge. Collected charges on the pads are leaked through the surface resistivity. The basic experiment has been performed and the readout of the position along the cathode strips is successfully ensured.