Development of a multi-grid-type microstrip gas chamber for synchrotron radiation applications and spallation neutron sources

Conventional MicroStrip Gas Chambers (MSGCs) have encountered many difficulties such as limited gas gain, spark-induced damage, etc. We have proposed a new multi-grid-type MSGC (M-MSGC) to overcome some of these difficulties. Additional grid strips are inserted between the anode and the cathode in this new design. Gaps between these strips are chosen to be as small as 10 μm where one can expect an efficient removal of the surface charge. However, additional electrodes also screen all the electric field of the upper part of the substrate and we cannot observe induced signals from the backside of the substrate. To overcome the difficulty, floating pads are placed close to the cathode strip on the surface of the M-MSGC, and the induced charges are read out through these pads. If the area of pads is sufficiently large and the positive charges are moving toward the pads, the backside electrodes can sense the induced charge. Although the induced charge is spread out over several rear strips, position sensing along the anode strips has been achieved. Another approach is considered to use only the front electrodes. A test plate has shown a position resolution of 1.3 mm for the axis along the anode strip.