Study on a charge-integrating operation mode of M-MSGC towards very fine-pitch MSGC

We are exploring a new possibility of MicroStrip gas Counters (MSGCs) based on our original multi-grid-type electrode structure for very high counting rate applications at a synchrotron radiation facility. Because most surface of the multi-grid-type MSGC plate is covered with metal strips, we can expect a very high counting rate detector with a charge-integrating readout method. We have used an individual readout circuit and connected each cathode strip to the corresponding input channel of charge-integrating ASICs. The detector system has shown a good linearity more than 1010 cps/mm2. However, we also found nonlinear behaviors that are mainly due to the space charge effects. To overcome these nonlinear effects, we tried to develop a very fine-pitch MSGC to enlarge an avalanche region per unit area. We fabricated an M-MSGC with the anode pitch of 80 μm and the anode width of 2 μm. A single anode version of this electrode structure showed a pulse height spectrum of a 55Fe source and a plate with multiple strips was successfully fabricated and operated.