Study of GEM characteristics for application in a MicroTPC

The gas electron multiplier (GEM) may provide a convenient method for obtaining significant electron multiplication over large detector areas. An important potential application of the GEM is in microTPCs. We are conducting a study of a multi-GEM structure with particular emphasis on the following characteristics: gain uniformity/stability, ion feedback, and position readout. In particular, we present the first experimental results of interpolating anode pad readout. Initial results provide encouragement that the GEM application in microTPCs may be realized.