Optimization of anode dimensions for microgap detectors at high pressure

The possibility of using microgap structures in pressurized gaseous devices for high rate synchrotron radiation detectors has been presented before; one of their main drawbacks is the limited maximum safe gain at which they can be operated. In this study we present data on the performance of microgap plates with several widths of the anodes (4 to 12 micron) and of the insulating layer (6 to 30 micron). Krypton and xenon based gaseous mixtures were used at pressures of 1, 3 and 6 bar under irradiation by ⁵⁵Fe and ¹⁰⁹Cd X-ray sources and an X-ray tube. The dependence of gain on anode voltage is analyzed, as well as the effects of drift field on gain and charge collection. We also present data on the measured safe maximum gain before breakdown versus count rate