OPTIMIZATION OF ANODE DIMENSIONS FOR MICROGAP DETECTORS AT HIGH-PRESSURE

The possibility of using microgap structures in pressurized gaseous de vices 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 pe rformance of microgap plates with several widths of the anodes (4 to 1 2 micron) and of the insulating layer (6 to 30 micron). Krypton and xe non based gaseous mixtures were used at pressures of 1, 3 and 6 bar un der irradiation by Fe-55 and Cd-109 X-ray sources and an Xray tube. Th e dependence of gain on anode voltage is analyzed, as well as the effe cts of drift field on gain and charge collection. We also present data on measured safe maximum gain before breakdown versus count rate.