Dependence of the performance of CsI-covered microstrip plate VUV photosensors on geometry: experimental results

The behavior of a xenon-filled microstrip gas chamber instrumented with a microstrip plate with eight different microstrip geometries is reported. The best energy resolution achieved for 5.9-keV and for 22.1-keV X-rays was 13.6% and 7.0%, respectively. The same microstrip plate covered with a CsI film was used in place of the photomultiplier tube to detect the vacuum ultraviolet scintillation light produced in a driftless xenon-filled gas proportional scintillation counter. The relative amplitude, energy resolution,. optical positive feedback, and photoelectron extraction efficiency are discussed. The energy resolution obtained for 5.9-keV X-rays was 11.4%, which is better than that achieved with a standard proportional counter, about 13% for argon based proportional counters.