Utilization of a thin columnar cesium iodide (CsI) layer in gas avalanche microdetector

A thin (200–300 μm) layer of columnar cesium iodide (CsI) crystals has been coupled to a conventional microstrip gas chamber. This layer provides the dominant source of electron production by incident charged particles in gas avalanche microdetectors, and is expected to make a significant improvement in spatial and time resolution, and detection efficiency, with respect to particleʹs angle of incidence. The CsI layer also makes the chamber useful for X- or γ-ray detection with good position accuracy. In this paper, measurements are presented of signal enhancement due to the columnar CsI layer, and the efficiency versus angle.