Insensitive zones and space resolution of microdot (MDOT) detectors of 50, 100 and 200 micron pitch

Insensitive regions and spatial resolution of microdot (MDOT) detectors with 200 μm, 100 μm and 50 μm pitches were studied using a collimated X-ray beam as a probe. The insensitive zones measured by the probe-scan were compared with those estimated previously from the drift-voltage dependence of the count rate. The X-ray probe-scan along an isolated strip of a gauged linear array of MDOT anodes showed significant insensitive zones in the 200 μm pitch detector, but less in the 100 μm and 50 μm pitch detectors. The measured projected spatial widths were 80 μm, 55 μm and 51 μm for the 200 μm, 100 μm and 50 μm pitch detectors, respectively. Together with gain measurements made previously, these results suggest that 100 μm is the optimum pitch to minimize insensitive zones, and achieve good spatial resolution and good avalanche gain