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

Insensitive regions and spatial resolution of the microdot (MDOT) detectors having 200 μm, 100 μm, and 50 μm pitches were studied using a collimated X-ray 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 variation. The X-ray probe scan was done along an isolated strip of a ganged linear array of MDOT anodes, and this showed the existence of insensitive zones in the 200 μm pitch detector. However, we did not observe these in the in the 100 μm and 50 μm pitch detectors. The spatial resolution, indicated by the standard deviation of the fitted Gaussian distribution of scanning signals across the anode strip, was determined to be 80 μm, 55 μm, and 51 μm for the 200 Gun, 100 μm, and 50 μm pitch detectors, respectively. Therefore, the 100 μm was determined to be the optimum pitch for absence of the insensitive zones, good spatial resolution, and good avalanche gain