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 /spl mu/m, 100 /spl mu/m, and 50 /spl mu/m 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 /spl mu/m pitch detector. However, we did not observe these in the in the 100 /spl mu/m and 50 /spl mu/m 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 /spl mu/m, 55 /spl mu/m, and 51 /spl mu/m for the 200 Gun, 100 /spl mu/m, and 50 /spl mu/m pitch detectors, respectively. Therefore, the 100 /spl mu/m was determined to be the optimum pitch for absence of the insensitive zones, good spatial resolution, and good avalanche gain.