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 wit h 200 mu m, 100 mu m, and 50 mu m pitches were; studied using a collimated X-ray beam as a probe. The insensitive: zones measured by the probe-scan we re compared with those estimated previously from the drift-voltage dependen ce of the count rate. The X-ray probe-scan along an isolated strip of a ganged linear array; of M DOT anodes showed significant insensitive zones in the 200 mu m pitch detec tor, but less in the 100 mu m and 50 mu m pitch detectors. The measured pro jected spatial widths were 80 mu m, 55 mu m, and 51 mu m for the 200 mu m, 100 mu m, and 50 mu m pitch detectors, respectively. Together with gain mea surements made previously, these results suggest that 100 mu m is the optim um pitch to minimize insensitive zones, and achieve good spatial resolution and good avalanche gain.