We describe recent observations and measurements realized with microdot (MDOT) detectors having 50 mm, 100 mm, and 200 mm pitches for 3.7 keV X-rays. A gas gain of 3.1×103 has been measured with 50 mm pitch MDOT at potential difference much lower than those usually obtained with MSGCs. The defocusing effect caused by the existence of the readout lines passing below the insulator layer has been investigated from the drift voltage dependence of the count rate variation and the electric field simulation for all the detectors. Results concerning the spatial resolutions are presented with collimated X-ray beams.

• Hyosung Cho(Department of Radiological Science, Yonsei University)
• Bongsoo Lee(School of Biomedical Engineering, Konkuk University)
• Sin Kim(Department of Nuclear and Energy Engineering, Cheju National University)