A CONCEPT OF A SCANNING POSITRON MICROSCOPE

The concept of a scanning positron microscope which is under construct ion in Munchen and Trento will be shown. A beam with a variable energy from 1 to 30 keV and a spot diameter of 1 mu m, which can be scanned over an area of (0.6 x 0.6) mm(2), is formed after a double stage stoc hastic cooling of the positrons emitted from a radioactive source. Add itionally, the beam will be pulsed to have a well-defined time base fo r positron lifetime measurements. The design of the microscope is domi nated by special demands of positron physics. Therefore, the microscop e contains electron optical elements which are well known but rarely u sed. These are the through the lens reflection remoderator and the opt ical column with a magnetic side gap lens as probe forming lens.