The München scanning positron microscope

For the first time a scanning positron microscope (SPM) using a pulsed positron beam for the nondestructive, three-dimensionally resolved investigation of defect distributions has been constructed. A positron beam with variable energy from 0.5 to 30 keV, with a spot diameter of 1 μm or below, can be scanned over an area of 0.6 × 0.6 mm2. Beam pulsing enables positron lifetime studies with a time resolution of 200 ps FWHM. The beam is formed by double stage stochastic cooling (moderation) of the positrons emitted from a radioactive isotope. Included in the system is a conventional scanning electron microprobe for easy alignment of the optical column and for surface analysis. The design of the entire SPM is determined by the special demands of positron physics, which are discussed briefly.