Lifetime measurements with a scanning positron microscope - art. no. 067402

First lifetime results obtained with a scanning positron microscope will be presented. A pulsed positron beam with a variable energy from 0.5 to 20 ke V, with a spot diameter of 2 mum, can be electronically scanned over an are a of 0.6 x 0.6 mm(2). This beam is formed after a double-stage stochastic c ooling (moderation) of positrons emitted from a radioactive isotope. Includ ed in the system is a conventional scanning electron microprobe for surface analysis. Three-dimensional positron lifetime spectra or a GaAs sample wit h a small surface scratch reveal the range due to the mechanical damage.