Scanning positron microbeam.

The construction and operation of a scanning positron microbeam is reported. The positrons are obtained from a doubly remoderated positron beam with a normalized brightness-per-volt of 1.8x10 sup 5 e sup + sec sup (-1) cm sup (-2) rad sup (-2) V sup (-1) Ci sup (-1). The beam of 8000e sup + sec sup (-1) is brought to a 10x50micron sup 2 focus by a sectored lens and is scanned across a test grid. Possible applications to defect spectroscopy and the observation of small samples will be discussed.