THE GRID SHADOW TECHNIQUE AS A TOOL FOR BEAM FOCUSING IN NUCLEAR MICROPROBES

A technique is presented which greatly facilitates the focusing of nuclear microprobe ion beams down to sizes of about one micrometer. It is based on the visual observation of the pattern created by the ion beam when impinging on a scintillating screen after first having passed through a 2000 mesh copper grid (grid period 12.7-mu-m) placed in the image plane. No additional electronic components or detectors are required. Apart from aiding the user in the focusing of the beam, the generated patterns give information concerning the quality of the ion beam focusing system and is therefore recommended as a permanent part of any nuclear microprobe setup.