A tunable collimator for precision irradiation with ion microbeams

We describe a cheap yet effective beam collimation system capable of providing square apertures from 1mm down to about 10μm. The tunable part is driven by two manual micrometers, one controlling the shape the other the size, which could be immediately replaced by high precision stepping motors should remote control be needed. The aperture was calibrated by means of a simple home-made laser diffraction system which allows a considerable precision. The collimation system was used to produce low-divergence beams of oxygen and protons, in order to test the position sensitivity of a silicon microstrip telescope detector.