PROBE FOR MEASURING ION-BEAM ANGULAR-DISTRIBUTION

A new type of ion beam probe is described that measures the angular di stribution of energetic ions and, through their sputtering effects, en ergetic neutrals as well. This probe does not require either complicat ed motion actuators or very sensitive electrical measurements in the a dverse environment of an ion beam, but instead performs the measuremen t through the sputter etching of a multilayer sample with contrasting metal colors. This probe was tested and found to provide a half-width at half-maximum reproducibility of about +/-0.3 deg. After use, the pr obe sample provides a permanent record of the angular distribution of the ion beam at the target location tested. Because no electrical cont acts are required, the probe can even be attached to a moving stage to measure the effective angular distribution of an ion beam while being carried through a complicated planetary pattern. Using this probe, th e low divergence and paraxial beam from an ion source with 30 cm flat graphite grids were documented. This probe, in conjunction with profil es obtained with a Faraday probe, allows full global and internal ion beam characterization. It is significant that the minimum divergences obtained in this investigation were 40-60 percent lower than the minim um divergences obtained from earlier tests with small arrays of apertu res. (C) 1996 American Vacuum Society.