Probe for measuring ion beam angular distribution

Abstract

Low energy ion beam mixing as a tool for multilayer xray mirror fabricationA new type of ion beam probe is described that measures the angular distribution of energetic ions and, through their sputtering effects, energetic neutrals as well. This probe does not require either complicated motion actuators or very sensitive electrical measurements in the adverse environment of an ion beam, but instead performs the measurement 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 Ϯ0.3 deg. After use, the probe sample provides a permanent record of the angular distribution of the ion beam at the target location tested. Because no electrical contacts 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, the low divergence and paraxial beam from an ion source with 30 cm flat graphite grids were documented. This probe, in conjunction with profiles 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 minimum divergences obtained from earlier tests with small arrays of apertures.

Fast (tens to hundreds of eV) neutral beams for materials processing

“…An indirect measurement was performed by Yunogami et al [13] who measured the angular divergence of the residual ions emanating from the neutral beam source. Also, a rough idea of the beam divergence may be obtained by measuring the etch rate drop off as a function of distance from the neutralization grid [26] or by using techniques applied to ion beams [82]. In principle, the fast neutral beam may be ionized (using an electron beam) and the ion current measured as a function of (angular) position.…”