Effect of beam steering on aberration coefficients measured at the Argonne National Laboratory neutral particle beam test stand

A pinhole diagnostics system has been used to measure beam aberrations as a function of steering angle for an expanded beam at the ANL Neutral Particulate Beam Test Stand. The experiment began with a low-abberation unsteered beam. The horizontal steering angle was varied through the range {plus minus}3.5 mrad, and the vertical steering angle varied though the range {plus minus}1.0 mrad. Systematic variations in the dependence of the various aberration coefficients on steering angle were found well above their respective uncertainty levels. Plots are presented showing the dependence of aberration coefficients on steering angle. Certain pairs of coefficients which are related by symplectic constraint equations from canonical coordinate transformations show similar variations with steering angle. 2 refs., 4 figs