Emergent-angle-dependent charge-state distributions of 2-MeV He-4 transmitted through a thin carbon foil - art. no. 032717

The emergent-angle-dependent charge-state fractions of 2-MeV He-4 transmitt ed in a carbon foil of 2.5 mu g/cm(2) in thickness have been measured in th e range from 0 to 8 mrad. The angular distribution due to multiple scatteri ng has been also obtained for each outgoing charge state. Up to the angle o f similar to 4 mrad, both the neutral and singly charged fractions increase with increasing the emergent angle. This trend is more remarkable in the n eutral fraction. At the larger angles, these fractions reach saturated valu es. The observed behavior can be explained qualitatively by the impact para meter dependence of the charge-exchange probabilities. Although a Monte Car lo simulation can reproduce the obtained angle-dependent charge-state fract ions, it gives a slightly narrower angular distribution due to multiple sca ttering for each outgoing charge state.