Neutral fraction of ions penetrated through a thin aluminum foil at small-angle incidence of fast protons

Dependence of the neutral fractions contained in the foil-transmitted 0.6 M eV H+ ion beams on the angle of incidence (2.5-90 degree) has been measured at the beam direction: when (0.6-1) MeV H+ ions are impinged on a poly-cry stalline Al thin foil. The fraction for ions of the same exit-energy decrea ses slightly with the decreasing angle of incidence. The dependence on the angle of incidence is calculated with a classical model for charge-exchange s with a modification taking into account the topological effect of the exi t-surface of the foil. The surface is observed by a three-dimensional-profi le microscope and the parameters of the surface roughness are obtained. The observed parameters are consistent with those calculated from the surface topology assumed to obtain the neutral fractions comparable to the measured ones.