Energy losses and straggling of 10 MeV/amu C5+,4+ ions in charge state non-equilibrium region

It was found that the energy loss straggling of 10 MeV/amu 3He1+ and 6Li2+ ions transmitted through thin carbon foils exhibits a bump structure at the foil-thickness region where the charge-changed H-like component becomes comparable to the frozen-charged one. This characteristic behavior could be reproduced well by a Monte Carlo simulation taking account of the electron loss and capture processes. An abrupt increase of the straggling values were also observed for 12C5+ and 12C4+. In order to improve a quantitative understanding, not only the attenuation of H-like and He-like beams as a function of the foil thickness but also the electron-captured fractions for the incidence of bare and H-like beams have been measured and charge changing cross sections among the bare, H-like and He-like charge states are evaluated. A computer simulation taking account of charge exchanges can reproduce quite well the measured energy losses and straggling of partially clothed C ions in the thicker foils.