Energy losses and straggling of light ions transmitted through thin carbon foils

Abstract

The energy losses of 10 MeV/amu 3 He 2+,1+ , 6 Li 3+,2+ , 12 C 6+,5+,4+ and 16 O 8+,7+,6+,5+ ions passing through carbon foils of 5–110 μg/cm 2 in thickness were measured with a high resolution magnetic spectrograph. The measurement was carried out for ions emerging from foils in the same charge state as the incident beam. The measured fixed-charge stopping powers have been reported in our previous papers. In this paper, the energy loss straggling of partially clothed ions in the charge-state nonequilibrium region is reported for the first time. A double peak structure in energy loss spectra of 3 He 1+ and 6 Li 2+ ions transmitted through carbon foils of 40–50 μg/cm 2, which is due to charge changing contributions, was also described before. The present study shows that these contributions also bring about a characteristic behavior in the foil thickness dependence of the straggling values. For partially clothed C and O ions, a linear relation between the foil thickness and the straggling does not hold in the thicker foil region and the straggling exhibits an abrupt increase, although the double peak structure did not appear in the energy loss spectra. A Monte Carlo simulation taking account of the charge exchange can well reproduce the energy loss straggling of 3 He 1+ and 6 Li 2+ emerging from thicker foils.