Charge-state measurements of backscattered ions from Au films

A small electrostatic accelerator (65 kV) was built as a postaccelerator for measuring the charge-state fractions of ions backscattered from solid or gas targets. A new method is described in which the charge-state fractions of 3He, 4He, /sup 12/C, /sup 14/N, and /sup 16/O ions backscattered from gold films are determined simultaneously. The added features in this work are the facts that the method can be efficiently used for low-energy incident ions and that spectra could be measured, compared, and analyzed by minimizing uncertainties inherent in experimental parameters. The energy dependence of the charge-state fractions of 3He, 4He, and /sup 12/C ions are measured between 3 MeV and 150 keV. The /sup 12/C charge-state-fraction data nicely fit the Gaussian model but none of the chi2 models. The mean ion charge i/sub m/ and the standard deviation s are also measured. Preliminary measurements of the dependence of the charge-state fractions on target thickness are also discussed