Equilibrium and non-equilibrium charge-state distributions of 2 MeV/u sulfur ions passing through carbon foils

Both equilibrium and non-equilibrium charge-state distributions for 2.0 MeV/u sulfur ions after passing through carbon foils were studied experimentally. For the equilibrium charge-state distribution, incident ions of S7+, S12+, S14+ and S16+ were injected into carbon foils 54, 98, 150 and 200 μg/cm2 in thickness, whereas for the non-equilibrium distributions, new measurements for S15+ and S16+ incidences were made through carbon foils of 0.9–10 μg/cm2 to supplement our previous experiments regarding S6+−S14+ incidences [M. Imai, M. Sataka, K. Kawatsura, K. Takahiro, K. Komaki, H. Shibata, H. Sugai, K. Nishio, Nucl. Instr. and Meth. B 230 (2005) 63; M. Imai, M. Sataka, K. Kawatsura, K. Takahiro, K. Komaki, H. Shibata, H. Sugai, K. Nishio, Nucl. Instr. and Meth. B 256 (2007) 11]. Mean charge states for S6+–S14+ incidences as functions of the penetration thickness merged at 6.9 μg/cm2 and changed together until reaching equilibrium at around 100 μg/cm2, while those for S15+ and S16+ incidences took different paths to equilibrium, which was also the case for distribution widths for S6+–S14+, S15+ and S16+ incidences. An equilibrium mean charge state of 12.68 and distribution width of 1.11 were attained with equilibrium charge distributions between 6+ and 16+.