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+.