Gas-pressure dependence of charge-state fractions and mean charges of 1.4Â MeV/u-uranium ions stripped in molecular hydrogen

Using a recently created BREIT computer code (Balance Rate Equations for Ion Transportation), evolutions of the charge-state fractions Fq(x) and equilibrium mean charge states q¯ are calculated for stripping of 1.4 MeV/u-U4+ ions in H2 gas for target thicknesses x⩽100 μg/cm2 (⩽3·1019molecule/cm2) and gas pressures 10-4⩽P⩽500 mbar. Calculations of the non-equilibrium Fq(x) and equilibrium Fq0 distributions for ion charges 4⩽q⩽40 are performed by solving the balance (rate) equations with account for the multi-electron processes and the target-density effect. Calculated equilibrium mean charge state increases from q¯≈27.6 at P=10-4 mbar to its saturated (maximum) value of q¯≈32.7 at pressures P≳250 mbar while the equilibrium target thickness xeq increases from 20 to 50 μg/cm2 (from 0.6 to 1.5 in units of 1019molecule/cm2) in the H2-pressure range considered. From the present calculations it is concluded that the maximum mean charge state q¯ which can be achieved in stripping of 1.4 MeV/u-U4+ ions in H2 gas is about q¯≈33 at a gas pressure P≳250 mbar.