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

作者：Shevelko V P^*; Winckler N; Tolstikhina I Yu

来源：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms , 2016, 377: 77-82.

DOI：10.1016/j.nimb.2016.04.025

• Charge-changing cross sections
• Equilibrium mean charge state
• Evolutions of charge-state fractions

Using a recently created BREIT computer code (Balance Rate Equations for Ion Transportation), evolutions of the charge-state fractions F-q(x) and equilibrium mean charge states (q) over bar are calculated for stripping of 1.4 MeV/u-U4+ ions in H-2 gas for target thicknesses x <= 100 mu g/cm(2) (<= 3 . 10(19) molecule/cm(2)) and gas pressures 10(-4) <= P <= 500 mbar. Calculations of the non-equilibrium F-q(x) and equilibrium F-q(0) 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) over bar approximate to 27.6 at P = 10(-4) mbar to its saturated (maximum) value of (q) over bar approximate to 32.7 at pressures P greater than or similar to 250 mbar while the equilibrium target thickness chi(eq) increases from 20 to 50 mu g/cm(2) (from 0.6 to 1.5 in units of 10(19) molecule/cm(2)) in the H-2-pressure range considered. From the present calculations it is concluded that the maximum mean charge state (q) over bar which can be achieved in stripping of 1.4 MeV/u-U4+ ions in H-2 gas is about (q) over bar approximate to 33 at a gas pressure P greater than or similar to 250 mbar.

• 出版日期2016-6-15