Multiple ionisation of rare gases by high-energy uranium ions

Multiple ionisation cross sections sigma (q) for the production of recoil ions in charge state q by 120 MeV u^-1 U⁹⁰⁺ impact have been measured for Ne, Ar and Kr targets using a recoil-ion-projectile-electron triple-coincidence technique. The data are compared with previously measured cross sections for U-ion impact in the projectile energy (E_p) range from 1.4 to 420 MeV u^-1. For low recoil-ion charge states sigma (q) decreases over the whole E_p range somewhat more slowly than 1/E_p, whereas for higher recoil-ion charge states sigma (q) reaches a maximum at about 10-15 MeV u^-1. The data are nicely described by parameter-free n-body Classical Trajectory Monte Carlo (nCTMC) calculations. The calculations indicate the importance of accounting for the Auger events in the description of the multiple ionisation process. Because of the smooth E_p dependence of sigma (q) towards high E_p, the development of a recoil-ion source using a primary U-ion beam in the storage ring for the production of high charge state recoil-ions appears to be feasible.