Multiple ionisation of rare gases by high-energy uranium ions

Abstract

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 (Ep) range from 1.4 to 420 MeV u-1. For low recoil-ion charge states sigma (q) decreases over the whole Ep range somewhat more slowly than 1/Ep, 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 Ep dependence of sigma (q) towards high Ep, 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.