Multiple-electron losses in uranium ion beams in heavy ion synchrotrons

摘要

Charge changing processes as the result of collisions with residual gas particles are the main cause of beam loss in high energy medium charge state heavy ion beams. To investigate the magnitude of this effect for heavy ion synchrotrons like the planned SIS100 at GSI, the multiple-electron and the total electron-loss cross sections are calculated for U~(q+) ions, q = 10, 28, 40, 73, colliding with typical gas components H_2, He, C, N_2, O_2, and Ar at ion energies E = 1 MeV/u-10 GeV/u. The total electron-capture cross sections for U~(28+) and U~(73+) ions interacting with these gases are also calculated. Most of these cross sections are new and presented for the first time. Calculated charge-changing cross sections are used to determine the ion-beam lifetimes τ for U~(28+) ions which agree well with the recently measured values at SIS18/GSI in the energy range E = 10-200 MeV/u. Using simulations made by the StrahlSim code with the reference ion U~(28+), it is found that in SIS100 the beam loss caused by single and multiple electron losses has only little impact on the residual gas density due to the high efficiency of the ion catcher system.