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RS-APS-Seminar

Donnerstag, 01.03.2018, 14:00 Uhr
Seminarraum HI-Jena, Fröbelstieg 3
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Charge State Distributions for Relativistic Heavy Ion Beams at CERN and FAIR

Felix Kröger
Universität Jena

In this work charge state distributions of heavy ions have been calculated for the production of effective stripper foils for heavy ion acceleration facilities. In this context, the FAIR facility at GSI and the proposed Gamma Factory at CERN are presented, where the use of partially stripped, relativistic ions will be of special interest for upcoming experiments. To determine the charge state distribution as a function of penetration depth, various programmes have been applied depending on the respective energy regime. For stripping scenarios in the lower energy regime, the GLOBAL code was applied, that allows to take into account up to twenty-eight projectile electrons for energies up to 2000 MeV/u. Since the GSI/FAIR facility can accelerate even low-charged uranium ions up to 2700 MeV/u, and the Gamma Factory at CERN considers a stripping scenario at 59000 MeV/u, another programme was needed. This is why for the stripping scenarios in the high energy regime, first the well-known CHARGE code was used. However, even if it can operate in the very high energy regime, it only takes into account bare, hydrogen- and helium-like projectile charge states. To overcome this limitation, the recently developed BREIT code was verified and used for stripping scenarios in the high energy regime. As this code has no built-in treatment of the various charge-changing processes, it needs a multitude of information about the electron capture and loss cross sections as input parameters. Thus, for the calculation of charge state distributions with the BREIT code, cross sections were produced by well tested theories and codes. The BREIT code together with the codes for the cross section production were then applied for two studies: first for an exemplary study for the upcoming GSI/FAIR facility to show the practicability of the BREIT code together with the cross section programmes, and then for a study to find optimal stripper foils for the Gamma Factory study group at the CERN facility, in order to produce efficiently Pb80+ and Pb81+ ions from a Pb54+ beam before entering the LHC. In addition, experimental data of a beam time at ESR at GSI in 2016 was analysed, where a Xe54+ ion beam of several MeV/u was colliding with a hydrogen gas target. The resulting experimental capture cross sections allowed to verify the suitability of the EIKONAL code for the prediction of the NRC cross sections for upcoming experiments at CRYRING@GSI.