• F. Herfurth, W.A. Barth, G. Clemente, L.A. Dahl, P. Gerhard, M. Kaiser, H.J. Kluge, N. Kotovski, C. Kozhuharov, M.T. Maier, W. Quint, A. Sokolov, T. Stöhlker, H. Vormann, G. Vorobjev
  GSI, Darmstadt
• O.K. Kester
  NSCL, East Lansing, Michigan
• J. Pfister, U. Ratzinger, A.C. Sauer, A. Schempp
  IAP, Frankfurt am Main

Heavy, highly-charged ions (HCI) with only one or few electrons are interesting systems for precision experiments as for instance tests of the theory of quantum electrodynamics (QED). To achieve high precision, kinetic energy and spatial position of the ions have to be well controlled. This is in contradiction to the production process that employs stripping of electrons at high energies by sending relativistic highly-charged ions with still many electrons through matter. In order to match the production at 400 MeV/u with the requirements of the experiments - stored and cooled HCI at low energy - the linear decelerator facility HITRAP has been built at the experimental storage ring (ESR) at GSI in Darmstadt. The ions are first decelerated in the ESR from 400 to 4 MeV/u, cooled and extracted. The ion beam phase spaces are then matched to an IH-structure, decelerated from 4 to 0.5 MeV/u before a 4-rod RFQ reduces the energy to 6 keV/u. Finally, the HCI are cooled in a Penning trap to 4 K. Extensive ion optical calculations were performed and in recent tests up to one million highly-charged ions have been decelerated from 400 MeV/u to 0.5 MeV/u.

• W.A. Barth, G. Clemente, L.A. Dahl, P. Gerhard, L. Groening, M. Kaiser, B. Lommel, M.T. Maier, S. Mickat, W. Vinzenz, H. Vormann
  GSI, Darmstadt

A low current high duty factor U¹⁰⁺-beam from the Penning Ion Source as well as a high current low duty factor U⁴⁺-beam from a MeVVa source were used for machine investigations in the GSI-UNILAC and synchrotron (SIS18). Carbon stripper foils (20, 40 and 50 ug/cm²) were mounted in the gas stripper section at 1.4 MeV/u to provide for highly charged uranium ions (40+) to be delivered to the SIS18 for life time beam measurements. High current tests were performed to check the durability of the carbon foils. No measurable variation of the stripped low and high current beam in the poststripper DTL could be detected during the life time of the foils. An U⁴⁰⁺-beam current of up to 1.0·10⁺¹¹ particles per 100mues could be reached in the transfer line to the SIS18. This paper will report on the investigations of stripper foils with different thickness. Additionally long time observation of all relevant beam parameters (transverse emittance, energy spread and energy loss, bunch shape, beam transmission up to the SIS-injection) are presented.

• L. Groening, W.A. Barth, W.B. Bayer, G. Clemente, L.A. Dahl, P. Forck, P. Gerhard, I. Hofmann, M. Kaiser, M.T. Maier, S. Mickat, T. Milosic, H. Vormann, S.G. Yaramyshev
  GSI, Darmstadt
• D. Jeon
  ORNL, Oak Ridge, Tennessee
• D. Uriot
  CEA, Gif-sur-Yvette

Recent experiments at the Universal Linear Accelerator (UNILAC) at GSI provided evidence for space charge driven resonances along a periodic DTL. A transverse fourth order resonance has been detected by recording the four fold symmetry in phase space. As predicted in [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009)], the resonance dominates over the envelope instability. Additionally, evidence for resonant emittance transfer from the longitudinal to the transverse plane has been found for settings providing equal depressed tunes of the involved planes.

Slides