Vacuum and Electron Cloud Issues at the Gsi Present and Future Facilities

According to the international accelerator project at GSI, the double synchrotron SIS100/300 and a chain of storage rings will be built (using the present GSI synchrotron SIS18 as injector) in order to achieve high intensity and high energy heavy ion pulses for nuclear or plasma physics studies or anti-proton production. Dynamic vacuum instability and electron cloud are potential intensity limiting factors in the SIS18 and SIS100/300, which need to be investigated. Dynamic vacuum instability induced by ion loss due to charge exchange presently limits the intensity in the SIS18 to a few 10 U, well below the design goal value needed for the future facility. NEG-coating of the vacuum chamber surface and a system of collimators to intercept the beam losses in a controlled way are the measures presently under study to push up the instability threshold. A broad simulation campaign aimed at defining possible electron cloud issues in the SIS18 and in the SIS100/300 shows on the other hand that the thresholds for electron cloud build up in terms of SEY are rather high. Parameters like SEY and dimensions of the beam vacuum chamber for SIS100/300 have been swept over wide ranges of values, and good sets for the safe ring operation are thus identified.