• G.X. Xia
  MPI-P, München
• M. Ivanyan
  CANDLE, Yerevan
• K. Manukyan, K.A. Sargsyan
  YSU, Yerevan
• R. Wanzenberg
  DESY, Hamburg

At DESY the PETRA accelerator has been converted into a new 3rd generation high-brilliance synchrotron radiation facility called PETRA III. For the first commissioning in spring 2009 a positron beam is used. In the future it is also foreseen to operate the synchrotron light source with an electron beam. Ion effects pose a potential problem to the electron beam operation of PETRA III. In this paper, a weak-strong simulation code is employed to study the ion effect issues in detail for different operation scenarios.

• R. Wanzenberg
  DESY, Hamburg
• E. Métral
  CERN, Geneva

Wakefields and trapped Higher Order Modes in the CMS experimental chamber at the LHC are investigated using a geometrical model which closely reflects the presently installed vacuum chamber. The basic rf-parameters of the higher order modes (HOMs) including the frequency, loss parameter,and the Q-value are provided. To cover also transient effects the short range wakefields and the total loss parameter has been calculated, too. Most numerical calculations are performed with the computer code MAFIA. The calculations of the Modes is complemented with an analysis of the multi-bunch instabilities due to the longitudinal and dipole modes in the CMS vacuum chamber.