Amorphous Carbon Coatings for Mitigation of Electron Cloud in the CERN SPS

Amorphous carbon thin films have been applied to the liners in the electron cloud monitors and to vacuum chambers of three dipole magnets in the SPS. The electron cloud is completely suppressed for LHC type beams in the liners even after 3 months of air venting and no performance deterioration is observed after more than one year of SPS operation. In stainless steel (StSt) liners upon variation of the magnetic field in the monitors the electron cloud current maintains its intensity down to weak fields of some 40 Gauss. This is in agreement with previous findings and also with dark traces observed on the RF shields made of StSt, which are located between dipoles and quadrupoles. The dynamic pressure rise has been used to monitor the behavior of the dipole magnets. It is about the same for coated and uncoated magnets, apart from a weak improvement in the carbon coated ones under conditions of intense electron cloud