Electron Cooling at GSI and FAIR – Status and Latest Activities

The status, function and operation parameters of the existing and future electron coolers at GSI and FAIR are presented. We report on the progress of the ongoing recommissioning of the former CRYRING storage ring with its electron cooler at GSI. First systematic results on the cooling of a 400 MeV proton beam during the last ESR beamtime are discussed. Motivated by the demands of the experiments on high stability, precise monitoring and even absolute determination of the velocity of the electrons i.e. the velocity of the electron- cooled ion beams, high precision measurements on the electron cooler voltage at the ESR were carried out towards the refurbishment of the main high-voltage supply of the cooler. Similar concepts are underway for the CRYRING cooler high-voltage system.