Present Performance of Electron Cooling at Cosy-Jülich

At COSY, electron cooling is used after stripping injection of H- or D- ions in order to prepare phase-space-dense ion beams before acceleration to a requested energy. The electron-cooled beam has been successfully applied for specific external experiments. The achievable beam intensity is limited by instabilities during the cooling process. Besides initial losses after injection, as long as the beam has still large emittances, the self-excitation of coherent betatron oscillations is the dominating beam loss mechanism. Perspectives for possible improvements are briefly addressed.