Instability phenomena of electron-cooled ion beams at COSY

At the cooler synchrotron 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. In addition, stacking of an electron cooled beam at injection could significantly increase the stored beam intensity. Transverse coherent instabilities due to beam-wall interaction occurring at higher intensities could be cured through chromaticity correction either by introducing more Landau damping or by applying an active transverse feedback system. This led to an increase in intensity and stability of a cooled beam. (C) 2004 Elsevier B.V. All rights reserved.