Electron cooling experiments at the heavy ion storage ring TSR

At low relative velocities the transverse cooling rates of fast stored ions by cold electrons are usually smaller than the longitudinal ones. By dispersive electron cooling, however, it is possible to increase the horizontal cooling rate on the expense of the longitudinal rate. The cooling scheme requires a horizontal gradient of the longitudinal cooling force, which was achieved by displacing the electron beam relative to the ion beam, and a finite dispersion in the ion–electron interaction region. Moreover, electron cooling of very hot ion beams is usually rather slow. Two different methods were investigated to study the longitudinal cooling times. The first method uses an induction accelerator to push the ions into the effective velocity range of the longitudinal electron cooling force. In the second method the mean electron velocity is swept over the velocity distribution of the ion beam in order to decrease the collection time.