Dispersive 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 transfer heat from the horizontal into the longitudinal degree of freedom, thereby increasing the horizontal cooling rate on the expense of the longitudinal rate. The cooling scheme requires a horizontal gradient of the longitudinal cooling force which can be achieved by displacing the electron beam relative to the ion beam, and a finite dispersion in the ion–electron interaction region. Operating the heavy ion test storage ring TSR at a moderate dispersion of DS=1.81 m, we investigated the dispersive electron cooling process and found good agreement with the expectations from fundamental considerations.