Transverse Laser Cooling of a Radio-frequency Bunched Ion Beam in the Storage Ring Tsr

We report on the observation of the indirect transverse laser cooling eeect in a radio-frequency bunched beam of 7.3 MeV 9 Be + ions, stored in the Heidelberg Test Storage Ring and subject to direct longitudinal laser cooling. This bunched scheme ooers particular advantages for producing ultracold beams with unprecedented phase-space densities. The development of beam cooling techniques has ever had a great impact on experiments with stored charged particle beams 1]. Laser cooling experiments with ion beams have demonstrated their capabilities to produce exceptionally high phase-space densities 2]. In this regime, the innuence of space-charge eeects becomes important and possible ordering eeects may drastically change the beam dynamics 3]. Recent experiments 2] at the Heidelberg Test Storage Ring (TSR) have demonstrated an eecient, indirect transverse cooling eeect during the longitudinal laser cooling of a coasting beam. In a suuciently dense ion beam, intrabeam Coulomb-scattering leads to a relaxation process between all degrees of freedom and facilitates the dissipation of thermal energy from the transverse motion via a longitudinal cooling mechanism. Evidence was found that rare close