Laser cooling of fast stored ions in barrier buckets

We apply novel bunch forms for efficient laser cooling of fast stored ion beams at the Heidelberg Test Storage Ring. Be-9(+) ions are longitudinally confined in barrier buckets providing free motion of the cooled ions inside the bucket (quasi-coasting beam). The implementation of laser cooling in barrier buckets is described, and longitudinal dynamics of laser cooling is compared to electron cooling. With laser cooling, longitudinal temperatures far below 1 K are reached, corresponding to a momentum spread of Delta p/p < 10(-6). When the thermal energy becomes sufficiently small, significant modifications of the ion distribution due to space-charge effects are observed.