Recent results from laser cooling experiments in ASTRID - real-time imaging of ion beams

We describe the latest results from laser cooling experiments using Mg ions in the ASTRID storage ring. In particular, we focus on the transverse dyna mics of the longitudinally cooled beam. We have developed a direct imaging technique, using the laser fluorescence to determine the horizontal and ver tical distributions in the beam. The beam can now be imaged in real time, u sing an image intensifier and a fast-sampling CCD camera. The sensitivity a nd resolution of this system allow direct observation of beams which are we ll below the longitudinal charge density corresponding to a "string" of par ticles. We have observed space-charge limitations to the transverse beam si zes, as well as intriguing instabilities of very low-current beams. (C) 200 0 Elsevier Science B.V. All rights reserved.