Limits in laser cooling of fast ions in storage rings

Since the first observation of laser cooling of fast, stored ions,1 quantitative investigations of the cooling process and its limits have been undertaken. To overcome the limited interaction time when cooling ions at velocities of approximately 5% of the velocity of light, the ions are trapped in the Heidelberg test storage ring (TSR). There, they can interact repeatedly with a copropagating laser beam in one of the four straight sections of the TSR.