Laser cooling of relativistic C ions at the ESR

Recent experiments [1,2] at the Experimental Storage Ring (ESR) at GSI have shown that relativistic Li-like carbon (C) ion beams can be laser-cooled to an unprecedented momentum spread of p/p 10. Here, a single-frequency laser was tuned to the Doppler-shifted 1s2s 1s2p (P1/2 and P3/2) transitions. These results encourage the application of laser cooling to beams of other Liand Na-like ions at even higher energies, as will e.g. be available at FAIR [3]. However, before that, two important techniques still need to be demonstrated: 1) Efficient laser cooling of ion beams with a large initial momentum spread. Additional pre-electron cooling, as was required in the past, should be omitted. In addition, a continuous scan of the bunching frequency was applied to bring the laser frequency in overlap with ions of different velocities inside the bunch. 2) All-optical measurements of the relevant beam parameters. The ultra-low momentum spread of a lasercooled ion beam lies below the sensitivity of the Schottky pick-up system and possible ordering effects in the regime of strong coupling between the ions cannot be resolved. The aim of the upcoming beamtime is to prove the successful technical realization of these techniques at the ESR. In the setup (see Fig. 1) we will apply a new data acquisition and control system, new laser systems, add detectors for fluorescence measurements, and make full use of all new and existing diagnostic tools at the ESR [4].