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- M. H. Bussmann, D. Habs
LMU, München
- K. Beckert, P. Beller, B. Franzke, C. Kozhuharov, T. Kuehl, W. Noertershaeuser, F. Nolden, M. Steck
GSI, Darmstadt
- Ch. Geppert, S. Karpuk
Johannes Gutenberg University Mainz, Mainz
- C. Novotny
Johannes Gutenberg University Mainz, Institut für Physik, Mainz
- S. Reinhardt
MPI-K, Heidelberg
- G. Saathoff
MPQ, Garching, Munich
- U. Schramm
FZD, Dresden
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We report on the first laser cooling of a bunched beam of C3+ ions at the ESR (GSI) at a beam energy of E = 1.47 GeV. Combining laser cooling of the 2S1/2-2P3/2 transition with moderate bunching of the beam lead to a reduction of the longitudinal momentum spread by one order of magnitude if compared to pure electron cooling. If additional electron cooling was applied, thus increasing the coupling between the longitudinal and transverse degree of freedom, three-dimensional cold beams with a plasma parameter of unity could be attained. In a second measurement campaign, a combination of a sweeping-frequency and a fixed-frequency laser beam was succesfully implemented to increase the momentum acceptance of the narrow band laser force. This cooling scheme improved the match of acceptance of the laser force to the momentum spread of the beam and reduced heating due to intra beam scattering. In addition to the interesting beam dynamics observed at low momentum spreads of ∆p / p < 10-6 precision spectroscopy of 2S1/2-2P1/2 and 2S1/2-2P3/2 transition was performed, both absolute and relative, at a precision challenging the best theoretical models available. The laser cooling schemes used at the ESR can be directly extended to the regime of ultra-relativistic ion energies at the new FAIR facility. There, it becomes possible to cool a large number of ion species using a single laser beam source, exploiting the relativistic Doppler shift of the laser frequency. Finally, the fluorescence photons emitted by these ultra-relativistic laser cooled ion beams can be directly used for precision X-ray spectroscopy of the cooling transitions. The resolution of such measurements would essentially be only limited by the resolution of the X-ray spectrometers available.
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