Kyoto ICR, Uji, Kyoto
MPI-K, Heidelberg
JINR, Dubna, Moscow Region
NIRS, Chiba-shi
Ion storage and cooler ring, S-LSR, has been designed to enable the investigation of coldest possible ion beams with use of various beam cooling schemes such as an electron beam cooling and the laser cooling. Electron beam cooling of 7 MeV protons and laser cooling of 40 keV Mg ions have been applied up to now. The first laser cooling applied to ~108 Mg ions with the induction accelerator voltage of ~6 mV reduced the momentum spread (1 σ) from 1.7×10-3 to 2.9×10-4, which is considered to be saturated by the momentum transfer from transverse degree of freedom to the longitudinal one due to intra-beam scattering. The laser cooling force has been improved from the above one more than one order of magnitude owing to the precise alignment between the laser and Mg ion beam. Recent measurement with frequency shift of the laser showed the enhancement of the coherent signals in odd harmonics of the revolution frequency picked up with an electrostatic beam monitor and detailed measurements of various harmonics have been performed with changing the resolution bandwidth of the spectrum analyzer, although the origin of such coherency is not yet identified up to now. For the purpose of measurement of lowest possible temperature attainable by the laser cooling, measurement with reducing the ion numbers of Mg is needed, which has been blocked by the difficulty of observing the Schotty signal of such a low intensity beam. So as to cope with this situation, development of observing system of emitted light by the transition from the upper level to the ground state with the use of photomultiplier has been performed, which recently succeeded in detection of clear signals coming from the oriented process. Activities above mentioned will be presented together with the forth coming experimental results on laser cooling.
