Latest results of experimental approach to ultra-cold beam at S-LSR

Noda, Akira*; Nakao, Masao*; Soda, Hikaru*; Tongu, Hiromu*; Okamoto, Hiromi*; Osaki, Kazuya*; Yuri, Yosuke; Jimbo, Koichi*; Grieser, M.*; He, Z.*

We have tried to approach to the lowest attainable beam temperature with laser cooling of a 40-keV Mg ion beam at a cooler storage ring S-LSR, which has a superperiodicity of six and is designed to be tough against resonant perturbation to the circulating beam. The capability of active indirect transverse laser cooling has been experimentally demonstrated with the use of the theoretically-proposed synchro-betatron resonance coupling scheme. For the reduction of beam heating due to intrabeam scattering, an additional scheme has been established to control the intensity of the circulating beam down to ions by scraping the outskirt of the beam with the use of a horizontally-moving scraper, which could cool the horizontal and vertical beam temperature down to K and K, respectively, at an operation tune without horizontal-vertical (H-V) coupling. In the present paper, we would like to also present our recent results with H-V coupling in addition to longitudinal-horizontal coupling toward further reduction of the transverse beam temperature.