Experimental approach to ultra-cold ion beam at S-LSR

At S-LSR, abrupt reduction of momentum spread of 7 MeV proton beam to ~2 × 10^-6 at proton number of ~2000 has been observed, which indicates phase transition to 1 dimensional ordered state. Attained proton temperatures after transition are 26 μeV and 1 meV for longitudinal and transverse directions, respectively, which compared with the corresponding values of 20 μeV and 34 meV for electron beam, indicates the magnetization of electron. Laser cooling of 24Mg⁺ has also been started and momentum spread of ~10⁸ ions is reduced to 2 × 10^-4, saturated with the momentum transfer from transverse degree of freedom by intra-beam scattering.