Realization of the phase transition of a charged particle beams

点击翻译按钮获取中文摘要

The purpose of this study is to demonstrate the realizability of the phase transition of a charged-particle beam circulating in a storage ring. The molecular dynamics (MD) simulation technique was employed to investigate the possibility of beam crystallization. To experimentally explore the collective motion of a high-quality beam, we developed a table-top system 'S-POD (Simulator for Particle Orbit Dynamics)" that consists mainly of a linear Paul trap, a laser cooler high precision ion detectors, a vacuum system, and various power supplies. S-POD enables one to make a systematic study of collective phenomena in space-charge-dominated beams. Experiments of beam cooling were also carried out at the ion storage ring "S-LSR" of Kyoto University The main results obtained during the term of this project are summarized as follows:1. Extensive MD simulations were performed, which demonstrate that multi-dimensional Coulomb crystals can be stabilized in a dispersion-free storage ring without the use of tapered dissipative force2. A Wien filter can naturally extend a longitudinal beam cooling force to the transverse degrees of freedom and, thus, makes it possible to establish a coasting crystalline state when EP beam line density is sufficiently low.3. Results of S-POD experiments indicate that the stability of a high-quality beam in a storage ring may be affected not only by coherent resonance but also by incoherent resonance.4 A laser cooling system and a laser-induced fluorescence diagnostic were designed and constructed for S-POD. Ca" ions were successfully Doppler cooled and formed one-dimensional Coulomb crystals.5. The longitudinal motion of a coasting ^<24>Mg^+beam was laser-cooled in S-LSR (although an ultracold state was not reached due to the lack of transverse dissipation). The one-dimensional ordering of a 7MeV proton beam was observed with an electron cooler switched on.