Velocity Distributions and Density Profiles of Buffer-Gas Gooled One Component Plasma in Toroidal RF lon Trap

Velocity and spatial distributions of calcium (Ca*) ions confined in a toroidal RF trap have been measured by using laser-induced fluorescence method. Cat ion temperature in the toroidal direction decreases from over 2000 K to about 500 K by collisions with He atoms when He pressure is increased from 5 x 10-7 Torr to 5 x 10-5 Torr. The ion density, estimated from the fluorescence intensity of the trapped ions, is roughly estimated as 105 cm-3. The Coulomb coupling parameter f, defined by the ratio of Coulomb energy to kinetic energy of ions, is about 10-4. Ca* ion temperature in poroidal cross-section is estimated from the measured density profile. The velocity distributions and density profiles of the cooled ions are not deviated from those obtained from Boltzmann statistics.