Ion temperature and plasma flows in improved confinement mode in the H-1 heliac

Low and improved confinement modes in the H-1 heliac @M. G. Shats et al., Phys. Rev. Lett. 77, 4190 ~1996!# are studied experimentally in rf-sustained ~,100 kW, 7 MHz! argon discharges at low magnetic fields ~,0.15 T!. Surprisingly high ion temperature, measured using a retarding field energy analyzer, is found which increases across the transition to improved confinement mode from 40 to 80 eV, while the electron density increases by about 50%. Both toroidal and poloidal plasma flow velocities do not change across the transition. The increase in a radial electric field in high mode is balanced on average by a corresponding increase in the ion pressure gradient. © 1997 American Institute of Physics. @S1070-664X~97!01710-2#