Perpendicular ion acceleration during ICRF, LHRF and ECH experiments in toroidal plasmas in the UCLA CCT device

Measurements of the fast neutral flux in the CCT (Continuous Current Tokamak) device in ICRF-, LHRF-, and ECH-produced plasmas show a common feature: fast ion tails (Ei/Ti∼100) with large ratios of perpendicular-to-parallel energy (Eperpendicular/Eparallel∼ 100). Perpendicular fast ion production is particularly strong during fast wave RF operation, regardless of driver frequency, but enhanced ion generation has been observed at ω=nΩi, up to n=7. Superthermal ion tails (Ei/Ti∼20) are also present in high-harmonic ICRF-heated tokamak discharges, but the ion distribution function relaxes towards isotropy in pitch angle due to improved ion confinement. In all of the above plasma, the perpedicularity of the fast ion distribution increases with energy