FORMATION AND TERMINATION OF HIGH ION TEMPERATURE MODE IN HELIOTRON TORSATRON PLASMAS/

The physics of the formation and termination of high ion temperature m ode (hgh T-i mode) is studied by controlling density profiles and radi al electric field. High ion temperature mode is observed for neutral b eam heated plasmas in heliatron/torsatron plasmas (Heliotron-E). This high T-i mode plasma is characterized by a peaked ion temperature prof ile and is associated with a peaked electron density profile produced by neutral beam fuelling with low wall recycling. This high T-i mode i s terminated by flattening of the electron density caused either by ga s puffing or by second-harmonic ECH (core density 'pump out').