Profile control and its effects on plasma confinement in Heliotron E

The effects of the plasma profile on the global energy confinement have been studied in Heliotron E with special regard to differences between heating methods (ECH, NBI and NBI + ECH). With high power NBI, peaked Ti and peaked ne profiles (Ti(0)/?Ti ? <~ 2.7, ne(0)/?ne? <~4.5) were simultaneously achieved under low recycling conditions. A peaked ne profile (ne(0)/?ne? >~2.5 ) could lead to the high Ti mode where the ion heat transport in the central region is substantially reduced. By changing the ECH launching condition (on-axis, off-axis and toroidally oblique injection), the peakedness of the Te profile could be controlled in the range 1.3 <~Te(0)/?Te? <~4.5. A peaked Te profile and a flat ne profile (3.5 <~Te(0)/?Te?, ne(0)/?ne? <~1.8) were brought about by the well focused on-axis ECH. The ECH plasma with a peaked Te profile has higher stored energy than that with a moderately peaked Te profile for the same injected ECH power and the same density region. The global energy confinement time normalized by the LHD scaling, tEG/tELHD, showed ne(0)/?ne? dependence for the low Ti mode NBI plasmas. For the high Ti mode, the ne(0)/?ne? dependence of tEG/tELHD was weak. These findings suggest that the LHD scaling should be modified to scale the global energy confinement of the helical plasmas in a wide range of ne(0)/?ne?.