Profile control and its effects on plasma confinement in Heliotron E

The effects of the plasma profile on the global energy confinement have bee n studied in Heliotron E with special regard to differences between heating methods (ECH, NBI and NBI + ECH). With high power NBI, peaked T-i and peak ed n(e) profiles (T-i(0)/[T-i] less than or similar to 2.7, n(e)(0)/[n(e)] less than or similar to 4.5) were simultaneously achieved under low recycli ng conditions. A peaked n(e) profile (n(e)(0)/[n(e)] greater than or simila r to 2.5) could lead to the high T-i mode where the ion heat transport in t he central region is substantially reduced. By changing the ECH launching c ondition (on-axis, off-axis and toroidally oblique injection), the peakedne ss of the T-e profile could be controlled in the range 1.3 less than or sim ilar to T-e(0)/[T-e] less than or similar to 4.5. A peaked T-e profile and a flat n(e) profile (3.5 less than or similar to T-e(0)/[T-e], n(e)(0)/[n(e )] less than or similar to 1.8) were brought about by the well focused on-a xis ECH. The ECH plasma with a peaked T-e profile has higher stored energy than that with a moderately peaked T-e profile for the same injected ECH po wer and the same density region. The global energy confinement time normali zed by the LHD scaling, tau(E)(G)/tau(E)(LHD), showed n(e)(0)/[n(e)] depend ence for the low T-i mode NBI plasmas. For the high T-i mode, the n(e)(0)/[ n(e)] dependence of tau(E)(G)/tau(E)(LHD) was weak. These findings suggest that the LHD scaling should be modified to scale the global energy confinem ent of the helical plasmas in a wide range of n(e)(0)/[n(e)].