Modifications of turbulence and turbulent transport associated with a bias-induced confinement transition in LAPD

摘要: Azimuthal flow is driven in the edge of Large Plasma Device (LAPD) [W. Gekelman, {\itshape et. al}, Rev. Sci. Instr. {\bfseries 62}, 2875 (1991)] through biasing a section vacuum vessel relative to plasma source cathode. As applied bias exceeds threshold, transition radial particle confinement observed, evidenced by dramatic steepening density profile, similar L- H-mode toroidal devices. The threshold behavior and dynamic transport related penetration degree spatial overlap between shear gradient profiles. An investigation changes turbulence turbulent associated with presented. Two-dimensional cross-correlation measurements show that coherence LAPD significantly biasing. azimuthal correlation increases dramatically, while length little altered. Turbulent amplitude reduced at transition, particularly electric field fluctuations, but dominant change observed cross-phase fluctuations. lead suppression then apparent reversal flux as exceeded.