title: Rotation reversal bifurcation and energy confinement saturation in tokamak Ohmic L-mode plasmas.
abstract: Direction reversals of intrinsic toroidal rotation have been observed in diverted Alcator C-Mod Ohmic L-mode plasmas following electron density ramps. For low density discharges, the core rotation is directed cocurrent, and reverses to countercurrent following an increase in the density above a certain threshold. Such reversals occur together with a decrease in density fluctuations with 2 cm(-1)≤k(θ)≤11 cm(-1) and frequencies above 70 kHz. There is a strong correlation between the reversal density and the density at which the Ohmic L-mode energy confinement changes from the linear to the saturated regime.
authors.affiliation: Plasma Science & Fusion Center (PSFC), Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Rice
authors.forename: I
authors.initials: I
authors.lastname: Cziegler
authors.forename: P H
authors.initials: PH
authors.lastname: Diamond
authors.forename: B P
authors.initials: BP
authors.lastname: Duval
authors.forename: Y A
authors.initials: YA
authors.lastname: Podpaly
authors.forename: M L
authors.initials: ML
authors.lastname: Reinke
authors.forename: P C
authors.initials: PC
authors.lastname: Ennever
authors.forename: M J
authors.initials: MJ
authors.lastname: Greenwald
authors.forename: J W
authors.initials: JW
authors.lastname: Hughes
authors.forename: Y
authors.initials: Y
authors.lastname: Ma
authors.forename: E S
authors.initials: ES
authors.lastname: Marmar
authors.forename: M
authors.initials: M
authors.lastname: Porkolab
authors.forename: N
authors.initials: N
authors.lastname: Tsujii
authors.forename: S M
authors.initials: SM
authors.lastname: Wolfe