title: Reduced critical rotation for resistive-wall mode stabilization in a near-axisymmetric configuration.
abstract: Recent DIII-D experiments with reduced neutral beam torque and minimum nonaxisymmetric perturbations of the magnetic field show a significant reduction of the toroidal plasma rotation required for the stabilization of the resistive-wall mode (RWM) below the threshold values observed in experiments that apply nonaxisymmetric magnetic fields to slow the plasma rotation. A toroidal rotation frequency of less than 10 krad/s at the q=2 surface (measured with charge exchange recombination spectroscopy using C VI) corresponding to 0.3% of the inverse of the toroidal Alfvén time is sufficient to sustain the plasma pressure above the ideal MHD no-wall stability limit. The low-rotation threshold is found to be consistent with predictions by a kinetic model of RWM damping.
authors.affiliation: Columbia University, New York, New York 10027, USA.
authors.forename: H
authors.initials: H
authors.lastname: Reimerdes
authors.forename: A M
authors.initials: AM
authors.lastname: Garofalo
authors.forename: G L
authors.initials: GL
authors.lastname: Jackson
authors.forename: M
authors.initials: M
authors.lastname: Okabayashi
authors.forename: E J
authors.initials: EJ
authors.lastname: Strait
authors.forename: M S
authors.initials: MS
authors.lastname: Chu
authors.forename: Y
authors.initials: Y
authors.lastname: In
authors.forename: R J
authors.initials: RJ
authors.lastname: La Haye
authors.forename: M J
authors.initials: MJ
authors.lastname: Lanctot
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Liu
authors.forename: G A
authors.initials: GA
authors.lastname: Navratil
authors.forename: W M
authors.initials: WM
authors.lastname: Solomon
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: R J
authors.initials: RJ
authors.lastname: Groebner