title: Internal kink instability during off-axis electron cyclotron current drive in the DIII-D tokamak
abstract: Experimental evidence is reported of an internal kink instability driven by a new mechanism: barely trapped suprathermal electrons produced by off-axis electron cyclotron heating on the DIII-D tokamak. It occurs in plasmas with an evolving safety factor profile q(r) when q(min) approaches 1. This instability is most active when ECCD is applied on the high field side of the flux surface. It has a bursting behavior with poloidal/toroidal mode number = m/n = 1/1. In positive magnetic shear plasmas, this mode becomes the fishbone instability. This observation can be qualitatively explained by the drift reversal of the barely trapped suprathermal electrons.
authors.affiliation: Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
authors.initials: KL
authors.lastname: Wong
authors.initials: MS
authors.lastname: Chu
authors.initials: TC
authors.lastname: Luce
authors.initials: CC
authors.lastname: Petty
authors.initials: PA
authors.lastname: Politzer
authors.initials: R
authors.lastname: Prater
authors.initials: L
authors.lastname: Chen
authors.initials: RW
authors.lastname: Harvey
authors.initials: ME
authors.lastname: Austin
authors.initials: LC
authors.lastname: Johnson
authors.lastname: La Haye RJ
authors.initials: RT
authors.lastname: Snider