Internal kink instability during off-axis electron cyclotron current drive in the DIII-D tokamak
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.
Wong
KL
Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
Chu
MS
Luce
TC
Petty
CC
Politzer
PA
Prater
R
Chen
L
Harvey
RW
Austin
ME
Johnson
LC
La Haye RJ
Snider
RT