Quiescent H-Mode Plasmas with Rotation Driven by Static Non-axisymmetric Fields

A quiescent H-mode (QH-mode) edge allows ELM-free operation of a plasma with good confinement and good particle exhaust. Until recently, QH-mode operation required rather strong plasma toroidal rotation in order for the edge velocity shear to exceed a minimum value [1]. However, rapid rotation may not be feasible in a self-heated burning plasma with little or no momentum injection from neutral beams. New DIII-D experiments in ITER-similar plasmas show that the neoclassical torque from static, nonresonant magnetic fields (NRMFs) provides a useful knob to change the edge rotation profile shear. NRMF application resulted in QH-mode operation with less than half the rotation (evaluated on top of the pedestal) of previous QH-mode without the NRMFs. At this low rotation, the NRMF torque may be amplified by entering the theoretically predicted $1/\nu$ collisionality regime.\par \vskip8pt \noindent [1] K.H.\ Burrell, {\em et al.}, Phys.\ Rev.\ Lett.\ {\bf 102}, 155003 (2009).