Observation and control of resistive wall modes

Resistive wall modes and nonuniform wall rotation

The resistive wall mode ~RWM! poses a threat to many plasma confinement devices. The continuous rotation of the wall relative to the plasma makes it appear perfectly conducting, because of the skin effect, but this is ineffective if the perturbation locks to the wall. This raises the question of whether a nonuniformly rotating wall is more effective. In this paper we discuss the effect of such ...

Observation of resistive and ferritic wall modes in a line-tied pinch.

The resistive wall mode is experimentally identified and characterized in a line-tied, cylindrical screw pinch when the edge safety factor is less than a critical value. Different wall materials have been used to change the wall time and show that the growth rates for the RWM scale with wall time and safety factor as expected by theory. The addition of a ferritic wall material outside the condu...

Effect of Control Coil Configuration and Feedback Gain on Resistive Wall Modes in HBT-EP*

Critical Toroidal Rotation Profile for Resistive Wall Modes and Control of Magnetic Islands in Tokamaks

Abstract A three-mode model for the resistive wall modes based on the toroidally coupled resistive wall tearing modes is developed. The linear neoclassical tearing mode response is used at the singular surfaces to enhance plasma inertia and reduce the toroidal rotation speed for stability. The dispersion relation is obtained from the determinant of a 6×6 matrix. The toroidal rotation profile fo...

EX/P9-5 Comprehensive Control of Resistive Wall Modes in DIII-D Advanced Tokamak Plasmas

The resistive wall mode (RWM) and neoclassical tearing mode (NTM) have been simultaneously suppressed in the DIII-D for durations over 2 seconds at beta values 20% above the no-wall limit with modest electron cyclotron current drive (ECCD) and low plasma rotation. The critical plasma rotation was significantly lower than reported at the IAEA FEC in 2006. However, even in this stabilized regime,...