Plasma Physics Seminar
Monday, March 26
2535 Engineering Hall
Speaker: Carlos Paz-Soldan, University of Wisconsin - Madison
"Stabilization of the Resistive Wall Mode and Error Field Modification by a Rotating Conducting Wall"
Abstract: The interaction of a rotating conducting wall with a linear plasma column and its resistive wall mode (RWM) instability is detailed. A rotating wall capable of routine operation at speeds of ~ 300 km/h was designed, manufactured, and assembled. The interaction of error fields with the rotating wall are shown to lead to asymmetries in wall rotation. Analytic theory is used to illustrate that the error field at a given wall velocity is complex and can often overcome the natural shielding of the wall. MHD mode-locking is found for the first time in a linear plasma column. A torque balance model which includes the effect of the error field, plasma rotation, and wall rotation is developed and applied to the experiment. Asymmetry in wall rotation is also found in the torque balance, with one wall rotation direction eliminating the mode-locking bifurcations. Using locked and born-locked modes, the stabilizing effect of the rotating wall on the RWM is experimentally demonstrated. The rotating wall is found to decrease the locked mode growth rate and increase the RWM stable operation window to higher plasma current.