Stabilization of the resistive wall mode by differentially rotating walls

The effect of differentially rotating walls on external resistive wall inst abilities is investigated for a general cylindrically symmetric diffuse pin ch configuration. It is found that when the relative wall rotation velocity exceeds a critical value, the resistive wall mode is stabilized. The criti cal rotation frequency is, however, quite large, well above the growth rate with a single wall and probably impractical for a realistic experiment. Th ough the presence of a finite vacuum gap between the walls reduces the crit ical velocity for stabilization, the required flow is still likely to be to o large for practical applications. (C) 2001 American Institute of Physics.