Hybrid-kinetic simulation of the generation of mass flow due to plasma-wall interaction in reversed-field pinches

Abstract

Flux loop and line density measurements in the reversed-field pinch ZT-40M indicate the existence of poloidally symmetric excitations in the edge that move in the direction anti-parallel to the toroidal current with a velocity of the order of the thermal ion speed. A recently proposed mechanism of momentum transfer between the plasma and the wall explains these observations by showing that plasma flow near the wall can be sustained over magnetohydrodynamic time scales as a result of unidirectional transfer of momentum during a collision with the wall of an ion with finite gyroradius. The present hybrid-kinetic simulations substantiate the proposed mechanism by showing that within a few to ten microseconds flow of the required direction and order of magnitude results from collisions of ions with a momentum-absorbing wall.