Poloidal edge-plasma rotation driven by angular momentum transfer originating from charge exchange in the scrape-off layer of a tokamak

Abstract

A possible new driving mechanism for poloidal plasma rotation in the scrape-off layer (SOL) of a tokamak is proposed. This driving mechanism results from charge exchange between ‘‘cold’’ hydrogen atoms from the wall and ‘‘hot’’ plasma ions in the SOL, where the consequent loss of microscopic angular momentum is compensated by an increase of the macroscopic rotation of the edge plasma. Balancing the increase by viscous damping, inherent to the toroidal geometry of the tokamak, gives values for the poloidal rotation velocity, which are in good agreement with experimental results.