Experimental Observation of rf Driven Plasma Flow in the Phaedrus-T Tokamak

We have observed frequency shifts of the $2/1$ tearing mode in a tokamak that are consistent with injecting momentum with low frequency rf waves. The $2/1$ frequency increased for current drive antenna phasing, decreased for anticurrent drive phasing, and was linear with rf power and driven current. The change in the toroidal velocities derived from the frequency shifts and the calculated rf momentum is consistent. The frequency change also increased with magnetic field, independent of antenna phasing. This is the first demonstration of modifying the $2/1$ frequency through rf momentum input.