Generation of localized noninductive current by electron cyclotron waves on the DIII-D tokamak

Localized currents due to electron cyclotron current drive have been measur ed for the first time in experiments on the DIII-D tokamak. The location of driven current in the plasma has been varied from near the center of the t okamak out to half of the minor radius. The measured current drive efficien cy agrees with quasilinear Fokker-Planck calculations near the center and e xceeds the predicted value with increasing minor radius. Reduction of the t rapped electron fraction due to finite collisionality is a leading candidat e to explain the discrepancy.