UCLA

The Electric Tokamak [R. J. Taylor, T. A. Carter, J.-L. Gauvreau et al., Nucl. Fusion 45, 1634 (2005)] operates at high plasma density (one and a half times the Greenwald limit) due to a strong particle pinch. However, particle accumulation causes several problems. The operation of the machine can suffer several violent disruptions which hinder the study of many plasma phenomena. Plasma motion and large density swings are undesirable because they alter continuous processes, leaving only transient regimes to study. Particle source and local temperature control can defeat the fundamental mechanisms of this electric pinch. If edge fueling feedback is not sufficient to induce quiescent behavior, the fast ion loss caused by second harmonic ion-cyclotron radio-frequency injection functions as a particle sink deep within the outer plasma cross-section. By linking these strong effects to the fueling feedback, stable medium density (2x10^18 particles/m3) plasmas can be sustained for several seconds. This new regime yields surprisingly long and calm discharges.