STRONG TOROIDAL ASYMMETRIES IN POWER DEPOSITION ON DIVERTOR AND FIRSTWALL COMPONENTS DURING LHCD ON TDEV AND TORE SUPRA

Strong toroidal asymmetries in power deposition during lower hybrid cu rrent drive experiments have been observed on TdeV and Tore Supra. The se asymmetries are characterized by high heat loads on components magn etically connected to the LHCD antenna. The experimental results indic ate that fast electrons generated by the rf fields in the scrape-off l ayer in front of the antenna are responsible for the localized heat lo ads. The rf power lost in the edge through this channel increases with both the edge density and the rf power level. In TdeV, the fraction o f the injected power lost can exceed 10% at high power and high densit y, while it stays under 2% in Tore Supra. A simple model describing th e trajectories of electrons in front of the antenna suggests that the high N-parallel to components of the near field spectrum are responsib le for the acceleration of the scrape-off layer electrons.