Strong toroidal asymmetries in power deposition on divertor and first wall components during LHCD on TdeV and Tore Supra

Strong toroidal asymmetries in power deposition during lower hybrid current drive experiments have been observed on TdeV and Tore Supra. These asymmetries are characterized by high heat loads on components magnetically connected to the LHCD antenna. The experimental results indicate that fast electrons generated by the rf fields in the scrape-off layer in front of the antenna are responsible for the localized heat loads. The rf power lost in the edge though this channel increases with both the edge density and the rf power level. In TdeV, the fraction of the injected power lost can exceed 10% at high power and high density, while it stays under 2% in Tore Supra. A simple model describing the trajectories of electrons in front of the antenna suggests that the high N| components of the near field spectrum are responsible for the acceleration of the scrape-off layer electrons.