Dynamics of fast electrons driven by the lower hybrid wave in giant sawtoothing plasmas

By hard x-ray tomography of the nonthermal bremsstrahlung emission, a detai led investigation of the dynamics of the fast electrons driven by the lower hybrid wave in the presence of giant sawteeth is carried out. While sawtoo th activity is clearly observed on the bulk contribution, no modulation is detected on radiations emitted by the suprathermal population. This origina l effect is interpreted as the consequence of a poor penetration of the wav e in the core of the plasma due to reduced accessibility conditions. Implic ations for current drive in sawtoothing plasmas are discussed.