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 detailed investigation of the dynamics of the fast electrons driven by the lower hybrid wave in the presence of giant sawteeth is carried out. While sawtooth activity is clearly observed on the bulk contribution, no modulation is detected on radiations emitted by the suprathermal population. This original effect is interpreted as the consequence of a poor penetration of the wave in the core of the plasma due to reduced accessibility conditions. Implications for current drive in sawtoothing plasmas are discussed.