Lower hybrid current drive efficiency and power deposition profile during MHD activity in tore supra

When the magnetic shear vanishes over a wide spatial region close to the q=2 surface, a strong MHD activity ascribed to a global tearing mode m/n=2/1 is observed, corresponding to a 15% reduction of the current drive efficiency, and a significant flattening of the HXR profile localized in the vicinity of the island. Calculations of the HXR bremsstrahlung and the LH current drive efficiency are reported based on Fokker-Planck calculations to assess the role played by the fastest electrons of the tail, and identify the fraction which is lost by the MHD perturbation.