High Core Electron Confinement Regimes in FTU Plasmas with Low-or Reversed-Magnetic Shear and High Power Density Electron-Cyclotron-Resonance Heating

Electron temperatures in excess of 8 keV have been obtained by electron-cyclotron-resonance heating on FTU plasmas at peak densities up to 8×1019 m-3. The magnetic shear in the plasma core is low or negative, and the electron heat diffusivity remains at, or below, the Ohmic level (0.2 m2/s), in spite of the very large heating power density (10-20MW/m3) which produces extremely high temperature gradients (up to 120 keV/m). The ion heat transport remains at the neoclassical level.