Comparative Experiments on Lower Hybrid Wave Heating of Ions in High-Density Hydrogen and Deuterium Plasmas at the FT-2 Tokamak

Abstract

In the framework of the isotope effect studies at the FT-2 tokamak, the efficiencies were compared of the lower hybrid wave heating of the ion components of the hydrogen and deuterium plasmas with high densities (close to the Greenwald limit, 〈ne〉 ≤ 1020 m–3). It was experimentally ascertained that, in accordance with the theoretical concepts, the efficient axial heating of the deuterium plasma ions occurs, as opposed to the peripheral heating of the hydrogen plasma ions. Such an isotope effect occurs due to the different localization of the plasma-RF wave interaction regions. The distinctive feature of these experiments is the fact that, in deuterium plasma, during the preliminary ohmic heating, the dependence of the energy lifetime on density τЕ(n) is linear (LOC dependence), and, with increasing density, the transition to the improved ohmic confinement mode occurs. In hydrogen plasma, on the contrary, the transition to the saturation mode is observed. In this study, the considerable decrease in τЕ was revealed, observed during the additional lower hybrid wave heating in both hydrogen and deuterium plasmas.