Schemes for ICRF Heating of High-Density Core Plasma in LHD

Ion Cyclotron Range of Frequencies (ICRF) heating is one of the plasma heating methods in the Large Helical Device (LHD). The wave injected from the ICRF antenna can propagate in the plasma even if the plasma density is extremely high. It was shown that the high power absorption occurs in the plasma core with the second harmonic heating in the case of high-density deuterium plasma in LHD by the calculation with a simple model of the ICRF heating. Wave number perpendicular to the static magnetic field increases with the plasma density, and it enhances the finite Larmor radius effect in the second harmonic heating. Enhanced finite Larmor radius effect and a large amount of resonant ions enable the intense power absorption. By increasing the frequency, the third harmonic heating will also be possible. Though the intensity of the power absorption will decrease, more localized heating on the magnetic axis will be realized because the finite Larmor radius effect works better in the third harmonic heating