Study of the Antenna Loading Resistance of the LHD ICRF Antenna

概要

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Ion cyclotron range of frequencies (ICRF) heating is used to heat plasma in magnetically confined fusion plasma experiments. ICRF heating has been used in the Large Helical Device (LHD) and contributes to high-power steady-state experiments. Antenna loading resistance is important in ICRF heating; a high loading resistance is required for high-power injection. Many elements influence the antenna loading resistance. Here, the dependence of the loading resistance on various parameters is investigated. The loading resistance is very low at lower wave frequencies. High-power injection using such frequencies was difficult in plasma heating experiments in the LHD. The loading resistance increases with the plasma density. The distance between the antenna and the plasma boundary is closely related to the plasma edge density. It is important to keep the antenna away from the plasma and also keep the loading resistance at a certain level in steady-state operation for the various types of plasma. The effect of additional heating and magnetic field strength are also investigated. These results will contribute to the design of new ICRF antennas, the ICRF heating experiment in the LHD, and ICRF heating in future plasma devices.