Influence of the Doppler Effect on Electron Cyclotron Heating Power Absorption in the Large Helical Device

In magnetically confined fusion plasmas, electron cyclotron heating (ECH) is a crucial auxiliary heating method that uses high-power microwaves for plasma initiation, electron heating, and current drive. The electron cyclotron resonance condition includes the Doppler effect, which consequently influences ECH power absorption in plasmas. In order to experimentally investigate the Doppler effect on power absorption in high-temperature plasmas, we conducted experiments to scan the injection direction of ECH relative to the magnetic field in the Large Helical Device (LHD). By varying the injection direction of the ECH, we observed changes in the power absorption profile. We will present the detailed experimental results regarding the Doppler effect on ECH.