High Harmonic ECH Experiment for Extension of Heating Parameter Regime in LHD
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High harmonic electron cyclotron resonance heating (ECH) can extend the plasma heating region to higher density and higher <i>β</i> compared to the normal heating scenario. In this study, the heating characteristics of the second-harmonic ordinary (O2) and third-harmonic extraordinary (X3) modes and the possible extension of heating regime are experimentally confirmed. At the same time, a comparative study using ray-tracing calculation was performed in the realistic three-dimensional configuration of the Large Helical Device. The O2 mode heating showed a 40% absorption rate even above the X2 mode cut-off density. The X3 mode heating using powerful 77 GHz gyrotrons demonstrated an increase of about 40% in the central electron temperature in the plasmas at <i>β</i>-value of about 1%. These results were quantitatively explained to some extent by ray-tracing calculations.
- Plasma and Fusion Research
Plasma and Fusion Research 8(0), 2402073-2402073, 2013
The Japan Society of Plasma Science and Nuclear Fusion Research