O-X-B Heating of Overdense Plasmas by 54.5 GHz Electron Cyclotron Waves in CHS
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An evident increase in the plasma stored energy by applying 54.5 GHz electron cyclotron (EC) waves has been observed in plasmas sustained by neutral beam injection (NBI) with line-averaged electron density of above 3.8 × 10<sup>19</sup> m<sup>-3</sup>, that is, the cut-off density of the 54.5 GHz waves, in the Compact Helical System (CHS). The heating effect can be seen even for high-density over 8 × 10<sup>19</sup> m<sup>-3</sup>: more than twice the cut-off density. The 54.5 GHz EC-wave beam is obliquely injected to high-density plasmas. The scanning of the EC-wave beam direction gives the evident increase in the stored energy at the beam direction where the leakage EC-wave power from the CHS vacuum vessel becomes almost the minimum. The most possible cause for this heating mechanism is an electron Bernstein wave heating via an Ordinary - eXtraordinary - Bernstein (O-X-B) mode conversion process.
- Plasma and Fusion Research
Plasma and Fusion Research (1), 029-029, 2006
The Japan Society of Plasma Science and Nuclear Fusion Research