Influence of coupling to spectra of weakly damped eigenmodes in the ion cyclotron range of frequencies on parasitic absorption in rectified radio frequency sheaths
- Alfven Laboratory, Royal Institute of Technology, Association VR-Euratom, Stockholm (Sweden)
Coupling to broad spectra of weakly damped magnetosonic eigenmodes in the ion cyclotron range of frequencies is analyzed. Small variations in density or magnetic field can significantly affect the phase of the reflected wave and hence the coupling in large tokamaks. Under such conditions a statistical treatment is appropriate for predictions of coupling properties. Although the average coupling resistance is independent of single pass damping the antenna voltage, the wave field at the walls and the average power absorbed in the plasma are affected. The average losses caused by rectified rf sheath potentials increase with decreasing single pass damping and with decreasing width of the toroidal mode spectrum. The losses are sensitive to the misalignment between the equilibrium magnetic field and the Faraday screens of the antennas. These effects can at least partly explain the reduced heating efficiencies observed in scenarios with weak single pass damping and the differences in performance between different antennas and phasings.
- OSTI ID:
- 20698378
- Journal Information:
- Physics of Plasmas, Vol. 12, Issue 3; Other Information: DOI: 10.1063/1.1851988; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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