Mode conversion of fast Alfv{acute e}n waves at the ion{endash}ion hybrid resonance
- Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
- Centre Canadien de Fusion Magnetique, Varennes, Quebec (Canada)
Substantial radio-frequency power in the ion-cyclotron range of frequencies can be effectively coupled to a tokamak plasma from poloidal current strap antennas at the plasma edge. If there exists an ion{endash}ion hybrid resonance inside the plasma, then some of the power from the antenna, delivered into the plasma by fast Alfv{acute e}n waves, can be mode converted to ion-Bernstein waves. In tokamak confinement fields the mode-converted ion-Bernstein waves can damp effectively and locally on electrons [A. K. Ram and A. Bers, Phys. Fluids B {bold 3}, 1059 (1991)]. The usual mode-conversion analysis that studies the propagation of fast Alfv{acute e}n waves in the immediate vicinity of the ion{endash}ion hybrid resonance is extended to include the propagation and reflection of the fast Alfv{acute e}n waves on the high magnetic-field side of the ion{endash}ion hybrid resonance. It is shown that there exist plasma conditions for which the entire fast Alfv{acute e}n wave power incident on the ion{endash}ion hybrid resonance can be converted to ion-Bernstein waves. In this extended analysis of the mode conversion process, the fast Alfv{acute e}n waves can be envisioned as being coupled to an internal plasma resonator. This resonator extends from the low magnetic-field cutoff near the ion{endash}ion hybrid resonance to the high magnetic-field cutoff. The condition for 100{percent} mode conversion corresponds to a critical coupling of the fast Alfv{acute e}n waves to this internal resonator. As an example, the appropriate plasma conditions for 100{percent} mode conversion are determined for the Tokamak Fusion Test Reactor (TFTR) [R. Majeski {ital et} {ital al}., {ital Proceedings} {ital of} {ital the} 11{ital th} {ital Topical} {ital Conference} {ital on} {ital RF} {ital Power} {ital in} {ital Plasmas}, Palm Springs (American Institute of Physics, New York, 1995), Vol. 355, p. 63] experimental parameters. {copyright} {ital 1996 American Institute of Physics.}
- OSTI ID:
- 280177
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 3; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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