The ion-ion hybrid Alfvén resonator in a fusion environment

Journal Article · Sun Jun 15 04:00:00 EDT 2014 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4882662· OSTI ID:22304129

Farmer, W. A. ^[1]; Morales, G. J. ^[1]

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1. Physics and Astronomy Department, University of California, Los Angeles, Los Angeles, California 90095 (United States)

An investigation is made of a shear Alfvén wave resonator for burning plasma conditions expected in the ITER device. For small perpendicular scale-lengths the shear mode, which propagates predominantly along the magnetic field direction, experiences a parallel reflection where the wave frequency matches the local ion-ion hybrid frequency. In a tokamak device operating with a deuterium–tritium fuel, this effect can form a natural resonator because of the variation in local field strength along a field line. The relevant kinetic dispersion relation is examined to determine the relative importance of Landau and cyclotron damping over the possible resonator parameter space. A WKB model based on the kinetic dispersion relation is used to determine the eigenfrequencies and the quality factors of modes trapped in the resonator. The lowest frequency found has a value slightly larger than the ion-ion hybrid frequency at the outboard side of a given flux surface. The possibility that the resonator modes can be driven unstable by energetic alpha particles is considered. It is found that within a bandwidth of roughly 600 kHz above the ion-ion hybrid frequency on the outboard side of the flux surface, the shear modes can experience significant spatial amplification. An assessment is made of the form of an approximate global eigenmode that possesses the features of a resonator. It is identified that magnetic field shear combined with large ion temperature can cause coupling to an ion-Bernstein wave, which can limit the instability.

• OSTI ID: 22304129
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 21; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALPHA PARTICLES
BERNSTEIN MODE
DISPERSION RELATIONS
IONS
ITER TOKAMAK
KHZ RANGE 100-1000
MAGNETIC FIELDS
MAGNETIC SURFACES
PLASMA WAVES
QUALITY FACTOR