Kinetic Alfven eigenmodes in JET and DIII-D

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:489482

Jaun, A; Hellsten, T ^[1]; Heidbrink, W W; Carolipio, E ^[2]

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1. Alfven Lab., Stockholm (Sweden)
2. Univ. of California, Irvine, CA (United States); and others

Kinetic effects are studied for global Alfven eigenmodes in realistic tokamak equilibria with finite aspect ratio and plasmas, comparing calculations from the full wave code PENN with experimental measurements. The kinetic plasma model is based on a Larmor radius expansion in toroidal geometry and takes into account the gradients in the equilibrium density and temperatures. It allows for a consistent description of the mode conversion to the kinetic Alfven wave (KAW) and the effect of diamagnetic drifts on electromagnetic waves. Comparisons axe first carried out for a JET discharge, showing that multiple peeks measured in the low frequency Alfven spectrum are the signature of kinetic Alfven eigenmodes (KAE) induced through coupling between a global ellipticity Alfven eigenmode (EAE) and the KAW. In general, series of modes appear in the proximity of global fluid modes, some with a regular spacing in frequency and a very weak Landau damping of {vert_bar}{gamma}/{omega}{vert_bar} {approx_equal} 0.0007. A kinetic analysis of a DIII-D discharge shows that TAE mode wavefields reach the plasma core through electromagnetic drift waves which propagate because of finite temperature gradients in the regions of small k{sub {parallel}}. They can lead to particle diffusion and may explain the large losses of beam ions observed during the TAE instabilities. Comparisons of frequency and eigenmode structure axe carried out for resistive and kinetic models, between the theoretical calculations using the PENN code and the experimental measurements from magnetic probes.

• OSTI ID: 489482
• Report Number(s): CONF-960354--
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
EIGENFREQUENCY
KINETIC EQUATIONS
PLASMA INSTABILITY
TOKAMAK DEVICES