Global Alfven Eigenmodes in DIII-D

Conference · Mon Jun 01 04:00:00 EDT 1992

OSTI ID:10162267

Turnbull, A D; Chu, M S; Strait, E J; Lao, L L; Greene, J M; Taylor, T S ^[1]; Heidbrink, W W; Duong, H ^[2]; Chance, M S ^[3]

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1. General Atomics, San Diego, CA (United States)
2. California Univ., Irvine, CA (United States)
3. Princeton Univ., NJ (United States). Plasma Physics Lab.

Global Alfven modes, such as the Toroidicity-Induced Alfven Eigenmode (TAE), pose a serious threat for strongly-heated tokamaks since they can result in saturation of the achievable beam {beta} at moderate levels and they may also cause serious {alpha}-particle losses in future ignited devices. The DIII-D tokamak has a unique capability for study of the resonant excitation of these instabilities by energetic beam ions. TAE modes have now been observed in DIII-D over a wide range of operating conditions, including both circular cross-section and elongated ({kappa} {approximately} 1.8) discharges. Equilibrium reconstructions of several representative discharges, using all available external magnetic and internal profile data, have been done and analyzed in detail. The computed real mode frequencies of the TAE modes are in good agreement with the experimentally observed mode frequencies and differ significantly from the estimated kinetic ballooning mode frequencies. The TAE calculations include coupling to the Alfven and acoustic continuum branches of the MHD spectrum and generally indicate that the simplified circular cross-section, large aspect-ratio assumptions made in analytic calculations are poor approximations to the actual TAE mode structures. In particular, the global TAE modes are almost always coupled to one or more continuum branches by toroidicity, poloidal shaping, and finite {beta} effects. Estimates of the various resonant excitation and damping mechanisms, including continuum damping, have been made and the total is found to be in reasonable agreement with the experimental threshold.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-89ER53277; AC02-76CH03073; AC03-89ER51114
• OSTI ID: 10162267
• Report Number(s): GA-A--20935; CONF-920610--10; ON: DE92016250
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700340
ALFVEN WAVES
DOUBLET-3 DEVICE
EIGENVALUES
MHD EQUILIBRIUM
PARTICLE LOSSES
PLASMA INSTABILITY
PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES