Coupling of global toroidal Alfven eigenmodes and reversed shear Alfven eigenmodes in DIII-D
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
- Fusion Research Center, University of Texas, 1 University Station, Austin, Texas 78712-0263 (United States)
- Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)
- University of California, Irvine, California 92697 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- University of Wisconsin, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States)
Reversed shear Alfven eigenmodes (RSAEs) are typically thought of as being localized near the minima in the magnetic safety factor profile, however, their spatial coupling to global toroidal Alfven eigenmodes (TAEs) has been observed in DIII-D discharges. For a decreasing minimum magnetic safety factor, the RSAE frequency chirps up through that of stable and unstable TAEs. Coupling creates a small gap at the frequency degeneracy point forming two distinct global modes. The core-localized RSAE mode structure changes and becomes temporarily global. Similarly, near the mode frequency crossing point, the global TAE extends deeper into the plasma core. The frequency splitting and spatial structure of the two modes throughout the various coupling stages, as measured by an array of internal fluctuation diagnostics, are in close agreement with linear ideal MHD calculations using the NOVA code. The implications of this coupling for eigenmode stability is also investigated and marked changes are noted throughout the coupling process.
- OSTI ID:
- 20975041
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 14; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Alfv?nic Instabilities and Fast Ion Transport in the DIII-D Tokamak
Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges