Investigation of global Alfvén instabilities in the Tokamak Fusion Test Reactor
- 1 July 1992
- journal article
- research article
- Published by AIP Publishing in Physics of Fluids B: Plasma Physics
- Vol. 4 (7), 2122-2126
- https://doi.org/10.1063/1.860462
Abstract
Toroidal Alfvén eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into plasmas at low magnetic field in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 51]. The injection velocities were comparable to the Alfvén speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtoothlike behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization were investigated at various plasma currents and magnetic fields. The results indicate that the instability can effectively clamp the number of energetic ions in the plasmas. The observed instability threshold is discussed in light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high‐frequency oscillations do not have a direct effect on the plasma neutron source strength.Keywords
This publication has 18 references indexed in Scilit:
- Resonant damping of toroidicity-induced shear-Alfvén eigenmodes in tokamaksPhysical Review Letters, 1992
- Continuum damping of high-mode-number toroidal Alfvén wavesPhysical Review Letters, 1992
- On the collisional damping of TAE-modes on trapped electrons in tokamaksPhysica Scripta, 1992
- Excitation of toroidal Alfvén eigenmodes in TFTRPhysical Review Letters, 1991
- Plasma fluctuation measurements in tokamaks using beam-plasma interactionsReview of Scientific Instruments, 1990
- Low-n shear Alfvén spectra in axisymmetric toroidal plasmasPhysics of Fluids, 1986
- High-n ideal and resistive shear Alfvén waves in tokamaksAnnals of Physics, 1985
- Stabilization of the Alfvén wave instability in a two-component tokamakNuclear Fusion, 1977
- Excitation of Alfvén Waves by High-Energy Ions in a TokamakPhysical Review Letters, 1975
- Stability regions of dissipative trapped-ion instabilityNuclear Fusion, 1972