Investigation of global Alfven instabilities in TFTR
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- Princeton Univ., NJ (United States). Plasma Physics Lab.
- Wisconsin Univ., Madison, WI (United States)
- Texas Univ., Austin, TX (United States)
- Columbia Univ., New York, NY (United States)
Toroidal Alfven Eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into TFTR plasmas at low magnetic field such that the injection velocities were comparable to the Alfven 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 sawtooth-like 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 was investigated at various plasma current and magnetic field. The results indicate that the instability can effectively clamp the number of energetic ions in the plasma. The observed instability threshold is discussed in the 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 direct effect on the plasma neutron source strength.
- Research Organization:
- Princeton Univ., NJ (United States). Plasma Physics Lab.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 10118084
- Report Number(s):
- PPPL--2816; ON: DE92006649
- Country of Publication:
- United States
- Language:
- English
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