Mechanism for rapid sawtooth crashes in tokamaks
The sawtooth oscillations in the soft x-ray signals observed in tokamaks are associated with periodic changes in the central electron temperature, T/sub e/. Typically, a slow phase during which the central temperature slowly rises is followed by a fast drop in T/sub e/, associated with flattening of the central temperature. The time scale of the slow phase is determined by various transport processes such as ohmic heating. The resistive internal kink mode was invoked by Kadomtsev to explain the crash phase of the oscillations. Fast crash times observed in the large tokamaks are studied here, especially the fast crashes observed in JET. These sawtooth oscillations are characterized by the absence of any discrenible precursor oscillations, and a rapid collapse of the central temperature in about 100 microseconds. During the crash phase, the hot core region rapidly moves outward and is replaced by colder plasma. Then, this highly asymmetric state relaxes (in approx.100..mu..sec) to a poloidally symmetric state in which a ring of hot plasma surrounds the colder core plasma, producing a hollow pressure profile.
- Research Organization:
- Texas Univ., Austin (USA). Inst. for Fusion Studies
- DOE Contract Number:
- FG05-80ET53088
- OSTI ID:
- 5258608
- Report Number(s):
- DOE/ET/53088-250; IFSR-250; ON: DE86016136
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
700107* -- Fusion Energy-- Plasma Research-- Instabilities
CLOSED PLASMA DEVICES
ELECTRON TEMPERATURE
INSTABILITY
JET TOKAMAK
MATHEMATICAL MODELS
PLASMA INSTABILITY
SPECTRA
THERMONUCLEAR DEVICES
THERMONUCLEAR REACTORS
TOKAMAK DEVICES
TOKAMAK TYPE REACTORS
X-RAY SPECTRA