Resistive instabilities in tokamaks

Technical Report · Tue Oct 01 00:00:00 EDT 1985

DOI:https://doi.org/10.2172/5086595· OSTI ID:5086595

Rutherford, P H

Low-m tearing modes constitute the dominant instability problem in present-day tokamaks. In this lecture, the stability criteria for representative current profiles with q(0)-values slightly less than unit are reviewed; ''sawtooth'' reconnection to q(0)-values just at, or slightly exceeding, unity is generally destabilizing to the m = 2, n = 1 and m = 3, n = 2 modes, and severely limits the range of stable profile shapes. Feedback stabilization of m greater than or equal to 2 modes by rf heating or current drive, applied locally at the magnetic islands, appears feasible; feedback by island current drive is much more efficient, in terms of the radio-frequency power required, then feedback by island heating. Feedback stabilization of the m = 1 mode - although yielding particularly beneficial effects for resistive-tearing and high-beta stability by allowing q(0)-values substantially below unity - is more problematical, unless the m = 1 ideal-MHD mode can be made positively stable by strong triangular shaping of the central flux surfaces. Feedback techniques require a detectable, rotating MHD-like signal; the slowing of mode rotation - or the excitation of non-rotating modes - by an imperfectly conducting wall is also discussed.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 5086595
• Report Number(s): PPPL-2277; ON: DE86002538
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TOKAMAK DEVICES
PLASMA MACROINSTABILITIES
TEARING INSTABILITY
FEEDBACK
MAGNETIC ISLANDS
STABILIZATION
CLOSED PLASMA DEVICES
INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
PLASMA INSTABILITY
THERMONUCLEAR DEVICES
700107* - Fusion Energy- Plasma Research- Instabilities