Observation of finite-. beta. MHD phenomena in tokamaks

Technical Report · Sat Sep 01 00:00:00 EDT 1984

DOI:https://doi.org/10.2172/6618576· OSTI ID:6618576

McGuire, K M

Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q/sub 0/ and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 6618576
• Report Number(s): PPPL-2134; ON: DE84017072
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
PLASMA MACROINSTABILITIES
BETA RATIO
TOKAMAK TYPE REACTORS
COUPLING
ENERGY SPECTRA
HIGH-BETA PLASMA
MAGNETOHYDRODYNAMICS
OPTIMIZATION
PLASMA CONFINEMENT
PLASMA WAVES
CONFINEMENT
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MECHANICS
PLASMA
PLASMA INSTABILITY
SPECTRA
THERMONUCLEAR REACTORS
700107* - Fusion Energy- Plasma Research- Instabilities