A study of runaway electron confinement and theory of neoclassical MHD turbulence

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5504116

Kwon, Oh Jin

Due to their high sensitivity to magnetic fluctuations, runaway electrons can be used to probe the structure of electromagnetic turbulence that causes anomalous electron heat transport in the L-mode confinement regime. The results of runaway confinement experiments from ASDEX are analyzed and the radial scale length of the magnetic turbulence is determined to be about 1 mm. Using this value and that of experimentally deduced electron thermal diffusivity, the author determines the radial magnetic fluctuation level at the plasma edge in the L-mode to be about 2 {times} 10{sup {minus}4}. From a comparison of these results with the predictions of various theoretical models, it is concluded that resistive-ballooning modes offer the best possibility for a consistent interpretation of the data. Neoclassical MHD equations, which are valid in the experimentally relevant, low-collisionality regimes, support instabilities which might be responsible for anomalous heat transport and high turbulence level of the tokamak edge. From the nonlinear study of neoclassical pressure-gradient-driven turbulence (NPGDT), the turbulent pressure diffusivity is obtained as an eigenvalue of the renormalized equations. The levels and radial scales of turbulence are also determined, and are shown to exceed mixing length estimates by powers of a nonlinear enhancement factor. The reconsideration of the radial structure of magnetic flutter driven by NPGDT leads to estimates of the electron heat transport and magnetic fluctuation levels which differ substantially from previous calculations.

• Research Organization: Texas Univ., Austin, TX (United States)
• OSTI ID: 5504116
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700330 -- Plasma Kinetics
Transport
& Impurities-- (1992-)
700340* -- Plasma Waves
Oscillations
& Instabilities-- (1992-)
ASDEX TOKAMAK
BALLOONING INSTABILITY
CLOSED PLASMA DEVICES
COMPARATIVE EVALUATIONS
CONFINEMENT
DATA ANALYSIS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY TRANSFER
EVALUATION
FERMIONS
FLUID MECHANICS
HEAT TRANSFER
HYDRODYNAMICS
INSTABILITY
LEPTONS
MAGNETOHYDRODYNAMICS
MECHANICS
NEOCLASSICAL TRANSPORT THEORY
PLASMA CONFINEMENT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PRESSURE GRADIENTS
RUNAWAY ELECTRONS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TRANSPORT THEORY
TURBULENCE