Weak turbulence theory of collisionless trapped electron driven drift instability in tokamaks

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859854· OSTI ID:5838022

Hahm, T S; Tang, W M ^[1]

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1. Plasma Physics Laboratory, Princeton University, Princeton, NJ (USA)

The toroidal collisionless trapped electron modes are analyzed in the weak turbulence regime treating both ions and trapped electrons nonlinearly in the presence of ion and electron temperature gradients. The spectral intensity of the density fluctuations in the nonlinearly saturated state is analytically obtained from the steady-state solution of the wave-kinetic equation. Distant nonlinear interactions between low-{ital k}{sub {theta}} and high-{ital k}{sub {theta}} modes of similar frequencies via trapped electron scattering (the resonance between the beat wave and the trapped electron precession drift frequencies) suppress the low-{ital k}{sub {theta}} ({ital k}{sub {theta}}{rho}{sub {ital s}} {much lt}({ital L}{sub {ital n}}/{ital R}){sup 1/2}) modes while close interactions via ion Compton scattering (nonlinear ion Landau damping) produce a monotonically decreasing spectrum from {ital k}{sub {theta}}{rho}{sub {ital s}} {congruent}({ital L}{sub {ital n}}/{ital R}){sup 1/2} to {ital k}{sub {theta}}{rho}{sub {ital s}}{congruent}1 according to an approximate power law {ital k}{sup {minus}3}{sub {theta}}. Various fluctuation amplitudes at saturation and the fluctuation-induced anomalous particle and heat fluxes are found to be smaller than the mixing length estimates. The plasma confinement is predicted to improve with higher {ital T}{sub {ital i}}/ {ital T}{sub {ital e}}, more peaked density profile, larger aspect ratio, and higher plasma current. Also, a significant dependence of transport on the electron temperature gradient is found which could contribute to the rigidity of the electron temperature profile often experimentally observed.

• DOE Contract Number: AC02-76CH03073
• OSTI ID: 5838022
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 3:4; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700103 -- Fusion Energy-- Plasma Research-- Kinetics
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ANALYTICAL SOLUTION
ANNULAR SPACE
CLOSED CONFIGURATIONS
CLOSED PLASMA DEVICES
COLLISIONLESS PLASMA
CONFIGURATION
CONFINEMENT
DRIFT INSTABILITY
ELECTRON TEMPERATURE
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
FLUCTUATIONS
INSTABILITY
ION TEMPERATURE
LEPTONS
MAGNETIC FIELD CONFIGURATIONS
NONLINEAR PROBLEMS
PLASMA
PLASMA CONFINEMENT
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
SATURATION
SPACE
STEADY-STATE CONDITIONS
TEMPERATURE GRADIENTS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TOROIDAL CONFIGURATION
TRAPPING
TURBULENCE
VARIATIONS