Theory of weak ion temperature gradient driven turbulence near the threshold of instability
This paper presents a theory of weak ion temperature gradient driven turbulence near the threshold of instability. The model considers kinetic ions and adiabatic electrons in a sheared slab geometry. Linear theory shows that for /eta//sub th/ < /eta//sub i/ /approx lt/ /eta//sub th/ + (1+1//tau/)L/sub n//L/sub s/ (where /eta//sub th/ = 0.95 is the instability threshold and L/sub n//L/sub s/ << 1) then ..gamma.. << ..omega.. and a weak turbulence theory applies. The nonlinear wave kinetic equation indicates that ion Compton scattering is the dominant nonlinear saturation process. The wave kinetic equation is reduced to a differential equation for the spectrum, from which it is shown that the energy scatters to the linearly stable low k/sub y/ modes. The resulting spectrum of fluctuation levels (peaked about k/sub /perpendicular// /rho//sub i/ approx. = 1) is much lower than that suggested by naive extrapolation from the strong turbulence regime. The resulting ion thermal conductivity is also extremely low, so that strong ion heating can be expected to drive the ion temperature gradient to a level where this weakly turbulent threshold regime is surpassed. 27 refs., 4 figs., 1 tab.
- Research Organization:
- Texas Univ., Austin (USA). Inst. for Fusion Studies; California Univ., San Diego, La Jolla (USA). Dept. of Physics
- DOE Contract Number:
- FG05-80ET53088; FG03-88ER53275
- OSTI ID:
- 6822763
- Report Number(s):
- DOE/ET/53088-354; IFSR-354; ON: DE89005392
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PLASMA INSTABILITY
TEMPERATURE GRADIENTS
COMPTON EFFECT
FLUCTUATIONS
ION TEMPERATURE
KINETIC EQUATIONS
NONLINEAR PROBLEMS
THERMAL CONDUCTIVITY
TOKAMAK TYPE REACTORS
TRANSPORT THEORY
TURBULENCE
BASIC INTERACTIONS
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
EQUATIONS
INSTABILITY
INTERACTIONS
PHYSICAL PROPERTIES
SCATTERING
THERMODYNAMIC PROPERTIES
THERMONUCLEAR REACTORS
VARIATIONS
700107* - Fusion Energy- Plasma Research- Instabilities