Theory of tokamak edge turbulence: Drift-thermal instability-induced turbulence and ionization-driven drift wave turbulence

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6190898

Ware, A S

Two models of tokamak edge turbulence are examined: drift-thermal instability-induced turbulence and ionization driven drift wave turbulence. A simple model for drift-thermal instability-induced turbulence is derived and studied both analytically and numerically. Both nonlocal, nonlinear analytical calculations and three-dimensional computations are used. Potential and temperature fluctuation levels and radial correlation lengths are calculated and compared to numerical results. The saturation mechanism and the role of a fluctuation-generated shear flow are elucidated. The numerical calculations are used to obtain spectra and correlation lengths. A detailed comparison of analytical and numerical results is given. The theory of ionization-driven drift wave turbulence is presented in the context of a quasi-local model. Linear analysis reveals that ionization effects can destabilize collisional drift waves and can possibly induce parallel shear flow instabilities, as well. Nonlinear analysis indicates that energy is transferred from large to small stable scales and converted to ion kinetic energy. Results indicate mode coupling effects are dominant. Large fluctuation levels, in excess of mixing length expectations, are predicted. The ionization source drives a purely inward particle flux, which can explain the anomalously rapid up-take of particles which occurs in response to gas puffing. Finally, the development of a local model of ionization driven drift wave turbulence is extended to include the effects of magnetic shear and poloidal source asymmetry, as well as poloidal mode coupling arising from both magnetic drifts and the source asymmetry. Numerical and analytic investigation confirms that ionization effects can destabilize collisional toroidal drift waves. However, the mode structure is determined primarily by the ion curvature and del(B) drifts and is not overly affected by the poloidal source asymmetry.

• Research Organization: California Univ., San Diego, CA (United States)
• OSTI ID: 6190898
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700340* -- Plasma Waves
Oscillations
& Instabilities-- (1992-)
ANALYTICAL SOLUTION
CLOSED PLASMA DEVICES
DRIFT INSTABILITY
EDGE LOCALIZED MODES
INSTABILITY
NONLINEAR PROBLEMS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA MICROINSTABILITIES
SATURATION
THERMONUCLEAR DEVICES
THREE-DIMENSIONAL CALCULATIONS
TOKAMAK DEVICES
TURBULENCE