Sawtooth oscillation in tokamaks

Technical Report · Wed Mar 01 04:00:00 EST 1989

DOI:https://doi.org/10.2172/6179465· OSTI ID:6179465

Park, W; Monticello, D A

A three-dimensional nonlinear toroidal full MHD code, MH3D, has been used to study sawtooth oscillations in tokamaks. The profile evolution during the sawtooth crash phase compares well with experiment, but only if neoclassical resistivity is used in the rise phase. (Classical resistivity has been used in most of the previous theoretical sawtooth studies.) With neoclassical resistivity, the q value at the axis drops from 1 to about 0.8 before the crash phase, and then resets to 1 through a Kadomtsev-type complete reconnection process. This ..delta..q/sub 0/ approx. = 0.2 is much larger than ..delta..q/sub o/ approx. = 0.01, which is obtained if classical resistivity is used. The current profile is strongly peaked at the axis with a flat region around the singular surface, and is similar to the Textor profile. To understand this behavior, approximate formulas for the time behavior of current and q values are derived. A functional dependence of sawtooth period scaling is also derived. A semi-empirical scaling is found which fits the experimental data from various tokamaks. Some evidence is presented which indicates that the fast crash time is due to enhanced effective resistivity inside the singular current sheet, generated by, e.g., microinstability and electron parallel viscosity with stochastic fields at the x-point. 16 refs., 5 figs.

• Research Organization: Princeton Univ., NJ (USA). Plasma Physics Lab.
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 6179465
• Report Number(s): PPPL-2601; ON: DE89009642
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
COMPUTER CODES
CONFINEMENT
EQUILIBRIUM
M CODES
MHD EQUILIBRIUM
NONLINEAR PROBLEMS
OSCILLATIONS
PLASMA CONFINEMENT
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS