Comparing linear ion-temperature-gradient-driven mode stability of the National Compact Stellarator Experiment and a shaped tokamak
- Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
One metric for comparing confinement properties of different magnetic fusion energy configurations is the linear critical gradient of drift wave modes. The critical gradient scale length determines the ratio of the core to pedestal temperature when a plasma is limited to marginal stability in the plasma core. The gyrokinetic turbulence code GS2 was used to calculate critical temperature gradients for the linear, collisionless ion temperature gradient (ITG) mode in the National Compact Stellarator Experiment (NCSX) and a prototypical shaped tokamak, based on the profiles of a JET H-mode shot and the stronger shaping of ARIES-AT. While a concern was that the narrow cross section of NCSX at some toroidal locations would result in steep gradients that drive instabilities more easily, it is found that other stabilizing effects of the stellarator configuration offset this so that the normalized critical gradients for NCSX are competitive with or even better than for the tokamak. For the adiabatic ITG mode, NCSX and the tokamak had similar adiabatic ITG mode critical gradients, although beyond marginal stability, NCSX had larger growth rates. However, for the kinetic ITG mode, NCSX had a higher critical gradient and lower growth rates until a/L{sub T} Almost-Equal-To 1.5 a/L{sub T,crit}, when it surpassed the tokamak's. A discussion of the results presented with respect to a/L{sub T} vs. R/L{sub T} is included.
- OSTI ID:
- 22113437
- Journal Information:
- Physics of Plasmas, Vol. 20, Issue 2; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CONFIGURATION
CRITICAL TEMPERATURE
CROSS SECTIONS
ELECTRON TEMPERATURE
H-MODE PLASMA CONFINEMENT
ION TEMPERATURE
PLASMA
PLASMA DRIFT
PLASMA INSTABILITY
PLASMA SIMULATION
STABILITY
STELLARATORS
TEMPERATURE GRADIENTS
THERMONUCLEAR REACTORS
TOKAMAK DEVICES
TURBULENCE
WAVE PROPAGATION