Magnetic field structure of experimental high beta tokamak equilibria
The magnetic field structure of several low and high ..beta.. tokamaks in the Columbia High Beta Tokamak (HBT) was determined by high-impedance internal magnetic probes. From the measurement of the magnetic field, the poloidal flux, toroidal flux, toroidal current, and safety factor are calculated. In addition, the plasma position and cross-sectional shape are determined. The extent of the perturbation of the plasma by the probe was investigated and was found to be acceptably small. The tokamaks have major radii of approx.0.24 m, minor radii of approx.0.05 m, toroidal plasma current densities of approx.10/sup 6/ A/m/sup 2/, and line-integrated electron densities of approx.10/sup 20/ m/sup -2/. The major difference between the low and high ..beta.. tokamaks is that the high ..beta.. tokamak was observed to have an outward shift in major radius of both the magnetic center and peak of the toroidal current density. The magnetic center moves inward in major radius after 20 to 30 ..mu..sec, presumably because the plasma maintains major radial equilibrium as its pressure decreases from radiation due to impurity atoms. Both the equilibrium and the production of these tokamaks from a toroidal field stabilized z-pinch are modeled computationally. One tokamak evolves from a state with low ..beta.. features, through a possibly unstable state, to a state with high ..beta.. features.
- Research Organization:
- Columbia Univ., New York (USA). Plasma Physics Lab.
- DOE Contract Number:
- FG02-86ER53222
- OSTI ID:
- 5405443
- Report Number(s):
- DOE/ER/53222-92; ON: DE86014329
- Country of Publication:
- United States
- Language:
- English
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