High beta tokamak research

This report discussion the following on high beta tokamaks: basic machine operation; operational parameter space; and plasma impurity control

High beta tokamak research. Progress report, November 1991--December 1992

This report discussion the following on high beta tokamaks: basic machine operation; operational parameter space; and plasma impurity control

High Beta Tokamak research. Technical report of research progress, February 24, 1993--August 24, 1993

During the past 6 months, experiments have been conducted with the HBT-EP tokamak in order to (1) test and evaluate diagnostic systems, (2) establish basic machine operation, (3) document MHD behavior as a function of global discharge parameters, (4) investigate conditions leading to passive stabilization of MHD instabilities, and (5) quantify the external saddle coil current required for DC mode locking. In addition, the development and installation of new hardware systems has occurred. A prototype saddle coil was installed and tested. A five-position (n,m) = (1,2) external helical saddle coil was attached for mode-locking experiments. And, fabrication of the 32-channel UV tomography and the multipass Thomson scattering diagnostics have begun in preparation for installation later this year

STABILIZATION OF KINK INSTABILITIES BY EDDY CURRENTS IN A SEGMENTED WALL AND COMPARISON WITH IDEAL MHD THEORY

ABSTRACT. The characteristics of external kink instabilities observed during wall stabilization studies in the HBT-EP tokamak have been compared with the predictions of ideal MHD theory, in order to examine the stabilizing role of a resistive wall that is segmented both toroidally and poloidally. The reconstructed equilibria, for discharges with different plasma-wall configurations, are consistent with external and internal magnetic measurements, measured soft X ray profiles and measured equilibrium wall eddy currents. The stability analysis of these equilibria predicts patterns of instability induced eddy currents for a model wall that is continuous and perfectly conducting, and these patterns are in good agreement with the ones observed on the HBT-EP segmented wall. These eddy currents account for the observed stabilization of fast ideal modes when the wall is fully inserted, consistent with the prediction of marginal stability