INFLUENCE OF EXTERNAL TOROIDAL FLUX ON LOW-ASPECT-RATIO TOROIDAL PLASMA

摘要

In the HIST device, the external flux is generated by two kinds of currents: the current I_s flowing along thernsymmetry axis and the bias coil current I_D. The influence of the external flux on the MHD equilibrium and stabilityrnof the low-aspect-ratio toroidal plasma in the HIST device is investigated numerically. Equilibrium configurationsrnof the low-aspect-ratio toroidal plasma in the HIST device are numerically determined by means of the combinationrnof FDM and BEM. The influence of I_s and I_D on their stability is also investigated by using the Mercier criterion.rnThe results of computations show that the Mercier limit decreases to zero with increasing I_s and with decreasingrnI_D. Moreover, either a further increase in I_s or a further decrease in I_D raises the Mercier limit considerably.rnBesides, the equilibrium configuration in the HIST device changes its state from spheromak through ultra-low qrnto tokamak with increasing I_s and with decreasing I_D.