Magnetohydrodynamic Equilibrium of Heliotron J Plasmas

Magnetohydrodynamic (MHD) equilibria of Heliotron J plasma are investigated by using the HINT code. HINT calculates an MHD equilibrium by using the relaxation method, which calculates the time evolution of dissipative MHD equations. Since HINT uses Eulerian rectangular grids, it does not assume nested flux surfaces. In the standard configuration, magnetic islands appear inside the plasma in spite of low (<> ~ 0.4%). The width of the islands depends on the pressure distribution. To reduce island width, feedback control of the external vertical field is introduced. Because of the effect of the external vertical field, magnetic islands are suppressed. The effects of the net toroidal currents on MHD equilibrium are also investigated. The rotational transform is changed by the currents, but the Shafranov shift is almost unaffected. The width of the islands changes because of the change in the rotational transform.