A 3-D resistive MHD simulation analysis of field reversal control in the reversed field pinch

A three-dimensional resistive MHD simulation code under the compressibility condition is applied to analysis of the field reversal control in the reversed field pinch (RFP). Simulation results have shown that a loss of the field reversal at the wall leads to increase of q-value on the axis and broad one of the q-profile, and also the rapid increase of the fluctuating magnetic energy due to nonlinear tearing modes with the m=1 and m=2 modes. By deepening the field reversal at the wall, the reversal surface moves inside the plasma, and the q-profile becomes narrow. As a result, a rapid growth and saturation of these tearing modes is suppressed by the field reversal control. (author)