MHD equilibrium analysis with anisotropic pressure in LHD

Abstract

The MHD equilibrium theory predicts that anisotropic plasma pressures parallel and perpendicular to field lines are not flux surface quantities. The method to identify the distortion of pressure from the surface average in experimental plasmas is not established. Here, the effects of the distortion on the measured values are investigated in the Large Helical Device (LHD). The MHD equilibria with the anisotropic pressure are studied using a 3D MHD equilibrium code, ANIMEC, which uses the bi-Maxwellian model as an anisotropic plasma pressure model in the 3D geometry. We study the position of magnetic axis and the magnetic flux obtained by magnetic diagnostic as candidates of characteristic parameter in the MHD equilibrium. As the results, we find that the position of magnetic axis is not sensitive to the distortion from the flux surface average, but the magnetic flux is sensitive to the distortion. This suggests that the magnetic diagnostics has a possibility to estimate the distortion from flux surface average.