Numerical method for linear MHD stability analysis without spectrum pollution

Aiba, Nobuyuki; Cooper, W. A.*; Gruber, R.*

When linear MHD stability is analyzed numerically, it is well-known that numerical instability called "spectrum pollution" sometimes appears. This numerical instability is usually caused due to inadequate choice of basis functions of finite elements, and the numerical method fixing this problem, named as Hybrid-Element-Method, was developed about 30 years ago. However, we identified that this instability is also caused due to missing to adopt numerical integral method. From both the viewpoint of basis functions and that of numerical integral method, we developed the new numerical method for linear MHD stability with Hybrid-Element-Method in combination with Gauss-Legendre quadrature. This new method realizes to suppress completely numerical instability even when plasma rotates.