Analysis of the eddy current in multi-shell torus system

In a large tokamak device without an iron core, the formulation of the eddy current or the induced current on torus components such as a vacuum vessel, toroidal coils, support structures, a center column and passive poloidal coil groups has been carried out according to the finite element circuit theory. Assuming an each conductive plate to be infinitely thin, the magnetic interaction between conductive surfaces is obtained by the energy integration for the corresponding eigen mode of eddy current on the respective surface and a set of given circuit equations in this torus system is solved again by the method of eigen value expansion. Keeping an advantage of the finite element circuit method, i.e. no restriction for the torus cross-section, the aspect ratio, the inhomogeneity of the resistivity of conductive surface, this method gives no restriction for the number of components of the torus system. Since the present method is applicable to the quantitative analysis of eddy current in the actual tokamak device composed of many components, it will be possible to discuss quantitatively the electromagnetic load and the effects of the eddy current field on the control of a plasma cross-section and its desired position according to the required accuracy. (author)