Selecting method of the dominant eigenmodes of eddy currents for plasma control study

A method for selecting the dominant eigenmodes of the eddy currents which affect plasma equilibria and its control is presented. The method is based on the blockline diagram analysis of a control model. The passive effects of conductors due to eddy currents are classified into 6 groups and each effect such as a shell effect and a shield effect is expressed in a simple summation of that of each eigenmode. This property is used to select the dominant eigenmodes for a plasma control study. The application of this method is made for JT-60 and 35 dominant eigenmodes are selected from among 464 eigenmodes obtained from the eddy current analysis. The effect due to these 35 dominant eigenmodes approximates well to that due to 464 eigenmodes and it is shown that the dimension of the control model is well reduced by using this method. (author)