NUMERICAL ANALYSIS OF SUPERCONDUCTOR RING AND SLAB IN RESPECT OF RIPPLE REDUCTION IN TOKAMAK

Abstract

In numerical analysis superconductors are treated as non-linear conductors with virtual conductivity that is to be changed so that the current density takes the critical yalue according to the critical state model. The algorithm proposed by Uesaka does this by decreasing the initial virtual conductivity until the current density reaches the critical value. However, this algorithm cannot handle correctly the situation when the eiectric field approaches zero, which is the case when the external field becomes constant. The virtual conductivity should be increased to infinity in order to sustain the critical current. To simulate this critical state, the steady state of finite elernents was introduced. Two algorithms that apply this state v/ere developed. and together with the Uesaka algorithrn they were used to study the application of superconductor rings and slabs to reduce magnetic ripple in t.he tokamak.