Research Of J-TEXT Tokamak Three-dimensional Magnetic Field Distribution

The magnetic configuration is essential for tokamak fusion experimental research. Intokamak with iron core, the core increases the difficulty of calculating the magneticdistribution. For simplifying the calculation, some two-dimensional analytic modelsincluding the effect of the iron core have been established. The assumptions of thesetwo-dimensional analytic models lead to different results with the actual magnetic fielddue to the distinctive boundary condition. In order to accurately calculate thethree-dimensional magnetic field distribution in the tokamak with iron core, this paper hasestablished a three-dimensional numerical model based on J-TEXT tokamak, comparedthe derived results of different models and investigated the toroidal asymmetry of themagnetic field distribution of the three-dimensional model of tokamak with iron core.The magnetic field distribution of J-TEXT tokamak contains not only the poloidalfield, but also the toroidal field. The ideal tokamak toroidal magnetic field is distributeduniformly toroidally. However, there are gaps between each toroidal field coils, causingthe changes on the toroidal. Therefore, in order to accurately calculate the ripple of thetororidal magnetic field, a system of toroidal field coils were precisely established. Andsome other features of the tororidal magnetic field were observed and studied.For maximizing the use of the work about poloidal magnetic field distribution withiron core condition and the accurate toroidal magnetic field distribution and better studyabout magnetic surface, designed and wrote the magnetic field lines tracing program. Withthe import of the database of magnetic fields distribution, the program can draw the locusof the magnetic line from the beginning position, leading to depict the magnetic surfacethe beginning point was on. And we compare different magnetic surface under differentcurrent excitation conditions.Via Finite Element Method, a poloidal field coils system with iron core and a systemof toroidal field coils were established. With these two systems, different magnetic fielddistribution were calculated under certain resolution and stored into severalthree-dimensional databases. As the magnetic fields can be linearly superposed, thesedatabases can be combined into a variety of magnetic distributions under different current conditions. At last, the databases were used to test the magnetic field tracing programwritten based on fourth-order Runge-Kutta method and made it possible for us to visuallyobserve the influence from different coils.