Abstract: The Tokamak equilibrium fitting numerical calculation code EFIT is modified to study the MHD (magnetohydrodynamics) equilibrium in an EAST device. The divertor configuration in the steady-state phase of the EAST device is simulated with the modified cede. A method is proposed to satisfy the free boundary equilibrium for non-symmetrical current, by using linear equation array with the current of poloidal field coils as the main confined condition and expected configuration as the auxiliary confined condition. It is shown that the method can be used to obtain the equilibrium configuration which is induced by non-symmetrical current, and to solve the non-convergence problem of a free boundary equilibrium.

Key words: Tokamak, MHD equilibrium, EFIT code