A free-boundary Tokamak Equilibrium Solver (TES), developed for advancedstudy of tokamak equilibra, is described with two distinctive features. One isa generalized method to resolve the intrinsic axisymmetric instability, whichis encountered after all in equilibrium calculation with a free-boundarycondition. The other is an extension to deal with a new divertor geometry suchas snowflake or X divertors. For validations, the uniqueness of a solution isconfirmed by the independence on variations of computational domain, themathematical correctness and accuracy of equilibrium profiles are checked by adirect comparison with an analytic equilibrium known as a generalized Solovevequilibrium, and the governing force balance relation is tested by examiningthe intrinsic axisymmetric instabilities. As a valuable application, asnowflake equilibrium that requires a second order zero of the poloidalmagnetic field is discussed in the circumstance of KSTAR coil system.
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