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The poloidal field magnet system of the KSTAR consists of three pairs of coils using the cable-in-conduit conductors cooled by forced super-critical helium. The conductor of PF5 is Nb/sub 3/Sn superconductor with Incoloy 908 conduit, and that of PF6 and PF7 is NbTi superconductor with SS 316LN. The PF coils are self-supporting with regard to radial loads, and they are arranged symmetrically with respect to the equatorial plane. PF5 coil is connected to the TF coil structure at eight points by hinges, while PF6 and PF7 coils are connected at sixteen points by flexible plates to allow relative radial movements. In order to investigate the structural integrity, structural analysis has been conducted including buckling and fatigue analyses. The major design loads are dead weight, assembly loads, thermal load due to cool down, and electromagnetic loads under the critical load conditions. It is found that the PF magnet structures can safely withstand all operating conditions. In addition, AISI 316LN can be substituted for JJ1 as the material of the PF coil structures.

The central solenoid (CS) magnet system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device consists of four pairs of segmented CS coils and a CS coil structure. The maximum repulsive force between CS coils is about 12 MN. The functions of the CS structure are to apply preload on the CS coils and to support the repulsive force between CS coils during operation. The designed axial compression of 15 MN at 4.5 K will be applied partly by assembling the preload structure at room temperature with preload of about 13.4 MN and partly by the thermal contraction difference between the CS coils and the structure during cool down. Additional preload will be given by minute adjustment of wedges. The structural analysis of the CS magnet system has been performed to verify the CS structure design reliability.

The toroidal field (TF) magnet system of Korea Superconducting Tokamak Advanced Research (KSTAR) device consists of 16 superconducting coils enclosed in steel cases. The TF cases are wedged along the inboard straight legs to sustain in-plane centering forces. The inter-coil structures contain adjustable shear keys and conical bolts to provide pre-loading in toroidal direction and to resist in-plane and out-of-plane forces, which are the most critical loads on the TF magnet system. For effective cooling of the TF case, a pad-type cooling channel has been designed to ensure structural and thermal stability. In order to investigate the structural integrity and to increase the structural reliability of the KSTAR magnet system, structural analyses have been conducted. From the analysis results, it has been found that the TF magnet structure can safely withstand the reference scenario operations.