Development of superconducting coils

Development of superconducting system for the Large Helical Device (LHD) is summarized. The LHD is a fully superconducting heliotron type fusion experimental device under construction at the National Institute for Fusion Science (NIFS). The superconducting coils for the LHD consist of two helical coils and three pairs of poloidal coils. Their magnetic stored energy becomes 1.6 GJ and the LHD is one of the largest superconducting systems in the world. To construct such a large scale superconducting system, not only we have to accumulate existing technologies but we also have to develop new technologies. The items of research and development for the superconducting coil system of LHD, i.e. the superconducting test facilities, the development of superconducting conductors and coils for the helical coils and the poloidal coils, the development of the superconducting bus line, cooling and excitation tests on a single inner vertical coil for the LHD, are reported. (author)