Large Helical Device Project

The Large Helical Device (LHD) is a heliotron-type toroidal fusion experimental device which will provide useful and reliable datasets for high-temperature helical plasmas with an equivalent Q value of 0.1 to 0.35. One of the crucial tasks of LHD is to demonstrate steady-state operations by taking the advantage of its magnetic configuration with currentless plasmas as well as built-in divertors. In this respect, the coil systems are fully superconducting (SC); consisting of a pair of helical coils, three pairs of poloidal coils and nine bus lines. All the SC coils have been successfully fabricated with high accuracy and they are presently in the final stage of assembly in a cryostat vessel along with outside preparations of plasma heating devices, diagnostic equipment and control systems. The first plasma operation is scheduled for the end of March 1998. The technological development of SC magnets through this project played a key role in LHD, and will also be useful for constructing future fusion reactors.