Study of a helical axis heliotron

Optimization studies have been done for the helical axis heliotron configuration. One purpose is to find a configuration suitable for experimental studies of the basic properties of a helical axis heliotron. In the present study, the role of the bumpy field component (toroidal mirror ratio) in MHD stability and neoclassical confinement for this type of configuration is examined. The physical mechanism of the improvement of the neoclassical transport through control of the bumpy field component is clarified. The physics design and current status of the new helical axis heliotron device, Heliotron J, are also described.