DIVERTOR EXPERIMENT IN LARGE HELICAL DEVICE

This paper describes the major objectives of the LHD divertor experime nt which is proposed to produce currentless-steady-state plasmas with high performance and without any current disruption. Since further imp rovement in confinement is a common and general requirement for fusion research including the LHD project, it is also necessary to develop t he edge plasma control techniques and to understand the physical behav iour in the LHD divertor, i.e. the newly developed continuous helical divertor and a local island divertor (LID) concepts. In order to achie ve these objectives, there were several key issues in physics and tech nology, which had to be resolved through careful investigation before the LHD experiment could start. In this paper, we summarize the recent progress of the physics understanding of divertor functions, divertor plasma operation scenarios, and properties of the LHD magnetic field structure in addition to the experimental planning. We also describe t he recent result of an LID experiment in the CHS device, which demonst rated the possibility of edge particle and heat control by the LID.