Local island divertor for the new edge control scenario

The new edge control scenario for the large helical device (LHD) with a local island divertor (LID) has been proposed, and technical and design studies of the LID have been done in detail. Although the LHD edge plasma control will primarily be done with a closed full helical divertor that utilizes a natural separatrix in the edge region, the LID that utilizes an m / n =1/1 island will be used in the early stage of the LHD experiment, prior to installing the closed full helical divertor. The advantage of the LID over the closed full helical divertor is the technical ease of hydrogen pumping because of the toroidally localized hydrogen recycling. This localized recycling, however, leads to high heat and particle fluxes onto divertor plates of an LID divertor head, and an average heat flux of 5 MW m − 2 has been designed for 3 MW steady state discharges. This paper will summarize the new edge control scenario proved experimentally, as well as the technical and design studies of the LID for LHD.