Edge plasma control with a local island divertor

Abstract A divertor head of local island divertor (LID) that utilizes an m / n =1/1 island was installed on the large helical device (LHD) after the fifth experimental campaign in 2001–2002. Up to the fifth campaign, the effect of the LID magnetic configuration on plasma performance was studied without the divertor head. It was found that the island itself deteriorates plasma parameters such as electron temperature, stored energy, etc., and that the ergodic layer around the natural helical separatrix plays a role on preventing impurities from penetrating into the core plasma.