Two approaches to the reactor-relevant high-beta plasmas with profile control in the Large Helical Device

摘要

From detailed optimization of configuration, volume averaged beta < 5% has been achieved in the Large Helical Device(LHD). While the heating efficiency was the main point to be optimized in this approach, to form a more peaked pressure profile is another promising approach towards the high beta regime. A higher electron density profile with a steeper pressure gradient has been formed by pellet injection. From the MHD stability analysis, this peaked pressure profile is stable against the ideal MHD modes. By both approaches, the central plasma beta β_0 reaches about 10%.