Experimental Confinement Studies Beyond ITER

The advantages of stellarators are discussed with an emphasis on the high density limit more than 10 times higher than that of tokamaks with the equivalent magnetic field strength. The comparison between stellerators and tokamaks in the light of the new paradigm of plasma turbulence and zonal flows is presented to propose a new optimization principle of magnetic field configuration. The roles of low-temperature devices should be recognized for further understanding of the plasma confinement even in the era of burning state plasmas