A demonstration of magnetic field optimization in LHD

An optimized configuration of the neoclassical transport and the energetic particle confinement to a level typical of so-called “advanced stellarators” is found by shifting the magnetic axis position in LHD. Electron heat transport and NBI beam ion distribution are investigated in low-collisionality LHD plasma in order to study the magnetic field optimization effect on the thermal plasma transport and the energetic particle confinement. A higher electron temperature is obtained in the optimized configuration, and the transport analysis suggests a considerable effect of neoclassical transport on the electron heat transport assuming the ion-root level of radial electric field. Also a higher energetic ion distribution of NBI beam ions is observed showing the improvement of the energetic particle confinement. These obtained results support a future reactor design by magnetic field optimization in a non-axisymmetric configuration.