Prospects for Self-Burning Operation in Heliotron-Type Fusion Reactor

Possible gaps between the current large helical device (LHD) experiment and the reactor operation have been investigated using the dynamic profile extrapolation model, which is validated by the LHD experiments. Self-burning solutions can be achieved under the wide range of fueling conditions. However, the minimum fusion output is rather high, and it may be incompatible with the allowable heat load to the in-vessel components. In order to meet the conditions, improvement of the confinement properties or increase of the magnetic field strength is required. In addition, auxiliary heating is one of the effective means for reducing the minimum fusion output by substituting fusion alpha heating, although this means abandoning the advantage of self-burning capability. Fuel dilution is enhanced due to the source profile effects of the alpha particle that is generated in the core plasma and fuel, which must be injected from the periphery. In order to mitigate the fuel dilution to below an acceptable level, sufficient fuel recirculation is required even if it leads to a reduction of burning efficiency.