Aspect ratio dependencies of D-³He fueled tokamak reactors

Ignition capability is studied and compared for two types of D-³He spherical tokamak (ST) and medium aspect ratio tokamak (MT) reactors. The required power fraction to ions for maintaining the hot ion mode, which is indispensable for D-³He fusion, is smaller in a ST reactor than that in a MT reactor due to the lower synchrotron radiation loss. It is found that the nuclear elastic scattering capable of supplying 40% of the fusion energy to ions is enough to maintain the hot ion mode in the D-³He ST reactor with the high wall reflectivity. For achieving the D-³He MT reactor, the power fraction to ions should be additionally increased.