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.