Parameter Requirements for D- 3 He Helical Reactors

Parameter requirements are studied for D- 3 He helical reactors with three sizes based on the shifted large helical device (LHD) plasma (the major radius R = 3.6 m) with R = 14.5~18.5 m, and for a compact reactor based on a quasi-poloidal stellarator with R = 10.36 m. To achieve ignition in a D- 3 He helical reactor with the magnetic field strength Bo = 6 T, the confinement should be improved up to >2.4 times larger than the present LHD confinement, and the volume averaged beta 〈β 〉 = 14~21 %, the hot ion mode with the peak ion to electron temperature ratio Ti/ Te>1.5 and the heating power of 200~300 MW are necessary. The lower beta would be obtained in a larger machine and the neutron power can be reduced to 60 ~ 90 MW for 3 GW fusion power.