A D-³He fusion is attractive for achieving a safer and cleaner fusion reactor. Recent demonstration of feasibility of a D-³He spherical tokamak reactor⁽¹⁾ encourages studies of a D-³He helical reactor. To see the future prospect of LHD type experiments, it is also important to study a D-³He helical reactor. In this paper, we examine parameter requirements for D-³He helical reactors with three sizes (R=14.5,16.6 and 18.5 m) based on the shifted LHD plasma (R=3.6 m), and for a compact reactor (R=9.6 m) based on a quasi-poloidal stellarator⁽²⁾. We use 0-D particle and power balance equations for D-³He, D-D and D-T fusions. The density limit scaling is used for controlling the heating power. Fusion power is regulated by a PID controller with the fusion power and fuel ratio signals. The confinement factor γ_HH over the present LHD confinement time (1.6xISS95 scaling) is used. The prompt loss of all the fusion products is assumed to be zero and all the effective particle confinement time ratios to be τ_p/τ_E=2. D-³He ignition is possible in the helical reactor with R=14.5m, <a_p>=2.6 m, B_o=6 T, the wall reflectivity R_eff=0.99, the high beta <β>~21 %, γ_HH=3, the heating power P_EXT=200 MW, and fuel ratio D:³He=0.45:0.55. The neutron power is 60 MW, the peak electron density is 3.9x10²⁰ m^-3 and the peak ion temperature is 115 keV. Bremsstrahlung loss 0.9 GW to the first wall and the conduction loss 1.8 GW to the divertor are converted to the electricity of 1.1 GW with the conversion efficiency of 40 %. Heat flux to the first wall is 0.74 MW/m²and neutron wall loading is 0.04 MW/m². The divertor heat flux provides a challenging task. Helical reactors with other sizes have similar performances.

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