Neutral beam requirements for mirror reactors

The neutral beam requirements for mirror reactors as presently envisioned are 200 keV for the Field Reversed Mirror (FRM) and 1200 keV for the Tandem Mirror (TMR). The hybrid version of the Standard Mirror, FRM and TMR require 100 to 120 keV. Due to the energy dependence of atomic processes, negative ions should produce neutrals more efficiently than positive ions above some energy and below this energy, positive ions are probably more efficient. Thus, we conclude that hybrid reactors can use D ions but all of the fusion reactor designs call for D-ions to make the neutral beams. Trends in the energy requirements are discussed. The hardening of neutral beams against neutron and gamma radiation is discussed.