A study of barrier tandem mirrors as deuterium-deuterium (D-D) cycle reactors shows that high central cell beta and axisymmetry are crucial to even a moderate Q reactor. The SATYR system is large, with low-power density, and Q ∼ 5 to 6. A specialized axisymmetric configuration involving a plug-barrier cell with a levitated internal ring has been developed, though overall results are independent of the specific axisymmetric end plug configuration. The internal ring thermal analysis, including both surface and neutron volumetric heating, revealed unexpectedly that the operating time between recooling periods is limited by the time to reach the temperature limit of the superinsulator rather than the time for the superconductor to reach some predetermined level (e.g., 12 K for Nb-Ti). Further, it is found that a melt-layer within the ring is not required. A new pressure-vessel-type blanket design with pebble beds of ferritic steel produces high blanket multiplication and has long life (exceeding plant life). The overall study is presented along with detailed analyses in problem topics ranging from reactor physics on the one hand to detailed fusion engineering on the other. Specific subjects analyzed include reactor plasma performance, magnetic configuration development, coil design, blanket nuclear analysis and thermal hydraulics, blanket materials, structural analyses, and lifetime. A detailed comparison of economic, environmental, and safety scaling factors for D-D and deuterium-tritium (D-T) reactors reveals few incentives for aiming at D-D devices. It is concluded that the linearity of tandem mirrors, their inherent modularity and potential for steady-state operation, their predicted high-power density and high Q value, combined with the findings of this study, suggest that optimized D-T-cycle barrier tandem mirror reactors with axisymmetry and high βc have the potential to be economic reactor systems and should remain the major goal of mirror fusion research.
