Simple spherical D-T targets for heavy-ion beam fusion

The results of 1-D numerical study are reported for a class of simple D-T targets driven by the beams of heavy ions. A simple target is defined as a uniform spherical metallic shell with the frozen D-T deposited on its inner surface and the D-T gas in the central cavity. Optimum target parameters have been found for several combinations of the three relevant driver parameters—the input energy Ein, the beam pulse duration tin, and the beam ion energy Eb. A simple box pulse profile was assumed. As a central set of driver parameters around which most of the calculations have been done, the values Ein = 6.12 MJ, tin = 17 ns, and Eb = 20 GeV have been adopted. It was found that all the targets from the class under consideration ignite uniformly over the entire fuel mass. Maximum energy gains amount to Gopt = 80–100. The physical picture of the target performance is analyzed in detail.

Streaming modes in final beam transport for heavy ion beam fusion

A key issue in the design of an HIF reactor cavity is the transport of the heavy ion beam from final focusing, across the cavity, to the target. Previous estimates have indicated that streaming instabilities will disrupt the beam transport for a background chamber gas pressure of 10−4 to 10−1 torr. The most attractive liquid lithium first wall reactor cavity designs produce a background gas density in just this pressure range. A detailed analysis of the streaming instabilities has now demonstrated that the beam can be transported through this background. The important fact that had been neglected is that a mode with a given wave number will grow for only a small fraction of the transport time, due to the changing beam and electron densities during transport. This analysis opens wide an attractive window for reactor cavity design.