Streaming modes in final beam transport for heavy ion beam fusion

Abstract

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.