Basic limitations in the RF linac/storage ring approach

Summary

Ignition of indirectly driven high-gain targets requires a specific power of typically 10¹⁶ W/g. Storage ring limitations and space charge effects in final focusing are shown to have an important impact on the minimum number of beams incident on the target. The increase in this number, if compared with the earlier HIBALL design, is largely due to the more stringent focusing requirements from indirect drive and a more careful evaluation of space charge effects. We compare the consequences on driver design of a two-converter target using 10 GeV ions with a «hotraum» target using 5 GeV ions. Parameters can be identified for which both scenarios have comparable risk in terms of exceeding conventional accelerator thresholds. For the 10 GeV case a spot radius of 3 mm is clearly more realistic (from the driver point of view) than the previously considered 1.3 mm radius.