Design considerations for final pulse compression with bending for heavy ion fusion drivers

Immediately prior to final focus onto a fusion target, heavy ion driver beams are compressed in length by typically an order of magnitude. This process is simultaneous with bending through large angles to achieve the required target illumination configuration. The large increase in beam current is accommodated by a combination of decreased lattice period, increased beam radius, and increased strength of the beamline quadrupoles. However, the large head-to-tail velocity tilt (up to 5%) needed to compress the pulse results in a very significant dispersion of the pulse centroid from the design axis. A principal design goal is to minimize the magnitude of the dispersion while maintaining approximate first order achromaticity through the complete compression/bend system. Configurations of bends and quadrupoles which achieve this goal while simultaneously maintaining a locally matched beam-envelope have been analyzed