Ion-optical layout of a powerful next-generation pre-separator for in-flight separation of relativistic rare isotopes

Rare isotope beams can be efficiently produced at relativistic energies via projectile fragmentation and projectile fission. Magnetic rigidity analysis in combination with atomic energy loss (Bρ–ΔE–Bρ method) in profiled matter placed at dispersive focal planes represents the tool for spatial separation in flight. The next-generation in-flight separators at high energies will consist of multiple degrader stages to provide intense monoisotopic fragment beams of all elements up to uranium. The pre-separator layout with the first degrader system holds many technical challenges, e.g. to handle the high-power primary beams characterized by a large range in time structure, from a DC beam to very short bunches. The latter requirement is particularly necessary for high-intensity primary beams bunched in short pulses (50 ns) for experiments with storage-rings. Large acceptance and high-separation power for uranium fission fragments and for exotic nuclei far from stability are the keys to serve the nuclear structure and astrophysical research at the frontiers. Consequently, large aperture magnets have to be applied to handle the inevitable large phase-space volume. The correction of higher-order image aberrations is a challenge and essential to achieve a high-separation power for the Bρ–ΔE–Bρ method.