Minimization of three-dimensional beam emittance growth in rare-isotope accelerator

Abstract

We describe a method to minimize the three-dimensional (3D) emittance growth (EG) in a rare-isotope accelerator. EG due to charge-stripping section can be minimized by optimizing transverse and longitudinal beam optics upstream of this section. EG in the bending section can be reduced by correcting higher-order chromatic abberation and momentum-compaction factor. EG in the superconducting linear accelerator (SCL) can be minimized by appropriately adjusting strengths of quadrupole magnets and rf voltages and phases of accelerating cavities. To validate our approach, we use it to analyze the driver linac for the in-fight fragmentation (IFF) separator of the RAON facility currently being built in Daejeon, Korea and show that redesign of the 90-degree bending section of the RAON accelerator together with adjustment of optics in the upstream and downstream SCLs can limit the 3D EG to 10% in the entire region of the driver linac. The emittance minimization was performed using a multi-objective genetic algorithm and the simplex method. Eff ects of various magnet errors on the beam-EG are also considered.