Experience with Heavy Ion Charge Strippers at RIKEN

Abstract:  The RIKEN Radioactive Isotope Beam Factory (RIBF) has been successfully operating for over ten years since the first beam at the end of 2006 with the aim of accessing the unexplored region on the nuclear chart, far from stability. The continuous efforts have improved the performance of the RIBF accelerator complex. We did a lot of things to upgrade accelerator performance, including construction a 28-GHz superconducting ECR ion source with a new injector linac and development of new types of charge strippers. This seminar focuses on the charge strippers. The RIBF accelerator complex uses the two charge strippers for effective acceleration of the uranium ions. These charge strippers could be a bottle-neck problem especially in high power operation. We carried out elaborating R&D works to replace the conventional carbon foils with the new types of the charge strippers which can survive irradiation of high intensity heavy ion beams, reaching to the solutions of helium gas stripping for the first stripper and rotating disks using highly oriented graphene sheet for the second one so far. This talk overviews R&D works for the charge strippers since 2008 and reports the present status of the charge strippers currently used for the operation with future prospect.