Author: Hasebe, H.
Paper Title Page
MOPFI025 Progress Towards High-Intensity Heavy-Ion Beams at RIKEN RIBF 333
  • O. Kamigaito, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa
    RIKEN Nishina Center, Wako, Japan
  The RIKEN RIBF(Radioactive Isotope Beam Factory) accelerator complex has been designed and constructed to provide heavy-ion beams from D to U ions with the energy of 400 MeV/u to the maximum. Though the goal intensity is 1 particle μ amperes for the whole mass range, the intensities of very heavy-ions from Ca to U are still not satisfactory. In 2012, owing to the intensity upgrade of 48Ca beams from ECR ion source, the beam current of 48Ca was 400 pnA which was improved by factors of 2 in comparison with that in 2011. Since 2011, the new injector RILAC2 has been successfully commissioned and operated very stably for beam service time, increasing the U beam intensity by an order of magnitude. Because it was no longer realistic to use carbon foil to strip the charge of intense U beams, in 2012 the Low-Z gas stripper system instead of the standard carbon foil system has been introduced and successfully worked. To accelerate the 238U64+ beams provided by the Low-Z gas stripper, modification of the following Fixed-frequency Ring Cyclotron was performed. In 2012, 15 pnA uranium beams which was four times larger than that provided in 2011 has been achieved.  
THPWO038 Electron Stripping of High-intensity 238U Ion Beam with Recirculating He Gas 3851
  • H. Imao
    RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan
  • T. Dantsuka, M. Fujimaki, N. Fukunishi, H. Hasebe, O. Kamigaito, M. Kase, H. Kuboki, K. Kumagai, T. Maie, H. Okuno, T. Watanabe, Y. Watanabe, K. Yamada, Y. Yano
    RIKEN Nishina Center, Wako, Japan
  Next-generation in-flight RI beam facilities such as RIBF and FRIB pursue powerful and energetic 238U ion beams to produce thousands of new isotopes. For their efficient acceleration, a durable electron stripper in the intermediate energy region around 10-20 MeV/u is indispensable. However, there is no available stripper for the U beams with the intensity of more than 1 puA so far because of the lifetime problem of thin solid strippers caused by high energy loss.  In the present study, a novel electron stripping system employing high-flow rate He gas circulation (200 L/min) has been developed. He gas with the thickness of 0.6 mg/cm2 is confined and separated from beamline vacuum using five-stage differentially-pumped sections. To avoid huge gas consumption, a clean gas recycling is achieved with multi-stage mechanical booster pump array. The recycling rate of He gas was achieved as more than 99%. The system was successfully operated in user runs with U35+ beams more than 1 puA injected at 10.8 MeV/u for the first time. U64+ beams were stably delivered to subsequent accelerators with the stripping efficiency of 23% without any deterioration of the system.