Centers & Labs

RIKEN Nishina Center for Accelerator-Based Science

Accelerator R&D Team

Team Leader: Hiroki Okuno (D.Sci.)
Hiroki  Okuno(D.Sci.)

We are developing the key hardware in upgrading the RIBF accelerator complex. Our primary focus and research is charge stripper which plays an essential role in the RIBF accelerator complex. Charge strippers remove many electrons in ions and realize efficient acceleration of heavy ions by greatly enhancing charge state. The intensity of uranium beams is limited by the lifetime of the carbon foil stripper conventionally installed in the acceleration chain. The improvement of stripper lifetimes is essential to increase beam power towards the final goal of RIBF in the future. We are developing the low-Z gas stripper. In general gas stripper is free from the lifetime related problems but gives low equilibrium charge state because of the lack of density effect. Low-Z gas stripper, however, can give as high equilibrium charge state as that in carbon foil because of the suppression of the electron capture process. Another our focus is the upgrade of the world's first superconducting ring cyclotron.

Main Research Field



  • Superconductivity
  • Charge stripper
  • liquid He
  • Cyclotron
  • nuclear transmutation

Selected Publications

  1. Ohnishi, J., Nakagawa, T., Higurashi, Y., Okuno, H., Kusaka, K., Goto, A.:
    "Construction and test of the superconducting coils for RIKEN SC-ECR ion source"
    Proc. of the 11th European Particle Accelerator Conference (EPAC 2008), Genoa, Italy, 2008, p433-435
  2. Ohnishi, J., Okuno, H., Fukunishi, Yamada, K., Goto, A., Yano, Y.:
    "The magnetic field of the superconducting ring cyclotron"
    Proc. the 18th International Conference on Cyclotrons and Their Applications, Giardini Naxos, Italy, 2007, p429-431
  3. Kuboki, H, Okuno, S. Yokouchi, H., Hasebe, Kishida, T., Fukunishi, N., Kamigaito, O., Goto, A., Kase, M., Yano, Y.:
    "Charge-state distribution measurements of 238U and 136Xe at 11 MeV/nucleon using gas charge stripper"
    Physical Review Special Topics - Accelerators and Beams 13, 093501 (2010)
  4. Hasebe, H., Okuno, H., Kuboki, H., Ryuto, H., Fukunishi, N., Kamigaito, O., Goto, A., Kase, M., Yano, Y.:
    "Development of long-life carbon stripper foils for uranium ion beams"
    Proc. of the 24th world conference of the INTDS, Caen, France, 2008, in print.
  5. Hasebe, H., Ryuto, H., Fukunishi, N., Goto, A., Kase, M., Yano, Y.
    "Polymer coating method developed for carbon stripper foils"
    Nuclear Instruments and Methods in Physics Research A590 (2008) p13-17
  6. Imao, H., Okuno, H., Kuboki, H., Yokouchi, S., Fkunishi, Kamigaito, O., Hasebe, H., Watanabe, T., Watanabe, Kase, M., Yano, Y.:
    "Charge stripping of 238U ion beam by helium gas stripper"
    Physical Review Special Topics - Accelerators and Beams 15, 123501 (2012)
  7. Okuno, H., Fkunishi, N., Goto, A., Hasebe, H., Imao, H., Kamigaito, O., Kase, M., Kuboki, H., Yano, Y. S. Yokouch, and A. Herschcovitch:
    "Low-Z Gas stripper as an alternative to carbon foils the acceleration of high-power uranium beams"
    Physical Review Special Topics - Accelerators and Beams 14, 033503 (2011)
  8. Okuno, H., Fukunishi, N., Fujinawa, T., Higurashi, Y., Ikezawa, E., Kamigaito, O., Kase, M., Nakagawa, T., Ohnhishi, J., Sato, Y., Yano, Y., Ostroumov, P.:
    "Heavy Ion Accelerators for RIKEN RI Beam Factory and Upgrade Plans"
    Proc. of the 42nd ICFA Advanced Beam Dynamics Workshop on High-Intensity, High-Brightness Hadron Beams, Nashville USA, (2008) 416
  9. Okuno, H., Adelmann, A., Yang, J.:
    "Possibility of Roud Beam Formation in RIBF Cyclotrons"
    Proc. of ICAP'09 San Francisco, Sept., 2009
  10. Okuno, H., Yamada, K., Ohnishi, J., Fukunishi, N., Ikegami, K., Maie, T., Hasebe, H., Kamigaito, O., Sakamoto, N., Kumagai, K., Yokouchi, S., Kase, M., Goto, A., Yano, Y.:
    "Commissioning of the Superconducting Ring Cyclotron for the RIKEN RI Beam Factory"
    IEEE Trans. Appl. Supercond., 18 (2008) 226

Lab Members

Principal Investigator

Hiroki Okuno
Team Leader

Core Members

Hiroshi Imao
Senior Research Scientist
Jun-ichi Ohnishi
Senior Technical Scientist
Hiroo Hasebe
Nishina Center Technical Scientist
Naoya Ikoma
Junior Research Associate