Laboratory Head
Michiharu WADAD.Sci.
  • Now writing...


Research Areas

A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being built as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell. The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of dc electric fields and inhomogeneous rffields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV Li-8 ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. First spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic Be ions from the RIPS were trapped and laser cooled in a linear rf trap and the ground state hyperfine splittings of Be-7, Be-11 were measured with 0.1 ppm precision. Optical transition frequencies of Be-7, Be-9, Be-10, Be-11 were also measured with 1 ppb precision. From these two experiments, we investigate nuclear charge and magnetization radii. Other spectroscopy experiments using the slow RI-beams are also under progress in off-line setups. A collinear fast beam apparatus for nuclear charge radii measurements was build and tested with stable Ar+ ion beams. A multi-reflection time-of-flight mass spectrograph was build for precise and fast measurements of short-lived radioactive nuclei. A high mass resolving power of 140,000 for K and Rb isotopes has been achieved with a 5 ms measurement period. It is equivalent to use a nonexsisting 90 T magnet for a Penning trap mass spectrometer.

Research Subject

  1. Development and constraction of the next-generation slow RI-beam facility -- SLOWRI
  2. Precision laser spectroscopy of trapped radioactive Beryllium isotope
  3. Development of a multi-reflection time-of-flight mass spectrograph for precision mass measurements of short-lived nuclei
  4. Development of collinear fast beam apparatus for isotope shift measurements
  5. Development of parasitic slow RI-beam using gas cell and resonance laser ionization scheme

List of Selected Publications

  1. Schury, P., Wada, M., Ito, Y., Kaji, D., Arai, F., MacC ormick, M., Murray, I., Haba, H., Jeong, S., Kimura, S., Koura, H., Miyatake, H., Morimoto, K., Morita, K., Ozawa, A., Rosenbusch, M., Reponen, M., Söderström, P.-A., Takamine, A., Tanaka, T., Wollnik, H.:
    "First online multireflection time-of-flight mass measurements of isomer chains produced by fusion-evaporation reactions: Toward identification of superheavy elements via mass spectroscopy"
    Physical Review C 95, 011305(R) (2017)
  2. Takamine, A., Wada, M., Okada, K., Sonoda, T., Schury, P., Nakamura, T., Kanai, Y., Kubo, T., Katayama, I., Ohtani, S., Wollnik, H., Schuessler, H.A.:
    "Hyperfine Structure Constant of the Neutron Halo Nucleus 11Be+"
    Phys. Rev. Lett., 112, 162502 (2014)
  3. Ito, Y., Schury, P., Wada, M., Naimi, S., Sonoda, T., Mita, H., Arai, F., Takamine, A., Okada, K., Ozawa, A., Wollnik, H.:
    "Single-reference high-precision mass measurement with a multireflection time-of-flight mass spectrograph"
    Phys. Rev. C 88, 011306® (2013)
  4. Okada, K., Wada, M., Nakamura, T., Takamine, A., Lioubimov, V., Schury, P., Ishida, Y., Sonoda, T., Ogawa, M., Yamazaki, Y., Kambara, T., Kanai, Y., Kojima, T.M., Yoshida A., Kubo, T., K., Katayama, I., Ohtani, S., Wollnik, H., Schuessler, H.A.:
    "Precision Measurements of the hyperfine Structure of Laser-Cooled Radioactive 7Be+ ions Produced by Projectile Fragmentation"
    Phys. Rev. Lett. 101, 212502 (2008)
  5. Takamine, A., Wada, M., Okada, K., Nakamura, T., Schury, P., Sonoda, T., Lioubimov, V., Iimura, H., Yamazaki, Y., Kanai, Y., Kojima, T.M., Yoshida, A., Kubo, T., Katayama, I., Ohtani, S., Wollnik, H., Schuessler, H.A.:
    "Isotope shift measurements of 11,9,7Be+"
    Eur. Phys. J. A. 10883-5 (2009)
  6. Schury, P., Wada, M., Ito, Y., Arai, F., Naimi, S., Sonoda, T., Wollnik, H., Shchepunov, V.A., Smorra, C., Yuan, C.:
    "A high-resolution multi-reflection time-of-flight mass spectrograph for precision mass measuremets at RIKEN/SLOWRI"
    Nucl. Inst. And Meth. Phys. Res. B335, 39 (2014)
  7. Sonoda, T., Tsubota, T., Wada, M., Katayama, I., Kojima, T.M., Reponen, M.:
    "A gas circulation and purification system for gas-cell based low-energy RI-beam production"
    Rev. Sci. Inst., 87, 065104 (2016).
  8. Wada, M.:
    "Genealogy of gas cells for low-energy RI-beam production"
    Nucl. Inst. and Meth. Phys. Res. B 317, 450 (2013).
  9. Takamine, A., Wada, M., Ishida, Y., Nakamura, T., Okada, K., Yamazaki, Y., Kambara, T., Kanai, Y., Kojima, T.M., Nakai, Y., Oshima, N., Yoshida, A., Kubo, T., Ohtani, S., Noda, K., Katayama, I., Hostain, P., Varentsov, V., Wollnik, H.:
    "Space-charge effect in the catcher gas cell of a rf ion guide"
    Rev. Sci. Instrum. 76, 103503 (2005)
  10. Wada, M., Ishida, Y., Nakamura, T., Yamazaki, Y., Kambara, T., Ohyama, H., Kanai, Y., Kojima, T.M., Nakai, Y., Yoshida, A., Kubo, T., Matsuo, Y., Fukuyama, Y., Okada, K., Sonoda, T., Ohtani, S., Noda, K., Kawakami, H., Katayama, I.:
    "Slow RI-beams from projectile fragment separators"
    Nucl. Instrum. and Meth. B204, 570-581 (2003)


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