Toshiyuki Kubo

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identi...

Spectroscopy of 32Ne and the "Island of Inversion".

We report on the first spectroscopic study of the N=22 nucleus 32Ne at the newly completed RIKEN Radioactive Ion Beam Factory. A single gamma-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a 226 MeV/u 32Ne beam on a carbon target and proton removal from 33Na at 245 MeV/u. This transition is assigned to the deexcitation of the first Jpi=2+ state in 32Ne to the 0+ ground state. Interpreted through comparison with state-of-the-art shell-model calculations, the low excitation energy demonstrates that the island of inversion extends to at least N=22 for the Ne isotopes.

Identification of New Neutron-Rich Isotopes in the Rare-Earth Region Produced by 345 MeV/nucleon 238U

A search for new isotopes in the neutron-rich rare-earth region has been carried out using a 345 MeV/nucleon 238U beam at the RIKEN Nishina Center RI Beam Factory. Fragments produced were analyzed and identified using the BigRIPS in-flight separator. We observed a total of 29 new neutron-rich isotopes: 153Ba, 154,155,156La, 156,157,158Ce, 156,157,158,159,160,161Pr, 162,163Nd, 164,165Pm, 166,167Sm, 169Eu, 171Gd, 173,174Tb, 175,176Dy, 177,178Ho, and 179,180Er.

Industrial Application of Radioactive Ion Beams at the RIKEN RI Beam Factory

The Radioactive Ion Beam Factory (RIBF) at RIKEN is a heavy‐ion accelerator facility that can provide intensive beams of radioactive isotopes (RI beam) produced at in‐flight RI‐beam separators. While the facility is used for experiments of various basic research fields, a new project has been started to open the facility to non‐academic proposals from industry. We show an overview of the RIBF and the project of industrial use, and present a utilization of an RI‐beam for development of wear diagnostics of industrial materials.

Invariant Mass Spectroscopy of

Unbound states in 17C were investigated via one-neutron knockout of 18C. The experiment was performed using SAMURAI spectrometer in RIBF at RIKEN. By invariant mass spectroscopy, three resonances were measured at excitation energies of 3.03(12), 2.74(3), and 4.03(6)u2005MeV as preliminary results. For the excited state at 2.74(3)u2005MeV, the parallel momentum distribution was satisfactorily described by the distribution calculated for p-wave knockout from 18C.

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A systematic study of the nucleon density distributions of finite nuclei is important for understanding the isospin dependence of the nuclear many-body system. For example, the neutron skin thicknesses are known to be strongly correlated with the density-dependent term of the symmetry energy, and the isospin-dependent term of the nuclear equation of state. In previous works, we have succeeded in extracting the neutron density distributions of stable nuclei such as Sn and Pb isotopes via proton elastic scattering. At the same time we have launched a new project aimed at measuring the Elastic Scattering of Protons with RI beams (ESPRI) with the purpose of the extraction of proton and neutron density distributions of unstable nuclei. We have newly developed and tested unique devices for the ESPRI measurements at NIRSHIMAC in Chiba and GSI in Germany. Finally, we have successfully performed the ESPRI experiment at RIBF in April, 2013. Unlike the case of stable nuclei, however, we have no information on the nuclear charge densities of unstable nuclei. Thus, we have proposed a new method to extract proton and neutron densities via two-energy proton elastic scattering. This method is based on the large difference between the energy dependences of the p-p and p-n interactions. Recently, we performed an experiment to demonstrate this new method using real data of Zr isotopes. In this report, we show the preliminary results of Zr only. For other isotopes (Zr), the analysis is still ongoing. The experiment was performed at RCNP, Osaka University. Polarized proton elastic scattering from Zr and Ni at 200 and 300 MeV was measured by using the Grand Raiden magnetic spectrometer. Figure 1 shows the angular distributions of cross sections (dσ/dΩ) and the analyzing powers (Ay) of Zr(p⃗,p) at 200 and 300 MeV and of Ni(p⃗,p) at 200 MeV. The red lines denote the result of relativistic impulse approximation (RIA) with relativistic-Hartree (RH) densities. The Ni data was used to determine the effective interaction at 200 MeV (solid lines). Using the effective interaction, the proton and neutron densities of Zr were simultaneously searched and the results are denoted by the solid lines in Fig. 1 and 2. The

C via One-neutron Knockout Reaction of

T. Nishi , G.P.A. Berg, M. Dozono, H. Fujioka, N. Fukuda, T. Furuno, H. Geissel, R.S. Hayano, N. Inabe, K. Itahashi, S. Itoh, D. Kameda, T. Kubo, H. Matsubara, S. Michimasa , K. Miki, H. Miya , Y. Murakami, M. Nakamura, N. Nakatsuka, S. Noji, K. Okochi, S. Ota , H. Suzuki, K. Suzuki, M. Takaki , H. Takeda, Y.K. Tanaka, K. Todoroki, K. Tsukada, T. Uesaka, Y.N. Watanabe, H. Weick, H. Yamada, and K. Yoshida