Daisuke Kameda

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...

Identification of New Isotopes 125 Pd and 126 Pd produced by In-flight Fission of 345 MeV/nucleon 238 U: First Results from the RIKEN RI Beam Factory

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out in the commissioning experiment of the next-generation in-flight radioactive isotope beam separator BigRIPS at the RI Beam Factory at the RIKEN Nishina Center. Two neutron-rich palladium isotopes 125 Pd and 126 Pd were observed for the first time, which demonstrates the great potential of the RIKEN RI beam factory.

Energy resolution of gas ionization chamber for high-energy heavy ions

The energy resolution is reported for high-energy heavy ions with energies of nearly 340 MeV/nucleon and was measured using a gas ionization chamber filled with a 90%Ar/10%CH4 gas mixture. We observed that the energy resolution is proportional to the inverse of the atomic number of incident ions and to the inverse-square-root of the gas thickness. These results are consistent with the Bethe–Bloch formula for the energy loss of charged particles and the Bohr expression for heavy ion energy straggling. In addition, the influence of high-energy δ-rays generated in the detector on the energy deposition is discussed.

Ground-state electric quadrupole moment of 31 Al

levels are lowered [3, 4] and theirB(E2) values are enhanced [5] sizably in these isotopes,and the possibility of deformation has been proposed.Theoretical analyses [6] discussed the importance of 2p-2h excitations from the sd shell to the upper pf shell,and concluded it plausible that an inversion of ampli-tudes between the sd normal and pf intruder configura-tions would lead to deformation of the ground states.The region of nuclei where such a phenomenon occurs iscalled the island of inversion. In elucidating the under-lying mechanism for the inversion, the measurements ofthe electromagnetic moments have played an importantrole. For example in a series of neutron-rich Na isotopes,it has been found that, once entering the island of in-version, the ground-state magnetic dipole moment µ andelectric quadrupole moment Q [7, 8] show clear devia-tions from the conventional shell-model predictions [9],indicating that µ and Q are sensitive to changes in thenuclear configuration [10]. Also in the recent study of Mgisotopes, anomalous ground-state properties have beenrevealed through the µ-moment measurements [11, 12].In the present work, the ground-state Q moment of

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) MeV as preliminary results. For the excited state at 2.74(3) MeV, 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

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To produce a radioactive-isotope (RI) beam with high spin alignment, we have developed a novel method, the two-step projectile-fragmentation (PF) method, that employs momentum-dispersion matching. An on-line experiment to produce 32A1 from 48Ca via 33A1 was performed at RIKEN RI Beam Factory. In the experiment, we succeeded in producing approximately 8% spin alignment in an RI beam of 32A1. In this paper, we focus on evaluating the magnitude of spin alignment realized in one-nucleon removal from 33A1.