Papers by Susumu Shimoura
Bulletin of the American Physical Society, 2018
S. Masuoka,∗1 S. Shimoura,∗1 M. Takaki,∗1 S. Ota,∗1 S. Michimasa,∗1 M. Dozono,∗1 C. Iwamoto,∗1 K.... more S. Masuoka,∗1 S. Shimoura,∗1 M. Takaki,∗1 S. Ota,∗1 S. Michimasa,∗1 M. Dozono,∗1 C. Iwamoto,∗1 K. Kawata,∗1 N. Kitamura,∗1 M. Kobayashi,∗1 R. Nakajima,∗1 H. Tokieda,∗1 R. Yokoyama,∗1 D. S. Ahn,∗2 H. Baba,∗2 N. Fukuda,∗2 T. Harada,∗3 E. Ideguchi,∗4 N. Imai,∗1 N. Inabe,∗2 Y. Kondo,∗5 T. Kubo,∗2 Y. Maeda,∗6 F. M. Marqués,∗7 M. Matsushita,∗1 T. Nakamura,∗5 N. Orr,∗7 H. Sakai,∗2 H. Sato,∗2 P. Schrock,∗1 L. Stuhl,∗1,∗2 T. Sumikama,∗2 H. Suzuki,∗2 H. Takeda,∗2 K. Taniue,∗6 T. Uesaka,∗2 K. Wimmer,∗8 K. Yako,∗1 Y. Yamaguchi,∗1 Y. Yanagisawa,∗2 K. Yoshida,∗2 and J. Zenihiro∗2
25TH INTERNATIONAL CONFERENCE ON THE APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY, 2019
During operations of the Hyper-ECR ion source at the Center for Nuclear Study, University of Toky... more During operations of the Hyper-ECR ion source at the Center for Nuclear Study, University of Tokyo, an observation of plasma light intensities by a monochromator was made. Various gaseous and metal ions are produced, then extracted, and injected into RIKEN AVF cyclotron by the Hyper-ECR ion source. In this study, we developed the method of determining the crucible position, the magnetic strength distribution, and the RF power necessary for the plasma production. In summary, this study proves the importance of plasma spectroscopy for ion source operation.
Physical Review Letters, 2018
The key parameter to discuss the possibility of the pion condensation in nuclear matter, i.e. the... more The key parameter to discuss the possibility of the pion condensation in nuclear matter, i.e. the so-called Landau-Migdal parameter g ′ , was extracted by measuring the double-differential cross sections for the (p, n) reaction at 216 MeV/u on a neutron-rich doubly magic unstable nucleus, 132 Sn with the quality comparable to data taken with stable nuclei. The extracted strengths for Gamow-Teller transitions from 132 Sn leading to 132 Sb exhibit the GT giant resonance (GTR) at the excitation energy of 16.3 ± 0.4(stat.) ± 0.4(syst.) MeV with the width of Γ = 4.7 ± 0.8 MeV. The integrated GT strength up to Ex = 25 MeV is S − GT = 53 ± 5(stat.) +11 −10 (syst.), corresponding to 56% of Ikeda's sum rule of 3(N − Z) = 96. The present result accurately constrains the Landau-Migdal parameter as g ′ = 0.68±0.07, thanks to the high sensitivity of the GTR energy to g ′. In combination with previous studies on the GTR for 90 Zr and 208 Pb, the result of this work shows the constancy of this parameter in the nuclear chart region with (N − Z)/A = 0.11 to 0.24 and A = 90 to 208.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005
... Nomachi, Y. Ohashi, T. Ooba, H. Ohkuma, DS Oshuev, C. Rangacharyulu, A. Sakaguchi, T. Sasaki,... more ... Nomachi, Y. Ohashi, T. Ooba, H. Ohkuma, DS Oshuev, C. Rangacharyulu, A. Sakaguchi, T. Sasaki, PM Shagin, Y. Shiino, H. Shimizu, Y. Sugaya, M. Sumihama, H. Toyokawa, A. Wakai, CW Wang, SC Wang, K. Yonehara, T. Yorita, M. Yoshimura, M. Yosoi and RGT Zegers, Phys ...
Physical Review C, 2009
Low-lying excited states in the neutron-rich nucleus ^32Mg were studied by proton inelastic scatt... more Low-lying excited states in the neutron-rich nucleus ^32Mg were studied by proton inelastic scattering in inverse kinematics via an in-beam gamma-ray spectroscopy technique. Populated states were identified by measuring de-excitation gamma rays, in which five new states were found by gamma-gamma coincidence analyses. The differential cross sections were analyzed by using coupled-channel calculations to determine the transferred angular momenta and
Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014), 2015
An experiment measuring one-neutron knockout from 17 C on a hydrogen target and populating neutro... more An experiment measuring one-neutron knockout from 17 C on a hydrogen target and populating neutron unbound states in the residue revealed the first 2 − state in 16 C at 5.45(1) MeV. Comparison of its populating cross section and parallel momentum distribution with a Glauber model calculation confirmed the nature of the state as a ν0p 1/2-hole state. Additionally, two more states were found at ∼6.1 and 6.28(2) MeV. Their neutron decay property suggested the former to be 1 − (0 −) and the latter 2 − , in agreement with a recent claim from a weak-coupling model.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2011
A Gamow-Teller (GT) transition from the drip-line nucleus 14 Be to 14 B was studied via the (p, n... more A Gamow-Teller (GT) transition from the drip-line nucleus 14 Be to 14 B was studied via the (p, n) reaction in inverse kinematics using a secondary 14 Be beam at 69 MeV/nucleon. The invariant mass method is employed to reconstruct the energy spectrum. A peak is observed at an excitation energy of 1.27(2) MeV in 14 B, together with bumps at 2.08 and 4.06(5) MeV. The observed forward peaking of the state at 1.27 MeV and a good description for the differential cross section, obtained with a DWBA calculation provide support for the 1 + assignment to this state. By extrapolating the cross section to zero momentum transfer the GT-transition strength is deduced. The value is found to compare well with that reported in a β-delayed neutron emission study.
Physics Letters B, 2005
The 0 + g.s. → 2 + 1 excitation of the neutron-rich nucleus 28 Ne has been investigated via heavy... more The 0 + g.s. → 2 + 1 excitation of the neutron-rich nucleus 28 Ne has been investigated via heavy-ion inelastic scattering in reversed kinematics. The B(E2; 0 + g.s. → 2 + 1) value was determined to be 132(23) e 2 fm 4 , which is smaller than expected from the low excitation energy of the first 2 + 1 state. A comparison with theoretical predictions suggests that the suppressed collectivity in 28 Ne is characteristic of nuclei lying on the boundary of the 'island of inversion'.
Physics Letters B, 2001
The highly neutron-rich nucleus 34 Mg has been studied via Coulomb excitation using a radioactive... more The highly neutron-rich nucleus 34 Mg has been studied via Coulomb excitation using a radioactive 34 Mg beam at 44.9 MeV/nucleon with a Pb target. The B(E2; 0 + g.s. → 2 + 1) value for the previously proposed 2 + 1 state in 34 Mg was determined for the first time to be 631(126) e 2 fm 4. This value corresponds to the quadrupole deformation parameter β 2 of 0.58(6), implying an anomalously large deformation of 34 Mg.
Physical Review C, 2006
Inelastic proton scattering to the 2 + 1 state of neutron-rich 16 C is studied in inverse kinemat... more Inelastic proton scattering to the 2 + 1 state of neutron-rich 16 C is studied in inverse kinematics using a 33-MeV/nucleon beam. The deformation parameter β pp = 0.47(5) obtained is consistent with the global systematics of even-even nuclei, based on the homogeneous quantum liquid-drop model. This result contrasts that of a recent lifetime measurement for the 2 + 1 state in 16 C, where an anomalously reduced E2 transition strength is observed. A combination of these two results yields a large M n /M p ratio of about 7, indicating a dominant neutron contribution to the quadrupole collectivity.
Physical Review C, 2004
Breakup reactions of the one-neutron halo nucleus 11 Be on lead and carbon targets at about 70 Me... more Breakup reactions of the one-neutron halo nucleus 11 Be on lead and carbon targets at about 70 MeV/ nucleon have been investigated at RIKEN by measuring the momentum vectors of the incident 11 Be, outgoing 10 Be, and neutron in coincidence. The relative energy spectra as well as the angular distributions of the 10 Be+ n center of mass system (inelastic angular distributions) have been extracted both for Pb and C targets. For the breakup of 11 Be on Pb, the selection of forward-scattering angles, corresponding to large impact parameters, is found to be effective to extract almost purely the first-order E1 Coulomb breakup component and to exclude the nuclear contribution and higher-order Coulomb breakup components. This angle-selected energy spectrum is thus used to deduce the spectroscopic factor for the 10 Be͑0 + ͒ 2s 1/2 configuration in 11 Be which is found to be 0.72± 0.04 with a B͑E1͒ strength up to E x = 4 MeV of 1.05± 0.06 e 2 fm 2. The energy weighted E1 strength up to E x = 4 MeV explains 70% ± 10% of the cluster sum rule, consistent with the obtained spectroscopic factor. The non-energy-weighted sum rule within the same energy range is used to extract the root-mean-square distance of the halo neutron to be 5.77͑16͒ fm, consistent with previously known values. In the breakup with the carbon target, we have observed the excitations to the known unbound states in 11 Be at E x = 1.78 MeV and E x = 3.41 MeV. Angular distributions for these states show the diffraction pattern characteristic of L = 2 transitions, resulting in a J = ͑3/2,5/2͒ + assignment for these states. We finally find that even for the C target the E1 Coulomb direct breakup mechanism becomes dominant at very forward angles.
Physical Review C, 1985
Elastic and inelastic scattering of 12C+ 12C, especially excitations of the ground-rotational-ban... more Elastic and inelastic scattering of 12C+ 12C, especially excitations of the ground-rotational-band members in 12C, have been studied at 139.5 and 158.8 MeV. Although reasonable fits to the angular distributions for the band members were obtained with a shallow optical potential, rainbowlike gross bumps observed at large angles in the elastic scattering were not explained at all by coupled-channel calculations
Nuclear Physics A, 2008
... Large quadrupole deformation lengths of 1.12(16) fm and 1.36(14) fm were obtained for 60 Cr a... more ... Large quadrupole deformation lengths of 1.12(16) fm and 1.36(14) fm were obtained for 60 Cr and 62 Cr, respectively, which confirm the enhanced col-lectivity ... and Ti suggests that the contributions of both protons and neutrons are crucial for the large collectivity in Cr ...
Nuclear Physics A, 1984
Nonequilibrium light-particle emissions have been investigated in the reaction 93Nb+ 14N at 132, ... more Nonequilibrium light-particle emissions have been investigated in the reaction 93Nb+ 14N at 132, 159 and 208 MeV by measuring inclusive differential cross sections of p, d, t, 3He and a. The experimental data were analyzed in terms of three models: (i) an extended exciton model, (ii) a coalescence model, and (iii) a moving thermal source model. The angle-integrated energy spectra of the protons were well described by the extended exciton model in which projectile nucleons were assumed to be transferred to the target one by one, but those of composite particles were not. On the other hand, the composite particle spectra (except for c(at forward angles) were successfully described by the coalescence model using spectra consistent with those for the protons. Extracted coalescence radii P, were about 140 MeV/c for d and t, and about 220 MeV/c for c(. The light-particle spectra were also fitted by the moving-source model assuming isotropic emission from a source moving with approximately half of the beam velocity and with much higher temperature than that of the compound nucleus. Extracted temperatures followed the systematics of a recent compilation for the various reactions. A discussion of these analyses is given.
Hyperfine Interactions, 1987
A new on-line separator was constructed and used successfully for the study on short-lived isotop... more A new on-line separator was constructed and used successfully for the study on short-lived isotopes at the Bevalac at Lawrence Berkeley Laboratory. The isotopes were produced through projectile fragmentation processes of high energy heavy-ion reactions. Various isotopes were rigidity-separated by use of a beam line and, finally, the desired single isotope was range-analyzed to stop in a catcher. A large number of .a-emitting 21F nuclei were successfully collected and the nuclear lifetime was determined by detecting .a rays. \,-This report was done with support from the Department of Energy. Any conclusions or opinions expressed in this report represent solely those of the author(s) and not necessarily those of The Regents of the University of California, the Lawrence Berkeley Laboratory or the Department of Energy. Reference to a company or product name does not imply approval or recommendation of the product by the University of California or the U.S. Department of Energy to the exclusion of others that may be suitable.
The European Physical Journal A, 2009
In-beam γ-ray spectroscopy of high-spin states in 49-51 Ti was performed via the fusionevaporatio... more In-beam γ-ray spectroscopy of high-spin states in 49-51 Ti was performed via the fusionevaporation reaction using a radioactive beam. By excitation function and γ-γ coincidence analysis, yrast high-spin levels up to I = (21/2 −), (11 +), (17/2 −) in 49-51 Ti were determined. The levels were compared with full-pf-shell model calculation. The level structure indicates the persistency of the N = 28 shell gap at yrast states in 49-51 Ti.
The European Physical Journal A, 2006
In the first half of the paper, the nuclear astrophysics activities in Japan, especially in exper... more In the first half of the paper, the nuclear astrophysics activities in Japan, especially in experimental studies are briefly overviewed. A variety of beams have been developed and used for nuclear astrophysics experiments in Japan. The activities include the RI beam facilities at low energies by the in-flight method at the Center for Nuclear Study (CNS), University of Tokyo and by the ISOL-based method at the JAERI tandem facility, and the RI beam facility at intermediate energies at RIKEN. Other activities include a study of the 12 C(α, γ) 16 O reaction exclusively at the tandem accelerator at the Kyushu University, and studies at the neutron facility at Tokyo Institute of Technology and at the photon facility at AIST (Sanso-ken). Research opportunities in the future at RIBF, J-PARC, and SPRING8 are also discussed. A discussion on the research activities at CNS has been specifically extended in the latter half, including various possibilities in collaboration at the RI beam factory at RIKEN.
Physical Review Letters, 2016
A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the dou... more A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the doublecharge-exchange reaction 4 Heð 8 He; 8 BeÞ at 186 MeV=u. The energy of the state is 0.83 AE 0.65ðstatÞ AE 1.25ðsystÞ MeV above the threshold of four-neutron decay with a significance level of 4.9σ. Utilizing the large positive Q value of the ð 8 He; 8 BeÞ reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently.
Nuclear spectroscopy via direct reactions of RI beams is discussed focusing on characteristics of... more Nuclear spectroscopy via direct reactions of RI beams is discussed focusing on characteristics of charge-exchange reactions of RI beams. Recent experiments using the SHARAQ spectrometer at the RIBF are presented, where isovector spin monopole and spin-non-flip monopole responses are studied by charge exchange reaction of RI beams. Some experimental plans and perspectives are also presented.
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Papers by Susumu Shimoura