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RIBF Users Group Thesis Awards

RIBF Users Group Thesis awards started from 2012. The awards honor the achievements of young scholars who earned his or her doctoral degree based on an RIBF experiment (using BigRIPS, GARIS, CRIB, RIPS, etc.), or a theoretical study related to physics at RIBF. The winner will be selected by the Thesis Award selection committee and be provided an opportunity to give a special presentation at the annual RIBF Users Meeting.

2018

We are pleased to announce that the RIBF Users Group Thesis Awards for 2018 will be presented to Dr. Takahiro Nishi (RIKEN) for his outstanding contributions to the physics research at RIBF. Dr. Nishi obtained his Ph.D. degree at the University of Tokyo in 2017.
Dr. Takahiro Nishi receives the award for his Ph.D. thesis "Precision spectroscopy of deeply bound pionic states in 121,116Sn” (University of Tokyo, 2017). His thesis describes the experimental study of precise spectroscopy of pionic nuclear bound states at BigRIPS. The results are directly related to chiral symmetry breaking in nuclear medium. He successfully observed the atomic 1s and 2p states of pionic-121, 116Sn, and determined precisely the “b1” parameter of the pion-nucleus optical potential. The thesis presents the first result of the “πAF” project and also describes his contributions to all the aspects of the project, a detailed design and tuning of the dispersion-matched ion optics for the Sn(d,3He) reaction. This was paramount in order to achieve the required spectral resolution. This experimental study is a milestone towards systematic study of deeply bound pionic states. Further measurements along the Sn isotope chain will reveal the nuclear density dependence of the chiral symmetry breaking.

RIBF Thesis Award 2018 Selection Committee Members
M. Asai, J. Gibelin, W. Horiuchi (Chair), T. Isobe, Y. Kanada-En’yo, T. Matsumoto, T. Nakamura, S. Ota, S. Sakaguchi, M. Wakasugi, Y. Watanabe, K. Wimmer, K. Yoshida, J. Zenihiro,

With best regards,
Kathrin Wimmer (Chair of RIBF Users Group Executive Committee)
Hideto En’yo (Director of Nishina Center for Accelerator-Based Science)

2017

We are pleased to announce that the RIBF Users Group Thesis Awards for 2017 will be presented to Dr. Kazuyuki Sekizawa (Faculty of Physics, Warsaw University of Technology) and Dr. Jin Wu (Argonne National Laboratory) for their outstanding contributions to physics at RIBF. Dr. Kazuyuki Sekizawa belonged to University of Tsukuba and JSPS as a DC2 Research Fellow, and received Ph.D. in 2015. Dr. Jin Wu belonged to Peking University and RIKEN as an International Program Associate, and received Ph.D. in 2016.
Dr. Kazuyuki Sekizawa receives the award for his Ph.D. thesis entitled “Multinucleon Transfer Reactions and Quasifission Processes in Time-Dependent Hartree-Fock Theory” (University of Tsukuba in 2015). The thesis presents the first extensive application of the time-dependent Hartree-Fock (TDHF) theory to the multi-nucleon transfer and quasifission processes in the low-energy heavy-ion reactions. With the particle-number-projection method, the transfer probabilities and the cross sections are investigated. This method can explain existing experimental data reasonably well. Since the method is size extendable and has no adjustable parameter, the developed framework can be applied to production reactions of unknown neutron-rich nuclei as well as superheavy elements.
Dr. Jin Wu receives the award for his Ph.D. thesis "beta-decay spectroscopy of Z=55∼67 neutron-rich nuclei" (Peking University in 2016). His thesis describes the experimental study of beta-decay half-lives of heavy mid-shell nuclei via beta-decay spectroscopy in combination of the germanium detector array EURICA and the double-sided silicon detector array WAS3ABi, aiming at understanding the production mechanism of the smaller and broader peak of rare-earth elements in the solar abundance. The beta-decay half-lives of 94 neutron-rich nuclei were measured precisely, and 57 of them are measured for the first time. Newly measured half-lives give a significant contribution to describe the solar abundance pattern of rare-earth elements, which makes a strong impact on the scenario of r-process nucleosynthesis. The thesis also discuss the large drop in the systematic trend of half-lives at N=97 and N=105.

With Best Regards,
Tadaaki Isobe (Chair of RIBF Users Group Executive Committee)
Hideto En'yo (Director of Nishina Center for Accelerator-Based Science)

2016

We are pleased to announce that the RIBF Users Group Thesis Awards for 2016 will be presented to Dr. Kosho Minomo (Research Center for Nuclear Physics, Osaka University) and Dr. Clementine Santamaria (National Superconducting Cyclotron Laboratory, Michigan State University) for their outstanding contributions to the physics at RIBF.
Dr. Kosho Minomo receives the award for his PhD thesis ``Determination of deformed and halo structure of unstable nuclei by fully microscopic theory'' (Kyushu University in 2013). In this thesis, Dr. Minomo constructed a new theoretical method to microscopically derive a nucleus-nucleus optical potential. With this method, the optical potential can be obtained using a fundamental interaction with no adjustable parameters, which is a significant advantage compared to other methods and essential to investigate reaction of exotic nuclei. Using this method, he successfully reproduced the reaction cross section for Ne isotopes and concluded that the observed large cross section of 31Ne comes from its halo structure with a deformed core. The reaction theory and physics of a deformed halo nucleus proposed in this thesis will have an impact in both theoretical and experimental studies. It will open the way for further developments of physics of general reaction phenomena with exotic nuclei.
Dr. Clementine Santamaria receives the award for her PhD thesis ``Quest for new nuclear magic numbers with MINOS'' (Universite Paris Sud XI in 2015). Her thesis work is 1) on the development of MINOS (MagIc Numbers Off Stability), a unique hydrogen target surrounded by a TPC to reconstruct the reaction vertex point, and 2) on the first in-beam gamma ray spectroscopy experiment using the MINOS + DALI2 setup. Dr. Santamaria played a key role in the development, construction, and implementation of MINOS, and in particular the on-line and off-line commissioning experiments. For example, the geometry and gas to be used in MINOS were determined based on her analysis and she developed the primary tracking algorithm for the TPC. The MINOS device has now become widely used at RIBF and has significantly expanded the capability of spectroscopic studies of exotic nuclei far from the stability.

With Best Regards,
Tadaaki Isobe (Chair of RIBF Users Group Executive Committee)
Hideto En'yo (Director of Nishina Center for Accelerator-Based Science)

2015

The RIBF Users Group executive committee (UEC) and the Director of RIKEN Nishina Center are proud to announce that the RIBF Users Group Thesis Awards for 2015 have been awarded to Dr. Zhengyu Xu (Department of Physics, the University of Hong Kong) for “Beta-decay spectroscopy on neutron-rich nuclei in a range of Z = 26~32” and to Dr. Yuta Ito (RIKE Nishina Center) for “A multi-reflection time-of-flight mass spectrograph for high-precision mass measurements of short-lived nuclei”. We would like to congratulate both winners for their outstanding work.
Dr. Xu receives the award for his PhD thesis "Beta-decay spectroscopy on neutron-rich nuclei in a range of Z = 26?32" (School of Science, University of Tokyo in 2014). His thesis describes on an experimental work studying β-decay properties of neutron-rich nuclei in the vicinity of 78Ni. He was a member of the EURICA collaboration and was actively involved in the initial commissioning as well as all subsequent stages of the experiment. He was in charge of developing the double-sided silicon active stoppers. He contributed the setup of the EURICA gamma-ray detector system, and conducted a test experiment of EURICA and decay-spectroscopy experiments at RIBF. He was in charge of analysis for data obtained for Ni-78 and its vicinity. From this work, half-lives of 38 neutron-rich nuclei were measured, including 72?74Fe, 76,77Co, 79,80Ni, 81,82Cu, 84Zn, 87Ga and 87,88Ge, of which the half-lives are measured for the first time. In addition, ten β-delayed neutron emission probabilities (Pn) were investigated, and the Pn values of 78Ni, 80,81Cu, 83,84Zn, and 85Ga are newly deduced. Based on the new results, information was obtained on shell evolution at Z = 28 and N = 50 and these new data are used to used to suggest 78Ni is a good doubly-magic nucleus 78Ni.
Dr. Ito receives the award for his PhD thesis "A multi-reflection time-of-flight mass spectrograph for high-precision mass measurements of short-lived nuclei" (Graduate School and Applied Science, University of Tsukuba in 2014). His thesis describes a novel online mass measurement method for radioactive nuclei, especially for short-lived ones. For a Multi-Reflection Time-Of-Flight mass spectrograph (MRTOF) experiments, he developed two interfaces between a gas catcher setup and the MRTOF. One is a tapered linear RF quadrupole structure trap that accumulates continuous ion beams from the gas catcher. The other is a flat-trap made of two printed circuit boards that bunches ions from the tapered trap before injecting to the MRTOF. This was a key improvement to make an online mass measurement of 8Li+ (T1/2 = 838 ms) successful. That was the first MRTOF mass measurement of radioactive ions produced in projectile fragmentation at RIPS. He has also developed a new data analysis method of a single reference method. The speed, precision, and accuracy of the first online measurement exemplify the potential for using this new type of mass spectrograph for precision measurements of short-lived nuclei. It will open a new era of precision mass measurements of short-lived nuclei, in particular of “difficult elements” which are not available at ISOL facilities and "superheavy elements".

2013

Dr. Nobuyuki Kobayashi (University of Tokyo)
Thesis title: "Spectroscopy of Neutron-Rich Nuclei via the Inclusive Breakup Reactions"
His thesis established a novel spectroscopic method by using inclusive Coulomb and nuclear breakup reactions. With this method, he has systematically studied the ground-state properties of isotopes ranging from carbon (Z=6) to sulfur (Z=14) located in the vicinity of the neutron drip line. The observed large cross sections provide evidence of neutron halo structures in 22C, 31Ne, and 37Mg. Among them, 31Ne is likely to be the first case of a p-wave halo which appears in its ground state due to changes in the shell structure. This mechanism is of particular impact in that it could affect the structure of wide region of nuclei at the limit of existence resulting in possible modification in the location of the neutron drip line.
Part of his work has been published in - "One- and two-neutron removal reactions from the most neutron-rich carbon isotopes", PRC86(2012)054604 - "Halo Structure of Island of Inversion Nucleus 31Ne", PRL103(2009)262501

Best regards,
Ken Yako, on behalf of Thesis Award Selection Committee

2012

Dr. Kenjiro Miki (RCNP)
The thesis entitled "Study of the isovector spin monopole resonance via the (t,3He) reactions at 300 MeV/u".
A part of this work was published as K. Mkiki et al., in Phys. Rev. Lett. 108, 262503 (2012).