Kyushu University Academic Staff Educational and Research Activities Database
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Yuichi Ichikawa Last modified date:2023.06.19

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Academic Degree
Country of degree conferring institution (Overseas)
Field of Specialization
Experimental Nuclear Physics
ORCID(Open Researcher and Contributor ID)
Total Priod of education and research career in the foreign country
Research Interests
  • Study of exotic nuclear properties using nuclear-spin-oriented RI beams
    keyword : Spin, RI beam
  • Study of fundamental symmetries using nuclear-spin manipulation
    keyword : Spin, Symmetry
Academic Activities
1. Y. Ichikawa, H. Nishibata, Y. Tsunoda, A. Takamine, K. Imamura, T. Fujita, T. Sato, S. Momiyama, Y. Shimizu, D. S. Ahn, K. Asahi, H. Baba, D. L. Balabanski, F. Boulay, J. M. Daugas, T. Egami, N. Fukuda, C. Funayama, T. Furukawa, G. Georgiev, A. Gladkov, N. Inabe, Y. Ishibashi, T. Kawaguchi, T. Kawamura, Y. Kobayashi, S. Kojima, A. Kusoglu, I. Mukul, M. Niikura, T. Nishizaka, A. Odahara, Y. Ohtomo, T. Otsuka, D. Ralet, G. S. Simpson, T. Sumikama, H. Suzuki, H. Takeda, L. C. Tao, Y. Togano, D. Tominaga, H. Ueno, H. Yamazaki, X. F. Yang, Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu, Nature Physics, 10.1038/s41567-018-0410-7, 15, 4, 321-325, 2019.04, Exotic nuclei are characterized by having a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus may vary due to nuclear force and excess neutrons, in a phenomenon called shell evolution. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieve large spin alignment via a two-step reaction scheme that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes..
2. T. Sato, Y. Ichikawa, S. Kojima, C. Funayama, S. Tanaka, T. Inoue, A. Uchiyama, A. Gladkov, A. Takamine, Y. Sakamoto, Y. Ohtomo, C. Hirao, M. Chikamori, E. Hikota, T. Suzuki, M. Tsuchiya, T. Furukawa, A. Yoshimi, C. P. Bidinosti, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, N. Yoshinaga, Y. Sakemi, K. Asahi, Development of co-located 129Xe and 131Xe nuclear spin masers with external feedback scheme, Physics Letters, Section A: General, Atomic and Solid State Physics, 10.1016/j.physleta.2017.12.003, 382, 8, 588-594, 2018.02, We report on the operation of co-located 129Xe and 131Xe nuclear spin masers with an external feedback scheme, and discuss the use of 131Xe as a comagnetometer in measurements of the 129Xe spin precession frequency. By applying a correction based on the observed change in the 131Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 μHz is obtained for a 104 s averaging time, suggesting the possibility of future improvement to ≈ 1 nHz by improving the signal-to-noise ratio of the observation..
3. K. Asahi, Y. Ichikawa, M. Chikamori, Y. Ohtomo, E. Hikota, T. Suzuki, T. Inoue, T. Furukawa, A. Yoshimi, K. Suzuki, T. Nanao, H. Miyatake, M. Tsuchiya, N. Yoshida, H. Shirai, T. Ino, H. Ueno, Y. Matsuo, T. Fukuyama, Search for electric dipole moment in 129Xe atom using a nuclear spin oscillator, Physics of Particles and Nuclei, 10.1134/S1063779614010080, 45, 1, 199-201, 2014.01, We aim to measure the electric dipole moment (EDM) of a diamagnetic atom 129Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented..
4. Yuichi Ichikawa, Hideki Ueno, Yuji Ishii, Takeshi Furukawa, Akihiro Yoshimi, Daisuke Kameda, Hiroshi Watanabe, Nori Aoi, Koichiro Asahi, Dimiter L. Balabanski, Raphaël Chevrier, Jean Michel Daugas, Naoki Fukuda, Georgi Georgiev, Hironori Hayashi, Hiroaki Iijima, Naoto Inabe, Takeshi Inoue, Masayasu Ishihara, Toshiyuki Kubo, Tsubasa Nanao, Tetsuya Ohnishi, Kunifumi Suzuki, Masato Tsuchiya, Hiroyuki Takeda, Mustafa M. Rajabali, Production of spin-controlled rare isotope beams, Nature Physics, 10.1038/nphys2457, 8, 12, 918-922, 2012.12, The degree of freedom of spin in quantum systems serves as an unparalleled laboratory where intriguing quantum physical properties can be observed, and the ability to control spin is a powerful tool in physics research. We propose a method for controlling spin in a system of rare isotopes which takes advantage of the mechanism of the projectile fragmentation reaction combined with the momentum-dispersion matching technique. The present method was verified in an experiment at the RIKEN RI Beam Factory, in which a degree of alignment of 8% was achieved for the spin of a rare isotope 32Al. The figure of merit for the present method was found to be greater than that of the conventional method by a factor of more than 50..
5. Balabanski D.L., Ishii Y., Ishihara M., Inoue T., Inabe N., Iijima H., Hayashi H., Georgiev G., Furukawa T., Fukuda N., Asahi K., Aoi N., Cottenier S., Haas H., Hass M., Ueno H., Ichikawa Y., Gaudefroy L., Daugas J.M., Chevrier R., Yoshimi A., Watanabe H., Vermeulen N., Tsuchiya M., Takeda H., Suzuki K., Rajabali M.M., Ohnishi T., Neyens G., Nanao T., Kubo T., Kameda D., Is the 7/2^_ isomer state of ^S spherical?, Physical Review Letters, 10.1103/PhysRevLett.108.162501, 108, 16, 162501-162501, 2012.04, We report on the spectroscopic quadrupole moment measurement of the 7/2^_ isomeric state in ^_S_ [E^∗ =320.5(5)  keV , T_=415(3)  ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, ∣Q_s∣=23(3)  efm^2 , is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured ∣Q_s∣, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape..
6. Y. Ichikawa, T. K. Onishi, D. Suzuki, H. Iwasaki, T. Kubo, V. Naik, A. Chakrabarti, N. Aoi, B. A. Brown, N. Fukuda, S. Kubono, T. Motobayashi, T. Nakabayashi, T. Nakamura, T. Nakao, T. Okumura, H. J. Ong, H. Suzuki, M. K. Suzuki, T. Teranishi, K. N. Yamada, H. Yamaguchi, H. Sakurai, β Decay of the proton-rich nucleus 24Si and its mirror asymmetry, Physical Review C - Nuclear Physics, 10.1103/PhysRevC.80.044302, 80, 4, 2009.10, β-decay spectroscopy of the proton-rich nucleus 24Si was performed. The decay scheme was reconstructed from results of delayed γ-ray and proton measurements. We observed two β branches to bound states in 24Al for the first time. The branching ratios were determined to be 31(4)% and 23.9(15)% for the 11+ state at 0.426 MeV and the state at 1.090 MeV, respectively. The observation of an allowed transition to the 1.090-MeV state enabled us to firmly determine its spin-parity as 1+. In the proton measurements performed with the ΔE-E method, we observed a new unbound level at 6.735 MeV. The branching ratios to three unbound states, including the new level, were also determined for the first time. Based on the decay scheme, the B(GT) values of 24Si were deduced. The B(GT) values were smaller than those of the mirror nucleus 24Ne by 22% and 10% for the 11+ and 12+ states, respectively. The mirror asymmetries of B(GT), observed in both the 11+ and the 12+ states, indicate changes in configuration in the wave function associated with the Thomas-Ehrman shift. To clarify the mechanism of this asymmetry, a comparison with shell-model calculations is also discussed. The calculations attribute the changes in configuration to the lowering of the 1s1/2 orbital..
1. Y. Ichikawa, Recent progress of nuclear moment measurement, RIBF Users Meeting 2022, 2022.09.
2. Y. Ichikawa, Nuclear moment measurement: present and future, Physics of RI: Recent progress and perspectives, 2022.05.
3. Y. Ichikawa, Nuclear moment studies using spin-oriented RI beams, REIMEI Workshop on Universal Features of Quantum Flows with Spin, Orbital and Tensor Correlations, 2020.02.
4. Y. Ichikawa, Nuclear-moment measurements of exotic nuclei using spin-oriented RI beams at RIBF, 14th Asia-Pacific Physics Conference 2019 (APPC2019), 2019.11.
5. Y. Ichikawa, Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu, RIBF Nuclear Physics Seminar, 2019.02.
6. Y. Ichikawa, Nuclear magnetic dipole moments measured with spin-oriented RI beams at RIKEN RIBF, The International Conference on HYPERFINE Interactions and Applications (HYPERFINE 2019), 2019.02.
7. Y. Ichikawa, Nuclear moment measurement using spin-oriented RI beam at RIBF, International Symposium on RI Beam Physics in the 21st Century: 10th Anniversary of RIBF, 2017.12.
8. Y. Ichikawa, Nuclear moment measurements using spin-aligned RI beam at RIBF, ANL Physics Division Seminar, 2017.11.
9. Y. Ichikawa, Magnetic moment measurement of isomeric state of 75Cu using spin-aligned RI beam at RIBF, Advances in Radioactive Isotope Sceinces (ARIS) 2017, 2017.05.
10. Y. Ichikawa, Magnetic moment measurement using spin-aligned beam at RIBF, RIBF Users Meeting 2016, 2016.09.
11. Y. Ichikawa, Search for electric dipole moment of 129Xe using active nuclear spin maser, 7th International Workshop on Fundamental Physics Using Atoms (FPUA 2014), 2014.03.
12. Y. Ichikawa, Experimental search for atomic EDM in 129Xe at Tokyo Tech., An ICTS Program on CP Violation in Elementary Particles and Composite Systems, 2013.02.
13. Y. Ichikawa, Production of spin-controlled RI beams, RIBF Nuclear Physics Seminar, 2012.12.
14. Y. Ichikawa, Experimental study of EDM in 129Xe atom using nuclear-spin maser, 6th International Workshop on Fundamental Physics using Atoms (FPUA 2012), 2012.09.
15. Y. Ichikawa, Spin manipulation of RI beams from two-stage projectile fragmentation reaction, Advanced Studies Institute on Symmetries and Spin (Spin-Praha-2012), 2012.07.