九州大学-研究者情報 [市川雄一 (准教授) 理学研究院物理学部門]

1.	S. Go, Y. Tsuzuki, H. Yoneda, Y. Ichikawa, T. Ikeda, N. Imai, K. Imamura, M. Niikura, D. Nishimura, R. Mizuno, S. Takeda, H. Ueno, S. Watanabe, T. Y. Saito, S. Shimoura, S. Sugawara, A. Takamine, T. Takahashi, Demonstration of nuclear gamma-ray polarimetry based on a multi-layer CdTe Compton camera, Scientific Reports, https://doi.org/10.1038/s41598-024-52692-2, 14, 2573, 2024.02, [URL], 宇宙観測技術をベースとした多層半導体コンプトンカメラを用い、原子核から放出されるガンマ線の偏光を検出し、原子核の内部構造を明らかにできることを示した。多層半導体コンプトンカメラの光に対する高い位置決定精度と検出効率に着目し、この装置を用いて56Fe 原子核の励起状態から放出されるガンマ線の偏光測定を行った。その結果、偏光の測定を実証したばかりでなく、その測定の感度は非常に高く、高い検出効率を兼ね備えた革新的な手法であることが判明した。この成果は、希少な不安定核おける原子核の魔法数消失過程など、宇宙の成立や物質の性質の理解の基礎的知見を深めることに寄与すると期待される。.
2.	F. Boulay, G. S. Simpson, Y. Ichikawa, S. Kisyov, D. Bucurescu, A. Takamine, D. S. Ahn, K. Asahi, H. Baba, D. L. Balabanski, T. Egami, T. Fujita, N. Fukuda, C. Funayama, T. Furukawa, G. Georgiev, A. Gladkov, M. Hass, K. Imamura, N. Inabe, Y. Ishibashi, T. Kawaguchi, T. Kawamura, W. Kim, Y. Kobayashi, S. Kojima, A. Kusoglu, R. Lozeva, S. Momiyama, I. Mukul, M. Niikura, H. Nishibata, T. Nishizaka, A. Odahara, Y. Ohtomo, D. Ralet, T. Sato, Y. Shimizu, T. Sumikama, H. Suzuki, H. Takeda, L. C. Tao, Y. Togano, D. Tominaga, H. Ueno, H. Yamazaki, X. F. Yang, and J. M. Daugas, g-Factor of the ⁹⁹Zr (7/2⁺) Isomer: Monopole Evolution in Shape-Coexisting Region, Physical Review Letters, 10.1103/PhysRevLett.124.112501, 124, 112501, 2020.03, [URL], The gyromagnetic factor of the low-lying 251.96(9) keV isomeric state of the nucleus ⁹⁹Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of 7/2⁺, with a half-life of 336(5) ns. The isomer was produced and spin aligned via the abrasion-fission of a ²³⁸U primary beam at RIKEN RIBF. A magnetic moment 2.31(14) μ_N was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main d_5/2 composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution..
3.	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, [URL], 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..
4.	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, [URL], 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..
5.	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, [URL], 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..
6.	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, [URL], 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..
7.	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, [URL], 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..
8.	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, [URL], 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 1s_1/2 orbital..

主要総説, 論評, 解説, 書評, 報告書等

全てを見る→

1.	市川雄一, 核スピンから探る原子核・素粒子・宇宙, 2022.01.
2.	市川雄一, 低エネルギースピン物理 ―スピン核分光実験―, 2021.08.
3.	市川雄一, 変形しながら殻進化 ―磁気モーメントで探るエキゾチック核の「中身」―, 2019.10.
4.	市川雄一, スピン操作したRIビームの生成, 2014.09.
5.	市川雄一, 多種多様なRIビームのスピンを操る, 2013.12.
6.	市川雄一, 陽子過剰核の²⁴Siのベータ崩壊とその鏡映対称性, 2010.09.

主要学会発表等

全てを見る→

1.	Y. Ichikawa, Nuclear-moment measurements by gamma-ray spectroscopy, Workshop on frontier nuclear studies with gamma-ray spectrometer arrays (gamma24), 2024.03, [URL].
2.	市川雄一, 核反応によるスピン整列生成と核内スピン構造の探索, 原子核におけるスピン自由度の織り成すダイナミクス, 2024.12.
3.	Y. Ichikawa, Recent progress of nuclear moment measurement, RIBF Users Meeting 2022, 2022.09.
4.	Y. Ichikawa, Nuclear moment measurement: present and future, Physics of RI: Recent progress and perspectives, 2022.05.
5.	市川雄一, 核スピンから探る原子核・素粒子・宇宙, 原子核三者若手夏の学校, 2021.08.
6.	市川雄一, 低エネルギースピン物理, 日本のスピン物理学の展望, 2021.02, [URL].
7.	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, [URL].
8.	Y. Ichikawa, Nuclear-moment measurements of exotic nuclei using spin-oriented RI beams at RIBF, 14th Asia-Pacific Physics Conference 2019 (APPC2019), 2019.11.
9.	Y. Ichikawa, Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of ⁷⁵Cu, RIBF Nuclear Physics Seminar, 2019.02.
10.	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.
11.	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.
12.	Y. Ichikawa, Nuclear moment measurements using spin-aligned RI beam at RIBF, ANL Physics Division Seminar, 2017.11.
13.	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.
14.	Y. Ichikawa, Magnetic moment measurement using spin-aligned beam at RIBF, RIBF Users Meeting 2016, 2016.09.
15.	市川雄一, スピン操作したRIビームの生成, 日本物理学会第69回年次大会, 2014.03.
16.	Y. Ichikawa, Overview of RIBF and spin orientation in RI beam, The 14th International CNS Summer School (CNSSS15), 2015.08.
17.	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.
18.	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.
19.	市川雄一, スピン操作したRIビームの生成, 東北大学CYRICセミナー, 2013.01.
20.	Y. Ichikawa, Production of spin-controlled RI beams, RIBF Nuclear Physics Seminar, 2012.12.
21.	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.
22.	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.
23.	市川雄一, 陽子過剰核²⁴Siのベータ崩壊とその鏡映対称性, 日本物理学会2010年秋季大会, 2010.09.

その他の優れた研究業績

2020.03, 理化学研究所プレスリリース
「ジルコニウム同位体は励起状態でも突然変形する　－99Zr の励起状態の核磁気モーメント測定から明らかに－」
https://www.riken.jp/press/2020/20200317_2/index.html.

2019.01, 理化学研究所、東京大学プレスリリース
「磁気モーメントから分かる銅同位体の新たな姿　－極限までスピン整列度を高めたRI ビームを駆使して測定に成功－」
https://www.riken.jp/press/2019/20190130_2/.

2012.10, 理化学研究所、東京工業大学プレスリリース
「多種多様なRIビームのスピンを操作する新手法を開発　－2段階のRI 生成反応であらゆるRIビームに対してのスピン操作と大強度化を実現－」
https://www.riken.jp/press/2012/20121022/.

学会活動

所属学会名

日本物理学会

学会大会・会議・シンポジウム等における役割

2024.03.14～2024.03.15, The 15th International Workshop of Fundamental Physics Using Atoms (FPUA2024), Organizing committee, Local organizing committess.

2024.03.06～2024.03.07, 核談創立70周年記念シンポジウム〜原子核物理学の昨日・今日・明日～, 研究会組織委員.

2022.09.06～2022.09.07, RIBF Users Meeting 2023, Organizing committee, Chair.

2023.09.04～2023.09.05, 第12回　停止・低速不安定核ビームを用いた核分光研究会, 研究会組織委員.

2023.03.15～2023.03.17, 第4回若手放談会：エキゾチック核物理の将来, 研究会組織委員.

2023.11.28～2023.11.30, The International Workshop on Atomic Parity Violation (APV2022) , Organizing committee.

2022.11.24～2022.11.25, The 14th International Workshop of Fundamental Physics Using Atoms (FPUA2022), Organizing committee, Local organizing committess.

2022.09.20～2022.09.22, RIBF Users Meeting 2022, Organizing committee, Chair.

2021.10.18～2021.10.22, SPIN2021, Local Organizing Committee & Program Committee.

2021.02.23～2021.02.24, 日本のスピン物理学の展望, 研究会組織委員.

2020.02.19～2020.02.21, 第3回若手放談会：エキゾチック核物理の将来, 研究会組織委員.

2020.01.09～2020.01.10, The 12th International Workshop on Fundamental Physics Using Atoms (FPUA 2020), Local Organizing Committee.

2020.01.16～2020.01.17, 第11回　停止・低速不安定核ビームを用いた核分光研究会, 研究会組織委員.

2019.03.18～2019.03.19, 第10回　停止・低速不安定核ビームを用いた核分光研究会, 研究会組織委員.

2018.10.23～2018.10.27, Fifth Joint Meeting of the Nuclear Physics Divisions of the APS and the JPS (HAWAII2018), Organizing Committee of “Mini-symposium on Fundamental Symmetries (Many-body Sysmtems)”.

2018.01.08～2018.01.09, The 10th International Workshop on Fundamental Physics Using Atoms (FPUA 2018), Organizing Committee.

2017.12.04～2017.12.05, International symposium on RI beam physics in the 21st century: 10th anniversary of RIBF, Organizing Committee.

2017.03.05～2017.03.06, 第9回　停止・低速RIビームを用いた核分光研究会, 研究会組織委員.

2017.01.09～2017.01.10, The 9th International Workshop on Fundamental Physics Using Atoms (FPUA 2017), Organizing Committee.

2016.03.04～2016.03.04, 14th RIBF Discussion - Charge Radii studies through laser spectroscopy, Local Organizing Committee.

2016.03.03～2016.03.04, 第8回　停止・低速不安定核ビームを用いた核分光研究会, 研究会組織委員.

2015.12.06～2012.12.07, Physics with Fragment Separators - 25th Anniversary of RIKEN Projectile Fragment Separator (RIPS25), Scientific Secretary.

2015.11.30～2015.12.01, Fundamental Physics Using Atoms 2015 (FPUA2015) -Toward better understanding of our matter universe-, Local Organizing Committee.

2014.12.01～2014.12.05, The sixth international conference on Trapped Charged Particles and Fundamental Physics (TCP2014), Scientific Secretary.

2014.03.03～2014.03.04, 第7回　停止・低速不安定核ビームを用いた核分光研究会, 研究会組織委員.

受賞

第5回理研研究奨励賞, 理化学研究所, 2014.03.

第8回日本物理学会若手奨励賞, 日本物理学会, 2014.03.

第16回原子核談話会新人賞, 原子核談話会, 2010.09.

研究資金

科学研究費補助金の採択状況(文部科学省、日本学術振興会)

2024年度～2028年度, 基盤研究(A), 代表, 核スピンメーザーを⽤いた静的・動的電気双極⼦モーメントの探索.

2020年度～2022年度, 挑戦的研究（萌芽）, 代表, Xe原子EDM測定に向けた電極素材表面における131Xeスピン緩和機構の解明.

2020年度～2023年度, 基盤研究(B), 代表, スピン整列ビームを用いたエキゾチック核構造研究の展開.

2016年度～2019年度, 基盤研究(A), 分担, 重イオンを用いた新奇光子ビーム生成機構の検証実験.

2016年度～2019年度, 基盤研究(C), 代表, Cu同位体の励起状態核磁気モーメント測定による中性子過剰核の核構造研究.

2014年度～2016年度, 基盤研究(A), 分担, 能動核スピンメーザー法を用いた原子EDMと核シッフモーメントの研究.

2010年度～2013年度, 基盤研究(B), 連携, 中性子数２８近傍核の核電磁モーメント測定.

2009年度～2011年度, 若手研究(A,B), 代表, Mg同位体の励起状態の磁気モーメント測定による核構造研究.

学内資金・基金等への採択状況

2021年度～2021年度, わかばチャレンジ, 代表, 放射線検出による核スピン歳差運動の精密測定　-不安定核原子EDM測定にむけて-.

九大関連コンテンツ

pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。

QIR　九州大学学術情報リポジトリシステム情報科学研究院

理学部・理学研究院


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