How is the rapid neutron capture process terminated ? -Pioneering research with delayed fission spectroscopies-

• Project/Area Number: 18H03711
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 15:Particle-, nuclear-, astro-physics, and related fields
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: Miyatake Hiroari 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 教授 (50190799)
• Co-Investigator(Kenkyū-buntansha): 平山 賀一 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 研究機関講師 (30391733) ; SCHURY P.H 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 助教 (30462724) ; 渡邉 裕 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 准教授 (50353363)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥44,850,000 (Direct Cost: ¥34,500,000、Indirect Cost: ¥10,350,000); Fiscal Year 2020: ¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000); Fiscal Year 2019: ¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000); Fiscal Year 2018: ¥32,370,000 (Direct Cost: ¥24,900,000、Indirect Cost: ¥7,470,000)
• Keywords: 早い中性子捕獲過程 / 精密質量測定 / GAGG検出器 / 超微細構造測定 / 核分裂障壁測定 / 多核子移行反応 / レーザー共鳴イオン化 / 原子核質量測定 / 宇宙核物理 / 不安定原子核物理 / 核分裂 / 超重元素

Outline of Final Research Achievements

A pioneering work of the astrophysical heavy-element synthesis has been performed. It aims to study fission phenomena of synthesized isotopes in the rapid neutron capture process at explosive environments. Such isotopes can be produced through the multi-nucleon transfer reactions of uranium-beam and actinides target. And they are separated and collected with using KEK Isotope Separation System (KISS). Measurements of fission barriers and fission-fragment distributions of their beta-delayed fission phenomena will make clear the termination condition of the r-process.
New beta-ray detection system with high collection efficiency and high energy resolution has been developed in this work. And Multi-Reflection Time-of-Flight mass spectrograph (MRTOF) has been newly installed at the KISS facility. Measurements of fissions from unknown neutron-rich very heavy isotopes will be launched after the permission for use of curium target in the laboratory.

Academic Significance and Societal Importance of the Research Achievements

金・白金・ウランなどの重元素の起源は、超新星爆発や中性子合体などの爆発的天体環境における早い中性子捕獲(r-)過程だと考えられているが、定量的理解は出来てない。そこでr-過程終端部での重元素生成を調べるため、極めて重い中性子過剰核を人工的に生成し、β遅発核分裂を測定を目指して開拓的研究を開始した。これまでの研究・開発の蓄積をもとにした、世界に先駆けた研究である。
具体的には核分裂を詳細に調べるための高性能検出器の開発、未知重元素同位体の精密質量測定を行うシステムの設置を行った。今後の実験によって、中性子星合体で予測されている核分裂起源の重元素生成に定量的な判断が下せるようになるだろう。

Research Products

• [Int'l Joint Research] Institute for Basic Science/Seoul National University(韓国)
• [Int'l Joint Research] Beihan University/Institute of Modern Physics(中国)
• [Int'l Joint Research] Surrey University/Brighton University(英国)
• [Int'l Joint Research] Argonne Nat. Lab.(米国)
• [Int'l Joint Research] GSI(ドイツ)
• [Int'l Joint Research]
• [Int'l Joint Research] Institute for Basic Science/Seoul National University(韓国)
• [Int'l Joint Research] Beihan University/Institute of Modern Physics(中国)
• [Int'l Joint Research] Surrey University/Brighton University(英国)
• [Int'l Joint Research] Argonne Nat. Lab.(米国)
• [Int'l Joint Research] GSI(ドイツ)
• [Int'l Joint Research]
• [Int'l Joint Research] Institute for Basic Science(韓国)
• [Int'l Joint Research] TRIUMF(カナダ)
• [Journal Article] Three-dimensional tracking multi-segmented proportional gas counter for β-decay spectroscopy of unstable nuclei (2021)
  • Author(s): Hirayama Y.、Schury P.、Mukai M.、Choi H.、Iimura S.、Watanabe Y.X.、Wada M.、Watanabe H.、Miyatake H.
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 997 Pages: 165152-165152
  • DOI: 10.1016/j.nima.2021.165152
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] KISS Project (2021)
  • Author(s): Miyatake, H.
  • Journal Title: AIP Conference Proceedings Volume: 2319 Pages: 080006-080006
  • DOI: 10.1063/5.0036990
  • Peer Reviewed
• [Journal Article] Nuclear spectroscopy of r-process nuclei using KEK Isotope Separation System (2020)
  • Author(s): Hirayama Y.、Watanabe Y.X.、Mukai M.、Ahmed M.、Ishiyama H.、Jeong S.C.、Kakiguchi Y.、Kimura S.、Moon J.Y.、Oyaizu M.、Park J.H.、Schury P.、Wada M.、Miyatake H.
  • Journal Title: Journal of Physics: Conference Series Volume: 1643 Issue: 1 Pages: 012138-012138
  • DOI: 10.1088/1742-6596/1643/1/012138
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Properties of Ta187 Revealed through Isomeric Decay (2020)
  • Author(s): Walker P.M.、Hirayama Y.、Lane G.J.、Watanabe H.、Dracoulis G.D.、Ahmed M.、Brunet M.、Hashimoto T.、Ishizawa S.、Kondev F.G.、Litvinov Yu.A.、Miyatake H.、Moon J.Y.、Mukai M.、Niwase T.、Park J.H.、Podolyk Zs.、Rosenbusch M.、Schury P.、Wada M.、Watanabe X.Y.、Liang W.Y.、Xu F.R.
  • Journal Title: Physical Review Letters Volume: 125 Issue: 19 Pages: 192505-192505
  • DOI: 10.1103/physrevlett.125.192505
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] In-gas-cell laser ionization spectroscopy of Os194,196 isotopes by using a multireflection time-of-flight mass spectrograph (2020)
  • Author(s): Choi H.、Hirayama Y.、Choi S.、Hashimoto T.、Jeong S. C.、Miyatake H.、Moon J. Y.、Mukai M.、Niwase T.、Oyaizu M.、Rosenbusch M.、Schury P.、Taniguchi A.、Watanabe Y. X.、Wada M.
  • Journal Title: Physical Review C Volume: 102 Issue: 3 Pages: 034309-034309
  • DOI: 10.1103/physrevc.102.034309
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Deexcitation γ-ray transitions from the long-lived Iπ=13/2+ metastable state in Os195 (2020)
  • Author(s): Watanabe Y. X.、Ahmed M.、Hirayama Y.、Mukai M.、Park J. H.、Schury P.、Kakiguchi Y.、Kimura S.、Ozawa A.、Oyaizu M.、Wada M.、Miyatake H.
  • Journal Title: Physical Review C Volume: 101 Issue: 4 Pages: 041305-041305
  • DOI: 10.1103/physrevc.101.041305
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Nuclear spectroscopy of r-process nuclei using KEK Isotope Separation System (2020)
  • Author(s): Y. Hirayama, Y.X. Watanabe, M. Mukai, P. Schury, M. Ahmed, H. Ishiyama, S.C. Jeong, Y. Kakiguchi, S. Kimura, J.Y. Moon, M. Oyaizu, J.H. Park, M. Wada, H. Miyatake
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume: 463 Pages: 425-430
  • DOI: 10.1016/j.nimb.2019.04.035
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Development of a multi-segmented proportional gas counter for β-decay spectroscopy at KISS (2020)
  • Author(s): M. Mukai, Y. Hirayama, P. Schury, Y.X. Watanabe, M. Ahmed, H. Haba, H. Ishiyama, S.C. Jeong , Y. Kakiguchi, S. Kimura, J.Y. Moon, M. Oyaizu, A. Ozawa, J.H. Park, H. Ueno, M. Wada, H. Miyatake
  • Journal Title: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms Volume: 463 Pages: 421-424
  • DOI: 10.1016/j.nimb.2019.04.036
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Efficient two-color two-step laser ionization schemes of λ1 ~250 nm and λ2 = 307.9 nm for heavy refractory elements-Measurements of ionization cross-sections and hyperfine spectra of tantalum and tungsten (2019)
  • Author(s): Y. Hirayama, M. Mukai, Y. X. Watanabe, M. Oyaizu, S. C. Jeong, Y. Kakiguchi, P. Schury, M. Wada, and H. Miyatake
  • Journal Title: Review of Scientific Instruments Volume: 90 Issue: 11 Pages: 115104-115104
  • DOI: 10.1063/1.5124444
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Time-of-flight mass spectrographs of high mass resolving power (2019)
  • Author(s): Wollnik H.、Wada M.、Schury P.、Rosenbusch M.、Ito Y.、Miyatake H.
  • Journal Title: International Journal of Modern Physics A Volume: 34 Issue: 36 Pages: 1942001-1942001
  • DOI: 10.1142/s0217751x19420016
• [Journal Article] KEK Isotope Separation System (KISS) (2018)
  • Author(s): Y. Watanabe, Y. Hirayama, H. Miyatake
  • Journal Title: Nuclear Physics News Volume: 28 Issue: 4 Pages: 25-28
  • DOI: 10.1080/10619127.2018.1529984
  • Peer Reviewed / Open Access
• [Presentation] 非軸対称変形核192Reの基底状態からのベータ崩壊 (2020)
  • Author(s): 渡邉 寛
  • Organizer: 日本物理学会 ２０２０年度 秋季大会
• [Presentation] MRTOF+α-TOFを用いた短寿命α崩壊核種の質量-崩壊特性測定 (2020)
  • Author(s): 庭瀬暁隆
  • Organizer: 日本物理学会 ２０２０年度 第７５回年次大会
• [Presentation] Study of nuclear structure in the vicinity of N=126 at KISS (2020)
  • Author(s): Yoshikazu Hirayama
  • Organizer: Vth Topical Workshop on Modern Aspects in Nuclear Structure
  • Invited
• [Presentation] KISSでの核分光研究 (2020)
  • Author(s): 宮武宇也
  • Organizer: 令和元年度KUR専門研究会「短寿命RIを用いた核分光と核物性研究Ⅵ」 兼「第11回停止・低速RIビームを用いた核分光研究会」
• [Presentation] Towards precise mass measurements of Nh and Mc isotopes (2019)
  • Author(s): Michiharu Wada
  • Organizer: 4th International Symposium on Superheavy Elements
  • Int'l Joint Research / Invited
• [Presentation] KISS Projewct (2019)
  • Author(s): Hiroari Miyatake
  • Organizer: 14th Asia-Pacific Physics Conference
  • Int'l Joint Research / Invited
• [Presentation] 第7周期元素科学：超重元素の物理と化学 (2019)
  • Author(s): 宮武宇也
  • Organizer: 日本物理学会2019年秋季大会 合同シンポジウム
  • Invited
• [Presentation] Nuclear physics by multi-reflection time-of-flight mass spectrograph at WNSC (2019)
  • Author(s): Peter Schury
  • Organizer: INPC 2019
  • Int'l Joint Research
• [Presentation] Nuclear spectroscopy of r-process nuclei in the vicinity of N=126 by using KISS (2019)
  • Author(s): Toshikazu Hirayama
  • Organizer: INPC2019
  • Int'l Joint Research
• [Presentation] Recent experimental results of KEK Isotope Separation System (KISS) (2019)
  • Author(s): Yutaka Watanabe
  • Organizer: The 13th International Conference on Stopping and Manipulation of Ions and related topics SMI-2019
  • Int'l Joint Research / Invited
• [Presentation] Present progress of researches with KISS and MRTOF (2019)
  • Author(s): Hiroari Miyatake
  • Organizer: OMEG 15
  • Int'l Joint Research / Invited
• [Presentation] Towards comprehensive mass measurements with MRTOF mass spectrographs at RIKEN RIBF (2019)
  • Author(s): Michiharu Wada
  • Organizer: 2019 KPS Spring Meeting
  • Invited
• [Presentation] Production of N=126 nuclei and beyond using multinucleon transfer reactions (2019)
  • Author(s): Yutaka Watanabe
  • Organizer: Physics between lead and uranium: in preparation of new experimental campaigns at ISOLDE
  • Invited
• [Presentation] Nuclear spectroscopy of r-process nuclei in the vicinity of N=126 at KISS (2019)
  • Author(s): Yoshikazu Hirayama
  • Organizer: Physics between lead and uranium: in preparation of new experimental campaigns at ISOLDE
  • Invited
• [Presentation] Production of N=126 nuclei and beyond using multinucleon transfer reactions Yutaka Watanabe (2019)
  • Author(s): Y. Watanabe
  • Organizer: Physics between lead and uranium: in preparation of new experimental campaigns at ISOLDE
  • Int'l Joint Research
• [Presentation] Nuclear spectroscopy of r-process nuclei in the vicinity of N=126 at KISS Yoshikazu Hirayama (2019)
  • Author(s): Y. Hirayama
  • Organizer: Physics between lead and uranium: in preparation of new experimental campaigns at ISOLDE
  • Int'l Joint Research
• [Presentation] Nuclear spectroscopy of r-process nuclei in the vicinity of N = 126 at KISS (2019)
  • Author(s): 平山賀一
  • Organizer: 日本物理学会第７４回年次大会シンポジウム
  • Invited
• [Presentation] 宇宙核物理に関連する質量測定 (2019)
  • Author(s): 和田道治
  • Organizer: 核データと重元素合成を中心とする宇宙核物理研究会
  • Invited
• [Presentation] KISS/MRTOFの現状 (2018)
  • Author(s): 宮武宇也
  • Organizer: 平成30年度KUR専門研究会「短寿命RIを用いた核分光と核物性研究Ⅴ」
• [Presentation] MRTOF Mass Spectrographs at RIKEN RIBF ---Toward Comprehensive Mass Measurements of >1000 Nuclides Including Super Heavy Nuclides (2018)
  • Author(s): M. Wada
  • Organizer: 13th International Conference on Nucleus-Nucleus Collisions (NN2018)
  • Int'l Joint Research / Invited
• [Presentation] KISS and MRTOF Projects of KEK (2018)
  • Author(s): P. Schury
  • Organizer: The 10th China-Japan Joint Nuclear Physics Symposium (CJNP 2018)
  • Int'l Joint Research / Invited
• [Presentation] Mass Measurements of Heavy and Superheavy Nuclei by Multi-Reflection Time-of-Flight Mass Spectrograph (2018)
  • Author(s): P. Schury
  • Organizer: 7th International Conference on Trapped Charged Particles and Fundamental Physics (TCP2018)
  • Int'l Joint Research
• [Presentation] RNB project on the astrophysical element synthesis (2018)
  • Author(s): H. Miyatake
  • Organizer: Tsukuba Global Science Week 2018 (TGSW2018)
  • Int'l Joint Research / Invited
• [Presentation] Nuclear production by multinucleon transfer reactions (2018)
  • Author(s): Y. Watanabe
  • Organizer: 20th Northeastern Asian Symposium on “Nuclear Physics in the 21st Century”
  • Int'l Joint Research / Invited
• [Presentation] Nuclear spectroscopy of r-process nuclei using KEK Isotope Separation System (2018)
  • Author(s): Y. Hirayama
  • Organizer: XVIII The International Conference on Electromagnetic Isotope Separators and Related Topics (EMIS2018)
  • Int'l Joint Research
• [Presentation] r-過程終焉部、核分裂障壁 (2018)
  • Author(s): 宮武宇也
  • Organizer: 「超重元素研究の新展開」研究会
  • Invited
• [Remarks] 高エネルギー加速器研究機構素粒子原子核研究所和光原子核科学センター
  • URL: https://research.kek.jp/group/wnsc/
• [Remarks]
  • URL: http://research.kek.jp/group/wnsc/
• [Remarks] KEK Wako Nuclear Science Center
  • URL: http://research.kek.jp/group/wnsc/