多価イオンビームによる2光子稀崩壊の観測

• Project Area: Toward new frontiers : Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams
• Project/Area Number: 21H00161
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: Saitama University
• Principal Investigator: 山口 貴之 埼玉大学, 理工学研究科, 教授 (10375595)
• Project Period (FY): 2021-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2022: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000); Fiscal Year 2021: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
• Keywords: 蓄積リング / 多価イオン / ガンマ崩壊

Outline of Research at the Start

多価イオンビームは、原子核と電子の相互作用を研究する上でユニークな実験環境となる。本研究では、蓄積リングに貯蔵された多価イオンビームを利用し、中性原子状態では難しい、原子核の2光子稀崩壊の観測を行う。
実験はドイツGSI研究所の加速器施設で行う。加速した78Krビームを標的に照射し、完全イオン化した72Ge（第1励起状態0+）ビームを生成する。このビームを蓄積リングESRに入射し、貯蔵する。2光子崩壊は、ショットキー検出器による周回周期の変化によって非破壊的に観測する。
低エネルギー0+準位を精度よく決定することで、原子核の変形共存のメカニズムに迫る新しいツールになることが期待される。

Outline of Annual Research Achievements

原子核の励起状態は、基底状態と励起状態がともにスピンが0+の場合、角運動量保存のためガンマ線を放出できず、内部転換電子崩壊によって脱励起する。しかし完全なイオン化により軌道電子が存在しない場合、かつ励起エネルギーが電子陽電子対生成を起こす閾値より低い場合は、一見すると崩壊できない特異な状態になる。このとき量子力学の2次効果として、2光子同時放出現象が起こる。イオンビームを蓄積リングに貯蔵する実験環境では、競合する過程がなく明確にこの稀少な現象を観測できる。
実験はドイツの重イオン科学研究所GSI/FAIRにて行った。シンクロトロンで加速した78KrビームをBe標的に照射し、核反応で2次ビームを生成した。ビームエネルギーが核子あたり約400MeVなので、ビームは完全イオン化しており、長寿命励起状態(アイソマー：スピン0+)を含んでいる。このビームを蓄積リングESRに入射し、貯蔵した。ESRのビーム光学条件は等時性、すなわち周回周期が粒子の質量電荷比に比例する条件に調整した。そのため、周回周期の非破壊観測によって飛行中のガンマ崩壊（質量変化）を検出することができる。観測にはショットキー検出器を用いた。2021年に2度のビームタイムを消化し、2022-2023年度にデータ解析を行った。その結果は2023年度に投稿論文としてまとめサブミット済みである（現在審査中）。結果として、70Seの2光子崩壊は観測することができなかったが、72Geの2光子崩壊の観測に成功し、予想より寿命が約10倍速い驚きの結果を得た。この成果を受け、2024年度に他の核種で同様の実験が認められている。また国際会議にて成果発表を行った。

Research Progress Status

令和4年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和4年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] GSI/Max-Planck Institut(ドイツ)
• [Int'l Joint Research] CEA(フランス)
• [Int'l Joint Research] IMP(中国)
• [Int'l Joint Research] CEA Paris-Saclay(フランス)
• [Int'l Joint Research] GSI/Goethe Universitat(ドイツ)
• [Int'l Joint Research] University of Surrey/Univ. of Edinburgh(英国)
• [Int'l Joint Research] TRIUMF(カナダ)
• [Int'l Joint Research] Argonne National Laboratory(米国)
• [Int'l Joint Research]
• [Journal Article] Ground-state mass of 22Al and test of state-of-the-art ab initio calculations (2024)
  • Author(s): M.Z. Sun, Y. Yu, X.P. Wang, M. Wang, J.G. Li, Y.H. Zhang, K. Blaum, Z.Y. Chen, R.J. Chen, H.Y. Deng, et al.
  • Journal Title: Chin. Phys. C Volume: 48 Issue: 3 Pages: 034002-034002
  • DOI: 10.1088/1674-1137/ad1a0a
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Proton capture on stored radioactive 118Te ions (2023)
  • Author(s): S. F. Dellmann, J. Glorius, Y. A. Litvinov, R. Reifarth, K. Al-Khasawneh, M. Aliotta, L. Bott, B. Brueckner, C. Bruno, R. J. Chen, et al.
  • Journal Title: EPJ Web of Conferences Volume: 279 Pages: 11018-11018
  • DOI: 10.1051/epjconf/202327911018
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Precision experiments with heavy-ion storage rings (2023)
  • Author(s): Yu.A. Litvinov, J. Glorius, M. Steck, Th. Stoehlker. K. Blaum, C.C. Bruno, P.J. Woods, I. Dillmann, B. Jurado, W. Korten, X. Ma, Y. Zhang, R. Reifarth, P. Walker, T. Yamaguchi
  • Journal Title: Acta Phys. Pol. B suppl. Volume: 16 Issue: 4 Pages: 1-1
  • DOI: 10.5506/aphyspolbsupp.16.4-a25
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Storage, accumulation and deceleration of secondary beams for nuclear astrophysics (2023)
  • Author(s): J. Glorius, Yu. A. Litvinov, M. Aliotta, F. Amjad, B. Brueckner, C.G. Bruno, R. Chen, T. Davinson, S.F. Dellmann, T. Dickel, et al.
  • Journal Title: Nucl. Instrum. Methods Phys. Res. B Volume: 541 Pages: 190-193
  • DOI: 10.1016/j.nimb.2023.04.059
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Recent achievements at the Rare-RI Ring, a unique mass spectrometer at the RIBF/RIKEN (2023)
  • Author(s): S. Naimi, Y. Yamaguchi, T. Yamaguchi, A. Ozawa
  • Journal Title: Eur. Phys. J. A Volume: 59 Issue: 4
  • DOI: 10.1140/epja/s10050-023-01009-4
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Matter radius of the doubly-magic 56Ni measured in a storage ring (2023)
  • Author(s): M. von Schmid, T. Aumann, S. Bagchi, S. Boenig, M. Csatlos, I. Dillmann, C. Dimopoulou, P. Egelhof, V. Eremin, T. Furuno, et al.
  • Journal Title: Eur. Phys. J. A Volume: 59 Issue: 4 Pages: 83-83
  • DOI: 10.1140/epja/s10050-023-00967-z
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Bρ-defined isochronous mass spectrometry and mass measurements of 58Ni fragments (2023)
  • Author(s): M. Zhang, X. Zhou, M. Wang, Y. H. Zhang, Yu.A. Litvinov, H. S. Xu, R. J. Chen, H. Y. Deng, C. Y. Fu, W. W. Ge, et al.
  • Journal Title: Eur. Phys. J. A Volume: 59 Issue: 2
  • DOI: 10.1140/epja/s10050-023-00928-6
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Isochronous mass measurements of neutron-deficient nuclei from 112Sn projectile fragmentation (2023)
  • Author(s): Y. M. Xing, C. X. Yuan, M. Wang, Y. H. Zhang, X. H. Zhou, Yu. A. Litvinov, K. Blaum, H. S. Xu, T. Bao, R. J. Chen, et al.
  • Journal Title: Phys. Rev. C Volume: 107 Issue: 1
  • DOI: 10.1103/physrevc.107.014304
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Precision measurement of the transition energy gt versus magnetic rigidity for storage-ring isochronous mass spectrometry (2022)
  • Author(s): M. Zhang, Y.H. Zhang, M. Wang, X. Zhou, Y.J. Yuan, X.L. Yan, Y.M. Xing, C.Y. Fu, R.J. Chen, X. Xu, et al.
  • Journal Title: Nucl. Instrum. Methods Phys. Res. A Volume: 1027 Pages: 166329-166329
  • DOI: 10.1016/j.nima.2022.166329
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Bρ-defined isochronous mass spectrometry: An approach for high-precision mass measurements of short-lived nuclei (2022)
  • Author(s): M. Wang, M. Zhang, X. Zhou, Y. H. Zhang, Yu. A. Litvinov, H. S. Xu, R. J. Chen, H. Y. Deng, C. Y. Fu, W. W. Ge, et al.
  • Journal Title: Phys. Rev. C Volume: 106 Issue: 5
  • DOI: 10.1103/physrevc.106.l051301
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] First Application of Mass Measurements with the Rare-RI Ring Reveals the Solar r-Process Abundance Trend at A=22 and A=123 (2022)
  • Author(s): H. F. Li, S. Naimi et al.
  • Journal Title: Physical Review Letters Volume: 128 Issue: 15 Pages: 152701-1
  • DOI: 10.1103/physrevlett.128.152701
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Masses of exotic nuclei (2021)
  • Author(s): Yamaguchi T.、Koura H.、Litvinov Yu.A.、Wang M.
  • Journal Title: Progress in Particle and Nuclear Physics Volume: 120 Pages: 103882-103882
  • DOI: 10.1016/j.ppnp.2021.103882
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Status of the laser spectroscopy and merged-beam experiments at RICE (2021)
  • Author(s): Y. Nakano, R. Igosawa, S. Iida, S. Okada, M. Lindley, S. Menk, R. Nagaoka, T. Hashimoto, S. Yamada, T. Yamaguchi, S. Kuma, T. Azuma,
  • Journal Title: JPS Conf. Proc. Volume: 35 Pages: 11006-11006
  • DOI: 10.7566/jpscp.35.011006
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] First demonstration of mass measurements for exotic nuclei using Rare-RI Ring (2021)
  • Author(s): D. Nagae, S. Omika, Y. Abe, Y. Yamaguchi, F. Suzaki, K. Wakayama, N. Tadano, R. Igosawa, K. Inomata, H. Arakawa, et al.
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011014
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Performance of a Time-Of-Flight detector and demonstration of a novel position-sensitive detector for mass measurements with Rare-RI Ring (2021)
  • Author(s): S. Suzuki, A. Ozawa, T. Moriguchi, M. Amano, D. Kamioka, Y. Ichikawa, Y. Tajiri, K. Hiraishi, T. Matsumoto, D. Nagae, Y. Abe, S. Naimi, H. Li, T. Yamaguchi, S. Omika, Z. Ge, K. Wakayama, N. Tadano, H. Arakawa, K. Inomata, T. Kobayashi, A. Kitagawa, S. Sato,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011017
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Basic study on delta ray detection for the determination of in-ring revolution time (2021)
  • Author(s): K. Inomata, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, T. Fujii, D. Kamioka, A. Kitagawa, H. Li, T. Moriguchi, D. Nagae, S. Omika, A. Ozawa, S. Sato, S. Suzuki, T. Suzuki, K. Wakayama,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011020
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Beam test on a long scintillating fiber as a position sensor in a storage ring facility (2021)
  • Author(s): K. Inomata, T. Yamaguchi, H. Arakawa, A. Kitagawa, D. Nagae, K. Nishimuro, S. Omika, S. Sato, T. Suzuki, N. Tadano, K. Wakayama,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011021
  • Peer Reviewed / Open Access
• [Journal Article] Properties of a thin YAP(Ce) scintillation counter for heavy ions (2021)
  • Author(s): H. Arakawa, Y. Yamaguchi, Y. Abe, M. Amano, K. Inomata, D. Kamioka, A. Kitagawa, H. Li, T. Moriguchi, D. Nagae, S. Omika, A. Ozawa, S. Sato, S.Suzuki, T. Suzuki, K. Wakayama,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011022
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Development of mirror-type MCP detectors for mass measurements at the Rare-RI Ring (2021)
  • Author(s): Z. Ge, S. Naimi, D. Nagae, Y. Abe, S. Omika, T. Uesaka, F. Suzaki, H. Li, Y. Yamaguchi, M. Wakasugi, K. Wakayama, T. Yamaguchi, A. Ozawa, H. Arakawa, K. Inomata, T. Kobayashi, K. Nishimuro, S. Suzuki, T. Moriguchi, D. Kamioka, M. Mukai, M. Amano, A. Kitagawa, S. Sato, G. Lorusso, Y. Yano,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011023
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A simple readout method for a position-sensitive detector using plastic scintillator bars (2021)
  • Author(s): K. Wakayama, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, Z. Ge, K. Inomata, D. Kamioka, A. Kitagawa, T. Kobayashi, H. Li, T. Moriguchi, D. Nagae, S. Omika, A. Ozawa, S. Sato, S. Suzuki, T. Suzuki, N. Tadano,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011024
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] MCP with delay-line anode used for position sensitive detector at Rare RI-Ring (2021)
  • Author(s): H. Li, Z. Ge, S. Naimi, D. Nagae, Y. Abe, T. Uesaka, F. Suzaki, M. Wakasugi, S. Omika, Y. Yamaguchi, T. Yamaguchi, K. Wakayama, H. Arakawa, K. Inomata, A. Ozawa, S. Suzuki, T. Moriguchi,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011025
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Development of experimental devices for precise mass measurements at the Rare-RI Ring (2021)
  • Author(s): S. Omika, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, Z. Ge, K. Inomata, D. Kamioka, H. Li, H. Miura, T. Moriguchi, D. Nagae, S. Naimi, K. Nishimuro, A. Ozawa, F. Suzaki, S. Suzuki, T. Suzuki, N. Tadano, T. Uesaka, M. Wakasugi, K. Wakayama, Y. Yanagisawa, Y. Yamaguchi,
  • Journal Title: JPS Conf. Proc. Volume: 35
  • DOI: 10.7566/jpscp.35.011026
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] In-ring velocity measurement for isochronous mass spectrometry (2021)
  • Author(s): X. Zhou, M. Zhang, M. Wang, Y. H. Zhang, Y. J. Yuan, X. L. Yan, X. H. Zhou, H. S. Xu, X. C. Chen, Y. M. Xing, et al.
  • Journal Title: Phys. Rev. AB Volume: 24 Issue: 4
  • DOI: 10.1103/physrevaccelbeams.24.042802
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] 稀少RIリングにおける共鳴Schottky検出器の開発現状 (2024)
  • Author(s): 滝浦 一樹
  • Organizer: 日本物理学会2024年春季大会
• [Presentation] Present status of the storage-ring mass spectrometer at RIBF (2023)
  • Author(s): T. Yamaguchi
  • Organizer: International Symposium on Stored Ions for Precision Measurement
  • Int'l Joint Research / Invited
• [Presentation] Challenge to exotic nuclei-Rare RI storage ring facility at RIBF (2023)
  • Author(s): T. Yamaguchi
  • Organizer: The 3rd International Workshop on “Origin of Elements and Cosmic Evolution:From Big-Bang to Supernovae and Mergers”(OECE2023)
  • Int'l Joint Research / Invited
• [Presentation] Storage ring facilities for radioactive ions new detectors and upgrade plans (2023)
  • Author(s): T. Yamaguchi
  • Organizer: 4th International conference on Advances in Radioactive Isotope Science
  • Int'l Joint Research
• [Presentation] 多価イオンビームによる2光子稀崩壊の観測 (2023)
  • Author(s): 山口 貴之
  • Organizer: 新学術領域研究「宇宙観測検出器と量子ビームの出会い。新たな応用への架け橋。」領域研究会
  • Invited
• [Presentation] Present status of the Rare-RI Ring Facility (2023)
  • Author(s): T. Yamaguchi
  • Organizer: RIBF Users Meeting 2023
  • Int'l Joint Research / Invited
• [Presentation] 多価イオンビームによる2光子稀崩壊の観測 (2022)
  • Author(s): 山口 貴之
  • Organizer: 新学術領域研究「宇宙観測検出器と量子ビームの出会い。新たな応用への架け橋。」領域研究会
  • Invited
• [Presentation] Precision experiments of exotic nuclei at the storage rings (2021)
  • Author(s): T. Yamaguchi
  • Organizer: Tsukuba Global Science Week 2021
  • Int'l Joint Research / Invited