Study on thorium-229 Low-lying Isomer state and its application for fundamental physics

• Project/Area Number: 18H01230
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Okayama University
• Principal Investigator: Yoshimura Koji 岡山大学, 異分野基礎科学研究所, 教授 (50272464)
• Co-Investigator(Kenkyū-buntansha): 笠松 良崇 大阪大学, 理学研究科, 講師 (70435593)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥17,290,000 (Direct Cost: ¥13,300,000、Indirect Cost: ¥3,990,000); Fiscal Year 2020: ¥5,460,000 (Direct Cost: ¥4,200,000、Indirect Cost: ¥1,260,000); Fiscal Year 2019: ¥5,460,000 (Direct Cost: ¥4,200,000、Indirect Cost: ¥1,260,000); Fiscal Year 2018: ¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000)
• Keywords: 原子核時計 / トリウム / 放射光X線 / 核共鳴散乱 / 物理定数の経年変化 / X線検出器 / 暗黒物質 / レーザー / 実験核物理 / トリウム229 / 放射光Ｘ線 / 放射光 / 周波数標準 / APD / 物理定数の時間変化

Outline of Final Research Achievements

We have succeeded in artificially producing the first excited state (isomer state) of thorium-229, which has the smallest excitation energy in the world. The isomer state was produced via the second excited state by a new method using nuclear resonant scattering with high-brilliance synchrotron radiation X-rays and a fast X-ray detector. This study has enabled us to produce a large number of thorium-229 isomer states in controllable manner, and we will make effective use of the produced isomer states to elucidate the isomer states in detail.

Academic Significance and Societal Importance of the Research Achievements

本研究で達成された手法により、トリウム229のアイソマー状態の解明が進めば、トリウム原子核のレーザー励起、さらに原子核時計の早期の実現が可能となる。トリウム229を用いた原子核時計は、最先端の原子時計を上回る精度を達成できる可能性があり、様々な分野への応用が期待されている。基礎物理分野においては、物理定数の経年変化の検証、新しい手法での暗黒物質探索、等、新しい物理探究のプラットホームを提供可能である。

Research Products

• [Int'l Joint Research] TU WIEN(オーストリア)
• [Int'l Joint Research] ウィーン工科大学(オーストラリア)
• [Int'l Joint Research] UCLA(米国)
• [Int'l Joint Research] ウィーン工科大学(オーストリア)
• [Journal Article] Absolute X-ray energy measurement using a high-accuracy angle encoder (2021)
  • Author(s): Masuda Takahiko、Watanabe Tsukasa、Beeks Kjeld、Fujimoto Hiroyuki、Hiraki Takahiro、Kaino Hiroyuki、Kitao Shinji、Miyamoto Yuki、Okai Koichi、Sasao Noboru、Seto Makoto、Schumm Thorsten、Shigekawa Yudai、Tamasaku Kenji、Uetake Satoshi、Yamaguchi Atsushi、Yoda Yoshitaka、Yoshimi Akihiro、Yoshimura Koji
  • Journal Title: Journal of Synchrotron Radiation Volume: 28 Issue: 1 Pages: 111-119
  • DOI: 10.1107/s1600577520014526
  • NAID: 120006956810
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Energy response of X-rays under high flux conditions using a thin APD for the energy range of 6?33 keV (2019)
  • Author(s): Masuda T.、Hiraki T.、Kaino H.、Kishimoto S.、Miyamoto Y.、Okai K.、Okubo S.、Ozaki R.、Sasao N.、Suzuki K.、Uetake S.、Yoshimi A.、Yoshimura K.
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 913 Pages: 72-77
  • DOI: 10.1016/j.nima.2018.10.029
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Development of a measurement system enabling the reconstruction of γ-ray time spectra by simultaneous recording of energy and time information (2019)
  • Author(s): Hiroyuki Tajima, Shinji Kitao, Ryo Masuda, Yasuhiro Kobayashi, Takahiko Masuda, Koji Yoshimura and Makoto Seto
  • Journal Title: Jpn. J. Appl. Phys. Volume: 58 Issue: 10 Pages: 108001-108001
  • DOI: 10.7567/1347-4065/ab3f19
  • NAID: 210000157036
  • Peer Reviewed
• [Journal Article] X-ray pumping of the 229Th nuclear clock isomer (2019)
  • Author(s): T. Masuda, A. Yoshimi, A. Fujieda, H. Fujimoto, H. Haba et al.
  • Journal Title: Nature Volume: 573 Issue: 7773 Pages: 238-242
  • DOI: 10.1038/s41586-019-1542-3
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] 放射光で探るレーザー光による超精密原子核制の可能性:229Th極低核励起準位 (2018)
  • Author(s): 吉見彰洋、笠松良崇、北尾真司、瀬戸誠、増田孝彦、山口敦史、依田芳卓、吉村浩司
  • Journal Title: 放射光 Volume: 31 Pages: 304-314
  • Peer Reviewed
• [Presentation] Novel Production Method of the Lowest-Energy Nuclear State Thorium-229 Isomer (2020)
  • Author(s): Koji YOSHIMURA
  • Organizer: GIMRT-REMAS2020
  • Int'l Joint Research / Invited
• [Presentation] Measurement of ultra-low energy level of Thorium-229 Isomer with high intense X-ray beam (2020)
  • Author(s): K. Yoshimura
  • Organizer: The 12th International Workshop on Fundamental Physics Using Atoms (FPAU2020)
  • Int'l Joint Research / Invited
• [Presentation] 229Th 原子核極低エネルギー準位と高精度原子核時計への応用 (2020)
  • Author(s): 吉見彰洋
  • Organizer: 理研「物質階層原理＆ヘテロ界面」2019年度研究報告会
  • Invited
• [Presentation] トリウム229アイソマー準位からの真空紫外光の探索 (2020)
  • Author(s): 海野弘行
  • Organizer: 日本物理学会大７５回年次大会
• [Presentation] 高輝度X線によるトリウム-229極低エネルギーアイソマーの能動的生成ー究極の原子核時計に向けての第一歩ー (2019)
  • Author(s): 吉村浩司
  • Organizer: SPring-8シンポジウム
  • Invited
• [Presentation] Towards the spectroscopy of 229Th nuclear clock transition using Nuclear Resonant Scattering (2019)
  • Author(s): A. Yoshimi
  • Organizer: DICP Workshop on Mossbauer Spectroscopy Related to Synchrotron Radiation and Free Electron Laser
  • Int'l Joint Research / Invited
• [Presentation] Production of the 229Th nuclear clock isomer with brilliant X-ray (2019)
  • Author(s): A. Yoshimi
  • Organizer: International Nuclear Conference 2019 (INPC2019)
  • Int'l Joint Research / Invited
• [Presentation] トリウム-229 極低アイソマー準位の測定 (2019)
  • Author(s): 吉見彰洋
  • Organizer: 2019年度 大洗アルファ合同研究会
  • Invited
• [Presentation] 核共鳴散乱を利用したトリウム原子核時計の開発 (2019)
  • Author(s): 吉見彰洋
  • Organizer: 第13 回 SPRUC 核共鳴散乱研究会
  • Invited
• [Presentation] トリウム229原子核異性体からの真空紫外光観測の現状 (2019)
  • Author(s): 増田孝彦
  • Organizer: 日本物理学会2019年秋季大会
• [Presentation] X-ray pumping of the nuclear-clock isomer 229Th (2019)
  • Author(s): Takahiko Masuda
  • Organizer: The 11th international workshop on Fundamental Physics Using Atoms 2019
  • Int'l Joint Research / Invited
• [Presentation] Realization of the active pumping of thorium-229 isomeric state (2019)
  • Author(s): Takahiko Masuda
  • Organizer: Cosmic acceleration” symposium
  • Int'l Joint Research
• [Presentation] 核共鳴散乱を用いたトリウム229アイソマー準位への能動的遷移 (2019)
  • Author(s): 海野弘行
  • Organizer: 日本物理学会第74回年次学会
• [Presentation] トリウム-229 の原子核時計遷移分光 (2019)
  • Author(s): 吉見彰洋
  • Organizer: 日本物理学会第74回年次学会
• [Presentation] Search for the lowest-energy nuclear isomeric state of Th-229 toward a “nuclear clock” (2019)
  • Author(s): 平木貴宏
  • Organizer: 核化学研究会
• [Presentation] A search for the low-energy 229Th nuclear isometric transition using an “optical” pumping technique at 29-keV (2018)
  • Author(s): Satoshi Uetake
  • Organizer: International coference on atomic physics 2018
  • Int'l Joint Research
• [Presentation] トリウム229の極低エネルギー原子核時計遷移の探索 II (2018)
  • Author(s): 植竹智
  • Organizer: 日本物理学会2018秋季大会
• [Presentation] Search for the ultra-low energy isomer state of thorium-229 nuclei (2018)
  • Author(s): Takahiko Masuda
  • Organizer: 5th Joint Meeting of the Division of Nuclear Physics of the APS and the JPS
  • Int'l Joint Research
• [Presentation] Fast APD detector with a short tail in the timing response for an experiment using synchrotron radiation X-ray beam (2018)
  • Author(s): Takahiko Masuda
  • Organizer: 5th International Workshop on New Photon-Detectors
  • Int'l Joint Research