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Production and determination of Th-229m, a key material for the next generation atomic-nuclear clock

Research Project

Project/Area Number 15K13396
Research Category

Grant-in-Aid for Challenging Exploratory Research

Allocation TypeMulti-year Fund
Research Field General applied physics
Research InstitutionTohoku University

Principal Investigator

Kikunaga Hidetoshi  東北大学, 電子光理学研究センター, 准教授 (00435645)

Co-Investigator(Renkei-kenkyūsha) NANBU kenichi  東北大学, 電子光理学研究センター, 技術専門職員 (00422072)
Project Period (FY) 2015-04-01 – 2019-03-31
Project Status Completed (Fiscal Year 2018)
Budget Amount *help
¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2017: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2016: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2015: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Keywords核異性体 / 原子核励起 / トリウム / 放射化学 / 核化学 / 核励起 / 原子核 / 標準
Outline of Final Research Achievements

Thorium nucleus with a mass number of 229 (Th-229g) have a metastable state (Th-229m) with the lowest excitation energy known to date. This excitation energy is to be 7-8 eV, vacuum ultraviolet light. The transition between Th-229m and Th-229g has a potential for a high-precision "atomic nuclear" clock. However, there are no reports on direct excitation from Th-229g to Th-229m. In this study, we developed a high current electron irradiation apparatus for direct excitation of Th-229g and evaluated its performance. In addition, we also investigated a target preparation to withstand high current electron beam and prepared Th-229g material from U-233.

Academic Significance and Societal Importance of the Research Achievements

本研究には,これまで1994年に数 eVの励起エネルギーを持つ特異な原子核であることが知られて以来,誰も成功していないTh-229mの直接崩壊信号の観測を目指すという基礎科学的な意義がある。また,本研究で行われたTh-229電子線励起の試みはTh-229gのレーザー励起法の開発など次のステップに進む上での基礎データとなるため,次世代”原子核”時計を開発する上での重要な一歩となる。また,本研究の過程でU-233から分離され研究に使えるように整備されたTh-229試料は,娘核種に核医学分野で注目されるAc-225など有用RIを含むため,本研究以外にも利用されつつある。

Report

(5 results)
  • 2018 Annual Research Report   Final Research Report ( PDF )
  • 2017 Research-status Report
  • 2016 Research-status Report
  • 2015 Research-status Report
  • Research Products

    (3 results)

All 2019 2018 2016

All Journal Article (1 results) Presentation (2 results)

  • [Journal Article] Variation of the Nuclear Decay Constants of <sup>229m</sup>Th and <sup>235m</sup>U Affected by Their Chemical Environments2018

    • Author(s)
      笠松 良崇, 菊永 英寿
    • Journal Title

      RADIOISOTOPES

      Volume: 67 Issue: 10 Pages: 471-482

    • DOI

      10.3769/radioisotopes.67.471

    • NAID

      130007498076

    • ISSN
      0033-8303, 1884-4111
    • Year and Date
      2018-10-15
    • Related Report
      2018 Annual Research Report
  • [Presentation] U-233線源の利用2019

    • Author(s)
      菊永英寿
    • Organizer
      2019重元素化学ワークショップ
    • Related Report
      2018 Annual Research Report
  • [Presentation] 48Crの半減期精密測定2016

    • Author(s)
      菊永英寿,高宮幸一,大槻勤,羽場宏光
    • Organizer
      2016日本放射化学会年会
    • Place of Presentation
      新潟大学(新潟)
    • Year and Date
      2016-09-10
    • Related Report
      2016 Research-status Report

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Published: 2015-04-16   Modified: 2020-03-30  

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