Development of beam-through-type gas-cell for mass measurement of proton-rich nuclei

• Project/Area Number: 19K14750
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Kimura Sota 国立研究開発法人理化学研究所, 仁科加速器科学研究センター, 特別研究員 (10827348)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2021: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000); Fiscal Year 2020: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000); Fiscal Year 2019: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
• Keywords: ガスセル / 多重反射型飛行時間式質量分析 / 精密質量測定 / 不安定核 / X線バースト / 早い陽子捕獲過程 / 原子核質量測定

Outline of Research at the Start

爆発的天体現象であるX線バーストを駆動する核燃焼過程、速い陽子捕獲過程の解明には陽子過剰核の質量が鍵となるが必要な実験データが未だ得られていない。鍵となる陽子過剰核の寿命が短く高精度質量測定に従来手法は適さない。そこで短寿命な原子核の精密質量測定に有効で近年実用化した多重反射型飛行時間式質量分析法(MRTOF)を用いる。しかしこれまでの研究から陽子過剰核の測定には特有の困難を伴うことが分かっている。本研究では新たにビーム透過型ガスセルの開発を行うことで実験上の困難を取り除き、MRTOFを用いて陽子過剰核の精密質量測定を行う。

Outline of Final Research Achievements

A beam-through-type gas cell has been developed for the precise mass measurement of proton-rich nuclei. A new apparatus consisting of a beam-through-type gas cell and a multi-reflection time-of-flight mass spectrometer was installed in the superconducting in-flight RI beam separator BigRIPS at RIKEN, and the mass measurement experiment of neutron-rich nuclei was performed as commissioning. As a result, the masses of 88,89As, and 112Mo were experimentally determined for the first time. The beam-through-type gas cell was confirmed to have reached the practical stage, although there still is room for improvement.

Academic Significance and Societal Importance of the Research Achievements

不安定原子核を用いた種々の精密測定実験にはエネルギーの揃った高純度の低エネルギーイオンビームが必要とされている。しかし不安定核は高エネルギーのイオンとして生成されるためガスセルを用い一度低速イオンに変換する。本研究で開発したビーム透過型ガスセルは大強度の入射ビームに対してその効率を保ちつつ、更にガスセル内での不純物イオンの発生低減を狙ったものであり、不安定原子核を用いた実験の可能性を大きく広げるものである。

Research Products

• [Journal Article] Study of the N = 32 and N = 34 Shell Gap for Ti and V by the First High-Precision Multireflection Time-of-Flight Mass Measurements at BigRIPS-SLOWRI (2023)
  • Author(s): Iimura S.、Rosenbusch M.、Takamine A.、Tsunoda Y.、Wada M.、Chen S.、Hou D.S.、Xian W.、Ishiyama H.、Yan S.、Schury P.、Crawford H.、Doornenbal P.、Hirayama Y.、Ito Y.、Kimura S.、Koiwai T.、Kojima T.M.、Koura H.、Lee J.、Liu J.、Michimasa S.、Miyatake H.、Moon J.Y.、Naimi S.、Nishimura S. et al.
  • Journal Title: Physical Review Letters Volume: 130 Issue: 1 Pages: 1-6
  • DOI: 10.1103/physrevlett.130.012501
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] The new MRTOF mass spectrograph following the ZeroDegree spectrometer at RIKEN’s RIBF facility (2023)
  • Author(s): Rosenbusch M.、Wada M.、Chen S.、Takamine A.、Iimura S.、Hou D.、Xian W.、Yan S.、Schury P.、Hirayama Y.、Ito Y.、Ishiyama H.、Kimura S.、Kojima T.、Lee J.、Liu J.、Michimasa S.、Miyatake H.、Moon J.Y.、Mukai M.、Naimi S.、Nishimura S.、Niwase T.、Sonoda T.、Watanabe Y.X.、Wollnik H.
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 1047 Pages: 167824-167824
  • DOI: 10.1016/j.nima.2022.167824
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Study of the neutron-rich 252Cf-fission-fragments with MRTOF-MS (2022)
  • Author(s): S. Kimura
  • Organizer: the 16th International Symposium on Origin of Matter and Evolution of Galaxies
  • Int'l Joint Research
• [Presentation] MRTOF-MSを用いた252Cf自発核分裂片の網羅的精密質量測定 (2022)
  • Author(s): 木村創大
  • Organizer: 日本物理学会第77回年次大会
• [Presentation] MRTOF-MSを用いた252Cf核分裂片の精密質量測定 (2020)
  • Author(s): 木村創大
  • Organizer: 日本物理学会第７５回年次大会