Elucidation of the r-process second peak from key nuclear mass measurements at N=82 with the Rare-RI Ring at RIKEN/RIBF

2019 年度 実施状況報告書

• 研究課題/領域番号: 19K03901
• 研究機関: 国立研究開発法人理化学研究所
• 研究代表者: Naimi Sarah 国立研究開発法人理化学研究所, 開拓研究本部, 研究員 (40747135)
• 研究期間 (年度): 2019-04-01 – 2022-03-31
• キーワード: Nuclear masses / r-process / Storage Ring / Position detector

研究実績の概要

I have measured 4 new masses with the Rare-RI Ring, 122Rh, 123Pd, 124Pd and 125Ag that are relevant for the r-process study. We reported about these mass measurements at the International Nuclear Physics Conference held last year and the paper reporting about the experiment has been accepted for publication in the conference proceeding. Further data analysis and preparation of publications are still ongoing, which is part of the thesis of my PhD student.
To measure more neutron-rich rare isotopes, we need more accurate injection into the Rare-RI Ring of these rare isotopes. For that a diagnostics detector is needed inside the ring.
The development of the position-sensitive detector is going smoothly. We tested improved design of the detector at the HIMAC facility as planned. The results we achieved are promising. The position resolution of the detector was improved by 30% and the accuracy by 80%. There is more room to improve the position resolution, the initial goal was 70% improvement. The development of the position-sensitive detector was part of the Master thesis of my student from the University of Surrey in the UK. The student has graduated and the development of the detector is published in his master thesis. We also submitted a report of the HIMAC experiment to the Riken Accelerator Progress Report.

現在までの達成度 (区分)

2: おおむね順調に進展している

理由

I measured 4 new nuclear masses and I plan to measure more masses within the next 2 years.
I tested the position-sensitive detector at the HIMAC facility and the tests gave promising results.

今後の研究の推進方策

To continue mass measurements of extremely rare isotopes with the Rare-RI Ring at Riken, we need to improve diagnostics inside the ring. The position-sensitive detector needs improvement and still under development. This year I will concentrate on improving the detector performance, especially its resolution to reach the initial 70% improvement. With my new Master student, we will test an improved geometry of the detector this year at the HIMAC facility. If we achieve this goal, then I will install the new detector inside the Rare-RI Ring and perform mass measurements of even more neutron-rich Palladium and Silver rare isotopes.

次年度使用額が生じた理由

My original plan was to solve at the same time two main issues of the position-sensitive detector: accuracy and resolution. After consideration, I decided to focus on one problem at a time. Therefore, I didn't use the full allocated budget as originally planned. Last year our effort were mainly focused on the detector's position accuracy, which we improved considerably. This year I will use the remaining budget to focus on improving the position resolution of the detector.

研究成果

• [雑誌論文] Efficiency and timing performance of time-of-flight detector utilizing thin foils and crossed static electric and magnetic fields for mass measurements with Rare-RI Ring facility (2020)
  • 著者名/発表者名: S. Suzuki, A. Ozawa, D. Kamioka, Y. Abe, M. Amano, H. Arakawa, Z. Ge, K. Hiraishi, Y. Ichikawa, K. Inomata, A. Kitagawa, T. Kobayashi, Hg. Li, T. Matsumoto, T. Moriguchi, M. Mukai, D. Nagae, S. Naimi, S. Omika, S. Sato, Y. Tajiri, K. Wakayama, T. Yamaguchi
  • 雑誌名: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 巻: 965 ページ: 163807
  • DOI: https://doi.org/10.1016/j.nima.2020.163807
  • 査読あり / 国際共著
• [雑誌論文] Development of a new in-ring beam monitor in the Rare-RI Ring (2019)
  • 著者名/発表者名: S. Omika, T. Yamaguchi, N. Tadano, Y. Abe, M. Amano, Z. Ge, D. Kamioka, T. Moriguchi, D. Nagae, S. Naimi, A. Ozawa, F. Suzaki, S. Suzuki, T. Suzuki, T. Uesaka, M. Wakasugi, K. Wakayama, Y. Yamaguchi
  • 雑誌名: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 巻: 463 ページ: 241-243
  • DOI: https://doi.org/10.1016/j.nimb.2019.05.029
  • 査読あり / 国際共著
• [雑誌論文] Mass Measurements with the Rare-RI Ring for the A=130 r-process Abundance Peak (2019)
  • 著者名/発表者名: S. Naimi et al.
  • 雑誌名: Riken Acceleration Progress Report 巻: 52 ページ: 102
  • 査読あり / オープンアクセス
• [雑誌論文] Preliminary analysis of mass measurement experiment in the south-western region of 132Sn with Rare RI Ring (2019)
  • 著者名/発表者名: H.F. Li, S. Naimi et al.
  • 雑誌名: Riken Acceleration Progress Report 巻: 52 ページ: 52
  • 査読あり / オープンアクセス
• [学会発表] First Mass Measurements with the Rare-RI Ring at RIBF/RIKEN for Nuclear Astrophysics (2019)
  • 著者名/発表者名: Sarah Naimi
  • 学会等名: 27th International Nuclear Physics Conference 2019
• [学会発表] Mass measurement of neutron-rich 122Rh, 123,124Pd and 125Ag nuclides with Rare-RI Ring at RIBF in RIKEN (2019)
  • 著者名/発表者名: Hongfu Li
  • 学会等名: 27th International Nuclear Physics Conference 2019