Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)

Research Facility Development Division
Instrumentation Development Group
1. Abstract

This group develops the core-experimental instruments at the RI Beam Factory. Three projects are currently going on. SCRIT is
the world’s ﬁrst experimental facility for electron scattering of unstable nuclei and was constructed oﬀ the main beamline of RIBF.
The ﬁrst physic result was demonstrated in 2017. After years of developments and improvements, the world’s ﬁrst electron scatteringexperiment with online-produced radioactive isotopes has been successfully conducted in 2022. An upgrade of the electron beam
power that drives RI beam production is currently underway. The Rare-RI Ring is an event-by-event-operated heavy ion storage ringfor precise mass measurement of extremely rare exotic nuclei. It is currently accepting applications for experimental proposals and has
already conducted PAC-approved experiments and published its ﬁrst physics results. In 2022, we conﬁrmed that the new capacitorsof the kicker-magnet system worked well during long-time test. Thus, the problem in the operation has been solved so far. Moreimprovements are currently underway to achieve more precise mass measurements and stable operation. The compact heavy-ion
storage ring RUNBA is an R&D machine for the development of beam recycling techniques for nuclear reaction research on rareelements. This is currently under construction and some of the critical components of the ring are currently undergoing technicaldevelopment.
All instrumentations are designed to maximize the research potential of the world’s most intense RI beams, and dedicated RI
Beam Factory equipment makes the experimental challenge possible. The experimental technique and experience accumulated in thisgroup provide opportunities for new experimental challenges and form the basis for the future development of the RIBF.

2. Major Research Subjects(1) SCRIT Project (electron scattering oﬀ unstable nuclei)(2) Rear RI Ring Project (precise mass measurement)(3) RUNBA project (Beam recycling techniques)

3. Summary of Research Activity

We are developing beam manipulation techniques to carry out the above projects. These are high-quality slow RI beam generation
technology (SCRIT), beam cooling and stopping technology (SCRIT) and beam accumulation technology in a storage ring (Rare RIRing, RUNBA). The technical know-how accumulated in the project will play a major role in the next generation of RIBF. The current
status and future plans for SCRIT and Rare-RI Ring are described in the respective sections.
In 2022, we successfully conducted the world’s ﬁrst electron scattering experiment with online-produced unstable nuclei, which is137
Cs isotopes, through years of the developments and improvements. We are in the process of power upgrading of the electron beamfrom the RTM, which is the driving for RI production, and expanding the nuclei that can be accessed. The Rare RI Ring is an eventby-event based mass measurement system, designed speciﬁcally for extremely low-producing isotopes. We carried out PAC-approved
experiments and successfully measured the masses of 74, 76 Ni, 122 Rh, 123, 124 Pd and 125 Ag for the ﬁrst time. To improve mass resolution
and eﬃciency, the ﬁrst-response kicker system and optical tuning system are being improved. To ensure stable operation, the newcapacitors were tested with a kicker manet system with good results. According to the future plans of Nishina center, a beam re-cycling
technique is under development. Beam recycling technology allows the circulation of RI beams to be maintained in a storage ringwith a thin internal target until a nuclear reaction occurs. In order to establish beam recirculation, the increase in energy width andemittance needs to be compensated for using a fast feedback system. We have demonstrated the possibility of compensation in ananalytical way and found the properties of EDC and ADC devices necessary for compensation. To develop these new technologies,
a compact heavy ion storage ring (RUNBA) connected to ISOL (ERIS) is under construction at the SCRIT facility. Under a researchcooperation agreement with ICR in Kyoto University, technical development of the main components required for RUNBA i.e. thecharge breeder, energy dispersion corrector, angular diﬀusion corrector and internal target system are underway. We developed theprototype devices for EDC and ADC devices, and further improvements are ongoing. Furthermore, we also developed the simulation
code based on the analytical model, and evaluated the performance of RUNBA.

Members
Directors
Tetsuya OHNISHIMasanori WAKASUGIContract Researcher
Ryo OGAWARA
Visiting Scientists
Shun IIMURA (Rikkyo Univ.)
Daisuke NAGAE (Tokyo Tech)
Ryo OGAWARA (Kyoto Univ.)
Akira OZAWA (Tsukuba Univ.)

Fumi SUZAKI (JAEA)
Kyo TSUKADA (Kyoto Univ.)
Masanori WAKASUGI (Kyoto Univ.)- 301 -

Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)

Student Trainees
Yuki ITO (Kyoto Univ.)
Yusei MAEDA (Kyoto Univ.)
Yoshiki MAEHARA (Kyoto Univ.)
Mariko TACHIBANA (Kyoto Univ.)

Fuuma TOUJOU (Rikkyo Univ.)
Tsubasa YAMANO (Rikkyo Univ.)
Satoru YOSHIDA (Kyoto Univ.)

Administrative Part-time Worker
Midori TAKEMON

List of Publication & Presentations
Publication[Review Article]
M. Wakasugi, Y. Abe, Y. Ito, T. Ohnishi, R. Ogawara, K. Kuze, S. Takagi, K. Tsukada, H. Tongu, Y. Maehara, and Y. Yamaguchi,“Recycled-Unstable-Nuclear Beam Accumulator (RUNBA) for developing beam recycling technique toward the study of nuclear reaction for rare RIs,” J. Part. Accl. Soc. Jpn. 19, 25 (2022).

Presentations[Domestic Conferences/Workshops]

小川原亮 (口頭発表), 「RI-RI 反応実験を目的としたビームリサイクル技術開発用蓄積リング（RUNBA）の動作原理」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
小川原亮 (口頭発表), 「ビームリサイクル技術開発を目的とした重イオン蓄積リング RUNBA の動作原理」, 第 19 回日本加速器学会年会, オンライン, 2022 年 10 月 18–21 日.

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