Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)

Nuclear Science and Transmutation Research Division
Superheavy Element Research Group
Superheavy Element Production Team
1. Abstract

The elements with atomic number Z ≥ 104 are called as trans-actinide or superheavy elements (SHEs). Superheavy Element
Production Team synthesizes SHE nuclei including new elements and investigates synthesis mechanisms of SHE nuclei, nuclear
properties of SHE nuclei, and chemical properties of SHEs in collaboration with Superheavy Element Devise Development Team andNuclear Chemistry Research Team of RIKEN Nishina Center.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Search for new superheavy elements
Decay spectroscopy of the heaviest nuclei
Study of reaction mechanisms for production of the heaviest nuclei
Study of chemical properties of the heaviest elements

3. Summary of Research Activity(1) Search for new superheavy elements
In November 2016, the 7th period of the periodic table was completed with the oﬃcial approval of four new elements, nihonium(Nh, Z = 113), moscovium (Mc, Z = 115), tennessine (Ts, Z = 117), and oganesson (Og, Z = 118) by International Union of Pureand Applied Chemistry. We have started to search for new elements to expand the chart of the nuclides toward to the island of stability
and the periodic table of the elements toward the 8th period. In January 2020, RIKEN heavy-ion Linear ACcelerator (RILAC) wasupgraded as Superconducting RIKEN heavy-ion Linear ACcelerator (SRILAC). We installed the new gas-ﬁlled recoil ion separator
GARIS-III on the beam line of SRILAC. In June–July 2020, we conducted the commissioning of SRILAC and GARIS-III using the169
Tm + 40 Ar, 208 Pb + 40 Ar, and 208 Pb + 51 V reactions. Since October 2020, we have been conducting a synthesis experiment ofisotopes of new element 119 in the 248 Cm + 51 V reaction under the nSHE collaboration.
(2) Study of reaction mechanisms for production of the heaviest nuclei
SHE nuclei have been produced by complete fusion reactions of two heavy nuclei. However, the reaction mechanism of thefusion process is still not well understood both theoretically and experimentally. In 2022, the quasielastic barrier distribution of the51
V + 248 Cm reaction was extracted by measuring the excitation function of quasielastic backscattering using GARIS-III at SRILAC. The result was utilized to estimate the optimal incident beam energy for production of isotopes of new element 119 in the248
Cm(51 V, xn)299−x 119 reactions. We also measured the excitation functions for the evaporation residues and the quasielastic scattering of the 51 V + 159 Tb reaction to deepen our understanding of the 51 V-induced reaction on the deformed target.
(3) Study of chemical properties of the heaviest elements
Chemical characterization of newly-discovered SHEs is an extremely interesting and challenging research subject in modern
nuclear and radiochemistry. In collaboration with Nuclear Chemistry Research Team of RIKEN Nishina Center, we are developing
SHE production systems as well as rapid single-atom chemistry apparatuses for chemistry studies of SHEs. We installed a gas-jet
transport system to the focal plane of GARIS at RILAC. This system is a promising approach for exploring new frontiers in SHE
chemistry: the background radiations from unwanted products are strongly suppressed, the intense primary heavy-ion beam is absent
in the gas-jet chamber, and hence the high gas-jet extraction yield is attained. Furthermore, the beam-free conditions make it possible
to investigate new chemical systems. In 2022, we continued to develop an ultra-rapid gas-chromatograph apparatus, which consists ofan RF carpet gas cell and a cryo-gas-chromatograph column with a Si detector array, at the focal plane of GARIS for the gas chemistryof SHEs. To realize aqueous chemistry studies of Sg (Z = 106) and Bh (Z = 107), we have been developing a continuous andrapid solvent extraction apparatus which consists of a continuous dissolution apparatus Membrane DeGasser (MDG), a Flow Solvent
Extractor (FSE), and a liquid scintillation detector for α/SF-spectrometry. In collaboration with Osaka University, co-precipitation
behavior of No (Z = 102) with BaSO4 and CaC2 O4 was also investigated with 255 No produced in the 248 Cm(12 C, 5n)255 No reaction atthe AVF cyclotron.

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Ⅵ. ORGANIZATION AND ACTIVITIES OF RNC

RIKEN Accel. Prog. Rep. 56 (2023)

Members
Team Leader
Hiromitsu HABA
Research & Development Scientist
Daiya KAJI
Visiting Scientists
Marc ASFARI (IPHC/Univ. of Strasbourg)
Mahananda DASGUPTA (Australian Nat’l Univ.)
Olivier DORVAUX (Univ. of Strasbourg)
Benoit Jean-Paul GALL (Univ. of Strasbourg)
Zaiguo GAN (Inst. of Modern Phys./Chinese Academy of Sci.)
David HINDE (Australian Nat’l Univ.)
Minghui HUANG (Inst. of Modern Phys./Chinese Academy ofSci.)
Kieran KESSACI (Univ. of Strasbourg)
Student Trainees
Margaux S.A. FORGE (Univ. of Strasbourg)
Takumi FUKATSU (Kyushu Univ.)
Yuichi ISHIBASHI (Kyushu Univ.)
Sotaro MATSUNAGA (Kyushu Univ.)
Haruki MATSUURA (Kyushu Univ.)

Hiroyuki KOURA (JAEA)
Daisuke NAGAE (Tokyo Tech)
Satoshi SAKAGUCHI (Kyushu Univ.)
Mirei TAKEYAMA (Yamagata Univ.)
Taiki TANAKA (Australian Nat’l Univ.)
Huabin YANG (Inst. of Modern Phys./Chinese Academy ofSci.)
Zhiyuan ZHANG (Inst. of Modern Phys./Chinese Academy ofSci.)
Yuya MICHIMOTO (Kyushu Univ.)
Mikito NOMI (Kyushu Univ.)
Koichi SUGIYAMA (Kyushu Univ.)
Yuki YAMANOUCHI (Kyushu Univ.)

InternMargaux S.A. FORGE (Univ. of Strasbourg)

List of Publications & Presentations
Publications[Original Papers]
A. Yakushev, L. Lens, Ch.E. Düllmann, J. Khuyagbaatar, E. Jäger, J. Krier, J. Runke, H. M. Albers, M. Asai, M. Block, J. Despotopulos,A. Di Nitto, K. Eberhardt, U. Forsberg, P. Golubev, M. Götz, S. Götz, H. Haba, L. Harkness-Brennan, R.-D. Herzberg, F. P. Heßberger,
D. Hinde, A. Hübner, D. Judson, B. Kindler, Y. Komori, J. Konki, J. V. Kratz, N. Kurz, M. Laatiaoui, S. Lahiri, B. Lommel, M. Maiti,A. Mistry, Ch. Mokry, K. J. Moody, Y. Nagame, J. P. Omtvedt, P. Papadakis, V. Pershina, D. Rudolph, L. G. Samiento, T. K. Sato,M. Schädel, P. Scharrer, B. Schausten, D. A. Shaughnessy, J. Steiner, P. Thörle-Pospiech, A. Toyoshima, N. Trautmann, K. Tsukada,J. Uusitalo, K.-O. Voss, A. Ward, M. Wegrzecki, N. Wiehl, E. Williams, and V. Yakusheva, “On the adsorption and reactivity of element
114, ﬂerovium,” Front. Chem. 10, published online (August 25, 2022). DOI: 10.3389/fchem.2022.976635 .
M. Tanaka, P. Brionnet, M. Du, J. Ezold, K. Felker, B. J. P. Gall, S. Go, R. K. Grzywacz, H. Haba, K. Hagino, S. Hogle, S. Ishizawa,D. Kaji, S. Kimura, T. T. King, Y. Komori, R. K. Lemon, M. G. Leonard, K. Morimoto, K. Morita, D. Nagae, N. Naito, T. Niwase,B. C. Rasco, J. B. Roberto, K. P. Rykaczewski, S. Sakaguchi, H. Sakai, Y. Shigekawa, D. W. Stracener, S. VanCleve, Y. Wang,K. Washiyama, and T. Yokokita, “Probing optimal reaction energy for synthesis of element 119 from 51 V + 248 Cm reaction withquasielastic barrier distribution measurement,” J. Phys. Soc. Jpn. 91, 084201-1–11 (2022).
A. C. Berriman, D. J. Hinde, D. Y. Jeung, M. Dasgupta, H. Haba, T. Tanaka, K. Banerjee, T. Banerjee, L. T. Bezzina, J. Buete, K. J. Cook,S. Parker-Steele, C. Sengupta, C. Simenel, E. C. Simpson, M. A. Stoyer, B. M. A. Swinton-Bland, and E. Williams, “Energy dependenceof p + 232 Th ﬁssion mass distributions: Mass-asymmetric standard I and standard II modes, and multichance ﬁssion,” Phys. Rev. C 105,064614-1–18 (2022).
H. Sakai, H. Haba, K. Morimoto, and N. Sakamoto, “Facility upgrade for superheavy-element research at RIKEN,” Eur. Phys. J. A 58,
238-1–15 (2022).

[Review Article]

羽場宏光, 「人工元素合成」, 科学 92, 846–851 (2022).

[Books]

羽場宏光, 「元素探索と RI 製造」 in 「量子ビーム科学の基礎と応用」, NSA/Commentaries 27, 一般社団法人日本原子力産業協会
原子力システム研究懇話会, 195 ページ, 2023 年 3 月 24 日, p. 26–39.
桜井弘（編）, 荒野泰, 小谷明, 高妻孝光, 佐治英郎, 鈴木晋一郎, 中山祐正, 根矢三郎, 羽場宏光, 廣田俊, 藤井敏司, 「ブルーバックス
元素 118 の新知識 第 2 版」
, 講談社, 2023 年 3 月 20 日, p. 560.

[Proceeding]

H. Sakai, H. Haba, K. Morimoto, and N. Sakamoto, “Facility upgrade for SHE research at RIKEN Nishina Center,” Acta Phys. Pol. B
Proc. Suppl. 16, 4-A10-1–12 (2023).

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RIKEN Accel. Prog. Rep. 56 (2023)

Presentations[International Conferences/Workshops]
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory—Search for new elements through diagnosis
and therapy of cancer—,” Laser Solutions for Space and the Earth 2022 in OPTICS & PHOTONICS International Congress 2022 (OPIC2022), Yokohama, Japan & Online, April 18–22, 2022.
M. Tanaka (invited) for nSHE Collaboration, “Quasielastic backscattering measurement for 51 V + 248 Cm reaction toward element-119
synthesis at RIKEN,” 19th Workshop on Recoil Separator for Superheavy Element Chemistry & Physics (TASCA 22), Darmstadt,
Germany & Online, May 10–12, 2022.
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory—Search for new elements through diagnosis
and therapy of cancer—,” IAEA/RCA RTC on Good Manufacturing Practice (GMP) and Radiation Safety Aspects of Radiopharmaceutical Production Using Medical Cyclotron, Online, May16–20, 2022.
H. Sakai (invited), H. Haba, K. Morimoto, and N. Sakamoto, “Facility upgrade for SHE research at RIKEN,” Zakopane Conference on
Nuclear Physics, “Extremes of the Nuclear Landscape,” Zakopane, Poland, August 28–September 4, 2022.
M. Tanaka (oral) for nSHE Collaboration, “Optimal energy for element 119 synthesis via 51 V + 248 Cm reaction probed by quasielastic
barrier distribution measurement,” Zakopane Conference on Nuclear Physics, “Extremes of the nuclear landscape,” Zakopane, Poland,August 28–September 4, 2022.
S. Sakaguchi (poster) and M. Tanaka for nSHE Collaboration, “Probing optimal energy for synthesis of element 119 from 51 V+248 Cmreaction,” The 28th International Nuclear Physics Conference (INPC 2022), Cape Town, South Africa, September 11–16, 2022.
A. Takamine (invited), D. Kaji, H. Haba, M. Wada, P. Schury, H. Koura, H. Wollnik, H. Miyatake, H. Ishiyama, K. Morimoto, M. Rosenbusch, S. Kimura, T. Niwase, Y. Hirayama, Y. Ito, Y. Watanabe, and P. Brionnet, “Multi-reﬂection time-of-ﬂight mass spectroscopy ofsuperheavy nuclides,” 19th International Conference on Electromagnetic Isotope Separators and Related Topics (EMIS 2022), Daejeon,Korea, October 3–7, 2022.
M. Tanaka (oral), “Optimal reaction energy for synthesis of element 119 via 51 V + 248 Cm reaction probed by quasielastic barrier distribution measurement,” 19th International Conference on Electromagnetic Isotope Separators and Related Topics (EMIS 2022), Daejeon,Korea, October 3–7, 2022.
P. Brionnet (poster), R. Grzywacz, D. Kaji, T. King, T. Niwase, K. Morimoto, and K. Rykaczewski, “Development and optimization ofthe digital electronic for the search of new super heavy element at RIKEN on GARIS-III,” 19th International Conference on Electromagnetic Isotope Separators and Related Topics (EMIS 2022), Daejeon, Korea, October 3–7, 2022.
H. Haba (invited), “Production and distribution of radioisotopes at RIKEN RI Beam Factory,” PRISMAP Workshop on Emerging Infrastructures and Technical Developments, Padova, Italy & Online, November 21–22, 2022.
H. Haba (invited), “Production of radioisotopes for application studies at RIKEN RI Beam Factory—Search for new elements throughdiagnosis and therapy of cancer,” The Fifth International Conference on Application of RadiotraCers and Energetic Beams in Sciences(ARCEBS 2023), Purulia, India, January 31–February 5, 2023.

[Domestic Conferences/Workshops]

永井歩夢 (口頭発表), 細川浩由, 中島朗久, 坂口綾, 南部明弘, 重河優大, 羽場宏光, 横山明彦, 「232 Th + 7 Li 核反応によって生成する
U 同位体の ICP-MS による定量」, 日本放射化学会第 66 回討論会 (2022), 文京区, 2022 年 9 月 15–17 日.
渡邉瑛介 (口頭発表), 笠松良崇, 横北卓也, 中西諒平, 大髙咲希, 板倉悠大, 益田遼太郎, 王瑞麟, 重河優大, 南部明弘, 殷小杰, 羽場宏光,高宮幸一, 篠原厚, 「クラウンエーテルを用いた 102 番元素ノーベリウムの硝酸系固液抽出実験」, 日本放射化学会第 66 回討論会 (2022), 文京区, 2022 年 9 月 15–17 日.
中西諒平 (口頭発表), 渡邉瑛介, 大髙咲希, 王瑞麟, 板倉悠大, 速水翔, 羽場宏光, 南部明弘, 篠原厚, 笠松良崇, 「Rf の共沈実験に向けた Zr, Hf, Th のシュウ酸, マロン酸系でのフロー式共沈実験」, 日本放射化学会第 66 回討論会 (2022), 文京区, 2022 年 9 月
15–17 日.
羽場宏光 (依頼講演), 「新元素でがん治療〜理研 RI ビームファクトリーがつくるラジオアイソトープ〜」, 放射線安全フォーラム
第 75 回放射線防護研究会, 「短寿命核種の利用の拡大に向けて」, 文京区 & オンライン, 2022 年 10 月 29 日.
山ノ内邑希 (ポスター発表), 坂口聡志, Pierre Brionnet for nSHE Collaboration, 「新元素合成のための最適反応エネルギー推定に向けた 51 V + 159 Tb 融合反応の励起関数測定」, 日本物理学会 2023 年春季大会, オンライン, 2023 年 3 月 22–25 日.
深津巧光 (ポスター発表), 坂口聡志, Pierre Brionnet for nSHE Collaboration, 「新元素合成のための最適反応エネルギー推定に向けた 51 V + 159 Tb 融合反応の障壁分布測定 I」, 日本物理学会 2023 年春季大会, オンライン, 2023 年 3 月 22–25 日.
道本優也 (ポスター発表), 坂口聡志, Pierre Brionnet for nSHE Collaboration, 「新元素合成のための最適反応エネルギー推定に向けた 51 V + 159 Tb 融合反応の障壁分布測定 II」, 日本物理学会 2023 年春季大会, オンライン, 2023 年 3 月 22–25 日.

Outreach Activities

羽場宏光 (依頼講演), 「新元素でがん治療—RIBF がつくるラジオアイソトープ—」, 理研と未来を創る会第 28 回講演会, 和光市,2022 年 9 月 6 日.
羽場宏光 (依頼講演), 「ニホニウム発見への道のり」, 山梨県立吉田高等学校理研見学会, 和光市, 2022 年 11 月 16 日.

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