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Kumar, V.*; Chapman, R.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; Wady, P.*; 他10名*
Physical Review C, 110(4), p.044308_1 - 044308_18, 2024/10
被引用回数:0 パーセンタイル:0.00(Physics, Nuclear)Excited states of the molybdenum isotopes Mo were populated in two experiments which used fusion-fission and binary grazing reactions. In the first experiment, the GASP array of Ge detectors was used to detect
rays from fusion-fission products from the
S +
Yb reaction at 230 MeV. In the multinucleon transfer experiment, a 530-MeV beam of
Zr ions was incident on a thin
Sn target; projectile-like ejectiles were detected and identified using the PRISMA magnetic spectrometer and their associated
rays detected using the CLARA array of Clover detectors. Previously known bands were extended in all isotopes, and a new g
band was established in
Mo. The observed level schemes were compared with shell-model calculations, which reproduce the general features of the energy spectrum of excited states of
Mo,
Mo, and
Mo, although not in detail. For the h
negative-parity decay sequences of the three isotopes studied, evidence is presented for nuclear shape changes with increasing neutron number.
Jungclaus, A.*; Grska, M.*; Mikolajczuk, M.*; Acosta, J.*; Taprogge, J.*; 西村 俊二*; Doornenbal, P.*; Orlandi, R.; 他55名*
Physical Review Letters, 132(22), p.222501_1 - 222501_7, 2024/05
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)At the RIBF facility in RIKEN, the half-lives of the 6 and 8
excited states of semi-magic nucleus
Cd were measured, and the B(E2) transition matrix elements of the corresponding transitions were deduced. This information was used to determine the effective proton charges in
Cd. By comparing these new results with the effective charges deduced from a previous measurement of
Cd, the effective charges near doubly magic
Sn and
Sn could be compared for the first time. This revealed an unexpected large decrease of the isovector effective charges due to the increasing number of neutrons. This information is very important for state-of-the-art large scale shell model calculations.
Benito, J.*; Lenzi, S. M.*; Recchia, F.*; Axiotis, M.*; Aydin, S.*; Bazzacco, D.*; Benzoni, G.*; Orlandi, R.; 他37名*
Acta Physica Polonica B; Proceedings Supplement, 17(3), p.3-A4_1 - 3-A4_7, 2024/04
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)Excited states of neutron-rich Fe isotopes have been studied through a multinucleon transfer reaction of a
Zn beam on a
U target at the National Laboratories of Legnaro, Italy. The magnetic spectrometer PRISMA was used to identified the isotopes produced in the reaction, and the CLARA array of Clover Ge detectors to detect their gamma rays. The obtained level scheme were compared with new, state-of-the-art large scale shell model calculations. The large model space used in the calculation, which included the 2d
orbital, revealed that this orbit is key in order to obtain excellent agreement between the calculations and the experimental data.
Fujikawa, Y.*; Kawabata, T.*; Adachi, S.*; 廣瀬 健太郎; 牧井 宏之; 西尾 勝久; Orlandi, R.; 洲嵜 ふみ; 他13名*
Physics Letters B, 848, p.138384_1 - 138384_6, 2024/01
被引用回数:5 パーセンタイル:79.77(Astronomy & Astrophysics)We searched for the 6-condensed state in
Mg by measuring the
C+
C scattering with the SAKRA Si detector array. By using the invariant-mass method for the detected 3
particles, the inclusive cross sections for the
C+
C
C(0
) + X and
C(3
) + X reactions were determined. In both the inclusive
C(0
) + X channel and the exclusive
C(0
) +
C(0
) channel, the cross section peaked at E
= 19.4 MeV, which correspond to the excitation energy of E
= 33.3 MeV in
Mg. This 19.4-MeV state is a candidate for the 6
-condensed state
Kumar, V.*; Chapman, R.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; 他13名*
Physical Review C, 108(4), p.044313_1 - 044313_19, 2023/10
被引用回数:1 パーセンタイル:30.87(Physics, Nuclear)The nuclear structure of neutron-rich niobium isotopes Nb were studied at the Legnaro National Laboratories using
-ray spectroscopy. The isotopes were produced in two different experiments, either using multi-nucleon transfer reactions of
Zr 530-MeV beam onto a
Sn target, or via fusion-fission of
S on
Yb. The level schemes of these isotopes were extended respectively up to excitation energies of 4545, 5409, and 3814 keV. The structure of the low-lying states in these isotopes was interpreted and discussed in the context of shell-model calculations. In particular, for the
Nb isotope (
=41,
=58), the results indicate the presence of shape-coexistence at low-energies, which was observed for the first time in this isotope.
Pedersen, L. G.*; Sahin, E.*; Grgen, A.*; Bello Garrote, F. L.*; Orlandi, R.; 他61名*
Acta Physica Polonica B; Proceedings Supplement, 16(4), p.4-A14_1 - 4-A14_6, 2023/08
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)Excited states in Cu were observed for the first time following the
decay of
Ni created by in-flight fission of
U. Based on the coincidences with the observed
-ray transitions, a level scheme comprising eight excited states was constructed, with tentative spin assignments for 5 of them. In addition to the
-decaying states, an isomeric state with a lifetime of 3.8(4) ms was also found to decay by internal conversion.
岩元 大樹; 中野 敬太; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 杉原 健太*; 西尾 勝久; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; et al.
EPJ Web of Conferences, 284, p.01023_1 - 01023_4, 2023/05
被引用回数:0 パーセンタイル:0.00(Nuclear Science & Technology)加速器駆動システム(ADS)の核特性予測精度の向上と京都大学臨界集合体実験装置(KUCA)におけるADS炉物理実験で用いる中性子源情報の取得を目的として、京都大学の固定磁場強集束(FFAG)加速器を用いた核データ測定実験プログラムを開始した。このプログラムの一環として、鉄,鉛及びビスマスに対する陽子入射二重微分中性子収量(TTNY)及び断面積(DDX)を測定した。測定では、真空チェンバ内に設置された標的試料に107MeVの陽子ビームを照射し、核反応によって標的から発生した粒子の信号を、小型の中性子検出器を用いて検出した。検出信号とFFAGキッカー電磁石の信号の時間差から飛行時間(TOF)を求め、ガンマ線の事象を波形弁別法によって除去して中性子事象をカウントすることで中性子のTOFスペクトルを求めた。得られた中性子のTOFスペクトルから、相対論的運動学によりTTNY及びDDXを求めた。実験で得られたTTNY及びDDXを、モンテカルロ輸送計算コードPHITSによる計算と比較し、PHITSに組み込まれた核反応モデル及び評価済み核データライブラリJENDL-4.0/HEの妥当性を検証するとともに、PHITSによる計算の予測精度を評価した。
岩元 大樹; 中野 敬太; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 杉原 健太; 西尾 勝久; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; et al.
Journal of Nuclear Science and Technology, 60(4), p.435 - 449, 2023/04
被引用回数:4 パーセンタイル:56.38(Nuclear Science & Technology)加速器駆動核変換システム(ADS)の研究開発及び京都大学臨界実験装置(KUCA)におけるADS未臨界炉物理の基礎研究を目的として、固定磁場強収束(FFAG)加速器を用いて107MeV陽子による鉄、鉛及びビスマス標的に対する二重微分中性子収量(TTNY)を測定した。TTNYは8個の中性子検出器(各検出器は小型のNE213液体有機シンチレータと光電子増倍管より構成される)からなる中性子検出器システムを用いて飛行時間法により得られたものである。測定で得られたTTNYを、粒子・重イオン輸送コードシステム(PHITS)に組み込まれたモンテカルロ法に基づく核破砕反応モデル(INCL4.6/GEM, Bertini/GEM, JQMD/GEM, JQMD/SMM/GEM)及び評価済み高エネルギー核データライブラリ(JENDL-4.0/HE)による計算結果と比較した。JENDL-4.0/HEを含む比較対象のモデルは、検出器角度5度における高エネルギーピークを再現しないなどの特徴的な不一致が見られた。測定で得られたTTNYとPHITSによって評価した20MeV以下のエネルギー及び角度積分中性子収率を比較した結果、INCL4.6/GEMがKUCAにおけるADS炉物理実験のモンテカルロ輸送シミュレーションに適していることが示された。
Pedersen, L. G.*; Sahin, E.*; Grgen, A.*; Bello Garrote, F. L.*; 角田 佑介*; 大塚 孝治*; 新倉 潤*; Orlandi, R.; 他59名*
Physical Review C, 107(4), p.044301_1 - 044301_10, 2023/04
被引用回数:1 パーセンタイル:30.87(Physics, Nuclear)Nuclei in the vicinity of Ni (
=28,
=50) are important benchmarks to study the evolution of shell structure far from stability. Excited states in
Cu were observed for the first time following the
-decay of
Ni, which was produced by in-flight fission of
U. Using
-ray coincidences, a level scheme comprising eight excited states was built. Using the observed
feeding and the
-decay properties of the excited states, spin was tentatively assigned to 5 new states. In addition to the
-decaying states, an isomeric state with a lifetime of 3.8(4) ms was found to decay by internal conversion. By comparing the results with large scale shell model calculations, quantitative information about the proton-neutron interaction outside the doubly magic
Ni core was obtained.
岩元 大樹; 明午 伸一郎; 中野 敬太*; 佐藤 大樹; 岩元 洋介; 杉原 健太*; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; 八島 浩*; et al.
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.404 - 409, 2023/01
加速器駆動核変換システム(ADS)の研究開発に資するため、固定磁場強収束(FFAG)加速器を用い、核データを取得する実験的研究プログラムを開始した。ADSの核設計及び京都大学臨界集合体実験装置(KUCA)における未臨界実験体系の解析で重要となる、鉛及びビスマスの陽子入射中性子収量及び核分裂に関する核データを対象とした。中性子の飛行時間(TOF)測定で要求される短パルスビームの技術開発を行い、その要求値となるビーム幅10ns以下を達成するとともに、107MeV陽子入射による厚い標的中性子収量TTNY及び中性子生成二重微分断面積DDXをTOF法により測定した。TTNY及びDDXの測定には、小型シンチレータと光電子増倍管から構成される中性子検出器を用いた。測定で得られた結果をADSの核設計で用いられるPHITSによる解析値と比較した。さらに、マイクロチャンネルプレート(MCP)と多芯線比例計数管(MWPC)を組み合わせにより、107MeV陽子入射のPb核分裂反応から生成される核分裂片の質量数分布を測定した。本プログラムの最終年度となる令和4年度は、
Biに対する核分裂片の質量数分布と核分裂で生じる核分裂中性子の測定を実施するとともに、
Np核分裂計数管を用いて、陽子と標的との核反応で形成される中性子場の測定を実施する予定である。
Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; 浅井 雅人; 塚田 和明; 佐藤 哲也; 伊藤 由太; 洲嵜 ふみ; 永目 諭一郎*; et al.
Physical Review C, 106(6), p.064301_1 - 064301_11, 2022/12
被引用回数:4 パーセンタイル:56.09(Physics, Nuclear)The nuclear structure of Cf produced by the
O+
Cf multinucleon transfer reaction was investigated using
-ray spectroscopy. Analysis of the
-ray spectrum of
Cf revealed the presence of multiple long-lived (isomeric) excited states at low excitation energies. The energies and half-lives of the isomers contain information on the proton and neutron orbits in the heavy-element region and the deformation of atomic nuclei, and are important data to predict the properties of nuclei in the "island of stability".
岩元 大樹; 中野 敬太; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 石 禎浩*; 上杉 智教*; 栗山 靖敏*; 八島 浩*; 西尾 勝久; et al.
JAEA-Conf 2022-001, p.129 - 133, 2022/11
加速器駆動システム(ADS)の核特性予測精度の向上と京都大学臨界集合体実験装置(KUCA)におけるADS炉物理実験で用いる中性子源情報の取得を目的として、京都大学の固定磁場強集束(FFAG)加速器を用いた核データ測定実験プログラムを開始した。このプログラムの一環として、鉄に対する陽子入射二重微分中性子収量(TTNY)及び断面積(DDX)を測定した。測定では、真空チェンバ内に設置された鉄標的に107MeVの陽子ビームを照射し、核反応によって標的から発生した粒子の信号を、小型の中性子検出器を用いて検出した。検出信号とFFAGキッカー電磁石の信号の時間差から飛行時間(TOF)を求め、ガンマ線の事象を波形弁別法によって除去して中性子事象をカウントすることで中性子のTOFスペクトルを求めた。得られた中性子のTOFスペクトルから、相対論的運動学により鉄標的に対するTTNY及びDDXを求めた。
田中 翔也*; 廣瀬 健太郎; 西尾 勝久; Kean, K. R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; 有友 嘉浩*
Physical Review C, 105(2), p.L021602_1 - L021602_5, 2022/02
被引用回数:3 パーセンタイル:34.70(Physics, Nuclear)The angular momentum of a primary excited compound nucleus produced in multinucleon transfer reaction is an important quantity to evaluate cross sections to synthesize neutron-rich heavy element nuclei as well as for surrogate reaction studies. The mechanism is, however, not enough understood due to the lack of detailed experimental data. In the present study, we determined the angular momentum of primary excited nuclei, Np,
Pu, and
Am, produced in the multi-nucleon transfer channels of the
O +
Np reaction. With this aim, angular distributions of fission fragments with respect to the axis perpendicular to the reaction plane were measured for each compound nucleus. The distributions show an anisotropy exhibiting an enhanced yield on the reaction plane. They are well reproduced by a saddle point model, from which the average angular momentum is derived in the model framework. The angular momentum increases with the compound-nucleus mass, thus the number of nucleons exchanged, but shows a saturating trend toward heavier compound nuclei. These results are the first ones to point to the dependence of the angular momentum on the transfer channels.
Gerst, R.-B.*; Blazhev, A.*; Moschner, K.*; Doornenbal, P.*; Obertelli, A.*; Orlandi, R.; 他62名*
Physical Review C, 105(2), p.024302_1 - 024302_11, 2022/02
被引用回数:7 パーセンタイル:69.74(Physics, Nuclear)The neutron rich krypton isotopes Kr (
=36,
=58,59,60 respectively) were investigated at the Radioactive Isotope Beam Facility Facility (RIBF) at RIKEN. The nuclei of interest were produced in nuclear reactions induced by radioactive Kr and Rb beams, prduced via in-flight fission of
U, impinging onto the liquid hydrogen target MINOS. The main reactions occurring were (p,pn), (p,p') and (p,2p). The isotopes of interest were separated in the fragment separator BigRIPS, and their
rays detected using the DALI2
-ray spectrometer. The
Kr provide insights onto the sudden onset of deformation occurring in Zr and Mo isotopes at
=60, which is also associated with shape coexistence. In this experiment the level scheme of these isotopes could be extended, and new yrast and non-yrast states were identified. The results were compared with predictions of the "beyond-mean-field" model and the IBM model, and indications of prolate-oblate shape coexistence at
=60 in the Kr isotopes was found.
Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.
Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10
被引用回数:5 パーセンタイル:24.15(Astronomy & Astrophysics)The long-lived Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction
Fe(n,
)
Fe on
Fe (half-life=44.5 days) is the key reaction for the production of
Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1
-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the
Fe(n,
)
Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5
3.5 mb at
= 30 keV and 13.4
1.7 mb at
= 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of
Fe from the
Fe(n,
)
Fe rate are at most 25
. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of
Fe.
Tonev, D.*; De Angelis, G.*; Deloncle, I.*; Orlandi, R.; 他27名*
Physics Letters B, 821, p.136603_1 - 136603_6, 2021/10
被引用回数:5 パーセンタイル:53.57(Astronomy & Astrophysics)The mirror nuclei P and
S, produced via the
Ne+
C reaction at 33 MeV, were studied at Legnaro Laboratory using the EUCLIDES Si array coupled with the GASP Ge array. The observed B(E1) strengths of mirror E1 transitions, provide strong evidence for breaking of isospin symmetry in the A=31 mass region. The new finding are supported and explained by state-of-the-art beyond-mean-field calculations including 2- and 3-body forces. According to these findings, the breaking of isospin symmetry originate from violation of charge symmetry in the 2- and 3-body parts of the Coulomb potential.
Moon, B.*; Jungclaus, A.*; Nadja, H.*; Gargano, A.*; Lozeva, R.*; Moon, C.-B.*; Orlandi, R.; 他66名*
Physical Review C, 103(3), p.034320_1 - 034320_15, 2021/03
被引用回数:9 パーセンタイル:73.68(Physics, Nuclear)At RIKEN RIBF facility, the beta decay of Sb and
Sb were studied and several new excited states were assigned to the level schemes of
Te and
Te. The structure of these Te isotopes deduced from the level scheme is compared with state-of-the-art shell-model calculations using different effective interactions. The comparison with calculations permits to determine the spectroscopic factors and deformation of these isotopes close to doubly magic
Sn.
岩佐 直仁*; 石川 竣喜*; 久保野 茂*; 榊原 昂浩*; 小湊 和也*; 西尾 勝久; 松田 誠; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; et al.
Physical Review C, 103(1), p.015801_1 - 015801_5, 2021/01
被引用回数:1 パーセンタイル:14.30(Physics, Nuclear)The Be(
He,
)
Be(
)
Li reaction was studied at
(
He)=30 MeV to deduce the branching ratios of
of resonant state at 18.91 - 20.1 MeV in
Be, which are necessary to extract the
Be(
,
)
Li
reaction rate relevant to the
Be destruction in the big bang nucleosynthesis, from the
Li(
,
)
Be reaction cross section. The decay protons from
Be
to the ground and first excited states in
Li were well-separately measured. The
ratio of the 19.235-MeV state was deduced to be 3.4
1.9%. The 19.86- and 20.1-MeV states were found to decay dominantly into the first excited and ground states of
Li, respectively.
Vermeulen, M. J.; 西尾 勝久; 廣瀬 健太郎; Kean, K. R.; 牧井 宏之; Orlandi, R.; 塚田 和明; Tsekhanovich, I.*; Andreyev, A. N.; 石崎 翔馬*; et al.
Physical Review C, 102(5), p.054610_1 - 054610_11, 2020/11
被引用回数:6 パーセンタイル:51.35(Physics, Nuclear)Fission fragment mass distributions for 23 nuclei (U,
Np,
Pu,
Am,
Cm, and
Bk) were measured using the multi-nucleon transfer approach in the reaction of
O+
Np, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low energy fission of
Np,
Pu, and
Cm is reported for the first time. The experimental data for all the studied nuclei were compared to the Langevin calculations. The calculation which takes into account the effects of multi-chance fission well reproduced the peak-to-valley ratio and mass-asymmetric peak positions of the distributions. The angular momenta given to the fissioning nucleus is also discussed.
Bello Garrote, F. L.*; Sahin, E.*; 角田 佑介*; 大塚 孝治*; Grgen, A.*; Orlandi, R.; 他61名*
Physical Review C, 102(3), p.034314_1 - 034314_13, 2020/09
被引用回数:4 パーセンタイル:38.05(Physics, Nuclear)Detailed spectroscopy of neutron-rich odd- Cu isotopes is of great importance for studying the shell evolution in the region of
Ni. Excited states in
Cu were populated in the
decay of
Ni isotopes, which were produced by the in-flight fission at RIBF, RIKEN. The
Ni isotopes were separated, identified, and implanted in a highly segmented Si detector array for the detection of the
-decay electrons, while the delayed
rays were detected by an array of HPGe cluster detectors. A level scheme of
Cu was built up to
4 MeV, from which the location of the two previously known low-lying isomeric states was clarified. The level structure below 2 MeV was interpreted based on the results of the shell-model calculations and the systematics of odd-
Cu isotopes, revealing the evolution of single-particle states in this region.