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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
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.
永井 泰樹*; 木下 充隆*; 井頭 政之*; 延原 由利子*; 牧井 宏之; 三島 賢二*; 嶋 達志*; Mengoni, A.*
Physical Review C, 102(4), p.044616_1 - 044616_8, 2020/10
被引用回数:0We measured the total capture cross section of the O
O reaction, as well as partial cross sections leading to the ground (
and first excited (
states in
O. The measurement was carried out at average neutron energies of 157, 349, 398, 427, 468, 498, and 556 keV by using pulsed neutrons produced via the
Li
Be reaction and a
-ray detection system based on an anti-Compton NaI(Tl) spectrometer. We observed the interference effect between the
resonance state at 4554 keV of
O, corresponding to a neutron energy of 411 keV in the center-of-mass system, and a non-resonant contribution in the capture process. The measured partial cross sections are in good agreement with theoretical calculations obtained taking into account the interference between the
resonance and a non-resonant p-wave direct radiative capture contribution. Using the present results, together with our previous measurement, we derived the Maxwellian-averaged capture cross sections (MACS) for thermal energies between kT = 5 and 100 keV, key quantities for
process nucleosynthesis studies in massive stars.
Dupont, E.*; Astier, A.*; Petrache, C. M.*; Lv, B. F.*; Deloncle, I.*; Kiener, J.*; Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; et al.
Physical Review C, 101(1), p.014309_1 - 014309_6, 2020/01
被引用回数:0 パーセンタイル:100(Physics, Nuclear)Five new 2 levels and one new 3
level were established in
Po. The states were populated via the
Pb(
C,
Be) two-proton reaction experiment, performed at the JAEA Tandem in Tokai. A setup combining Ge, LaBr
, and Si telescopes was used to detect in-beam
-rays and ejectile residues. Two-proton configurations were assigned to all new states. All assignments are strongly supported by shell-model calculations.
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.; 小川 達彦; Soldner, T.*; K
ster, U.*; Pollitt, A.*; Hambsch, F.-J.*; et al.
Physical Review C, 100(4), p.044610_1 - 044610_7, 2019/10
被引用回数:2 パーセンタイル:63.02(Physics, Nuclear)The prompt fission -ray energy spectrum for cold-neutron induced fission of
U was measured in the energy range
= 0.8 - 20,MeV, by gaining a factor of about 10
in statistics compared to the measurements performed so far. The spectrum exhibits local bump structures at
4,MeV and
6,MeV, and also a broad one at
15,MeV. In order to understand the origins of these bumps, the
-ray spectra were calculated using a statistical Hauser-Feshbach model, taking into account the de-excitation of all the possible primary fission fragments. It is shown that the bump at
4,MeV is created by the transitions between the discrete levels in the fragments around
Sn, and the bump at
6,MeV mostly comes from the complementary light fragments. It is also indicated that a limited number of nuclides, which have high-spin states at low excitation energies, can contribute to the bump structure around
15,MeV, induced by the transition feeding into the low-lying high-spin states.
Xiao, Y.*; Go, S.*; Grzywacz, R.*; Orlandi, R.; Andreyev, A. N.; 浅井 雅人; Bentley, M. A.*; de Angelis, G.*; Gross, C. J.*; Hausladen, P.*; et al.
Physical Review C, 100(3), p.034315_1 - 034315_8, 2019/09
被引用回数:4 パーセンタイル:18.92(Physics, Nuclear)A search for super-allowed decay of N=Z nuclei
Te and
Xe was carried out using a novel recoil-decay scintillator detector at the tandem accelerator facility at Japan Atomic Energy Agency. Inorganic crystal scintillation material of YAP:Ce (Yttrium Aluminium Perovskite) coupled to position-sensitive photo-multiplier tube (PSPMT) was implemented for the first time in a radioactive decay experiment. Residues from the fusion-evaporation reaction
Ni+
Fe
Xe
were separated by the JAEA Recoil Mass Separator (RMS) and implanted into the YAP:Ce crystal.
decays of neutron-deficient tellurium isotopes were identified and proton-emission of
I was observed. No conclusive evidence was found for the decay chain
Xe
Te
Sn within 3 days experiment. The cross section limit of 130 pb was obtained for production of two events of
Xe, about an order of magnitude below the expectation based on earlier cross section measurements and HIVAP calculations.
Kean, K. R.; 西尾 勝久; 廣瀬 健太郎; Vermeulen, M. J.; 牧井 宏之; Orlandi, R.; 塚田 和明; Andreyev, A. N.; Tsekhanovich, I.*; 千葉 敏*
Physical Review C, 100(1), p.014611_1 - 014611_6, 2019/07
被引用回数:0 パーセンタイル:100(Physics, Nuclear)The validity of the multinucleon transfer (MNT) approach for deduction of fission barrier heights was investigated in an experiment carried out at the JAEA tandem accelerator facility. By using the O+
Np reaction, fission barrier heights were inferred from fission probabilities of the nuclei
Np and
Pu produced in the
and
transfer channels, respectively. The deduced values of fission barriers agree well with the literature data, thus demonstrating the potential of the MNT reactions for obtaining fission-barrier data for nuclei not accessible for fission studies via neutron- or light charged particle-induced reactions.
Tsekhanovich, I.*; Andreyev, A. N.; 西尾 勝久; Denis-Petit, D.*; 廣瀬 健太郎; 牧井 宏之; Matheson, Z.*; 森本 幸司*; 森田 浩介*; Nazarewicz, W.*; et al.
Physics Letters B, 790, p.583 - 588, 2019/03
被引用回数:10 パーセンタイル:6.44(Astronomy & Astrophysics)Fragment mass distributions from fission of the excited compound nucleus Pt have been deduced from the measured fragment velocities. The
Pt nucleus was created at the JAEA tandem facility in a complete fusion reaction
Ar+
Nd, at beam energies of 155, 170 and 180 MeV. The data are indicative of a mixture of the mass-asymmetric and mass-symmetric fission modes associated with higher and lower total kinetic energies of the fragments, respectively. The measured fragment yields are dominated by asymmetric mass splits, with the symmetric mode contributing at the level of
1/3. This constitutes the first observation of a multimodal fission in the sub-lead region. Most probable experimental fragment-mass split of the asymmetric mode,
/
79/99, is well reproduced by nuclear density functional theory using the UNEDF1-HFB and D1S potentials. The symmetric mode is associated by theory with very elongated fission fragments, which is consistent with the observed total kinetic energy/fragment mass correlation.
佐藤 哲也; 浅井 雅人; Borschevsky, A.*; Beerwerth, R.*; 金谷 佑亮*; 牧井 宏之; 水飼 秋菜*; 永目 諭一郎; 長 明彦; 豊嶋 厚史; et al.
Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11
被引用回数:13 パーセンタイル:26.3(Chemistry, Multidisciplinary)第一イオン化エネルギー(IP)は、原子の価電子軌道に関する情報を与える。99番元素アインスタイニウムよりも重いアクチノイドのIP
は、一度に一つの原子しか扱うことのできない実験の難しさから、これまでに実験的に測定された例はなかった。我々は表面電離法を応用した新しい測定手法により、103番元素ローレンシウム(Lr)のIP
測定に成功し、Lrが弱く束縛された最外殻電子をもつことを強く示唆する結果を得た。一方、Lrとは対象的に、102番元素ノーベリウムは充填された5f軌道および7s軌道をもつために、アクチノイド中最高のIP
をもつと考えられている。表面電離法によるIP
決定法をNoおよび100番元素フェルミウム, 101番元素メンデレビウムに適用することにより求められた各IP
から、5f軌道への電子の充填に伴ってIP
が単調に増加し、Noで最も大きくなることを確かめることができた。このことから、f軌道に電子が充填され、アクチノイド系列がLrで終わることを実験的に確かめた。
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.*; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; A
che, M.*; Astier, A.*; et al.
Nuclear Instruments and Methods in Physics Research A, 906, p.88 - 96, 2018/10
被引用回数:3 パーセンタイル:40.19(Instruments & Instrumentation)中性子誘起核分裂における即発高エネルギー線を観測するための新しい測定システムの開発を行った。測定システムは核分裂片を観測するための多芯線比例計数管と
線測定用のLaBr
(Ce)シンチレータから構成される。開発したシステムを仏国ラウエ・ランジュバン研究所にある高中性子束炉のPF1Bコースに設置して、
U中性子誘起核分裂における即発
線を行った。測定ではエネルギー最大20MeVまでの
線スペクトルの観測に成功し、
U中性子誘起核分裂において非常に高いエネルギーの
線が放出されていることを確認した。
西中 一朗*; 横山 明彦*; 鷲山 幸信*; 牧井 宏之; 橋本 和幸*
Journal of Radioanalytical and Nuclear Chemistry, 314(3), p.1947 - 1965, 2017/12
被引用回数:2 パーセンタイル:64.19(Chemistry, Analytical)Li +
Sn反応により生成されるI, Te, Sn同位体の生成断面積を入射エネルギー24-59MeVの領域で測定した。得られた生成断面積のエネルギー依存性を統計模型計算の結果と比較することにより、各同位体の生成機構と崩壊様式の観点から完全・不完全融合反応の生成断面積への寄与を議論した。また、医学的に有用な
Iの生成という観点から、様々なSn同位体と
Liビームの組み合わせにより、
I同位体がどの程度生成されるかを計算し、
Li以外をビームとして用いた場合との比較を行った。
廣瀬 健太郎; 西尾 勝久; 田中 翔也*; Lguillon, R.*; 牧井 宏之; 西中 一朗*; Orlandi, R.; 塚田 和明; Smallcombe, J.*; Vermeulen, M. J.; et al.
Physical Review Letters, 119(22), p.222501_1 - 222501_6, 2017/12
被引用回数:26 パーセンタイル:8.29(Physics, Multidisciplinary)JAEAタンデム加速器施設で行ったO+
U反応における多核子移行チャンネルを用いた実験により、
U,
Np、および
Puの核分裂質量分布を励起エネルギー10
60MeVにおいて測定した。これらのうち、
U,
Npのデータは本実験により初めて観測された。原子核の殻効果の減衰によって対称分裂すると予想されていた高励起エネルギーにおいても、質量分布が非対称を示すことがわかった。搖動散逸定理に基づく動力学モデル計算との比較から、この振る舞いはマルチチャンス核分裂によるものであることを明らかにした。
西尾 勝久; 廣瀬 健太郎; Vermeulen, M. J.; 牧井 宏之; Orlandi, R.; 塚田 和明; 浅井 雅人; 豊嶋 厚史; 佐藤 哲也; 永目 諭一郎; et al.
EPJ Web of Conferences, 163, p.00041_1 - 00041_6, 2017/11
被引用回数:1 パーセンタイル:25.96We are promoting a study of fission using multi-nucleon transfer (MNT) reactions, where excited states in neutron-rich actinide nuclei, which cannot be accessed by particle capture and/or fusion reactions, are populated. Also, the excited states in the fissioning nucleus are widely populated by the MNT reactions, from which effects of excitation energy on fission properties can be investigated. Experiments were carried out at the JAEA tandem facility in Tokai, Japan. We studied reactions using the O beam and several actinide target nuclei such as
Th,
U,
Np,
Cm. Ejectile nucleus was identified by a silicon
E-E telescope to identify transfer channel and hence the compound nucleus. Fission fragments were detected by multi-wire proportional counters, and fission fragment mass distributions (FFMDs) were measured for each isotope. Measured FFMDs are reproduced by a calculation based on the fluctuation-dissipation model, and importance of multi-chance fission concept is investigated. Fission fragment angular distribution relative to the recoil direction suggested the increase of the spin of the fissioning nucleus with the number of transferred nucleons.
西尾 勝久; 廣瀬 健太郎; Lguillon, R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; 田中 翔也*; et al.
Proceedings of 6th International Conference on Fission and Properties of Neutron-rich Nuclei (ICFN-6), p.590 - 597, 2017/11
We are promoting a fission study using multi-nucleon transfer reactions, where excited states in neutron-rich actinide nuclei, which cannot be accessed by particle capture and/or fusion reactions, are populated. This allows us to study fission in the new region of chart of nuclei. Also, the excited states in the fissioning nucleus are widely populated in the reactions, thus the effects of excitation energy on fission can be investigated. Experiments were carried out at the JAEA tandem facility in Tokai, Japan. We studied reactions using the O beam (
9MeV/u) and several actinide target nuclei such as
Th,
U,
Np,
Cm. Ejectile nuclei and thus the transfer channels were identified by a newly developed silicon
E-E detectors. The produced nuclei in one experiment reached more than fifteen. Fission fragment mass distributions (FFMDs) were measured for each isotopes. Measured FFMDs are reproduced by a calculation based on the fluctuation-dissipation model (Langevin-type calculation), where effects of multi-chance fission were included. We also started to measure the prompt neutrons accompanied by fission.
Yan, S. Q.*; Li, Z. H.*; Wang, Y. B.*; 西尾 勝久; Lugaro, M.*; Karakas, A. I.*; 牧井 宏之; Mohr, P.*; Su, J.*; Li, Y. J.*; et al.
Astrophysical Journal, 848(2), p.98_1 - 98_8, 2017/10
被引用回数:0 パーセンタイル:100(Astronomy & Astrophysics)The Zr(
)
Zr reaction cross section is crucial in the modelling of
-process nucleosynthesis in asymptotic giant branch stars because it controls the operation of the branching point at the unstable
Zr and the subsequent production of
Zr. We have carried out the measurement of the
Zr(
O,
O) and
Zr(
O,
O) reactions and obtained the
-decay probability ratio of
Zr
and
Zr
to determine the
Zr(
)
Zr reaction cross sections with the surrogate ratio method. We tested our deduced maxwellian-averaged cross section in stellar models with masses between 2 and 6
and metallicities 0.014 and 0.03. The largest changes - up 80 % variations in
Zr - are seen in the models of 3-4
, where the
Ne neutron source is mildly activated. The new rate can still provide a match to data from meteoritic stardust silicon carbide grains, provided the maximum mass of the parent stars is below 4
, for a metallicity of 0.03.
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; Astier, A.*; Pollitt, A.*; et al.
EPJ Web of Conferences, 146, p.04036_1 - 04036_4, 2017/09
被引用回数:2 パーセンタイル:10.14核分裂に伴い放出される即発線スペクトルの測定は高励起状態にある中性子過剰な核分裂片の脱励起過程を理解する上で重要であると同時に、革新的原子炉の設計といった応用分野においても重要である。これまで
Cfの自発核分裂においては、核分裂片の巨大共鳴振動が励起されていることを示唆する、8MeVから20MeVにおいて膨らみを持つ高エネルギー
線が観測されていることが知られている。巨大共鳴振動励起の起源を理解するためには
Cfの自発核分裂以外で即発
線スペクトルを測定する必要があるが、中性子誘起核分裂においては最近の測定においても9MeV程度までしか観測されていない。我々は
U(n,f)においても20MeVまでの即発
線スペクトルの観測を目的とした測定を仏国ラウエ・ランジュバン研究所にある高中性子束炉の大強度冷中性子ビームを用いて行った。発表では測定で得られた結果について報告する。
西尾 勝久; 廣瀬 健太郎; Lguillon, R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; 田中 翔也*; et al.
EPJ Web of Conferences, 146, p.04009_1 - 04009_6, 2017/09
被引用回数:2 パーセンタイル:10.14The objective of this work is to extend fission data for actinide nuclei not investigated so far in order to understand the fission mechanism, especially for neutron-rich nuclei. Multi-nucleon transfer reactions were used to populate the compound nuclei which cannot be accessed by particle capture or fusion reactions. The experiment was carried out at the tandem facility of Japan Atomic Energy Agency. In the multi-nucleon transfer reactions using O beam, a wide variety of nuclei around a target nucleus was produced. By identifying transfer channels, fission data of nuclei more than fifteen compound nuclei were generated in one experiment. Another feature of transfer reaction is that the excitation energies of a compound nucleus can be populated continuously from the ground state up to several tens MeV, allowing us to study the excitation energy dependence of fission properties. From the excitation function of fission probabilities, fission-barrier heights of neutron-rich actinide nuclei were obtained. Experiments were carried out in the reactions of
O +
U,
Th,
Cm,
Np. The obtained fission fragment mass distributions were reproduced by a model calculation based on a fluctuation dissipation model.
廣瀬 健太郎; 西尾 勝久; 牧井 宏之; 西中 一朗*; 太田 周也*; 永山 達郎*; 田村 信行*; 後藤 真一*; Andreyev, A.; Vermeulen, M. J.; et al.
Nuclear Instruments and Methods in Physics Research A, 856, p.133 - 138, 2017/06
被引用回数:3 パーセンタイル:50.46(Instruments & Instrumentation)Fission and capture reactions were simultaneously measured in the neutron-induced reactions of Am at J-PARC. Data were taken with the TOF method in
= 0.1
20 eV. The fission events were observed by detecting prompt fission neutrons using liquid organic scintillators. The capture reaction was measured by detecting
rays from the compound nuclei using the same detectors, where the prompt fission neutrons and capture
rays were separated by a pulse shape analysis. The cross sections were obtained by normalizing the relative yields at the first resonance to evaluations or other experimental data. The ratio of the fission to capture cross sections at each resonance is compared with those from an evaluated nuclear data library and other experimental data. Some differences were found between the present values and the library/literature values at several resonances.
Lguillon, R.; 西尾 勝久; 廣瀬 健太郎; 牧井 宏之; 西中 一朗*; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; et al.
Physics Letters B, 761, p.125 - 130, 2016/10
被引用回数:27 パーセンタイル:6.5(Astronomy & Astrophysics)It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the O +
Th reaction are used to study fission of fourteen nuclei
Th,
Pa, and
U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of
Th and
Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.
Yan, S. Q.*; Li, Z. H.*; Wang, Y. B.*; 西尾 勝久; 牧井 宏之; Su, J.*; Li, Y. J.*; 西中 一朗; 廣瀬 健太郎; Han, Y. L.*; et al.
Physical Review C, 94(1), p.015804_1 - 015804_5, 2016/07
被引用回数:3 パーセンタイル:63.27(Physics, Nuclear)The relative -decay probability ratios of the neutron resonance states in
Zr and
Zr populated via two neutron transfer reactions,
Zr(
O,
O)
Zr and
Zr(
O,
O)
Zr, have been measured to test the validity of the surrogate ratio method (SRM) in determining the (n,
) reaction cross section. The cross sections of the
Zr(n,
)
Zr reaction are derived from the experimentally obtained ratios and the cross sections of the
Zr(n,
)
Zr reaction in the equivalent neutron energy range of
= 0 - 8 MeV. The deduced cross sections of
Zr(n,
)
Zr reaction agree with the directly measured ones in the low-energy region, and with the evaluated ENDF/B-VII.1 data at higher energies of
3 MeV. The agreement supports the concept of the SRM method to indirectly determine the (n,
) reaction cross sections.
石山 博恒*; Jeong, S.-C.*; 渡辺 裕*; 平山 賀一*; 今井 伸明*; Jung, H. S.*; 宮武 宇也*; 小柳津 充広*; 長 明彦; 乙川 義憲; et al.
Nuclear Instruments and Methods in Physics Research B, 376, p.379 - 381, 2016/06
被引用回数:6 パーセンタイル:38.13(Instruments & Instrumentation)We have developed an in situ and nanoscale Li diffusion measurement method in Li battery materials using an -emitting radioactive
Li tracer. In this method, while implanting a low-energy (8 keV)
Li beam, the
particles emitted at a small angle (10
) relative to the sample surface were detected as a function of time. Measurement for Li diffusion coefficients in a spinel phase LiMn
O
(LMO) thin film has been started, which is used as an electrode in a Li ion secondary battery. An obvious Li diffusion effect in LMO was observed at the sample temperature of 623 K, and the further measurement is underway.