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論文

Angular momentum transfer in multinucleon transfer channels of $$^{18}$$O + $$^{237}$$Np

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

https://doi.org/10.1103/PhysRevC.105.L021602
 被引用回数：2 パーセンタイル：30.99(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, $$^{237,238,239}$$Np, $$^{238,239,240}$$Pu, and $$^{239,240,241}$$Am, produced in the multi-nucleon transfer channels of the $$^{18}$$O + $$^{237}$$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.

論文

Measurement of fission-fragment mass distributions in the multinucleon transfer channels of the $$^{18}$$O+$$^{237}$$Np reaction

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

https://doi.org/10.1103/PhysRevC.102.054610
 被引用回数：5 パーセンタイル：51.79(Physics, Nuclear)

Fission fragment mass distributions for 23 nuclei ($$^{234-237}$$U, $$^{236-239}$$Np, $$^{238-241}$$Pu, $$^{240-243}$$Am, $$^{242-245}$$Cm, and $$^{244-246}$$Bk) were measured using the multi-nucleon transfer approach in the reaction of $$^{18}$$O+$$^{237}$$Np, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low energy fission of $$^{236}$$Np, $$^{238}$$Pu, and $$^{245}$$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.

論文

Validation of the multinucleon transfer method for the determination of the fission barrier height

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

https://doi.org/10.1103/PhysRevC.100.014611
 被引用回数：3 パーセンタイル：32.18(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 $$^{18}$$O+$$^{237}$$Np reaction, fission barrier heights were inferred from fission probabilities of the nuclei $$^{239}$$Np and $$^{239,240}$$Pu produced in the $$2n$$ and $$pn/p2n$$ 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.

論文

Nuclear fission; A Review of experimental advances and phenomenology

Andreyev, A. N.; 西尾 勝久; Schmidt, K.-H.*

Reports on Progress in Physics, 81(1), p.016301_1 - 016301_61, 2018/01

https://doi.org/10.1088/1361-6633/aa82eb
 被引用回数：127 パーセンタイル：91.67(Physics, Multidisciplinary)

In the last two decades, through technological, experimental and theoretical advances, the situation in experimental fission studies has changed dramatically. With the use of advanced production and detection techniques both much more detailed and precise information can now be obtained for the traditional regions of fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies. This work first of all reviews the recent developments in experimental fission techniques, in particular the resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams. The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of the other fission observables, such as prompt neutron and $$gamma$$-ray emission will also be reviewed. The review will conclude with the discussion of the new experimental fission facilities which are presently being brought into operation, along with promising "next-generation" fission approaches, which might become available within the next decade.

論文

核データ研究の最前線; たゆまざる真値の追及、そして新たなニーズへ応える為に,3; 核分裂データの最前線; 実験と理論

西尾 勝久; 千葉 敏*

日本原子力学会誌ATOMO$$Sigma$$, 59(12), p.717 - 721, 2017/12

核分裂は原子力エネルギー利用の基礎となる現象であるが、その複雑さのため質および量ともに限られた実験データを現象論によって記述し、核データとして利用されるにとどまっていた。近年、新規の実験技術確立に加え高性能計算機を活かした理論計算に大きな進展があったので、最新成果を見ながら議論する。

論文

Role of multichance fission in the description of fission-fragment mass distributions at high energies

廣瀬 健太郎; 西尾 勝久; 田中 翔也*; L$'e$guillon, 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

https://doi.org/10.1103/PhysRevLett.119.222501
 被引用回数：50 パーセンタイル：91.17(Physics, Multidisciplinary)

JAEAタンデム加速器施設で行った$$^{18}$$O+$$^{238}$$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、$$^{237-240}$$U, $$^{239-242}$$Np、および$$^{241-244}$$Puの核分裂質量分布を励起エネルギー10$$sim$$60MeVにおいて測定した。これらのうち、$$^{240}$$U, $$^{240,241,242}$$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。

論文

Study of fission using multi-nucleon transfer reactions

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

https://doi.org/10.1051/epjconf/201716300041
 被引用回数：1 パーセンタイル：61.03(Nuclear Science & Technology)

We 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 $$^{18}$$O beam and several actinide target nuclei such as $$^{232}$$Th, $$^{238}$$U, $$^{237}$$Np, $$^{248}$$Cm. Ejectile nucleus was identified by a silicon $$Delta$$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.

論文

Experimental fission study using multi-nucleon transfer reactions

西尾 勝久; 廣瀬 健太郎; L$'e$guillon, 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

https://doi.org/10.1051/epjconf/201714604009
 被引用回数：3 パーセンタイル：86.09(Nuclear Science & Technology)

The 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 $$^{18}$$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 $$^{18}$$O + $$^{238}$$U, $$^{232}$$Th, $$^{248}$$Cm, $$^{237}$$Np. The obtained fission fragment mass distributions were reproduced by a model calculation based on a fluctuation dissipation model.

論文

One-neutron pickup into $$^{49}$$Ca; Bound neutron $$g_{9/2}$$ spectroscopic strength at $$N$$ = 29

Gade, A.*; Tostevin, J. A.*; Bader, V. M.*; Baugher, T.*; Bazin, D.*; Berryman, J. S.*; Brown, B. A.*; Hartley, D. J.*; Lunderberg, E.*; Recchia, F.*; et al.

Physical Review C, 93(3), p.031601_1 - 031601_5, 2016/03

AA2015-0859.pdf:0.32MB

https://doi.org/10.1103/PhysRevC.93.031601
 被引用回数：15 パーセンタイル：72.2(Physics, Nuclear)

中性子過剰カルシウム同位体では、最近、中性子数34の魔法数が発見されるなど、その殻構造が大きな注目を集めている。中性子の$$pf$$軌道の上には$$g_{9/2}$$軌道があるはずであるが、これまでその位置に関する明確な実験データが存在しなかった。ミシガン州立大のサイクロトロン施設を用いて行われた本研究では、$$^{48}$$Caビームを$$^{12}$$Cにあてる重イオン反応と脱励起$$gamma$$線測定を組み合わせることによって、$$^{49}$$Caの4.018-MeV状態の分光学的因子を精度よく得ることに成功した。重イオン反応によって高角運動量状態の断面積を増大させ、脱励起$$gamma$$線を測定することによって反応データだけでは分離できない$$f_{5/2}$$状態を分離することが可能になったためである。この実験によって、4.018-MeV状態は比較的大きな分光学的因子を持つことがわかり、殻模型計算の予言が確かめられた。

論文

Observation of new neutron-deficient isotopes with Z$$ge$$92 in multinucleon transfer reactions

Devaraja, H. M.*; Heinz, S.*; Beliuskina, O.*; Comas, V. F.*; Hofmann, S.*; Hornung, C.*; M$"u$nzenberg, G.*; 西尾 勝久; Ackermann, D.*; Gambhir, Y. K.*; et al.

Physics Letters B, 748, p.199 - 203, 2015/09

AA2015-0304.pdf:0.78MB

https://doi.org/10.1016/j.physletb.2015.07.006
 被引用回数：66 パーセンタイル：96.96(Astronomy & Astrophysics)

In deep inelastic multinucleon transfer reactions of $$^{48}$$Ca +$$^{248}$$Cm we observed about 100 residual nuclei with proton numbers between Z =82 and Z =100. Among them, there are five new neutron-deficient isotopes: $$^{216}$$U, $$^{219}$$Np, $$^{223}$$Am, $$^{229}$$Am and $$^{233}$$Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the $$alpha$$-decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

論文

In-beam $$gamma$$-ray spectroscopy of $$^{240}$$U using the ($$^{18}$$O,$$^{16}$$O) reaction

石井 哲朗; 重松 宗一郎; 浅井 雅人; 牧嶋 章泰*; 松田 誠; 金子 順一*; Hossain, I.*; 市川 進一; 河野 俊之*; 小川 雅生*

Physical Review C, 72(2), p.021301_1 - 021301_5, 2005/08

https://doi.org/10.1103/PhysRevC.72.021301
 被引用回数：20 パーセンタイル：76.34(Physics, Nuclear)

200MeVの$$^{18}$$Oビームと$$^{238}$$U標的による2核子移行反応により、中性子過剰核である$$^{240}$$Uの脱励起$$gamma$$線を測定した。Si $$Delta E$$-$$E$$検出器を用いて$$^{16}$$O粒子と同時計測することにより、$$^{240}$$Uの$$gamma$$線であることを同定した。$$^{16}$$O粒子の運動エネルギーの値を使い、$$^{240}$$Uの励起エネルギーを中性子分離エネルギー以下に限定した。$$^{240}$$Uにおいて、12$$^{+}$$状態までの基底バンドと9$$^{-}$$状態までの$$K^{pi}=0^{-}$$の8重極バンドを確立した。$$^{240}$$Uの8重極バンドヘッドは、$$^{236,238}$$Uのものよりも100keVほど高いエネルギーに位置する。このことは、U原子核の8重極相関が、中性子数144から146の領域で第2の極大値を持つことを示唆している。

報告書

高速炉用共分散データの整備(II)

柴田 恵一*; 長谷川 明*

PNC TJ9500 98-001, 102 Pages, 1998/03

PNC-TJ9500-98-001.pdf:5.87MB

高速炉の炉心解析で重要な核種について、評価済核データライブラリーJENDL-3.2の中性子核データの共分散を推定しファイル化した。対象となった核種は、10B、11B、55Mn、240Pu及び241Puである。共分散を推定した物理量は、断面積、分離・非分離共鳴パラメータ及び弾性散乱角度分布の1次のルジャンドル係数である。共分散の推定は、出来る限りJENDL-3.2のデータ評価法に基づいて行った。すなわち、評価値が実験値に基づいている場合は実験値の誤差、理論計算値に基づいている場合は理論計算値の誤差を算出した。評価結果は、ENDF-6フォーマットで整備した。

論文

Results of DWBA analysis for ($$^{6}$$Li,d) and ($$alpha$$,p) reaction in respect of primordial nuclear synthesis; Some related topics to nuclear astrophysics and cosmology

濱田 真悟; 安江 正治*; R.J.Peterson*

研究会報告集,短寿命核ビームの科学 93, 0, p.309 - 312, 1994/06

東大核研SFサイクロトロン施設での$$^{6}$$Liビームを用いて$$^{24}$$Mg($$^{6}$$Li,d)$$^{28}$$Si反応をE$$_{Li}$$=44,55,73MeVにわたって測定した。その逆反応である$$^{28}$$Si(d,$$^{6}$$Li)$$^{24}$$Mg反応を阪大RCNPにおいて偏極重陽子ビームを用いて測定した。またさらに$$^{7}$$Li原子核をターゲットして上記東大SFサイクロトロンよりの$$^{4}$$Heビームを用いて、$$^{7}$$Li($$alpha$$,p)$$^{10}$$Be反応を測定した。本研究会の発表はこれらの実験データを発表者のDWBA解析の結果とともに公表する予定である。この核反応のデータは最近注目の集まっている原始宇宙初期の元素合成過程を知るうえで価値がある。

論文

Cluster structures in $$^{10}$$Be from $$^{7}$$Li($$alpha$$,p)$$^{10}$$Be reaction

濱田 真悟; 安江 正治*; 久保野 茂*; 田中 雅彦*; R.J.Peterson*

Physical Review C, 49(6), p.3192 - 3199, 1994/06

https://doi.org/10.1103/PhysRevC.49.3192
 被引用回数：42 パーセンタイル：89.41(Physics, Nuclear)

65MeVの$$^{4}$$He入射粒子ビームを用いた$$^{7}$$Li($$alpha$$,p)$$^{10}$$Be反応での3核子移行反応が良い精度で行われた。ゼロレンヂDWBA近似を用いてデータとクラスターモデルの予測を較べることで、低励起のK=0$$^{+}$$,1$$^{-}$$バンドの状態への反応分光因子が求まった。Ex=17.74MeVと18.54MeVの状態に対する反応分光学因子の大きな値がみつかり、$$^{3}$$Heと$$^{7}$$Liの低エネルギーでの融合反応が宇宙初期の核合成とA=5と8の存在量の不足を説明するための重要な情報である。

論文

Nucleon transfer in highly mass-asymmetric reaction systems between $$^{197}$$Au and relatively light projectiles in the energy region below 10MeV/u, I; Target-like products

横山 明彦*; 斉藤 直*; 庄司 正秀*; 馬場 宏*; 馬場 澄子; 畑 健太郎; 関根 俊明; 市川 進一

Z. Phys., A, 332, p.61 - 69, 1989/00

非対称重イオン核反応系における核子移行反応メカニズムを研究した。即ち、$$^{197}$$Auターゲットと、$$^{37}$$Cl,$$^{16}$$O,$$^{14}$$n,$$^{12}$$C入射粒子との反応で生成するターゲット類似核に関して、励起関数と反跳飛程を測定した。得られた実験結果を解析し、準弾性散乱成分と深部非弾性散乱成分に分割し、特に準弾性散乱による核子移行反応に関してトンネリング模型に基く理論的考察を試みた。

論文

Nucleon transfer in highly mass-asymmetric reaction systems between $$^{197}$$Au and relatively light projectiles in the energy region below 10 MeV/u, II; Projectile ($$^{16}$$O)-like products

横山 明彦*; 斉藤 直*; 馬場 宏*; 畑 健太郎; 永目 諭一郎; 市川 進一; 馬場 澄子; 篠原 厚*; 今西 信嗣*

Z. Phys., A, 332, p.71 - 81, 1989/00

$$^{197}$$Auターゲットと、8.8MeV/原子及び6.6MeV/原子の$$^{16}$$O入射粒子との反応で生成した入射粒子類似核の運動エネルギースペクトルと角度分布を測定した。それらの放出過程は、準弾性散乱過程と深部非弾性散乱過程に分割できた。深部非弾性成分に関して詳細な解析を行い、この反応系の場合、比較的短い反応時間で深部非弾性散乱が起きていることを確認した。

論文

Transfer cross sections for $$^{2}$$$$^{8}$$Si+$$^{5}$$$$^{8}$$$$^{,}$$$$^{6}$$$$^{2}$$Ni

杉山 康治; 冨田 芳明; 池添 博; 井出野 一実; 鹿園 直基; 加藤 哲久*; 藤田 博*; 杉光 強*; 久保野 茂*

Phys.Lett.,B, 176(3-4), p.302 - 306, 1986/00

$$^{2}$$$$^{8}$$Si+$$^{5}$$$$^{8}$$$$^{,}$$$$^{6}$$$$^{2}$$Niの系での核子移行反応をEleb=110Mevで行った。核子移行反応の断面積は$$^{2}$$$$^{8}$$Si+$$^{5}$$$$^{8}$$$$^{N}$$iと$$^{2}$$$$^{8}$$Si+$$^{6}$$$$^{2}$$Niでは大きく違った。又一核子移行反応の断面積が最も大きかった。これらの結果は直接反応機構に基づくDWBA法の計算でよく再現できた。

口頭

Study for fission using multi-nucleon transfer reaction

西尾 勝久; 廣瀬 健太郎; L$'e$guillon, R.; 牧井 宏之; 西中 一朗; Orlandi, R.; Smallcombe, J.; 千葉 敏*; 荒木 祥平*; 渡辺 幸信*; et al.

no journal, , 

We report the recent development for the fission study using multi-nucleon transfer reaction at the JAEA tandem facility. Using multi-nucleon transfer reaction, neutron-rich nuclei can be produced, which cannot be accessed by fusion-reaction, and several nuclei populated by different transfer channels can be studied in one experiment. Another feature of transfer reaction is that the excitation energy of a compound nucleus is populated from the ground state up to several tens MeV, thus the excitation energy dependence of the fission properties can be obtained. We have carried out experiments in the reactions of $$^{18}$$O + $$^{238}$$U and $$^{18}$$O + $$^{232}$$Th. Transfer channel and the excitation energy of compound nucleus were determined by using silicon $$Delta$$E-E detectors. Fission fragments were detected by position-sensitive multi-wire proportional counters. We obtained the fragment mass distributions from actinium to plutonium isotopes for 24 nuclei and their excitation energy dependence. Among them, fragment mass distributions for nine nuclei were obtained for the first time.

口頭

Fission study of actinide nuclei using multi-nucleon transfer reaction

西尾 勝久; 廣瀬 健太郎; L$'e$guillon, R.; 牧井 宏之; 西中 一朗; Orlandi, R.; Smallcombe, J.; 千葉 敏*; 荒木 祥平*; 渡辺 幸信*; et al.

no journal, , 

Recent development of the fission study using multi-nucleon transfer reaction at the JAEA tandem facility will be presented. Using multi-nucleon transfer reaction, wide variety of nuclei around the target nucleus is produced. By identifying transfer channel, fission properties of several compound nuclei can be studied in one experiment. Another feature of transfer reaction is that excitation energy 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. Experiments were carried out in the reactions of $$^{18}$$O + $$^{238}$$U and $$^{18}$$O + $$^{232}$$Th. Transfer channel and the excitation energy of the compound nucleus were determined by using silicon $$Delta$$E-E detectors. Fission fragments are detected by position-sensitive multi-wire proportional counters. Results for fission fragment mass distributions for more than 20 nuclei and their excitation energy dependence will be discussed.

口頭

In-beam fission study at JAEA

西尾 勝久

no journal, , 

In-beam fission study at the JAEA tandem facility is discussed. The first part in the presentation is the study for reaction mechanism of fusion-fission and quasifission in relation with heavy-element synthesis. Systematic measurement of fission-fragment mass distributions using $$^{238}$$U target nucleus have been carried out. With the help of a model calculation a method to determine the fusion probability is proposed. Recently, we developed a $$^{248}$$Cm target, and series of experiment involving $$^{248}$$Cm are planned to study fission for heavier elements. The second part of the presentation is the study for fission of neutron-rich nuclei. Multi-nuclear transfer reactions were used to populate wide variety of nuclei and their excited states. Langevin-type calculation was carried out to discuss the shell damping energy of the fissioning nuclei.

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