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Se from combined conversion-electron and 
-ray spectroscopySmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Muir, D.*; Pr
chniak, L.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; et al.
Physical Review C, 110(2), p.024318_1 - 024318_16, 2024/08
被引用回数：1 パーセンタイル：52.60(Physics, Nuclear)In the selenium isotopes various shape phenomena are present, in particular the emergence of a dominant oblate deformation in the most neutron-deficient isotopes has been observed. The scenario of shape coexisting oblate and prolate bands has been proposed across the isotopic chain, with the crossing point of such bands being located near Se, where no coexistence has yet been identified. To determine the presence or absence of any low-lying 
state in Se, confirm the level structure, and interpret the nuclear deformation with theoretical models. A combined internal conversion electron and -ray spectroscopy study was undertaken with the SPICE and TIGRESS spectrometers at the TRIUMF-ISAC-II facility. Nuclear models were provided by the Generalised Triaxial Rotor Model (GTRM) and the collective Generalised Bohr Hamiltonian (GBH). Despite a comprehensive search, no evidence was found for the existence of a state below 2 MeV in Se. Significant discrepancies to the previously established positive parity level scheme were found. GBH calculations using UNEDF1 mass parameters were found to reproduce the revised low-lying level structure well. Se does not have a well defined axial shape. The 2
state at 1601 keV resembles a quasi- excitation rather than a member of a shape coexisting band; the presence of such a band is all but ruled out.
Martel, I.*; Acosta, L.*; Aguado, J. L.*; Smallcombe, J.; 他68名*
Nuclear Instruments and Methods in Physics Research B, 541, p.176 - 179, 2023/08
被引用回数：3 パーセンタイル：59.85(Instruments & Instrumentation)The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the Isolde Superconducting Recoil Separator (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.
Eu; Quasiparticle configurations of excited states and structure of 
= 4
bandheads in GdYates, D.*; Kr
cken, R.*; Dillmann, I.*; Garrett, P. E.*; Smallcombe, J.; 他44名*
Physical Review C, 107(6), p.064309_1 - 064309_20, 2023/06
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)Detailed spectroscopy of neutron-rich, heavy, deformed nuclei is of broad interest for nuclear astrophysics and nuclear structure. Nuclei in the 
-process path and following freeze-out region impact the resulting -process abundance distribution, and the structure of nuclei midshell in both proton and neutron number helps to understand the evolution of subshell gaps and large deformation in these nuclei.
Sun, L. J.*; Fry, C.*; Davids, B.*; Esker, N.*; Wrede, C.*; Smallcombe, J.; 他27名*
Physics Letters B, 839, p.137801_1 - 137801_8, 2023/04
被引用回数：2 パーセンタイル：43.87(Astronomy & Astrophysics)Motivated primarily by the large uncertainties in the thermonuclear rate of the 30PS reaction that limit our understanding of classical novae, we carried out lifetime measurements of 
S excited states using the Doppler Shift Lifetimes (DSL2) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility.
0 transition strength for 
Se using the SPICE spectrometerSmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; Barton, C. J.*; Bhattacharjee, S. S.*; et al.
Physical Review C, 106(1), p.014312_1 - 014312_9, 2022/07
被引用回数：5 パーセンタイル：60.14(Physics, Nuclear)The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton dripline. In this work a study of Se by internal conversion electron and -ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the 
state were performed yielding a determination of 
milliunits. Two state mixing calculations were performed that highlighted the importance of interpretation of such 
strength values in the context of shape-coexistence.
decay of 
Te with a novel recoil-decay scintillation detectorXiao, 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：19 パーセンタイル：83.32(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 XeTe 
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.
廣瀬 健太郎; 西尾 勝久; 田中 翔也*; L
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
被引用回数：59 パーセンタイル：91.35(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; 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.
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：3 パーセンタイル：83.31(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 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.
O + Th reactionLguillon, 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：45 パーセンタイル：92.63(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.
洲嵜 ふみ; 西尾 勝久; Andreyev, A. N.*; 廣瀬 健太郎; Orlandi, R.; 牧井 宏之; Smallcombe, J.; 伊藤 由太
no journal, ,
天体における元素合成や超重元素の合成の分野において、中性子の多い原子核を生成する反応として多核子移行反応が注目されている。これら中性子過剰核の生成断面積は、多核子移行反応で複合核を生成する断面積と、複合核が核分裂することなく脱励起して生き残る確率の積で表される。この生き残り確率は、複合核の励起エネルギー分布とスピン分布に依存するが、核分裂が競合する領域での詳細なデータはほとんどない。本研究では、蒸発残留核断面積を測定することでこれらを明らかにすることを目標とする。実験は、JAEA反跳生成核分離装置(JAEA-RMS)を用いて行った。JAEA-RMSを回転させることで、断面積の角度依存性を調べることができる。実験手法を確立するため、まず
Si+
Bi反応を調べた。JAEA-RMSの焦点において蒸発残留核の崩壊を測定し、核種を同定した。その上で、核種ごとに断面積の角度依存性を決定したので報告する。
Se nuclear shapes with SPICE and TIGRESSSmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*
no journal, ,
The phenomenon of shape coexistence is prevalent in the Z~34 region, with isotopes of neutron-deficient even Ge, Se and Kr each exhibiting the characteristic low-lying coexisting 0 bands which display quadrupole deformation different to that of the ground states. In the selenium isotopes, 
Se seem to show a prolate ground structure with shape coexisting oblate excitation, while in 
Se the oblate structure appears to have become the ground state. The exact nature of the low-lying structure Se and any shape coexistence remains uncertain. Combining the Spectrometer for Internal Conversion Electrons (SPICE) with the TIGRESS HPGe Array, a full electron and gamma-ray experimental study of Se was undertaken at the TRIUMF ISAC-II facility to unveil the low-lying structure of these nuclei. Details of the device and experiment will be presented, alongside the experimental results and possible structural interpretations for both isotopes.
Li+
W反応で観測された質量非対称核分裂田村 信行; 廣瀬 健太郎; 西尾 勝久; 西中 一朗; 牧井 宏之; Orlandi, R.; Lguillon, R.; Smallcombe, J.; Andreyev, A. N.; 大槻 勤*; et al.
no journal, ,
原子力機構・先端基礎研究センターでは、陽子過剰核
Hgにおいて質量非対称な核分裂を観測し、アクチノイド原子核以外にも質量非対称分布を示す新たな領域が独立して存在することを明らかにした。理論によれば、鉛より軽い元素の中性子過剰核側に新たな質量非対称核分裂を示す原子核が存在するとされた。これを確認することを目的とし、本実験研究では、Li+W反応で生成される原子核の質量数分布を測定した。比較実験のため、Li+
W反応も調べた。実験は、原子力機構タンデム加速器施設で行った。この結果、Li+W反応において質量非対称分裂を観測した。解析の結果、Liのブレークアップによって生成された
HがWに吸収されてできる
Reが質量非対称分裂の原因であると考えられた。
82 nuclei at the JAEA Tandem FacilitySmallcombe, J.; 西尾 勝久; 廣瀬 健太郎; 西中 一朗; 牧井 宏之; Orlandi, R.; 田村 信行*; 後藤 真一*; 大槻 勤*; Andreyev, A.*; et al.
no journal, ,
Recent 
-delayed fission studies of proton rich Hg showed the fission to be dominated by asymmetric fragment masses, in contrast to initial predictions. Models of the potential-energy surface for the path toward scission showed a lower fission barrier for an asymmetrically deformed Hg volume. As a probe of this theoretical interpretation, fission of Hg was induced through the symmetric reaction 
Z
Z. Mass and energy distributions of fragments for a series of bombarding energies were recorded using 2 MWPCs. As a continuation of Z 
fission studies, fission induced in the Li
W reactions were measured. Near A190 a new region of asymmetric fission is predicted to emerge as one moves towards neutron rich nuclei. In preliminary investigations mass asymmetry was observed in fragments of the Li
W reaction. However, fragment kinematics were inconsistent with fission of 
Ir formed by fusion. A follow up experiment was conducted in an attempt to confirm the first observation of fission induced by the Li breakup-fusion reaction W
Li,
He
Re. Experimental details and initial results will be presented.
廣瀬 健太郎; 西尾 勝久; Lguillon, R.; 牧井 宏之; 西中 一朗; Orlandi, R.; Smallcombe, J.; 石井 哲朗; 塚田 和明; 浅井 雅人; et al.
no journal, ,
We have developed a measurement system for the multi-nucleon transfer reaction and been studying fission of short-lived minor actinides and neutron-rich nuclides. The experiment was performed at the tandem accelerator facility of Japan Atomic Energy Agency where targets of U, Th, Cm were irradiated with O beams. In this experiment, more than ten nuclides were excited up to few tens of MeV at a time. Projectile-like scattered particles after the multi-nucleon transfer reaction were detected and identified using a E-E silicon telescope. The mass distribution was deduced from the time difference between two fission fragments from the compound nucleus which were detected using two pairs of multi-wire proportional counters. Neutrons accompanied by fission were also measured using liquid scintillators placed around the reaction chamber. In the nucleon transfer reaction, the axis of the angular-momentum transfer can be determined from the direction of the scattered particle. This is one of the most different point from the neutron/ion-induced fusion-fission reaction where only the plane on which the axis lies can be determined. The fission angular distributions with respect to this axis as well as the mass yield, the prompt neutron multiplicity and so on will be presented.
O+Cm反応における核子移行核分裂の測定廣瀬 健太郎; 西尾 勝久; Lguillon, R.; Smallcombe, J.; 西中 一朗; 牧井 宏之; Orlandi, R.; 塚田 和明; 千葉 敏*; 大槻 勤*; et al.
no journal, ,
短寿命アクチノイド核種や中性子過剰アクチノイド核種の核分裂を研究するために、我々は多核子移行反応測定システムを構築し、O+U, O+Th反応における多核子移行核分裂の測定を行ってきた。今回はO+Cm反応の測定を行い、
Cm, 
Bk, 
Cfの核分裂質量分布を得た。実験は原子力研究開発機構のタンデム加速器施設で行った。エネルギー162MeVに加速したOビームを、ニッケル箔に電着したCm標的に照射することでさまざまな複合核を合成した。核子を移行した後の散乱粒子を、シリコン検出器を使って同定することで、複合核の核種を知ることができる。2つの核分裂片を多芯線比例計数検出器を使って、散乱粒子と同時計測することで、合成した複合核の核分裂を観測した。
Cm, 
Bk, 
Cfの核分裂質量分布は本測定により初めて得られた。
西尾 勝久; 廣瀬 健太郎; Lguillon, R.; Orlandi, R.; 西中 一朗; Smallcombe, J.*; 千葉 敏; 荒木 祥平*; 渡辺 幸信*; 立澤 遼太郎*; et al.
no journal, ,
A recent development of fission study using multi-nucleon transfer reaction at the JAEA tandem facility will be presented. Using multi-nucleon transfer reactions, a wide variety of nuclei around a target nucleus is produced. By identifying transfer channels, fission data 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 widely from the ground state up to several tens MeV, allowing us to study the excitation energy dependence of fission properties. The experiments were carried out in the reactions of O + U, Th, Cm. Results for fission fragment mass distributions and their excitation energy dependence are compared with a model calculation based on a fluctuation dissipation model. Also, experimental data of prompt neutron multiplicity in fission and angular distribution of fission fragments will be discussed.
西尾 勝久; 岩本 修; 牧井 宏之; 廣瀬 健太郎; Orlandi, R.; 洲嵜 ふみ; 塚田 和明; 浅井 雅人; Smallcombe, J.
no journal, ,
長寿命マイナーアクチノイド(MA)原子核を核変換する加速器駆動炉など次世代の原子炉システムを設計するためには高エネルギーまでの中性子入射断面積が必要である。本発表では、実験データがほとんどない非弾性散乱断面積に加え、核分裂断面積、捕獲断面積、(n,2n)断面積を同時に測定する技術開発の計画を示す。
洲嵜 ふみ; 西尾 勝久; 牧井 宏之; 廣瀬 健太郎; Orlandi, R.; Smallcombe, J.; 浅井 雅人
no journal, ,
重イオン反応における多核子移行反応は中性子数の多い原子核をつくる反応として注目されているが、目的とする原子核を生成する最適な反応と実験条件を決めるには、詳細な実験データの取得と理論の構築が必要である。原子力機構では多核子移行反応で生成される蒸発残留核の詳細な測定をすすめており、最初の結果を示す。
洲嵜 ふみ; 西尾 勝久; 牧井 宏之; 廣瀬 健太郎; Orlandi, R.; Smallcombe, J.
no journal, ,
Multinucleon transfer (MNT) reactions have attracted attention in the field of nuclear physics and astronomical nucleosynthesis as a reaction which produces neutron-rich nuclei as evaporation residues (ER). But detailed feature of reaction mechanism is not understood. Detailed experimental data are necessary to develop a model to guide an optimal reaction and experimental condition. We have started the measurement of ER cross sections in various conditions. Experiments were carried out using the JAEA Recoil Mass Separator (JAEA-RMS). As a first attempt, we studied the reaction Si+Bi. The production cross sections for each produced isotopes are determined as a function of recoil angle and recoil energy (thus Q-value), where identification of nuclides were achieved by the on-line alpha-decay measurement of the implanted ERs at the focal plane Si detector. The result is the first to realize the on-line decay measurement produce in the MNT reaction at a finite angle.
