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論文

Probing the nuclear interaction radius with single-proton transfer reactions

Liu, R.*; Yan, S.*; 西尾 勝久; 牧井 宏之; Orlandi, R.; 他17名*

Chinese Physics C, 50(9), p.094004_1 - 094004_6, 2026/09

https://doi.org/10.1088/1674-1137/ae7ff6
 被引用回数：0

In this work, the measurements of $$^{56,58}Fe$$($$^{18}$$O, $$^{17}$$N)$$^{57,59}$$Co transfer reactions were carried out and Distorted Wave Born Approximation calculations were employed to reproduce the experimental data with the systematic heavy ion optical potential to investigate the interaction radius. The Coulomb barrier radii $$r_{rm B}$$ were determined to be 9.58$$pm$$0.35 fm and 9.83$$pm$$0.37 fm for $$^{18}$$O+$$^{56}$$Fe and $$^{18}$$O+$$^{58}$$Fe, respectively. The maximum distances between two nuclei surfaces were calculated to be 0.68$$pm$$0.35 fm for $$^{18}$$O+$$^{56}$$Fe and 0.85$$pm$$0.37 fm for $$^{18}$$O + $$^{58}$$Fe in this work, which provide a clear physical picture of the distance between two nuclei surfaces in single-nucleon transfer reactions.

論文

Investigating the $$^{13}$$N($$alpha$$,$$p$$)$$^{16}$$O reaction rates via the $$^{19}$$F($$p$$,$$t$$)$$^{17}$$F reaction

Kim, S. H.*; Chae, K. Y.*; 浅井 雅人; 廣瀬 健太郎; 佐藤 哲也; 牧井 宏之; 西尾 勝久; Orlandi, R.; Smallcombe, J.; 洲嵜 ふみ; et al.

Journal of the Korean Physical Society, 89(5), p.488 - 493, 2026/09

https://doi.org/10.1007/s40042-026-01643-3
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

コア崩壊超新星爆発(CCSNe)の元素合成シミュレーションにおいて、$$^{13}$$N($$alpha$$,$$p$$)$$^{16}$$O反応速度の不確実性が課題となっていた。本研究では、この反応を制約するため、JAEAタンデム加速器で$$^{19}$$F($$p$$,$$t$$)$$^{17}$$F遷移反応実験を実施した。得られたトリトンスペクトルと角度分布から、関連する$$^{17}$$F共鳴の崩壊特性(部分幅)を詳細に測定し、その結果を用いて反応速度パラメータを精密化した。これにより、CCSNe核合成モデルの信頼性向上が期待できる。

論文

Deformation and magicity in heavy actinides; First observation of the ground-state rotational band of $$^{252}$$Fm

Orlandi, R.; 浅井 雅人; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; 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 Letters, 137(8), p.082501_1 - 082501_6, 2026/08

https://doi.org/10.1103/7gzt-ldn5
 被引用回数：1

The ground-state rotational band of $$^{252}$$Fm ($$Z$$ = 100, $$N$$ = 152) was investigated using two different experimental setups at the JAEA Tandem Accelerator Laboratory. The first five $$gamma$$-ray transitions of the ground-state rotational band were observed for the first time. The new data revealed that $$^{252}$$Fm possesses the lowest first excited $$2^+$$ state energy, 41.88(16) keV, and the largest kinematic moment of inertia compared to neighboring isotopes in this region. These unique properties provide strong evidence for deformed shell gaps at $$Z$$ = 100 and $$N$$ = 152, revealing that $$^{252}$$Fm is a deformed doubly magic nucleus.

論文

Fission mode identification in the $$^{180}$$Hg region; Derivative analysis approach

Kattikat Melcom, D. T.*; Tsekhanovich, I.*; Guezet, F.*; Andreyev, A.*; 西尾 勝久

Physical Review C, 114(1), p.014627_1 - 014627_8, 2026/07

https://doi.org/10.1103/qx28-3tkb
 被引用回数：0

Existence of several fission modes (paths) comes from the nuclear structure of fissiong system, and it has been discussed from the measurement of fission-fragment mass (FFMD) and total kinetic energy (TKE) distributions. For some cases, especially fission from highly excited states, the obtained FFMDs are in general structureless, which makes the identification of fission modes ambiguous and analysis dependent. It has been thus desired to develop a robust analysis approach aiming at identification of a number of major fission modes in FFMDs. For this purpose, we propose a method to calculate the second derivative of FFMD. Number of detected minima on the second derivative curve is relevant to the number of fission modes and thus determines the structure of the fit function to be used for the FFMD and TKE data description. This approach was adopted to the high-energy fission of $$^{180}$$Hg, populated by the $$^{36}$$Ar+$$^{144}$$Sm fusion reaction at the JAEA tandem facility. Compared to the previous analysis assuming only single asymmetric fission mode, the current approach shows also the signature of symmetric fission mode.

論文

Direct observation of the superallowed $$alpha$$-decay of $$^{104}$$Te

Cox, I.*; Grzywacz, R.*; King, T. T.*; Rykaczewski, K. P.*; 西尾 勝久; 他30名*

Nature, 654(8117), p.52 - 56, 2026/06

https://doi.org/10.1038/s41586-026-10581-w
 被引用回数：0 パーセンタイル：0.00(Multidisciplinary Sciences)

The radioactivity of the $$alpha$$ particle is among the most compelling evidence for the existence of cluster structures in atomic nuclei. During the decay process, a preexisting$$alpha$$ particle tunnels through the potential barrier formed by the residual nucleus. The degree of preformation of the $$alpha$$ particle, a strongly bound system of two protons and two neutrons, is extracted from the data by dividing the $$alpha$$-decay probability by the barrier penetrability for a given particle energy. The preformation probability changes rapidly near nuclear shell closures, which is direct evidence that clustering is connected to nuclear structure. Enhanced preformation was observed in the lightest $$alpha$$-particle emitters, spherical tellurium and xenon isotopes decaying to magic isotopes of tin. Here we show the most extreme case of $$alpha$$-particle preformation from the measurement of the decay of tellurium-104 ($$^{104}$$Te). With a half-life of 7.2$$^{+2.3}_{-1.5}$$ ns, $$^{104}$$Te is the fastest ground-state $$alpha$$-emitting nucleus known so far. The deduced preformation demonstrates that the enhancement is greater for $$^{104}$$Te than for any other nucleus. One nuclear model that can explain our observation postulates that the $$alpha$$ particle can exist only in the low-nuclear-matter-density regions on the surface of the nucleus. The uniquely high preformation for $$^{104}$$Te is attributed to its relation to doubly magic tin-100 ($$^{100}$$Sn), creating conditions conducive to form an $$alpha$$ particle.

論文

A Method for estimating light quenching in inorganic scintillator detectors for radioactive ion beam experiments

Kreider, B.; Cox, I.*; Grzywacz, R.*; Allmond, J. M.*; 西尾 勝久; 他23名*

Nuclear Instruments and Methods in Physics Research A, 1085, p.171298_1 - 171298_7, 2026/05

https://doi.org/10.1016/j.nima.2026.171298
 被引用回数：0 パーセンタイル：0.00(Instruments & Instrumentation)

In recent experiments, inorganic scintillators have been used to study the decays of exotic nuclei, providing an alternative to silicon detectors and enabling measurements that were previously impossible. However, proper use of these materials requires us to understand and quantify the scintillation process, specifically in response to very heavy nuclei. In this work, we show a simplified method based on the models of Birks (1951) and Meyer and Murray (1962) to parametrize the light output of inorganic scintillators in response to beams of energetic heavy ions over a broad range of energies. We test the accuracy of our parametrization approach by calculating light output and quenching factors for various ions and comparing them with experimental data from Lutetium Yttrium Orthosilicate (LYSO:Ce), a common inorganic scintillator. The Meyer-Murray model suggests that, for sufficiently heavy ions at high energies, the majority of the light output is associated with the creation of delta electrons, which are induced by the passage of the beam through the material. These delta electrons dramatically impact the response of detection systems when subject to ions with velocities typical of beams in modern fragmentation facilities. To illustrate this, we also present a qualitative estimate of the effects of delta rays on overall light output using the Birks-Meyer-Murray parametrization. The approach presented herein will serve as a basic framework for further, more rigorous studies of scintillator response to heavy ions. This work is a crucial first step in planning future experiments where energetic exotic nuclei are interacting with scintillator detectors.

論文

Design of a storage ring based on a fixed-field alternating-gradient configuration with an internal target for heavy-ion beams with stochastic charge state conversions

石 禎浩*; 上杉 智教*; 森 義治*; 西尾 勝久

Physical Review Accelerators and Beams (Internet), 29(5), p.050101_1 - 050101_14, 2026/05

https://doi.org/10.1103/th5l-mq3q
 被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)

In heavy-ion accelerators used for radioactive isotope production, the accelerated beam is typically directed onto a target and then discarded in a beam dump. To make more efficient use of the beam, recycling of the beam passed through the target is proposed in the framework of the so-called energy recovery internal target (ERIT). In the ERIT system, the target is irradiated by a circulating beam, while the energy lost in the target is recovered using rf cavities. So far, such a system has been realized only for proton beams. Here, an ERIT system for heavy-ion beams is demonstrated for the first time. A major challenge is the circulation of ions with multiple atomic charge states. After passing through the target, ions rapidly reach an equilibrated charge-state distribution, independent of the initial charge state. This stochastic charge-state conversion (SCSC) leads to rapid beam-emittance growth. To mitigate this effect, we develop a method to match the closed orbits and betatron functions of different charge states at the target location, based on a scaling fixed-field alternating-gradient (FFA) lattice. We present the design of such an FFA ring and show, through 6D beam-tracking simulations, that the transverse emittance growth induced by SCSC can be significantly reduced over a practical number of turns, whereas longitudinal emittance growth remains significant and is discussed separately.

論文

科学と技術のための核データ国際会議(ND2025)

岩本 修; 小浦 寛之; 遠藤 駿典; 木村 敦; 中山 梓介; 荒木 祥平; 西尾 勝久; 大塚 直彦*; 湊 太志*; 渡辺 幸信*; et al.

核データニュース(インターネット), (142), p.18 - 30, 2025/10

http://www.aesj.or.jp/~ndd/ndnews/No142.html

2025年6月にマドリッドで開催された科学と技術のための核データ国際会議ND2025の参加報告である。開催国を除いて参加者の多かった国を順に並べるとアメリカ、フランス、日本、中国、イギリスとなる。前回よりも遠方での開催となったにも関わらず、日本の参加者が前回よりも増えていた。月曜から原子核データについて多くを網羅したトピックについて発表がなされた。具体的には原子核反応測定、原子核構造、原子核崩壊データ、施設と装置、サンプル準備、核分裂と核破砕、原子炉のための核データ、核融合、天体核物理と宇宙応用、医療応用、核廃棄物管理、臨界安全、同位体生成、原子核理論、モンテカルロシミュレーション、機械学習、原子核データ評価、標準化、積分実験と妥当性、普及活動、教育・トレーニング・アウトリーチ、であった。本報告では測定、評価・ライブラリ、積分検証、核分裂、ミューオンの各分野それぞれについて執筆した。

論文

Neutron emission during fission and its impact on fission-fragment mass distribution studied by a Langevin model

高木 慎弥*; 原田 壮太*; 有友 嘉浩*; 廣瀬 健太郎; 西尾 勝久

Physical Review C, 112(4), p.044607_1 - 044607_9, 2025/10

https://doi.org/10.1103/ml4c-3k8t
 被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)

Actinide nucleus shows mass-asymmetric fission in low energy due to shell structure. The fission fragment mass distributions at high energy tend to have a symmetric shape due to smearing of the shell. On the other hand, the distribution can be changed by the neutron emission before fission, as it decreases the excitation energy of fissioning nucleus, thus revives the shell structure. In the so called multichance fission, neutron emission is considered at the ground state shape, and competition between fission and neutron emission is determined in the framework of statistical model. In the present work, we describe fission in the Langevin equations, and the neutron emission is treated all over the fission process. The calculation demonstrated experimentally observed mass distribution, characterized by the peak-to-valley ratio, for wide range of initial compound-nucleus excitation energy up to 60MeV. The results show that, while neutron emission dominates at the ground state shape, it occurs along the shape evolution down to the scission point.

論文

Experimental determination of the resonance width and the branching ratio $$Gamma_{p1}$$/$$Gamma_{p0}$$ for the 19.40-MeV state in $$^{8}$$Be for studying the $$^{7}$$Be($$n$$,$$p1$$)$$^{7}$$Li$$^{*}$$ reaction relevant to the cosmological lithium problem

岩佐 直仁*; 西尾 勝久; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; 洲嵜 ふみ; Smallcombe, J.; 他7名*

Physical Review C, 112(3), p.035801_1 - 035801_6, 2025/09

https://doi.org/10.1103/jhgx-cht5
 被引用回数：2 パーセンタイル：66.26(Physics, Nuclear)

The $$^{7}$$Li($$^{3}$$He,$$d$$)$$^{8}$$Be$$^{*}$$($$p$$)$$^{7}$$Li reaction was measured at $$E_{lab}$$($$^{3}$$He) = 28 MeV for studying the $$^{7}$$Be($$n$$,$$p1$$)$$^{7}$$Li$$^{*}$$ reaction, which is a $$^{7}$$Be destruction reaction in the big bang nucleosynthesis. Resonant states at 18.9$$-$$20.1 MeV in $$^{8}$$Be were populated by the $$^{7}$$Li($$^{3}$$He,$$d$$)$$^{8}$$Be$$^{*}$$ reaction and decay protons to the ground ($$p0$$) and first-excited states ($$p1$$) in $$^{7}$$Li were well separated and measured. The resonance width $$Gamma$$ and branching ratio $$Gamma_{p1}$$/$$Gamma_{p0}$$ for the 19.40-MeV state in $$^{8}$$Be were deduced to be 342$$pm$$112 keV and 11.2 $$pm$$ 3.5 $$pm$$ 5.0 (syst.)%, respectively. The $$7$$Be($$n$$,$$p1$$)$$^{7}$$Li$$^{*}$$ reaction cross section was deduced.

論文

Kinetic energy of fission fragments within a dynamical model

高木 慎弥*; 有友 嘉浩*; 中島 滉太*; 岡田 和記; 廣瀬 健太郎; 西尾 勝久

Physical Review C, 112(1), p.014608_1 - 014608_7, 2025/07

https://doi.org/10.1103/8smy-1ls9
 被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)

Kinetic energy of individual fission fragment for actinide nuclei is, for example, important for evaluating the prompt-neutron spectrum in the laboratory system. It is experimentally known that kinetic energy for each fragment is constant at about 100 MeV for light fragments and that for heavy fragments decreases linearly with mass number. Most of the theoretical studies carried out so far attempted to calculate the total kinetic energy of both fragments, i.e. sum of the energies of two fragments, but the kinetic energy of each fragment was not analyzed in detail as far as we recognize. We have calculated them in thermal-neutron induced fission of $$^{239}$$Pu with a dynamical model using Langevin equations within a three-dimensional two-center parametrization. Also fission of $$^{258}$$Fm was investigated. It is calculated from the Coulomb energy at the scission point and the pre-scission kinetic energy. It is found that the pre-scission kinetic energy has about 2-4% contribution in the kinetic energy. The calculated results reproduce the trend of the experimental data.

論文

Competition between mass-symmetric and asymmetric fission modes in $$^{258}$$Md produced in the $$^{4}$$He + $$^{254}$$Es reaction

西尾 勝久; 廣瀬 健太郎; 牧井 宏之; Orlandi, R.; Kean, K. R.*; 塚田 和明; 豊嶋 厚史*; 浅井 雅人; 佐藤 哲也; Chiera, N. M.*; et al.

Physical Review C, 111(4), p.044609_1 - 044609_12, 2025/04

https://doi.org/10.1103/PhysRevC.111.044609
 被引用回数：1 パーセンタイル：43.93(Physics, Nuclear)

In spontaneous fission (SF) it is found that the mass-asymmetric fission of well-known actinides suddenly changes to the symmetric fission when nucleus has a mass number $$A_{c}$$ larger than 257. We have measured for the first time fission-fragment mass and total-kinetic-energy (TKE) distributions of the excited compound nucleus $$^{258}$$Md, populated in the reaction $$^{4}$$He+$$^{254}$$Es, using the rare isotope $$^{254}$$Es with a short half-life, $$T_{1/2}$$=276 days. The fission of $$^{258}$$Md can be interpreted as involving 3 fission modes: an mass-asymmetric mode and two modes of mass-asymmetric fissions, the latter two are manifested by different TKE values. Predominantly symmetric fission was obtained at the excitation energy of 15.0 MeV. By increasing the energy to 18.0 MeV, the asymmetric fission mode dominates. Both such a strong change of fission modes within a small increase of excitation energy and the enhancement of asymmetric split are new phenomena in fission.

論文

Giant dipole resonance photofission and photoneutron reactions in $$^{238}$$U and $$^{232}$$Th

Filipescu, D.*; Gheorghe, I.*; Goriely, S.*; 西尾 勝久; 宇都宮 弘章*; 洲嵜 ふみ; 廣瀬 健太郎; 他10名*

Physical Review C, 109(4), p.044602_1 - 044602_23, 2024/04

https://doi.org/10.1103/PhysRevC.109.044602
 被引用回数：6 パーセンタイル：76.58(Physics, Nuclear)

New measurements of photofission and photoneutron reactions on $$^{238}$$U and $$^{232}$$Th in the Giant Dipole Resonance (GDR) energy region have been performed at the laser Compton-scattering $$gamma$$-ray source of the NewSUBARU synchrotron radiation facility. The photoneutron ($$gamma, in$$) with $$i$$ = 1-3 and photofission ($$gamma, F$$) reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutron (PFN) multiplicities predicted by the theory of evaporation in sequential neutron emission from excited fission fragments. We report experimental ($$gamma, n$$), ($$gamma, 2n$$), ($$gamma, 3n$$) and ($$gamma, F$$) cross sections, average energies of PFNs and of($$gamma$$, $$in$$) photoneutrons, as well as the mean number of PFNs per fission and the width of the PFNs multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions.

論文

Search for the 6$$alpha$$ condensed state in $$^{24}$$Mg using the $$^{12}$$C+$$^{12}$$C scattering

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

https://doi.org/10.1016/j.physletb.2023.138384
 被引用回数：12 パーセンタイル：81.41(Astronomy & Astrophysics)

We searched for the 6$$alpha$$-condensed state in $$^{24}$$Mg by measuring the $$^{12}$$C+$$^{12}$$C scattering with the SAKRA Si detector array. By using the invariant-mass method for the detected 3$$alpha$$ particles, the inclusive cross sections for the $$^{12}$$C+$$^{12}$$C $$rightarrow$$ $$^{12}$$C(0$$^{+}_{2}$$) + X and $$^{12}$$C(3$$^{-}_{1}$$) + X reactions were determined. In both the inclusive $$^{12}$$C(0$$^{+}_{2}$$) + X channel and the exclusive $$^{12}$$C(0$$^{+}_{2}$$) + $$^{12}$$C(0$$^{+}_{1}$$) channel, the cross section peaked at E$$_{cm}$$ = 19.4 MeV, which correspond to the excitation energy of E$$_{x}$$ = 33.3 MeV in $$^{24}$$Mg. This 19.4-MeV state is a candidate for the 6$$alpha$$-condensed state

論文

Neutron-production double-differential cross sections of $$^{rm nat}$$Pb and $$^{209}$$Bi in proton-induced reactions near 100 MeV

岩元 大樹; 明午 伸一郎; 佐藤 大樹; 岩元 洋介; 石 禎浩*; 上杉 智教*; 八島 浩*; 西尾 勝久; 杉原 健太*; $c{C}$elik, Y.*; et al.

Nuclear Instruments and Methods in Physics Research B, 544, p.165107_1 - 165107_15, 2023/11

https://doi.org/10.1016/j.nimb.2023.165107
 被引用回数：5 パーセンタイル：49.60(Instruments & Instrumentation)

入射陽子エネルギー200MeV以下の中性子生成に関する二重微分断面積(DDX)データの不足は、加速器駆動核破砕システム(ADS)の研究開発などの技術応用における核破砕モデルの検証を妨げている。本研究では、このエネルギー領域におけるADS核破砕ターゲット材料のDDX実験データを取得し、解析予測との比較を通じて核破砕モデルに関する課題を明らかにすることを目的とした。実験は、京都大学のFFAG加速器を用いて行った。100MeV領域の$$^{rm nat}$$Pbと$$^{209}$$Biの陽子入射核反応に対するDDXを飛行時間法を用いて30$$^{circ}$$から150$$^{circ}$$の角度範囲で測定した。得られたDDXをモンテカルロ法に基づく種々の核破砕モデル及び評価済み核データライブラリによる計算結果と比較した。DDXの測定値と核破砕モデル及び評価済み核データライブラリに基づく解析値を比較した結果、CEM03.03モデルが実験値に最も近い一致を示した。さらに、100MeV領域における陽子入射中性子生成DDXの再現性向上のために対処すべき複数の課題を明らかにした。

論文

Photofission and photoneutron cross sections for $$^{238}$$U and $$^{232}$$Th

Filipescu, D.*; 西尾 勝久; 洲嵜 ふみ; 廣瀬 健太郎; 他12名*

EPJ Web of Conferences, 284, p.04010_1 - 04010_4, 2023/05

https://doi.org/10.1051/epjconf/202328404010
 被引用回数：3 パーセンタイル：85.40(Nuclear Science & Technology)

Photofission and photoneutron reactions on $$^{238}$$U and $$^{232}$$Th in the energy range of 5.87 MeV - 20.14 MeV was carried out at the Compton-scattering $$gamma$$-ray source of the NewSUBARU synchrotro radiation facility of SPring-8, Japan. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron ($$gamma$$,xn) and photofission ($$gamma$$,fxn) reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutrons (PFN) multiplicities predicted by the evaporation theory. We here provide preliminary experimental ($$gamma$$, n), ($$gamma$$, 2n) and ($$gamma$$, F) cross sections, average energies of PFN and of photoneutrons emitted in ($$gamma$$, n) and ($$gamma$$, 2n) reactions, as well as the mean number of PFN per fission.

論文

Measurement of double-differential neutron yields for iron, lead, and bismuth induced by 107-MeV protons for research and development of accelerator-driven systems

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

https://doi.org/10.1051/epjconf/202328401023
 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。

論文

Measurement of 107-MeV proton-induced double-differential thick target neutron yields for Fe, Pb, and Bi using a fixed-field alternating gradient accelerator at Kyoto University

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

https://doi.org/10.1080/00223131.2022.2115423
 被引用回数：4 パーセンタイル：38.40(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。

論文

多核子移行反応における角運動量の付与; 超重元素領域にある安定の島をめざすには

西尾 勝久

Isotope News, (785), p.36 - 40, 2023/02

https://www.jrias.or.jp/pdf/2302_TRACER_NISHIO.pdf

多核子移行反応は、中性子数の多いアクチノイドおよび超重元素同位体を生成する方法として注目を集めている。反応の直後、高励起状態の複合核が生成されるが、これらが核分裂することなく中性子を放出して冷え固まることで中性子過剰核が生成される。ここで、複合核に付与される角運動量が大きいと、核分裂で壊れて何も残らない。本研究は、多核子移行反応における角運動量の付与を定量的に示した研究成果の解説である。

論文

京都大学FFAG加速器を用いた加速器駆動型核変換システム(ADS)用核データの実験的研究

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

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/TUP0/TUP040.pdf

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$$^{208}$$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、$$^{209}$$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、$$^{237}$$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。

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