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論文

Measurements of circular polarization from the 0.75-eV p-wave resonance of the $$^{139}$$La(n,$$gamma$$)$$^{140}$$La reaction

遠藤 駿典; 藤岡 宏之*; 後藤 優*; 猪野 隆*; 岩本 修; 岩本 信之; 河村 しほり*; 木村 敦; 北口 雅暁*; 小林 龍珠; et al.

JPS Conference Proceedings (Internet), 45, p.011056_1 - 011056_8, 2026/06

https://doi.org/10.7566/JPSCP.45.011056

The NOPTREX collaboration aims to search for time-reversal symmetry breaking (T-violation) using compound nuclear reactions. To elucidate the mechanism of T-violation in compound nuclear reactions, we are measuring the spin-angle correlation term of the (n,$$gamma$$) reaction. We have already successfully measured the angular distribution and transverse asymmetry of emitted gamma-rays for several nuclei, such as $$^{139}$$La and $$^{117}$$Sn. As the next step, we measured the circular polarization of the emitted gamma-rays from the 0.75-eV p-wave resonance of $$^{139}$$La(n,$$gamma$$)$$^{140}$$La reactions. The measurements were performed at J-PARC MLF BL04 (ANNRI). The circular polarization of gamma-rays was measured using the developed gamma-ray polarimeter. Although the circular polarization observed was weak, this first measurement on the resonances allowed us to place limits on the circular polarization from the p-wave resonance. In this presentation, we will report the details of the experiment and future plans.

論文

Study of the distribution of partial radiative widths for the $$^{181}$$Ta(n,$$gamma$$)$$^{182}$$Ta reaction

河村 しほり*; 遠藤 駿典; 岩本 修; 岩本 信之; 木村 敦; 北口 雅暁*; 中村 詔司; 奥平 琢也*; Rovira Leveroni, G.; 清水 裕彦*

JPS Conference Proceedings (Internet), 45, p.011069_1 - 011069_7, 2026/06

https://doi.org/10.7566/JPSCP.45.011069

Random Matrix Theory (RMT) has been proposed to deal with the statistics of eigenvalues and eigenfunctions of complex many-body quantum systems. For the Gaussian orthogonal ensemble (GOE) of matrices, RMT is expected to correctly describe fluctuation properties of nuclear levels at relatively high excitations, such as near the neutron threshold. The reduced partial width amplitudes, which determine the strength of the coupling between a resonance and a particular channel, have a Gaussian probability distribution centered at zero, while the reduced partial widths (the squares of the partial width amplitudes) have a chi-square distribution with one degree of freedom: the Porter-Thomas distribution. The fluctuation properties of partial radiative widths have been measured and studied for many nuclides. For $$^{182}$$Ta, the results reported by Wasson et al. and Stelts et al. are inconsistent, and its fluctuation properties of widths are not precisely understood. One possible reason for this disagreement may arise from imprecise determination of the spins of the resonances. We therefore planned to determine the spins of the resonances from measurements and examine the statistical fluctuations of the partial radiative widths based on the results of spins. In this study, as a first step, we measured the gamma-rays emitted by neutron capture reactions of $$^{181}$$Ta at J-PARC MLF ANNRI (BL04) and confirmed the fluctuations of the radiative widths. Using the spins of the resonances listed in the nuclear data library, JENDL-5, the present result was consistent with that of Stelts et al. which deviated from the Porter-Thomas distribution.

論文

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning (V); $$^{94}$$Zr(n, $$gamma$$)$$^{95}$$Zr and $$^{96}$$Zr(n, $$gamma$$)$$^{97}$$Zr reactions at JRR-3

中村 詔司; 木村 敦; 遠藤 駿典; Rovira Leveroni, G.; 芝原 雄司*

Journal of Nuclear Science and Technology, 63(6), p.653 - 666, 2026/06

https://doi.org/10.1080/00223131.2025.2586632
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

Decommissioning of nuclear facilities generates a wide variety of wastes in large quantities. To make matters more complicated, they are radioactive wastes due to neutron activation. Thus, the neutron capture cross-sections of decommissioned nuclides are required to evaluate the produced radioactivity. This study selected $$^{95}$$Zr and $$^{97}$$Zr nuclides from the nuclides targeted for decommissioning, and aimed to measure the thermal-neutron capture cross-sections of $$^{94}$$Zr and $$^{96}$$Zr, which contribute to the production of $$^{95}$$Zr and $$^{97}$$Zr, respectively. Considering the relatively small cross-sections of Zr isotopes, measurements were performed by a neutron activation method using the pneumatic tube PN-3 of the Japan Research Reactor-3 (JRR-3) because its thermal-neutron flux is 250 times larger than that of the graphite thermal column of the Kyoto University Research Reactor. A natural Zr foil was irradiated in the PN-3 and subjected to $$gamma$$-ray spectrometry. The thermal-neutron capture cross-sections were derived according to Westcott's convention to be 50.9$$pm$$0.6 millibarns for the $$^{94}$$Zr(n,$$gamma$$)$$^{95}$$Zr reaction, and 21.9$$pm$$0.3 millibarns for the $$^{96}$$Zr(n,$$gamma$$)$$^{97}$$Zr reaction. These results are consistent with recent evaluation and experimental data. It was demonstrated that the thermal-neutron capture cross-section of the order of millibarns could be straightforwardly measured by using the PN-3 of JRR-3.

論文

Neutron capture cross-section measurements at TC-Pn in KUR for tungsten among nuclides in decommissioning

中村 詔司; 芝原 雄司*; 木村 敦; 遠藤 駿典; Rovira Leveroni, G.

KURNS Progress Report 2025, P. 101, 2026/06

https://adm.rri.kyoto-u.ac.jp/pub/progressrep2/

本研究は、生成放射能を評価するために、廃止措置で問題となる核種について熱中性子捕獲断面積を測定するものである。本件では、対象核種の中から$$^{186}$$Wを選定し、京大原子炉にて放射化法によりその熱中性子捕獲断面積を測定した。今回、結果の再現性を確認するために2回の断面積測定を行い、$$^{186}$$W(n,$$gamma$$) $$^{187}$$W反応について43.5$$pm$$1.2 barns、43.1$$pm$$1.3 barnsを得た。従来の評価値38.1$$pm$$0.5 barnsは、1.4%ほど過小評価されている可能性がある。得られた断面積の結果の確かさを検証するために、Wを中性子束モニタとして使用した照射実験を1回実施した。今回得られた断面積の結果は、AuやCoモニタで求められる中性子束の結果と整合性のある中性子束を与えることを確認できた。

論文

Accurate measurement of the $$^{129}$$I neutron capture cross-section in the keV neutron region

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 片渕 竜也*

Journal of Nuclear Science and Technology, 63(4), p.358 - 369, 2026/04

https://doi.org/10.1080/00223131.2025.2543579
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

The $$^{129}$$I neutron capture cross-section was measured at the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline in the Materials and Life Science (MLF) facility of the Japan Proton Accelerator Research Complex (J-PARC). To obtain accurate results in the keV neutron region, the recently developed neutron filtering technique was employed with a 20-cm-thick $$^{nat}$$Si filter to tailor the incident neutron flux into quasi-monoenergetic neutron peaks with averaged neutron energies of 51.5 and 127.7 keV and, at the same time, hugely increase the signal-to-noise ratio. The present cross-section results were determined form the capture yield ratio of $$^{129}$$I to that of $$^{197}$$Au and using the evaluated nuclear data from JENDL-5 as reference. The $$^{129}$$I neutron capture cross section was found to be 0.278 $$pm$$ 0.034 b at 51.5 keV and 0.141 $$pm$$ 0.015 b 127.7 keV, validating the JENDL-5 and JEFF-3.3 evaluations, as well as the results from Noguere et al., in contrast to the larger evaluations of JENDL-4.0 and ENDF/B-VIII.1 and the data from Macklin et al.

論文

Neutron total and capture cross-section measurement and resolved resonance analysis of Er

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 片渕 竜也*

Annals of Nuclear Energy, 225, p.111688_1 - 111688_18, 2026/01

https://doi.org/10.1016/j.anucene.2025.111688
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

The neutron total and capture cross sections of $$^{nat}$$Er were measured at the Accurate Neutron-Nucleus Reaction Measurement Instrument beamline in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. For the neutron total cross-section measurements, Li-glass detectors were employed to derive the neutron transmission ratio of three $$^{nat}$$Er transmission samples with thicknesses of 1 mm, 0.175 mm and 0.05 mm. The neutron capture cross-section was determined from measurements of 0.025-mm-thick $$^{nat}$$Er samples with NaI(Tl) and Ge spectrometers in separate experiments, since they offer complementary capabilities. Moreover, the capture cross-section of $$^{167}$$Er was derived below 1 eV, since it accounted for over 95% of the capture events in $$^{nat}$$Er. Finally, the resolved resonance region up to 65 eV was analyzed using the REFIT code. The resonance parameters of 20 $$^{167}$$Er resonances, together with one resonance for each $$^{164}$$Er and $$^{166}$$Er were determined in a least-square fit using a combination of both capture data and the transmission data from the thicker 1 mm and 0.175 mm samples. T

論文

Revised neutron capture cross section of $$^{204}$$Pb by combining activation method and high-precision thermal ionization mass spectrometry

中村 詔司; 芝原 雄司*; 静間 俊行*; 木村 敦; 遠藤 駿典; Rovira Leveroni, G.

Journal of Nuclear Science and Technology, 9 Pages, 2026/00

https://doi.org/10.1080/00223131.2026.2666320
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

In view of the requirement for accurate cross-section data of the stable Pb isotopes in order to discuss the neutron moderation effect and neutron economy in the design of accelerator-driven systems, the authors previously derived the thermal-neutron capture cross-section of $$^{204}$$Pb by using thermal ionization mass spectrometry to be 0.537$$pm$$0.030 barn. The uncertainty in the $$^{205}$$Pb/$$^{204}$$Pb isotope ratio determined by mass spectrometry was 4.3$$%$$, bringing the total uncertainty to 5.6$$%$$. This study demonstrated that a new silica-gel emitter used in mass spectrometry improved isotope ratio precision to 1$$%$$. This enabled us to determine the reaction rate with 1$$%$$ accuracy, which exceeds the accuracy of conventional activation analysis. Owing to improved accuracy in mass spectrometry, the uncertainty has been reduced and the value of isotope ratio has changed slightly. Accordingly, the authors report a revised $$^{204}$$Pb neutron capture cross-section of 0.512$$pm$$0.019 barn.

論文

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning (IV); $$^{165}$$Ho(n,$$gamma$$)$$^{rm 166m,166g}$$Ho reactions

中村 詔司; 芝原 雄司*; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 62(11), p.1086 - 1099, 2025/11

https://doi.org/10.1080/00223131.2025.2525327
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

During the decommissioning of nuclear facilities, large amounts of radioactive wastes are generated from structural materials. When considering the disposal or reuse of such wastes, accurate neutron capture cross-sections are required to evaluate the amounts of radioactive nuclides among the wastes. The present work selected $$^{165}$$Ho among nuclides included in the list for clearance levels in decommissioning, and measured the thermal-neutron capture cross-sections for the $$^{165}$$Ho(n,$$gamma$$)$$^{rm 166m}$$Ho, $$^{rm 166g}$$Ho reactions by the neutron activation method. The thermal cross-section measurements were performed with the graphite thermal column of the Kyoto University Research Reactor under the 5-MW operation and the thermal-neutron capture cross-sections were derived on the basis of Westcott's convention. In this work, a value of 2.79$$pm$$0.04 barn was obtained for the $$^{165}$$Ho(n,$$gamma$$)$$^{rm 166m}$$Ho reaction, and 61.2$$pm$$0.6 barn for the $$^{165}$$Ho(n,$$gamma$$)$$^{rm 166g}$$Ho reaction. The combination of these cross-sections presented 64.0$$pm$$0.6 barn, which supports the recent evaluated data of 64.69 barn and 64.4$$pm$$1.2 barn within the limit of uncertainties.

論文

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (III); $$^{170}$$Er(n,$$gamma$$)$$^{171}$$Er and $$^{180}$$Hf(n,$$gamma$$)$$^{181}$$Hf reactions

中村 詔司; 芝原 雄司*; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 62(7), p.617 - 630, 2025/07

https://doi.org/10.1080/00223131.2025.2457589
 被引用回数：2 パーセンタイル：73.73(Nuclear Science & Technology)

In the decommissioning of nuclear facilities, large amounts of radioactive waste are generated due to neutron activation. In that case, neutron capture cross-sections of nuclides targeted in decommissioning are required to evaluate their radioactivities produced. The present study selected two nuclides, $$^{171}$$Er and $$^{181}$$Hf, among objective ones for decommissioning, and thermal-neutron capture cross-sections for their parent nuclides were measured by the neutron activation method at the Kyoto University Research Reactor under 1-MW operation. The thermal-neutron capture cross-sections were derived on the basis of Westcott's convention. The present study obtained the results as follows: 8.19$$pm$$0.35 barns for the $$^{170}$$Er(n,$$gamma$$)$$^{171}$$Er reaction and 13.57$$pm$$0.14 barns for the $$^{180}$$Hf(n,$$gamma$$)$$^{181}$$Hf reaction. As a by-product, the measurements of the Hf sample also yielded 0.427$$pm$$0.006 barns for the $$^{179}$$Hf(n,$$gamma$$)$$^{180m}$$Hf reaction. This study revealed that some experimental and data evaluations differ from the present results by more than the experimental uncertainties.

論文

Study of the spin-memory effect with low-energy gamma-rays in $$^{177}$$Hf(n,$$gamma$$)$$^{178}$$Hf reaction measurement

河村 しほり*; 遠藤 駿典; 岩本 修; 岩本 信之; 木村 敦; 北口 雅暁*; 中村 詔司; 奥平 琢也*; Rovira Leveroni, G.; 清水 裕彦*; et al.

EPJ Web of Conferences, 329, p.05002_1 - 05002_3, 2025/06

https://doi.org/10.1051/epjconf/202532905002
 被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)

共鳴の全角運動量は低エネルギー核反応において重要なパラメータの一つである。実験から共鳴のJを推定する方法はいくつか提案されているが、本研究ではWetzelとThomasによって提案された、共鳴のガンマ線スペクトルにおいて、適切に選ばれた2つの低エネルギーガンマ線の強度比を比較する方法に着目した。この方法は、HuizengaとVandenboschによって提案されたスピンメモリー効果(SME)に基づいている。SMEとは、カスケード遷移において多くの中間励起準位が存在しても、初期の共鳴状態のスピン情報が残ることを意味する。強度比に現れるSMEの強さは、強度比の差から定量的に評価することができる。過去の測定結果から、原子番号Zがマジックナンバー(Z=50)付近でSMEが大きくなることが示唆されている。本研究ではZ=50から離れた元素である天然のHf(Z=72)を用いて、J-PARC・MLF・ANNRIにおいて中性子捕獲反応測定を行った。SMEの強さは、共鳴からの低エネルギー$$gamma$$線の強度比から決定された。その結果、Hf(Z=72)で観測されたSMEはTa(Z=73)よりも非常に大きいことがわかった。

論文

Circular polarization measurement of $$gamma$$-rays emitted from $$^{32}$$S(n,$$gamma$$)$$^{33}$$S reaction with polarized neutrons

遠藤 駿典; 藤岡 宏之*; 井出 郁央*; 飯沼 昌隆*; 岩本 信之; 岩本 修; 亀田 健斗*; 河村 しほり*; 木村 敦; 北口 雅暁*; et al.

EPJ Web of Conferences, 329, p.05003_1 - 05003_3, 2025/06

https://doi.org/10.1051/epjconf/202532905003
 被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)

共鳴の全角運動量は核データにおいて重要なパラメータの一つであるが、その測定は困難な場合が多く、測定で決定されていないことが多い。本研究では共鳴の全角運動量を偏極中性子照射により発生したガンマ線の円偏光度の測定により決定する手法の確立を目指している。円偏光どの測定を行うためのガンマ線ポラリメータを開発し、J-PARC・MLF・ANNRIに設置し、偏極中性子入射による$$^{32}$$S(n,$$gamma$$)$$^{33}$$S反応における5.4MeVガンマ線の円偏光度の測定を行った。この5.4MeVのガンマ線は50%円偏光していることが知られており、このガンマ線を用いてポラリメータの円偏光度への感度であるAnalyzing Powerを決定することが目的である。測定の結果1%程度の差が確認され、ANNRIにて初めて円偏光度の測定に成功した。

論文

Neutron capture cross-section measurement at TC-Pn in KUR for holmium among nuclides in decommissioning

中村 詔司; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦; 芝原 雄司*

KURNS Progress Report 2024, P. 31, 2025/06

本研究は、生成放射能を評価するために、廃止措置で問題となる核種について熱中性子捕獲断面積を測定するものである。本件では、対象核種の中から$$^{166}$$Hoを選定し、京大原子炉にて放射化法によりその熱中性子捕獲断面積を測定した。今回、$$^{165}$$Ho(n,$$gamma$$)$$^{rm 166m}$$Ho反応について2.79$$pm$$0.04 barnを得た。従来の報告値は3.4$$pm$$0.5(b)に対して、誤差1.4$$%$$に向上して導出することができた。また副産物として、$$^{165}$$Ho(n,$$gamma$$)$$^{rm 166g}$$Ho反応について61.2$$pm$$0.6 barnを得た。$$^{rm 166m}$$Hoと$$^{rm 166g}$$Hoの生成の断面積を合わせて、64.0$$pm$$0.6 barnを求めた。今回の結果は、TOF法による過去の報告値64.4$$pm$$2.8(b)や、最近の評価値64.69 barn、64.4$$pm$$1.2 barnを誤差の範囲で支持した。

論文

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (II); $$^{58}$$Fe(n,$$gamma$$)$$^{59}$$Fe

中村 詔司; 芝原 雄司*; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 62(3), p.300 - 307, 2025/03

https://doi.org/10.1080/00223131.2024.2427244
 被引用回数：2 パーセンタイル：40.43(Nuclear Science & Technology)

As nuclear facilities are dismantled in decommissioning, large amount of various waste is generated. Even more inconveniently, waste is radioactive due to neutron activation. Thus, the neutron capture cross-sections of nuclides targeted in decommissioning are required to evaluate the radioactivity produced. In this work, $$^{58}$$Fe nuclide was selected among objective nuclides for decommissioning, and its thermal-neutron capture cross-section was measured by a neutron activation method at the graphite thermal column of Kyoto University Research Reactor in 5-MW operation. The thermal-neutron capture cross-section was derived using ${it Westcott'}$s convention. The present work obtained 1.36$$pm$$0.03 barns for the $$^{58}$$Fe(n,$$gamma$$)$$^{59}$$Fe reaction. The present result supports the JENDL-5 evaluation within 2$$sigma$$. If updated with currently recommended nuclear data, some of the reported past data would support the present result.

論文

原子炉施設廃止措置に関する基礎的研究

堀 順一*; 佐野 忠史*; 高宮 幸一*; 福谷 哲*; 中村 詔司; 名内 泰志*; 他3名*; 他10名*

KURNS-EKR-21, p.10 - 14, 2025/01

https://www.rri.kyoto-u.ac.jp/wp-content/uploads/houbunsyu59.pdf

本プロジェクト研究「原子炉施設廃止措置に関する基礎的研究」は、原子炉施設の廃止措置を安全且つ効率的に実施するために必要な基盤データの整備及び測定技術の開発を行うことによって、今後の京大研究炉の廃止措置作業に活用すると共に、福島第一原子力発電所で生じた燃料デブリの管理を含めた廃止措置全般の技術開発に資することを目的して、令和4年度から3か年にわたり実施された。本研究プロジェクトは、目的達成のために、7研究課題から構成されており、京都大学および他機関がそれぞれ分担して実施してきた。原子力機構は、「廃止措置における放射性廃棄物核種の核的特性に関する研究」を分担し、廃止措置で問題になる核種の生成量を評価するのに資する中性子断面積データの取得を目的として、数核種を選定してそれらの中性子捕獲断面積の導出に成功した。

論文

Neutron total and capture cross section measurements of $$^{nat}$$Er at ANNRI

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 片渕 竜也*

JAEA-Conf 2024-002, p.127 - 132, 2024/11

https://doi.org/10.11484/jaea-conf-2024-002

Measurements to measure the total and neutron capture cross section of $$^{nat}$$Er were performed in the Accurate Neutron Nucleus Reaction Measurement Instrument (ANNRI) at the Materials and Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). In this study, the preliminary results for the $$^{nat}$$Er neutron total and capture cross sections measured with Li-glass, Ge and NaI(Tl) detectors are presented and compared.

論文

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning; $$^{45}$$Sc, $$^{63}$$Cu, $$^{64}$$Zn, $$^{109}$$Ag, and $$^{113}$$In

中村 詔司; 芝原 雄司*; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 61(11), p.1415 - 1430, 2024/11

https://doi.org/10.1080/00223131.2024.2346347
 被引用回数：3 パーセンタイル：55.60(Nuclear Science & Technology)

廃止措置においては、生成放射能の評価に資する核データとして、中性子捕獲断面積を整備する必要がある。本研究では、整備すべき対象核種のうち$$^{45}$$Sc, $$^{63}$$Cu, $$^{65}$$Zn, $$^{109}$$Ag及び$$^{113}$$Inを選定し、KURのTC-Pnを用いてそれらの熱中性子捕獲断面積測定を行った。その結果、熱中性子捕獲断面積の結果が、以下のとおり得られた:$$^{45}$$Sc(n, $$gamma$$)$$^{46}$$Sc反応は27.18$$pm$$0.28 barn、$$^{63}$$Cu(n, $$gamma$$)$$^{64}$$Cu反応は4.34$$pm$$0.06 barn、$$^{64}$$Zn(n, $$gamma$$)$$^{65}$$Zn反応は0.719$$pm$$0.011 barn、$$^{109}$$Ag(n, $$gamma$$)$$^{rm 110m}$$Ag反応は4.05$$pm$$0.05 barn、そして$$^{113}$$In(n, $$gamma$$) $$^{114}$$In$$^{m1+m2}$$反応は8.53$$pm$$0.27 barn。ScとZnの結果は、これまでに報告されている評価値を誤差範囲で支持するが、一方、他の核種については評価値と異なる結果となった。得られた結果は、生成量評価にはもちろん、これらの核種を中性束モニタとして利用する場合に用いることが考えられる。

論文

Measurement of the thermal neutron capture-cross section of $$^{191}$$Ir at ANNRI MLF J-PARC

Patwary, K.; 瀬川 麻里子; 前田 亮; 藤 暢輔; 遠藤 駿典; 中村 詔司; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 61(10), p.1385 - 1396, 2024/10

https://doi.org/10.1080/00223131.2024.2334757
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

Thermal neutron capture cross-section for $$^{191}$$Ir, $$sigma$$$$_{Ir}$$(E$$_{th}$$), is a prominent parameter in producing $$^{192}$$Ir radionuclide used in high-dose-rate brachytherapy. However, considerable discrepancies exist in past measurements using the activation method and a derived cross-section data calculation from positive resonance parameters of $$^{191}$$Ir, which were measured using the neutron time-of-flight (TOF) method. Therefore, for the first time, we aimed to measure the $$sigma$$$$_{Ir}$$(E$$_{th}$$) accurately using the neutron TOF method. Experiments were performed using a pulsed neutron beam and a NaI(Tl) detector at the Accurate Neutron-Nucleus Reaction Measurement Instrument of the Materials and Life Science Experimental Facility in the J-PARC. The $$sigma$$$$_{Ir}$$(E$$_{th}$$) was derived from the capture yield using the pulse height weighting technique. As a result, this study obtained the $$sigma$$$$_{Ir}$$(E$$_{th}$$) as 949 $$pm$$ 80 b. The result agrees with some activation data and the evaluated nuclear data libraries, JENDL-5 and ENDF/B-VIII.0, within its uncertainty of 8.4%. This study provides a data reference for the $$sigma$$$$_{Ir}$$(E$$_{th}$$) measurement using the neutron TOF method.

論文

Circular polarization measurement for individual gamma rays in capture reactions with intense pulsed neutrons

遠藤 駿典; 安部 亮太*; 藤岡 宏之*; 猪野 隆*; 岩本 修; 岩本 信之; 河村 しほり*; 木村 敦; 北口 雅暁*; 小林 龍珠*; et al.

European Physical Journal A, 60(8), p.166_1 - 166_10, 2024/08

https://doi.org/10.1140/epja/s10050-024-01392-6
 被引用回数：5 パーセンタイル：73.54(Physics, Nuclear)

Measurements of $$gamma$$-ray circular polarization emitted from neutron capture reactions provide valuable information for nuclear physics studies. The spin and parity of excited states can be determined by measuring the circular polarization from polarized neutron capture reactions. Furthermore, the $$gamma$$-ray circular polarization in a neutron capture resonance is crucial for studying the enhancement effect of parity nonconservation in compound nuclei. The $$gamma$$-ray circular polarization can be measured using a polarimeter based on magnetic Compton scattering. A polarimeter was constructed, and its performance indicators were evaluated using a circularly polarized $$gamma$$-ray beam. Furthermore, as a demonstration, the $$gamma$$-ray circular polarization was measured in $$^{32}$$S(n,$$gamma$$)$$^{33}$$S reactions with polarized neutrons.

論文

Neutron capture cross-section measurements at TC-Pn in KUR for nuclides of concern in decommissioning

中村 詔司; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦; 芝原 雄司*

KURNS Progress Report 2023, P. 46, 2024/07

本研究は、生成放射能を評価するために、廃止措置で問題となる核種について熱中性子捕獲断面積を測定するものである。本件では、対象核種の中から$$^{58}$$Fe、$$^{170}$$Erおよび$$^{180}$$Hfを選定し、京大原子炉にて放射化法によりそれらの熱中性子捕獲断面積を測定した。今回、$$^{58}$$Fe(n,$$gamma$$)$$^{59}$$Fe反応について1.23$$pm$$0.03 barn、$$^{170}$$Er(n,$$gamma$$)$$^{171}$$Er反応について8.19$$pm$$0.35 barnを、そして$$^{180}$$Hf(n,$$gamma$$)$$^{181}$$Hf反応について13.57$$pm$$0.14 barnを得た。また、Hf試料の測定において副産物として、$$^{179}$$Hf(n,$$gamma$$)$$^{180m}$$Hf反応について0.427$$pm$$0.006 barnを得た。評価済みデータライブラリに採用されているデータは、今回得られた結果の不確かさ以上に違うことを明らかにした。

論文

Neutron capture cross section measurement of $$^{129}$$I and $$^{127}$$I using the NaI(Tl) spectrometer of the ANNRI beamline at J-PARC

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 藤 暢輔; 瀬川 麻里子; 前田 亮; 片渕 竜也*

European Physical Journal A, 60(5), p.120_1 - 120_14, 2024/05

https://doi.org/10.1140/epja/s10050-024-01333-3
 被引用回数：3 パーセンタイル：42.78(Physics, Nuclear)

The neutron capture cross section of $$^{129}$$I and $$^{127}$$I were measured from the thermal to the keV energy region with the NaI(Tl) spectrometer of the Accurate Neutron-Nucleus Reaction Measurement Instrument beamline in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. The neutron capture yield was determined by means of the total energy detection principle with the pulse-height weighting technique. The present cross section results for $$^{127}$$I were normalized using the saturated resonance method with a thick-enough $$^{197}$$Au and provide good agreement with JENDL-5 from thermal to about 500 keV. A resonance analysis with the REFIT code was performed and the resonance parameters for $$^{127}$$I below 310 eV are presented in this work. In the case of $$^{129}$$I, the three largest resonances of $$^{127}$$I were employed for the cross section normalization. The present results for $$^{129}$$I are the first experimental data for the neutron region between thermal and 20 eV. The present data display a different energy dependence than that in the JENDL-5 and JEFF-3.3 and much similar to that in ENDF/B-VIII.0. Notwithstanding, good agreement was found at the thermal region between the present measurement of 31.6 $$pm$$ 1.3 b and both evaluated and most experimental data.

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