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論文

Branching and fragmentation of dipole strength in $$^{181}$$Ta in the region of the scissors mode

Angell, C.; 羽島 良一; 静間 俊行; Ludewigt, B.*; Quiter, B. J.*

Physical Review Letters, 117(14), p.142501_1 - 142501_5, 2016/09

 被引用回数:7 パーセンタイル:49.16(Physics, Multidisciplinary)

In recent measurements of the scissors mode in radiative decay experiments, transition strengths were observed that were double that expected from theory and systematics well established from measurements on the radiative excitation channel, that is, using nuclear resonance fluorescence (NRF). Additional strength as measured with NRF can only present itself as heretofore unobserved branching or fragmentation of the scissors mode. Such a possibility was investigated in a transmission NRF measurement on the deformed, odd-mass $$^{181}$$Ta, using a quasi-monoenergetic $$gamma$$-ray beam at two beam energies, and additionally informing applications using transmission NRF to assay or detect odd-mass fissile isotopes. An anomalously large branching, $$approx$$70%, of small resonances to excited states was discovered. In contrast, previous studies using NRF of the scissors-mode strength in odd-mass nuclei assumed no branching existed. This branching, if present at all energies, combined with the observed highly-fragmented elastic strength would reconcile the scissors-mode strength observed in NRF measurements with the expectations for enhanced scissors-mode strength from radiative decay experiments.

論文

Demonstrating the integral resonance transmission method; Conceptual and experimental studies

Angell, C.; 早川 岳人; 静間 俊行; 羽島 良一; Quiter, B. J.*; Ludewigt, B. L.*; Karwowski, H. J.*; Rich, G.*; Silano, J.*

Proceedings of INMM 56th Annual Meeting (Internet), 9 Pages, 2015/07

Nuclear resonance fluorescence (NRF) is a promising technique for assaying $$^{239}$$Pu in spent nuclear fuel and for SNM detection applications because of its isotope-specific nature and potential for high sensitivity. To fully utilize the next generation of high-flux $$gamma$$-ray sources for NRF applications we developed the integral resonance transmission (IRT) method which integratesover all resonances within the energy width of a quasi-monoenergetic $$gamma$$-ray beam allowing the full utilization of the transmission signature. To realize the IRT technique both conceptual studies, exploring the consequences of the loss of resolution, and experimental studies, demonstrating several aspects of the IRT method, were undertaken. The conceptual studies included the development of a performance metric allowing comparison between using the IRT technique and single resonances, a study of the magnitude of resonance overlap, and beam simulations examining performance as a function of beam width. The experimental studies were done at the HI$$gamma$$S facility at Duke University, and included an experiment constraining resonance overlap in a NRF transmission measurement through a TMI-2 type canister, demonstration of the IRT technique by a NRF measurement on $$^{181}$$Ta, and the world's first transmission NRF measurement on $$^{239}$$Pu. In this talk, we will overview each component of the conceptual and experimental studies for the IRT method.

論文

Improving the assay of $$^{239}$$Pu in spent and melted fuel using the nuclear resonance fluorescence integral resonance transmission method

Angell, C.; 早川 岳人; 静間 俊行; 羽島 良一; Quiter, B. J.*; Ludewigt, B. L.*; Karwowski, H.*; Rich, G.*

Nuclear Physics and $$gamma$$-ray sources for Nuclear Security and Nonproliferation, p.133 - 141, 2014/12

Non-destructive assay (NDA) of $$^{239}$$Pu in spent nuclear fuel is possible using the isotope-specific nuclear resonance fluorescence (NRF) integral resonance transmission (IRT) method. The IRT method measures the absorption of photons from a quasi-monoenergetic $$gamma$$-ray beam due to all resonances in the energy width of the beam. According to calculations the IRT method could greatly improve assay times for $$^{239}$$Pu in nuclear fuel. To demonstrate and verify the IRT method, we first measured the IRT signature in $$^{181}$$Ta, and subsequently made IRT measurements in $$^{239}$$Pu. These measurements were done using the quasi-monoenergetic beam at the High Intensity $$gamma$$-ray Source (HI$$gamma$$S) in Durham, NC, USA. The IRT signature was observed as a decrease in scattering strength when the same isotope material was placed in the beam line upstream of the scattering target. The results confirm the validity of the IRT method in both $$^{181}$$Ta and $$^{239}$$Pu.

論文

Demonstration of the nuclear resonance fluorescence integral resonance transmission method for NDA of debris of melted nuclear fuel

Angell, C.; 早川 岳人; 静間 俊行; 羽島 良一; Quiter, B. J.*; Ludewigt, B. L.*; Karwowski, H.*; Rich, G.*

Proceedings of INMM 54th Annual Meeting (CD-ROM), 7 Pages, 2013/07

Non-destructive assay (NDA) of $$^{239}$$Pu in spent nuclear fuel is possible using the isotope-specific nuclear resonance fluorescence (NRF) integral resonance transmission (IRT) method. The IRT method measures the absorption of photons from a quasi-monoenergetic $$gamma$$-ray beam due to all resonances in the energy width of the beam. According to calculations the IRT method could greatly improve assay times for $$^{239}$$Pu in nuclear fuel. To demonstrate and verify the IRT method, we measured the IRT signature in a simulant material, $$^{181}$$Ta, whose nuclear resonant properties are similar to those of $$^{239}$$Pu. Measurements were made at beam energies of 2.27 and 2.75 MeV, using metallic Ta for both the absorption and scattering targets. The scattered radiation was measured using HPGe and LaBr detectors. The results confirm the validity of the IRT method and a similar result is expected on $$^{239}$$Pu.

口頭

Demonstration of the nuclear resonance fluorescence integral resonance transmission method for assay of $$^{239}$$Pu in spent and melted fuel

Angell, C.; 早川 岳人; 静間 俊行; 羽島 良一; Quiter, B. J.*; Bernhard, L.*; Hugon, K.*; Grayson, R.*

no journal, , 

Non-destructive assay (NDA) of $$^{239}$$Pu in spent nuclear fuel is possible using the integral resonance transmission (IRT) method. IRT measures the integral nuclear resonance fluorescence scattering on a mono-isotopic witness target following resonance absorption in nuclear fuel. Verification of the IRT method was obtained in a demonstration experiment using $$^{239}$$Pu.

口頭

共鳴吸収法を用いたTa-181の双極子準位の分岐比測定

静間 俊行; Angell, C.; 羽島 良一; Ludewigt, B.*; Quiter, B. J.*; 小泉 光生

no journal, , 

準単色レーザーコンプトン$$gamma$$線ビームを用いて、Ta-181原子核の吸収法による共鳴散乱実験を行った。実験は米国デューク大学で行った。中心エネルギー2.28、2.75MeV、半値幅約4%の$$gamma$$線ビームを、Ta-181の吸収ターゲット及び散乱ターゲットに照射し、散乱ターゲットからの共鳴散乱$$gamma$$線を高純度ゲルマニウム検出器を用いて測定した。その結果、これまでの測定値と比べ、約3倍の散乱強度があることがわかった。また、共鳴準位から励起状態への分岐が、エネルギー2.28MeV領域では75%、2.75MeV領域では50%と大きな値であることを明らかにした。本講演では、実験手法及び結果について報告するとともに、準単色レーザーコンプトン$$gamma$$線ビームを用いた非破壊核種分析の今後の計画について紹介する。

口頭

共鳴吸収法を用いたPu-239の磁気双極子遷移強度の測定

静間 俊行; Angell, C.*; 羽島 良一; Ludewigt, B.*; Quiter, B. J.*; 小泉 光生

no journal, , 

準単色レーザーコンプトン$$gamma$$線ビームを用いた核物質の非破壊検知・測定技術開発の一環として、Pu-239原子核の共鳴散乱実験を行った。実験は米国デューク大学で行った。中心エネルギー2.14MeV、半値幅約4%の$$gamma$$線ビームを、Pu-239の吸収ターゲット及び散乱ターゲットに照射し、散乱ターゲットからの共鳴散乱$$gamma$$線を高純度ゲルマニウム検出器を用いて測定した。その結果、励起エネルギー2.12から2.19MeVの平均積分断面積として、13eV barnを得た。また、励起した準位から基底状態と第一励起状態へ脱励起する割合の合計は、全体の0.4であった。このことから、毎秒10$$^{13}$$の強度をもつレーザーコンプトン$$gamma$$線ビームを用いることにより、燃料集合体中のPu-239を、4時間で、3%の測定誤差で分析可能であることがわかった。本講演では、実験手法及び結果について報告するとともに、準単色レーザーコンプトン$$gamma$$線ビームを用いた非破壊核種分析の今後の計画について紹介する。(なお、本研究開発は「核セキュリティ強化等推進事業費補助金」事業の一部である。)

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