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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

Simulation of the elastic scattering contributions to the NRF-based nondestructive assay of nuclear materials

Omer, M.; 羽島 良一*; Angell, C.*; 静間 俊行*; 早川 岳人*; 瀬谷 道夫; 小泉 光生

Proceedings of INMM 57th Annual Meeting (Internet), 9 Pages, 2016/07

核種の核共鳴蛍光反応過程で放出される核種固有の$$gamma$$線は、核物質の非破壊検知及び測定の非常に良い方法を提供する。われわれは、$$gamma$$線非破壊検知及び測定に関連する技術を開発している。核共鳴蛍光反応をシミュレートするモンテ・カルロコードは非破壊測定装置の設計及び評価において不可欠なものである。われわれは、そのため、Geant4コードをベースとするシミュレーションコードNRFGeant4を開発している。核共鳴蛍光反応実験においては、一般に高濃度測定対象物が使われる。この場合は核共鳴蛍光反応$$gamma$$線が強く、測定しやすいためである。それに対して実際の状況では、測定したい(興味のある)核種が小さい組成比でしか含まれていないことがある。このような状況では、核共鳴蛍光反応$$gamma$$線の測定が、他の反応(例として、(核共鳴反応と同じような)弾性散乱)からの影響を受けて困難となる。例えば、典型的な核燃料のペレットは90%程度の$$^{238}$$Uを母材として含むが、測定対象として興味のある$$^{239}$$Puは約1%以下の割合でしか含まれていない。このような場合、$$^{239}$$Puからの核共鳴蛍光$$gamma$$線の測定においては、$$^{238}$$Uの弾性散乱からの強い$$gamma$$線バックグランドが発生することとなる。それゆえ、母材の弾性散乱($$gamma$$線)強度を評価することは、測定しようとする(興味のある)核種の正確な測定においては不可欠なこととなる。現段階においては、弾性散乱の満足のゆく評価は(ある計算を除いて)できていない。われわれのこの研究では、弾性散乱事象を取込むように、シミュレーションコードの高度化を行っている。

論文

Enabling ${{it in situ }}$ thermometry using transmission nuclear resonance fluorescence

Angell, C.

Nuclear Instruments and Methods in Physics Research B, 368, p.9 - 14, 2016/02

 被引用回数:2 パーセンタイル:19.85(Instruments & Instrumentation)

Transmission nuclear resonance fluorescence (NRF) has been proposed for use as an assay and detection technique for nuclear security and safeguards applications because of its isotope-specific sensitivity and the penetrating capability of $$gamma$$-rays. It can also be used for in situ thermometry because the absorbing resonance profile is sensitive to temperature. Using transmission NRF for thermometry could provide a new avenue for studying the ion temperature evolution of laser-induced plasmas using the upcoming ELI-NP facility. It could also be used for applications where thermometry would be otherwise infeasible, such as for determining the average fuel temperature of spent nuclear fuel, a step that would reduce the assay uncertainty using transmission NRF. Beyond thermometry, an application of temperature effects was found in the improvement of transmission NRF efficacy for assay and detection: using a cryogenic witness target will reduce the required measurement time by 40%.

論文

Corrigendum; Pulse pileup correction in the presence of a large low-energy background [J. Nucl. Sci. Technol. 2015; 52: 426-433]

Angell, C.

Journal of Nuclear Science and Technology, 52(9), P. 1205, 2015/09

 被引用回数:0 パーセンタイル:2.27(Nuclear Science & Technology)

The present manuscript is an corrigendum to a previously published paper "Pulse pileup correction in the presence of a large low-energy background" [J. Nucl. Sci. Technol. 2015; 52: 426-433].

論文

レーザー・コンプトン散乱による高輝度$$gamma$$線の実現とその利用

羽島 良一; 沢村 勝; 永井 良治; 西森 信行; 早川 岳人; 静間 俊行; Angell, C.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.79 - 83, 2015/09

レーザー・コンプトン散乱で発生する$$gamma$$線は、エネルギー可変かつ狭帯域の特徴を有する。電子加速器とレーザーの先端技術を組み合わせることで、高輝度$$gamma$$線源を実現することができる。このような高輝度$$gamma$$線源は、核物質の非破壊測定をはじめとした産業利用、原子核物理の基礎研究に革新的な進歩をもたらすと期待されている。ヨーロッパでは、次世代$$gamma$$線源としてELI-NPの建設が始まっており、2018年の運転開始の予定である。われわれは、エネルギー回収型リニアック(ERL)を用いることで、ELI-NPを超える輝度、強度を持った$$gamma$$線源を提案しており、基盤技術の開発を行っている。本発表では、ERLに基づくレーザー・コンプトン散乱$$gamma$$線源の特徴、産業利用、学術利用の展開について述べる。

論文

R&D status of nondestructive assay system based on nuclear resonance fluorescence

静間 俊行; 羽島 良一; 早川 岳人; Angell, C.; 瀬谷 道夫

Proceedings of 37th ESARDA Annual Meeting (Internet), p.838 - 845, 2015/08

核物質の非破壊分析は核セキュリティーや保障措置において重要な技術である。原子力機構核種分析研究グループでは核共鳴蛍光散乱を用いた非破壊分析システムを提案している。核共鳴蛍光散乱を用いることにより、非破壊で核種を同定することが可能となる。我々が提案する検出システムでは、レーザー光と高エネルギー電子とのコンプトン散乱によって生成されるエネルギー可変で単色の$$gamma$$線ビームを使用する。単色$$gamma$$線ビームを用いることにより、効率よく共鳴散乱$$gamma$$線を測定することが可能となる。エネルギー回収型リニアックを用いたコンプトン$$gamma$$線生成の実証試験、検出システムの確立やモンテカルロシミュレーションを用いたベンチマーク等の技術開発を開始しており、本シンポジウムでは、コンプトン$$gamma$$線生成及び測定原理の実証実験の結果について報告する。

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

Diffraction of $$gamma$$-rays with energies of 1.17 and 1.33 MeV by a flat Si crystal

松葉 俊哉*; 早川 岳人; 静間 俊行; 西森 信行; 永井 良治; 沢村 勝; Angell, C.; 藤原 守; 羽島 良一

Japanese Journal of Applied Physics, 54(5), p.052203_1 - 052203_5, 2015/05

 被引用回数:3 パーセンタイル:13.97(Physics, Applied)

Diffraction of $$gamma$$-rays by a flat Si crystal has been demonstrated using a high flux $$^{60}$$Co source with an intensity of 2.3 TBq. The diffraction intensities of the $$gamma$$-rays with energies of 1.17 and 1.33 MeV have been measured as a function of the rotation angle of the crystal. Three peaks corresponding to the Si(440) and Si(220) diffractions for 1.17 MeV and the Si(440) diffraction for 1.33 MeV have been measured. The heights and shapes of these three peaks are well reproduced by taking into account Bragg's law and the experimental geometry.

論文

Method for determining individual deposition velocities of radon progeny

Angell, C.; Pedretti, M.*; Norman, E. B.*

Applied Radiation and Isotopes, 98, p.34 - 39, 2015/04

 被引用回数:2 パーセンタイル:17.75(Chemistry, Inorganic & Nuclear)

The deposition velocity of radon progeny is used to model the removal of progeny from the air by surfaces in assessing indoor air quality. The deposition velocity can also be used to assess radon-induced background in sensitive, low-background experiments. Typically, a single value of the deposition velocity issued for all radon progeny. This manuscript presents an experimental method for uniquely determining the deposition velocity of each chemical species of radon progeny and demonstrates that the deposition velocities are different for Po, Pb, and, in principle, for Bi as well, and can vary depending on the surface material.

論文

Pulse pileup correction in the presence of a large low-energy background

Angell, C.

Journal of Nuclear Science and Technology, 52(3), p.426 - 433, 2015/03

 被引用回数:4 パーセンタイル:33.51(Nuclear Science & Technology)

Pulse pileup correction is required for high count rate experiments. Spectral distortion due to pileup is strongly affected by the distribution of pulse heights. Methods used to limit the digitization rate-including energy thresholds and coincidence requirements-adversely affect attempts to correct the pileup-induced distortion. A simplified method for correcting the spectral distortion using a general pileup function can be used when the spectrum is dominated by a low-energy background. This method has particular relevance for nuclear resonance fluorescence experiments.

論文

Demonstration of a transmission nuclear resonance fluorescence measurement for a realistic radioactive waste canister scenario

Angell, C.; 羽島 良一; 早川 岳人; 静間 俊行; Karwowski, H.*; Silano, J.*

Nuclear Instruments and Methods in Physics Research B, 347, p.11 - 19, 2015/03

 被引用回数:10 パーセンタイル:67.6(Instruments & Instrumentation)

Transmission nuclear resonance fluorescence (NRF) is a promising method for precision non-destructive assay (NDA) of fissile isotopes including $$^{239}$$Pu in spent fuel while inside a storage canister. The assay, however, could be confounded by the presence of overlapping resonances from competing isotopes in the canister. A measurement is needed to demonstrate that transmission NRF is unaffected by the shielding material. To this end, we carried out a transmission NRF measurement using a mono-energetic $$gamma$$-ray beam on a proxy target (Al) and absorbing material simulating a realistic spent fuel storage canister. Similar amounts of material as would be found in a possible spent fuel storage canister were placed upstream: concrete, stainless steel (SS 304), lead (as a proxy for U), and water. An Al absorption target was also used as a reference. These measurements demonstrated that the canister material should not significantly influence the non-destructive assay.

論文

Erratum; Evidence for radiative coupling of the pygmy dipole resonance to excited states [Phys. Rev. C 86, 051302(R) (2012)]

Angell, C.; Hammond, S. L.*; Karwowski, H. J.*; Kelley, J. H.*; Krti$v{c}$ka, M.*; Kwan, E.*; 牧永 あや乃*; Rusev, G.*

Physical Review C, 91(3), p.039901_1 - 039901_2, 2015/03

AA2014-0872.pdf:0.1MB

 被引用回数:5 パーセンタイル:74.67(Physics, Nuclear)

The present manuscript is an erratum to a previously published paper "Evidence for radiative coupling of the pygmy dipole resonance to excited states" [Phys. Rev. C 86, 051302(R) (2012)].

論文

レーザー・コンプトン散乱による$$gamma$$線NDAの技術開発の現状

羽島 良一; 静間 俊行; 永井 良治; 森 道昭; 早川 岳人; Angell, C.; 瀬谷 道夫

核物質管理学会(INMM)日本支部第35回年次大会論文集(インターネット), 7 Pages, 2015/01

日本原子力研究開発機構は、レーザー・コンプトン散乱(LCS)で生成する大強度単色$$gamma$$線(LCS $$gamma$$線)と原子核共鳴蛍光散乱(NRF)による核種の非破壊測定を提案し、これに必要な基盤技術開発を行っている。平成26年度は、4年間の技術開発プログラムの最終年度としてLCS $$gamma$$線の発生実証試験(実証試験)をコンパクトERL(ERL試験加速器)にて実施する予定であり、高エネルギー加速器研究機構の協力のもと、実証試験の準備を進めている。コンパクトERLは2014年3月12日に完成検査に合格し、同6月20日までの運転では実証試験に向けた電子ビーム調整などを行った。2014年7月から12月までの加速器の停止期間中にLCS用レーザー、電子・レーザー衝突用真空容器、ビームライン、LCS $$gamma$$線測定装置などの設置を行い、2015年1月以降に実証試験を開始する。本発表では、これら、(LCS $$gamma$$線の発生)実証試験に向けた準備状況を報告する。

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

Validating resonance properties using nuclear resonance fluorescence

Angell, C.; 羽島 良一; 早川 岳人; 静間 俊行; Karwowski, H.*; Silano, J.*

Physical Review C, 90(5), p.054315_1 - 054315_6, 2014/11

AA2014-0567.pdf:0.3MB

 被引用回数:6 パーセンタイル:43.07(Physics, Nuclear)

Measurement of a resonance's integrated cross section using nuclear resonance fluorescence can be a valuable tool for verifying the properties of the resonance because of the clear and unambiguous physical connection to the spin, lifetime, and ground state branching ratio of the level. We demonstrate this idea by measuring the integrated cross section of the 3.004 MeV level in $$^{27}$$Al to 4% using the mono-energetic $$gamma$$-ray beam at the High Intensity $$gamma$$-ray Source. That level was the subject of much debate experimentally in the 1960's, especially its spin, and even now only has a current tentative spin assignment of $$J=(9/2)$$. The consistency check between this integrated cross section and the known properties of the level indicate that one (or more)of the literature properties is incorrect. Based on the range of extent of each property, a re-assignment of spin to atentative $$J=(7/2)$$ may be warranted, but this would need to be confirmed with other measurements. This result demonstrates the utility of NRF as a way to verify the properties of states in the literature before undertaking more extensive measurements.

論文

Spectroscopy of $$^{153}$$Gd and $$^{157}$$Gd using the ($$p,d gamma$$) reaction

Ross, T. J.*; Hughes, R. O.*; Allmond, J. M.*; Beausang, C. W.*; Angell, C.; Basunia, M. S.*; Bleuel, D. L.*; Hurke, J. T.*; Casperson, R. J.*; Escher, J. E.*; et al.

Physical Review C, 90(4), p.044323_1 - 044323_12, 2014/10

 被引用回数:7 パーセンタイル:47.25(Physics, Nuclear)

Low-spin single quasi neutron levels in $$^{153}$$Gd and $$^{157}$$Gd have been studied following the $$^{154}$$Gd ($$p,d gamma$$) $$^{153}$$Gd and $$^{158}$$Gd ($$p,d gamma$$) $$^{157}$$Gd reactions. A combined Si telescope and high-purity germanium array was utilized, allowing $$d$$-$$gamma$$ and $$d$$-$$gamma$$-$$gamma$$ coincidence measurements. Almost all of the established low-excitation-energy, low-spin structures were confirmed in both $$^{153}$$Gd and $$^{157}$$Gd. Several new levels and numerous new $$gamma$$ rays are observed in both nuclei, particularly for $$Ex$$ $$geq$$ 1 MeV. Residual effects of a neutron sub shell closure at $$N$$ = 64 are observed in the form of a large excitation energy gap in the single quasi neutron level schemes.

論文

Erratum; "Concepts in nuclear science illustrated through experiments with radon" [Am. J. Phys. 80, 61-65 (2012)]

Angell, C.; Kaplan, A.*; Seelig, J. D.*; Norman, E. B.*; Pedretti, M.*

American Journal of Physics, 82(8), P. 802, 2014/08

 被引用回数:0 パーセンタイル:2.17(Education, Scientific Disciplines)

The present manuscript is an addendum to a previously published paper "Concepts in nuclear science illustrated through experiments with radon" [Am. J. Phys. 80, 61-65 (2012)].

論文

Improvement to the semi-empirical germanium detector response model at the Compton edge

Angell, C.

Nuclear Instruments and Methods in Physics Research A, 752, p.33 - 35, 2014/07

 被引用回数:4 パーセンタイル:33.13(Instruments & Instrumentation)

An accurate detector response model is needed for extracting broad distributions of $$gamma$$-rays incident on a detector. Current analytical detector-response models for HPGe detectors systematically vary from experimental spectra in the region of the Compton edge. In this work, we introduce new terms for the Compton edge in the semi-empirical detector response model, an analytical model for HPGe detectors, which produces better agreement at the Compton edge and broadens the model's applicability to a wider range of detector geometries.

論文

Application of laser Compton scattered $$gamma$$-ray beams to nondestructive detection and assay of nuclear material

羽島 良一; 早川 岳人; 静間 俊行; Angell, C.; 永井 良治; 西森 信行; 沢村 勝; 松葉 俊哉; 小菅 淳*; 森 道昭; et al.

European Physical Journal; Special Topics, 223(6), p.1229 - 1236, 2014/05

 被引用回数:17 パーセンタイル:49.18(Physics, Multidisciplinary)

Generation of energy-tunable $$gamma$$-rays via laser Compton scattering is of great interest for applications of MeV photons -which interact with nuclei- and scientific studies. One of the promising applications of such energy-tunable $$gamma$$-rays is the nondestructive detection and assay of nuclides, which are necessary for nuclear security and safeguards. We are developing technologies relevant to $$gamma$$-ray nondestructive detection and assay, which include a high-brightness $$gamma$$-ray source based on modern laser and accelerator technologies, and $$gamma$$-ray measurement methods optimized for highly radioactive samples.

論文

Statistical uncertainties of nondestructive assay for spent nuclear fuel by using nuclear resonance fluorescence

静間 俊行; 早川 岳人; Angell, C.; 羽島 良一; 湊 太志; 須山 賢也; 瀬谷 道夫; Johnson, M.*; McNabb, D.*

Nuclear Instruments and Methods in Physics Research A, 737, p.170 - 175, 2014/02

 被引用回数:1 パーセンタイル:10.27(Instruments & Instrumentation)

大強度単色光源を用いた核共鳴散乱による低濃度アクチナイド核種を含む使用済み核燃料の非破壊分析における統計誤差の評価を行った。ORIGEN2.2-UPJ燃焼コードを用いて使用済み核燃料からの放射強度を計算し、バックグラウンド計数を求めた。また、レーリー散乱,核トムソン散乱,デルブルック散乱からのコヒーレント散乱によるバックグラウンドも考慮した。コヒーレント散乱による$$gamma$$線エネルギーは、共鳴散乱$$gamma$$線のエネルギーと一致するため、第一励起状態への遷移$$gamma$$線を測定する方法を提案する。励起エネルギー2.25, 3.5, and 5MeVにおいて、3から100eV$$cdot$$bの全共鳴散乱断面積を仮定して、共鳴散乱$$gamma$$線測定の統計誤差を見積もった。その結果、毎秒10$$^6$$個の強度をもつ$$gamma$$線ビームを用いて、3.5から5MeVの励起エネルギーにおける全積分断面積30eV$$cdot$$bをもつ共鳴散乱に対して、4000秒の測定時間で2.2から3.2%の統計誤差で、使用済み核燃料中の1%のアクチナイド核種を分析できることがわかった。

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