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Isomer spectroscopy in $$^{133}$$Ba and high-spin structure of $$^{134}$$Ba

Kaya, L.*; Vogt, A.*; Reiter, P.*; Siciliano, M.*; 清水 則孝*; 宇都野 穣; Wang, H.-K.*; Gargano, A.*; Coraggio, L.*; Itaco, N.*; et al.

Physical Review C, 100(2), p.024323_1 - 024323_18, 2019/08



Downward terrestrial gamma-ray flash observed in a winter thunderstorm

和田 有希*; 榎戸 輝揚*; 中澤 知洋*; 古田 禄大; 湯浅 孝行*; 中村 佳敬*; 森本 健志*; 松元 崇弘*; 牧島 一夫*; 土屋 晴文

Physical Review Letters, 123(6), p.061103_1 - 061103_6, 2019/08

During a winter thunderstorm on 2017 November 24, a strong burst of gamma-rays with energies up to $$sim$$10 MeV was detected coincident with a lightning discharge, by scintillation detectors installed at Kashiwazaki-Kariwa Nuclear Power Plant at sea level in Japan. The burst had a sub-second duration, which is suggestive of photoneutron productions. The leading part of the burst was resolved into four intense gamma-ray bunches, each coincident with a low-frequency radio pulse. These bunches were separated by 0.7$$-$$1.5 ms, with a duration of $$<$$1 ms each. Thus, the present burst may be considered as a "downward" terrestrial gamma-ray flash (TGF), which is analogous to up-going TGFs observed from space. Although the scintillation detectors were heavily saturated by these bunches, the total dose associated with them was successfully measured by ionization chambers, employed by nine monitoring posts surrounding the power plant. From this information and Monte Carlo simulations, the present downward TGF is suggested to have taken place at an altitude of 2500$$pm$$500 m, involving $$8^{+8}_{-4} times10^{18}$$ avalanche electrons with energies above 1 MeV which is comparable to those in up-going TGFs.


Performance of large volume LaBr$$_{3}$$ scintillation detector equipped with specially-designed shield for neutron resonance capture analysis

土屋 晴文; 小泉 光生; 北谷 文人; 原田 秀郎

Nuclear Instruments and Methods in Physics Research A, 932, p.16 - 26, 2019/07

A large-volume ($$phi$$12.0 cm$$times$$12.7 cm) LaBr$$_{3}$$ scintillation detector equipped with a specially-designed radiation shield was evaluated for neutron resonance capture analysis at the neutron time-of-flight (TOF) facility GELINA. By using the LaBr$$_{3}$$ detector with and without the shield, measurements were carried out at a 13-m TOF station with three metallic samples, namely, Ni, Cr, and Fe. In addition, Monte Carlo simulations with Geant4 were performed, and the results were compared with the measurements to analyze the observed energy spectra and TOF spectra. Energy spectra obtained with the shield showed that prompt $$gamma$$-ray peaks emitted from each sample can be used to identify the isotopes. Moreover, the signal-to-noise ratios of resonance peaks in a TOF spectrum with the shield were enhanced 1.5-2.5 in comparison with those without the shield. Furthermore, simultaneous measurements conducted using the three samples demonstrated that the shield employed herein was indispensable for identifying impurities in a composite sample such as particle-like fuel debris.



榎戸 輝揚*; 和田 有希*; 土屋 晴文

日本物理学会誌, 74(4), p.192 - 200, 2019/04



Hydrogen gas measurements of phosphate cement irradiated during heat treatment

入澤 啓太; 工藤 勇*; 谷口 拓海; 並木 仁宏*; 大杉 武史; 中澤 修

QST-M-16; QST Takasaki Annual Report 2017, P. 63, 2019/03



Measurements of gamma-ray emission probabilities in the decay of americium-244g

中村 詔司; 寺田 和司*; 木村 敦; 中尾 太郎*; 岩本 修; 原田 秀郎; 上原 章寛*; 高宮 幸一*; 藤井 俊行*

Journal of Nuclear Science and Technology, 56(1), p.123 - 129, 2019/01

 パーセンタイル:100(Nuclear Science & Technology)



Gamma-ray imaging system for Fukushima Daiichi Nuclear Power Plant using silicon strip detector

冠城 雅晃; 佐藤 優樹; 吉原 有里*; 島添 健次*; 高橋 浩之*; 鳥居 建男

Reactor Dosimetry; 16th International Symposium on Reactor Dosimetry (ISRD-16) (ASTM STP 1608), p.405 - 414, 2018/11

On March 11, 2011, a massive earthquake occurred in the Tohoku region of Japan, and a large tsunami hit the Fukushima Daiichi Nuclear Power Plant (1F), resulting in a nuclear accident. Despite the years that have passed since the accident, decommissioning remains a concern. Radiation measurement techniques are very important for accelerating the decommissioning and ensuring low radiation exposure to workers. Our gamma-ray imaging system is the detection device for determining the three dimensional radioactive distributions of nuclear fuel debris, measuring high-energy gamma rays (greater than 1 MeV). Silicon semiconductor detectors are among the candidate detectors for radiation measurements in our system because of their radiation-hardness and high counting rate capability. We have been developing a stacked amorphous-silicon (Si)/crystal-Si heterojunction Si strip detector, which has 1-mm-pitch striped electrodes (0.5 mm wide) and 1.2-mm-pitch stacked technology. The detector consists of an Si strip mounted on a thin printed circuit board, front-end readout electronics with a complementary metal oxide semiconductor application specific integrated circuit, and a field programmable gate array. The threshold level of energy deposition of each pulse signal in each channel can be set from the application-specific integrated circuit, and gamma-ray images with energy discrimination can be obtained. The energy threshold level for discrimination of $$^{60}$$Co gamma rays from $$^{137}$$Cs gamma rays was investigated experimentally and by means of simulation, and it was found to be about 500 keV. Therefore, our Si strip detector has the required position sensitivity and energy discrimination ability for identifying high-energy gamma-ray source distributions.


Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

和田 有希*; Bowers, G. S.*; 榎戸 輝揚*; 鴨川 仁*; 中村 佳敬*; 森本 健志*; Smith, D.*; 古田 禄大*; 中澤 知洋*; 湯浅 孝行*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

 被引用回数:1 パーセンタイル:53.8(Geosciences, Multidisciplinary)

An on-ground observation program for high energy atmospheric phenomena in winter thunderstorms along Japan Sea has been performed via lightning measurements of $$gamma$$-ray radiation, atmospheric electric field and low-frequency radio band. On February 11, 2017, the radiation detectors recorded $$gamma$$-ray emission lasting for 75 sec. The $$gamma$$-ray spectrum extended up to 20 MeV and was reproduced by a cutoff power-law model with a photon index of 1.36$$^{+0.03}_{-0.04}$$, being consistent with a Bremsstrahlung radiation from a thundercloud (as known as a $$gamma$$-ray glow). Then the $$gamma$$-ray glow was abruptly terminated with a nearby lightning discharge. The low-frequency radio monitors, installed $$sim$$50 km away from Noto School, recorded intra/inter-cloud discharges spreading over $$sim$$60km area with a $$sim$$300 ms duration. The timing of the $$gamma$$-ray termination coincided with the moment when a sequence of intra/inter-cloud discharges passed 0.7 km horizontally away from the radiation monitors. The atmospheric electric-field measurement presented that negative charge was located in the cloud base and not neutralized by the lightning discharge. This indicates that the $$gamma$$-ray source was located at an higher region than the cloud base.


Characterization of phosphate cement irradiated by $$gamma$$-ray during dehydration

入澤 啓太; 工藤 勇*; 谷口 拓海; 並木 仁宏*; 大杉 武史; 中澤 修

QST-M-8; QST Takasaki Annual Report 2016, P. 63, 2018/03

福島第一原子力発電所から発生する汚染水処理二次廃棄物の安全な貯蔵のため、リン酸セメントによる最小含水化した固化技術を開発している。実際の二次廃棄物における本固化技術の適用性を把握するため、脱水中のリン酸セメントを$$^{60}$$Co $$gamma$$線によって照射した。リン酸セメントのG(H$$_{2}$$)は脱水中の時間と共に減少し、7日後に検出下限値となった。さらに、脱水中の$$^{60}$$Co $$gamma$$線照射がリン酸セメントの結晶及び非晶質相を変化させないことが分かった。



武内 伴照; 柴田 裕司; 花川 裕規; 上原 聡明*; 上野 俊二*; 土谷 邦彦; 熊原 肇*; 柴垣 太郎*; 駒野目 裕久*

JAEA-Technology 2017-026, 26 Pages, 2018/02




Release and transport behaviors of non-gamma-emitting fission products and actinides in steam and hydrogen atmospheres

三輪 周平; Ducros, G.*; Hanus, E.*; Bottomley, P. D. W.*; Van Winckel, S.*; 逢坂 正彦

Nuclear Engineering and Design, 326, p.143 - 149, 2018/01

 パーセンタイル:100(Nuclear Science & Technology)



Effects of $$gamma$$ irradiation on the adsorption characteristics of xerogel microcapsules

大西 貴士; 田中 康介; 小山 真一; Ou, L. Y.*; 三村 均*

NEA/NSC/R(2017)3, p.463 - 469, 2017/11

資源の有効利用、廃棄物低減のために、無機イオン交換体(タングストリン酸アンモニウム(AMP)またはフェロシアン化銅(KCuFC))をアルギネートゲルで内包するマイクロカプセル(AWP-ALGまたはKCuFC-ALG)、および、アルギネートゲルそのもの(ALG)を用いた核種分離システムの開発を実施している。ALG, AWP-ALGおよびKCuFC-ALGは、それぞれ、Zr, CsおよびPdを選択的に吸着することが明らかになっている。しかしながら、$$gamma$$線照射に伴う吸着特性の変化については、十分に調べられていない。そこで、$$^{60}$$Co線源によって$$gamma$$線を3898kGyまで照射した後、各種マイクロカプセルの吸着特性を評価した。その結果、AWP-ALGまたはKCuFC-ALGは、内包する無機イオン交換体によってCsまたはPdを吸着するため、$$gamma$$線照射を通して吸着特性に変化は見られなかった。一方、ALGは$$gamma$$線照射に伴って放射線分解が進行し、Zrに対する吸着特性が低下した。


Photonuclear reactions triggered by lightning discharge

榎戸 輝揚*; 和田 有希*; 古田 禄大*; 中澤 知洋*; 湯浅 孝行*; 奥田 和史*; 牧島 一夫*; 佐藤 光輝*; 佐藤 陽祐*; 中野 俊男*; et al.

Nature, 551(7681), p.481 - 484, 2017/11

 被引用回数:26 パーセンタイル:3.91(Multidisciplinary Sciences)

Relativistic electrons accelerated by electric fields of lightnings and thunderclouds emit bremsstrahlung $$gamma$$ rays, which have been detected at ground observations. The energy of the $$gamma$$ rays is sufficiently high to potentially invoke atmospheric photonuclear reactions $$^{14}$$N($$gamma$$, n)$$^{13}$$N, which would produce neutrons and eventually positrons via $$beta^{+}$$ decay of generated unstable radioactive isotopes, especially $$^{13}$$N. However, no clear observational evidence for the reaction has been reported to date. Here we report the first detection of neutron and positron signals from lightning with a ground observation. During a thunderstorm on 6 February 2017 in Japan, an intense $$gamma$$-ray flash ($$<$$1 ms) was detected at our monitoring sites. The subsequent initial burst quickly subsided with an exponential decay constant of 40-60 ms, followed by a prolonged line emission at $$sim$$0.511MeV, lasting for a minute. The observed decay timescale and spectral cutoff at $$sim$$10 MeV of the initial emission are well explained with de-excitation $$gamma$$ rays from the nuclei excited by neutron capture. The centre energy of the prolonged line emission corresponds to the electron-positron annihilation, and hence is the conclusive indication of positrons produced after the lightning. Our detection of neutrons and positrons is unequivocal evidence that natural lightning triggers photonuclear reactions.


Establishment of a Laboratory for $$gamma$$-ray Spectrometry of Environmental Samples Collected in Fukushima

三枝 純; 依田 朋之; 前田 智史; 岡崎 勤; 大谷 周一; 山口 敏夫; 栗田 義幸; 波澄 篤; 米澤 仲四郎*; 武石 稔

Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1078 - 1085, 2017/11

2011年3月の福島第一原子力発電所の事故後、原子力機構は新たに放射能分析施設を福島に立ち上げた。分析施設では高分解能$$gamma$$線スペクトロメトリに基づき、土壌や水、ダストフィルタ、植物といった環境試料の放射能分析を月当たり約1,000件のペースで行っている。2012年9月の施設立上げ以来、分析結果の信頼性や、分析依頼者及び機器オペレータの利便性向上を目指した技術開発を実施し、制度的・技術的な課題を継続的に改善することで、ISO/IEC 17025規格に適合する試験所としての認定を得た。


Cross-shell excitations from the $$fp$$ shell; Lifetime measurements in $$^{61}$$Zn

Queiser, M.*; Vogt, A.*; Seidlitz, M.*; Reiter, P.*; 富樫 智章*; 清水 則孝*; 宇都野 穣; 大塚 孝治*; 本間 道雄*; Petkov, P.*; et al.

Physical Review C, 96(4), p.044313_1 - 044313_13, 2017/10

 被引用回数:1 パーセンタイル:100(Physics, Nuclear)



In-beam $$gamma$$-ray spectroscopy of $$^{35}$$Mg via knockout reactions at intermediate energies

籾山 悟至*; Doornenbal, P.*; Scheit, H.*; 武内 聡*; 新倉 潤*; 青井 考*; Li, K.*; 松下 昌史*; Steppenbeck, D.*; Wang, H.*; et al.

Physical Review C, 96(3), p.034328_1 - 034328_8, 2017/09

 被引用回数:2 パーセンタイル:72.32(Physics, Nuclear)

理化学研究所の不安定核実験施設RIBFにて、中性子過剰核$$^{35}$$Mgの励起状態を$$^{36}$$Mgおよび$$^{37}$$Alからのノックアウト反応によって生成し、そこからの脱励起$$gamma$$線を観測した。$$^{35}$$Mgは中性子数20魔法数が消滅するとされる「逆転の島」と呼ばれる領域に含まれると考えられており、また、奇核であることから、一粒子状態と集団的状態が結合した興味深い核構造が出現すると期待されている。この実験によって、206keV, 443keV, 616keV, 670keVの4本の$$gamma$$線を観測し、これらを全て基底状態へ脱励起する$$gamma$$線であると仮定して励起準位を構成した。この準位構造、ノックアウト反応の断面積、移行運動量分布を殻模型計算および反対称化分子動力学計算と比較した。二つの計算は、基底状態近傍の高い準位密度などいくつかの特徴的な核構造を再現することに成功し、$$^{35}$$Mgは「逆転の島」に含まれるという描像と無矛盾であることがわかった。


$$gamma$$-ray spectroscopy of hypernuclei; Recent results and prospect at J-PARC

田村 裕和*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.011004_1 - 011004_11, 2017/07

The present status and future prospects of precision $$gamma$$-ray spectroscopy of $$Lambda$$ hypernuclei are described. A new experiment (J-PARC E13) has been performed at the J-PARC K1.8 line employing a newly-developed germanium (Ge) detector array, Hyperball-J, via the $$(K^-,pi^-)$$ reaction on $$^4$$He and $$^{19}$$F targets. This is the first study of $$s$$-shell and $$sd$$-shell $$Lambda$$ hypernuclei with Ge detectors. The $$^4$$He target spectrum exhibited a $$gamma$$-ray peak of $$^4_{Lambda}{rm He}(1^+to 0^+)$$ at $$1.406 pm 0.002 pm 0.002$$ MeV. Compared with the energy ($$1.09 pm 0.02$$ MeV) of the corresponding transition for the mirror hypernucleus, $$^4_{Lambda}{rm H}(1^+to 0^+)$$, the present result clearly indicates a large charge symmetry breaking (CSB) effect. This decisive data for CSB allows a stringent test of baryon-baryon interaction models. As for the $$^{19}$$F target run, a preliminary spectrum shows several $$gamma$$-ray peaks assigned to $$^{19}_{Lambda}{rm F}$$ transitions. Future plans of $$gamma$$-ray spectroscopy are also discussed.


The First gamma-ray spectroscopic study of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012004_1 - 012004_4, 2017/07

The first $$gamma$$-ray spectroscopy of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F, is performed in June, 2015 at the J-PARC K1.8 beam line (J-PARC E13). Precise energy levels of $$^{19}_{Lambda}$$F can be revealed by measured $$gamma$$ rays in this experiment. Especially, the strength of $$Lambda N$$ spin-spin interaction in $$sd$$-shell hypernucleus is obtained through the energy spacing of the ground-state doublet of the hypernucleus. By comparing its strength between the $$s$$, $$p$$, and $$sd$$-shell hypernuclei, a radial dependence $$Lambda N$$ interaction is investigated. The hypernucleus is produced through the $$(K^-,pi^-)$$ reaction with the beam momentum of 1.8 GeV/c. In very preliminary results, we observed two $$gamma$$ rays, and their energies are $$315.8 pm 0.4$$ keV and $$ 895.3 pm 0.3$$ keV where the uncertainties are only statistical.


Development of a correction method for the time-of-flight prompt $$gamma$$-ray analysis

Huang, M.; 藤 暢輔; 海老原 充*; 木村 敦; 中村 詔司

Journal of Applied Physics, 121(10), p.104901_1 - 104901_7, 2017/03

 パーセンタイル:100(Physics, Applied)

A new analytical technique, time-of-flight prompt $$gamma$$-ray analysis, has been developed at the Japan Proton Accelerator Research Complex. In order to apply it to accurate elemental analysis, a set of standard Fe and Au samples were measured to examine the factors which affect the number of detected events. It was found that the main contributing factors included the attenuations of neutrons and $$gamma$$ rays in the sample, live-time ratio of the data acquisition system and signal pile-up correction factor. A simulation model was built for the estimations of neutron and $$gamma$$-ray attenuations. A simple empirical formula was proposed to calculate the signal pile-up correction factor. The whole correction method has proven to be accurate and reliable.



瀬谷 道夫; 羽島 良一*; 呉田 昌俊

第37回核物質管理学会日本支部年次大会論文集(CD-ROM), 10 Pages, 2017/02


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