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Journal Articles

Valence control of charge and orbital frustrated system YbFe$$_{2}$$O$$_{4}$$ with electrochemical Li$$^{+}$$ intercalation

Murase, Satoshi*; Yoshikawa, Yumi*; Fujiwara, Kosuke*; Fukada, Yukimasa*; Teranishi, Takashi*; Kano, Jun*; Fujii, Tatsuo*; Inada, Yasuhiro*; Katayama, Misaki*; Yoshii, Kenji; et al.

Journal of Physics and Chemistry of Solids, 162, p.110468_1 - 110468_6, 2022/03

We report a trial of the valence control for mixed valence iron triangular oxide YbFe$$_{2}$$O$$_{4}$$ in order to develop an effective technique to control the frustration of charges in strongly correlated electron systems. The electro-chemical doping of Li$$^{+}$$ into YbFe$$_{2}$$O$$_{4}$$ was examined on the cell type sample similar to the Li-ion secondary battery cell. Systematic change of the lattice constant, Fe-Fe and Fe-Yb distance were observed with Li doping. Maximum value of the doping was over 300 mAh/g. An EXAFS experiment indicated that Li positioned between Yb octahedron layer (U-layer) and Fe-bipyramidal layer (W-layer). However, detailed change of iron valence state of YbFe$$_{2}$$O$$_{4}$$ was not clearly observed because of the superimpose of the signal from iron metal nano particles in XANES observation. The results indicate that the electrochemical method might be one of the potential technique to control the frustration of charges in YbFe$$_{2}$$O$$_{4}$$.

Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:9 Percentile:88.96(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

High oxide-ion conductivity in Si-deficient La$$_{9.565}$$(Si$$_{5.826}$$[]$$_{0.174}$$)O$$_{26}$$ apatite without interstitial oxygens due to the overbonded channel oxygens

Fujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi

Journal of Materials Chemistry A, 6(23), p.10835 - 10846, 2018/06

 Times Cited Count:12 Percentile:61.53(Chemistry, Physical)

Journal Articles

Report on OPIC Laser Solutions for Space and the Earth (LSSE 2017)

Ebisuzaki, Toshikazu*; Wada, Satoshi*; Saito, Norihito*; Fujii, Takashi*; Nishimura, Akihiko

Reza Kenkyu, 45(10), p.664 - 665, 2017/10

no abstracts in English

Journal Articles

Simulation of discharge in insulating gas from initial partial discharge to growth of a stepped leader using the percolation model

Sasaki, Akira; Kato, Susumu*; Takahashi, Eiichi*; Kishimoto, Yasuaki*; Fujii, Takashi*; Kanazawa, Seiji*

Japanese Journal of Applied Physics, 55(2), p.026101_1 - 026101_10, 2016/02

 Times Cited Count:2 Percentile:12.91(Physics, Applied)

A percolation model of discharge, which can reproduce stochastic behaviors of initial partial discharge to the growth of a stepped leader, is presented. The model uses macroscopic cells, from which a network of electric circuits is defined, and the spatial and temporal evolutions of the electric field and current in the discharge medium are calculated. For each cell, one of two states, either insulator or conductor, which corresponds to neutral gas or ionized plasmas, respectively, is decided. The decision is made on the basis of probability for each calculation cell at each time step, taking the effects of local electric field and current, which enhance ionization and sustain the discharge channel, respectively, into account. The stochastic behavior of discharge is discussed, in conjunction with the characteristic feature of ionization, that is, the ionization occurs not only ahead of the streamer tip where the electric field is enhanced but randomly in the discharge medium.

Journal Articles

Electronic structure of BaFeO$$_{3}$$ studied by X-ray spectroscopy

Mizumaki, Masaichiro*; Fujii, Hitoshi*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Uozumi, Takayuki*; Takano, Mikio*

Physica Status Solidi (C), 12(6), p.818 - 821, 2015/06

 Times Cited Count:8 Percentile:94.79

We investigated the electronic structure of BaFeO$$_{3}$$ by using HAXPES and XAS measurements and first principle studies. The experimental and theoretical results indicated that BaFeO$$_{3}$$ is a negative charge transfer compound. We concluded that the on-site Coulomb energy and the strong hybridization between Fe-3d and O-2p orbitals play a very important role of emergence of negative charge transfer. And we found the new structure in the Fe-2p XPS spectrum and concluded this structure is originated from non-local screening.

Journal Articles

Cross section measurements of the radioactive $$^{107}$$Pd and stable $$^{105,108}$$Pd nuclei at J-PARC/MLF/ANNRI

Nakamura, Shoji; Kimura, Atsushi; Kitatani, Fumito; Ota, Masayuki; Furutaka, Kazuyoshi; Goko, Shinji*; Hara, Kaoru; Harada, Hideo; Hirose, Kentaro; Kin, Tadahiro*; et al.

Nuclear Data Sheets, 119, p.143 - 146, 2014/05

 Times Cited Count:8 Percentile:56.03(Physics, Nuclear)

We have started the measurements of the neutron-capture cross sections for stable $$^{105,108}$$Pd nuclei as well as the radioactive $$^{107}$$Pd. The neutron-capture cross-section measurements by the time-of flight method were performed using an apparatus called "Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI)" installed at the neutron Beam Line No.4 of the Materials and Life science experimental Facility (MLF) in the J-PARC. The neutron-capture cross sections of $$^{107}$$Pd and $$^{105,108}$$Pd have been measured in the neutron energy range from thermal to 300 eV. Some new information was obtained for resonances of these Pd nuclei.

Journal Articles

Electrode properties of Li$$_{2}$$MnO$$_{3}$$ (${it C}$2/${it m}$) for a lithium-battery cathode in several charge-discharge potential ranges

Nakao, Yasuhiro*; Ozawa, Kiyoshi*; Fujii, Hiroki*; Mochiku, Takashi*; Iwai, Hideo*; Tsuchiya, Yoshinori*; Igawa, Naoki

Transactions of the Materials Research Society of Japan, 38(2), p.229 - 233, 2013/12

Li$$_{2}$$MnO$$_{3}$$ powder with a monoclinic cell related to the space group of ${it C}$2/${it m}$ was synthesized by a simplified coprecipitation method. Its electrode properties as a lithium-battery cathode were investigated in the charge-discharge potential ranges of 2.0 - 4.6, 2.0 - 4.8, and 2.0 - 5.0 V. In all the potential ranges, the electrochemical capacities gradually increased during cycling, and the increased capacities significantly depended on the potential ranges. Compared to the discharge capacities for the potential ranges of 2.0 - 4.6 and 2.0 - 5.0 V, the former merely increased from 12.5 to 22.5 mAhg$$^{-1}$$ between the 1st and 99th cycles, whereas the latter increased from 20.0 to 110.2 mAhg$$^{-1}$$ during the same cycling. The structural variation in Li$$_{2}$$MnO$$_{3}$$ is induced by the cycling, the rhombohedral phase is detected during cycling in the potential range of 2.0 - 5.0 V.

Journal Articles

Evaluation of protection factors of a breath-responsive-powered air-purifying respirator

Nakagawa, Masahiro; Nojima, Shun; Fujii, Katsutoshi; Shishido, Nobuhito; Sakai, Toshiya; Umehara, Takashi; Shimizu, Isamu

Hoken Butsuri, 47(3), p.189 - 193, 2012/10

It is essential to wear an air-purifying respirator in the radiation works in a contaminated atmosphere. A breath-responsive-powered air-purifying respirator (BR-PAPR) has been recently developed. However, no research has yet been conducted to determine the protection factor (PF) of the BR-PAPR in actual workplaces. In this study, the PFs of the BR-PAPR were measured by a man-test apparatus and compared with those of a non-powered full face mask. The PFs were measured under three different situations; normal wearing condition, clogging the filter and leaving a gap between the face and the mask. Under these situations, it was found that the PFs of the BR-PAPR are higher than those of the non-powered full face mask. PFs greater than 4000 were obtained for 95% of the subjects who wear the BR-PAPR, and PFs over 6667, the upper limit of the man-test apparatus, were obtained for 49% of them. The questionnaire survey was conducted for workers. The results showed that the workers feel a reduced burden when they wear the BR-PAPR. The results of this study showed high protection performance and operation efficiency of the BR-PAPR.

Journal Articles

Neutron-capture cross-sections of $$^{244}$$Cm and $$^{246}$$Cm measured with an array of large germanium detectors in the ANNRI at J-PARC/MLF

Kimura, Atsushi; Fujii, Toshiyuki*; Fukutani, Satoshi*; Furutaka, Kazuyoshi; Goko, Shinji*; Hara, Kaoru; Harada, Hideo; Hirose, Kentaro; Hori, Junichi*; Igashira, Masayuki*; et al.

Journal of Nuclear Science and Technology, 49(7-8), p.708 - 724, 2012/07

 Times Cited Count:42 Percentile:96.69(Nuclear Science & Technology)

Journal Articles

Complementary characterization of radioactivity produced by repetitive laser-driven proton beam using shot-to-shot proton spectral measurement and direct activation measurement

Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.

Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04

 Times Cited Count:2 Percentile:10.01(Physics, Applied)

A proton beam driven by a repetitive high-intensity-laser is utilized to induce a $$^{7}$$Li(p,n)$$^{7}$$Be nuclear reaction. The total activity of $$^{7}$$Be are evaluated by two different methods. The activity obtained measuring the decay $$gamma$$-rays after 1912 shots at 1 Hz is 1.7$$pm$$0.2 Bq. This is in good agreement with 1.6$$pm$$0.3 Bq evaluated from the proton energy distribution measured using a time-of-flight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with a high-speed signal processing system.

Journal Articles

Electrochemical characteristics of layered Li$$_{1.95}$$Mn$$_{0.9}$$Co$$_{0.15}$$O$$_{3}$$ (${it C}$2/${it m}$) as a lithium-battery cathode

Ozawa, Kiyoshi*; Nakao, Yasuhiro*; Mochiku, Takashi*; Cheng, Z.*; Wang, L.*; Iwai, Hideo*; Tsuchiya, Yoshinori*; Fujii, Hiroki*; Igawa, Naoki

Journal of the Electrochemical Society, 159(3), p.A300 - A304, 2012/01

 Times Cited Count:13 Percentile:49.71(Electrochemistry)

A manganese-based solid solution with the composition of Li$$_{1.95}$$Mn$$_{0.9}$$Co$$_{0.15}$$O$$_{3}$$ was synthesized by a simplified coprecipitation method, and its electrochemical characteristics as a lithium-battery cathode were investigated. Rietveld refinement based on neutron diffraction data revealed that the material is assigned to an Li$$_{2}$$MnO$$_{3}$$-type structure model with a space group symmetry of ${it C}$2/${it m}$. In cycling of the cell in the potential range from 2.0 to 4.8 V at current densities of 30 mAhg$$^{-1}$$, the discharge capacity characteristically increases from 46.3 to 196.5 mAhg$$^{-1}$$ as the cycle increases from 1 to 11, and a discharge capacity above 175.5 mAhg$$^{-1}$$ is obtained between the 23rd and 58th cycles. The cyclic voltammogram and X-ray photoelectron spectroscopy measurements showed that the manganese redox reaction is progressively activated during the first ten-odd cycles.

Journal Articles

Measurements of neutron capture cross sections at J-PARC/MLF/ANNRI, 2

Hori, Junichi*; Fujii, Toshiyuki*; Fukutani, Satoshi*; Furusaka, Michihiro*; Furutaka, Kazuyoshi; Goko, Shinji*; Harada, Hideo; Hiraga, Fujio*; Igashira, Masayuki*; Kamiyama, Takashi*; et al.

JAEA-Conf 2011-002, p.29 - 34, 2011/09

The neutron capture cross sections of $$^{93}$$Zr, $$^{99}$$Tc and $$^{107}$$Pd have been measured relative to the $$^{10}$$B(n,$$alphagamma$$) standard cross section by the neutron time-of-flight (TOF) method. Neutron capture $$gamma$$ rays were measured with a 4$$pi$$ Ge spectrometer as a part of the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) installed at the neutron Beam Line No.4 (BL04) of the Material and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). This paper presents the preliminary results.

Journal Articles

Measurement of neutron-capture cross sections of palladium isotopes at the J-PARC/MLF/ANNRI

Nakamura, Shoji; Furutaka, Kazuyoshi; Goko, Shinji; Harada, Hideo; Kimura, Atsushi; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Ota, Masayuki; Oshima, Masumi; et al.

Journal of the Korean Physical Society, 59(2), p.1773 - 1776, 2011/08

 Times Cited Count:5 Percentile:41.54(Physics, Multidisciplinary)

A series of neutron-capture cross-section measurements using the time-of flight method has been started at the J-PARC/MLF/ANNRI. As a part of the measurements, we have measured the neutron-capture cross-sections of Pd isotopes such as $$^{105,106,108}$$Pd.

Journal Articles

Study of neutron capture reactions using the 4$$pi$$ Ge spectrometer

Harada, Hideo; Goko, Shinji*; Kimura, Atsushi; Ota, Masayuki*; Oshima, Masumi; Kitatani, Fumito; Toh, Yosuke; Furutaka, Kazuyoshi; Kin, Tadahiro; Koizumi, Mitsuo; et al.

Journal of the Korean Physical Society, 59(2), p.1547 - 1552, 2011/08

 Times Cited Count:8 Percentile:53.36(Physics, Multidisciplinary)

For the improvement of the accuracy on the neutron capture cross sections, a 4$$pi$$ Ge spectrometer was developed. The 4$$pi$$ Ge spectrometer is a unique tool due to its superior energy resolution for studying properties on neutron capture reactions, not only capture cross sections but also resonance identification, $$gamma$$-ray intensity distribution, and spin-parity assignment. For example, its performance on the resonance identification was demonstrated using a $$^{rm nat}$$Ag sample. On the measurement of a $$gamma$$-ray intensity distribution for each resonance, the results of $$^{238}$$U will be shown. Using the 4$$pi$$ Ge spectrometer, the measurements of neutron capture cross sections were started at the J-PARC/MLF/ANNRI. The preliminary results on the measurements of neutron capture cross sections will be discussed mainly based on measurements of neutron capture cross sections for $$^{241}$$Am, together with related techniques.

Journal Articles

Measurements of neutron-capture cross sections of $$^{244}$$Cm and $$^{246}$$Cm at J-PARC/MLF/ANNRI

Kimura, Atsushi; Furutaka, Kazuyoshi; Goko, Shinji*; Harada, Hideo; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Nakamura, Shoji; Ota, Masayuki*; Oshima, Masumi; et al.

Journal of the Korean Physical Society, 59(2), p.1828 - 1831, 2011/08

 Times Cited Count:2 Percentile:21.57(Physics, Multidisciplinary)

Journal Articles

The "Study on nuclear data by using a high intensity pulsed neutron source for advanced nuclear system" nuclear data project and the characteristics of the neutron beam line for the capture cross section experiments at J-PARC

Kiyanagi, Yoshiaki*; Kino, Koichi*; Furusaka, Michihiro*; Hiraga, Fujio*; Kamiyama, Takashi*; Kato, Kiyoshi*; Igashira, Masayuki*; Katabuchi, Tatsuya*; Mizumoto, Motoharu*; Oshima, Masumi; et al.

Journal of the Korean Physical Society, 59(2), p.1781 - 1784, 2011/08

 Times Cited Count:13 Percentile:64.75(Physics, Multidisciplinary)

The project of the comprehensive nuclear data research for the development of the advanced reactor systems had been executed successfully by eight organizations from 2005 to 2009. In this project, we constructed the pulsed neutron beamline that was aimed to obtain neutron capture cross-sections of long-lived fission products and minor actinides accurately. The energy spectra, spatial distributions, and pulses of the beam were studied by measurements and simulation calculations, and they were found to be consistent with those of the beamline design. In this paper, we present the overview of the project and the properties of the neutron beam provided by this beam line.

Journal Articles

Status and future perspectives of nuclear data measurements at J-PARC MLF BL04

Harada, Hideo; Oshima, Masumi; Kimura, Atsushi; Goko, Shinji*; Ota, Masayuki*; Furutaka, Kazuyoshi; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Nakamura, Shoji; et al.

JAEA-Conf 2010-005, p.9 - 14, 2010/12

The neutron-nucleus reaction instrument (NNRI) was installed at the J-PARC MLF BL04, which was designed for measuring neutron cross sections with a neutron time-of-flight technique. This includes two kinds of capture $$gamma$$-ray spectrometers: the 4$$pi$$ Ge spectrometer and the NaI spectrometers. The measurements of neutron capture cross sections for minor actinides and fission products have been started at the NNRI using these spectrometers since 2009. In this paper, the preliminary results and future perspectives are discussed.

Journal Articles

Measurement of neutron capture cross section ratios of $$^{244}$$Cm resonances using NNRI

Goko, Shinji*; Kimura, Atsushi; Harada, Hideo; Oshima, Masumi; Ota, Masayuki*; Furutaka, Kazuyoshi; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Nakamura, Shoji; et al.

Journal of Nuclear Science and Technology, 47(12), p.1097 - 1100, 2010/12

 Times Cited Count:5 Percentile:38.65(Nuclear Science & Technology)

To obtain the accurate nuclear data of minor actinides required for a nuclear transmutation system or an innovative nuclear fuel cycle system, measurement of neutron-capture cross section of $$^{244}$$Cm was performed using NNRI installed at beam line No.4 (BL04) of MLF in J-PARC. Using "4$$pi$$ Ge spectrometer" that is a component of NNRI, neutron time of flight spectra and prompt $$gamma$$ ray spectra were measured. Then neutron-capture cross section ratios of $$^{244}$$Cm resonances were derived and compared with the evaluated values of JENDL-3.3. The previous experimental data was measured using a nuclear explosion as a pulsed neutron source, and the present result is the first time in the world that such measurements have been carried out at an accelerator facility. By developing techniques for more detailed analysis and improvement of the experimental conditions, the absolute values of capture cross section are expected to be obtained.

Journal Articles

Percolation simulation of laser-guided electrical discharges

Sasaki, Akira; Kishimoto, Yasuaki*; Takahashi, Eiichi*; Kato, Susumu*; Fujii, Takashi*; Kanazawa, Seiji*

Physical Review Letters, 105(7), p.075004_1 - 075004_4, 2010/08

 Times Cited Count:10 Percentile:57.71(Physics, Multidisciplinary)

A three-dimensional simulation of laser guided-discharges based on the percolation is presented. The model includes both local growth of a streamer due to the enhanced electric field at the tip and propagation of a leader by remote ionization such that caused by runaway electrons. The stochastic behavior of the discharge through preformed plasma channel is reproduced by the calculation, which shows complex path with detouring and bifurcation. The probability of guiding is investigated with respect to the ionized, conductive fraction along the channel.

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