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Journal Articles

Magnetic properties and electronic configurations of Mn ions in the diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ studied by X-ray magnetic circular dichroism and resonant inelastic X-ray scattering

Suzuki, Hakuto*; Zhao, G.*; Okamoto, Jun*; Sakamoto, Shoya*; Chen, Z.-Y.*; Nonaka, Yosuke*; Shibata, Goro; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.

Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.52(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

JAEA Reports

XAFS measurement of simulated waste glass samples (Borosilicate glass including vanadium)

Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Ayame, Yasuo; Okamoto, Yoshihiro; Shiwaku, Hideaki; Matsuura, Haruaki*; Uchiyama, Takafumi*; Okada, Yukiko*; Nezu, Atsushi*; et al.

JAEA-Research 2016-015, 52 Pages, 2016/11


The local structure of waste elements in simulated waste glasses including V was estimated by using synchrotron XAFS measurement in this study. The results are as follows. (1) V has a high possibility which exists in the glass phase in the case of frit, and V can regard both samples as stable 4 coordination structure. (2) Zn, Ce, Nd, Zr, and Mo exist in the glass phase, and the difference is admitted by the percentage of Ce(III) and Ce(IV) by the composition. (3) Ru is separated from the glass phase as RuO$$_{2}$$ crystalline, both of metal and oxide exist in Rh, and Pd is separated out as metal. (4) It was confirmed that the regularity of the local structure of Zr and Mo in the molten glasses retreats as a result of the XAFS measurement at high temperature. (5) The XAFS measurement of molten glasses were performed at 1200$$^{circ}$$C, so it would be possible to acquire excellent data by improving the shapes of the sample cell.

Journal Articles

Determination of the number of pulsed laser-Compton scattering photons

Kondo, Takeo*; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Yamagata, Tamio*; Okamoto, Akiyuki*; Harada, Hideo; Kitatani, Fumito; Shima, Tatsushi*; Horikawa, Ken*; Miyamoto, Shuji*

Nuclear Instruments and Methods in Physics Research A, 659(1), p.462 - 466, 2011/12

 Times Cited Count:27 Percentile:88.52(Instruments & Instrumentation)

We measured pulse-height spectra of 16.7 MeV laser-Compton scattering photons with a 6"$$times$$5" NaI(Tl) detector for blank and three lead materials of 75.8, 50.9, and 25.9% transmissions at the NewSUBARU facility to investigate how the original Poisson distribution of the pulsed photons is modified after passing through thick-target materials. We present a well-prescribed method of determining the number of incident photons within 3.5% accuracy based on the response of the NaI(Tl) detector to the pulsed photon beams.

Journal Articles

Structural investigation of thorium in molten lithium-calcium fluoride mixtures for salt treatment process in molten salt reactor

Numakura, Masahiko*; Sato, Nobuaki*; Bessada, C.*; Okamoto, Yoshihiro; Akatsuka, Hiroshi*; Nezu, Atsushi*; Shimohara, Yasuaki*; Tajima, Keisuke*; Kawano, Hirokazu*; Nakahagi, Takeshi*; et al.

Progress in Nuclear Energy, 53(7), p.994 - 998, 2011/11

 Times Cited Count:13 Percentile:70.68(Nuclear Science & Technology)

X-ray absorption fine structure (XAFS) measurements on thorium fluoride in molten lithium-calcium fluoride mixtures and molecular dynamics (MD) simulation of zirconium and yttrium fluoride in molten lithium-calcium fluoride mixtures have been carried out. In the molten state, coordination number of thorium and inter ionic distances between thorium and fluorine in the first neighbor are nearly constant in all mixtures. However the fluctuation factors (Debye-Waller factor and C$$_3$$ cumulant) increase until $$x$$CaF$$_2$$ = 0.17 and decrease by addition of excess CaF$$_2$$. It means that the local structure around Th$$^{4+}$$ is disordered until $$x$$CaF$$_2$$=0.17 and stabilized over $$x$$CaF$$_2$$ = 0.17. The variation of fluctuation factors is related to the number density of F$$^-$$ in ThF$$_4$$ mixtures and the stability of local structure around Th$$^{4+}$$ increases with decreasing the number density of F$$^-$$ in ThF$$_4$$ mixtures. This tendency is common to those in the ZrF$$_4$$ and YF$$_3$$ mixtures.

Journal Articles

Removal of fission products in the spent electrolyte using iron phosphate glass as a sorbent

Amamoto, Ippei; Mitamura, Naoki*; Tsuzuki, Tatsuya*; Takasaki, Yasushi*; Shibayama, Atsushi*; Yano, Tetsuji*; Nakada, Masami; Okamoto, Yoshihiro

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.503 - 508, 2010/10

The main objective of this development is to recycle the purified eutectic medium of the pyroreprocessing, delaying its disposal for as long as possible. We have introduced the simple filtration method to remove the rare earth element (REE) particles which were formed due to the conversion of REE chlorides to phosphates. Here, the iron phosphate glass is used as a filtration medium for the removal of FP particles. However, some soluble FP such as compounds of alkali-metals, alkaline-earth metals, etc. still remain in the eutectic medium. This time around, on an experimental basis, the iron phosphate glass has been used as a sorbent instead, to remove the soluble FP. We have obtained some positive results and have intention to incorporate it into the spent electrolyte recycle process as a part of the FP separation and immobilization system.

Journal Articles

Fast neutron-$$gamma$$ discrimination on neutron emission profile measurement on JT-60U

Ishii, Keiichi*; Shinohara, Koji; Ishikawa, Masao; Baba, Mamoru*; Isobe, Mitsutaka*; Okamoto, Atsushi*; Kitajima, Sumio*; Sasao, Mamiko*

Review of Scientific Instruments, 81(10), p.10D334_1 - 10D334_3, 2010/10

 Times Cited Count:6 Percentile:31.42(Instruments & Instrumentation)

Journal Articles

In-situ analyses of chemical state and ionic distribution in the extraction chromatography column

Watanabe, So; Sano, Yuichi; Myochin, Munetaka; Okamoto, Yoshihiro; Shiwaku, Hideaki; Ikeda, Atsushi; Suzuki, Shinichi; Yaita, Tsuyoshi

Nihon Ion Kokan Gakkai-Shi, 21(3), p.189 - 194, 2010/07

Journal Articles

Local coordination about La$$^{3+}$$ in molten LaCl$$_3$$ and its mixtures with alkali chlorides

Okamoto, Yoshihiro; Suzuki, Shinichi; Shiwaku, Hideaki; Ikeda, Atsushi; Yaita, Tsuyoshi; Madden, P. A.*

Journal of Physical Chemistry A, 114(13), p.4664 - 4671, 2010/03

 Times Cited Count:51 Percentile:85.94(Chemistry, Physical)

The local structure around the La$$^{3+}$$ ions in molten LaCl$$_{3}$$ and its mixtures with alkali and alkaline earth chlorides has been investigated by using extended X-ray absorption fine structure (XAFS) and molecular dynamics (MD) techniques. New experimental methods allow observations at the La K-absorption edge at the high temperatures of interest and the ability of the technique to obtain reliable information even at very low La$$^{3+}$$ concentrations in multi-component mixtures is demonstrated. Both the mean La-Cl interionic separation and the mean La$$^{3+}$$ coordination number are found to decrease as the concentration of La$$^{3+}$$ in the mixture decreases. In dilute mixtures with such cations La$$^{3+}$$ is able to adopt a very stable octahedral coordination geometry but this is inhibited by the presence of more strongly coordinating cations like Li$$^{+}$$ and Mg$$^{2+}$$.

Journal Articles

Measurement of DT and DD neutrons with a TOF spectrometer for determination of fuel ion density ratio in ITER

Okada, Koichi*; Kondo, Keitaro; Ochiai, Kentaro; Sato, Satoshi; Konno, Chikara; Okamoto, Atsushi*; Kobuchi, Takashi*; Kitajima, Sumio*; Sasao, Mamiko*

Journal of Plasma and Fusion Research SERIES, Vol.8, p.666 - 669, 2009/09

Measurement of fuel ion density ratio, $$n$$$$_{rm D}$$/$$n$$$$_{rm T}$$, is required for burning control on ITER. The measured $$n$$$$_{rm D}$$/$$n$$$$_{rm T}$$ ratio must be fed back in real time. A neutron measurement system to measure $$n$$$$_{rm D}$$/$$n$$$$_{rm T}$$ should be operable at high counting rate. It is estimated that the number of emitted DT neutrons is 200 times higher than that of DD neutrons under the condition of ITER standard operation. A neutron measurement system was developed using a DT/DD generator, where DT neutrons are dominant and DD neutrons are contaminated slightly in the neutron beam. The measurement instrument was a TOF spectrometer. Signals originating from each neutron must be distinguished in order to measure the fuel ratio. We developed a circuit system with discrimination windows to distinguish each signal pulse, and DT and DD neutrons were measured separately and simultaneously with this system. The experimental result indicates a possibility that this system is suitable for measurement of fuel ion density ratio on ITER.

Journal Articles

Nature of magnetic coupling between Mn ions in as-grown Ga$$_{1-x}$$Mn$$_{x}$$As studied by X-ray magnetic circular dichroism

Takeda, Yukiharu; Kobayashi, Masaki*; Okane, Tetsuo; Okochi, Takuo*; Okamoto, Jun*; Saito, Yuji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Fujimori, Atsushi*; Tanaka, Arata*; et al.

Hoshako, 22(4), p.202 - 209, 2009/07

no abstracts in English

Journal Articles

Nature of magnetic coupling between Mn ions in as-grown Ga$$_{1-x}$$Mn$$_{x}$$As studied by X-ray magnetic circular dichroism

Takeda, Yukiharu; Kobayashi, Masaki*; Okane, Tetsuo; Okochi, Takuo; Okamoto, Jun*; Saito, Yuji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Fujimori, Atsushi; Tanaka, Arata*; et al.

Physical Review Letters, 100(24), p.247202_1 - 247202_4, 2008/06

 Times Cited Count:39 Percentile:82.47(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Soft X-ray magnetic circular dichroism study of uranium monochalcogenides at uranium $$N_{4,5}$$ absorption edges

Okane, Tetsuo; Takeda, Yukiharu; Okamoto, Jun*; Mamiya, Kazutoshi*; Okochi, Takuo; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Ochiai, Akira*; et al.

Journal of the Physical Society of Japan, 77(2), p.024706_1 - 024706_6, 2008/02

 Times Cited Count:15 Percentile:64.7(Physics, Multidisciplinary)

Journal Articles

Soft X-ray magnetic circular dichroism study of Ca$$_{1-x}$$Sr$$_x$$RuO$$_3$$ across the ferromagnetic quantum phase transition

Okamoto, Jun*; Okane, Tetsuo; Saito, Yuji; Terai, Kota*; Fujimori, Shinichi; Muramatsu, Yasuji*; Yoshii, Kenji; Mamiya, Kazutoshi*; Koide, Tsuneharu*; Fujimori, Atsushi; et al.

Physical Review B, 76(18), p.184441_1 - 184441_5, 2007/11

 Times Cited Count:34 Percentile:76.57(Materials Science, Multidisciplinary)

Ca$$_{1-x}$$Sr$$_x$$RuO$$_3$$, which is ferromagnetic for Sr concentration x $$>$$ 0.3, has been studied by X-ray magnetic circular dichroism (XMCD) in Ru 3$$p$$ and O 1$$s$$ core-level X-ray absorption. XMCD signals appear at x $$sim$$ 0.3 and monotonically increases with x in the ferromagnetic phase. While the monotonic increase of the XMCD signals with x is of a typical Stoner-type, the absence of appreciable change in the spectral line shapes of both the Ru 3$$p$$ and O 1$$s$$ XMCD spectra indicate that the itinerant-electron ferromagnetism in Ca$$_{1-x}$$Sr$$_x$$RuO$$_3$$ is influenced by strong electron correlation.

Journal Articles

${it Ex-situ}$ and ${it in-situ}$ X-ray diffractions of corrosion products freshly formed on the surface of an iron-silicon alloy

Suzuki, Shigeru*; Matsubara, Eiichiro*; Komatsu, Takuya*; Okamoto, Yoshinori*; Kanie, Kiyoshi*; Muramatsu, Atsushi*; Konishi, Hiroyuki; Mizuki, Junichiro; Waseda, Yoshio*

Corrosion Science, 49(3), p.1081 - 1096, 2007/03

 Times Cited Count:32 Percentile:81.09(Materials Science, Multidisciplinary)

${it Ex-situ}$ X-ray diffraction measurements of a small amount of samples extracted from wet corrosion products freshly formed on a pure iron and iron-2 mass% silicon surfaces have been conducted using synchrotron radiation. The results showed that $$gamma$$-FeOOH was formed on the outer side of wet corrosion products formed on the pure iron by sodium chloride solution, while $$gamma$$-FeOOH, $$alpha$$-FeOOH, Fe$$_{3}$$O$$_{4}$$, and green rusts were formed on the inner side. In comparison to the case of the pure iron, a significant formation of $$beta$$-FeOOH was observed in the iron-silicon alloy. Furthermore, in-situ diffraction measurements by a conventional X-ray source were conducted for analyzing corrosion products formed on the pure iron and iron-silicon alloy surfaces by cyclic exposure to wet and dry atmospheres. The results obtained by the ${it in-situ}$ diffraction and ${it ex-situ}$ diffraction measurements on the corrosion products were consistent.

Journal Articles

Soft X-ray magnetic circular dichroism study of weakly ferromagnetic Zn$$_{1-x}$$V$$_{x}$$O thin film

Ishida, Yukiaki*; Hwang, J. I.*; Kobayashi, Masaki*; Takeda, Yukiharu; Mamiya, Kazutoshi*; Okamoto, Jun*; Fujimori, Shinichi; Okane, Tetsuo; Terai, Kota*; Saito, Yuji; et al.

Applied Physics Letters, 90(2), p.022510_1 - 022510_3, 2007/01

 Times Cited Count:23 Percentile:64.7(Physics, Applied)

no abstracts in English

Journal Articles

Soft X-ray magnetic circular dichroism study of ferromagnetic uranium compounds

Okane, Tetsuo; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Okamoto, Jun*; Mamiya, Kazutoshi*; Muramatsu, Yasuji*; Fujimori, Atsushi; Ochiai, Akira*; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.105 - 106, 2006/08

no abstracts in English

Journal Articles

Soft X-ray absorption magnetic circular dichroism study of ferromagnetic superconductor UGe$$_2$$

Okane, Tetsuo; Okamoto, Jun*; Mamiya, Kazutoshi*; Fujimori, Shinichi; Takeda, Yukiharu; Saito, Yuji; Muramatsu, Yasuji*; Fujimori, Atsushi*; Haga, Yoshinori; Yamamoto, Etsuji; et al.

Journal of the Physical Society of Japan, 75(2), p.024704_1 - 024704_5, 2006/02

 Times Cited Count:12 Percentile:58.59(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Evolution of the electronic structure across the filling-control and bandwidth-control metal-insulator transitions in pyrochlore-type Ru oxides

Okamoto, Jun*; Fujimori, Shinichi; Okane, Tetsuo; Fujimori, Atsushi*; Abbate, M.*; Yoshii, Shunsuke*; Sato, Masatoshi*

Physical Review B, 73(3), p.035127_1 - 035127_6, 2006/01

 Times Cited Count:2 Percentile:12.72(Materials Science, Multidisciplinary)

We have performed photoemission and soft X-ray absorption studies of pyrochlore-type Ru oxides, namely, the filling-control system Sm$$_{2-x}$$Ca$$_x$$Ru$$_2$$O$$_7$$ and the bandwidth-control system Sm$$_{2-x}$$Bi$$_x$$Ru$$_2$$O$$_7$$, which show insulator-to-metal transition with increasing Ca and Bi concentration, respectively. Core levels and the O 2$$p$$ valence band in Sm$$_{2-x}$$Ca$$_x$$Ru$$_2$$O$$_7$$ show almost the same amount of monotonous upward energy shifts with Ca concentration, which indicates that the chemical potential is shifted downward due to hole doping. The Ru 4$$d$$ band in Sm$$_{2-x}$$Ca$$_x$$Ru$$_2$$O$$_7$$ is also shifted toward the Fermi level ($$E_F$$) with hole doping and the density of states (DOS) at $$E_F$$ increases. The core levels in Sm$$_{2-x}$$Bi$$_x$$Ru$$_2$$O$$_7$$, on the other hand, do not show clear energy shifts except for the Ru 3$$d$$ core level, whose line shape change also reflects the increase of metallic screening with Bi concentration. We observe pronounced spectral weight transfer from the incoherent to the coherent parts of the Ru $$4d$$ $$t_{2g}$$ band with Bi concentration, which is expected for a bandwidth-control Mott-Hubbard system. The increase of the DOS at $$E_F$$ is more abrupt in the bandwidth-control Sm$$_{2-x}$$Bi$$_x$$Ru$$_2$$O$$_7$$ than in the filling-control Sm$$_{2-x}$$Ca$$_x$$Ru$$_2$$O$$_7$$, in accordance with a recent theoretical prediction. Effects of charge transfer between the Bi 6$$sp$$ band and the Ru 4$$d$$ band are also discussed.

Journal Articles

Characterization of magnetic components in the diluted magnetic semiconductor Zn$$_{1-x}$$Co$$_x$$O by X-ray magnetic circular dichroism

Kobayashi, Masaki*; Ishida, Yukiaki*; Hwang, J. I.*; Mizokawa, Takashi*; Fujimori, Atsushi*; Mamiya, Kazutoshi*; Okamoto, Jun*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; et al.

Physical Review B, 72(20), p.201201_1 - 201201_4, 2005/11

 Times Cited Count:140 Percentile:96.14(Materials Science, Multidisciplinary)

no abstracts in English

56 (Records 1-20 displayed on this page)