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Journal Articles

Oxidation of anatase TiO$$_{2}$$(001) surface using supersonic seeded oxygen molecular beam

Katsube, Daiki*; Ono, Shinya*; Takayanagi, Shuhei*; Ojima, Shoki*; Maeda, Motoyasu*; Origuchi, Naoki*; Ogawa, Arata*; Ikeda, Natsuki*; Aoyagi, Yoshihide*; Kabutoya, Yuito*; et al.

Langmuir, 37(42), p.12313 - 12317, 2021/10

 Times Cited Count:1 Percentile:7.13(Chemistry, Multidisciplinary)

We investigated the oxidation of oxygen vacancies at the surface of anatase TiO$$_{2}$$(001) using supersonic seeded molecular beam (SSMB) of oxygen. The oxygen vacancies at the top-surface and sub-surface could be eliminated by the supply of oxygen using an SSMB. These results indicate that the interstitial vacancies can be mostly assigned to oxygen vacancies, which can be effectively eliminated by using an oxygen SSMB. Oxygen vacancies are present on the surface of anatase TiO$$_{2}$$(001) when it is untreated before transfer to a vacuum chamber. These vacancies, which are stable in the as-grown condition, could also be effectively eliminated using the oxygen SSMB.

Journal Articles

Optimization of a 9 MeV electron accelerator bremsstrahlung flux for photofission-based assay techniques using PHITS and MCNP6 Monte Carlo codes

Meleshenkovskii, I.*; Ogawa, Tatsuhiko; Sari, A.*; Carrel, F.*; Boudergui, K.*

Nuclear Instruments and Methods in Physics Research B, 483, p.5 - 14, 2020/11

 Times Cited Count:2 Percentile:36.99(Instruments & Instrumentation)

For the purpose of fissile material detection, the technique to observe neutrons ejected from photo-fission induced by bremsstrahlung X-rays is being developed. This technique is advantageous in the sense that the machine can be compact compared to conventional neutron generators. However, photo-fission reaction cross sections are generally smaller than those of neutron-induced fission cross sections therefore optimization of the beam line is of high importance. In this study, we investigated the factors necessary to be optimized by using Monte-Carlo transport codes MCNP and PHITS. It was found that high-Z materials are advantageous to effectively produce bremsstrahlung X-rays but photons produce neutrons by secondary ($$gamma$$,n) reactions resulting in mixing of prompt and delayed fission reactions. Moreover, secondary neutrons are produced not only inside the target but also in the materials surrounding the target. Therefore it is necessary to select elements whose neutron separation energy is high to suppress parasitic secondary neutrons.

Journal Articles

Valence-band electronic structure evolution of graphene oxide upon thermal annealing for optoelectronics

Yamaguchi, Hisato*; Ogawa, Shuichi*; Watanabe, Daiki*; Hozumi, Hideaki*; Gao, Y.*; Eda, Goki*; Mattevi, C.*; Fujita, Takeshi*; Yoshigoe, Akitaka; Ishizuka, Shinji*; et al.

Physica Status Solidi (A), 213(9), p.2380 - 2386, 2016/09

 Times Cited Count:13 Percentile:52.76(Materials Science, Multidisciplinary)

We report valence-band electronic structure evolution of graphene oxide (GO) upon its thermal reduction. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored using real-time ultraviolet photoelectron spectroscopy. We observed a drastic increase in the density of states around the Fermi level upon thermal annealing at $$sim$$ 600$$^{circ}$$C. The result indicates that while there is an apparent bandgap for GO prior to a thermal reduction, the gap closes after an annealing around that temperature. This trend of bandgap closure was correlated with the electrical, chemical, and structural properties to determine a set of GO material properties that is optimal for optoelectronics. The results revealed that annealing at a temperature of 500$$^{circ}$$C leads to the desired properties, demonstrated by a uniform and an order of magnitude enhanced photocurrent map of an individual GO sheet compared to an as-synthesized counterpart.

Journal Articles

Small gas bubble experiment for mitigation of cavitation damage and pressure waves in short-pulse mercury spallation targets

Riemer, B. W.*; Wendel, M. W.*; Felde, D. K.*; Sangrey, R. L.*; Abdou, A.*; West, D. L.*; Shea, T. J.*; Hasegawa, Shoichi; Kogawa, Hiroyuki; Naoe, Takashi; et al.

Journal of Nuclear Materials, 450(1-3), p.192 - 203, 2014/07

 Times Cited Count:14 Percentile:72.72(Materials Science, Multidisciplinary)

Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 $$mu$$m in radius with achieved gas void fractions in the 10$$^{-5}$$ to 10$$^{-4}$$ range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.

Journal Articles

Monopole-driven shell evolution below the doubly magic nucleus $$^{132}$$Sn explored with the long-lived isomer in $$^{126}$$Pd

Watanabe, H.*; Lorusso, G.*; Nishimura, Shunji*; Otsuka, T.*; Ogawa, K.*; Xu, Z. Y.*; Sumikama, Toshiyuki*; S$"o$derstr$"o$m, P.-A.*; Doornenbal, P.*; Li, Z.*; et al.

Physical Review Letters, 113(4), p.042502_1 - 042502_6, 2014/07

 Times Cited Count:24 Percentile:77.04(Physics, Multidisciplinary)

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:28 Percentile:72.42(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:176 Percentile:99.41(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:7 Percentile:49.81(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

 Times Cited Count:169 Percentile:98.47(Astronomy & Astrophysics)

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of $$K^0_s$$, $$omega$$, $$eta'$$ and $$phi$$ mesons in $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, $$n$$ and $$T$$, determining the high $$p_T$$ and characterizing the low $$p_T$$ regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

Journal Articles

Precision hfs of $$^{126}$$Cs($$T$$$$_{1/2}$$ = 1.63 m) by ABMR

Pinard, J.*; Duong, H. T.*; Marescaux, D.*; Stroke, H. H.*; Redi, O.*; Gustafsson, M.*; Nilsson, T.*; Matsuki, S.*; Kishimoto, Yasuaki*; Kominato, K.*; et al.

Nuclear Physics A, 753(1-2), p.3 - 12, 2005/05

 Times Cited Count:4 Percentile:36.01(Physics, Nuclear)

The hfs separation $$Deltanu$$ of $$^{126}$$Cs($$T$$$$_{1/2} = 1.63$$ m) in the 6s $$^2$$S$$_{1/2}$$ ground state was obtained in a precision measurement near zero magnetic field by means of atomic beam magnetic resonance with laser optical pumping on-line with the CERN-PSB-ISOLDE mass separator. The result, $$Deltanu = 3629.514(0.001)$$ MHz, corrects significantly a previous published value from a high-field experiment. With our result, the precision of the nuclear magnetic moment, $$mu(^{126}$$Cs)$$sim 0.776 mu_N$$, is now limited by the influence of extended nuclear structure on the hfs (the Bohr-Weisskopf effect).

Journal Articles

Thermochemical properties of advanced fission fuel materials

Ogawa, Toru; Okamoto, Yoshihiro; R.J.K.Konings*

Advances in Science and Technology, 24, p.381 - 392, 1999/00

no abstracts in English

Journal Articles

Crystal chemistry of NpNi$$_{5}$$ compound

Akabori, Mitsuo; R.G.Haire*; J.K.Gibson*; Okamoto, Yoshihiro; Ogawa, Toru

Journal of Alloys and Compounds, 257, p.268 - 272, 1997/00

 Times Cited Count:2 Percentile:29.46(Chemistry, Physical)

no abstracts in English

Journal Articles

An X-ray diffraction study of the Np-Ni system

Akabori, Mitsuo; R.G.Haire*; J.K.Gibson*; Okamoto, Yoshihiro; Ogawa, Toru

Journal of Nuclear Materials, 247, p.240 - 243, 1997/00

 Times Cited Count:2 Percentile:23.05(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Design study of feasible water detritiation systems for fusion reactor of ITER scale

Iwai, Yasunori; Yamanishi, Toshihiko; Okuno, Kenji; Yokogawa, Nobuhisa*; *; Yoshida, Hiroshi; O.K.Kveton*

Journal of Nuclear Science and Technology, 33(12), p.981 - 992, 1996/12

 Times Cited Count:27 Percentile:89.28(Nuclear Science & Technology)

no abstracts in English

Journal Articles

The Investigation of selected Np-Zr alloys by X-ray diffraction up to 700$$^{circ}$$C

Okamoto, Yoshihiro; R.G.Haire*; J.K.Gibson*; Ogawa, Toru

Journal of Alloys and Compounds, 232, p.302 - 306, 1996/00

 Times Cited Count:8 Percentile:56.59(Chemistry, Physical)

no abstracts in English

Journal Articles

Thermodynamic analysis of Zr-U and Zr-Np alloys in view of f-d interaction

Ogawa, Toru; J.K.Gibson*; R.G.Haire*; M.M.Gensini*; Akabori, Mitsuo

Journal of Nuclear Materials, 223, p.67 - 71, 1995/00

 Times Cited Count:15 Percentile:79.41(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Proceeding of the Second Steering Conference relating to the Agreement on the Implementation of Research at the Chernobyl Center for International Research between CHECIR and JAERI

Nagaoka, Toshi; Togawa, Orihiko; Moriuchi, Shigeru; S.I.Rybalko*; Sukhoruchkin, A. K.*; S.V.Kazakov*

JAERI-Conf 94-005, 99 Pages, 1994/11

JAERI-Conf-94-005.pdf:3.18MB

no abstracts in English

Journal Articles

Alloying behavior in selected neptunium binary systems; The Role of 5f-bonding

J.K.Gibson*; R.G.Haire*; M.M.Gensini*; Ogawa, Toru

Journal of Alloys and Compounds, 213-214, p.106 - 110, 1994/00

 Times Cited Count:12 Percentile:66.85(Chemistry, Physical)

no abstracts in English

Journal Articles

Neptunium-iron phase diagram

J.K.Gibson*; R.G.Haire*; E.C.Beahm*; M.M.Gensini*; Maeda, Atsushi; Ogawa, Toru

Journal of Nuclear Materials, 211, p.215 - 222, 1994/00

 Times Cited Count:9 Percentile:63.38(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Development of a diagnostic system for high power microwave(FEL) electric fields in the microwave tokamak experiment

*; Odajima, Kazuo; Takiyama, Ken*; J.H.Foote*; K.Mizuno*; Ogawa, Toshihide; *; ; Hoshino, Katsumichi; Maeda, Hikosuke; et al.

Proc. of the 1992 Int. Conf. on Plasma Physics, Vol. 16C, Part II, p.II1191 - II1194, 1992/00

no abstracts in English

Oral presentation

Time-scale of POC cycle in the Japan Sea

Otosaka, Shigeyoshi; Tanaka, Takayuki; Togawa, Orihiko; Amano, Hikaru; Minakawa, Masayuki*; Khim, B.-K.*; Noriki, Shinichiro*

no journal, , 

A time-scale of particulate organic carbon (POC) in the Japan Sea, a marginal sea of the North Pacific, was quantified from radiocarbon (C-14) and stable carbon (C-13) measurements. Delta C-14 in POC decreased with depth, and the value was higher in the order of sinking POC, suspended POC and seabed sediment. delta C-13 values in suspended POC were higher than those in sinking POC obtained from the similar depth. From the radiocarbon signatures and elemental compositions of sinking POC, it was considered that Delta C-14 in sinking POC was determined by a mixing ratio of terrestrial and surface-produced POC. In addition, the difference of Delta C-14 and delta C-13 between the terrestrial and suspended POC was considered to indicate migration process of POC in the water column. From the difference of the C-14 age between terrestrial and suspended POC, it was estimated that an actual age of suspended POC at 3 km depth in the Japan Sea was about 300 years.

21 (Records 1-20 displayed on this page)