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Journal Articles

Direct energy conversion using Ni/SiC Schottky junction in $$^{237}$$Np and $$^{241}$$Am gamma ray regions

Fukuda, Tatsuo; Kobata, Masaaki; Shobu, Takahisa; Yoshii, Kenji; Kamiya, Junichiro; Iwamoto, Yosuke; Makino, Takahiro*; Yamazaki, Yuichi*; Oshima, Takeshi*; Shirai, Yasuhiro*; et al.

Journal of Applied Physics, 132(24), p.245102_1 - 245102_8, 2022/12

 Times Cited Count:1 Percentile:14.73(Physics, Applied)

Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron X-rays simulating the gamma rays of $$^{237}$$Np (30 keV) and $$^{241}$$Am (60 keV). From current-voltage measurements, electrical energies were obtained for both kinds of gamma rays. The energy conversion efficiencies were found to reach up to $$sim$$1.6%, which is comparable to those of a few other semiconducting systems reported thus far. This result shows a possibility of energy recovery from nuclear wastes using the present system, judging from the radiation tolerant nature of SiC. Also, we found different conversion efficiencies between the two samples. This could be understandable from hard X-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the formation of Ni-Si compounds at the interface in the sample with a poor performance. Hence, such combined measurements are useful to provide information that cannot be obtained by electrical measurements alone.

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:44 Percentile:96.99(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.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:262 Percentile:99.73(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Analytic cross sections for electron impact collisions with nitrogen molecules

Tabata, Tatsuo*; Shirai, Toshizo*; Sataka, Masao; Kubo, Hirotaka

Atomic Data and Nuclear Data Tables, 92(3), p.375 - 406, 2006/05

 Times Cited Count:73 Percentile:95.09(Physics, Atomic, Molecular & Chemical)

no abstracts in English

Journal Articles

Phonon anomaly on Na$$_x$$HfNCl superconductors with ${it T}$$$_c$$=22 K

Shamoto, Shinichi; Hirai, Atsuo*; Yamanaka, Shoji*; Aso, Naofumi*; Kajitani, Tsuyoshi*

Journal of Neutron Research, 12(4), p.295 - 300, 2004/12

Inelastic neutron scattering measurements have been performed on superconducting Na$$_x$$HfNCl powder samples with x=0.27 and 0.38 (T$$_c$$ =22 K). We have observed several temperature dependent phonon anomalies, e.g., at E=15, 29, 76, and 81 meV for the former sample. A phonon peak with E=14.5 meV at Q=6 $AA $^{-1}$$ increases for both samples with decreasing temperature below T=40 K, which is much higher than T$$_c$$. The phonon peak is assigned to an ab-plane vibrational mode, E$$_u$$, of chlorine and hafnium atoms, which strongly modifies the electronic band structure. The phonon anomaly is discussed in terms of carrier inhomogeneity.

Journal Articles

Fusion plasma performance and confinement studies on JT-60 and JT-60U

Kamada, Yutaka; Fujita, Takaaki; Ishida, Shinichi; Kikuchi, Mitsuru; Ide, Shunsuke; Takizuka, Tomonori; Shirai, Hiroshi; Koide, Yoshihiko; Fukuda, Takeshi; Hosogane, Nobuyuki; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.185 - 254, 2002/09

 Times Cited Count:34 Percentile:48.48(Nuclear Science & Technology)

With the main aim of providing physics basis for ITER and the steady-state tokamak reactors, JT-60/JT-60U has been developing and optimizing the operational concepts, and extending the discharge regimes toward sustainment of high integrated performance in the reactor relevant parameter regime. In addition to achievement of the equivalent break-even condition (QDTeq up to 1.25) and a high fusion triple product = 1.5E21 m-3skeV, JT-60U has demonstrated the integrated performance of high confinement, high beta-N, full non-inductive current drive with a large fraction of bootstrap current in the reversed magnetic shear and in the high-beta-p ELMy H mode plasmas characterized by both internal and edge transport barriers. The key factors in optimizing these plasmas are profile and shape controls. As represented by discovery of various Internal Transport Barriers, JT-60/JT-60U has been emphasizing freedom and restriction of profiles in various confinement modes. JT-60U has demonstrated applicability of these high confinement modes to ITER and also clarified remaining issues.

Journal Articles

Analytic cross sections for electron collisions with hydrocarbons; CH$$_4$$, C$$_2$$H$$_6$$, C$$_2$$H$$_4$$, C$$_2$$H$$_2$$, C$$_3$$H$$_8$$, and C$$_3$$H$$_6$$

Shirai, Toshizo; Tabata, Tatsuo*; Tawara, Hiroyuki*; Ichikawa, Yukikazu*

Atomic Data and Nuclear Data Tables, 80(2), p.147 - 204, 2002/03

 Times Cited Count:74 Percentile:93.79(Physics, Atomic, Molecular & Chemical)

Cross sections for 138 processes of hydrocarbons in collisions with electrons, based on available literature sources, are critically compiled. The leterature has been surveyed to September 2000. A short comment is given for each measurement. The recommended data sets are presented in separate graphs for each process. Analytic fits to the recommended cross sections are also presented.

Journal Articles

Analytic cross sections for electron collisions with CO, CO$$_{2}$$, and H$$_{2}$$O relevant to edge plasma impurities

Shirai, Toshizo; Tabata, Tatsuo*; Tawara, Hiroyuki*

Atomic Data and Nuclear Data Tables, 79(1), p.143 - 184, 2001/09

 Times Cited Count:56 Percentile:91.40(Physics, Atomic, Molecular & Chemical)

no abstracts in English

Journal Articles

High radiation and high density experiments in JT-60U

Kubo, Hirotaka; Sakurai, Shinji; Asakura, Nobuyuki; Konoshima, Shigeru; Tamai, Hiroshi; Higashijima, Satoru; Sakasai, Akira; Takenaga, Hidenobu; Itami, Kiyoshi; Shimizu, Katsuhiro; et al.

Nuclear Fusion, 41(2), p.227 - 233, 2001/02

 Times Cited Count:53 Percentile:81.48(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Analytic cross sections for collisions of H$$^{+}$$, H$$_{2}^{+}$$, H$$_{3}^{+}$$, H, H$$_{2}$$ and H$$^{-}$$ with hydrogen molecules

Tabata, Tatsuo*; Shirai, Toshizo

Atomic Data and Nuclear Data Tables, 76(1), p.1 - 25, 2000/09

 Times Cited Count:79 Percentile:94.45(Physics, Atomic, Molecular & Chemical)

no abstracts in English

Journal Articles

Monte Carlo simulation of hellium atoms and ions in JT-60U W-shaped divertor

Suzuki, Shingo*; Shimizu, Katsuhiro; Kubo, Hirotaka; Shirai, Toshizo; Sakasai, Akira; Sugie, Tatsuo; Asakura, Nobuyuki

Europhysics Conference Abstracts, 23J, p.477 - 480, 1999/00

no abstracts in English

Journal Articles

Role of divertor geometry on detachment and core plasma performance on JT60U

Asakura, Nobuyuki; Hosogane, Nobuyuki; Itami, Kiyoshi; Sakasai, Akira; Sakurai, Shinji; Shimada, Michiya; Kubo, Hirotaka; Higashijima, Satoru; Shimizu, Katsuhiro; Takenaga, Hidenobu; et al.

Journal of Nuclear Materials, 266-269, p.182 - 188, 1999/00

 Times Cited Count:66 Percentile:96.64(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Attenuation of high-energy neutral hydrogen beams in high-density plasmas

Suzuki, Shingo*; Shirai, Toshizo; Nemoto, Masahiro; Tobita, Kenji; Kubo, Hirotaka; Sugie, Tatsuo; Sakasai, Akira; Kusama, Yoshinori

Plasma Physics and Controlled Fusion, 40(12), p.2097 - 2111, 1998/00

 Times Cited Count:61 Percentile:85.55(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Analytic cross sections for collisions of H, H$$_{2}$$, He and Li atoms and ions with atoms and molecules,IV

Ito, Rinsuke*; Tabata, Tatsuo*; Shirai, Toshizo; R.A.Phaneuf*

JAERI-Data/Code 96-024, 62 Pages, 1996/07

JAERI-Data-Code-96-024.pdf:1.32MB

no abstracts in English

JAEA Reports

Analytic cross sections for collisions of H, H$$_{2}$$, He and Li atoms and ions with atoms and molecules, III

Ito, Rinsuke*; Tabata, Tatsuo*; Shirai, Toshizo; R.A.Phaneuf*

JAERI-Data/Code 95-008, 71 Pages, 1995/07

JAERI-Data-Code-95-008.pdf:1.54MB

no abstracts in English

Journal Articles

Non-dimensional transport scaling and its correlation with local transport properties in JT-60U plasmas

Shirai, Hiroshi; Takizuka, Tomonori; Kikuchi, Mitsuru; Mori, Masahiro; Nishitani, Takeo; Ishida, Shinichi; Kamada, Yutaka; Sato, Masayasu; Isei, Nobuaki; Koide, Yoshihiko; et al.

IAEA-CN-60/A2-17, 0, p.355 - 364, 1995/00

no abstracts in English

JAEA Reports

Analytic cross sections for collisions of H, H$$_{2}$$, He and Li atoms and ions with atoms and molecules, II

Ito, Rinsuke*; Tabata, Tatsuo*; Shirai, Toshizo; R.A.Phaneuf*

JAERI-Data/Code 94-005, 94 Pages, 1994/07

JAERI-Data-Code-94-005.pdf:2.0MB

no abstracts in English

Journal Articles

Evaluation of aseismic integrity in HTTR core-bottom structure, II; Vibrational characteristics of keyed graphite components

Futakawa, Masatoshi; Iyoku, Tatsuo; Shirai, Hiroshi*; Takada, Shoji; Ishihara, Masahiro

Nucl. Eng. Des., 148, p.83 - 90, 1994/00

 Times Cited Count:4 Percentile:42.28(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Ion temperature profile simulation of JT-60 and TFTR plasmas with ion temperature gradient mode transport models

Shirai, Hiroshi; Hirayama, Toshio; Koide, Yoshihiko; Yoshida, Hidetoshi; Naito, Osamu; Sato, Masayasu; Fukuda, Takeshi; Sugie, Tatsuo; Azumi, Masafumi; D.R.Mikkelsen*; et al.

Nuclear Fusion, 34(5), p.703 - 727, 1994/00

 Times Cited Count:7 Percentile:31.14(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Analytic cross sections for collisions of H, H$$_{2}$$, He and Li atoms and ions with atoms and molecules, I

Ito, Rinsuke*; Tabata, Tatsuo*; Shirai, Toshizo; R.A.Phaneuf*

JAERI-M 93-117, 91 Pages, 1993/06

JAERI-M-93-117.pdf:1.88MB

no abstracts in English

30 (Records 1-20 displayed on this page)