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

https://doi.org/10.1038/s41550-020-01271-2

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 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 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.

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

https://doi.org/10.1126/science.aav7432

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.

Event structure and double helicity asymmetry in jet production from polarized collisions at = 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

https://doi.org/10.1103/PhysRevD.84.012006

We report on the event structure and double helicity asymmetry () of jet production in longitudinally polarized collisions at = 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 = -0.0014 0.0037 at the lowest bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various distributions.

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in and Au+Au collisions at = 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

https://doi.org/10.1103/PhysRevC.83.044912

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 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 collisions.

Laser-arc hybrid welding for the cover plate of ITER TF coil

Shiihara, Katsunori*; Makino, Yoshinobu*; Ogawa, Tsuyoshi*; Asai, Satoru*; Kanahara, Toshio*; Senda, Ikuo*; Okuno, Kiyoshi; Koizumi, Norikiyo; Matsui, Kunihiro

Proceedings of 26th International Congress on Applications of Lasers & Electro-Optics (ICALEO 2007) (CD-ROM), p.316 - 324, 2007/10

The toroidal field coil is manufactured as one of superconducting coil systems in the ITER. For welding the cover plate of TF coil, the prevention of the thermal effect on the coil and the deformation of the whole coil are required. Moreover, the application of high efficient welding is required in consideration for the productivity. Therefore, laser-arc hybrid welding process was investigated for the application to the cover plate welding, because its process is superior in the tolerance of the joint gap and the ease of the control for the heat input. In the experiment, it was confirmed that the application of laser-arc hybrid welding with the double gas shielding for high concentration arc and the filler wire for controlling the deposit amount is effective in the joint gap up to 0.8mm. Besides, twin spot laser head with the arc was developed in order to weld the both sides of cover plate simultaneously. By the optimization of welding condition for twin spot laser-arc hybrid welding process, it was confirmed to be effective in the prevention of the gap movement during welding and the acquisition of the proper penetration without the weld defect. Finally, the effectiveness of laser-arc hybrid welding for the welding deformation and the weldability on the quality was verified by the scale model test with the actual shape.

Test results of HTTR control system

Motegi, Toshihiro; Iigaki, Kazuhiko; Saito, Kenji; Sawahata, Hiroaki; Hirato, Yoji; Kondo, Makoto; Shibutani, Hideki; Ogawa, Satoru; Shinozaki, Masayuki; Mizushima, Toshihiko; et al.

JAEA-Technology 2006-029, 67 Pages, 2006/06

JAEA-Technology-2006-029.pdf:3.07MB

The plant control performance of the IHX helium flow rate control system, the PPWC helium flow rate control system, the secondary helium flow rate control system, the inlet temperature control system, the reactor power control system and the outlet temperature control system of the HTTR are obtained through function tests and power-up tests. As the test results, the control systems show stable control response under transient condition. Both of inlet temperature control system and reactor power control system shows stable operation from 30% to 100%, respectively. This report describes the outline of control systems and test results.

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

https://doi.org/10.1088/0029-5515/43/7/314

no abstracts in English

Report of ITPA (International Tokamak Physics Activity) Meeting, 3

Ninomiya, Hiromasa; Takamura, Shuichi*; Wakatani, Masahiro*; Fujita, Takaaki; Fukuda, Takeshi; Toi, Kazuo*; Ogawa, Yuichi*; Takizuka, Tomonori; Miura, Yukitoshi; Hatae, Takaki; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 78(7), p.692 - 694, 2002/07

http://ci.nii.ac.jp/naid/10009260365

The second ITPA (International Tokamak Physics Activity) meeting was held at General Atomics (San Diego) and Princeton Plasma Physics Laboratory (Princeton) in U.S.A. In the meeting, topical physics group meetings of "Coordinating Committee", "Transport and Internal Barrier Physics", "Confinement Database and Modeling", "Edge and Pedestal Physics", "Scrape-off-layer and Divertor Physics", and "Diagnostics" were carried out. In getting many participants from Japan, Europe, Russia, ITER international team and U.S.A., the active discussions were carried out. On the other hand, the topical group members concerned that the contribution from Japan will be decreased if the experimental period of JT-60U is reduced. Here, the outline of discussions in each topical group is reported.

Effect of flow field on colloid deposition in filtration process of polystyrene latex particles through columns packed glass beads

Chinju, H.*; Nagasaki, Shinya*; Tanaka, Satoru*; Sakamoto, Yoshiaki; Takebe, Shinichi; Ogawa, Hiromichi

Journal of Nuclear Science and Technology, 38(8), p.645 - 654, 2001/08

https://doi.org/10.3327/jnst.38.645

no abstracts in English

Sorption and desorption kinetics of Np(V) on magnetite and hematite

Nakata, Kotaro*; Nagasaki, Shinya*; Tanaka, Satoru*; Sakamoto, Yoshiaki; Tanaka, Tadao; Ogawa, Hiromichi

Radiochimica Acta, 88(8), p.453 - 457, 2000/12

https://doi.org/10.1524/ract.2000.88.8.453

Sorption kinetics of Np(V) on magnetite and hematite were investigated, and a sequential desorption method was applied to investigate changes in the chemical form of Np sorbed according to the amount of time they were in contact with the Np solution. It was found that the sorption process consists of fast sorption and slow sorption which reaches equilibrium in 1 h. From the results of sorption and desorption kinetics, it was concluded that the equilibrium between various chemical forms of sorbed Np was achieved in about 1 week, although the amount of sorbed Np reached an equilibrium in only 1 h.