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.

News from Broader Approach activities, 58

Hoshino, Kazuo; Matsunaga, Go; Okumura, Yoshikazu

Purazuma, Kaku Yugo Gakkai-Shi, 91(12), p.802 - 803, 2015/12

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2015_12/jspf2015_12-802.pdf

Holding of the 17th IFERC Project Committee (PC), the 16th IFMIF/EVEDA-PC and the progress of the JT-60SA were reported. In the IFERC-PC, total 33 participated including Maisonnier chairperson, JA-EU committee, experts and project members. They reported the status of each activity, discussed the planning of project 2016 and revised plan, and concluded technical advice to the BA Steering Committee (SC). In the IFMIF/EVEDA-PC, total 27 participated including Takatsu chairperson, JA-EU committee, experts and project members. They reported the status of each activity, discussed the planning of project 2016 and revised plan, and the BA-SC recommended the endorsement of the new project plan. In the JT-60SA, a rotary crane for assembly of the troidal field coil has been installed. The disassembly of the constraint jigs of the vacuum vessel which completed 340 assembly has been progressed. 6 high temperature superconductor current leads for the troidal field coils had been delivered from EU.

Development of magnetic sensors for JT-60SA

Takechi, Manabu; Matsunaga, Go; Sakurai, Shinji; Sasajima, Tadayuki; Yagyu, Junichi; Hoshi, Ryo*; Kawamata, Yoichi; Kurihara, Kenichi; JT-60SA Team; Nishikawa, T.*; et al.

Fusion Engineering and Design, 96-97, p.985 - 988, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.06.108

Estimation of the lifetime of resin insulators against baking temperature for JT-60SA in-vessel coils

Sukegawa, Atsuhiko; Murakami, Haruyuki; Matsunaga, Go; Sakurai, Shinji; Takechi, Manabu; Yoshida, Kiyoshi; Ikeda, Yoshitaka

Fusion Engineering and Design, 98-99, p.2076 - 2079, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.06.018

The JT-60SA project is a EU - JA satellite tokamak under Broader Approach in support of the ITER project. In-vessel coils are designed and assembled by JA. The resin-insulator is required to have a heat resistance against the baking temperature of vacuum vessel of 200C (40000 hour). Thus the assessment of the heat load is fundamental for the design of the coils. However, the estimation of the lifetime of resin-insulator under the high-temperature region has not been examined. In the present study, the estimation of the lifetime of seven candidate resin-insulators such as epoxy resin and cyanate-ester resin under the 220C temperature region have been performed for the current coils design. Weight reduction of the seven candidate insulators was measured at different heating times under 180C, 200C and 220C environment using three thermostatic ovens, respectively. The reduction of the insulators has been used as input for Weibull-analysis towards Arrhenius-plot. Lifetime of the resins has been estimated for the first time at the high temperature region by the plot. Lifetime of the resin-insulators have been evaluated and discussed as well as the available temperature of the in-vessel coils.

News from Broader Approach activities, 56

Hoshino, Kazuo; Matsunaga, Go; Okumura, Yoshikazu

Purazuma, Kaku Yugo Gakkai-Shi, 91(8), p.561 - 562, 2015/08

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2015_08/jspf2015_08-561.pdf

The new construction of Joint Research Building for the DEMO R&D at IFERC, progress of the IFMIF Prototype Accelerator and the Satellite Tokamak (JT-60SA) project were reported. The Joint Research Building processing the construction as a new place where carry out a part of project for the DEMO R&D in the rest of the BA activity period and it mainly consists of the laboratory/material testing room for the material evaluation and Be production room for handling of the metal beryllium. For the IFMIF Prototype Accelerator, completed the repairs and test run of the Interlock, successful of the continuity rated proton beam, then after setting of the radiation control area, successful production of the deuterium ion beam. For the JT-60SA, the installation of a Helium refrigerator which is one of the world's largest and a He buffer tank have been completed. The 4th Research Coordination meeting was held and they discussed the research plan and theme for the experiment proposal of JT-60SA.

News from Broader Approach activities, 55

Hoshino, Kazuo; Matsunaga, Go; Okumura, Yoshikazu

Purazuma, Kaku Yugo Gakkai-Shi, 91(6), p.430 - 431, 2015/06

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2015_06/jspf2015_06-430.pdf

Holding of the 16th BA Steering Committee and progress of the Satellite Tokamak (JT-60SA) project were reported. There were 33 participants for the 16th BA Steering Committee, including 3 committee members and 10 specialists from EU, 4 committee and 11 specialists from JP, each project leaders and project committee chair persons, and they approved for update of the 2014 Annual Report and the Work Plan of IFMIF/EVEDA, the IFERC and the Satellite Tokamak project. In the construction of JT-60SA, the component carry-in from EU and the assembly has been progressed steadily in JP. To announce for these progressing, a ceremony was held and 200 people concerned in EU-JP attended. The 22nd JT-60SA Technical Coordination Meeting was held. 73 people EU-JP joined and had discussion regarding the design, status of production, examination of assembly and the integrate operation in the future. To send out information to the domestic community a major event in the BA activities.

News from Broader Approach activities, 53

Ishii, Yasutomo; Matsunaga, Go; Okumura, Yoshikazu

Purazuma, Kaku Yugo Gakkai-Shi, 91(2), p.161 - 162, 2015/02

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2015_02/jspf2015_02-161.pdf

Success of the first beam of injector for IFMIF prototype accelerator, accomplishment of liquid Lithium Target validation test of the IFMIF/EVEDA and the progress of Satellite Tokamak (JT-60SA) were reported. The IFMIF/EVEDA project are performed in International Fusion Energy Research Center at Rokkasho under the BA agreement, installation and adjustment of injector for IFMIF accelerator were completed and the adjustment beam test has started from Nov. 2014. For the engineering validation test, formability of the Lithium Target which become the neutron source, the Lithium Test Loop of real scale was fabricated in Oarai and test has been conducted for 2 years. At the end of Oct. 2014, made an exceeding achievement and successfully concluded. In the construction of JT-60SA at Naka, the design of each part has been performing with the 3D CAD soft CATIA. The update with previous state discloses on JT60-SA HP. To disseminate information to the domestic community a major event in the BA activities.

Experimental analyses and predictive simulations of toroidal rotation driven by the neoclassical toroidal viscosity in rippled tokamaks

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Matsunaga, Go; Shinohara, Koji; Yoshida, Maiko; Matsuyama, Akinobu; Ide, Shunsuke; Urano, Hajime

Nuclear Fusion, 54(11), p.114005_1 - 114005_14, 2014/11

https://doi.org/10.1088/0029-5515/54/11/114005

Extension of kinetic-magnetohydrodynamic model to include toroidal rotation shear effect and its application to stability analysis of resistive wall modes

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go; Honda, Mitsuru; Hayashi, Nobuhiko; Ide, Shunsuke

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Extension of the kinetic-magnetohydrodynamic (MHD) model is presented to include toroidal rotation shear effect for the first time. The sheared rotation is introduced through generalization of the guiding center Lagrangian, yielding two additional terms in a quadratic form of mode-particle resonance. Additionally, another new term is introduced by using the equilibrium distribution function with rotation effect. These three terms are overlooked in conventional models. The new model is applied to stability analysis of resistive wall modes (RWMs) successfully. Numerical results show that the rotation shear reduces RWM growth rates further, which is consistent with experimental results.

News from Broader Approach activities, 50

Ishii, Yasutomo; Matsunaga, Go

Purazuma, Kaku Yugo Gakkai-Shi, 90(8), p.506 - 507, 2014/08

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2014_08/jspf2014_08-506.pdf

This time, the 5th LIPAc Technical Meeting on June 3-5, Acceptance testing of the RF system for the prototype accelerator, start assembling the JT-60SA vacuum vessel from May, and the 3rd EU-Japan JT-60SA research coordination meeting on May 19-23 are reported. The 5th LIPAc Technical Meeting, Installation in Rokkasho, situation of adjustment work, and preparation status, 38 topics from each agency in each equipment have been reported. In addition, the performance test of RF system for the prototype accelerator that Europe procures was conducted under JAEA, F4E and the project team attendance. Good test results are obtained. The Superconducting tokamak JT-60SA vacuum vessel has started assembling from May. The 3rd JT-60SA EU-Japan Research Coordination Meeting, formulation of a research plan of JT-60SA, and discussion and information exchange of Japanese and EU joint research on JT-60SA were done. To disseminate information to the domestic community a major event in the BA activities.