JOPSS - Search Results

Journal Articles

Density stratification breakup by a vertical jet; Experimental and numerical investigation on the effect of dynamic change of turbulent Schmidt number

Abe, Satoshi; Studer, E.*; Ishigaki, Masahiro; Shibamoto, Yasuteru; Yonomoto, Taisuke

Nuclear Engineering and Design, 368, p.110785_1 - 110785_14, 2020/11

https://doi.org/10.1016/j.nucengdes.2020.110785

Times Cited Count：10 Percentile：75.92(Nuclear Science & Technology)

Journal Articles

Pressure-induced stacking disorder in boehmite

Ishii, Yusuke*; Komatsu, Kazuki*; Nakano, Satoshi*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*

Physical Chemistry Chemical Physics, 20(24), p.16650 - 16656, 2018/06

https://doi.org/10.1039/C8CP02565G

Times Cited Count：4 Percentile：17.83(Chemistry, Physical)

The structure of an aluminum layered hydroxide, boehmite (-AlOOH), as a function of pressure was studied by using synchrotron X-ray and neutron diffraction. Peak broadening and subsequent splitting, which are only found for hkl (h 0) peaks in the X-ray diffraction patterns above 25 GPa, are explained by stacking disorder accompanied with a continuously increasing displacement of the AlO $_{6}$ octahedral layer along a-axis. This finding could be the first experimental result for the pressure-induced stacking disorder driven by the continuous layer displacement. The magnitude of the layer displacement was estimated from the X-ray scattering profile calculation based on the stacking disordered structure model. Hydrogen bond geometries of boehmite, obtained by structure refinements on the observed neutron diffraction patterns for deuterated sample up to 10 GPa, show linearly approaching O-D covalent and DO hydrogen bond distances and they could merge below 26 GPa. The pressure-induced stacking disorder would make the electrostatic potential of hydrogen bonds asymmetric, yielding less chance for the proton-tunnelling.

Journal Articles

Study of ohmic loss of high power polarizers at 170 GHz for ITER

Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi

Fusion Engineering and Design, 81(19), p.2249 - 2256, 2006/09

https://doi.org/10.1016/j.fusengdes.2006.03.005

Times Cited Count：4 Percentile：30.68(Nuclear Science & Technology)

High efficiency ECCD operations need an obliquely propagating electromagnetic wave with a specified elliptical polarization in magnetized plasma. The polarizer is necessary in order to excite the specified polarization. In the ITER design for ECCD system, the transmitted power per one waveguide is planned to be 1 MW as CW operation. The ohmic loss evaluation code for grooved mirror polarizers which calculates tangential magnetic field to the material at exterior to the groove and inside of that was developed. Calculation results were made sure of agreement with high power experiment qualitatively, and validity of the evaluation code has been confirmed.

Journal Articles

Thermal analysis and Ohmic loss estimation of polarizer for ITER ECCD system

Saigusa, Mikio*; Takahashi, Koji; Kashiwa, Yoshinori*; Oishi, Shimpei*; Hoshi, Yuki*; Nakahata, Hiroyuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi*

Fusion Engineering and Design, 74(1-4), p.473 - 478, 2005/11

https://doi.org/10.1016/j.fusengdes.2005.06.087

Times Cited Count：4 Percentile：30.51(Nuclear Science & Technology)

The specification of an electron cyclotron current driving (ECCD) system in International Thermonuclear Experimental Reactor (ITER) demands severe operational conditions for transmission lines and polarizers. For evaluating Ohmic loss of a miter bend type polarizer, the six polarizers were made of chromium copper alloy, installed in miter bends and tested at a frequency of 170GHz, rf power of 441kW and pulse duration of 0.1-6 seconds. The increase in temperature on the back of the grooved mirrors has been measured with thermo couplers during high power rf pulses. The Ohmic loss of grooved mirrors strongly depends on the rotation angle of the polarization plane of the incident waves and the mirror rotation in high power experiments, for example the Ohmic loss distributed from 0.2% to1.6%. The thermal analysis of grooved mirror has been performed with the 3D FEM code: FEVA. The all strange behavior of Ohmic loss of polarizers could be explained, theoretically.

Journal Articles

Twin intersection in tensile deformed -TiAl intermetallic compounds

Sawai, Tomotsugu; Hishinuma, Akimichi

Journal of Physics and Chemistry of Solids, 66(2-4), p.335 - 338, 2005/02

https://doi.org/10.1016/j.jpcs.2004.06.059

Times Cited Count：14 Percentile：49.98(Chemistry, Multidisciplinary)

TiAl intermetallic compounds are potential materials for high temperature structural applications. They have also low induced radio-activity and good radiation resistance, which make these alloys very attractive in nuclear applications. Their ductility at low temperatures should be, however, still improved and their deformation mechanism is of great concern. In this study, intersections of deformation twins in -TiAl grains were examined in Ti-47at%Al alloy specimens tensile-tested at 873 K. Transmission electron microscopy (TEM) revealed 1/2110]{111} ordinary-type dislocations and 1/6112]{111} twins in deformed -TiAl grains. Some -TiAl grains contained twins on two different {111} planes, which intersect along 110] directions (type-1). No twin intersection along 101] (type-2) was observed, which was often reported in compressed specimens. Results are discussed with the Schmid factor distributions of twinning systems and ordinary slip systems as the function of tensile directions.

Journal Articles

Study of ohmic loss of high power polarizers at 170 GHz for ITER

Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Hoshi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

Proceedings of 2004 International Symposium on Microwave Science and Its Application to Related Fields (Microwave 2004), p.527 - 530, 2004/07

An electron cyclotron current drive (ECCD) system is, especially, necessary to suppress the neoclassical tearing mode instability in ITER. The polarizers are one of the important components in the ECCD system, to generate optimum polarization for an efficient ECCD. An ohmic loss of the polarizers is evaluated, when 170GHz, high power RF wave taransmits, in oreder to investigate its performance. The maximum temperature increase on the back plate of the deep grooved and the conventinal type were 65 $^{circ}$ C and 30 $^{circ}$ C, respectively. RF power and pulse were 441kW and 6sec, respectively. The dependence of temperature increase on the plolarizer angle obtained in the experiment agrees with the calculation, qualitatively. It was also found that the significant reduction of ohmic loss on the polarizers was achievable with the optimized rotation angle of the linearly polarized incident wave.