Effects of toroidal rotation shear and magnetic shear on thermal and particle transport in plasmas with electron cyclotron heating on JT-60U

Yoshida, Maiko; Honda, Mitsuru; Narita, Emi*; Hayashi, Nobuhiko; Urano, Hajime; Nakata, Motoki; Miyato, Naoaki; Takenaga, Hidenobu; Ide, Shunsuke; Kamada, Yutaka

Nuclear Fusion, 55(7), p.073014_1 - 073014_9, 2015/07

https://doi.org/10.1088/0029-5515/55/7/073014

Conditions without the increases in the thermal and particle transport with ECH have been experimentally investigated in positive magnetic shear (PS), weak magnetic shear (WS) and reversed magnetic shear (RS) plasmas with internal transport barriers (ITBs) on JT-60U. The ion heat diffusivity around an internal transport barrier in the ion temperature (-ITB) remains constant with ECH when a large negative toroidal rotation shear is formed before the ECH. The condition does not depend on the electron to ion temperature ratio (/) and ECH power. The electron heat diffusivity around a -ITB stays constant with ECH when the magnetic shear is negative around the Te-ITB region. Effective particle transport remains constant or reduces during ECH under the condition of negative magnetic shear.

Physics comparison and modelling of the JET and JT-60U core and edge; Towards JT-60SA predictions

Garcia, J.*; Hayashi, Nobuhiko; Baiocchi, B.*; Giruzzi, G.*; Honda, Mitsuru; Ide, Shunsuke; Maget, P.*; Narita, Emi*; Schneider, M.*; Urano, Hajime; et al.

Nuclear Fusion, 54(9), p.093010_1 - 093010_13, 2014/09

https://doi.org/10.1088/0029-5515/54/9/093010

Analysis of / effect on confinement properties

Narita, Emi*; Takizuka, Tomonori*; Hayashi, Nobuhiko; Fujita, Takaaki; Ide, Shunsuke; Honda, Mitsuru; Isayama, Akihiko; Itami, Kiyoshi; Kamada, Yutaka; Tanaka, Yasuyuki*; et al.

Plasma and Fusion Research (Internet), 7(Sp.1), p.2403102_1 - 2403102_5, 2012/07

https://doi.org/10.1585/pfr.7.2403102

Real-time observation of initial thermal oxidation on Si(110)-162 surfaces by O 1s photoemission spectroscopy using synchrotron radiation

Suemitsu, Maki*; Kato, Atsushi*; Togashi, Hideaki*; Konno, Atsushi*; Yamamoto, Yoshihisa*; Teraoka, Yuden; Yoshigoe, Akitaka; Narita, Yuzuru*; Enta, Yoshiharu*

Japanese Journal of Applied Physics, Part 1, 46(4B), p.1888 - 1890, 2007/04

https://doi.org/10.1143/JJAP.46.1888

Initial oxidation of Si(110) surface has been investigated by using real-time X-ray photoemission spectroscopy. The time evolution of the O 1s spectrum shows occurrence of rapid oxidation just after the introduction of the oxygen molecules, which is evidenced by the considerable peak intensity corresponding to oxygen exposure of as low as 1.5L (1L=1.3310 Pa s). This initial oxide is dominated by a state with a relatively low binding energy, which is gradually replaced by a state with a relatively high binding energy with the increase of the oxygen exposure, resulting in the low-KE shift of the O 1s peak. Comparison with previously reported O 1s spectra from dry-oxidized Si(111) surface suggests oxidation at or around the adatoms of Si(110)-162 clean surface as a likely oxidation state for this low-binding-energy peak.

Real-time observation of initial thermal oxidation on Si(110)-162 surface by photoemission spectroscopy

Suemitsu, Maki*; Kato, Atsushi*; Togashi, Hideaki*; Konno, Atsushi*; Yamamoto, Yoshihisa*; Teraoka, Yuden; Yoshigoe, Akitaka; Enta, Yoshiharu*; Narita, Yuzuru*

ECS Transactions, 3(2), p.311 - 316, 2006/00

https://doi.org/10.1149/1.2356291

Initial thermal oxidation of Si(110) surface has been investigated by using real-time X-ray photoemission spectroscopy with synchrotron radiation. The Si(110) initial oxidation is characterized by presence of a rapid oxidation just after the introduction of gaseous oxygen molecules. Peak separation of the O1s photoemission spectra suggests the presence of at least two distinct oxidation sites on the surface, which may reflect the complicated surface structure of the Si(110)-162 reconstruction.

Real time SR-XPS on initial oxidation process at Si(110)-162 surface

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Hasegawa, Satoshi*; Goto, Seiichi*; Nakano, Takuya*; Suemitsu, Maki*; Narita, Yuzuru*; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

We have investigated the initial oxidation process on an Si(110)-162 surface by real time synchrotron radiation photoemission spectroscopy (SR-XPS). As a result, a rapid initial oxidation regime was found to exist on this surface, which is not present on other crystal orientations. Analyses of the O1s spectra suggest insertion of oxygen atoms at the Si-Si bonds as the predominant process during initial oxidation. The rapid initial oxidation is accompanied by decrease of the Si2p subpeak that is related to Si(110)-162 reconstruction, indicating the preferential oxidation at the pentagon pair.

Ultrathin oxide formation process on Si(110)-162 surface and its interface structure

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Suemitsu, Maki*; Narita, Yuzuru*; Teraoka, Yuden; Yoshigoe, Akitaka

no journal, , 

We have investigated oxidation at Si(110) surfaces via real-time photoemission spectroscopy with synchrotron radiation. We have already obtained the following information that rapid initial oxidation region was in the early stage of oxidation and one of shifted Si2p core level components was decreased with increasing oxide. Therefore, we focused our interest to the topmost ultrathin oxide-layer formation and investigated time evolution of oxide components of Si2p photoemission spectrum. All experiments were conducted at surface chemistry station of BL23SU in the SPring-8. The oxygen pressure was 1.010Pa and substrate temperature was 813 K. Consequently, concerning oxide components of Si2p during oxidation, the intensity of Si component was larger than that of Si until 1 ML oxidation.

Impact of Te/Ti on confinement properties with emphasis on profile shapes

Narita, Emi*; Takizuka, Tomonori*; Hayashi, Nobuhiko; Fujita, Takaaki; Ide, Shunsuke; Honda, Mitsuru; Tanaka, Yasuyuki*; Isayama, Akihiko; Itami, Kiyoshi; Fukuda, Takeshi*

no journal, , 

Gyrokinetic analyses of effects of toroidal rotation on heat transport in JT-60U

Narita, Emi; Honda, Mitsuru; Yoshida, Maiko; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke

no journal, , 

Toroidal rotation is the key to improve the energy confinement in tokamak plasmas. In JT-60U, it has been reported that electron heat transport is affected by the direction of toroidal rotation in the core region. In the plasma, an internal transport barrier is formed with the weak magnetic shear. Since the gradient of the radial electric field is weak in the core region, the effect of the gradient may be insignificant. In this study, it is shown that the change in the rotation direction can affect the linear growth rate by using the gyrokinetic flux-tube code GKW with the experimental parameters. In addition, the effects of the rotation direction are compared with the experiment, and physics mechanisms of changes in heat transport are discussed.

H-mode database and turbulence analyses of the current profile effect on improved electron energy confinement

Narita, Emi; Honda, Mitsuru; Hayashi, Nobuhiko; Takizuka, Tomonori*; Ide, Shunsuke; Itami, Kiyoshi; Isayama, Akihiko; Fukuda, Takeshi*

no journal, , 

no abstracts in English