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Asakura, Nobuyuki; Shinya, Kichiro*; Tobita, Kenji; Hoshino, Kazuo; Shimizu, Katsuhiro; Uto, Hiroyasu; Someya, Yoji; Nakamura, Makoto; Ono, Noriyasu*; Kobayashi, Masahiro*; et al.
Fusion Science and Technology, 63(1T), p.70 - 75, 2013/05
no abstracts in English
Asakura, Nobuyuki; Shinya, Kichiro*; Tobita, Kenji; Hoshino, Kazuo; Shimizu, Katsuhiro; Uto, Hiroyasu; Someya, Yoji; Nakamura, Makoto; Ono, Noriyasu*; Kobayashi, Masahiro*; et al.
Fusion Science and Technology, 63(1T), p.70 - 75, 2013/05
Times Cited Count：14 Percentile：72.01(Nuclear Science & Technology)Design study of poloidal field coil (PFC) locations and current distribution for the advanced divertor in the Demo tokamak reactor was presented. Concept of the super-X divertor (SXD) for Demo reactor has an outer divertor leg longer than the conventional divertor, and it extends outboard to increase both the target wetted area and connection length to the outer target (
). Equilibrium calculation code, TOSCA, was developed by introducing two parameters, i.e. super-X null radius (
) and a ratio of the poloidal flux at the super-X null to that at the separatrix (
). Some SXD magnetic configurations with minimal number of PFCs located outside toroidal field coil (TFC) were Demonstrated. Locations of the divertor target were also investigated. It was found that the flux expansion can be increased up to 4-10 depending on the target location and , and that SXD has an advantage to increase with . Thus, the divertor plasma temperature is expected to decrease at the same upstream plasma density. On the other hand, large currents for the divertor PFCs were necessary. Other arrangements of PFCs such as (1) larger and (2) inside TFC, can reduce the PFC currents.
Asakura, Nobuyuki; Ono, Noriyasu*; Tanaka, Hirohiko*; Kawashima, Hisato; Nakano, Tomohide
Journal of Nuclear Materials, 390-391, p.364 - 367, 2009/06
Times Cited Count：4 Percentile：30.43(Materials Science, Multidisciplinary)Characteristics of the fluctuations at three locations (Low-Field-Side midplane, X-point, and High-Field-Side SOLs) of the JT-60U SOL were investigated in L-mode and ELMy H-mode plasmas. Influence of their poloidal asymmetry at the LFS and HFS on the parallel plasma flow was investigated. For the L-mode, poloidal asymmetry in djs/
js
was enhanced at the LFS midplane (40-60%), while it was small (10-20%) at the HFS SOL and LFS X-point. On the other hand, djs/js was similar (20-30
) for the ELMy H-mode. Statistical properties (Skewness) and their poloidal asymmetry were different in the ELMy H-mode and L-mode plasmas. In the ELMy H-mode, positive S (= 0.3-0.5) was seen near the separatrix. However, in the L-mode, larger S (=0.5-0.9) was observed at the LFS midplane, and it extended to the far SOL (r 10 cm). In-out asymmetry in the intermittent transport will contribute to produce the SOL flow pattern.
Tanaka, Hirohiko*; Ono, Noriyasu*; Asakura, Nobuyuki; Tsuji, Yoshiyuki*; Kawashima, Hisato; Takamura, Shuichi*; Uesugi, Yoshihiko*; JT-60U Team
Nuclear Fusion, 49(6), p.065017_1 - 065017_7, 2009/06
Times Cited Count：38 Percentile：79.52(Physics, Fluids & Plasmas)Comparison between fluctuation characteristics at high-field-side (HFS) and low-field-side (LFS) scrape off layers (SOLs) has been made, for the first time, in the L mode plasma of the JT-60U tokamak using reciprocating Langumuir probes. Statistical analysis based on probability distribution function (PDF) was employed to describe intermittent (non-diffusion) transport in SOL plasma fluctuations. The positive bursty events appeared most frequently at LFS midplane associated with blobby plasma transport, then the PDF is strongly skewed positively, while the PDF in HFS SOL is close to Gaussian distribution. Conditional averaging analysis of the positive bursty events at LFS midplane indicates the intermittent feature with a rapid increase and a slow decay is similar to that of plasma blobs theoretically predicted. Statistical self-similarity was also investigated with Fourier power spectrum and statistics of waiting-time and duration-time of the fluctuation.
Tanaka, Hirohiko*; Ono, Noriyasu*; Asakura, Nobuyuki; Tsuji, Yoshiyuki*; Kajita, Shin*
no journal, ,
no abstracts in English
Tanaka, Hirohiko*; Ono, Noriyasu*; Asakura, Nobuyuki; Tsuji, Yoshiyuki*; Kajita, Shin*
no journal, ,
We have investigated fast temporal electrostatic fluctuations measured in detached SOL/divertor plasmas of JT-60U. Application of statistical analysis techniques clarified that fluctuations of ion saturation current measured around X-point had a number of positive spikes under the detached condition, but not under the attached condition. This result suggests that an intermittent phenomenon occurred near the detached divertor leg would generate blob-like structures in divertor region. In this presentation, we will show the results obtained by using several analysis techniques (e.g. spectral analysis, conditional averaging, and so on). After that, we will compare the results between under the detached and attached condition.
