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Asakura, Nobuyuki; Nakano, Tomohide; Naito, Osamu; Oyama, Naoyuki
Journal of Nuclear Materials, 415(Suppl.1), p.S318 - S321, 2011/09
Times Cited Count：5 Percentile：36.88(Materials Science, Multidisciplinary)Impurity gas seeding is considered as the primary technique to decrease the heat loading to the divertor. Characteristics of the divertor plasma and radiation was investigated. Distribution of the impurity radiation in the edge and divertor was different depending on the impurity species. For Argon seeding, radiation loss in the main edge increased compared to Neon seeding cases. ELM characteristics changed from Type-I to Type-III for the intense Ar seeding, and detachment was produced. Dynamics of the transition from detachment to re-attachment was investigated. When the Ar gas puff rate was reduced, Type-I ELM activity appeared accompanied by a reduction in the edge radiation loss. Time scale of the re-attachment was short (0.4 s) compared to the transition from attached to detached divertor (1 s), which was affected by change in the edge transport barrier. In-out asymmetries in 
and ion flux became large in the re-attachment, and influence of the carbon-influx was increased.
Hoshino, Kazuo; Shimizu, Katsuhiro; Takizuka, Tomonori; Asakura, Nobuyuki; Nakano, Tomohide
Journal of Nuclear Materials, 415(Suppl.1), p.S549 - S552, 2011/08
Times Cited Count：10 Percentile：58.64(Materials Science, Multidisciplinary)no abstracts in English
Koubiti, M.*; Nakano, Tomohide; Godbert-Mouret, L.*; Marandet, Y.*; Rosato, J.*; Stamm, R.*
Journal of Nuclear Materials, 415(Suppl.1), p.S1151 - S1154, 2011/08
Times Cited Count：4 Percentile：31.26(Materials Science, Multidisciplinary)The C IV (
= 6-7) spectral lines emitted from the JT-60U detached plasmas were observed with a high-wavelength resolution spectrometer and the profiles were analyzed with a PPP code. The analysis indicates that the spectral profiles were broadened with both the Doppler and the Stark effects. From these effects, the electron temperature and density were evaluated. Along the viewing chord for the X-point, the electron temperature and density was determined to be 3 eV and 
, respectively. These are similar to those determined from the intensity ratio of C IV lines (6.3 eV and 
, respectively). The high density plasma around the X-point was confirmed with these independent methods.
Kawashima, Hisato; Hoshino, Kazuo; Shimizu, Katsuhiro; Takizuka, Tomonori; Ide, Shunsuke; Sakurai, Shinji; Asakura, Nobuyuki
Journal of Nuclear Materials, 415(Suppl.1), p.S948 - S951, 2011/08
Times Cited Count：8 Percentile：51.42(Materials Science, Multidisciplinary)The divertor design of the JT-60SA tokamak device is finalized according to the engineering requirements and the physical analyses with the SONIC code simulations. Assuming the steady-state high beta core plasmas with 41 MW heating power, high heat and particle fluxes flowing out from core to SOL arrive at the divertor targets and give a large heat load. From the engineering viewpoint, the allowable heat load is restricted below 15 MW/m
by the tolerability of the target material and structure. As a scenario to reduce the heat load, the vertical target configuration is adopted to receive the heat load on the wide area. In addition, the V-shaped corner is set to enhance the recycling at the outer side divertor where receives a relatively large heat load. Then, the remote radiative cooling is optimized by control of the D
gas puffing, the impurity seeding and the divertor pumping.
Tanaka, Yasunori*; Smirnov, R. D.*; Pigarov, A. Y.*; Takenaga, Hidenobu; Asakura, Nobuyuki; Uesugi, Yoshihiko*; Ono, Noriyasu*
Journal of Nuclear Materials, 415(Suppl.1), p.S1106 - S1110, 2011/08
Times Cited Count：11 Percentile：61.73(Materials Science, Multidisciplinary)Dust can be an important contributor to impurity contamination of the core and scrape-off-layer (SOL) plasmas in tokamak fusion devices. This is the first report about investigation of transport of carbon dust particles in case of JT-60U tokamak using the dust transport code (DUSTT). The DUSTT code takes into account various plasma-dust interaction processes. In the present report, background plasma parameters in JT-60U such as densities and temperatures of electron, ion and neutral atom were computed with the UEDGE code. Three dimensional trajectories, temperature evolution, and radius variation of dust particles launched from different positions at the inner divertor, the outer divertor and the dome structure in JT-60U tokamak were simulated numerically to study dynamics and transport of dust particles there. As a result, the lifetime of dust particles is dependent mainly on the ion density in trajectories in final term.
Fukumoto, Masakatsu; Nakano, Tomohide; Itami, Kiyoshi; Wada, Takaaki*; Ueda, Yoshio*; Tanabe, Tetsuo*
Journal of Nuclear Materials, 415(Suppl.1), p.S705 - S708, 2011/08
Times Cited Count：5 Percentile：36.88(Materials Science, Multidisciplinary)Tungsten coating on the first wall in ITER is proposed to reduce in-vessel tritium retention. However, it is possibility that carbon based materials would be used at high heat load components such as limiter. To predict the tritium retention in tungsten coating, it is essential to investigate the effects of carbon impurity on deuterium retention in tungsten coating. In this study, effects of carbon impurity on deuterium retention in the tungsten coating exposed to JT-60U divertor plasmas were investigated. Deuterium was trapped by carbon which was implanted and accumulated in the tungsten coating during the plasma discharge. D/C ration of 0.04-0.08 in the tungsten coating was reached to 1/2-1/4 compared to T/C ration in carbon co-deposition layer. Therefore, simultaneous use of carbon armor materials and tungsten coating would enhance tritium retention in tungsten coating.
Alimov, V.; Tyburska, B.*; Ogorodnikova, O. V.*; Roth, J.*; Isobe, Kanetsugu; Yamanishi, Toshihiko
Journal of Nuclear Materials, 415(Suppl.1), p.S628 - S631, 2011/08
Times Cited Count：15 Percentile：71.97(Materials Science, Multidisciplinary)Deuterium retention in porous vacuum plasma spraying tungsten coating exposed at various temperatures to a low-energy, high flux (10
D/ms) pure D and helium-seeded D plasmas was examined by thermal desorption spectroscopy and the nuclear reaction. Under exposure to pure D plasma (76 eV D
) at 340-560 K, the D concentration reaches 1
2 at.% at depths of several micrometers, while at temperatures above 700 K the D concentration is below 10
at.% and deuterium is retained over the whole thickness of the coating. Seeding of 76 eV He into the D plasma reduces the D retention at temperatures of 400-600 K. However, at temperature above 700 K, the D retention becomes comparable to that for pure D plasma exposure.
Nakano, Tomohide; JT-60 Team
Journal of Nuclear Materials, 415(Suppl.1), p.S327 - S333, 2011/08
Times Cited Count：24 Percentile：83.11(Materials Science, Multidisciplinary)It has been observed that with increasing toroidal rotation velocity inside the 
= 1 layer in the direction opposite to the plasma current, sawtooth activity becomes moderate and tungsten accumulation becomes significant. The tungsten accumulation level is significantly reduced from this trend in the case when electron cyclotron wave or high energy neutral beam is injected into the plasma core. In contrast, the tungsten accumulation is kept high by the electron cyclotron wave injection into the peripheral region.
Pitcher, C. S.*; Andrew, P.*; Barnsley, R.*; Bertalot, L.*; Counsell, G. G.*; Encheva, A.*; Feder, R. E.*; Hatae, Takaki; Johnson, D. W.*; Kim, J.*; et al.
Journal of Nuclear Materials, 415(Suppl.1), p.S1127 - S1132, 2011/08
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)