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Journal Articles

Synergy of turbulent and neoclassical transport through poloidal convective cells

Asahi, Yuichi*; Grandgirard, V.*; Sarazin, Y.*; Donnel, P.*; Garbet, X.*; Idomura, Yasuhiro; Dif-Pradalier, G.*; Latu, G.*

Plasma Physics and Controlled Fusion, 61(6), p.065015_1 - 065015_15, 2019/05

 Times Cited Count:3 Percentile:28.55(Physics, Fluids & Plasmas)

The role of poloidal convective cells on transport processes is studied with the full-F gyrokinetic code GYSELA. For this purpose, we apply a numerical filter to convective cells and compare the simulation results with and without the filter. The energy flux driven by the magnetic drifts turns out to be reduced by a factor of about 2 once the numerical filter is applied. A careful analysis reveals that the frequency spectrum of the convective cells is well-correlated with that of the turbulent Reynolds stress tensor, giving credit to their turbulence-driven origin. The impact of convective cells can be interpreted as a synergy between turbulence and neoclassical dynamics.

Journal Articles

Turbulent generation of poloidal asymmetries of the electric potential in a tokamak

Donnel, P.*; Garbet, X.*; Sarazin, Y.*; Asahi, Yuichi; Wilczynski, F.*; Caschera, E.*; Dif-Pradalier, G.*; Ghendrih, P.*; Gillot, C.*

Plasma Physics and Controlled Fusion, 61(1), p.014003_1 - 014003_11, 2019/01

 Times Cited Count:7 Percentile:76.02(Physics, Fluids & Plasmas)

Poloidal asymmetries of the $$E times B$$ plasma flow are known to play a role in neoclassical transport. According to conventional neoclassical theory, the level of poloidal asymmetry of the electric potential is expected to be very small. In the present work, a general framework for the generation of axisymmetric structures of potential by turbulence is presented. Zonal flows, geodesic acoustic modes and convective cells are described by a single model. This is done by solving the gyrokinetic equation coupled to the quasi-neutrality equation. This calculation provides a predictive calculation of the frequency spectrum of flows given a specified forcing due to turbulence. It also shows that the dominant mechanism comes from zonal flow compression at intermediate frequencies, while ballooning of the turbulence Reynolds stress appears to be the main drive at low frequency.

Journal Articles

The Precise energy spectra measurement of laser-accelerated MeV/n-class high-Z ions and protons using CR-39 detectors

Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Kondo, Kiminori; Oda, Keiji*; Yamauchi, Tomoya*; Fukuda, Yuji

Plasma Physics and Controlled Fusion, 58(3), p.034013_1 - 034013_6, 2016/03

 Times Cited Count:16 Percentile:78.53(Physics, Fluids & Plasmas)

In order to understand the synergetic interplay between the Coulomb explosion of clusters and the background gas dynamics, we have conducted ion acceleration experiments using CO$$_2$$ clusters (250 nm in dia.) embedded in background H$$_2$$ gas with the J-KAREN laser (1 J, 40 fs, 10$$^{-10}$$ contrast) at JAEA-KPSI. By a careful analysis of etch pit positions on CR-39 and their structures including the etch pit growth behavior analysis with the multi-step etching technique, energy spectra for protons from the background gas and carbon/oxygen ions from the clusters are obtained separately. The maximum energies of protons and carbon/oxygen ions are determined as 1.6 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of the background gas ions induced by Coulomb explosion of clusters is discussed with the help from numerical simulations which employ a particle-in-cell (PIC) method including relaxation and ionization processes of plasma particles.

Journal Articles

Ion acceleration via "nonlinear vacuum heating" by the laser pulse obliquely incident on a thin foil target

Yogo, Akifumi*; Bulanov, S. V.; Mori, Michiaki; Ogura, Koichi; Esirkepov, T. Z.; Pirozhkov, A. S.; Kanasaki, Masato*; Sakaki, Hironao; Fukuda, Yuji; Bolton, P.; et al.

Plasma Physics and Controlled Fusion, 58(2), p.025003_1 - 025003_7, 2016/02

 Times Cited Count:5 Percentile:29.39(Physics, Fluids & Plasmas)

Journal Articles

Integrated tokamak modelling with the fast-ion Fokker-Planck solver adapted for transient analyses

Toma, Mitsunori; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Honda, Mitsuru; Ide, Shunsuke

Plasma Physics and Controlled Fusion, 57(9), p.095007_1 - 095007_9, 2015/09

 Times Cited Count:3 Percentile:17.93(Physics, Fluids & Plasmas)

Integrated tokamak modelling that enables the simulation of an entire discharge periodis indispensable for designing advanced tokamak plasmas. For this purpose, we extend the integrated code TOPICS to make it more suitable for transient analyses in the fast-ion part. The fast-ion Fokker-Planck solver is integrated into TOPICS at the same level as the bulk transport solver so that the time evolutions of the fast ion and the bulk plasma are consistent with each other as well as with the equilibrium magnetic field. The integrated code is applied to ramp-up simulations for JT-60SA and ITER to confirm its capability and effectiveness in transient analyses. In the integrated simulations, the coupled evolution of the fast ions, plasma profiles, and equilibrium magnetic fields are presented.

Journal Articles

On the spatial structure of solitary radial electric field at the plasma edge in toroidal confinement devices

Ito, Kimitaka*; Ito, Sanae*; Kamiya, Kensaku; Kasuya, Naohiro*

Plasma Physics and Controlled Fusion, 57(7), p.075008_1 - 075008_7, 2015/07

 Times Cited Count:18 Percentile:76.27(Physics, Fluids & Plasmas)

The solitary radial electric field in the edge of toroidal plasma is studied based on the electric field bifurcation model. Results are applied to tokamak and helical plasmas, and the dependence of the electric field structure on the plasma parameters and geometrical factors is analyzed. The order of magnitude estimate for tokamak plasma is not far from experimental observations. It is shown that, in helical plasmas, the height of electric field structure is reduced substantially owing to the ripple particle transport, while the width is influenced less. The implications of the results for the limit of achievable gradient in the H-mode pedestal are also discussed.

Journal Articles

Simulation of plasma current ramp-up with reduced magnetic flux consumption in JT-60SA

Wakatsuki, Takuma; Suzuki, Takahiro; Hayashi, Nobuhiko; Shiraishi, Junya; Ide, Shunsuke; Takase, Yuichi*

Plasma Physics and Controlled Fusion, 57(6), p.065005_1 - 065005_12, 2015/06

 Times Cited Count:8 Percentile:46.64(Physics, Fluids & Plasmas)

Journal Articles

Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall

Giroud, C.*; Jachmich, S.*; Jacquet, P.*; J$"a$rvinen, A.*; Lerche, E.*; Rimini, F.*; Aho-Mantila, L.*; Aiba, Nobuyuki; Balboa, I.*; Belo, P.*; et al.

Plasma Physics and Controlled Fusion, 57(3), p.035004_1 - 035004_20, 2015/03

 Times Cited Count:51 Percentile:96.4(Physics, Fluids & Plasmas)

This paper reports the progress made at JET-ILW on integrating the requirements of the reference ITER baseline scenario with normalized confinement factor of 1, at a normalized pressure of 1.8 together with partially detached divertor whilst maintaining these conditions over many energy confinement times. The 2.5 MA high triangularity ELMy H-modes are studied with two different divertor configurations with D-gas injection and nitrogen seeding. The power load reduction with N seeding is reported. The relationship between an increase in energy confinement and pedestal pressure with triangularity is investigated. The operational space of both plasma configurations is studied together with the ELM energy losses and stability of the pedestal of unseeded and seeded plasmas.

Journal Articles

An Approximate single fluid 3-dimensional magnetohydrodynamic equilibrium model with toroidal flow

Cooper, W. A.*; Hirshman, S. P.*; Chapman, I. T.*; Brunetti, D.*; Faustin, J. M.*; Graves, J. P.*; Pfefferl$'e$, D.*; Raghunathan, M.*; Sauter, O.*; Tran, T. M.*; et al.

Plasma Physics and Controlled Fusion, 56(9), p.094004_1 - 094004_8, 2014/09

 Times Cited Count:4 Percentile:24.41(Physics, Fluids & Plasmas)

An approximate model for a single fluid three-dimensional (3D) magnetohydrodynamic (MHD) equilibrium with pure isothermal toroidal flow with imposed nested magnetic flux surfaces is proposed. It recovers the rigorous toroidal rotation equilibrium description in the axisymmetric limit. The approximation is valid under conditions of nearly rigid or vanishing toroidal rotation in regions with significant 3D deformation of the equilibrium flux surfaces. Bifurcated helical core equilibrium simulations of long-lived modes in the MAST device demonstrate that the magnetic structure is only weakly affected by the flow but that the 3D pressure distortion is important. The pressure is displaced away from the major axis and therefore is not as noticeably helically deformed as the toroidal magnetic flux under the subsonic flow conditions measured in the experiment.

Journal Articles

The Effect of the electron temperature and current density profiles on the plasma current decay in JT-60U disruptions

Shibata, Yoshihide; Isayama, Akihiko; Miyamoto, Seiji*; Kawakami, Sho*; Watanabe, Kiyomasa*; Matsunaga, Go; Kawano, Yasunori; Lukash, V.*; Khayrutdinov, R.*; JT-60 Team

Plasma Physics and Controlled Fusion, 56(4), p.045008_1 - 045008_8, 2014/04

 Times Cited Count:2 Percentile:12.66(Physics, Fluids & Plasmas)

In JT-60U disruption, the plasma current decay during the initial phase of current quench has been calculated by a disruption simulation code (DINA) using the measured electron temperature $$T_{rm e}$$ profile. In the case of fast plasma current decay, $$T_{rm e}$$ has a peaked profile just after thermal quench and the $$T_{rm e}$$ profile doesn't change significantly during the initial phase of current quench. On the other hand, in the case of the slow plasma current decay, the $$T_{rm e}$$ profile is border just after the thermal quench, and the $$T_{rm e}$$ profile shrinks. The results of DINA simulation show that plasma internal inductance $$L_{rm i}$$ increases during the initial phase of current quench, while plasma external inductance $$L_{rm e}$$ does not change in time. The increase of $$L_{rm i}$$ is caused by current diffusion toward the core plasma due to the decrease of $$T_{rm e}$$ in intermediate and edge regions. It is suggested that an additional heating in the plasma periphery region has the effect of slowing down plasma current decay.

Journal Articles

On the Gyrokinetic model in long wavelength regime

Miyato, Naoaki; Scott, B. D.*; Yagi, Masatoshi

Plasma Physics and Controlled Fusion, 55(7), p.074011_1 - 074011_6, 2013/07

 Times Cited Count:6 Percentile:30.89(Physics, Fluids & Plasmas)

Journal Articles

Impact of plasma rotation on the linear physics of resistive wall modes in tokamaks

Aiba, Nobuyuki; Shiraishi, Junya; Hirota, Makoto

Plasma Physics and Controlled Fusion, 55(7), p.074002_1 - 074002_7, 2013/00

 Times Cited Count:6 Percentile:25.89(Physics, Fluids & Plasmas)

The authors identified that plasma poloidal rotation sometimes plays an important role for ideal MHD stability due to changing the Doppler-shift frequency. As the result, the stability of edge localized MHD mode can depends on the direction of toroidal rotation; this dependence is qualitatively consistent with the experimental results observed in JT-60U. Plasma rotation is also responsible for the stability of resistive wall mode (RWM). In reversed shear plasmas, plasma rotation once stabilize this RWM but destabilize this again when rotation frequency reaches to certain frequency. This re-destabilization is thought to be related to the coupling between RWM and a stable MHD wave; this coupling is one of the destabilizing mechanisms discussed in previous theoretical papers. This re-destabilized RWM can become unstable in the plasma whose beta value is below no-wall beta limit.

Journal Articles

Highly accurate approximate solutions of the stokes equation for high electron density and long laser-wavelength

Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori

Plasma Physics and Controlled Fusion, 54(5), p.055005_1 - 055005_7, 2012/05

 Times Cited Count:7 Percentile:34.01(Physics, Fluids & Plasmas)

Journal Articles

Extreme field science

Bulanov, S. V.; Esirkepov, T. Z.; Hayashi, Yukio; Kando, Masaki; Kiriyama, Hiromitsu; Koga, J. K.; Kondo, Kiminori; Kotaki, Hideyuki; Pirozhkov, A. S.; Bulanov, S. S.*; et al.

Plasma Physics and Controlled Fusion, 53(12), p.124025_1 - 124025_13, 2011/12

 Times Cited Count:5 Percentile:26.34(Physics, Fluids & Plasmas)

Journal Articles

Integrated modelling of a JET type-I ELMy H-mode pulse and predictions for ITER-like wall scenarios

Wiesen, S.*; Brezinsek, S.*; J$"a$rvinen, A.*; Eich, T.*; Fundamenski, W.*; Huber, A.*; Parail, V.*; Corrigan, G.*; Hayashi, Nobuhiko; JET-EFDA Contributors*

Plasma Physics and Controlled Fusion, 53(12), p.124039_1 - 124039_12, 2011/12

 Times Cited Count:22 Percentile:71.91(Physics, Fluids & Plasmas)

Journal Articles

Innovation on high-power long-pulse gyrotrons

Litak, A.*; Sakamoto, Keishi; Thumm, M.*

Plasma Physics and Controlled Fusion, 53(12), p.124002_1 - 124002_14, 2011/12

 Times Cited Count:27 Percentile:78.05(Physics, Fluids & Plasmas)

Journal Articles

Extreme field science

Bulanov, S. V.; Esirkepov, T. Z.; Hayashi, Yukio; Kando, Masaki; Kiriyama, Hiromitsu; Koga, J. K.; Kondo, Kiminori; Kotaki, Hideyuki; Pirozhkov, A. S.; Bulanov, S. S.*; et al.

Plasma Physics and Controlled Fusion, 53(12), p.124025_1 - 124025_13, 2011/11

Journal Articles

Linear response model of the vertical electromagnetic force on a vessel applicable to ITER and future tokamaks

Miyamoto, Seiji

Plasma Physics and Controlled Fusion, 53(8), p.082001_1 - 082001_7, 2011/08

 Times Cited Count:4 Percentile:21.61(Physics, Fluids & Plasmas)

Vertical displacement events (VDEs) and a subsequent plasma disruption cause severe electromagnetic force on the vacuum vessel of axisymmetric magnetic confinement fusion devices like tokamaks and spherical tokamaks. This force is a dominant factor for the supporting system of the vacuum vessel and in-vessel components and a lot of efforts have been devoted to predict the possible force in future machines such as ITER. The eddy and halo currents induced in the vessel accompanying VDE and current quench complicate the analysis of the electromagnetic force and usually, computer simulations are required to employ for the analysis. So far, a database of vertical force for ITER has been created based on DINA simulation. However, no theory has been developed for systematic explanation of the simulation data. The problem of calculating vertical electromagnetic force on the vessel is reformulated to a linear response problem. First, it is shown that a burdensome task of calculating in-vessel halo and eddy currents is reduced to the calculation of the source term of the vertical force, or a force exerted on the plasma by poloidal field (PF) coils. The calculation is carried out without relying on the knowledge of currents in the vessel. The vertical force then emerges as a result of linear response, or electromagnetic shielding by the vessel. The model provides an analytical way of calculating vertical force. As an example of application, dependence of vertical force on current quench rate is derived analytically. The obtained formula well reproduces the simulation result of DINA.

Journal Articles

Synthesized intensity of emission lines of hydrogen isotopes and impurities in the ITER divertor plasma

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kusama, Yoshinori

Plasma Physics and Controlled Fusion, 53(4), p.045005_1 - 045005_17, 2011/04

 Times Cited Count:2 Percentile:11.78(Physics, Fluids & Plasmas)

Journal Articles

Manipulation and electron-oscillation-measurement of laser accelerated electron beams

Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Koga, J. K.; Daido, Hiroyuki; Bulanov, S. V.

Plasma Physics and Controlled Fusion, 53(1), p.014009_1 - 014009_7, 2011/01

 Times Cited Count:5 Percentile:26.34(Physics, Fluids & Plasmas)

254 (Records 1-20 displayed on this page)