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Journal Articles

Challenges of ab initio simulations to physics of burning plasma confinement

Watanabe, Tomohiko*; Idomura, Yasuhiro; Todo, Yasushi*; Honda, Mitsuru*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(3), p.152 - 156, 2022/03

Understanding of physical processes of particle, momentum, and thermal transports is essential for predicting the confinement performance of burning plasmas in ITER, which is targeting the scientific demonstration of magnetic confinement fusion. First principles based simulations on Fugaku disclosed physical mechanisms such as complex transport processes of multi-scale turbulence in deuterium-tritium plasmas and kinetic effects in energetic particle transport due to electromagnetic fluctuations. We promote further research and development of first principles based simulations towards the performance prediction of burning plasmas.

Journal Articles

Dynamics of enhanced neoclassical particle transport of tracer impurity ions in ion temperature gradient driven turbulence

Idomura, Yasuhiro; Obrejan, K.*; Asahi, Yuichi; Honda, Mitsuru*

Physics of Plasmas, 28(1), p.012501_1 - 012501_11, 2021/01

 Times Cited Count:3 Percentile:55.67(Physics, Fluids & Plasmas)

Tracer impurity transport in ion temperature gradient driven (ITG) turbulence is investigated using a global full-$$f$$ gyrokinetic simulation including kinetic electrons, bulk ions, and low to medium $$Z$$ tracer impurities, where $$Z$$ is the charge number. It is found that in addition to turbulent particle transport, enhanced neoclassical particle transport due to a new synergy effect between turbulent and neoclassical transports makes a significant contribution to tracer impurity transport. Bursty excitation of the ITG mode generates non-ambipolar turbulent particle fluxes of electrons and bulk ions, leading to a fast growth of the radial electric field following the ambipolar condition. The divergence of $$Etimes B$$ flows compresses up-down asymmetric density perturbations, which are subject to transport induced by the magnetic drift. The enhanced neoclassical particle transport depends on the ion mass, because the magnitude of up-down asymmetric density perturbation is determined by a competition between the $$Etimes B$$ compression effect and the return current given by the parallel streaming motion. This mechanism does not work for the temperature, and thus, selectively enhances only particle transport.

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:15.29(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

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

 Times Cited Count:14 Percentile:61.44(Physics, Fluids & Plasmas)

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 ($$T_{rm i}$$-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 ($$T_{rm e}$$/$$T_{rm i}$$) and ECH power. The electron heat diffusivity around a $$T_{rm e}$$-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.

Journal Articles

Integrated modelling of toroidal rotation with the 3D non-local drift-kinetic code and boundary models for JT-60U analyses and predictive simulations

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Yoshida, Maiko; Hayashi, Nobuhiko; Kamiya, Kensaku; Matsuyama, Akinobu; Shinohara, Koji; Matsunaga, Go; Nakata, Motoki; et al.

Nuclear Fusion, 55(7), p.073033_1 - 073033_11, 2015/07

 Times Cited Count:5 Percentile:25.88(Physics, Fluids & Plasmas)

Journal Articles

Advance in integrated modelling towards prediction and control of JT-60SA plasmas

Hayashi, Nobuhiko; Honda, Mitsuru; Shiraishi, Junya; Miyata, Yoshiaki; Wakatsuki, Takuma; Hoshino, Kazuo; Toma, Mitsunori; Suzuki, Takahiro; Urano, Hajime; Shimizu, Katsuhiro; et al.

Europhysics Conference Abstracts (Internet), 39E, p.P5.145_1 - P5.145_4, 2015/06

Journal Articles

Effects of the radial electric field on the confinement of fast ions in ITER

Tani, Keiji*; Honda, Mitsuru; Oikawa, Toshihiro*; Shinohara, Koji; Kusama, Yoshinori; Sugie, Tatsuo

Nuclear Fusion, 55(5), p.053010_1 - 053010_15, 2015/05


 Times Cited Count:2 Percentile:9.8(Physics, Fluids & Plasmas)

The effects of a radial electric field (EF) on the losses of alpha particles and NBI fast ions in typical ITER operation scenarios for both error fields due to test blanket modules (TBMs) and toroidal field (TF) ripple were evaluated using an iterative method to execute an orbit-following Monte-Carlo code and a one-dimensional transport code. The EF effect on the loss of fast ions strongly depends on the operation scenario as well as on the error field. The electric field is very significant in the loss of fast ions in a 9MA ITER operation scenario with a higher safety factor and in the error field associated with TBMs. The EF effect in the error field of TF-ripple is very small in any operation scenario. The radial electric field changes the toroidal precession of fast ions and consequently alter their condition of resonance with the error field, which may account for the EF effect on the loss of fast ions in ITER with TBMs.

Journal Articles

Roles of argon seeding in energy confinement and pedestal structure in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Hayashi, Nobuhiko; Yoshida, Maiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 55(3), p.033010_1 - 033010_9, 2015/03

 Times Cited Count:34 Percentile:87.13(Physics, Fluids & Plasmas)

Physics picture of improving energy confinement with argon seeding at high density has been investigated in JT-60U. Better confinement is sustained at high density by argon seeding accompanied by higher core and pedestal temperatures. Peaked density profiles are kept with argon seeding. Density peaking and dilution effects lower the pedestal density at a given averaged density. The pedestal density in the argon seeded plasmas which is relatively lower than that in a single deuterium puff enables the pedestal temperature to be higher. The density peaking is a key factor of sustaining better confinement in argon seeded H-mode plasmas.

Journal Articles

Gyrokinetic analyses of core heat transport in JT-60U plasmas with different toroidal rotation direction

Narita, Emi*; Honda, Mitsuru; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke; Fukuda, Takeshi*

Plasma and Fusion Research (Internet), 10, p.1403019_1 - 1403019_11, 2015/03

Journal Articles

Boundary condition for toroidal plasma flow imposed at the separatrix in high confinement JT-60U plasmas with edge localized modes and the physics process in pedestal structure formation

Kamiya, Kensaku; Honda, Mitsuru; Urano, Hajime; Yoshida, Maiko; Kamada, Yutaka; Ito, Kimitaka*; JT-60 Team

Physics of Plasmas, 21(12), p.122517_1 - 122517_8, 2014/12

 Times Cited Count:13 Percentile:57.12(Physics, Fluids & Plasmas)

Modulation Charge eXchange Recombination Spectroscopy (MCXRS) measurements with high spatial and temporal resolution have made the evaluation of the toroidal plasma flow of fully stripped carbon impurity ions in the JT-60U tokamak peripheral region (including in particular separatrix) possible with a better signal-to-noise ratio. Boundary condition of Vt imposed at the separatrix in ELMy H-mode plasmas has been identified, comparing between co- and counter-NBI discharges. The Vt value at the separatrix is not held fixed at the zero, varying with momentum input direction, but being not strongly affected by the ELM event. A non-zero Vt value at the separatrix might be connected to fast ion losses due to toroidal field ripple that results in formation of a negative radial electric field (Er) layer having almost zero (or very weak positive) Er-shear value at the separatrix. Improved understanding of physics process in pedestal structure formation for the Vt and Er is also discussed.

Journal Articles

Experimental analyses and predictive simulations of toroidal rotation driven by the neoclassical toroidal viscosity in rippled tokamaks

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Matsunaga, Go; Shinohara, Koji; Yoshida, Maiko; Matsuyama, Akinobu; Ide, Shunsuke; Urano, Hajime

Nuclear Fusion, 54(11), p.114005_1 - 114005_14, 2014/11

 Times Cited Count:14 Percentile:59.62(Physics, Fluids & Plasmas)

Journal Articles

Integrated modeling of toroidal rotation with the 3D non-local drift-kinetic code and boundary models for JT-60U analyses and predictive simulations

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Yoshida, Maiko; Hayashi, Nobuhiko; Kamiya, Kensaku; Matsuyama, Akinobu; Shinohara, Koji; Matsunaga, Go; Nakata, Motoki; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Extension of kinetic-magnetohydrodynamic model to include toroidal rotation shear effect and its application to stability analysis of resistive wall modes

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go; Honda, Mitsuru; Hayashi, Nobuhiko; Ide, Shunsuke

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Extension of the kinetic-magnetohydrodynamic (MHD) model is presented to include toroidal rotation shear effect for the first time. The sheared rotation is introduced through generalization of the guiding center Lagrangian, yielding two additional terms in a quadratic form of mode-particle resonance. Additionally, another new term is introduced by using the equilibrium distribution function with rotation effect. These three terms are overlooked in conventional models. The new model is applied to stability analysis of resistive wall modes (RWMs) successfully. Numerical results show that the rotation shear reduces RWM growth rates further, which is consistent with experimental results.

Journal Articles

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

 Times Cited Count:35 Percentile:87.29(Physics, Fluids & Plasmas)

Journal Articles

Impact of higher-order flows in the moment equations on Pfirsch-Schl$"u$ter friction coefficients

Honda, Mitsuru

Physics of Plasmas, 21(9), p.092508_1 - 092508_10, 2014/09

 Times Cited Count:17 Percentile:64.53(Physics, Fluids & Plasmas)

Journal Articles

Edge radial electric field formation after the L-H transition on JT-60U

Kamiya, Kensaku; Matsunaga, Go; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Kamada, Yutaka; Ida, Katsumi*; Ito, Kimitaka*; JT-60 Team

Contributions to Plasma Physics, 54(4-6), p.591 - 598, 2014/06

 Times Cited Count:6 Percentile:31.83(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Role of seed impurity for H-mode plasmas in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Yoshida, Maiko; Hayashi, Nobuhiko; Kamada, Yutaka; JT-60 Team

Europhysics Conference Abstracts (Internet), 38F, p.P4.018_1 - P4.018_4, 2014/06

This paper reports the analysis result of heat transport and pedestal structure in H-mode plasmas with and without argon seeding on JT-60U.

Journal Articles

Report on ITPA meetings, 45

Hayashi, Nobuhiko; Aiba, Nobuyuki; Isayama, Akihiko; Shinohara, Koji; Honda, Mitsuru

Purazuma, Kaku Yugo Gakkai-Shi, 90(6), p.352 - 355, 2014/06

no abstracts in English

Journal Articles

Coulomb logarithm formulae for collisions between species with different temperatures

Honda, Mitsuru

Japanese Journal of Applied Physics, 52(10), p.108002_1 - 108002_3, 2013/10

 Times Cited Count:8 Percentile:36.22(Physics, Applied)

Journal Articles

Simulations of toroidal rotation driven by the neoclassical toroidal viscosity in tokamaks

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Matsunaga, Go; Ide, Shunsuke; Yoshida, Maiko; Hayashi, Nobuhiko

Europhysics Conference Abstracts (Internet), 37D, p.P1.182_1 - P1.182_4, 2013/07

174 (Records 1-20 displayed on this page)