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Journal Articles

Frontier in fusion research, 2; Introduction to modern tokamak physics

Kikuchi, Mitsuru; Azumi, Masafumi*

Frontiers in Fusion Research, 2; Introduction to Modern Tokamak Physics, 402 Pages, 2015/09

This book is a textbook on modern tokamak plasma physics for graduate students and researchers based on our Reviews of Modern Physics (2012).

Journal Articles

Steady-state tokamak research; Core physics

Kikuchi, Mitsuru; Azumi, Masafumi*

Reviews of Modern Physics, 84(4), p.1807 - 1854, 2012/12

 Times Cited Count:45 Percentile:87.5(Physics, Multidisciplinary)

Tokamak uses transformer action for plasma confinement. So, it is proposed to use non-inductive current drive including bootstrap current to achieve steady state operation. This paper reviews the progress of steady state tokamak research focused on theoretical aspect for 20 years since my proposal in 1990.

Journal Articles

Collisionality dependence of a shielding factor of a beam driven current

Honda, Mitsuru; Kikuchi, Mitsuru; Azumi, Masafumi*

Nuclear Fusion, 52(2), p.023021_1 - 023021_12, 2012/02

 Times Cited Count:20 Percentile:66.66(Physics, Fluids & Plasmas)

Journal Articles

Simulation studies on alpha-particle-driven current in tokamak reactors

Tani, Keiji; Azumi, Masafumi*

Nuclear Fusion, 48(8), p.085001_1 - 085001_9, 2008/08

 Times Cited Count:13 Percentile:49.86(Physics, Fluids & Plasmas)

Simulation studies are made for alpha-driven currents in tokamak reactors by using an orbit-following Monte-Carlo code. The finite banana width of alpha particles causes an asymmetry particle trapping and consequently an alpha current is driven by the imbalance of transit particles. The current driven by alpha transit particles (simply referred to as transit current) is greatly enhanced by a collaborative effect of the finite banana-width trajectories and a non-uniformity of alpha particle source. The pitch-angle scattering is also very important for the transit current. Fusion produced alpha particles can drive substantial current to assist the bulk bootstrap current in steady state tokamak reactors.

Journal Articles

Nonlinear evolution and deformation of driven magnetic islands in rotating plasmas

Ishii, Yasutomo; Azumi, Masafumi; Smolyakov, A. I.*

Nuclear Fusion, 47(8), p.1024 - 1032, 2007/08

 Times Cited Count:9 Percentile:34.53(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Explosive growth and nonlinear dynamics of the forced magnetic island

Ishii, Yasutomo; Azumi, Masafumi; Smolyakov, A. I.*

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

no abstracts in English

Journal Articles

Magnetic island evolution in rotating plasmas

Ishii, Yasutomo; Azumi, Masafumi*; Smolyakov, A. I.*

Journal of Plasma Physics, 72(6), p.1243 - 1248, 2006/12

 Times Cited Count:1 Percentile:3.81(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

A Model for striation formation in ac PDP discharges

Muraoka, Katsunori*; Azumi, Masafumi; Suzuki, Keizo*; Yamagata, Yukihiko*; Yagi, Masatoshi*

Journal of Physics D; Applied Physics, 39(10), p.2135 - 2139, 2006/05

 Times Cited Count:5 Percentile:21.93(Physics, Applied)

A model is presented to explain the mechanism of striation formation in ac plasma display panel discharges. A simple Monte Carlo simulation code follows the electron motions in such discharges and features of striations obtained by the simulation are consistent with experimental results. The model suggests the indirect measurement of electric field in a micro-discharges from the space pich of striations.

Journal Articles

Critical $$beta$$ analyses with ferromagnetic and plasma rotation effects and wall geometry for a high $$beta$$ steady state tokamak

Kurita, Genichi; Bialek, J.*; Tsuda, Takashi; Azumi, Masafumi*; Ishida, Shinichi; Navratil, G. A.*; Sakurai, Shinji; Tamai, Hiroshi; Matsukawa, Makoto; Ozeki, Takahisa; et al.

Nuclear Fusion, 46(2), p.383 - 390, 2006/02

 Times Cited Count:9 Percentile:33.28(Physics, Fluids & Plasmas)

It is shown that critical beta is decreased by ferromagnetic effect by about 8% for $$mu$$/$$mu$$$$_{0}$$$$sim$$2, $$mu$$ and $$mu$$$$_{0}$$ denoting the permeability of ferromagnetic wall and vacuum, respectively, for tokamak of aspect ratio 3. The existence of the stability window for resistive wall mode opened by both effects of the toroidal plasma rotation and the plasma dissipation, which was not observed for high aspect ratio tokamak, is found for tokamak of aspect ratio 3. The effect of ferromagnetism on them is also investigated. The critical beta analyses of NCT (National Centralized Tokamak) plasma using VALEN code are started with stabilizing plate and vacuum vessel geometry with finite resistivity, and the results for passive effect of stabilizing plate are obtained. The calculations including stabilizing effect of the vacuum-vessel and also active feedback control are also performed for present design of NCT plasma.

Journal Articles

Critical $$beta$$ analyses with ferromagnetic and plasma rotation effects and wall geometry for a high $$beta$$ steady state tokamak

Kurita, Genichi; Bialek, J.*; Tsuda, Takashi; Azumi, Masafumi; Ishida, Shinichi; Navratil, G. A.*; Sakurai, Shinji; Tamai, Hiroshi; Matsukawa, Makoto; Ozeki, Takahisa; et al.

IAEA-CN-116/FT/P7-7 (CD-ROM), 8 Pages, 2004/11

The critical beta is shown to be decreased by ferromagnetic effect by about 8 % for m/m0$$sim$$2, m and m0 denote the permeability of ferromagnetic wall and vacuum, respectively, for tokamak of aspect ratio 3. The existence of the stability window opened by both effects of the toroidal plasma rotation and the plasma dissipation, which was not observed for high aspect ratio tokamak, is found for tokamak of aspect ratio 3. The effect of ferromagnetism on them is also investigated. The critical beta analyses of NCT (National Centralized Tokamak) plasma using VALEN code are started with stabilizing plate and vacuum vessel geometry with finite resistivity, and the results for passive effect of stabilizing plate are obtained. The calculations including stabilizing effect of the vacuum-vessel and also active feedback control are also performed for present design of NCT plasma.

Journal Articles

In the case of Japan Atomic Energy Research Institute

Azumi, Masafumi

Purazuma, Kaku Yugo Gakkai-Shi, 80(5), p.378 - 381, 2004/05

Progress of large scale scientific simulation environment in JAERI is briefly described. The expansion of fusion simulation science have been played a key role in the increasing performances of super computers and computer network system in JAERI. Both scalar parallel and vector parallel computer systems are now working in Naka and Tokai sites respectively and, particle and fluid simulation codes developed under the fusion simulation project, NEXT, are running on each system. The storage grid system has been also successfully developed for the effective visualization analysis by remote users. Fusion research is going to enter the new phase of ITER, and the need for the super computer system with higher performance are increasing more than as ever along with the development of reliable simulation models.

Journal Articles

Nonlinear destabilization and explosive growth of double tearing modes

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki

Theory of Fusion Plasmas, ISPP21, p.213 - 226, 2004/00

no abstracts in English

Journal Articles

Ferromagnetic and resistive wall effects on the beta limit in a Tokamak

Kurita, Genichi; Tsuda, Takashi; Azumi, Masafumi; Ishida, Shinichi; Takeji, Satoru*; Sakasai, Akira; Matsukawa, Makoto; Ozeki, Takahisa; Kikuchi, Mitsuru

Nuclear Fusion, 43(9), p.949 - 954, 2003/09

 Times Cited Count:28 Percentile:66.45(Physics, Fluids & Plasmas)

In order to improve economic and environmental suitability of tokamak fusion reactors, both the accomplishment of high beta plasmas and the practical use of low activation materials to reduce the amount of radioactive waste are crucially important. Low radio-activation ferritic steel is considered as a most promising candidate for structural material in DEMO reactors, and there is the possibility of reduction of critical beta value by the deterioration of MHD stability due to ferromagnetism of ferritic steel. This paper investigates the effect of ferromagnetism with plasma flow on the beta limit of tokamak plasma by carrying out MHD stability analyses including ferromagnetic and plasma flow effects.

Journal Articles

Current point formation and magnetic reconnection process in nonlinearly destabilized double tearing modes

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki

Physics of Plasmas, 10(9), p.3512 - 3520, 2003/09

 Times Cited Count:8 Percentile:27.21(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Effect of a ferromagnetic wall on low $$beta$$ tearing modes in the Japan atomic research institute fusion Torus-2 modified

Bakhtiari, M.; Azumi, Masafumi; Tsuzuki, Kazuhiro; Kamiya, Kensaku; Kawashima, Hisato; Kusama, Yoshinori; Sato, Masayasu; Hoshino, Katsumichi; JFT-2M Group

Physics of Plasmas, 10(8), p.3212 - 3216, 2003/08

 Times Cited Count:13 Percentile:41.38(Physics, Fluids & Plasmas)

The Tearing mode equation is solved in presence of a ferromagnetic resistive wall to study the effect of the ferromagnetism on the Tearing mode stability. It is shown that a ferromagnetic wall has a weak effect on the surface Tearing modes depending on the curent profile.

Journal Articles

Long timescale plasma dynamics and explosive growth driven by the double tearing mode in reversed shear plasmas

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*

Nuclear Fusion, 43(7), p.539 - 546, 2003/07

no abstracts in English

Journal Articles

Long timescale plasma dynamics and explosive growth driven by the double tearing mode in reversed shear plasmas

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*

Nuclear Fusion, 43(7), p.539 - 546, 2003/07

 Times Cited Count:21 Percentile:56.61(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Structure-driven nonlinear instability of double tearing modes and the abrupt growth after long-time-scale evolution

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki

Physical Review Letters, 89(20), p.205002_1 - 205002_4, 2002/11

 Times Cited Count:85 Percentile:91.39(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Lecture "Let's study MHD" chapter 2 "MHD Model"

Azumi, Masafumi

Purazuma, Kaku Yugo Gakkai-Shi, 77(5), p.457 - 463, 2001/05

no abstracts in English

Journal Articles

Nonlinear destabilization of double tearing modes in reverced magnetic shear plasmas

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki

Journal of Plasma and Fusion Research SERIES, Vol.4, p.271 - 275, 2001/00

no abstracts in English

133 (Records 1-20 displayed on this page)