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論文

国際核融合エネルギー研究センターの高性能計算機システムHeliosを利用した国内シミュレーション研究プロジェクトの進展

石澤 明宏*; 井戸村 泰宏; 今寺 賢志*; 糟谷 直宏*; 菅野 龍太郎*; 佐竹 真介*; 龍野 智哉*; 仲田 資季*; 沼波 政倫*; 前山 伸也*; et al.

プラズマ・核融合学会誌, 92(3), p.157 - 210, 2016/03

幅広いアプローチ協定に基づいて国際核融合エネルギー研究センター(IFERC)の計算機シミュレーションセンター(CSC)に設置された高性能計算機システムHeliosは、2012年1月に運用を開始し、日欧の磁気核融合シミュレーション研究に供用され、高い利用率の実績を示すとともに、炉心プラズマ物理から炉材料・炉工学にわたる広い分野で多くの研究成果に貢献している。本プロジェクトレビューの目的は、国内の大学や研究機関においてHeliosを利用して進められているシミュレーション研究プロジェクトとその成果を一望するとともに、今後予想される研究の進展を紹介することである。はじめにIFERC-CSCの概要を示した後、各研究プロジェクト毎にその目的、用いられる計算手法、これまでの研究成果、そして今後必要とされる計算を紹介する。

論文

Fokker-Planck simulation of runaway electron generation in tokamak disruptions

奴賀 秀男; 松山 顕之; 矢木 雅敏; 福山 淳*

Plasma and Fusion Research (Internet), 10, p.1203006_1 - 1203006_2, 2015/01

The runaway electron generation during tokamak disruptions is investigated by kinetic simulations. Three dimensional Fokker-Planck simulations (2D in momentum space and 1D in radial direction) are carried out with various values of $$tau_q$$ and the results are compared with the previous simulation results that use runaway generation rate derived by Conner and Hastie. From the simulation results, It is pointed out that the importance of the hot-tail effect for the description of the runaway electron generation mechanism with fast thermal quench.

論文

Simple and fast Poisson solver with arbitrary boundary shape and condition for PIC simulation

滝塚 知典*; 東 修平*; 福山 淳*; 清水 勝宏

Contributions to Plasma Physics, 54(4-6), p.388 - 393, 2014/06

 パーセンタイル:100(Physics, Fluids & Plasmas)

Particle-in-cell(PIC)粒子シミュレーションは核融合装置における境界プラズマの物理を理解するための強力な手法である。長方形容器中の直交格子を扱うPoissonソルバーは非常に高速であるが、複雑なダイバータ配位のシミュレーションには簡単には適用できない。この論文では、PICシミュレーションのための任意境界形状と条件を取り扱える単純で高速のPoissonソルバーを提案する。このソルバーでは境界点が重要であり、その点上で電荷密度が適切に与えられ、境界条件が満たされる。開放系の粒子シミュレーションでは、時間ステップ内に粒子が自由に運動しているか境界壁に当たるかを識別する必要がある。PICシミュレーションで粒子位置が境界を越えたかどうかを判別する新手法も提案する。

論文

Model validation and integrated modelling simulations for the JT-60SA tokamak

Giruzzi, G.*; Garcia, J.*; 林 伸彦; Schneider, M.*; Artaud, J. F.*; Baruzzo, M.*; Bolzonella, T.*; Farina, D.*; Figini, L.*; 藤田 隆明; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

A coordinated Japan-EU modelling activity has started in order to provide predictive simulations of the main JT-60SA scenarios. The first results of this activity are discussed in this paper. This includes: (1) the critical comparison and benchmark of Japanese and EU H and CD codes, in particular of NBI codes for the complex injector configuration of the JT-60SA machine; (2) the validation of the main models and simulation framework used in both Japanese and EU integrated modelling suites of codes, based on selected reference discharges of JT-60U and JET, representing the main scenarios (H-mode, hybrid, advanced); (3) predictive modelling of JT-60SA scenario, using the 0.5-D code METIS.

論文

Study of plasma meniscus formation and beam halo in negative hydrogen ion sources

奥田 晋*; 宮本 賢治*; 福山 俊茂*; 西岡 宗*; 畑山 明聖*; 深野 あづさ*; 花田 磨砂也; 小島 有志

AIP Conference Proceedings 1515, p.107 - 113, 2013/02

 被引用回数:9 パーセンタイル:2.35

負イオン源中のプラズマ-ビーム境界であるメニスカスは、負イオンビーム光学に大きく影響することは明らかである。近年、メニスカスの形状によるビームハロが発生することが示唆されている。これは、曲率の大きい負イオン放出面によるものと考えられている。そこで、このプラズマメニスカスの形状とビームハロに対する負イオン生成率の関係をPICコードを用いて調べた。その結果、プラズマメニスカスは負イオンの量で形が決まるため、ビームハロ形成は表面生成された負イオンの量に強く依存することが分かった。

論文

理論モデルとシミュレーションコード

林 伸彦; 福山 淳*

プラズマ・核融合学会誌, 88(11), p.678 - 680, 2012/11

ITERと原型炉におけるプラズマの予測・制御や運転シナリオの設計を目指した理論モデルとシミュレーションコードの検証は、JT-60SA計画の主要な目的の1つである。同時に、検証の対象となるJT-60SA実験を準備するためにも、既存のコードによるモデリングや新しいコードの開発、効率的なデータ交換のプラットフォームの開発等が必要となる。これらの活動は、日本だけでなく既に開始されている日欧協力も交えて行われ、日欧のブロードアプローチ計画に基づいて設置された高性能計算機を活用する。

論文

Simulation study of L/H transition with self-consistent integrated modelling of core and SOL/divertor transport

矢木 雅敏; 清水 勝宏; 滝塚 知典; 本多 充; 林 伸彦; 星野 一生; 福山 淳*

Contributions to Plasma Physics, 52(5-6), p.372 - 378, 2012/06

 被引用回数:4 パーセンタイル:74.44(Physics, Fluids & Plasmas)

We have developed a self-consistent integrated modelling of core and SOL/divertor transport. Thereby it enables us to investigate operation scenarios to be compatible with high confinement core plasma and detached divertor plasmas. A 1.5D core code TOPICS-IB and a 2D divertor code SONIC were coupled successively with a Multiple Program Multiple Data parallel computing system. For an integrated code including Monte-Carlo calculations, this system makes it possible to perform efficient simulations. The dynamic simulation for the L/H transition in JT-60SA is carried out by this integrated code with a CDBM transport model including the E$$times$$B shearing effect. Impacts of SOL/divertor transport on the L/H transition is studied.

論文

Multi-fluid transport equations on the flux coordinates in tokamaks

本多 充; 福山 淳*; 中島 徳嘉*

Europhysics Conference Abstracts (Internet), 36F, p.P5.014_1 - P5.014_4, 2012/00

The one-dimensional multi-fluid transport code TASK/TX is used to investigate the physics regarding rotation, radial current and the radial electric field. Unlike conventional diffusive transport codes, its equation system is more fundamental in that the code directly solves the momentum equations for all species plus Maxwell's equations. The main drawback to the code is that the basis equations are built on the cylindrical coordinates. Neoclassical effects have already been incorporated and its validity has been confirmed, but any geometrical effects have not entered yet. In this study, we derive the equations on the axisymmetric flux coordinates in a manner consistent with the current TASK/TX concept. The equations are projected onto the radial, poloidal ant toroidal directions in the current framework. In the flux coordinates, however, we have to project the equations of motion onto the radial, parallel and toroidal direction because of the neoclassical nature of a toroidal plasma.

論文

On the neoclassical relationship between the radial electric field and radial current in tokamak plasmas

本多 充; 福山 淳*; 中島 徳嘉*

Journal of the Physical Society of Japan, 80(11), p.114502_1 - 114502_14, 2011/11

 被引用回数:3 パーセンタイル:66.9(Physics, Multidisciplinary)

The equation is analytically derived, stipulating the relationship between the radial electric field $$E_r$$ and radial current $$j_r$$ in tokamak plasmas, especially when heated by neutral beam injection. On a very short time scale compared to the decay in poloidal rotation, the polarization current $$j_mathrm{p}$$ compensates for the non-ambipolar fast-ion radial current, $$j_r^mathrm{fast}$$, producing a concomitant time change in $$E_r$$. This $$j_mathrm{p}$$ predominates among the constituents of $$j_r$$ that produces the $$vec{j}timesvec{B}$$ torque. On a longer time scale, $$E_r$$ should be estimated through a force balance equation. In a steady state, transport of toroidal momentum plays a dominant role in balancing the torque induced by $$j_r^mathrm{fast}$$. Analytical work demonstrates that the basis equations of the one-dimensional transport code TASK/TX essentially have the capability to reproduce the phenomena derived, which is subsequently confirmed by numerical simulation.

論文

Current ramps in tokamaks; From present experiments to ITER scenarios

Imbeaux, F.*; Citrin, J.*; Hobirk, J.*; Hogeweij, G. M. D.*; K$"o$chl, F.*; Leonov, V. M.*; 宮本 斉児; 中村 幸治*; Parail, V.*; Pereverzev, G. V.*; et al.

Nuclear Fusion, 51(8), p.083026_1 - 083026_11, 2011/08

 被引用回数:30 パーセンタイル:14.1(Physics, Fluids & Plasmas)

In order to prepare adequate current ramp-up and ramp-down scenarios for ITER, present experiments from various tokamaks have been analysed by means of integrated modelling in view of determining relevant heat transport models for these operation phases. A set of empirical heat transport models for L-mode has been validated on a multi-machine experimental dataset for predicting the $$l_i$$ dynamics within $$pm$$0.15 accuracy during current ramp-up and ramp-down phases. The most accurate heat transport models are then applied to projections to ITER current ramp-up, focusing on the baseline inductive scenario (main heating plateau current of $$I_p = 15$$ MA). These projections include a sensitivity study to various assumptions of the simulation. While the heat transport model is at the heart of such simulations, more comprehensive simulations are required to test all operational aspects of the current ramp-up and ramp-down phases of ITER scenarios. Recent examples of such simulations, involving coupled core transport codes, free-boundary equilibrium solvers and a poloidal field (PF) systems controller are also described, focusing on ITER current ramp-down.

論文

Integrated modeling of whole tokamak plasma

林 伸彦; 本多 充; 星野 一生; 濱松 清隆; 清水 勝宏; 滝塚 知典; 小関 隆久; 福山 淳*

Plasma and Fusion Research (Internet), 6(Sp.1), p.2403065_1 - 2403065_8, 2011/08

Development and integration of models for the whole tokamak plasma have progressed on the basis of experimental analyses and first principle simulations. Integrated models of core, edge-pedestal and scrape-off-layer (SOL)-divertor clarified complex and autonomous features of reactor relevant plasmas. The integrated core plasma model including an anomalous transport of alpha particles by Alfv$'e$n eigenmodes is developed in the core transport code TOPICS-IB and indicates the degradation of fusion performance. The integrated rotation model is developed in the advanced transport code TASK/TX and clarifies the mechanism of alpha particle-driven toroidal flow. The transport model of high-Z impurities is developed and predicts large inward pinch in a plasma rotating in the direction counter to the plasma current. TOPICS-IB is extended to include the edge-pedestal model by integrating with the stability code, simple SOL-divertor and pellet models, and clarifies the mechanism of pellet triggered ELM. The integrated SOL-divertor code SONIC is further integrated with TOPICS-IB and enables to study and design operation scenarios compatible with both the high confinement in the core and the low heat load on divertor plates.

論文

Alpha particle-driven toroidal rotation in burning plasmas

本多 充; 滝塚 知典; 飛田 健次; 松永 剛; 福山 淳*

Nuclear Fusion, 51(7), p.073018_1 - 073018_9, 2011/07

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are investigated. In DEMO plasmas, OFMC predicts that co-collisional torque and a counter $$vec{j}timesvec{B}$$ torque always emerge regardless of the magnetic configuration, and both of them virtually cancel each other out. The gradient of the source profile of alpha particles produces both torques, and the magnitude of each torque is enhanced in the reversed shear configuration compared to the normal shear configuration, provided that the source gradient is finite and similar in both cases. The resultant rotation velocity estimated by TASK/TX is far below the threshold to stabilize resistive wall modes through intrinsic alpha-driven torque alone. It is estimated that neutral beam injection at a moderate power level may be necessary for obtaining toroidal rotation sufficient to stabilize resistive wall modes.

論文

Alpha particle-driven toroidal rotation in burning plasmas

本多 充; 滝塚 知典; 飛田 健次; 松永 剛; 福山 淳*

Nuclear Fusion, 51(7), p.073018_1 - 073018_9, 2011/07

 被引用回数:15 パーセンタイル:32.91(Physics, Fluids & Plasmas)

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are investigated. In DEMO, an orbit-following Monte Carlo code OFMC predicts that the magnitude of both collisional and a $$vec{j}timesvec{B}$$ torques increases in a reversed shear configuration compared to that in a normal shear case. The gradient of the source profile of alpha particles produces the co-directed collisional torque and a counter-directed $$vec{j}timesvec{B}$$ torque, and both torques virtually cancel each other out over the entire domain. Eventually, the toroidal rotation velocity solely driven by alpha particles is not sufficient to stabilize resistive wall modes (RWMs), but neutral beam injection will be capable of exceeding the threshold of RWM stabilization, if it is used.

論文

Neoclassical transport modeling compatible with a two-fluid transport equation system

本多 充; 福山 淳*; 中島 徳嘉*

Plasma and Fusion Research (Internet), 6, p.1403008_1 - 1403008_11, 2011/05

二流体方程式系に適合した新古典輸送モデルを提案する。このモデルはモーメント法に基づいており、NCLASSモジュールを用いることで、比較的簡単な新古典粘性テンソル表記を通して重要な新古典特性を正確に再現することができる。流体描像の新古典輸送理論を適用することで、1次の流れ、ポロイダル流、新古典抵抗、ブートストラップ電流、粒子束について、TASK/TXの結果とNCLASSの出力結果が良い一致を示すことがわかった。

論文

Self-consistent integrated modelling of core and SOL/divertor transports and simulation study on transient behavior of heat load on divertor targets

清水 勝宏; 滝塚 知典; 星野 一生; 本多 充; 林 伸彦; 高山 有道*; 福山 淳*; 矢木 雅敏*

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 6 Pages, 2011/03

コア輸送とスクレイプオフ層/ダイバータでの輸送の統合モデリングを開発した。これによって、高閉じ込めコアプラズマと非接触プラズマが両立する放電シナリオについて研究することが可能となった。1.5次元コア輸送コード(TOPICS-IBとTASK)と2次元ダイバータコード(SONIC)を統合化するため、新しいMPMD並列計算システムを導入した。モンテカルロ計算を含んだ統合コードに対して、本システムは効率的なシミュレーションの実行が可能である。この統合コード(TOPICS-IB/SONIC)を用いたシミュレーション解析により、JT-60SA装置のHモード遷移に伴うダイバータの熱負荷特性を明らかにした。ELM崩壊後のダイバータ特性の過渡的挙動についても調べた。

論文

Integrated modeling of steady-state scenarios and heating and current drive mixes for ITER

村上 和功*; Park, J. M.*; Giruzzi, G.*; Garcia, J.*; Bonoli, P.*; Budny, R. V.*; Doyle, E. J.*; 福山 淳*; 林 伸彦; 本多 充; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Recent progress on ITER steady-state scenario modeling by the ITPA-IOS group is reviewed. Code-to-code benchmarks as the IOS group's common activities for the two steady-state scenarios (weak shear scenario and internal transport barrier scenario) are reviewed. These are discussed in terms of transport and kinetic profiles, heating and CD sources using various transport codes.

論文

Alpha particle-driven toroidal rotation in burning plasmas

本多 充; 滝塚 知典; 飛田 健次; 松永 剛; 福山 淳*; 小関 隆久

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are investigated. In DEMO plasmas, an orbit-following Monte Carlo code OFMC predicts that the profile of a collisional torque is influenced near the magnetic axis by a reversed magnetic shear configuration, while that of a $$vec{j}timesvec{B}$$ torque is not. It is found that the gradient of the source profile of alpha particles produces the co-directed collisional torque and a counter-directed $$vec{j}timesvec{B}$$ torque, and both torques virtually cancel each other out in the central region of the plasma. A non-negligible torque shear and resulting toroidal rotation in the co-direction are obtained in a weakly reversed-shear configuration, but the estimated rotation velocity is below the threshold to stabilize resistive-wall modes through intrinsic alpha-driven torque alone.

論文

Integrated transport simulation of LHD plasmas using TASK3D

若狭 有光*; 福山 淳*; 村上 定義*; 三木 真幸*; 横山 雅之*; 佐藤 雅彦*; 登田 慎一郎*; 舟場 久芳*; 田中 謙治*; 居田 克巳*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

An integrated transport simulation code for helical plasmas, TASK3D, is developed and applied to LHD plasmas. Neoclassical transport in helical plasmas is evaluated by the neutral-network-based neoclassical transport database, DGN/LHD. Five anomalous transport models are included and the estimated temperature profiles with experiments are compared. We also take into account the differential equation for the radial electric field $$E_r$$ into TASK3D. The obtained electron and ion thermal diffusivities with the Alcator, Bohm, and gyro-Bohm models indicate anomalous thermal transport dominates for electrons, while neoclassical thermal transport plays a crucial role for ions. TASK/TX, solving surface-averaged multi-fluid equations, is also applied to the LHD plasma to examine the time evolution of $$E_r$$ and plasma rotation. The transition between the electron and ion roots, and the radial structure of $$E_r$$ has been demonstrated self-consistently.

論文

Current ramps in tokamaks; From present experiments to ITER scenarios

Imbeaux, F.*; Basiuk, V.*; Budny, R.*; Casper, T.*; Citrin, J.*; Fereira, J.*; 福山 淳*; Garcia, J.*; Gribov, Y. V.*; 林 伸彦; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

In order to prepare adequate current ramp-up and ramp-down scenarios for ITER, present experiments from various tokamaks have been analysed by means of integrated modelling in view of determining relevant heat transport models for these operation phases. The most accurate heat transport models are then applied to projections to ITER current ramp-up, focusing on the baseline inductive scenario (main heating plateau current of Ip = 15 MA). These projections include a sensitivity studies to various assumptions of the simulation. Recent examples of such simulations, involving coupled core transport codes, free boundary equilibrium solvers and a poloidal field (PF) systems controller are described in the second part of the paper, focusing on ITER current ramp-down.

論文

Neoclassical relationship between the radial electric field and the radial current in tokamak plasmas

本多 充; 福山 淳*; 中島 徳嘉*

Europhysics Conference Abstracts (Internet), 35G, p.P2.137_1 - P2.137_4, 2011/00

The equation is analytically derived, stipulating the relationship between the radial electric field $$E_r$$ and radial current $$j_r$$ in tokamak plasmas, especially when heated by neutral beam injection. On a very short time scale compared to the decay in poloidal rotation, the polarization current $$j_mathrm{p}$$ compensates for the non-ambipolar fast-ion radial current, $$j_r^mathrm{fast}$$, producing a concomitant time change in $$E_r$$. This $$j_mathrm{p}$$ predominates among the constituents of $$j_r$$ that produces the $$vec{j}timesvec{B}$$ torque. On a longer time scale, $$E_r$$ should be estimated through a force balance equation. In a steady state, transport of toroidal momentum plays a dominant role in balancing the torque induced by $$j_r^mathrm{fast}$$. Analytical work demonstrates that the basis equations of the one-dimensional transport code TASK/TX essentially have the capability to reproduce the phenomena derived, which is subsequently confirmed by numerical simulation.

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