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論文

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

林 伸彦; 本多 充; 白石 淳也; 宮田 良明; 若月 琢馬; 星野 一生; 藤間 光徳; 鈴木 隆博; 浦野 創; 清水 勝宏; et al.

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

Towards prediction and control of JT-60SA plasmas, we are developing codes/models which can describe physics/engineering factors, and integrating them to one code TOPICS. Physics modelling: Coupling with MINERVA/RWMaC code showed that MHD equilibrium variation by centrifugal force largely affects RWM stability and the toroidal rotation shear stabilizes RWM. Coupling with OFMC code for NB torques, 3D MHD equilibrium code VMEC and drift-kinetic code FORTEC-3D for NTV torque, and toroidal momentum boundary model, predicted the core rotation of $$sim$$2% of Alfv$'e$n speed for a ITER hydrogen L-mode plasma. Coupling with core impurity transport code IMPACT showed the accumulation of Ar seeded to reduce the divertor heat load is so mild that plasma performance can be recovered by additional heating in JT-60SA steady-state (SS) scenario. Simulations coupled with MARG2D code showed that plasma current can be ramped-up to reach $$beta_N ge$$3 with MHD modes stabilized by ideal wall and with no additional flux consumption of central solenoid in JT-60SA. Engineering modelling: Coupling with integrated real-time controller showed that simultaneous control of $$beta_N$$ and $$V_{loop}$$ is possible at $$beta_N ge$$4 in JT-60SA SS scenarios. MHD equilibrium control simulator MECS demonstrated equilibrium control during heating phase and collapse induced events within power supply capability of PF coils in JT-60SA.

論文

Current ramp-up scenario with reduced central solenoid magnetic flux consumption in JT-60SA

若月 琢馬; 鈴木 隆博; 林 伸彦; 白石 淳也; 井手 俊介; 高瀬 雄一*

Europhysics Conference Abstracts (Internet), 39E, p.P5.144_1 - P5.144_4, 2015/06

We have investigated reduction of the CS flux required in the plasma current ramp-up phase using non-inductive current drive in JT-60SA with an integrated modeling code suite (TOPICS). JT-60SA will be equipped with various types of neutral beams different in the beam trajectories and energies (85 keV and 500 keV). We have made a scenario in which the plasma current is ramped up from 0.6 MA to 2.1 MA in 150 s with no additional CS flux consumption by overdriving the plasma current ($$I_{rm NI} > I_{rm p}$$, $$I_{rm NI}$$ : non-inductively driven current and $$I_{rm p}$$ : plasma current) with neutral-beam-driven and bootstrap current. In order to achieve the current overdrive condition from 0.6 MA, the current drive by the lower energy neutral beam injection (85 keV) is effective. The higher energy neutral beam injection (500 keV) cannot be utilized in this early phase with a low plasma density due to a large shine through loss, while it can effectively be utilized in the later phase. We have also investigated ideal MHD instabilities using a linear ideal MHD stability analysis code (MARG2D). External kink modes can be stabilized in most of the time during the current ramp-up if there is a perfect conducting wall.

論文

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

若月 琢馬; 鈴木 隆博; 林 伸彦; 白石 淳也; 井手 俊介; 高瀬 雄一*

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

 被引用回数:7 パーセンタイル:53.27(Physics, Fluids & Plasmas)

Current ramp-up with reduced central solenoid (CS) flux consumption in JT-60SA has been investigated using an integrated modeling code suite (TOPICS) with a turbulent model (CDBM). The plasma current can be ramped-up from 0.6 MA to 2.1 MA with no additional CS flux consumption if the plasma current is overdriven by neutral-beam-driven and bootstrap current. The time duration required for the current ramp-up without CS flux consumption becomes as long as 150s. In order to achieve the current overdrive condition from 0.6 MA, the current drive by a lower energy neutral beam (85 keV) is effective. A higher energy neutral beam (500 keV) cannot be utilized in this early phase due to large shine through loss, while it can be effectively utilized in the later phase. Therefore, the main current driver should be switched from the lower energy neutral beam to the higher energy neutral beam during the current ramp-up phase. As a result of an intensive auxiliary heating needed to overdrive the plasma current, plasma beta becomes high. Ideal MHD stabilities of such high beta plasmas have been investigated using a linear ideal MHD stability analysis code (MARG2D). External kink modes can be stabilized in most of the time during the current ramp-up if there is a perfectly conducting wall at the location of the stabilizing plate and the vacuum vessel of JT-60SA and the plasma has a broader pressure profile.

口頭

プラズマ輸送コードTOPICSを用いた、JT-60SAにおけるセンターソレイドを用いないプラズマ立ち上げシナリオ解析

若月 琢馬*; 鈴木 隆博; 林 伸彦; 井手 俊介; 高瀬 雄一*

no journal, , 

プラズマ電流の誘導立ち上げに用いる中心ソレノイド(CS)の磁束供給能力を削減して小型化できればコンパクトな核融合炉設計が可能になる。JT-60SAではそのような炉の実現可能性を調べるために、CSに頼らない立ち上げ手法の開発を計画している。本研究はJT-60SA実験に先立ち、プラズマ輸送コードTOPICSを用いてプラズマ電流の非誘導立ち上げシミュレーションを行った。プラズマの温度・密度分布の時間発展を与えて自発電流及び電流駆動を計算し、CS磁束の消費を抑えてプラズマ電流を0.6MAから2.1MAまで非誘導で立ち上げるシナリオを作成した。計算された閉じ込め時間はHモード閉じ込めの1.3倍程度であり、極端に高い値が必要とされるわけではないことを明らかにした。

口頭

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

若月 琢馬; 鈴木 隆博; 林 伸彦; 井手 俊介; 高瀬 雄一*

no journal, , 

Feasibility of current ramp-up with reduced central solenoid (CS) magnetic flux consumption should be demonstrated to envision compact tokamak reactors such as SlimCS. In JT-60SA, issues concerning compact steady-state reactors can be investigated using a variety of heating and current drive combinations (positive and negative ion source based neutral beams and electron cyclotron waves). In this paper, plasma current ramp-up scenarios with reduced CS flux consumption has been investigated on JT-60SA using TOPICS transport code. Time evolution of the temperature profile is calculated using the CDBM model with prescribed density profile. In order to minimize the resistive flux consumption, we aim at ramping-up the plasma current from 0.6 MA to 2.1 MA maintaining a non-inductive full current drive (full-CD) condition. It has been found that a large bootstrap current fraction ($$>$$ 60%) is needed to achieve a full-CD condition within the heating and CD capability planned in JT-60SA. This condition can be achieved with formation of a strong internal transport barrier. As a result, the resistive flux consumption can be reduced by a factor of 10. Since $$beta_N$$ exceeds 4 x li(3) during the ramp-up phase, we will also discuss the MHD stability.

口頭

Investigation of pressure profile controllability during plasma current ramp-up with reduced magnetic flux consumption in JT-60SA

若月 琢馬; 鈴木 隆博; 林 伸彦; 白石 淳也; 井手 俊介; 久保 博孝; 高瀬 雄一*

no journal, , 

Feasibility of plasma current ramp-up in JT-60SA without additional CS flux consumption after initial plasma formation has been investigated using an integrated modeling code suite (TOPICS). In our previous study, we developed a scenario in which the plasma current is ramped-up from 0.6 MA to 2.1 MA without additional CS flux consumption by overdriving the plasma current using neutral beams (NB) and electron cyclotron (EC) waves. The investigation of the ramp-up scenarios with several prescribed density profiles revealed that a pressure profile with an H-mode pedestal and a wide internal transport barrier (ITB) whose foot is located at a large minor radius is required in order to obtain a large bootstrap current within the MHD stability limit. In this study, we introduce a particle transport model according to experimental results of JT-60U. Particle transport is calculated by assuming that the particle diffusivity is a sum of neoclassical and anomalous diffusivities and particle pinch velocity is zero. As a result, it is shown that the location and strength of the ITB can be modified by changing the heating, current drive and fueling method using NB and EC. An ITB which is strong enough to overdrive the plasma current can be obtained within the proposed NB and EC capability at JT-60SA. We will show controllability of the pressure profile considering the ideal MHD stability.

口頭

Development of integrated real-time controls and operation scenarios for JT-60SA

鈴木 隆博; 林 伸彦; 若月 琢馬; 宮田 良明; 本多 充; 井手 俊介

no journal, , 

JT-60SAが目指す高圧力プラズマの定常維持のために、複合実時間制御手法とそれを用いた運転シナリオの開発を進めている。高圧力プラズマの維持を妨げる不安定性の発生を避けるための規格化圧力制御および安全係数最小値制御、外部コイル電流が一定となる定常運転に必要な周回電圧ゼロ制御を同時に行う複合制御コントローラを開発し、CDBM乱流輸送モデルに従うプラズマの制御性を統合コードTOPICSを用いて数値シミュレーションにより調べた。またITERで実証する核燃焼の制御に貢献するために、JT-60SAでは加熱装置により模擬した核燃焼の制御実験を計画している。そのための実時間制御コントローラを開発し、TOPICSコードを用いて制御性を調べた。これらの結果について報告する。

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