Intermittent events dominated by meso-scale physics and control of a macro system in steady state spherical tokamak

稳态球形托卡马克中介观物理主导的间歇事件和宏观系统的控制

• 批准号: 21246139
• 负责人: ZUSHI Hideki
• 金额: $ 27.87万
• 依托单位: Kyushu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2009
• 资助国家: 日本
• 起止时间: 2009 至 2012
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-21246139/
• 关键词: メゾスケール; blob; fast camera; PDP

This research is aiming at the subject associated with "Intermittent events dominated by meso-scale physics and control of a macro system in steady state spherical tokamak". Mainly, structure formation and its controllability under a process from an open magnetic field configuration to the closed one, contact to two closed magnetic surfaces, and open field region outside the closed one are of interest.During the research period, 1) current start-up in tokamak using non-inductive method and 2) blob propagation crossing the SOL region, which extends from the closed flux surfaces to the open ones. These phenomena can be recognized as intermitted or off-normal events against the steady state operation of the tokamak plasma. This research aims at pointing out the characteristics of the meso-scale physics for the macroscopic structure formation under the microscopic turbulence. The evaluation for the coupling coefficient between the meso-scopic and macroscopic systems will be investigated by … More evaluation of a phase relaxation time. Finally we would like to establish control methods for steady state tokamak operation. During H21-23 experiments for rf driven non-inductive plasma production and sustainment have been performed in QUEST and CPD. The followings have been achieved.(1) Using 8.2 GHz ECWs at ~ 100 kW, non-inductive current start-up and current sustainment has been successfully demonstrated at 35 kA, which is the world record. High poloidal equilibrium at ・・p =1.5 and ・<1(triangles) has been obtained. The maximum duration of 300 sec is also performed for ST configuration. During the formation phase from the open to closed surfaces, several diagnostic tools have been applied and then the following physical picture could be drawn. The chamber aspect ratio is small enough for several harmonics to exist inside the plasma, and it has been found that the MOMFC(mirror ratio depending on the Bzcurvature) and the amplitude of Bz/Bt contribute to the fast ramp-up of the current, because ofthe initially born energetic electrons of 10 keV could be well confined in the open magnetic fields. The high ・・p~ 1 plasma scenario has been demonstrated at high MOMFC=2 and Bz/Btof 10 %. Ipof 16 kA at the high current ramp-up rate of 0.3 - 0.5 MA/s was achieved non-inductively. A natural inboard poloidal field null appeared as MOMFCincreased and this equilibrium could be sustained for ~ 10 seconds. Based on the fluctuation measurements it has been observed that the long correlation length along the magnetic surfaces has been measured when a closed surface is formed. Thisindicates that the phenomenon dominated by a mesoscopic scale occurred during the topological change.(2)The second aspect addressed in this research isthe statistical approach of the SOL turbulence, plasma transport, blob propagation.This is aimed at identification ofthe generation region of the blob by charactering the pdf of the fluctuations, two dimensional structure of pdf and statistical aspect, blob propagation and acceleration, and flow pattern in the SOL and its impact on the turbulent transport. These observations have been carried out by using the wide viewing fast camera imaging and local probe measurements. Statistical aspects of the convective transport with respect to the variation in magnetic field pitch are dwelled upon. Progressive enhancement of fluctuations and consequent blob generation and propagation are observed with the increase in Bzat a constant Bt. Amplitude and waiting time of the blobs attains a maximum for highest Bz/Bt(=7.8%). 2D statistical analysis of the images enables us to identify blobformation location precisely at the steep density gradient region. Accelerated radial propagation was observed for large sized blobs. The effect of mirror ratio on turbulence is studied with the change in poloidal field curvature. Fluctuation characteristics are quite different for magnetic shears. The region characterized by the deviation of pdf from the Gaussian to gamma can be considered as a typical scale, with which the mesoscopic phenomenon dominates. A new diagnostic and analytical method have been developed to evaluate the plasma flow using the fluctuations. Less

本研究针对的课题是“介观物理主导的间歇事件与稳态球面托卡马克宏观系统的控制”。主要研究了从开放磁场构型到封闭磁场构型、接触两个闭合磁力面以及闭合磁力面外的开场区的结构形成及其可控性。在研究期间，1)托卡马克中的电流启动采用无感方法，2)斑点传播穿过溶胶区，从闭合磁通面延伸到开放磁通面。这些现象可以被认为是不利于托卡马克等离子体稳态运行的间歇或非正常事件。本研究旨在指出微观湍流作用下宏观结构形成的细观物理特征。对于介观系统和宏观系统之间的耦合系数的评估将用…进行研究更多地评价了一种相松弛时间。最后，我们想要建立稳态托卡马克运行的控制方法。在H21-23期间，在QUEST和CPD中进行了射频驱动无感等离子体产生和维持的实验。取得了以下成果：(1)在~100kW的8.2 GHz功率下，成功地实现了35kA的无感电流启动和电流维持，创造了世界纪录。在··p=1.5和·&lt；1(三角形)处获得了较高的极向平衡。ST配置也执行300秒的最大持续时间。在从开放表面到封闭表面的形成阶段，应用了几种诊断工具，然后可以绘制出以下物理图像。由于初始产生的10keV高能电子可以被很好地限制在开放磁场中，因此腔室的长径比足够小，可以在等离子体中存在几次谐波，并且发现MOMFC(依赖于Bz曲率的镜像比)和Bz/Bt的幅度有助于电流的快速上升。在高MOMFC=2和Bz/Bt=10%时，出现了高··p~1等离子体情景。在0.3~0.5 mA/S的大电流上升速率下，实现了16kA的无感IPOF。当MOMFC增大时，会出现一个自然的内侧极向场零点，这种平衡可以维持约10秒。在涨落测量的基础上，观察到当形成闭合表面时，沿磁性表面的长关联长度已被测量。(2)本文研究的第二个方面是对气溶胶湍流、等离子体输运、气球传播的统计方法，旨在通过表征脉动的pdf、气球的二维结构和统计特性、气球的传播和加速、气球在气溶胶中的流动形态及其对湍流传输的影响来识别气球的产生区域。这些观测是通过使用宽视角快速相机成像和局部探测器测量来进行的。关于对流输运与磁场间距变化的统计方面进行了详述。随着Bzat a恒定BT的增加，涨落逐渐增强，并随之而来的斑点的产生和传播。BZ/BT最高时，斑点的幅度和等待时间达到最大值(=7.8%)。图像的二维统计分析使我们能够准确地识别陡峭密度梯度区域的起泡位置。观察到大尺寸斑点的加速径向传播。通过极向场曲率的变化，研究了镜比对湍流的影响。磁力剪切机的波动特性有很大不同。以pdf从高斯到伽马的偏差为特征的区域可以被认为是一个典型的尺度，其中介观现象占主导地位。发展了一种新的诊断和分析方法，利用起伏来评估等离子体流动。较少

项目成果

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Non-inductive Current Start-up and Plasma Equilibrium with an Inboard Poloidal Field Null by Means of Electron Cyclotron Waves in QUEST

QUEST 中电子回旋波的无感电流启动和内侧极向场为零的等离子体平衡

• 发表时间: 2012
• 期刊: Proc. 24TH IAEA FUSION ENERGY CONFERENCE
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• 发表时间: 2010
• 作者: Y.Nagai;A.Kuramoto;T.Toyama;T.Takeuchi;M.Hasegawa;細川由貴,大久保智司,石川可奈子,宮下英明;H. Zushi
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高温プラズマ力学研究センターに関連した今までの成果と将来構想

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• 作者: Rong Xu;Jinhui Wang;MasakotoKanezashi;Tomohisa Yoshioka;andToshinori Tsuru;図子秀樹
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使用 QUEST 等离子体 SOL 振荡的高阶矩评估“意外力”

• 发表时间: 2011
• 作者: 図子秀樹;西野信博;S.BANERJEE;花田和明;長谷川真;石黒正貴;田島西夜;中村一男;藤澤彰英;出射浩;坂本瑞樹;川崎昌二;中島寿年;東島亜紀;江尻晶;高瀬雄一;前川孝;御手洗修;福山敦
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