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The resistive wall mode and feedback control physics design in NSTX

机译:NSTX中的电阻墙模式和反馈控制物理设计

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摘要

One of the goals of the National Spherical Torus Experiment (NSTX) is to investigate the physics of global mode stabilization in a low aspect ratio device. NSTX has a major radius R_0 = 0.86 m, a midplane half-width of 0.7 m, and an on-axis vacuum toroidal field B_0 ≤ 0.6 T and has reached a plasma current I_p = 1.5 MA. Experiments have established the wall-stabilized MHD operating space of the machine. The maximum β_t and β_N have reached 35% and 6.5%, respectively, with β_N reaching 9.5l_i. Collapses in plasma toroidal rotation and β_t have been correlated with violation of the n = 1 ideal MHD beta limit, β_(Nno-wall), computed by the DCON stability code using time-evolving EFIT reconstructions of experimental discharges. The resistive wall mode (RWM) was observed over a wide range of β_N when β_(N no-wall) was exceeded. Plasma toroidal rotation damping during the RWM was rapid and global. Damping rates were more than five times larger than caused by low toroidal mode number rotating modes alone, which displayed a slower, diffusive rotation damping away from the rational surface. The rotation damping rate and dynamics depend on the applied toroidal field and the computed minimum value of the safety factor. The computed RWM perturbed field structure from experimental plasma reconstructions has been input to the VALEN feedback analysis code for quantitative comparison of experimental and theoretical RWM growth rates and to analyse the effectiveness of various active feedback stabilization designs. The computed RWM n = 1 mode growth rate, which depends on plasma equilibrium parameters such as β_N and pressure profile peaking, agrees well with experimental growth rates in different operating regimes. Increasing β_N in the ST initially improves mode coupling to the stabilizing wall; however, at the highest β_N values reached, the ideal with-wall beta limit, β_(N wall), is approached, the effectiveness of the passive stabilizing plates is reduced, and the computed RWM growth rate approaches ideal MHD growth rates. Several active mode control designs were considered and evaluated. The most effective configuration is computed to provide stabilization at β_N up to 94% of the ideal with-wall limit.
机译:国家球形圆环实验(NSTX)的目标之一是研究低长宽比设备中全局模式稳定的物理原理。 NSTX的主半径R_0 = 0.86 m,中平面半宽度为0.7 m,轴上真空环形场B_0≤0.6 T,并且已达到等离子电流I_p = 1.5 MA。实验已经建立了机器的墙面稳定MHD操作空间。最大β_t和β_N分别达到35%和6.5%,其中β_N达到9.5l_i。血浆环面旋转和β_t的崩溃与违反n = 1理想MHDβ极限β_(Nno-wall)有关,后者由DCON稳定性代码使用实验放电随时间演变的EFIT重建计算得出。当超过β_(N无壁)时,在很大的β_N范围内观察到电阻壁模式(RWM)。 RWM期间的等离子体环形旋转阻尼迅速而全面。阻尼率比仅由低环形模数旋转模式引起的阻尼率大五倍以上,后者显示出较慢的,远离理性表面的扩散旋转阻尼。旋转阻尼率和动力学取决于所施加的环形场和计算出的安全系数的最小值。通过实验等离子体重建计算出的RWM扰动场结构已输入VALEN反馈分析代码,用于定量比较实验和理论RWM增长率,并分析各种有源反馈稳定设计的有效性。所计算的RWM n = 1模式增长率,这取决于血浆平衡参数(例如β_N和压力分布峰值),与不同操作方式下的实验增长率非常吻合。 ST中β_N的增加最初会改善与稳定壁的模式耦合;但是,在达到最高β_N值时,接近了理想的有壁β极限β_(N wall),降低了被动稳定板的有效性,并且所计算的RWM增长率接近了理想的MHD增长率。考虑并评估了几种有源模式控制设计。计算出最有效的配置以提供高达理想壁厚限制的94%的β_N稳定性。

著录项

  • 来源
    《Nuclear fusion》 |2004年第4期|p. 560-570|共11页
  • 作者单位

    Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA;

    Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA;

    Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA;

    Los Alamos National Laboratory, Los Alamos, NM, USA;

    Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA;

    Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA;

    Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA;

    Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA;

    University of Texas at Austin, Austin, TX, USA;

    Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 原子核物理学、高能物理学;
  • 关键词

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