托卡马克等离子体不同平衡位形下的电子回旋波电流驱动

在给定的等离子体总电流和中心电流密度条件下,数值求解平衡方程,求出不同拉长比和三角形变因子的托卡马克等离子体温度、密度、磁场分布,然后通过求解波迹方程和Fokker-Planck方程,分别计算这些位形下的电子回旋波波迹和电流驱动.结果表明：电子回旋波X模从顶部发射时,随着拉长比的增大,波迹会向弱场侧偏移.电子回旋波X模从弱场侧发射时,电子回旋波在等离子体中传播沉积的功率份额随着拉长比的增大而增加,驱动电流位置随着三角形变因子的增大向等离子体中心移动.驱动电流位置随环向和极向发射角的减小向中心移动,对应的电流密度峰值也变大.     

Effect of poloidal density variation of neutral atoms on the tokamak edge

Neutral atoms in the tokamak edge affect the electric field and plasma flow through charge exchange. Here, it is shown that these effects depend sensitively on the poloidal location of the atoms. It is found that the radial electric field and toroidal flow velocity in a collisional edge plasma are largest if the atoms are concentrated on the inboard side. This feature may explain MAST and COMPASS-D observations indicating easier H-mode access for inboard gas puffing. The results suggest an external means of controlling the toroidal flow and radial electric field and their shear, and have motivated further MAST measurements appearing to support the predictions.     

A confident source of hard X‐rays: radiation from a tokamak applicable for runaway electrons diagnosis

In a tokamak with a toroidal electric field, electrons that exceed the critical velocity are freely accelerated and can reach very high energies. These so‐called `runaway electrons' can cause severe damage to the vacuum vessel and are a dangerous source of hard X‐rays. Here the effect of toroidal electric and magnetic field changes on the characteristics of runaway electrons is reported. A possible technique for runaways diagnosis is the detection of hard X‐ray radiation; for this purpose, a scintillator (NaI) was used. Because of the high loop voltage at the beginning of a plasma, this investigation was carried out on toroidal electric field changes in the first 5 ms interval from the beginning of the plasma. In addition, the toroidal magnetic field was monitored for the whole discharge time. The results indicate that with increasing toroidal electric field the mean energy of runaway electrons rises, and also an increase in the toroidal magnetic field can result in a decrease in intensity of magnetohydrodynamic oscillations which means that for both conditions more of these high‐energy electrons will be generated.     

Current drive for rotamak plasmas

Experiments which have been undertaken over a number of years have shown that a rotating magnetic field can drive a significant non-linear Hall current in a plasma. Successful experiments of this concept have been made with a device called rotamak. In its original configuration this device was a field reversed configuration without a toroidal magnetic field but with a vertical field to establish the MHD equilibrium. However, modifications have shown that current can also be driven if a central current-carrying rod is used to provide an applied toroidal field. The new rotamak has then a spherical tokamak magnetic field structure. Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Plasma Response to Resonant Perturbations at Tokamak Edge

In certain circumstances, plasma response suppresses magnetic islands expected at perturbed resonant magnetic surfaces. We investigate the plasma response to the resonant magnetic perturbations in a large aspect ratio tokamak perturbed by external resonant helical windings, considering polar toroidal coordinates for which analytical toroidal equilibrium solutions and perturbing fields are available. We apply an empirical approach to mimic the plasma screening effects by introducing presumed plasma current sheets on the resonance surfaces to cancel the RMP effects. Numerical examples show the effect of plasma response reducing magnetic islands at the plasma edge and also regularizing field lines around the resonant surface. The distribution of connection lengths along the plasma cross section indicates that the plasma response increases the connection lengths since more toroidal turns are performed until a field line reaches the tokamak wall.     

用偏压限制器控制KT－5C托卡马克等离子体边缘电场的实验研究

在托卡马克ＫＴ－５Ｃ上，我们首次采用可灵活组合的多块限制器进行了施加偏压以控制等离子体边缘电场的实验，结果表明，在本装置上限制器加正偏压优于加负偏压，正偏压改变等离子体边缘电场效果更明显。偏压限制器收集面积、纵场和偏置电压的大小对偏压效果的影响都是敏感的。改变限制器收集面积和偏压导致的边缘电场的变化最终将趋于饱和，另外发现，偏压限制器与等离子体柱的相对位置对等离子体边缘电场的影响也是重要的。     

HT-7超导托卡马克调制电流改善等离子体约束

 在HT-7超导托卡马克上进行了电流调制改善等离子体约束物理实验，获得了初步的实验结果。对电流调制时的径向电场进行了数值计算和讨论。当等离子体环向电流以适当的频率和幅值周期性调制时，低模数的磁流体不稳定性得到明显的抑制，等离子体中心电子温度增加了33%，等离子体电子密度分布明显陡化，能量约束时间增加了27%~45%。杂质辐射周期性减少,粒子约束时间增加了2倍。在等离子体边界产生更强的径向负电场。     

KT—5B托卡马克上阿尔芬波加热实验中天线阻抗的测量

一、引 言 托卡马克等离子体中的阿尔芬波加热实验研究自80年代初以来取得了许多有价值的实验结果。在阿尔芬波加热实验中,天线辐射阻抗的测量是十分重要的。天线辐射阻抗的变化不仅直接反映了阿尔芬波与等离子体之间的能量耦合情况,而且也反映了波在等离子体中传播过程的某些物理特性。例如,出现离散阿尔芬波(DAW模)或表面静电波(SEW模)便会使阻抗出现较大的峰值。因此,探索一种简便易行又能反映阻抗随放电时间变化的细微     

HL-1装置主机的工程调试

本文叙述了HL-1装置主机在工程调试和等离子体放电中所涉及的主要技术问题。文中详述了场形和变压器芯柱伏秒数的一些测量结果,并阐述了主机的工作状况和一些技术性能。目前该装置已运行于B_t=2.3T,I_p=135kA参数下,运行情况表明:HL-1装置主机有着较好的技术性能,基本上满足物理实验的要求。     

SUNIST低环径比托卡马克的供电系统

介绍了SUNIST低环径比托卡马克的纵向场线圈、欧姆加热场线圈和平衡场线圈的电学参数。所用电容器组储能系统采用电容换流式准恒流充电回路。测量了这三组线圈中的放电电流,并将测量结果与回路计算结果作了比较。     

J-TEXT装置纵场电源系统及其调试

J-TEXT装置的纵场磁体是由十六个近似圆形的常规铜线圈串联而成。纵场电源系统需要为纵场磁体提供最大电流为160kA、平顶时间为500ms的准梯形电流波形,以在等离子体中心产生最大为3T的磁场。基于原TEXT-U纵场电源的电路结构,重新设计和改造了电源的控制系统和保护系统。目前,纵场电源系统已经通过了测试,在J-TEXT装置首轮放电运行中,该系统可输出92.5kA的平顶电流,在等离子体中心产生了约1.74T的磁场。     

铁芯托卡马克中二维和三维极向磁场计算模型的对比分析

为方便计算托卡马克磁场分布,建立了一些二维解析铁芯模型。由于前提假设的不同而给磁场分布的计算带来了不同的边界条件,因而得到的磁场分布计算结果与实际情况有所偏差。为了获得铁芯托卡马克的极向磁场三维分布,建立了带铁芯的极向磁场线圈三维数值模型,计算铁芯托卡马克的三维磁场,与不同铁芯模型的磁场计算结果进行比较,并且研究铁芯托卡马克的三维磁场的极向分量在环向上的不对称性。     

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For simplifying the calculation the magnetic distribution on tokamak, some two-dimensional analytic models including the effect of the iron core were established, such as the infinite long iron core model and the spool model. The assumptions of these two-dimensional analytic models lead to different results with the actual magnetic field due to the distinctive boundary condition. In order to accurately calculate the three-dimensional magnetic field distribution in the tokamak with iron core, a three-dimensional numerical finite element model was established based on J-TEXT tokamak. In two conditions, where the total toroidal current is nonzero or zero respectively, more comparison were carried out between the derived results of two-dimensional models and the results at different toroidal positions in three-dimensional models. Furthermore, the toroidal asymmetry of the magnetic field distribution of the three-dimensional model of tokamak with iron core was investigated. The results indicate that the three-dimensional construction of iron core causes the toroidal asymmetric poloidal magnetic field and the difference between the two- and three-dimensional models in the condition with total current of nonzero. However, in the condition with total current of zero, the intensity of toroidal asymmetric is reduced and the difference between the two- and three-dimensional models is smaller.     

Dynamic transport simulation code including plasma rotation and radial electric field

A new one-dimensional transport code named TASK/TX, which is able to describe dynamic behavior of tokamak plasmas, has been developed. It solves simultaneously a set of flux-surface averaged equations composed of Maxwell’s equations, continuity equations, equations of motion, heat transport equations, fast-particle slowing-down equations and two-group neutral diffusion equations. The set of equations describes plasma rotations in both toroidal and poloidal directions through momentum transfer and evaluates the radial electric field self-consistently. The finite element method with a piecewise linear interpolation function is employed with a fine radial mesh near the plasma surface. The Streamline Upwind Petrov–Galerkin method is also used for robust calculation. We have confirmed that the neoclassical properties are well described by the poloidal neoclassical viscous force. The modification of density profile during neutral beam injection is presented. In the presence of ion orbit loss, the generation of the inward radial electric field and torque due to radial current is self-consistently calculated.     

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介绍了一种计算HL-2M装置环向场线圈自感的简捷方法，即用多个多边形电流丝模拟环向场线圈，用两个小直线段的互感求和代替多重积分，使问题得到简化。利用HL-2A装置的放电数据拟合计算了HL-2A装置环向场线圈的自感，从而验证了方法的正确性。     

Toroidal Effect on Lower Hybrid Current Drive in Tokamak

In the review paper of N. J. Fish, the topics concerning the basic theory of lower hybrid wave heating and current drive are presented. In the consideration of radio-frequency heating and current drive of tokamak plasma near the lower hybrid frequency, the parallel wave length is imposed by the coupling device parallel to the magnetic field and is modified by gradients along the field. The important effects are found on wave penetration and damping when the toroidal aspect ratio is low. It may be possible to change the plasma current via electron Landau damping with a coupler rf power spectrum.     

清洗放电前MUT托卡马克中的电流分布

本文利用磁探针阵测量清洗放电前ＭＵＴ托卡马克中角向磁场的分布，从而计算得到了等离子体的电流分布。结果表明，在清洗放电初期，由于存在大量杂质，等离子体的横向扩散非常大，因而。真空室的绝缘段几乎不起绝缘作用，此时所测到的环向电流中绝大部分是流经厚壁真空室的电流。     

Initial Measurements of Plasma Potential in the Core of the MST Reversed Field Pinch with a Heavy Ion Beam Probe

Measurement of the plasma potential in the core of MST marks both the first interior potential measurements in an RFP, as well as the first measurements by a Heavy Ion Beam Probe (HIBP) in an RFP. The HIBP has operated with (20-110) keV sodium beams in plasmas with toroidal currents of (200-480) kA over a wide range of densities and magnetic equilibrium conditions. A positive plasma potential is measured in the core, consistent with the expectation of rapid electron transport by magnetic fluctuations and the formation of an outwardly directed ambipolar radial electric field. Comparison between the radial electric field and plasma flow is underway to determine the extent to which equilibrium flow is governed by E×B. Measurements of potential and density fluctuations are also in progress.Unlike HIBP applications in tokamak plasmas, the beam trajectories in MST (RFP) are both three-dimensional and temporally dynamic with magnetic equilibrium changes associated with sawteeth. This complication offers new opportunity for magnetic measurements via the Heavy Ion Beam Probe (HIBP). The ion orbit trajectories are included in a Grad-Shafranov toroidal equilibrium reconstruction, helping to measure the internal magnetic field and current profiles. Such reconstructions are essential to identifying the beam sample volume locations, and they are vital in MST's mission to suppress MHD tearing modes using current profile control techniques. Measurement of the electric field may be accomplished by combining single point measurements from multiple discharges, or by varying the injection angle of the beam during single discharges.The application of an HIBP on MST has posed challenges resulting in additional diagnostic advances. The requirement to keep ports small to avoid introducing magnetic field perturbations has led to the design and successful implementation of cross-over sweep systems. High levels of ultraviolet radiation are driving alternative methods of sweep plate operation. While, substantial levels of plasma flux into the HIBP diagnostic chambers has led to the use of magnetic plasma suppression.     

托卡马克中快波电流驱动下全波方程的数值求解

用全波方法研究环形对称托卡马克等离子体中离子回旋频率范围内(ICRF)的快波电流驱动(FWCD)问题,考虑有限拉莫尔半径(FLR)效应和平行色散,建立全波计算的物理模型—全波方程,通过对全波方程的数值求解得到快波在等离子体中激发的电场强度分布.结果表明:快波可以传播到高温高密度等离子体的中心;快波在磁轴附近发生了模式转换;快波可以驱动中心的等离子体电流以改善等离子体的平衡位型;平行电场比垂直电场小三个数量级,通过垂直方向的回旋共振和平行方向的穿越期磁泵效应达到驱动电流的目的.     

托卡马克中等离子体柱的位移稳定性

本文考虑托卡马克中纵场的作用以及等离子体柱和与之有互感的外迴路的相互作用,在圆截面,瘦环假设下,得到了自由运动时相对于沿水平方向、垂直方向的位移,以及小半径变化的一般稳定条件。由于强纵场的影响,一般来说,等离子体柱的小半径总是随着大半径的变化而改变,以维持通过等离子体角向电流迴路的磁通不变。对于这种扰动,当考虑到外迴路电流变化以后,稳定区域超过公式0关键词：