Investigation on the drives of the poloidal flow in the ohmic and biased electrode experiments

The experimental investigation on the drives of the poloidal flow in KT-5 D tokamak are presented. It is found that the poloidal flow is the main contributor to the radial electric field, and the Reynolds stress can drive significant poloidal flows in ohmic discharges. The investigation on the relationship between the radial gradient of Reynolds stress and the poloidal flow in biasing discharges indicates that not only Reynolds stress but also the Lorentz's force can drive the poloidal flow.     

Sheared poloidal flow driven by mode conversion in tokamak plasmas

A two-dimensional integral full-wave model is used to calculate poloidal forces driven by mode conversion in tokamak plasmas. In the presence of a poloidal magnetic field, mode conversion near the ion-ion hybrid resonance is dominated by a transition from the fast magnetosonic wave to the slow ion cyclotron wave. The poloidal field generates strong variations in the parallel wave spectrum that cause wave damping in a narrow layer near the mode conversion surface. The resulting poloidal forces in this layer drive sheared poloidal flows comparable to those in direct launch ion Bernstein wave experiments.     

Simulation on effect of poloidal power spectrum on lower hybrid wave propagation

The coupling of lower hybrid wave to the plasma is a crucial issue for efficient current drive in tokamaks. This paper establishes a new coupling model which assumes the antenna to be a curved face and the plasma to be a cylinder. Power spectrum considering the coupling between wave-guides in both poloidal and toroidal direction is simply estimated and discussed. The effect of the poloidal wave vector on wave propagation, power deposition and driven current is also investigated with the help of lower hybrid current drive code. Results show that the poloidal wave vector affects the ray tracing, and also has effect on power deposition and driven current. The effect of the poloidal wave vector on power deposition and driven current profile depends on plasma parameters. Preliminary studies suggest that it seems possible to control the current profile by adjusting the poloidal phase difference between the waveguide in poloidal direction.     

A model of the solar magnetic cycle with a meridian stream closed inside the convective zone

A dynamo model of the solar cycle suggesting a relatively new mechanism for generation of poloidal magnetic fields is studied. This model considers the meridian motion in which the material rises at the equator and sinks at the poles and allows the magnetic fields from the solar surface to be transferred to the generation layer at the base of the convective zone. In addition to the surface stream of material and large-scale magnetic field from the equator to the poles, we assume the looping of a new poloidal magnetic field near the poles. At the base of the convective zone, thin meridian streams transfer the end of that loop from the poles to the equator. The loop consists of poloidal fields on the top and at the bottom of the stream near the base of the convective zone. Thus, new poloidal magnetic fields, which are opposite in sign to the poloidal fields of the current solar cycle, are generated in the depth of the convective zone. New poloidal fields on the top of the stream become the fields of a new 11-year cycle. At the bottom of the meridian stream, the direction of the poloidal magnetic field is the same as the direction of the poloidal field of the current solar cycle. The lifetime of the deep-seated poloidal field is much longer than 11 years, due to the motion of the material which keeps it from rising too rapidly. The meridian loop of the subsequent solar cycle has a poloidal field opposite in direction to the poloidal field at the base of the convective zone. This counterbalances the poloidal field at the bottom of the meridian stream. The numerical model calculates the magnetic fields in the surface and bottom layers of the convective zone.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1187–1193, October, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Grant No. 93-0217133 and the International Science Foundation under ISF Grant No. JB5100.     

托卡马克中极向静电天线的离子Bernstein波的耦合计算

本文采用均匀的等离子体模型,对在托卡马克低场边由极向静电天线激发离子Bernstein波(IBW)的耦合问题作详细的理论分析。为了能更符合实验中的实际情况,文中考虑天线为有限长度以及非零的极向波数(k_y≠0)对耦合特性计算的影响。计算表明,极向静电天线可以有效地在等离子体中激发IBW。比较该天线与传统的环向IBW天线的辐射功率谱和阻抗等计算结果,表明两种天线对IBW的耦合有相似的特性。 关键词：     

EDGE REYNOLDS STRESS STRUCTURE OF LOWER HYBRID WAVE INJECTION IN THE HL—1M PLASMA

The radial profiles of electrostatic Reynolds stress,plasma poloidal rotations,radial and poloidal electric fields have been measured in the plasma boundary region on the HL-1M tokamak using a multi-array of Mach/Langmuir probes.During experiments of lower hybrid wave current drive,the variations in LHW drive power xill cause changes in the edge electric field,poloidal rotation veloity and Reynolds stress.The results indicate that sheared poloidal flow can be generated in the edge plasma due to radially varied Reynolds stress.     

A pθ, pz dependent equilibrium solution for the cylindrical pinch

We have obtained a solution of the cylindrical pinch equilibrium equation with both a poloidal and a longitudinal current. The β poloidal is typically between 0.1 and 0.5. The ratio of poloidal and toroidal currents is estimated.     

电子回旋波驱动的托卡马克芯部等离子体极向旋转

提出了一个驱动托卡马克芯部等离子体极向旋转的新途径：用电子回旋波产生芯部等离子体极向旋转.物理机制如下：在高功率的电子回旋波加热的托卡马克等离子体中，共振局域化现象将产生极向电场从而形成极向外高内低的离子密度分布；这个极向离子的积累可以克服来自磁泵的阻尼而使等离子体极向旋转退稳定.从流体力学方程和漂移动力学方程中，得到了等离子体旋转退稳的判别式.结果表明现有的电子回旋波加热功率水平可以驱动芯部等离子体的极向旋转. 关键词：     

HL-1M托卡马克边缘参数和雷诺胁强的径向分布

利用多组马赫/郎缪尔探针测量了HL-1M装置刮离层和边缘静电雷诺胁强，等离子体极向旋转，径向和极向电场的径向分布，在低杂波电流驱动，超声分子束注入，多发弹丸注入和中性束注入实验中，给出了雷诺胁强和极向流的关系。结果表明，由于雷诺胁强的径向变化，托卡马克等离子体可以自发地产生剪切极向流。     

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HT-7上用于低杂波电流驱动的相控波导阵天线采用的是标准波导,长和宽都是有限值。在考虑了天线上下排波导之间可能存在的极向相位差以及电磁干扰时,通过数值模拟的方法,分别得到了低杂波在环向方向的平行功率谱和在极向方向的极向功率谱。由于极向波矢的存在,低杂波进入等离子体的入射方向会发生改变。最后在不同极向相位差下对低杂波进入等离子体的入射方向进行了简要的计算和讨论。     

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HT-7上用于低杂波电流驱动的相控波导阵天线采用的是标准波导,长和宽都是有限值。在考虑了天线上下排波导之间可能存在的极向相位差以及电磁干扰时,通过数值模拟的方法,分别得到了低杂波在环向方向的平行功率谱和在极向方向的极向功率谱。由于极向波矢的存在,低杂波进入等离子体的入射方向会发生改变。最后在不同极向相位差下对低杂波进入等离子体的入射方向进行了简要的计算和讨论。     

Magnetohydrodynamic mechanism for pedestal formation

Time-dependent two-dimensional magnetohydrodynamic simulations are carried out for tokamak plasmas with edge poloidal flow. Differently from conventional equilibrium theory, a density pedestal all around the edge is obtained when the poloidal velocity exceeds the poloidal sound speed. The outboard pedestal is induced by the transonic discontinuity, the inboard one by mass redistribution. The density pedestal follows the formation of a highly sheared flow at the transonic surface. These results may be relevant to the L-H transition and pedestal formation in high performance tokamak plasmas.     

DESTABILIZATION OF THE POLOIDAL ROTATION IN A MULTIPLE ION SPECIES TOKAMAK PLASMA

The destabilization of the poloidal rotation for the species of ions with the poloidally inhomogeneous sources or sinks is studied in multiple ion species tokamak plasmas. Based on the fluid equations, the evolution equation of the poloidal ion rotation speed is derived analytically. The magnitude of the inhomogeneous sources or sinks needed to destabilize the rotation is shown to be proportional to the ion density. It is suggested that the poloidal plasma rotation can be generated by destabilizing the rotation of the minority ions.     

基于实时Linux的极向场电源主控制系统的设计

为了满足极向场电源控制系统严苛的实时响应的要求,选择实时Linux系统作为系统平台,采用一个开放源代码的、基于C/C++的Eclipse可扩展的开发平台作为开发工具,完成极向场电源主控制系统的设计,实现了在一个控制周期内(1ms)对极向场电源系统的12套本地控制器的实时通信和实时控制。对极向场电源主控制系统的高速通信和实时控制、稳定可靠等关键问题给出了可行的实践性的解决方法。经实验测试,该设计运行稳定,能满足极向场电源控制系统的实时需求。     

Stability of highly shifted equilibria in a large-aspect-ratio tokamak

High beta poloidal tokamaks can confine plasma pressures an order of magnitude higher than their low beta poloidal counterparts. The theoretical stability of these high beta poloidal magnetohydrodynamics equilibria was left unresolved for many years. Using modern computational tools, such configurations are now found stable to Mercier, resistive and high-n (ideal and resistive) ballooning criteria as well as fixed and free-boundary modes for a wide range of current density profiles in the framework of a low field large-aspect-ratio machine.     

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According to the high real-time and high-reliability control requirements of ITER high-power poloidal field power supply, the industrial Ethernet field bus EtherCAT (Ethernet Control Automation Technology) with high real-time communication performance is selected to design the ITER poloidal field power field layer monitoring system. Due to the characteristics of large size and distributed distribution of the ITER poloidal field power supply device, as well as to ensure high reliability data transmission, the reliability of two kinds of EtherCAT ring network redundancy topologies are compared, and the EtherCAT ring network redundancy topology where the last station in slave station unit is an extension module converting E-BUS to 100BASE-TX/FX is more reliable and is adopted to design the structure of the poloidal field power supply monitoring system. The configuration software TwinCAT (The Windows Control and Automation Technology) is used to configure the system, and Human Machine Interfaces with functions such as visual display and control of live signals are drawn by this software. The experimental tests and operation demonstrate that the system can preferably realize real-time monitoring of hundreds of analog and digital signals on the field layer, and meet the high real-time and reliability control requirements of the ITER poloidal field power supply.     

基于EtherCAT的ITER极向场电源现场层监控系统设计

根据ITER 大功率极向场电源高实时性与高可靠性控制的需求,选取了具有高实时通讯性能的工业以太网现场总线EtherCAT(以太网控制自动化技术)设计ITER 极向场电源现场层监控系统。依据ITER 极向场电源装置体积大、分布较为分散的特点,为保障高可靠性的数据传输,对比了可构成的两种EtherCAT 环网冗余拓扑的可靠性,选取从站单元中最末端从站是将E-BUS 转换为100BASE-TX/FX 的拓展模块的可靠性较高的环网冗余拓扑来设计极向场电源现场层监控系统的拓扑结构。使用了组态软件TwinCAT(基于Windows 的控制和自动化技术)对系统进行配置,同时绘制了具有可直观显示并控制现场信号等功能的HMI 界面。经测试,该系统可实现对现场层数百路模拟与数字量信号的实时监控,满足了ITER 极向场电源的高实时性与可靠性的控制需求。     

Turbulent saturation of tokamak-core zonal flows

Current theories of zonal flow dynamics focus on the transport of poloidal momentum. Different from a cylinder, stationary poloidal flows in a tokamak are accompanied by (possibly kinetic) flows along the magnetic field, which maintain incompressibility, and comprise the major part of the flow energy. In numerical turbulence studies, the flows saturate by the turbulent diffusion of the parallel flow, whereas the poloidal momentum transport continues to strongly drive the flows.     

Effects of plasma parameters on viscosity

A numerical code is developed to study the effect of ion density and temperature (as well as ion pressure and temperature gradients) on the amplitude of the local maxima of the poloidal viscosity with respect to the poloidal Mach number using the model developed by Shaing (1993). The sum of the poloidal viscosity and ion-neutral collisions is determined from the dependence of the plasma radial current on the radial electric field in a biased electrode experiment. The experimental results in the interchangeable module stellarator agree qualitatively with the predictions of the numerical calculation regarding the effects of variation of ion density and temperature on viscosity     

Observation of extended poloidal structures in the turbulent edge plasma of the L-2M stellarator

Results are reported from an experimental study of the characteristics of the turbulent edge plasma in the L-2M stellarator. Extended coherent structures are observed to form in the poloidal direction. The poloidal coherence length of the fluctuations reaches 20 cm. The coherence of the fluctuations depends appreciably on the poloidal azimuth and is maximum along the outer edge, as is natural for unstable modes in a toroidal plasma. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 634–639 (10 May 1998)