托卡马克高约束模边缘等离子体不稳定性研究

托卡马克高约束模运行可大幅提高磁约束核聚变等离子体约束品质,该模式下的等离子体不稳定性研究对于控制约束和保护装置有重要意义。本文主要介绍了高约束模及其边缘等离子体不稳定性的研究概况,并重点介绍了中国环流器二号A托卡马克装置上关于高约束模转换、边缘局域模特征和控制方法、台基区不稳定性和台基饱和机制等方面的研究进展。研究结果表明,实验上有望通过粒子和射频波注入等外部激励的方法,影响台基区等离子体湍流,进行控制台基动力学演化以及ELM,实现既保持高约束又降低高热负荷的等离子体稳态运行。     

High-Q Thermally Stable Operation of a Tokamak Reactor

Thermally stable subignited operation of a tokamak reactor, sustained in operation by a feedback-controlled supplementary heating source, is discussed. One-dimensional (radial) thermal stability analyses of model transport equations, together with numerical results from a one-dimensional (1-D) transport code, are used in studying the heating of deuterium-tritium (D-T) plasmas in the thermonuclear regime. The establishment of stability depends on a number of radially nonuniform nonlinear processes whose effect is analyzed. Nonuniform heat deposition resulting from plasma core supplementary heating is found to be a thermally more stable process than bulk heating. In the presence of impurity line radiation, however, core-heated temperature profiles may collapse, contracting inward from the limiter, the result of a radiation-induced instability. The effect of nonuniform transport coefficients is also discussed. Conditions are established for the realization of a subignited high-Q (Q ? 50) toroidal reactor plasma with appreciable output power (?2000 MW thermal).     

基于神经网络的托卡马克能量约束时间预测

使用机器学习理论中的神经网络方法,根据通用逼近原理对能量约束时间的复杂函数进行逼近,采用托卡马克装置的典型实验数据,设计一种组合结构的神经网络.通过大量的调参试验,给出一套性能最好的参数组合,并与传统幂指数形式的多元线性回归方法进行准确性和数据集迁移能力的比较.结果表明:神经网络模型对于能量约束时间的预测准确率更高,回...     

A Magnet Field System for a High Density Tokamak Reactor

A design for a magnet system for a high density high field tokamak reactor is described. In this design stress in the trunk of the toroidal field structure is significantly reduced by elimination of the central ohmic heating transformer. In addition all superconducting coils are operated in the steady state and pulsed fields are generated only by copper coils.     

Millimeter Propagation and High Confinement in Rhombus-Based Hybrid Plasmonic Waveguides

A hybrid plasmonic waveguide, consisting of two dielectric nanowires symmetrically put at the opposite corner angles of a rhombic metM, is proposed and numerically analyzed by the finite-element method. Simulations show that the present waveguide can achieve the millimeter propagation distance （1244 μm） and deep subwavelength mode area （5.5 × 10-3 μm2）, simultaneously. Compared with the previous hybrid waveguides based on cylinder nanowires or fiat films, the rhombie corner angles enable our waveguide to achieve both longer propagation distance and smaller mode area. This is due to the enhanced coupling between the dielectric guided mode in nanowires and the surface plasmon polariton mode at rhombic surface. Furthermore, the extreme confinement near the rhombic corner angles can strengthen the light-matter interaction greatly and make the present waveguide useful in many applications, such as nonlinear photonics, high-quality nanolazers and nanophotonic waveguides.     

兼具低非线性和高功率限制的狭缝波导（英文）

利用非线性效应的全矢量模型和狭缝波导的有限元模场求解法,系统地研究了狭缝波导结构和包层材料对其非线性和功率限制特性的影响.研究结果表明,狭缝波导的硅臂宽度、狭缝宽度、硅层高度和包层材料均影响其非线性和功率限制特性.对于空气包层狭缝波导,不同结构参数下的最高功率限制因子对应的非线性系数均高于20 W^-1·m^-1,而最低非线性系数6.5 W^-1·m^-1均出现在模式截止附近,泄露损耗较大,功率限制较弱,故空气包层狭缝波导无法同时实现低非线性和高功率限制;如果在狭缝波导上包覆二氧化硅,则可以同时获得低非线性和高功率限制,非线性系数可低至4.12 W^-1·m^-1,同时功率限制因子可达42%.     

高温超导体在未来聚变装置中的应用

简要地介绍了磁约束托卡马克装置中用超导磁体代替常规磁体的发展方向 ;叙述了可能用在聚变中的两类高温超导材料 ,并讨论了托卡马克磁体对高温超导体的特殊要求 ;描述了高温超导体的聚变应用进展 ;介绍了高温超导电流引线以及 A- SSTR2反应堆高温超导环场 (TF)线圈的概念设计     

Zero-Dimensional Model to Study the Effectiveness of Plasma Heating and Thermal Energy Confinement in Globus-M Tokamak in Ohmic Heating Modes

Experimental study of thermal energy confinement in magnetic confinement devices is one of the fundamental problems in plasma physics. The data processing technique covering kinetic and magnetic measurements performed for the Globus-M tokamak is described. A zero-dimensional code has been developed on the basis of this approach making it possible to calculate important discharge parameters during the experiment (between discharges): the electron and ion stored thermal energy content, plasma effective charge, and confinement time. Good agreement of the zero-dimensional calculations and ASTRA modeling indicates that this approach can be applied for routine data processing in Globus-M in view of the specifics of the device.     

Potential Confinement of a High Density Plasma in the GAMMA 10 Tandem Mirror

Potential confinement was demonstrated experimentally under various electron cyclotron resonance heating (ECRH) scenarios. The particle confinement time and the plasma confining potential increased with ECRH power. The plug potential formation by means of only _ce ECRH was studied by Monte-Carlo simulation. Potential confinement experiments have advanced in higher density region up to 4×10¹² cm^-3. The higher density plasma was obtained by high frequency ICRF heating and recently installed neutral beam injector in the central cell. Studies of scaling relation of the potential confinement with respect to the plasma density have started with the high density plasma.     

Mirnov Oscillations in a Small Tokamak

The confinement, the stability conditions, and the main characteristics of the detected Mirnov oscillations in the small tokamak TBR-1 are presented. The discharges investigated can be characterized, in terms of MHD activity, in two distinct regimes as the safety factor at the limiter ql is changed from 4 to 7.     

Thermonuclear Instabilities and Fueling in a Tokamak Reactor

The problem of fueling is of primary importance in the conceptual design of a fusion reactor. We consider a possible mechanism of supplying fresh fuel from a cold-plasma layer at the surface of the plasma. The existence of an energetic component of ions, viz, the alpha particles, may excite unstable collective oscillations of the plasma (called the thermonuclear instabilities). Such instabilities could give rise to microscopic processes which, in principle, would allow influx of fresh fuel while helping efflux of reaction products. A three-regime model is used to understand the nature of such fueling mechanisms and the possibility of using a cold-plasma layer as a surface fueling source.     

用单块激光器和环形外腔获得稳定的532 nm激光

采用单块半非平面Nd:YAG单频环形激光器和环形外腔倍频技术，获得了单频功率249.5mW的532nm波长的绿光输出，倍频效率43.2%，实现了倍频腔与激光器之间的跟踪锁定，倍频光功率稳定性优于1％，理论计算与实验结果一致。     

东方超环(EAST)装置中等离子体边界锂杂质的碰撞-辐射模型

在东方超环(EAST)装置中,由于大量锂化壁处理的使用,切向可见光摄像机拍摄到等离子体边界通常存在一条由锂(Li)杂质形成的绿色发光带.本文基于EAST边界等离子体参数条件,基于碰撞-辐射模型给出由已知边界等离子体状态推算Li绿光光强的空间分布的具体方法,并针对简化后的一维径向分布问题,收集、处理OPEN-ADAS数据库的数据,采用软件Mathematica 10.4.1编写相应的数值计算程序,分别输入EAST工作于低约束(L)与高约束(H)模时获得的两组边界电子温度、密度分布数据,给出并分析比较了利用该模型的计算结果.此项工作对于未来建立通过测量及反演边界锂杂质特征谱线强度的空间分布来重构边界等离子体状态的全新技术和研究存在三维磁场扰动条件下的边界等离子体行为均具有重要的理论参考价值.     

EAST边界和芯部杂质谱线的时间延迟研究

边界杂质注入是未来聚变装置ITER用于增强边界辐射,减少第一壁热负荷的一种重要方法。但部分注入的杂质会被输运到芯部,造成主等离子体辐射损失以及约束下降。光谱观测可以获取杂质种类、含量和分布等信息,在理解等离子体中杂质输运方面起着重要作用。在EAST(experimental advanced superconducting tokamak)偏滤器氩气(Ar)注入实验中,利用偏滤器可见光谱和芯部极紫外光谱监测边界的Ar¹⁺离子谱线ArⅡ(401.36 nm)和芯部的Ar¹⁵⁺离子谱线ArⅩⅥ(35.39 nm),并获得两者强度随时间的变化。其中,ArⅡ和ArⅩⅥ的电离能分别为27和918 eV,因此,ArⅡ和ArⅩⅥ分别对应分布于等离子体边界和芯部Ar离子。为了分析二者谱线强度随时间变化的特征,发展了一种基于正则Pearson积矩相关系数的相关分析方法,计算得到两者谱线强度变化的相对延迟时间,以此表征杂质从边界向芯部输运的时间。结果显示,偏滤器注入Ar杂质后,芯部ArⅩⅥ辐射增长滞后于边界ArⅡ辐射的增长,并且在具有较高的低杂波加热功率的放电中...     

Intermittent Structures in the High Field Side Boundary of the HYBTOK-II Tokamak

The spatial and temporal characteristics of the turbulence in the inboard and outboard scrape-off layer (SOL) of tokamak HYBTOK-II have been studied using poloidal probe array. Bursty behaviour with intermittent bursts was observed for both outboard and inboard SOL. In the inboard (high field side), high level of density fluctuations has been observed. The fluctuations in the high field side and low field side are identical in statistics that is non-Gaussian one.     

Study of laser output power stabilization for a deuterium cyanide laser interferometer on the Experimental Advanced Superconducting Tokamak

A control system which can improve stabilization of laser power in long-term operation automatically is designed for a deuterium cyanide (DCN) far-infrared laser interferometer on the Experimental Advanced Superconducting Tokamak. It stabilizes the output power of the laser by a closed-loop control system aided by a programmable logic controller. The system has been applied to the DCN laser and it has been proven that it is effective in stabilizing the laser near the highest scope of the output power.