Hybrid Method for Tokamak MHD Equilibrium Configuration Reconstruction

A hybrid method for tokamak MHD equilibrium configuration reconstruction is proposed and employed in the modified EFIT code. This method uses the free boundary tokamak equilibrium configuration reconstruction algorithm with one boundary point fixed. The results show that the position of the fixed point has explicit effects on the reconstructed divertor configurations. In particular, the separatrix of the reconstructed divertor configuration precisely passes the required position when the hybrid method is used in the reconstruction. The profiles of plasma parameters such as pressure and safety factor for reconstructed HL-2A tokamak configurations with the hybrid and the free boundary methods are compared. The possibility for applications of the method to swing the separatrix strike point on the divertor target plate is discussed.     

Density Fluctuation Measurements Using FIR Interferometer on HL-2A Tokamak

Density fluctuations were first measured in the core region of HL-2A tokamak plasma using a newly developed multi-channel FIR interferometer system. In divertor ohmic discharges, we measured the radial density fluctuation levels of 5%, which increase to 10-20% during the appearance of MHD activity. Most of the power density in the density fluctuation spectrum is directly associated with m = 2 tearing modes. The fluctuation levels reduce to 1/3 and plasma confinement is improved during off-axis electron-cyclotron-resonance heating （ECRH）.     

HL-2A装置偏滤器室中性气体压强的初步研究

HL-2A装置上首次实现了偏滤器位形放电。采用专门研制的可在强磁场和强噪声环境下工作的快响应真空电离规对偏滤器室内的中性气体压强进行了测量,给出了HL-2A装置偏滤器有关结构的基础数据。初步研究了偏滤器位形和孔栏位形放电期间偏滤器室中性气体压强的特性。     

The first results of divertor discharge and supersonic molecular beam injection on the HL-2A tokamak

HL-2A tokamak is the first tokamak with divertors in China. The plasma boundary and the position of the striking point on the target plates of the HL-2A closed divertor were simulated by the current filament code and they were in agreement with the diagnostic results in the divertor. Supersonic molecular beam injection (SMBI) system was first installed and tested on the HL-2A tokamak in 2004. In the present experiment low pressure SMBI fuelling on the HL-2A closed divertor was carried out. The experimental results indicate that the divertor was operated in the `linear regime' and during the period of SMB pulse injection into the HL-2A plasma the power density convected at the target plate surfaces was 0.4 times of that before or after the beam injection. It is a useful fuelling method for decreasing the heat load on the neutralizer plates of the divertor.     

Impurity behaviours of HL-2A divertor tokamak during the initial operation period

The divertor configuration was successfully formed and the siliconization as a wall conditioning was first achieved on HL-2A tokamak experimentally in 2004. The divertor configuration is reconstructed by the use of the CFC code. Impurity as an important issue is investigated in the experiments with divertor configuration and wall conditioning. Impurities dramatically decrease after both the divertor configuration is formed and silicon is coated on the surface of the vacuum vessel.     

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对HL-2A装置限制器位形和偏滤器位形下放电气体分别为氘和氦时的等离子体热辐射测量结果做了初步分析,分析结果表明：在偏滤器室注入惰性气体能够有效的降低到达靶板的热辐射;超声分子束注入时,观测到注入粒子在等离子体中输运过程;氦放电时的辐射比值明显高于氘放电时的比值;真空室器壁的处理能够有效地降低辐射损失,硅化对器壁条件的改善效果明显。     

HL-2A偏滤器运行模式的探针测量

在HL-2A装置的偏滤器位形运行模式下,用偏滤器靶板上的平面型嵌入式静电探针阵列测量了同一环截面的内外和上下四个中性化板上的电子温度、密度、悬浮电位分布。偏滤器运行模式下的边缘电子温度高于孔栏运行模式下的边缘的电子温度。比较了内外靶板之间的温度不对称性。给出了由18个米尔诺夫线圈信号重建获得的磁分界面,并用强磁场快速电离规测量了偏滤器室的中性气体压强变化。测量结果表明,在偏滤器运行模式下,主真空室中边缘粒子再循环降低,杂质通量水平下降。     

辅助加热下HL-2A边界层等离子体数值模拟

以二维边界等离子体流体模拟代码B2.5为核心,编制适合于具有封闭偏滤器位形特征托卡马克的边界层网格划分代码和计算后处理代码.模拟分析HL-2A托卡马克有约3MW辅助加热功率时的边界等离子体特性.结果表明,偏滤器靶板前形成了致密低温等离子体,偏滤器运行于高再循环状态.     

HL-2A装置送气和加料的脱靶特性

HL-2A装置辐射偏滤器实验采用边缘补充送气和分子束加料等方法来提高主等离子体密度,降低边缘等离子体温度、增加辐射功率分额,获得脱靶等离子体。偏滤器室内进行主动补充送气或者注入惰性气体杂质,降低偏滤器等离子体温度,获得脱靶等离子体,并首次获得了超声分子束注入产生脱靶等离子体的实验结果。利用HL-2A装置偏滤器同一极向截面内外中性化板上安装的嵌入式探针阵列和偏滤器室安装的电动探针系统,测量了偏滤器靶板上和偏滤器室的等离子体参数及其分布,并进行了相关分析和改善约束以及偏滤器脱靶等离子体运行模式下等离子体行为的研究。     

HL-2A单零偏滤器的位形特征

利用积分方法对多种电流剖面下HL2A装置单零偏滤器位形特征进行了计算研究。积分方法的优点是可以在任意电流剖面下求解具有X-点的自由边界的Grad-Shafranov方程。对HL2A装置而言,大体上可以在合理设定的分界面形状下,经几次叠代计算出各组极向场线圈(垂直场,三对多极场和多极补偿场以及水平场)中的电流。HL-2A的单零偏滤器位形基本上是圆截面加上在X-点附近的局部形变。对刮离区和偏滤器靶板区磁力线特性进行了分析以确定偏滤器的品质。     

Analyses of edge plasma characteristics in HL-2A

The edge plasma characteristics are studied by both a movable array of Mach/Reynolds stress/Langmuir 10-probes in the boundary region and the fixed flush probe arrays on the 4 divertor neutralization plates at the same toroidal cross-section in the HL-2A tokamak. The dependence of the Reynolds stress on poloidal flow in the edge plasma is analysed. The result indicates that the sheared poloidal flow in tokamak plasma can be induced by the radial gradient of Reynolds stress. In the divertor experiments of HL-2A, the profiles of the electron temperature, density and floating potential on divertor plates are measured by the flush probe arrays. The edge electron temperature in divertor configuration is higher than that in limiter configuration. The temperature asymmetry between outer and inner target plates is observed. The result of magnetic surface reconstructed from 18 Mirnov coils signals is presented. Both the particle recycling and the impurity flux in the bulk plasma during divertor discharges are discussed. Neutral gas pressure in divertor chamber, measured by fast ionization gauge during divertor discharge, is given.     

Neutral Pressure Measured by Fast Ionization Gauge in HL-2A

A special fast ionization gauge is developed to measure the neutral gas pressure in the main chamber and the divertor chamber of the HL-2A tokamak during discharges in order to research on particle behaviors, and to control the neutral gas pressure actively in the divertor chamber to further obtain radiation or detached divertor discharges     

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利用TSC程序对HL-2M装置的纯欧姆放电参数进行了首次数值放电模拟,证实了极向场线圈系统具有实现预设的宏观等离子体参数的能力。数值放电模拟还利用基本的位移控制和等离子体电流控制系统实现了从孔栏位形到下单零偏滤器位形的稳定演变。模拟提供的一些主要结果为工程和物理目标设计提供重要的参考。     

HL-2A装置大拉长比和三角形变等离子体位形设计

介绍了基于MATLAB 程序自主开发的等离子体位形编辑和设计代码SE,包括其设计原理、主要功能、人机界面和操作步骤。通过SWEQU 代码对SE代码的准确性进行了有效验证,分别用上述两种代码设计和验证了两种具有中等拉长比和三角形变位形的放电参数。具有较高拉长比和三角形变位形的实现需要投入装置的上偏滤器线圈来突破圆形截面的限制。最后通过SE代码编辑了一个较大拉长比和三角形变的等离子体位形,并获得了相应的放电参数。结果表明,在HL-2A 装置投入上偏滤器线圈后,可以得到具有较大拉长比和三角形变的新等离子体位形,这些位形为提高HL-2A 等离子体的品质奠定了坚实的基础。     

Tokamak Experiment and Tokamak Engineering——Development of the Plasma Diagnostics on HL-2A Tokamak

The main mission the HL-2A tokamak is of the experiments on to explore the divertor physics and to investigate the plasma confinement, transport and instabilities with high power auxiliary heating and advanced fuelling, it is necessary to develop more new diagnostics and increase the spatial and temporal resolutions of the measurements for exist system. Up to now, about 30 diagnostic systems have been moved from HL-1M to HL-2A tokamak. Other 10 diagnostic systems are being designed and installed on the device. In developed in last 2 years, will be presented.     

Development of Vacuum Monitoring System in the HL-2A tokamak

HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated from the operation staff during discharges, to guarantee the safe and reliable operation of the vacuum system, it is necessary to watch the vacuum system outside the machine hall with an automatic monitoring system. The paper describes the design and manufacture of the monitoring system.     

HL-2A装置第一壁石墨组件研究

HL-2A装置的第一壁由石墨构件、Cu偏滤器靶板和AISI 304LN不锈钢真空室内壁组成。石墨构件总重量为44kg,覆盏面积为2．80,覆盖率为2．2％。由于HL-2A装置所用石墨件材料均为历经长期托卡马克实验和长期暴露大气的石墨材料,因此石墨构件的处理效果显得更为重要。介绍了EK98、SMF-800石墨材料、ASDEX装置用CFC、国产CFC的研究结果和HL-2A装置第一壁石墨材料预处理及其结果。     

HL-2A偏压偏滤器物理设计

根据已有的理论模型,推算出了HL-2A偏压偏滤器的理论电流为1．5kA、偏压电压为200V,并对HL-2A偏压偏滤器做出了初步设计。HL-2A装置采用偏压后,有可能降低L-H模转变阈功率,增加偏滤器等离子体密度、压强和滞留时间,改善约束,改善内外靶板功率沉积的非对称性,提高排灰效率及提高偏滤器性能。     

HL-2M装置雪花减偏滤器热疲劳分析

利用SOLPS软件,采用有限元数值计算方法,模拟计算了HL-2M装置雪花减偏滤器靶板上热负载分布,分析了偏滤器温度及热应力分布,并使用ITER内部器件设计评判标准对HL-2M偏滤器结构进行热疲劳寿命的评估。结果表明,在低周循环下靶板大部分区域不会经历严重的塑性疲劳,但距离外侧抽气口4mm位置拱顶区域循环寿命约为1963次。模拟结果对HL-2M装置偏滤器设计具有一定参考意义。