FEB-E脱靶等离子体偏滤器的数值模拟

为了提高ＦＥＢ－Ｅ偏滤器的杂质控制和增加ＦＥＢ－Ｅ偏滤器处离子与中性气体的相互作用,用喷 气和杂质注入的方法设计了动态气全靶偏滤器。高约束Ｈ模拟态下的脱靶等离子体沿删削层（ＳＯＬ）磁力线有大的辐射功率份额（５０％￣８０％）和大的等离子体压力下降（９０％）。偏滤器上等离子体压降系数用ＳＯＬ的两点输运模型和辐射模型估算。结果显示,压降系数不仅与辐射功率份额有关,而且与ＳＯＬ驻点密度紧密相连。     

FEB-E动态气靶偏滤器的研究

在ＦＥＢ－Ｅ设计阶段,偏波器从开放式固定板靶优化为封闭式气体靶,以改善偏滤器的杂质控制和增加离子与气体的相互作用,通过喷气和注入杂质获得的部分脱靶等离子体形成了动态气体靶,喷气能降低删削层（ＳＯＬ）处等离子体温度,沪入的杂质增加了ＳＯＬ处的辐射功率,使靶板的负载降低,用ＮＥＷＴ１Ｄ编码模拟了ＳＯＬ处等离子体和杂质（硼杂质）的输运,得到了杂质、等离本温度和等离了体密度分布。着眼于杂质的滞留物辐射,优     

HL-2A装置偏滤器运行模式的探针测量

HL-2A装置是一个具有偏滤器位形的托卡马克装置，为我们开展先进偏滤器物理实验和改善主等离子体约束性能研究准备了良好的条件。等离子体的杂质含量由杂质源分布以及SOL和芯部等离子体中各种杂质输运过程确定。由于离子碰撞可导致狭窄的偏滤器入口部件处杂质溅射的增强，与起源于靶板处的杂质相比，偏滤器入口处的杂质更有效地污染芯部等离子体。     

用B2程序模拟HL-2A装置附着状态等离子体

用大型边缘多流体二维等离子体输运数值模拟程序B2模拟了HL-2A装置外偏滤器以及与之相连的刮削层内的等离子体。在不同的中心密度运行区，纯氢放电的HL-2A偏滤器可以形成不同的再循环运行模式，即线性或高再循环模式。通过控制模拟刮削层与芯部等离子体交界面处的等离子体参数，可实现对HL-2A装置再循环模式的控制。     

偏滤器靶板附近氦输运的蒙特卡洛模拟

本文用Monte Carlo方法模拟了偏滤器扁平抽气收集板附近区域的氦原子输运。考虑了氦原子被电子碰撞电离,氦原子与等离子体离子之间的弹性散射等原子过程以及离子的热运动和沿磁力线的流动。计算表明当偏滤器等离子体密度在7cm距离内从里向靶板逐渐增加约4.7倍,而温度分布保持不变时,氦灰返回靶板的几率比密度在7cm内向靶板递减4.7倍的通常正分布提高约45％。磁力线与靶板的交角、靶板的温度,边缘等离子体鞘层电位以及不同的靶材料对氦返回靶板几率的影响作了比较。得到的结果对托卡马克聚变裂变增殖堆孔栏和偏滤器工程设计有参考价值。     

托卡马克放电过程中偏滤器位形的演化

本文研制了适用偏滤器位形的１－１／２维托卡马克输运程度，并该程序模拟了托卡马克装置放电期间偏滤器位形的演化。在纯欧姆加热和有辅助加热两种放电方式下，对不同等离子体电流分布，拉长比，三角形变等参数下等离子体平衡位形的演化过程进行了计算机模拟。     

其它——DⅢ-D装置高约束等离子体大幅度ELM抑制的模拟研究

高的边缘压强梯度的H模放电可提高将来聚变反应堆的经济可行性，然而高的边缘压强梯度容易产生ELM不稳定性，它通常能把大的粒子和热负荷排到偏滤器靶板，这些ELM模限制了芯部等离子体性能和降低了偏滤器靶板的寿命。为了维持稳态的高性能等离子体，横越等离子体边界的粒子和热输运能用于粒子和杂质分布控制，因此，任何消除或者缓解大而快的ELM脉冲技术必须用另一个慢的输运过程来代替瞬时的粒子和热输运，这种技术在ITER这样的燃烧等离子体装置中是高度优先的。     

托卡马克边界等离子体数值模拟

本文用数值模拟法，通过数值求解二维多流体等离子体输运方程。来模拟托卡马克边界等离子体输运过程和输运特性。模拟计算的结果，对托卡马克偏滤器和第一壁的设计有重要意义。     

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装置偏滤器的脱靶等离子体实验

在HL-2A装置偏滤器靶板上采用嵌入式静电三探针阵列和偏滤器室内的电动扫描四探针组测量了同一极向截面的内外中性化板上和偏滤器室内的电子温度、密度、悬浮电位、空间电位、电场、电子压强及其分布,研究了偏滤器中等离子体参数的分布及非对称性和脱靶等离子体运行模式下的等离子体行为,开展了偏滤器脱离靶板等离子体的实验研究。利用主真空室的快速往复扫描三台阶式六探针系统测量了主等离子体边缘和偏滤器室内的等离子体温度、密度、粒子通量和中性粒子密度等参数,研究了脱靶等离子体的形成过程、物理特性、控制方法,以及对主等离子体性能的影响。     

Nonlinear collisional monte carlo simulations for high-temperature SOL plasma

A nonlinear Monte Carlo collisional model is applied to to investigate scrape-off layer (SOL) plasmas with high temperatures. In the proposed SOL modeling, A steady state SOL plasma, which satisfies the particle and energy balances and neutrality constraint, is determined in terms of total particle and heat fluxes across the separatrix, the edge plasma temperature, the secondary electron emission coefficient, and the SOL size. A conductive heat flux into the SOL is effectively modeled via random exchange of source particles and the SOL plasma particles. It is found that the potential drop and the electron transmission factor in the collisional SOL plasma are in good agreement with the theoretical prediction. The cooling effect of secondary electrons in the high temperature divertor operation is investigated. In such a collisionless plasma, the present nonlinear collision model is useful because the electron distribution function deviates far from a Maxwellian distribution. In the presence of strong secondary electron emission, the electron sheath energy transmission factor in the collisionless regime is found to be significantly smaller than that in the collisional regime. This fact suggests that a high-temperature divertor operation can be possible.     

氮ECR微波等离子体的电子能量分布研究

为了对ＧａＮ薄膜低温生长提供更多的活性氮，在一个腔耦合电子回旋共振（ＥＣＲ）半导体加工装置上，用朗谬探针和二次微分理论，研究了氮ＥＣＲ等离子体的实际电子能量分布。发现它们都是非麦克斯韦分布，含有高能电子，而且随着放电气压的下降和微波功率的增加，高能电子成分增加。     

第一壁泄漏杂质的分布计算

以数值计算法计算了第一壁冷却剂泄漏氦杂质在等离子体中的分布,氦分布的峰值在SOL(Scrape-ofLayer)区。当要求等离子体中心的氦浓度小于5%时,允许的最大泄漏率N_max约为0.35×10^-3Mol/s,允许的最大裂纹尺寸长约为3.1mm,宽约为0.63mm。影响杂质分布和浓度的主要因素有壁温、等离子体边缘温度、密度和SOL区的温度密度长度。壁温越低、等离子体边缘温度越低、密度越高、温度和密度长度越大,则中心杂质浓度越小,且杂质分布峰值越接近第一壁。     

Properties of the Tokamak Edge Plasma

A short review of some features of the edge plasma in limiter tokamaks is given. The limits of the simple 1-D SOL model and the relation between the core plasma are discussed. MARFE phenomena and detached plasma are closely connected with the particle and energy balance of the SOL. Their occurrence is based on the relation of plasma parameters of the edge plasma to those of the core. Important problems of plasma wall interactions are the detection of the impurity sources and sinks and the study of the impurity transport and shielding. The non-uniform character of plasma wall interactions and their dependence on the discharge performance still renders difficult any theoretical forecast of impurity distribution and transport and calls for better diagnostics.     

About bursty behaviour, coherent structures, wide scrape-off layer and large parallel flows in the edge of the Tore Supra tokamak

We present the measurements of plasma characteristics in the scrape-off layer (SOL) of the Tore Supra tokamak performed by means of reciprocating Langmuir probe. The probe is inserted into the machine from top. As the radial distance from last closed flux surface (LCFS) increases, ion saturation current exhibits stronger bursty character and its probability density function becomes increasingly skewed towards positive values. At the same time, burst duration and inter-burst time increase dramatically. We explain this phenomenon by radial propagation and dynamics of the ensemble of coherent turbulent structures of different size. The results of two-dimensional fluid modelling based of flux-driven interchange instability mechanism are in excellent agreement with experimental results. We obtained clear experimental evidence that most of the coherent structures are formed in poloidally localized region of the SOL around the outboard midplane. If the probe is magnetically connected to this region, the SOL is very wide and we detect bursty behaviour in the far SOL. On the other hand, if the probe is not magnetically connected to the outboard midplane region (magnetic field lines are intercepted by the outboard limiter), then the SOL is very thin and bursty behaviour is much less prominent. Detection of bursty behaviour in the far SOL is correlated with existence of wide SOL pointing on important role of bursty transport by means of coherent turbulent structures in establishing the width of the SOL in tokamaks. The measurements of parallel flow in the SOL shows that plasma particle radial flux coming from confinement region to the SOL is mostly poloidally localized around the outboard midplane. Our estimations show that more than 80% of plasma particle radial flux is coming from confinement region to the SOL in poloidally localized region — approximately ±15° — around the outboard midplane. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Roma, Italy, June 26–27, 2006.     

HL-2A装置快速扫描气动探针的研制和运用

快速扫描气动探针已在HL- 2A 装置上用于对边缘等离子体参数的径向分布的测量, 特别是刮离层等离子体参数的特征长度和扰动的测量。该系统采用精密的气动气缸驱动带有探针组件的长驱动杆, 其最快速度可在60 ms 时间内水平扫描8 cm 的距离。探针信号测量具有1MHz 的快速时间响应和0. 04 mm 的空间分辨率。可靠地测量了HL- 2A 装置边缘电子温度和密度的时空分布。     

Physical mechanisms in divertors and their impact on the core

The magnetic separatrix in a diverted tokamak determines the boundary between closed and open magnetic field lines. Even though the main influences on the physics of SOL and core regions may be different and shift from the plasma-neutral coupling and impurity radiation in the scrape-off layer (SOL) to anomalous plasma transport in the core, the influence of this boundary persists over some width, both into the core region and into the SOL. We give a short review of the progress in the divertor-SOL physics and discuss the links between edge core and SOL plasmas which are likely to have an important role in different edge-plasma phenomena.     

Evolution of the high-field-side radiation belts during the neon seeding plasma discharge in EAST tokamak

Divertor detachment achieved by injecting impurities or increasing density is always accompanied with various local radiation phenomena in the boundary or core plasma. This paper presents the formation and evolution of the high-field-side (HFS) radiation belts during the neon seeding plasma discharge in upper single null configuration with two directions of toroidal magnetic field in EAST tokamak. The neon mixed with deuterium seeding can induce the divertor detachment with strong radiation belts in the HFS scrape-off layer (SOL) region. With the increase of the radiation power, the plasma discharge will transit from H-mode to L-mode, and meanwhile the radiation belts move away from the near X-point to HFS SOL. When the radiation power is high enough, the radiation belts begin to move further to the other X-point along the HFS SOL, and even cause plasma disruption. The results indicate that the behavior of the radiation belts is related to the radiation power, plasma confinement performance and state of divertor detachment, which is useful for developing better feedback control methods to achieve high-performance radiative divertor operation mode.     

Measurement of natural plasma flow along the field lines in the scrape-Off layer on the JT-60U divertor tokamak

The plasma profile and parallel plasma flow in the scrape-off layer (SOL) were systematically measured using reciprocating Mach probes installed at the outer midplane and near the divertor magnetic null (x point) in the JT-60U tokamak with a single null divertor. For the ion vertical drift due to the toroidal magnetic field gradient (ion nablaB drift) directed towards the divertor, SOL plasma flow along the magnetic field lines away from the divertor ("flow reversal") was discovered at the midplane far from the divertor. A quantitative evaluation of the ion "Pfirsch-Schluter flow," wherein the parallel flow is naturally produced in a toroidal plasma, was consistent with the measurement.