HL-2A装置边缘等离子体的实验观测

HL-2A装置边缘等离子体在中平面的特性是通过可移动的探针组、快速扫描气动4探针和LHW天线边缘的固定4探针进行研究的。用于测量主等离子体边缘的温度、密度、悬浮电位、空间电位、径向和极向电场、雷诺协强、径向和极向等离子体流速及其径向分布。偏滤器靶板上的14组嵌入式静电3探针阵列用于测量同一环向截面的内外中性化板上的电子温度、密度、悬浮电位及其分布。     

HL-2A装置边缘扰动特性的研究

HL-2A装置边缘等离子体的扰动特性是通过中平面往复快速扫描气动6探针组来进行研究的。它在一次放电中能测量边缘等离子体参数的时空分布及其涨落量，以及静电涨落驱动的粒子通量和热通量在径向的变化。分析了在多发弹丸注入（MPI）、多脉冲超声分予束注入（SMBI）和电子回旋加热（ECRH）条件下的边界等离子体特性，研究边缘参数的涨落和相关特性。     

快速扫描探针在HL-2A装置边缘的参数分布测量

快速扫描探针系统在国内外的很多托克马克装置上得到广泛的应用，在等离子体的边缘SOL层所测量的物理参数都具有很高的时空分辨率。HL-2A装置上的扫描探针系统由传输杆、光栅尺、快速响应电磁阀、步进电机构成。在同一次放电条件下能测量的物理量有电子温度、电子密度、悬浮电位、极向电场和径向电场等参数。HL-2A装置的大半径为1．65m，小半径为0．4m，加热方式有中性束注入和电子回旋共振加热。     

HL-2A等离子体边缘的快速单探针测量

介绍了对HL-2A装置中平面边缘等离子体的单探针测量。单探针是安装在可径向移动、并可绕轴旋 转360o的传动杆上的。在1MHz的快速采样频率下,测量了主等离子体边缘的温度、密度、悬浮电位、空间电位、极 向等离子体流速的径向分布。测量的结果表明,利用单探针测量的主等离子体边缘参数与朗缪尔四探针测量结果 基本一致。     

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在一次稳定放电过程中利用快速扫描气动探针系统得到电子温度、密度、等离子体电位、极向电场以及它们的涨落、粒子通量、能量通量在径向的分布。研究了HL-2A装置边缘的静电涨落及其输运。实验结果指出,在等离子体边缘涨落量不服从玻耳兹曼关系,存在由于等离子体空间电位的梯度所产生的径向电场剪切层。分析了涨落对边缘约束的影响。     

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。     

HL-2A装置边缘等离子体参数测量

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。HL-2A装置主真空室的活动马赫／雷诺协强／朗缪尔10探针阵列具有很高的时间和空间分辨能力，能够直接测量边缘等离子体参数并研究边缘扰动和相关特性。大量的实验表明：约束的改进与旋转速度的增加和边缘涨落的下降密切相关。     

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用中平面往复快速扫描6探针组观测HL-2A装置边缘等离子体的扰动特性。在一次放电中能测量到边缘等离子体参数的时空分布及其涨落量，雷诺胁强与极向流和带状流的关系，以及静电涨落驱动的粒子通量和热通量的径向变化。在多发弹丸注入(MPI)和多脉冲超声分子束注入(SMBI)条件下，研究了边缘参数的涨落和相关特性。实验结果表明：SMBI和MPI等注入手段改变了边缘的扰动特性；雷诺胁强的径向梯度可以驱动带状流，抑制湍流输运。     

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 装置的边缘参数测量

HL-2A 装置中平面边缘的等离子体特性通过磁力传动的马赫/ 雷诺协强/ 朗缪尔10 探针组进行了研究。10 探针组安装在可径向向里和向外移动, 并可绕轴旋转360^o 的传动杆上, 用于测量主等离子体边缘的温度、密度、悬浮电位、空间电位、径向和极向电场、湍流的雷诺协强、径向和极向等离子体流速及其径向分布。HL- 2A 装置的实验结果表明, 边缘等离子体扰动诱发的雷诺协强产生了边缘极向流; 雷诺协强的径向梯度驱动带状流抑制了湍流输运。     

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。     

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介绍了一种对等离子体边缘进行径向扫描的往复静电探针系统,该系统由高压气源、传输杆、光栅尺、探针组件构成。它在一次放电中能测量主等离子体边缘的温度、密度、悬浮电位、空间电位、离子饱和电流、极向电场、粒子通量等参数的径向分布以及电子温度和密度的衰减长度。测量结果表明,利用该系统测量的主等离子体边缘参数分布与JT-60U、TEXT、HT-7等装置上测量的结果一致。     

The observation of field-aligned current during type-III ELM in EAST

Measurements of current-carrying filaments associated with Type-III edge localized mode (ELM) have recently been made in the Experimental Advanced Superconducting Tokamak by direct probing of the edge plasma using an advanced, fast-moving electrostatic and magnetic probe system. Contrary to expectations, no current filaments were detected near the separatrix. However, a clear signature of current filament has been observed in the far scrape-off layer (SOL) where the difference of the voltage between the divertor plates connecting a filament is sufficiently large, thus strongly suggesting that the current-carrying filaments form in the SOL, rather than being ejected from the plasma inside the separatrix. These findings provide, for the first time, information on the formation and sustainment of current filaments during type-III ELMy H-modes.     

相干结构Blob在HT-7托卡马克边界的传播

相干结构Blob的间歇爆发清晰地反映在HT-7托卡马克边界探针的离子饱和流信号中,Blob 的径向传播在近刮削层堆积出一个温度和密度的平台区,使密度和温度分布偏离了指数分布.条件平均方法提示了间歇脉冲结构空间分布的均匀性,Blob内部等离子体参数远高于背景等离子体参数,并且呈现出涡旋的形态.最后闭合磁面附近的数据显示,...     

Application of Emissive Probes for Plasma Potential Measurements in Fusion Devices

In experimental fusion devices, up to now, only cold probes were used to determine the plasma potential in the s crape‐ o ff l ayer (SOL), and their floating potential was assumed to be proportional to the plasma potential. However, drifting electrons or beams shift the current‐voltage characteristic of a cold probe by a voltage, which corresponds to the mean kinetic energy of the drifting electrons. This problem can be avoided by the use of electron emissive probes, since an electron emission current is independent of electron drifts in the surrounding plasma. In addition emissive probes are insensitive to electron temperature fluctuations in the plasma. We have used an arrangement of three emissive probes in the edge plasma region of ISTTOK (Instituto Superior Técnico tokamak) at Lisbon. The probes have been mounted in such a way that the tips are positioned on the same poloidal meridian but on different minor radii in the SOL. With this arrangement, the plasma potential has been measured in the edge region of the ISTTOK, and first results are presented in this contribution.     

Bias Effects on the Reynolds Stress Using the Multi-Purpose Probe in IR-T1 Tokamak

The effect of the positive bias on Reynolds stress(RS) and its effect on the radial turbulent transport at the edge plasma(r/a = 0.9) and scrape-off layer(SOL) region of plasma in tokamak are investigated.The radial and poloidal electric fields(E_T,E_p) and ion saturation current(I_s) are measured by multi-purpose probe(MPP).This probe is fabricated and constructed for the first time in the IR-Tl tokamak.The most advantage of this probe is that the variations of E_T and E_p can be measured in different radii at the single shot.Thus the information of different radii can be compared with high precision.The bias voltage is fixed at V_(bias) = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9.Moreover,the phase difference between radial and poloidal electric fields,and temporal evolution of the RS spectrum detected by MPP are calculated.RS magnitude on the edge(r/a = 0.9) is more than its vaiue in the SOL(r/a = 1.02).With the applied bias 200 V,RS and the magnitude of the phase difference between E_T and E_p are increased,while the radial turbulent transport is decreased simultaneously.Thus it can be concluded that RS affects radial turbulence.Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a=0.9 in the presence of bias.     

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.     

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.