【作者】 朱孟周；

【导师】 潘垣； 庄革；

【作者基本信息】 华中科技大学 ， 脉冲功率与等离子体， 2011， 博士

【摘要】 托卡马克实验研究显示,横越磁场的粒子输运和能量输运明显高于经典和新经典理论所预言的水平,这将会降低等离子体的约束性能,影响到未来聚变堆的经济性和实用性。许多试验研究显示这种高度反常的输运在装置边缘更为显著,它主要是由静电涨落引起的。但是产生反常输运的物理机制至今仍不明确。为了理解反常输运的物理机制,本文研究了J-TEXT托卡马克边缘的静电涨落和湍动输运特性。这对理解反常输运的物理机制,采取有效措施抑制等离子体湍流,提高等离子体约束具有重要的现实意义。本文以两套静电探针系统作为主要诊断工具,首次对J-TEXT托卡马克边缘的静电涨落和湍动输运进行了研究,并分析了静电涨落中的间歇性爆发事件及其对输运的影响,最后结合J-TEXT托卡马克等离子体为圆截面的特点,设计了一套极向探针阵列,用于研究静电涨落和湍动输运的极向分布特点,并分析了放电条件对等离子体参数极向分布的影响。主要的工作内容和实验结果如下：(1)建立了一套手动探针系统和一套极向探针阵列,并结合具体的实验目标设计了多种探针结构,例如四探针、一维径向和极向探针阵列、二维探针阵列等；(2)编写了大量的探针信号处理程序,可以实现静电涨落的湍流谱分析、相关分析、时频分析、双谱分析以及各种高阶矩统计分析等；(3)首次给出了J-TEXT托卡马克边缘等离子体的基本特性。实验观察到在最后闭合磁面附近存在自然形成的E×B流剪切。剪切层附近的静电涨落水平较低,涨落量之间的相关性降低,径向输运水平变小,温度和密度梯度变陡,存在自发形成的边界输运垒。这是欧姆放电条件下约束较好的重要因素。实验验证了在J-TEXT托卡马克边界E×B流剪切抑制湍动输运的BDT理论是成立的。(4)利用不同的探针结构研究了静电涨落中的间歇性爆发事件(IBE)。发现IBE具有高于周围等离子体的密度和径向速度。在J-TEXT边缘,其引起的输运占总输运的比重为25%-45%。在r-目平面内,单个IBE的速度大小和方向具有随机性,条件平均后的IBE则具有比较明确的速度大小和方向,径向速度Vr≈400～600m/s,极向速度Vθ≈600～1800m/s,方向分别沿着径向向外和离子逆磁漂移方向。通常幅值大的IBE要比幅值小的运动速度快。(5)对静电涨落自相似特性的研究显示,静电涨落具有明显的阵法性、f-1幂律分布和长程时间相关性,这与SOC理论预言的雪崩输运特征相一致。(6)对静电涨落的极向分布研究显示,电子温度、密度和径向粒子输运的极向分布具有明显的不对称性；对不同极向位置的密度涨落分析发现,低场侧的雪崩输运特征更为明显。改变放电条件显示,等离子体某些参数的极向分布会因为放电条件的不同而发生变化。更多还原

【Abstract】 Decades of studies on tokamaks have shown that the cross-field transport is much higher than expected in the fusion research. This will decrease the performance of plasma confinement, and thereby has adverse influence on the applicability of the fusion reactors in the future. Most experimental results have shown that the anomalous transport is more obvious in the boundary region of tokamaks. Significant contributors to the anomalous transport are the electrostatic fluctuations. However, the origin of the anomalous transport is still an open question. Therefore, we do our best to study the electrostatic fluctuations and turbulent transport in the boundary of J-TEXT tokamak, and thereby provide the possibility for deepening the understanding of the nature of the anomalous transport. This will be of great importance in finding effective measures to suppress the turbulence and enhance the plasma confinement efficiency.Two sets of Langmuir probe systems have been built and operated as the primary diagnostic tools. The electrostatic fluctuations and their influence on the radial transport are studied for the first time in the boundary of J-TEXT tokamak. The intermittent burst events (IBEs) and their influence on the radial transport are analyzed. A set of poloidal electrostatic probe array has been designed to study the poloidal asymmetry of the electrostatic fluctuations in the Scrape-Off Layer (SOL). The influence of the discharge conditions on the poloidal distribution of the plasma parameters is analyzed. The chief work and experimental results are described below:(1) Two sets of Langmuir probe systems have been built. Different probe tips have been designed according to different experimental purposes, such as four-probe array, one-dimensional radial probe array, one-dimensional poloidal probe array, two-dimensional probe array, and so on.(2) Lots of programs for the probe signal processing have been developed. A lot of detailed information about electrostatic fluctuations can be achieved using them, such as turbulent spectrum, correlation functions, bispectrum, time-frequency spectrum, higher order moments statistics, and so on. (3) The electrostatic fluctuations and their influence on the radial transport in the boundary of J-TEXT have been presented for the first time. The E x B flow shear is observed near the Last Closed Flux Surface (LCFS), where the level of the fluctuations decreases significantly, the degree of correlation between fluctuations diminishes, and the radial gradients of the electron temperature and density are higher than the other radial positions. The experimental results verify that the BDT theory is suitable near the LCFS of J-TEXT.(4) The IBEs and their influence on the radial transport are analyzed by applying lots of different probe arrays. The results reveal that the IBEs have higher density and radial velocity than their surrounding plasma. The radial transport carried by the IBEs is about 25%～45%to the total transport. In ther-θplane, the direction of movement of the single IBE is random. The average velocity of the IBEs has similar properties, the radial velocity Vr≈400-600m/s, the poloidal velocity Vθ≈600～1800 m/s, the directions of motion are outwards along the radius and along the ion diamagnetic direction, respectively. The IBEs with higher amplitude have higher velocity in most situations.(5) The electrostatic fluctuations have intermittent properties, power-law decay with the type of S(f)(?)f-1 in the power spectra, and time-long-range correlation characters. These properties are consistent with the predictions of the self-organized criticality systems (SOC).(6) The electrostatic fluctuations have poloidal asymmetry characters. The studies on the density fluctuations reveal that the SOC properties are more significant in the outside of the midplane. The discharge conditions may influence the poloidal distribution of the plasma parameters.更多还原