【作者】 张寿彪；

【导师】 刘万东； 谢锦林；

【作者基本信息】 中国科学技术大学 ， 等离子体物理， 2010， 博士

【摘要】 作者通过仔细的调研工作,对国外已有的磁场重联实验装置进行了详细的分析,比较了各个装置的实验参数、产生重联的方法,总结了现有实验室磁场重联研究的结果:包括碰撞等离子体中的重联模型测量、无碰撞等离子体中的Hall效应及其电子扩散区的测量、离子的加速和加热测量、重联过程中的静电和电磁涨落以及重联中的辐射研究等。尽管实验室模拟已经取得了一定的结果,但是仍然还有很多需要深入研究的问题,例如电子的加速和加热过程、离子加热机制、快速的重联模型、重联的边界条件和三维效应等问题。为了进行磁场重联实验研究,在中国科技大学的线性磁化等离子体实验装置(LMP)的基础上,对装置进行了一定的改造:建造了Helicon等离子体源,相比原有的灯丝源可以产生更高的等离子体密度;设计加工了产生重联磁场位形的电流板并且研制了较大峰值电流的脉冲电流源,在电流板上通同向电流可以产生重联的磁场位形,通过改变电流的大小来驱动入流等离子体,产生磁场重联;建造了精密二维可移动装置及其磁探针、静电探针等基本的诊断工具,通过探针在二维截面上的移动可以测量出整个截面上的磁场和等离子体参数的分布;在数据采集系统方面,实现了整个放电系统及采集系统的自动化,通过计算机的串口输出,利用matlab程序控制Helicon放电的时间以及脉冲电流加入的时间,并且同时控制采集系统的采集,大大简化了在整个截面采集数据的工作量。在所有的准备工作都完成后,在2007年底到2008年初完成了整套系统的调试工作。脉冲电源在每个电流板上的电流峰值达到了3000A,通过磁探针测量,得到了真空和等离子体条件下整个截面上的磁场分布,并且通过计算得到了在实验过程中系统公共通量的变化及其等离子体电流。电流板位形下并没有可测量到的电流产生,经过分析可能是这种条件下电子被磁场位形捕获所导致,将电流板改变为电流棒,通行电子数量增加,计算得到了等离子体电流的存在。通过轴向不同位置的发射探针测量等离子体电位得到了电流加入过程中轴向电场的存在,这个电场的大小正比于重联率。通过静电探针在截面上的测量,发现在脉冲电流加入的过程中等离子体密度由先前的圆柱对称分布变为倾斜状,并且倾斜的方向随着脉冲电流方向以及轴向磁场方向的改变而改变,并且和等离子体源的方向有关。经过分析,等离子体密度的倾斜是由三维的磁场位形决定的,由于轴向电子扩散流的存在而使等离子体密度呈现倾斜状。我们把密度倾斜后的中间密度高的部分称为密度片,经实验测量这种密度片的厚度和轴向磁场有关而和等离子体密度无关。更多还原

【Abstract】 We review results from the most recent experiments in the past 2 decades inwhich magnetic reconnection has been generated and studied in controlled lab-oratory settings. Laboratory experiments are crucial for understanding the fun-damental physics of magnetic reconnection since they can provide well-correlatedplasma parameters at multiple plasma locations simultaneously, while satellitescan only provide information from a single location at a given time in a spaceplasma. We have already study detailed of the experimental device of magneticreconnection, summarize the results of magnetic reconnection in laboratory: re-connection model in collision plasma, the Hall e?ect and electron di?usion regionin collisionless plasma, ion acceleration and heating, the electrostatic and electro-magnetic ?uctuations in reconnection, electromangetic radiation in reconnection.But there are many issues need in-depth study in laboratory, such as the electronacceleration and heating, particle heating mechanisms, fast reconnection model,boundary condition of reconnection and 3D e?ect of reconnection.Based on the Linear Magnetized Plasma device(LMP) of University of Scienceand Technology of China, a experimental device of magnetic reconnection is estab-lished: built the Helicon plasma source, compared to the original filament source itcan produced the higher plasma density; design the current plate for magnetic fieldtopologies of reconnection, and developed a large pulse current sources, increasethe current of plate, drive the plasma in?ow, produced the magnetic reconnec-tion process; built the movable system in 2D cross section and the basic diagnostictools, magnetic probe, electrostatic probe and other. We can measured the plasmaparameter distribution through the moving of probe in 2D cross section; build dataacquisition systems, achieve the automation of the discharge system and the dataacquisition system, through the output of computer’s serial port, using matlabprocess control the time of Helicon discharge and the time of apply of pulse cur-rent, and same time control the collection of acquisition system, greatly simplifiesthe workload of data collection in the whole cross section.After completed of all preparations, we completed the work of the debugging of the whole system. The peak current in each current plate reached 3000A,we received the magnetic field distribution in vacuum and plasma by magneticprobe, obtained the common ?ux and plasma current in experiment. There is nocurrent generation in current plate, but in current bar, the magnitude of axialcurrent is found to scale with the number of passing particles. Parallel electricfield is measured by emissive probes, the existence of a large electric field relatedto the reconnection process is verified. Magnetic ?ux doesn’t pile up because ofthe parameter region in our case, which is consistent with the result of numericalsimulation.Plasma density is measured by electrostatic probes in the cross section, in-creased the pulse current, found the change of distribution of plasma densityby cylindrical symmetric distribution into a tilt-shaped, and the direction of tiltchange with the direction of pulse current、direction of the axial magnetic field,and the direction of the plasma source. After analysis, the tilt of plasma densitydecided by the shape of the 3D magnetic field, due the di?usion of plasma in axial,the distribution of plasma density has changed.更多还原