同轴网格空心阴极等离子体诊断及微波传输特性研究

发布时间：2018-07-10 01:56

本文选题：等离子体 + 空心阴极放电　；参考：《哈尔滨工业大学》2017年博士论文

【摘要】：近些年,电磁波与等离子体相互作用因其在火箭尾焰微波衰减、再入飞行器通信、等离子体微波诊断等领域的应用而受到广泛关注。针对电磁波和等离子体相互作用的地面实验研究具有成本低,可重复,状态可调等特点,逐渐受到重视,这些实验研究能够为理论模型的验证提供有力依据。而电磁波与等离子体相互作用的理论框架构建已日臻完善,大量的数值模拟工作被报道,但有关电磁波与等离子体的相互作用的实验研究相对较少。基于此,本课题通过设计并搭建较大尺寸的同轴网格空心阴极放电等离子体系统,建立了电磁波在该等离子中的传输模型,配合微波传输系统,研究了电磁波在不同等离子体环境中传输特性,并利用电磁波经过等离子体后相位和振幅的变化对等离子体进行诊断,提出了一种用于等离子体的多诊断方法。本论文首先设计并搭建一种新型的空心阴极放电等离子体装置,利用同轴网格电极产生大尺寸密度均匀的弱电离碰撞等离子体,整个等离子体系统包含进气系统、真空系统、中频交流电源系统以及Langmuir探针诊断系统。研究了整个系统的工作模式,不同气氛的工作状态并利用系统自带的Langmuir探针测试了等离子体的基本参数,并与光谱诊断方法进行对比,提出了一种有关等离子体的多诊断方法,为电磁波和等离子体相互作用相关研究奠定了实验基础。理论研究了同轴网格空心阴极等离子体电磁波传输特性,分析了同轴网格空心阴极放电等离子体的基本特征,建立了电磁波与等离子体相互作用的传输模型,利用电磁场的时域有限差分(FDTD)的方法,研究了等离子体电子密度、等离子体碰撞频率以及等离子体的尺寸对电磁波传输特性的影响,阐释了电磁波与等离子体相互作用的物理机制,为电磁波和等离子体相互作用的实验研究提供理论指导。设计并搭建了宽频微波传输系统,利用同轴网格空心阴极放电装置,对电磁波在空心阴极等离子体中传输展开了实验研究。针对不同放电功率和放电压强下的电磁波透射系数进行实验测量,分析了在限定等离子体体积的前提下,电磁波传输特性的影响因素,并与理论计算模型相互比较,证明电磁波在等离子体中传输与电子密度和碰撞频率有直接关系;同时,针对不同等离子体放电条件下电磁波传输的相位变化进行研究,证明等离子体的电子密度和碰撞频率在影响电磁波透射相位变化中起到决定性作用。最后,研究了微波经过等离子体后的透射衰减和相位变化,提出了一种可用于同轴网格空心阴极放电等离子体的微波诊断方法,测试了不同放电条件下电磁波在等离子体中传输的透射衰减和相位变化规律,对等离子体基本参数(电子密度、电子温度)进行诊断,并与Langmuir探针诊断方法进行对比,证明了微波诊断的准确性,完善了等离子体的多诊断方法。
[Abstract]:In recent years, the interaction between electromagnetic wave and plasma has attracted wide attention due to its applications in the fields of microwave attenuation of rocket tail flame, reentry vehicle communication, plasma microwave diagnosis and so on. Due to the characteristics of low cost, repeatability and adjustable state, the ground experiments on the interaction between electromagnetic waves and plasma have been paid more and more attention. These experimental studies can provide a powerful basis for the verification of theoretical models. However, the theoretical framework for the interaction between electromagnetic waves and plasma has been constructed, and a large number of numerical simulations have been reported, but there are few experimental studies on the interaction between electromagnetic waves and plasma. Based on this, a large coaxial grid hollow cathode discharge plasma system is designed and built in this paper, and the transmission model of electromagnetic wave in the plasma is established, which is combined with microwave transmission system. The propagation characteristics of electromagnetic waves in different plasma environments were studied. The plasma was diagnosed by the changes of the phase and amplitude of electromagnetic waves after the plasma. A multi-diagnosis method for plasma was proposed. In this paper, a new type of hollow cathode discharge plasma device is designed and built, which uses coaxial grid electrode to produce large scale weakly electrically dissociated plasma with uniform density. The whole plasma system consists of intake system and vacuum system. If AC power supply system and Langmuir probe diagnostic system. The working mode of the whole system and the working states of different atmospheres are studied. The basic parameters of the plasma are tested by using the Langmuir probe of the system, and compared with the spectral diagnosis method, a multi-diagnosis method for plasma is proposed. The experimental results provide an experimental basis for the study of the interaction between electromagnetic waves and plasma. The electromagnetic wave propagation characteristics of coaxial grid hollow cathode plasma are theoretically studied, the basic characteristics of coaxial grid hollow cathode discharge plasma are analyzed, and the transmission model of interaction between electromagnetic wave and plasma is established. The effects of plasma electron density, plasma collision frequency and plasma size on the transmission characteristics of electromagnetic wave were studied by using the FDTD method of electromagnetic field. The physical mechanism of the interaction between electromagnetic wave and plasma is explained, which provides theoretical guidance for the experimental study of the interaction between electromagnetic wave and plasma. A wide-band microwave transmission system is designed and built. An experimental study on electromagnetic wave transmission in hollow cathode plasma is carried out by using coaxial grid hollow cathode discharge device. The transmission coefficient of electromagnetic wave under different discharge power and discharge pressure is measured experimentally. The influence factors of electromagnetic wave transmission characteristics under the premise of limiting plasma volume are analyzed and compared with the theoretical calculation model. It is proved that the transmission of electromagnetic wave in plasma is directly related to the electron density and collision frequency, and the phase change of electromagnetic wave propagation under different plasma discharge conditions is studied. It is proved that the electron density and collision frequency of plasma play a decisive role in the change of transmission phase of electromagnetic wave. Finally, the transmission attenuation and phase change of microwave through plasma are studied, and a microwave diagnosis method for coaxial grid hollow cathode discharge plasma is proposed. The transmission attenuation and phase change of electromagnetic wave in plasma under different discharge conditions were measured. The basic parameters (electron density, electron temperature) of plasma were diagnosed and compared with Langmuir probe diagnosis method. The accuracy of microwave diagnosis is proved and the multi-diagnosis method of plasma is improved.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O53

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