圆柱形等离子体与电磁波的相互作用

发布时间：2018-02-27 20:01

本文关键词： 低温等离子体电磁波相互作用等离子体参数　出处：《北京理工大学》2016年博士论文　论文类型：学位论文

【摘要】：等离子体是一种由大量自由运动的带电粒子构成的特殊材料,具有独特的电磁特性。在与外界电磁波的相互作用过程中,等离子体能够表现出与普通介质和金属非常不同的性质。研究等离子体与电磁波的相互作用不仅能够从理论角度加深对等离子体本身属性的理解,同时在应用领域中对各类以等离子体为基础的射频/微波器件的设计与制造也具有重要的意义。本文从数值模拟与实验两方面研究了圆柱形等离子体及其阵列与电磁波(主要是微波频段)相互作用的性质,探索其中出现的电磁波散射、等离子体激元以及光子禁带现象,分析这些现象与等离子体参数之间的关系。研究主要分为三部分:首先,利用时域有限差分(FDTD)方法,对电磁波在密度分布不均匀的圆柱形等离子体内的传播与散射进行数值模拟,研究了电子密度、碰撞频率以及密度分布类型对散射波的影响。实验上利用空心阴极放电在低气压氩气中产生不均匀等离子体柱,利用微波干涉法估算其电子密度,并测量了不同接收角度下电磁波的散射功率。模拟与实验结果表明,电子密度中心高、周围低的非均匀等离子体柱对电磁波具有明显的偏转作用,导致散射波能量的再分布。其次,模拟研究了不同条件下入射波在高密度圆柱形等离子体表面产生的等离子体激元现象。结果表明当等离子体参数和入射电磁波满足一定条件时,等离子体柱表面能够形成明显的激元,同时等离子体柱自身的消散效率出现极大值。柱面上的等离子体激元等效于沿相反方向传播的表面波相互干涉所形成的驻波,其模式随等离子体参数以及圆柱尺寸而变化。当激元出现时,等离子体柱周围的散射场将显著增强。最后,利用规则排列的多根等离子体柱组成等离子体光子晶体,数值模拟了此类光子晶体的能带结构,以及禁带性质与等离子体电子密度、碰撞频率和晶体几何参数之间的关系。实验上利用多根低气压放电管组成光子晶体,研究了管内电流、放电管数目以及管间距等参数对于入射电磁波透射率的影响。结果表明,利用圆柱形放电管可以方便地组装等离子体光子晶体,此类光子晶体具有可控的禁带结构。
[Abstract]:Plasma is a special material composed of a large number of free moving charged particles, which has unique electromagnetic properties. Plasma can exhibit very different properties from ordinary medium and metal. The study of the interaction between plasma and electromagnetic wave can not only deepen the understanding of the properties of plasma itself from a theoretical point of view. At the same time, it is of great significance to design and manufacture all kinds of RF / microwave devices based on plasma in the application field. In this paper, the cylindrical plasma and its array are studied from the aspects of numerical simulation and experiment. The nature of the interaction of electromagnetic waves (mainly in the microwave band), The phenomena of electromagnetic wave scattering, plasma exciton and photonic band gap are explored, and the relationship between these phenomena and plasma parameters is analyzed. The research is divided into three parts: firstly, the FDTD method is used. The propagation and scattering of electromagnetic waves in cylindrical plasma with inhomogeneous density distribution are numerically simulated, and the electron density is studied. The effect of collision frequency and density distribution on the scattering wave is studied. The electron density is estimated by microwave interferometry by using hollow cathode discharge to produce inhomogeneous plasma column in low pressure argon. The scattering power of electromagnetic wave at different receiving angles is measured. The simulation and experimental results show that the inhomogeneous plasma column with high electron density center and low surrounding plasma has obvious deflection to electromagnetic wave. Which leads to the redistribution of scattered wave energy. Secondly, The plasmon phenomena produced by incident waves on the surface of high density cylindrical plasma under different conditions are simulated. The results show that when the plasma parameters and incident electromagnetic waves satisfy certain conditions, At the same time, the dissipation efficiency of the plasma column is maximized. The plasma excitation on the cylinder is equivalent to the standing wave caused by the interference of the surface waves propagating in the opposite direction. The mode varies with the plasma parameters and the size of the cylinder. The scattering field around the plasma column increases significantly when the plasmon appears. Finally, the plasma photonic crystal is composed of regularly arranged plasma columns. The energy band structure of the photonic crystals and the relationship between the band gap properties and the electron density of the plasma, the collision frequency and the geometric parameters of the crystals are numerically simulated. The effects of the parameters such as the current in the tube, the number of the discharge tubes and the distance between the tubes on the transmittance of the incident electromagnetic wave are studied. The results show that the plasma photonic crystal can be assembled conveniently by using the cylindrical discharge tube. This kind of photonic crystal has controllable band gap structure.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O53;O441

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