电磁波在尘埃等离子体中的传输特性研究

发布时间：2018-05-31 06:11

本文选题：尘埃等离子体 + 电磁波传输　；参考：《哈尔滨工业大学》2017年博士论文

【摘要】：在宇宙空间中,物质大多以等离子体状态存在。由于人类的生产及生活,每天都会产生超过40公吨的尘埃进入地球大气层,因此在地球轨道空间中形成一种等离子体与尘埃共存的状态——尘埃等离子体。其改变了近地空间的电磁环境,对空间通信系统产生不可预估的影响,如极区中层夏季回波、夜光云等现象。同时尘埃等离子体在再入飞行器通信、火箭喷焰的微波衰减以及工业制造业等科学及工业领域的重大问题中也具有重要的应用价值。近几年尘埃等离子体中电磁波的传输问题成为科学领域研究的热点,主要是由于电磁波传输问题与等离子体诊断、空间探测、再入物理以及无线电通信等领域都密切相关。对于电磁波与尘埃等离子体相互作用的研究主要集中在尘埃声波、尘埃孤波、尘埃离子声波等方面,对尘埃等离子体中电磁波传输特性方面缺少准确、系统的理论研究,而实验研究更鲜有报道。因此本文从理论分析、数值模拟、实验验证角度入手,系统性研究电磁波在尘埃等离子体中的传输特性。本文以尘埃颗粒与等离子体复杂相互作用理论为出发点,结合统计物理学动理论方法,分别推导出弱碰撞完全电离和弱电离尘埃等离子体的介电常数表达式。弱碰撞完全电离尘埃等离子体是一个新提出的模型,由于没有中性分子的存在,电子与离子间的碰撞直接决定了电磁波的传输特性,而在弱电离尘埃等离子体中,存在大量未电离的中性气体分子,电子与中性分子的碰撞决定了电磁波的传输特性。分别建立电磁波在弱碰撞完全电离和弱电离尘埃等离子体中的传输模型,利用矩阵光学法进行数值模拟,得到电磁波的反射、透射和吸收系数与尘埃颗粒带电量、尺寸、密度以及尘埃等离子体厚度等参数的关系。对比电离度不同的两种尘埃等离子体对电磁波传输的不同影响,说明碰撞频率是影响电磁波在尘埃等离子体中传输的主要因素。采用实验室空心阴极放电等离子体产生装置,利用筛网振动装置实现低气压尘埃颗粒注入,形成较为稳定的尘埃等离子体环境。利用多物理场耦合分析软件COMSOL Multiphysics模拟产生尘埃等离子体环境,分析所产生的尘埃等离子体的相关特性,得到空心阴极放电尘埃等离子体特征参数的时空分布。同时利用朗缪尔探针对尘埃等离子体的参数进行诊断测量,探测尘埃颗粒注入前后电子密度、电子温度的变化,得到的测量结果与模拟结果相吻合,尘埃颗粒与电子、离子不断碰撞而被充电从而带上负电荷,电子密度降低。利用矢量网络分析仪配合相应的微波喇叭天线,对尘埃等离子体中电磁波传输特性进行实验研究,并与数值模拟结果进行对比。通过改变尘埃颗粒的密度以及放电腔内的电离气体成分、压强、放电功率等因素,测量不同情况下尘埃等离子体的电磁波参数,分析确定尘埃等离子体中影响电磁波传输特性的基本参数,从而得到尘埃等离子体中电磁波的传输规律。结果表明,带电尘埃颗粒的物理特性以及尘埃等离子体的放电环境都对电磁波的传输产生影响。通过本课题的研究可以发现,尘埃等离子体中尘埃颗粒对电磁波传输的影响不能忽略,同时对于降低火箭喷焰对微波衰减、减弱飞行器再入“黑障”效应、解决极区夏季回波现象等科学及工程问题提供实验基础和理论指导。
[Abstract]:In cosmic space, most of the matter exists in the state of plasma. Because of human production and life, more than 40 metric tons of dust will be produced every day into the earth's atmosphere, so a state of coexistence of plasma and dust in the earth's orbit space, such as dust, has changed the electromagnetic environment of the near earth space. The spatial communication system has an inpredictable effect, such as the phenomenon of the summer echo in the polar region and the Noctiluca cloud. At the same time, the dust plasma is also of important application value in the reentry vehicle communication, the microwave attenuation of the rocket flame and the major problems in the industrial manufacturing industry. The problem of wave transmission has become a hot topic in the field of science, mainly due to the close correlation between electromagnetic wave transmission and plasma diagnosis, space detection, reentry physics and radio communication. The research on the interaction of electromagnetic wave with dust plasma is mainly in the dust wave, dust solitary wave, and dust ion sound wave On the other hand, the transmission characteristics of electromagnetic waves in the dust plasma are lack of accurate, systematic theoretical research, and the experimental research is more rarely reported. Therefore, this paper systematically studies the transmission characteristics of electromagnetic waves in the dust plasma from the theoretical analysis, numerical simulation and experimental verification. This paper is based on the complexity of dust particles and plasma. The theory of interaction is the starting point and the dielectric constant expression of the weakly collisional fully ionized and weakly ionized dust plasma is derived by the method of statistical physics dynamic theory. The weak collision completely ionized dust plasma is a new model. Because there is no neutral fraction, the collision between electrons and ions is directly determined. A large number of unionized neutral gas molecules exist in the weak electricity from the dust plasma. The collisions between the electrons and the neutral molecules determine the transmission characteristics of the electromagnetic waves. The propagation model of the electromagnetic wave in the weak collision completely ionized and weakly ionized dust plasma is established, and the numerical value of the electromagnetic wave is established by matrix optics. The relation between the reflection, the transmission and absorption coefficient of the electromagnetic wave and the parameters of the charged particle size, size, density and the thickness of the dust plasma is obtained. The effects of the two kinds of dust plasma on the transmission of electromagnetic wave are compared. It is shown that the collision frequency is the main influence of the electromagnetic wave propagation in the dust plasma. Factors. Using a laboratory hollow cathode discharge plasma generating device, the low pressure dust particles are injected by the screen vibrating device to form a stable dust plasma environment. The dusty plasma environment is simulated by the multi physical field coupling analysis software COMSOL Multiphysics, and the dust plasma produced is analyzed. The spatial and temporal distribution of the characteristic parameters of the dust plasma of the hollow cathode discharge is obtained. At the same time, the parameters of the dust plasma are diagnosed and measured by the Langmuir probe, and the electron density and the change of the electron temperature are detected before and after the dust particles are injected. The results of the measurement are consistent with the simulation results, and the dust particles and the electrons are separated from the dust particles. By using the vector network analyzer and the corresponding microwave horn antenna, the transmission characteristics of the electromagnetic wave in the dust plasma are experimentally studied and compared with the numerical simulation results. By changing the density of the dust particles and the ionized gas in the discharge cavity, The parameters of the electromagnetic wave in the dust plasma are measured in different conditions, and the basic parameters affecting the transmission characteristics of the electromagnetic wave in the dust plasma are determined, and the transmission law of the electromagnetic wave in the dust plasma is obtained. The results show that the physical properties of the dust particles and the dust plasma are shown. The discharge environment affects the transmission of electromagnetic wave. Through this research, we can find that the influence of dust particles on the transmission of electromagnetic wave can not be ignored. At the same time, it can reduce the microwave attenuation, weaken the "black barrier" effect of the reentry of the aircraft and solve the scientific and engineering problems of the summer echo phenomenon in the polar region. Provide experimental basis and theoretical guidance.
【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;O441.4

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