等离子体电磁特性研究及应用

【作者】 檀雷；

【导师】 顾继慧；

【作者基本信息】 南京理工大学 ， 电磁场与微波技术， 2010， 硕士

【摘要】 本文通过两个工程应用实例——“等离子体对炮口电磁感应装定系统的附加磁效应”和“深空探测中航天器再入过程时黑障现象”对等离子体电磁特性进行了研究。本文对小型高射炮在实弹环境下,炮口等离子体的产生机理及等离子体电离浓度进行了分析与计算,依据计算所得的等离子体中自由电子浓度分析了炮口由空气电离所产生的附加磁场的大小和规律及其对原磁场的影响。并针对性地设计了一套利用“重活塞压缩器”模拟实弹环境下等离子体的生成,用接触式等离子体诊断法——“微波共振探针测量法”测量模拟生成的等离子体中自由电子浓度的实验方案以验证理论分析的合理性。研究结果表明炮口等离子体产生的附加磁场改变了原工作磁场的磁力线分布,使原平行分布的磁力线变为螺线形分布,使电磁感应装定的灵敏度降低,这对于可靠性要求很高的炮口电磁感应装定系统来说,是十分不利的。本文从对电磁波在等离子体中传播特性的研究出发,分析了深空探测中航天器再入过程时黑障现象的产生机理及航天器穿越大气层不同高度时,等离子体鞘套对不同工作频段电磁波能量的吸收衰减,并使用Matlab进行数值仿真。研究结果表明航天器再入到大气层特定高度时,由于等离子体鞘套对入射电磁波的衰减作用将必然导致黑障现象的出现,提高电磁波频率可有效减小黑障区域高度,但目前还未能有彻底消除黑障现象的方法。更多还原

【Abstract】 This paper studies the electromagnetic properties of the plasma by the two examples—"The additional magnetic effect of plasma on muzzle electromagnetic induction setting system "and" The Blackout phenomenon of spacecraft re-entry procedure in deep space exploration".The paper analyzes the produced principium of muzzle plasma and calculates the electron density of the plasma for the small anti-aircraft artilleries in the live environment. According to the calculated plasma concentration of free electrons, we analyze the intensity and the regularity of the additional magnetic field produced by the air ionization, and the additional magnetic effects to the original magnetic field. This paper designs a specific experiment, which uses "Heavy piston compressor" to imitate the plasma generation on the actual working conditions. A method called contact plasma diagnostic method—"Microwave resonator probe measurements" is used to measure free electron density of the plasma. The experiment is used to prove that the theoretical analysis is reasonable. The results show that the additional magnetic field produced by muzzle plasma changes the distribution of original magnetic field lines and makes the parallel magnetic field lines into spiral-shaped distribution, which reduces the sensitivity of the electromagnetic induction setting system and it is very unfavorable for high reliability of the electromagnetic induction setting system.According to propagation characteristics of electromagnetic waves in a plasma, this article analyses the mechanism of Blackout phenomenon by spacecraft re-entry procedure in the deep space exploration and the absorption attenuation of Plasma Sheath on different frequency electromagnetic wave when the spacecraft is crossing through the different height of atmosphere. The results show that the blackout phenomenon will be inevitable because of the attenuation effects of the Plasma Sheath when the spacecraft re-enters into the atmosphere at a specific height and increase the frequency of electromagnetic wave can effectively reduce the height of the Blackout region, but there hasn’t a complete method to eliminate the Blackout phenomenon.更多还原