【摘要】 在中国科学院力学研究所Φ800 mm高温低密度激波管上进行电磁波在等离子体中传输机理研究时,低密度和强激波条件下,由于气体解离和电离等非平衡过程,使得激波后2区宽度显著减小;同时由于边界层效应造成激波衰减和接触面加速,使得激波后2区长度进一步减小.这两个效应导致激波管2区实验观测时间减小,2区气体处于非平衡状态,增加了观察数据的不稳定性和数据分析的难度.本文提出在Φ800 mm高温低密度激波管中采用氩气（Ar）和空气（Air）混合气替代纯空气作为激波管实验介质气体.利用Ar不解离和难电离的特性,减小激波前后压缩比,从而增加激波后2区实验时间和气体长度.采用Langmuir静电探针和微波透射诊断技术测量激波后电子密度,同时利用探针测量激波后2区实验时间.结果显示,在Ar+Air混合气实验中,激波波后电子密度可达与纯Air同样的10¹³cm^-3量级.在与纯Air相同的电子密度和碰撞频率条件下,采用95%Ar+5%Air和90%Ar+10%Air两种混合气,激波后2区实验时间和气体长度约为纯Air条件下的5～10倍,其中2区实验时间为300～800μs,2区气体长度1～1.5 m.在Φ800 mm激波管中采用Ar+Air介质气体进行电磁波传输实验,获得了比在纯Air介质中与理论预测更一致的结果.更多还原

【Abstract】 In the study of the transmission mechanism of electromagnetic wave in plasma in Φ800 mm high temperature and low density shock tube in the Institute of Mechanics,CAS,under conditions of low density and strong shock,the experimental time at region 2 behind shock is significantly reduced due to the non-equilibrium processes such as gas dissociation and ionization.At the same time,the boundary layer effect leads to both the attenuation of the shock wave and the acceleration of the contact surface towards the shock front.Therefore,the experimental time at region 2 will be further reduced.These two effects lead to the reduction of the experimental observation time and the non-equilibrium state of test gas at region 2,resulting in the instability of data observation and the difficulty of data analysis.A mixture of argon and air is used to replace the pure air as the experimental test gas in Φ800 mm shock tube.Since argon does not dissociate and is difficult to ionize,the compression ratio of shock is significantly reduced,thereby the test time and the gas length at region 2 are largely increased.The electron densities behind shock were measured with both the Langmuir electrostatic probe and the microwave transmission attenuation method.Meanwhile,the test times at region 2 were measured with the Langmuir probe.The results show that the electron densities in the mixtures of argon and air are in the same order of 10¹³cm^-3 as in the pure air.Under the same electron density and collision frequency conditions,the test times and the gas lengths at region 2 in two mixtures of 90%Ar+10%Air and 95%Ar+5%Air are about 5-10 times than those in the pure air.The test times at region 2 are about 300～800 μs,and the gas lengths at region 2 are about 1-1.5 meter.In electromagnetic wave transmission experiments in Φ800 mm shock tube by using the argon and air mixture as the test gas,the results are more consistent with the theoretical prediction than those in the pure air.更多还原