【作者】 施晨毅；

【导师】 王振国；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2007， 博士

【摘要】 本文针对裸Faraday探针不能准确测量等离子体束流密度分布的情况进行了分析,进而优化设计出校准型Faraday探针。由于定向羽流离子与背景气体中的随机低速中性粒子发生了电荷交换碰撞,产生了低能离子。这些低能离子会影响Faraday探针测量羽流中离子束流密度分布的真实性。因此有必要设计校准型Faraday探针,来过滤电荷交换碰撞产生的低能离子。使得无论设备以什么样的抽速工作,都能用校准型Faraday探针,得到霍尔推力器发出的等离子体羽流中真实的离子流密度分布。本着提高Faraday探针测试精度的设计准则,首先,全面分析了Faraday探针工作的基本工作原理、物理过程和相关工作机制,并提出了一些必要的假设来简化物理过程,以便于理论公式的推导。在此基础上进行了与校准探针基本结构设计有关的比例因子公式推导。接着,按照理论上推导的比例因子公式,确定校准Faraday探针的结构和尺寸。选择校准探针中裸探针和校准筒的材料,进行加工、安装。然后接好测试电路,在一个真空度范围为1.7-2.3×10^-3Pa的真空舱里,用一个裸探针和一个校准探针来进行试验。选定801所研制的霍尔推力器工程样机SPT-70进行放电,该发动机功率约为0.6KW,放电时阴极流率为2sccm,阳极流率为16-20sccm。在加偏置电压和不加偏置电压的情况下,对两个探针做性能评估。通过分析试验结果,不仅验证了校准探针预期的性能,即校准型Faraday探针可以过滤电荷交换碰撞产生的低能离子,测得较为真实的离子束流密度分布;还发现了在校准探针的校准筒内探针与等离子体发生了强烈的相互作用,本文从校准筒内部压力和电场等方面进行了分析。本文最后对试验中发现的问题,提出了继续研究的手段和方法,以期能够了解探针内部情况,对探针结构和材料进一步进行优化设计,使校准型Faraday探针可以达到准确测量霍尔推力器羽流的成熟水平。更多还原

【Abstract】 The reason why a nude Faraday probe can’ t truly measure the ion current density in Hall thruster is discussed and the design of a collimated Faraday probe is reported in this paper.The resonant charge exchange（CEX） collisions of directed plume ions with the random background population of neutrals will bring low energy ion,which will be recorded as ion current by Faraday probe.A collimated probe design is attractive because it offers the possibility of obtaining the true ion current density profile regardless of the facility pumping speed.For improving the measuring precision of Faraday probe,firstly the paper analyses the basic principle and the physics process of plasma plume diagnose with it.Then it provides some assumptions to simplify the physics processes.Based on these assumptions,the expressions for the scale factor are derived.The structure and the size of the Faraday probe is decided by these theoretical expressions.Also the materials of the collector inside the collimated probe and the collimated tube are chosen.After all, the processing and fixing for the accessories of the collimated probe were be finished in 801 Institute.Experiments were conducted using a traditional nude Faraday probe and a collimated probe.The probes are evaluated using a 660W Hall thruster（SPT-70,which is made in 801 Institute.） in a facility capable of maintaining background pressures of 1.7-2.3×10^-2 Pa for cathode flow rates of 2sccm and anode flow rates of 16-20sccm. After preparing testing circuit,measurements were made for each position with the two probes either floating or biased to the collectors to evaluate them.Detailed examination of the results has shown that the collimator can act primarily as a filter for low energy ions introduced in the plume by charge exchange collisions and the collimated probe is interacting strongly with the plasma inside the collimator. The pressure and electric fields inside the collimator are considered in this paper.Finally other investigations may interrogate the probe interior itself by measuring the internal pressure and plasma properties with ionization gauges and electrostatic probes.Numerical modeling of the probe is also being considered,as are alternative designs to the probe geometry and materials.Further study is required to bring the collimated Faraday probe to a maturity level sufficient for use in evaluating Hall thruster plumes.更多还原