离子源内电子回旋共振等离子体诊断与分析

Diagnosis of Electron Cyclotron Resonance Plasma Inside Ion Source

电子回旋共振离子推力器（ECRIT）离子源的内部磁场会干扰离子源内等离子体诊断,选择合理的诊断方法需要分析离子源特性,了解磁场对诊断结果的影响。为此,采用朗缪尔（Langmuir）探针诊断了离子源的等离子体信息,根据朗缪尔探针理论得到电子温度、电子数密度、离子数密度,根据Druyvesteyn方法得到电子温度、电子数密度。结合实验现象,对比了不同方法所得诊断参数差异,分析了诊断结果的准确性。诊断结果表明：诊断位置到轴线的径向距离〉10 mm后,离子数密度由3.0×1017 m-3增至1.8×1018 m-3,符合离子源的放电原理和实际的放电形貌;不同处理方法所得电子温度、电子数密度接近,电子温度诊断值范围是4~20 e V,电子数密度诊断值范围是（2.0~9.0）×1016 m-3。离子数密度诊断结果较电子数密度诊断结果准确;电子温度较低时,使用积分得到的电子温度更准确;平行于探针的磁场会显著降低诊断得到的电子数密度,探针收集面垂直于磁场可减弱磁场干扰。

The magnetic field inside the electron cyclotron resonance ion thruster （ECRIT） affects the diagnosed para- meters of the inside plasma. It is necessary to analyze the effects of magnetic field on the diagnosed results so that proper diagnostics procedure can be chosen. We used Langrnuir probe to measure the plasma in ECRIT and obtained electron temperature, electron number density, and ion number density based on Langmuir theory as well as electron temperature and electron number density based on Druyvesteyn procedure. The results are compared while taking experimental phe- nomena into consideration and their accuracy is discussed. It is observed that the diagnosed ion density increases rapidly from 3.0~ 1017 m-3 to 1.8 ~ 1018 m-3 when radial distance from the axis is larger than 10 mm, which agrees well with expe- rimental results. The diagnosed electron temperature and number density obtained using the two methods are similar; the former ranges from 4 eV to 20 eV and the latter ranges from 2.0 xl016 m-3 to 9.0x1016 m-3. It is concluded that the ion number density diagnosis is more accurate than that of electron number density. At a relatively low temperature, using the Druyvesteyn procedure would be more reliable to diagnosis electron temperature. A magnetic field parallel to the probe tip will significantly reduce the obtained electron density, so ensuring the probe to be perpendicular to magnetic field helps reduce the interference.