30cm离子推力器空心阴极发射体区等离子体特性研究

Plasma Characteristics in Hollow Cathode Emitter Region of 30cm Diameter Ion Thruster

关键词:  离子推力器  空心阴极  发射体区  等离子体特性

Key words:  Ion thruster  Hollow cathode  Emitter region  Plasma characteristics

摘要:

为了获得30cm口径离子推力器20A额定发射电流空心阴极的稳态工作性能参数并验证现有发射体结构设计的合理性，采用数值模拟及有限元分析方法研究了空心阴极发射体区的等离子体特性参数。结果显示:空心阴极发射体区的压强基本在115～150Pa内，并且中间区域的Xe气压强较高；当阴极发射体温度为1570℃时，根据一维热传导方程得到发射体热损为10.26W；发射电流为15A时，电子温度在1.5～1.7eV内，且沿轴线方向靠近阴极顶小孔的电子温度较高，而将15A发射电流作为空心阴极的工作点是较为合适的选择；数值计算得到发射体区平均电子电流密度约为1.3×105A/m2，发射体内表面面积预估为1.5cm2，内径建议在[?]2～2.5mm内，采用该尺寸发射体的空心阴极通过电流发射能力试验证明其最大发射电流在19～20A内，现有发射体尺寸设计满足20A发射电流需求；发射体区中间区域离子电流密度峰值约为8.5×105A/m2，应重点关注发射体中间区域的厚度设计以及离子溅射腐蚀速率。

Abstract:

In order to obtain the 20A emission current hollow cathode steady-state work performance parameters of 30cm diameter ion thruster and verify the structure design of emitter，numerical calculation method and finite element method were used to study plasma characteristics in emitter region of hollow cathode. The obtained results indicate that the pressure at the emitter region is in the range of 115～150 Pa，and xenon pressure in middle region is higher than other place. Finite element method show that emitter's temperature is about 1570℃ and the heat loss estimated value is 10.26W by one-dimensional heat conduction equation，electron temperature is in the range of 1.5～1.7eV and which along axial direction closed to cathode orifice is higher than other region when emission current is 15A，the suggested hollow cathode optimum working emission current is 15A. Average electron current density is about 1.3×105A/m2，internal surface area is estimated 1.5cm2，the suggested inner diameter is in the range of[?]2～2.5mm，and hollow cathode's emitter which adopt the suggested structure design has experimentally verified that the biggest emission current is in the range of 19～20A，which prove the structure design of emitter meets hollow cathode's 20A emission current demand. Ion current density peak value in the middle of emitter region is about 8.5×105A/m2 ，and sputtering erosion effect in this place is the main factor which influence work life of cathode emitter，so the key point of emitter design are thickness and sputtering erosion rate of hollow cathode emitter.