关键词: 离子推力器；空心阴极； 小孔区； 等离子体特性

Abstract: In order to obtain 30cm diameter ion thruster's 20A emission current hollow cathode's plasma characteristics in orifice region and verify the current emission ability in existence structure design of orifice，numerical calculation method and finite element method were used to study plasma characteristics in orifice region of hollow cathode. The obtained results indicate that neutral density is in range of 4×1021/m3～6×1021/m3，which is well-distributed and neutral density is lower closed to the exit of orifice. When emitter temperature is 1800K and the average radial electron temperature is about 2.66eV by plasma diffusion 0-D model and which is higher closed to exit of orifice，and electron temperature is increasing about 1～2eV from orifice entrance to exit. Orifice region plasma density is in the range of 1×1021～1.4×1021/m3 by using ion continuity equations and plasma density decreasing obviously closed to exit of orifice. Electron current is about 7.2A closed to the entrance of orifice region and which is 11.6A closed to exit by using electron continuity equations，the calculation results are in well agreement with the experimental results，electron current gain coefficient is about 60% in orifice region. The highest ion current density is about 6.16×106 A/m2 which is about 0.5mm closed to the entrance. Through theory analysis，the exit of hollow cathode orifice is badly erosion meanwhile the diameter of orifice is increasing by erosion effect. The orifice diameter erosion rate is fall to negligible levels once orifice opened sufficiently，theory predict results of erosion tendency is in agreement with LHC-5 hollow cathode life test results.

Key words: Ion thruster；Hollow cathode；Orifice region；Plasma characteristics