为了对30 cm口径离子推力器的磁场设计提出合理建议，研究了四极磁场结构下，不同尺寸的磁极宽度和磁极间距对磁极表面磁场强度和放电室电子约束长度的影响，并利用Maxwell-3D磁场分析软件得到柱段和锥段永磁体分别呈30°，60°和90°夹角时的放电室磁场强度分布，根据不同磁场强度计算了电子温度、离子密度以及电离率等推力器放电参数。结果表明，当推力器放电电压为30 V时，磁极长度设计为0.008 m且磁极间距取为0.12 m，电子约束路径大约为50 m; 柱段和锥段永磁体分别呈30°，60°和90°夹角时，放电室磁场等势线基本在0.002~0.005 T之间; 永磁体夹角为60°时磁场分布和磁空区相比30°和90°夹角更为合理，此时的电子温度约在2~6 eV，等离子体密度约在4×1017~8×1017 m-3，电子碰撞频率比率约在0.2~1.8范围内。

In order to make reasonable proposals on the magnetic design of 30 cm diameter ion thruster, the effects of magnet diameter and the spacing on the magnet strength and the confinement length of the discharge electron have been studied. By utilizing Maxwell-3D software, the magnetic field distribution was obtained with the permanent magnet on the cylindrical section oriented at 30°, 60° and 90° to that on the conical section. According to different field calculated, several discharge parameters, such as electron temperature, ion density and ionization efficiency were calculated. The results indicate that when discharge voltage of 30 V，magnet pole length of 0.008 m and magnet spacing of 0.12 m are set, the confinement length of the primary is in the order of 50 m. When the angles between the permanent magnet on the cylindrical section and that on the conical section are 30°, 60° and 90°, the magnetic field contour inside the discharge chamber is in the range of 0.002-0.005 T. With the angle being 60°, the magnetic field and filed free region are more reasonable compared to the cases of 30° and 90°, when the electron temperature is about 2-6 eV, the plasma density is about (4-8)×1017/m3and the collisional frequency rate of electron is in the range of 0.2-1.8.