RESEARCH AND DEVELOPMENT OF LOW-POWER HALL THRUSTERS WITH CIRCULAR-CROSS-SECTIONAL DISCHARGE CHAMBER, AND ITS INNER PHYSICAL PROCESSES

利用TCHT-3A和TCHT-3B系列霍尔推力器研究了磁场位形对圆形放电室霍尔推力器性能的影响。结果表明，通过调整径向磁感应强度峰值位置，可以提高推力性能。随着径向磁通密度峰值位置向下游移动，离子向壁面的损失和流向阳极的电子流减小。然而，由于中性扩散，推进剂利用率也降低。对TCHT-2型圆形放电室霍尔推力器进行了羽流测量。离子流密度测量表明，羽流发散角对推进剂质量流量不敏感，推进剂利用率随质量流量的减小而降低。使用RPA的离子能量测量表明，在低质量流率的加速效率下降。由双探针测量的放电室内部电子温度和等离子体电势分布，确定了电离/加速区的位置，在该区域存在强径向磁场，小型霍尔推力器TCHT-3A的推力性能随尺寸减小而下降，离子损失增大。通过在下游区域施加强径向磁场，小型霍尔推力器TCHT-3B在低功率水平下获得了比TCHT-3A更高的推力性能。它在80- 170 W的功率范围内具有效率（26-39%）。

Effects of magnetic field configuration in Hall thrusters with circular cross-sectional discharge chambers were examined using TCHT-3A and TCHT-3B series Hall thrusters. The results showed that by adjusting the position of peak of radial magnetic flux density the thrust performance was improved. As the position of peak of radial magnetic flux density shifts downstream, the ion loss to the wall and electron current to the anode decrease. However, propellant utilization also decreases because of neutral diffusion. Hence, the optimal position of peak exists.Plume measurements of Hall thruster with circular cross-sectional discharge chamber, named TCHT-2, were carried out. Ion current density measurement showed that the plume divergent angle was not sensitive to propellant mass flow rate and that the propellant utilization decreased as the mass flow rate decreased. Ion energy measurement using RPA indicated that the efficiency of acceleration decreased at low mass flow rate. From the electron temperature and plasma potential distribution inside the discharge chamber obtained by a double probe, the ionization/acceleration region is located at which strong radial magnetic field exists.The miniature Hall thruster TCHT-3A showed that thrust performance declined with scaling down by increase of ion loss. By applying strong radial magnetic field at the downstream region, miniature Hall thruster TCHT-3B achieved higher thrust performance than TCHT-3A did at low power level. It has efficiency (26-39%) in the power range 80-170W.