Abstract: The operation mode of the thruster is divided into high current mode and low current mode to study the low frequency oscillation characteristics in a cusped field thruster. The characteristics of low frequency oscillation were studied by changing working parameters and magnetic field configuration. The effects of the outer circuit on the low frequency oscillation were also studied. Results show that the operation mode of the cusped field thruster converted from high current mode into low current mode with the increase of discharge voltage under the condition of high mass flow. In comparison, the discharge current in high current mode has the characteristics of high amplitude and low frequency with vague plume. With the increasing of discharge voltage, the current oscillation amplitude increases and then decreases, while oscillation frequency increases along with the discharge voltage. However, the discharge current in low current mode has the characteristics of low amplitude and high frequency, and plume has two obvious bright lines. Current oscillation amplitude and  frequency increases with the increasing of discharge voltage. With the increasing of mass flow rate, discharge current oscillation amplitude and frequency tend to increase in different working conditions. Meanwhile, the resistance and inductance in the outer circuit can suppress low frequency oscillation, but the effect of capacitance on low  frequency  oscillation is not obvious.

Key words: cusped field thruster, low frequency oscillation, high current mode, low current mode, working parameters, outer circuit