The influence of external magnetic field on the plume of vacuum arc thruster

The vacuum arc thruster (VAT) is considered to be a potential micro-thruster because of its simple structure and high specific impulse. The plume downstream from the cathode spot region of a co-axial type thruster with external magnetic field is analyzed by numerical simulation. Plasma velocity, temperature and density are used to represent the influence of the cathode spot region. When the magnetic field is applied, the plume is significantly affected even at the intensity of 0.03 T. Most ions move around the magnetic induction line, forming a concentrated beam. The beam expansion angle and the ion backflow are controlled therefore. The ion beam total velocity increment is about 20% in the plume while the beam direction is determined significantly by the cathode spot position and the external magnetic field. The deflection angle of the magnetic induction line in the near-field region will bring axial velocity loss. The magnetic field intensity affects little on the ion beam velocity increment while the influence of the initial plasma density change caused by the magnetic field cannot be ignored. Ground experiment data show a large increment of ion beam velocity between the conditions with and without the magnetic field (0.03 T and 0 T), but nearly no obvious variation from 0 to 15 cm downstream of the thruster in the former condition.