Evolution in time and space of ion and electron properties in the jet of a lowpower Vacuum Arc Thruster

International audienceThe plasma parameters temporal evolution of a 30 W class Vacuum Arc Thruster equipped with a titanium (Ti) cathode is examined in the far field region of the plasma jet. The maximum current intensity reaches 1.8 kA about 8 µs after the dis charge ignition. The change in the electron density, electron temperature and plasma potential during the short high current pulse has been obtained by means of time resolved Langmuir probe measurements. Probes were placed at 3 different locations on the thruster centerline: 20 cm, 25 cm and 30 cm. A time of flight technique has been used to deter mine the mean ion velocity in the plasma jet. We found a higher velocity than what is usually found in the literature for the same cathode material. The electron density peaks at more than 10^18 m−3. The electron temperature is above 4 eV at the beginning of the discharge and then it stabilizes around 0.5 eV. Interestingly, combining all data allows to assess the ion mean electrical charge and its temporal behavior. The mean charge reaches 2+ a few µs after ignition. It decays quickly afterwards and stays un changed around 2 beyond 10 µs. Analysis of all the results support the idea of two distinct plasma dis charge regimes