A plasma thruster includes extraction of a stream of positive ions. The plasma thruster includes a single ionization stage; injecting ionizable gas for said ionization stage comprising injecting a first gas and an electronegative second gas; creating an RF electric field to cause the gases to ionize in the ionization stage creating a first zone called the hot zone, in the ionization stage; the first gas being distributed in the hot first zone, the second gas being distributed in a second zone less hot than said first zone; extracting a stream of negative ions and a stream of positive ions, these being both connected to the ionization stage; and the extraction of a stream of positive ions and the extraction of a stream of negative ions, ensuring that the thruster is electrically neutral.