Plasma accelerator with closed electron drift

A closed electron drift plasma accelerator comprising:

• a main annular channel having an axis for ionization and acceleration that is open at its downstream end and defined by parts made of insulting material;
• a hollow cathode disposed outside the main annular channel adjacent to the downstream end thereof;
• an annular anode concentric with the main annular channel and disposed at a distance from the open downstream end;
• first and second ionizable gas feed means associated respectively with the hollow cathode and with the annular anode;
• a magnetic circuit for creating a magnetic field in the main annular channel;
• an annular buffer chamber whose dimension in the radial direction is larger than that of the main annular channel and which extends upstream therefrom beyond a zone in which the annular anode is placed, the second ionizable gas feed means opens out into the annular buffer chamber upstream from the annular anode via an annular ionizable gas manifold in a zone that is distinct from the zone carrying the annular anode, and further comprising a first, second and third magnetic field creation means together with internal and external plane radial pole pieces that are disposed level with the downstream end on either side of the main annular channel and that are connected to each other by a central core, a yoke, and a peripheral magnetic circuit disposed axially outside the main annular channel and the annular buffer chamber;
• and
• the accelerator being characterized in that the means for creating a magnetic field in the main annular channel are adapted to produce an essentially radial magnetic field in said main annular channel, the field having a gradient with maximum induction at the downstream end of said main annular channel, the field lines being essentially parallel to the plane radial pole pieces perpendicular to the axis of the accelerator at the downstream end of the main annular channel, and minimum induction in a transition zone situated in the vicinity of the annular anode between the buffer chamber and the main annular channel so as to enhance ionization of the ionizable gas, and in that the distinct magnetic field creation means comprise first magnetic field creation means disposed around and outside the main annular channel in the vicinity of the downstream end thereof, second magnetic field creation means disposed around the central core in a zone facing the annular anode and extending partially to face the buffer chamber, and third magnetic field creation means disposed around the central core between the second magnetic field creation means and the downstream end of the main annular channel.