Extreme hydrogen plasma densities achieved in a linear plasma generator

A magnetized hydrogen plasma beam was generated with a cascaded arc, expanding in a vacuum vessel at an axial magnetic field of up to 1.6T. Its characteristics were measured at a distance of 4cm from the nozzle: up to a 2cm beam diameter, 7.5×1020m−3 electron density, ∼2eV electron and ion temperatures, and 3.5km∕s axial plasma velocity. This gives a 2.6×1024H+m−2s−1 peak ion flux density, which is unprecedented in linear plasma generators. The high efficiency of the source is obtained by the combined action of the magnetic field and an optimized nozzle geometry. This is interpreted as a cross-field return current that leads to power dissipation in the beam just outside the source.