Pure metal vapor plasma source with controlled energy of ions

A new plasma source, the thermionic vacuum arc (TVA), is presented. With regard to a possible coating application, this new source exhibits two important advantages. First, this arc discharge generates a gas- and macroparticle-free metal vapor plasma with a high degree of ionization up to 20% for nearly every metal. Second, this arc offers the possibility to adjust the directed energy of the metal ions produced just by controlling the operating parameters without specific ion accelerating means. The ion acceleration is caused by the slope of the plasma potential along the direction of plasma expansion. Adjustment of the TVA volt-ampere characteristic by variation of the cathode temperature enables control of this acceleration mechanism. For suitable operating conditions, this arc discharge produces ions with directed energies exceeding 200 eV.