Electron beam extraction from a broad-beam vacuum-arc metal plasma source

We describe experiments demonstrating the formation of a high current electron beam from a vacuum arc plasma. A preexisting vacuum arc ion source was used, with the extraction voltage reversed in polarity so as to form an electron beam rather than an ion beam; no other changes were required. The beam formed was of energy up to 33 keV, beam current up to 70 A, beam diameter about 10 cm, pulse width 500 /spl mu/s, and energy density up to 25 J/cm/sup 2/. This kind of source can be used for material surface modification.