Two-dimensional observation of copper vapor in vacuum arcs by laser-induced fluorescence

The density distribution and the velocity of copper neutral atoms emitted from a single cathode spot in 40 A vacuum arc were measured by the two-dimensional laser-induced fluorescence method with a CCD camera. The copper atoms spread widely over the cathode and the density of the copper atoms reached 5/spl times/10/sup 13//cm/sup 3/. The velocity of copper atoms emitted from the cathode spot was about 10 km/sec.