Intense-Mode Vacuum Arc Characterization by Using 2-D Electron and Vapor Density Image

Shack-Hartmann type laser wavefront sensors were applied to simultaneous single-shot imaging of 2-D electron and copper-vapor density distributions over intense-mode vacuum arc discharges with a pulsed current waveform of 800 A in peak and 24 μs in damping time constant. A parametric analysis of the ion current based on our experimental results suggested that the intense-mode arcs included highly energetic ions moving from cathodes to anodes with a high velocity of 10
⁴
m/s and their proportion was larger than or comparable to slow ions with 10
^-1
m/s drifted from anodes to cathodes by the electric fields. Furthermore, hydrodynamic calculation demonstrated that the copper vapor in the vacuum plasmas dissipated almost instantaneously in a time scale of ~1 μs and it was not residual metal medium but fresh one continuously supplied from the electrodes.