Explosive plasma formation on surfaces caused by unipolar arcing

Summary form only given. Using a laser-produced plasma it has been demonstrated that unipolar arcs ignite and burn on a nanosecond time scale without any external electric field being applied. Micron-sized arcs burn between the plasma and a metal surface driven by local variations of the sheath potential. Locally, the surface forms both electron-emitting cathode spots and, surrounding the spot, electron-receiving anode areas. Similar unipolar arc craters have been observed on the cathode surface of a pulsed vacuum diode. Experimental results show that cathode spots are formed by unipolar arcing. The localized buildup of plasma above an electron-emitting spot naturally leads to an electric field distribution which drives the unipolar arc. The high current density of a unipolar arc provides explosive plasma formation