An investigation of the development of new emission center within the cathode spot of vacuum arc

In present work the development of the new emission center (fragment) and the death of a fragment within the vacuum arc cathode spot on a tungsten cathode at a current about 10 A were investigated with temporal resolution of 2.5 nsec and spatial resolution of 5-10 microns. The current through the separate fragment of cathode spot and the current of the rest part of cathode spot were registered simultaneously and separately by dividing the cathode in two electrically insulated parts closely located one near the other. The image of the cathode spot was taken with streak-camera, and the camera sweep was synchronized with the cathode current waveforms. It was found that: - the appearance and disappearance of the fragment is stepwise in character with rise and fall time of 1-2 nsec; - the most probable value of current step is close to the threshold current; - at the complete disappearance of the current through the fragment the luminosity disappears at the same moment (within accuracy of 1-2 nsec).