OBSERVATIONS OF ELECTRIC-ARC CATHODE REGION

CCD camera images of the near-cathode region of an electric are, worki ng at atmospheric pressure in argon, permitted observation of some int eresting phenomena that take place in this region, e.g. a 'dark zone' in the cathode sheath region, low-frequency (f < 0.1 Hz) fluctuations of discharge parameters and emitted light, the existence of several ho t spots on the cathode surface, different kinds of movements of the ar e spot on the cathode surface, and modification of the cathode surface structure.