Fundamental processes in vacuum arc deposition

Notwithstanding its multiple technical applications, the fundamental processes of the vacumm arc technique have been insufficiently explored experimentally and theoretical discussions have involved certain contradictions. In particular the main parameters and dimensions of the cathode spots have been under discussion for some time. To answer these current questions, a new system, the high speed framing camera (HSFC), was designed to combine a long distance observation with microscopic resolution and nanosecond time resolution. This camera was used to study the microscopic behaviour of cathode spots in a pulsed high current vacuum arc. The observations described reveal that a single cathode spot, as normally observed by optical means, consists of a number of simultaneously existing microscopic subspots, each with a diameter of about 15 micrometer, 30-50 micrometer apart and a microsecond lifetime