Laser initiation and early stages of electrical breakdown in charged glasses

A single pulse from a neodymium laser is used to initial electrical breakdown in glasses which accumulate and preserve a space charge induced by a beam of rapid monoenergetic electrons. Laser initiation permits use of high-speed recording apparatus and study of the initial stage of electrical breakdown in the charged glasses. A time delay in electrical breakdown relative to the initiating optical radiation was observed and measured, corresponding to the time of formation of a conductive channel between the region of space-charge localization and the specimen surface. Growth rates of the conductive channel are determined for surface and volume initiation, and possible mechanisms of laser initiation are considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 72–77, July, 1988.     

Surface structure changes in carbon-based materials and polymers under an oxygen-plasma beam

The surface topography of samples of graphite USB-15, pyrolytic carbon PGI, pyrolitic graphite UPV-1, and polyimide PM-1E exposed to accelerated oxygen-plasma beams has been studied by scanning electron microscopy. Surface etching by fast oxygen particles results in the formation of a system of cone/column-like protrusions. As the material mass loss increases, the protrusions increase in size, and the surface topography transforms. Etching of carbon-based materials leads to enrichment of the surface layer with carbon, which is most pronounced in the boron-doped graphite.