Scanning Electron Microscopy


These results question the usual scheme of flashover. They lead to a different interpretation based on classical concepts in solid state physics which can be verified at every step. An ionizing cascade in the bands, rather than a cascade of electron multiplication on the insulating surface, could explain the flashover, the conditioning and the deconditioning of high voltage generators through the building of a surface charge. As in the usual model the positive charge is responsible for the flashover, in this new model the building of this charge is the basis of the conditioning. The ionizing cascade in the bands is initiated by a tunnel injection into the insulator from the soldering metal-insulator junction or by electronic excitation. This interpretation is supported by the analysis of charging phenomena in insulators, the study of localization sites of carriers and by the neutralization mechanisms, charge diffusion or defect annealling. These studies are achieved by scanning electron microscopy and electron spectroscopy.

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