Ultraviolet radiation damage to dielectrics in spark gaps
Jackson, George L
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An assessment of some of the advantages and disadvantages of various surface analysis techniques applied to the analysis of both the insulators and conductors used in high voltage.-spark gaps is presented. Some of the analysis techniques introduced include Electron Spectroscopy for Chemical Analysis, Auger Electron Spectroscopy, X-ray Fluorescence, and Secondary Ion Mass Spectroscopy. Surface charging makes most analysis techniques incapable of giving useful information about the changes on or near the surface of insulators. Because of the amount of information available from a single ESCA spectrum, such as shifts in binding energies due to the changes in chemical environment, Auger electron peaks due to the relaxation of the atom after photoionization, and the quantitative information, ESCA is the best analysis technique available for the analysis of insulators. Also the problem of surface charging in ESCA is minimal. The analysis of conductors, however, is less complicated because surface charging is no longer a problem. Therefore the use of AES, SIMS, and ESCA can all give some useful information about conductor surfaces. Since there are several damage mechanisms involved in the deterioration of high voltage spark gaps, such as ultraviolet radiation from the arc, heat from the arc, emission of microparticles from the electrodes, and chemically reactive species in gas filled gaps, it is necessary to try to eliminate as many parameters as possible in order to better understand the damage caused by each mechanism. Therefore a vacuum chamber has been built whereby the damage caused by ultraviolet radiation can be separated from the damage caused by other mechanisms. Insulator samples are radiated with ultraviolet radiation and the samples are then analyzed with appropriate surface analysis techniques to determine what, if any, changes the exposure to the radiation caused.