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A composite micro-textured surface structure is proposed and demonstrated to enhance the surface flashover strength of polymer insulators used in vacuum. The structure is fabricated in two stages, with periodic triangular grooves of approximately 210 μm in width formed in the first stage and micro-holes of approximately 2 μm coated on the inner surface of grooves in the second. The aim is to exploit the synergistic effects between the grooves and micro-holes to suppress the secondary electron yield to obtain a better flashover performance. To acquire insulators with the composite micro-textured surface, the CO2 laser processing technique is applied to treat the surface of the PMMA insulators. The test results show that the flashover voltages of the insulators with the two-stage fabricated structure increase by 150% compared with the untreated samples in the best state. Compared with the traditional macro-groove structures on insulators, the proposed composite micro-textured insulators exhibit a better surface flashover performance. [ABSTRACT FROM AUTHOR]

Molecule self-assembly on the surface of alumina ceramic and its influence on the surface flashover characteristics of the alumina ceramic insulators were studied in this paper. First, octadecyltrichlorosilane was assembled on the surface of alumina ceramic insulators in the toluene solution. Then, 393 K thermal treatment of 2 h was conducted on the specimens to promote the growth of the molecule membrane. Quality detection of the prepared molecule membrane by Energy Dispersive x-ray Analysis and water contact angle test showed that the molecules were linked to the alumina surface and the arrangement of the molecules on the surface was regular and tight. Gas release characteristic suggested that the formation of the molecule membrane made the gas release rate of the treated alumina decrease. The flashover voltage test on the home-made, short-pulsed, high-voltage vacuum platform indicated that the flashover voltages of the treated insulators increased by over 200% compared with the original alumina insulators. These results indicated that a layer of regular molecule membrane was formed on the surface of alumina through molecule self-assembly, which could improve the surface voltage withstand strength of the treated insulators. [ABSTRACT FROM AUTHOR]

The fabrication method of grooves on the surface of alumina and their influence on the surface flashover characteristics of the alumina insulator were studied in this paper. To prepare grooves with a regular surface structure, the UV laser was applied to carve grooves on the surface of alumina ceramic, and dilute hydrochloric acid was used to corrode and remove the residual materials produced in the laser carving process. By adjusting the laser parameters, periodic grooves were prepared on the surface of a cylindrical alumina insulator with a groove depth of 60 µm and a groove width of approximately 50 µm on the laser spinning carving platform. Then, alumina insulators with different periods were prepared, and their vacuum surface flashover voltages were tested on a short pulsed high-voltage test platform. The test results indicated that the flashover voltages of the alumina insulators with laser carved periodic grooves were increased over 200%, and the improvement did not change much with the groove periods. A further study of the groove parameters showed that several grooves fabricated on the cathode end of the insulators were able to improve the flashover voltage of the alumina insulator to the voltage-withstand level of the fully grooved insulators. [ABSTRACT FROM AUTHOR]

Explosive emission cathodes are widely used in high power microwave generation. Conventional metallic cathodes have the disadvantages of bad emission uniformity and short lifetime. In order to improve the emission property of metallic cathodes, a new metal-dielectric cathode is fabricated with the plasma spraying technology. Unlike previous metal-dielectric cathodes, our metaldielectric cathode adopts a ferroelectric ceramic which possesses a large permittivity. The results of lifetime experiments show the metal-dielectric cathode presents just slight performance deterioration within 2.5-105 pulses and thus has a much longer lifetime than the normal copper cathode. The morphology observation demonstrates that the good emission property of the metal-dielectric cathode may benefit from the appearance of irregularities on the dielectric surface, which will have large microscopic field enhancement factors with the help of large permittivity of the ferroelectric material. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]