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Alumina ceramics is widely used as an insulating material for high voltage devices, because of low outgassing, hardness, low dielectric loss and high bulk breakdown voltage. However, there is serious problem to solve that the flashover voltage along the surface in vacuum is lower than that of a vacuum gap at the same length between electrodes. Many intensive researches have been carried out to improve...
The CVD system by 27.12 MHz ICP discharge and CO2 laser was developed to investigate the advanced ceramics, particularly diamond grain or film. Our system is unique, whose RF antenna coil was installed inside of chamber. In our experiment, it was measured that the plasma characteristics which were Te=3.0 eV and ne=8.2times109 cm-3. Any impurity was not observed in the present condition, judging from...
Secondary electron emission (SEE) coefficients of alumina ceramics with three different surface finishes have been measured using a scanning electron microscope with a single-pulse electron beam (100 pA, 1 ms). SEE coefficients of those aluminas with annealing process became lower after mechanical grinding operations even though its average roughness was almost same as those of as-sintered ones. SEE...
The breakdown of alumina rf windows is mostly caused by multipactor, as well as by material defects and contamination. Since multipator induces localized surface heating, leading to surface melting, it is necessary to observe secondary electron emission (SEE) coefficients of alumina ceramics under high temperature conditions. The SEE coefficients of commercial alumina ceramics and sapphire were measured...
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