Investigations Of High-Gradient Insulator

It is important to investgate the insulation structure in high voltage vacuum systems, especially the High-Gradient vacuum Insulator(HGI), which is helpful for the compactness and miniaturization of the high voltage insulation system.First, two principal theory of surface flashover, Secondary Electron Emission Avalanche and Electron Triggered Polarity Relaxation, are introduced and the secondary electron emission yield is discussed here; considering the presence of small voids between the insulator and electrodes in reality, several factors such as the insulator material, geometry, the way of attachment to electrodes, the configuration of electrodes, especially in the absence of the applied guide magnetic field and the reflux of electrons, are discussed of their influence on the high voltage hold off capability of insulator by using computer simulation and traditional theoretical calculation; the superiority of 45 degree insulator and the cooperation with grading ring in insulating ability and low flashover probability is also investigated.Second, the basic theory about the HGI is developed. The physical mechanism of excellent performance in insulation has been studied, the preliminary ration estimation to the insulating layer thickness has been made with the single electron theory, and compared with foreign production; qualitative analysis of else geometry parameter has been carried on, and the machining is introduced here. These endeavors have provided theory foundation for designing HGI in reality.In addition, emphasize investigation on the material Kapton has been carried on. The superiority of Kapton has been investigated when being used for high voltage vacuum insulation; the graph of secondary electron emission yield changing along with incident electron energy has been drawn for Kapton and others common insulation by using the software Mathcad. Kapton has better synthesis performance than the others.Finally, some endeavors have been done on searching after the method for optimizing the structure of HGI. Electric field distribution in HGI and electrons orbit near the surface of insulator have been simulated by employing the finite-element software COMSOL Multiphysics 3.2; the structure modal has been predigested and the grid has been optimized based on the primary simulation result, those work puts forward a particular and systemic method for the optimization design of HGI; a design target was set for more than 150kv per cm, Numerical calculation of electron orbits has shown that better performance could be attained when the axial length of a periodically cell equal 0.2mm and the length ratio of insulating layer to metal layer equal 5; the 45 degree insulator which is common used in traditional insulators has been introduced to the design of HGI, and better result has been gotten in computer simulation, the simulation result implies that each layer within the structure behaves independently in the breakdown process, and the total insulation ability is the summation of every insulator cell.