Abstract
This paper describes the charging phenomena of a cylindrical insulator made of PMMA, PTFE or Al2O3 under ramped, and stepped DC voltage application. The principal content of the paper is concerning the influence of surface roughness on the charging for various insulating spacers. By using an electrostatic probe located on the cathode, we have conducted the real-time observation of the electric field due to the surface charge. It has been found that the surface roughness decisively affects the charging, which is more pronounced for more highly polished insulators. Further more, the time dalay of the charging decreases with the polished insulators. These results show the importance of surface treatments for insulating spacers in vacuum.
