Patterned metallic coating of a ceramic chamber in storage ring bump magnets

To permit the pulsed field of a bump magnet to penetrate the vacuum chamber of a particle storage ring, a section of ceramic chamber is used. A thin metal coating on the inner surface is usually employed to prevent the static charge build-up on the surface of the ceramic chamber, as well as to reduce the coupling impedance. The metal coating, however, can lead to heating of the chamber walls due to eddy current. To avoid such an unwanted effect, a patterned coating is employed. In this paper, we discuss the electrical power and the field distortion due to the eddy current and the effect of various patterned metallic coatings on the motion of a circulating beam. The results are applied to the storage ring of the Pohang Light Source.