Low-Secondary Electron Yield of Ferrromagnetic Materials and Magnetized Surfaces

Low-secondary emission materials are required to avoid multipactor effect in large particle accelerators and communications. We are presenting direct measurements of the secondary electron emission yield (SEY) for several magnetic materials like permanent ferrite magnets and soft ferrites of different composition at energies of primary electrons from 5 to 1000 eV. In order to minimize the impact of the surface charging, the primary electron beam had a short pulse of length 270 ns. This paper discusses a method of developing a secondary-electron-suppressing highly textured ferrite surface with low SEY by depositing a layer of ferrite particles onto a metallic substrate. As a remarkable fact it has been found that particulated ferrites have maximum SEY values lower than unity up to 1000eV. In addition, the influence of external magnetic field on LHC main power coupler performance is also studied.