A Proposal for a Uniform Magnetic Focusing System to Improve the Sheet Beam Transmission

Sheet electron beam (SEB) has been widely concerned in high-power vacuum electronic devices (VEDs). By enlarging its transverse size, the current of SEB can be further increased under the premise of relatively low current density, thus greatly enhancing the output power. However, the instability of SEB transmission under the focusing of uniform magnetic focusing system (UMFS) limits the further development of SEB-VEDs. In order to solve this problem, a novel and simple method to improve the transmission performance of SEB has been proposed in this article. Based on the conventional UMFS, this method adds two another magnetic blocks with transverse magnetization, and then, the transverse magnetic (TM) field will be generated and will be fully utilized in optimizing the transmission of SEB. Comparative analysis of simulation results shows that under the same strength of the axial magnetic field, using the UMFS with additional TM field (TM-UMFS) to focus the SEB can further increase the electron passing rate by at least 30% compared to the conventional UMFS. The simple structure of TM-UMFS proposed in this article shows the high possibility in the fabricating process and is expected to obtain further development in the high-power SEB-VED industry.