Can magnetic systems be flexibly switched to suit versatile purposes? This paper introduces a novel design methodology for a current-tunable magnetic focusing system that can switch between Brillouin and immersive flow focusing modes. This magnetic system, composed of cascaded solenoid coils and pole pieces, is applicable in beam optics systems for vacuum tubes, particle accelerators, and free-electron lasers. The design methodology emphasizes optimizing the specific structure of the magnetic system, beginning with the immersive flow focusing mode and electron gun design. Through analysis, the system can transform into the Brillouin bunching mode by adjusting the coil currents without hardware modifications. This innovative method allows for easy adjustment of the beam radius. The authors verify the approach through single-beam and multi-beam optical system demonstrations, highlighting its potential for enhancing electron device performance and offering new possibilities for beam manipulation in various scientific and industrial applications. The current-tunable system offers a versatile solution for researchers and engineers working with electron beams. This adaptable system shows promise for future advancements.
Published in Physics of Plasmas, a leading journal in plasma physics, this paper directly aligns with the journal's focus on fundamental plasma phenomena and applications. The research addresses key challenges in beam optics and magnetic confinement, areas of significant interest to the journal's readership. The adjustable magnetic system contributes to advancements in plasma-based technologies, such as vacuum tubes and free-electron lasers, furthering the journal's mission to disseminate cutting-edge research in plasma physics.