Sheet Beam Electron Optical System using Periodic Cusped Magnets for Terahertz Applications

The success of terahertz vacuum electron devices requires efficient generation and transport of high current density electron beams. An electron optical system consisting of a sheet electron beam gun and periodic cusped magnets is proposed to efficiently generate and transport a sheet electron beam for terahertz applications. The system consists of an electron gun and dual-layer magnet blocks aligned with pole pieces. This design not only produces a higher magnetic field in the axial direction but also allows for easier adjustment of the magnetic field in the transverse direction. This focusing system is used to transport a 21.7 kV, 50 mA sheet electron beam with a cross-section of 0.24 mm × 0.08 mm through a 50 mm long tunnel with dimensions of 0.32 mm × 0.12 mm. The current density of the beam exceeds 260 Acm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup>. The focusing system is designed to produce an axial magnetic field B<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</inf> of 0.2 T. CST Particle Studio is used to model the sheet electron beam gun and the periodic cusped magnet system. The obtained results show a beam transmission efficiency of 100%.