Study of a Terahertz-Band Integrated Dual-Sheet Beam Weak Pole Offset Periodic Cusped Magnetic Focusing Structure

The long-distance and stable transmission of multiple sheet electron beams is one of the most critical challenges hindering the development of integrated multiple sheet electron beam devices. A uniform magnetic focusing structure is an effective scheme to focus multiple sheet electron beams, but it significantly increases the size and weight. To address this issue, this letter proposes a novel weak pole offset periodic cusped magnetic (WPO-PCM) focusing structure with a more compact geometry. In this structure, both the horizontal and vertical sides of each sheet electron beam are primarily confined by a large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${B}_{z}$ </tex-math></inline-formula>, while a small <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${B}_{y}$ </tex-math></inline-formula> is used for fine-tuning. The theoretical analysis, simulation, fabrication, and measurement of this WPO-PCM focusing structure are presented. The measured magnetic fields coincide well with their simulated counterparts, indicating that the structure could provide a peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${B}_{\text {z}}$ </tex-math></inline-formula> of 0.8 T. The effectiveness of the methodology for this WPO-PCM is further verified through the co-simulation of the dual-sheet beam electron optic system and the beam-wave interaction of the entire traveling wave tube.