An Approach to Electron Optical System Design for Dual-Pencil-Beam Traveling Wave Tubes

Achieving a high compression factor and stable long-distance transmission of electron beams presents significant challenges for developing multibeam devices, especially those that employ multiple pencil beams. Uniform magnetic (UM) field focusing structures, although viable, are often limited by their bulkiness and weight. This article presents a novel approach for designing dual-beam electron guns with significantly enhanced electron beam compression. The proposed methodology, implemented in W-band overmoded traveling wave tubes (TWTs), demonstrates exceptional performance, achieving a remarkable beam compression factor of 57 at a total current of 0.2 A ($2\times 0.1$A). In addition, a compact periodic cusped magnetic structure with a notch is proposed to effectively confine dual pencil beams. Co-simulation results of the electron optical system demonstrate a transmission efficiency of 99.2% over a distance of 100 mm.