$\infty$ -Shaped (Lemniscatical) Helix Slow-Wave Structure (LH-SWS) for High-Power Traveling-Wave Tubes

This paper introduces a novel ∞-shaped (lemniscatical) helix slow-wave structure (LH-SWS) to increase the achievable output power of the helix traveling wave tube amplifiers. This is realized using multibeam operation. It is shown that higher normalized phase velocity is achieved using the proposed LH-SWS compared to the conventional helix (CH) with the same pitch and radius. Furthermore, lower second harmonic content is obtained. Therefore, the output power could further increase. The experimental results of the LH-SWS cold performance with lemnscatical envelope are presented. The measured return loss of S
₁₁
<; -12 dB is obtained across the operating band of 2-4.8 GHz. Particle-in-cell simulation results show the saturated peak power of 2090 W (33.15 dBW) for the LH-SWS, whereas this