2017/08/31 by Farshad Yazdi, Mohamed A. K. Othman, Mehdi Veysi +2
Engineering · Physics and Astronomy · #Amplifier #Coalescence (physics) #Degeneracy (biology) #Dispersion (optics) #Electric power transmission #Group velocity #Gyrotron and Vacuum Electronics Research #Modal #Modal analysis #Orbital Angular Momentum in Optics #Particle Accelerators and Free-Electron Lasers #Synchronization (alternating current) #Traveling-wave tube #physics.app-ph #physics.plasm-ph
paper · pdf · doi:10.1109/tps.2017.2781245
15 pages, 11 figures
openalex created_date 2017/09/15 · arxiv created 2017/11/22 · openalex publication_date 2017/12/27 · arxiv updated 2018/02/14 · openalex updated_date 2026/08/05
Engineering of the eigenmode dispersion of slow wave structures (SWSs) to achieve desired modal characteristics is an effective approach to enhance the performance of high-power traveling wave tube (TWT) amplifiers or oscillators. We investigate here for the first time a new synchronization regime in TWTs based on SWSs operating near a third-order degeneracy condition in their dispersion. This special three-eigenmode synchronization is associated with a stationary inflection point (SIP) that is manifested by the coalescence of three Floquet-Bloch eigenmodes in the SWS. We demonstrate the special features of “cold” (without electron beam) periodic SWSs with SIP modeled as coupled transmission lines and investigate resonances of SWSs of finite length. We also show that by tuning parameters of a periodic SWS, one can achieve an SIP with nearly ideal flat dispersion relationship with zero group velocity or a slightly slanted one with a very small (positive or negative) group velocity leading to different operating schemes. The SIP structure when synchronized with an electron beam has potential benefits for amplification which include: 1) gain enhancement; 2) gain-bandwidth product improvement; and 3) higher power efficiency, when compared to conventional Pierce-like TWTs. The proposed theory paves the way for a new approach for potential improvements in gain, power efficiency, and gain-bandwidth product in high-power microwave amplifiers.