Traveling Poles Elimination Scheme and Calculations of External Quality Factors of Homs in Sc Cavities

The main scope of this work is the automation of the extraction procedure of the external quality factors Qext of Higher Order Modes (HOMs) in Superconducting (SC) radio frequency (RF) cavities. The HOMs are generated by charged particle beams traveling through a SC cavity at the speed of light (β ≈ 1). The HOMs decay very slowly, depending on localization inside the structure and cell-to-cell coupling, and may influence succeeding charged particle bunches. Thus it is important, at the SC cavity design optimization stage, to calculate the Qext of HOMs. Traveling Poles Elimination (TPE) scheme was used to automatically extractQext from the transmission spectra and careful eigenmode analysis of the SC cavity was performed to confirm TPE results. The eigenmode analysis also delivers important information about band structure, cell-to-cell coupling and allows rapid identification of modes that could interact with the charged particle bunches.