Phase velocity and interaction impedance measurements on slow-wave structures for high-power traveling-wave tubes

In this work some results of phase velocity and interaction impedance measurements made on a ring-bar slow-wave structure for a high-power traveling-wave tube are presented and discussed. The measurements were in range from 7 to 12 GHz. The experimental results obtained were compared to an analytical cold model based on the contra-wound helix theory and to 3D simulations done with a commercial full 3D eigenvalue solver software.