Radio-frequency design and commissioning of a flexible waveguide for high-vacuum S-band applications

Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system assemblies.However,the peak powers of these waveguides have been limited to several megawatts in non-vacuum environments.Herein,a novel flexible waveguide was developed for the S-band (2856 MHz) with the aim of facilitating the interconnection of two hard waveguides.
Methods The flexible waveguide was composed of brass,and its surface was plated with oxygen-free high-conductivity copper for brazing with stainless steel flanges in a vacuum furnace.By connecting the stainless steel flanges together,it can be applied to a high-vacuum environment.
Results The prototype exhibited good measurement results in low-power microwave tests;the results of a 72-h vacuum leak test showed satisfactory vacuum performance as well,and no obvious surface collapse was observed.High-power microwave commissioning was conducted between June and July 2019;the waveguide showed a maximum average power of approximately 2.7 kW.
Conclusion Unfortunately,the prototype was damaged after reaching that power level,which indicates the need for further optimization of the fabrication process.From our experiment,it is clear that the flexible waveguide cannot be used in large accelerators because of its average power limit.