Design study and modeling of multi-beam Klystron for Circular Electron Positron Collider

Aimed at energy-saving for the Circular Electron Positron Collider of China, a multi-beam klystron is designed for a higher efficiency than existing commercial klystrons in a continuous-wave UHF band range. The design considerations for every constituent part of the multi-beam klystron are discussed in detail, including modeling of the realistic structures and results of simulations. The electron gun and beam focusing solenoids, which are the fundamental basis for a high average power klystron, are brought out by establishing a good beam transportation rate. The interaction region is designed with the new bunching method using three-dimensional PIC simulation software. The resulted efficiency from the PIC simulation is higher than 80%, considering realistic RF coupling structures in the input and output cavities. The collector is capable of the full beam power dissipation. In the meanwhile, efforts have been taken to avoid reflecting electrons from the collector due to the space-charge depression. The scheme and considerations of the output windows are also introduced.