CEPC high power and high efficiency klystrons

Following the discovery of the Higgs boson at the Large Hadron Collider (LHC), Chinese scientists proposed the “Great Collider” initiative, a next-generation multinational particle accelerator research facility encompassing both a circular electron-positron collider (CEPC) and a super proton-proton collider (SPPC). The CEPC synchrotron radiation power is projected to reach 60 MW, necessitating highly efficient radiofrequency (RF) systems to minimize energy costs. The Institute of High Energy Physics (IHEP) has developed an 800kW continuous wave (CW) klystron with a target efficiency of 80%. Prototype testing achieved 803 kW (CW) at 78.5% efficiency under a 113 kV gun voltage. Simultaneously, a pulsed 5712 MHz klystron delivering 80 MW of peak power has been designed to drive four accelerating structures in the CEPC Linac, which will accelerate electron and positron beams to 30 GeV. This paper details the design, simulation, and testing of both klystrons, covering electron gun optimization, RF section design, magnetic focusing systems, collector thermal management, and high-power validation. These advancements support the CEPC-SPPC project and align with global efforts for next-generation colliders like the ILC, CLIC, and FCC.