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Description
High-power microwave (HPM) systems are essential for accelerating charged particles in large-scale accelerators, where precise control of microwave parameters—such as amplitude, phase, and pulse shape—is critical to achieving high beam quality. Among the key HPM components, pulse compressors, variable attenuators, phase shifters, and absorbing loads play pivotal roles in beam dynamics optimization and system reliability. Since 2017, the Institute of High Energy Physics (IHEP) has developed spherical cavity pulse compressors; a 2856 MHz prototype underwent rigorous high-power conditioning and achieved a peak output power exceeding 400 MW in 2024. This device is now operational in the Particle Wake-Field Acceleration (PWFA) project. Complementing this, compact variable attenuators, phase shifters, power dividers, and combiners—sharing a common waveguide-based mechanical design—have been successfully developed for L-band (1–2 GHz), S-band (2–4 GHz), and C-band (4–8 GHz) applications. Leveraging these components, a fast-switching RF power backup system has been implemented, enabling real-time redistribution of microwave power between two adjacent klystrons within several minutes—a capability vital for maintaining stable accelerator operation during unexpected klystron degradation or failure. Concurrently, an energy-recovering load is under development, integrating a tunable coupling mechanism with an efficient RF-to-DC conversion stage. Recent advances in fourth-generation gallium nitride (GaN) high-electron-mobility transistors (HEMTs)—notably their superior power density, thermal robustness, and operation up to X-band frequencies—have enabled the feasibility of high-efficiency RF rectification schemes, paving the way for next-generation energy-recycling RF systems.
