High-power RF protection system for CSNS linac

RF breakdown is a common phenomenon in high-power RF devices. It may make irreversible damage to physical structure. Finding a sensitive method to detect the phenomenon and to cut-off RF power as quickly as possible is a good way to prevent the RF breakdown damage. This paper presents a digital and multi-function high-power RF protection system based on VSWR (Voltage Standing Wave Ratio) measurement. The response time of this system is about 700 ns, which includes 300 ns for klystron delay and path delay. The system provides a series of functions that meet the requirements of pulsed and long running accelerators. It also supports real-time graphical display and data recording, which is useful for fault analysis.