Present status of the klystron modulator for the KEK electron-positron injector linac

This paper describes present status of the klystron modulator for SuperKEKB injector linac. The rf system of this linac consists of 60 high-power klystrons, each capable of 50 MW, 4.0 μs pulsed power at a repetition rate of 50 Hz. Each klystron is pulsed by its own PFN-type modulator, containing a thyratron switch tube. Average lifetime of the thyratron is approximately 34,500 hours. A solid-state switch based on an array of thyristors to replace the thyratron is in development to improve the reliability and maintainability of the modulator. A 43 kV, 34 kJ/s PFN-charging power supply has been also developed to realize a compact modulator, which makes space for new equipments in klystron gallery. (author)