RF reference distribution using fibre-optic links for KEKB accelerator

The KEKB accelerator is a 3 km circumference double-ring collider which has six RF accelerating stations and will have two station for crab cavities. Each station is 800 in from the other. A stable RF phase reference is necessary for stable RF cavity operation. Coaxial cables with phase locked loops are used for the present system. A more stable RF phase reference is required for the crab cavity luminosity improvement project. An RF phase distribution system using single-mode fiberoptic links has been tested for improvement of the phase stability. The system uses a phase stabilized optical fiber and a phase-locked loop circuit with a wavelength division multiplexed device (WDM). This paper describes the circuit and its performance.