Main Injector synchronous timing system

The Synchronous Timing System is designed to provide sub-nanosecond timing to instrumen-tation during the acceleration of particles in the Main Injector. Increased energy of the beam particles leads to a small but significant increase in speed, reducing the time it takes to com-plete a full turn of the ring by 61 nanoseconds (or more than 3 RF buckets). In contrast, the reference signal, used to trigger instrumentation and transmitted over a cable, has a constant group delay. This difference leads to a phase slip during the ramp and prevents instrumentation such as dampers from properly operating without additional measures. The Synchronous Tim-ing System corrects for this phase slip as well as signal propagation time changes due to tem-perature variations. A module at the LLRF system uses a 1.2 Gbit/s G-Link chip to transmit the RF clock and digital data (e.g. the current frequency) over a single mode fiber around the ring. Fiber optic couplers at service buildings split off part of this signal for a local module which reconstructs a synchronous beam reference signal. This paper describes the background, design, and expected performance of the Synchronous Timing System