Towards high-performance optical master oscillators for energy recovery linacs

Advanced accelerators as well as 4th generation light sources require extremely precise timing distribution. Energy recovery linacs, for example, require precise timing of the electron bunches reentering the linac in order to minimize the disturbance of the RF amplitude and phase to evade resonant effects on the subsequent accelerated bunch. The timing distribution system has to maintain femtosecond precision over lengths ranging from several hundred meters to a few kilometers. We discuss potential optical master oscillators with exceptionally low timing jitter that can be used for ultra-precise timing distribution in such facilities. A promising approach is the use of a mode-locked laser that generates pulses with an ultra-stable repetition rate, distributed through fiber links. A good candidate is a mode-locked Erbium-doped fiber laser, featuring very low high-frequency noise in comparison to presently available microwave sources. Laser systems locked to atomic references are discussed, which may eventually enable synchronization of independent lasers in the facility with potentially few-femtosecond precision as well as pump–probe measurements with attosecond time resolution.