SLAC Femtosecond Laser Timing Synchronization System

SLAC femtosecond laser timing synchronization system is an FPGA based real time feedback control system that synchronizes laser oscillator to RF reference signal on femtosecond timing scale. The system was first installed on SLAC mega-electron-volt (MeV) ultrafast electron diffraction (UED) instrument in 2019 and has achieved 10 femtosecond laser-RF timing jitter on the UED laser oscillator. Since then, the system has been installed in a few other SLAC laser facilities, such as the LCLS (Linac Coherent Light Source) - II injector laser, LCLS-II pump-probe lasers, etc. These lasers have different tuning ranges from a few Hz per volt to a few hundred Hz per volt and tuning bandwidth from a few kHz to hundreds kHz. We have recently upgraded the firmware design to enable a wider operating range so that the system can be used on various SLAC lasers with different tuning parameters. This presentation describes the system algorithm, its FPGA implementation and test results from various lasers.