Precise control and measurement of Laser–RF synchronization for Thomson-scattering X-ray source

X-ray sources based on Thomson-scattering require strict synchronization between the laser pulse and the electron bunch. Jitter between the laser and the RF phase should be kept within a femtosecond scale to guarantee electron beam quality and the time of flight before impact with the terawatt laser pulse. A laser–RF synchronizer that uses the 36th harmonic of the laser repetition rate was built at Tsinghua University, and it has tested to have a less than 100-fs [10-Hz, 100-kHz] rms time jitter. An RF deflector cavity is used to verify the electron bunch pulse-to-pulse time jitter with respect to the RF accelerating phase in the same condition, and the result shows a 540-fs rms jitter. This paper discusses the synchronization experiment setup, as well as the time jitter measurements under different conditions.