Development Status of an EOM-Based Laser Arrival Time Monitor for large-scale XFEL facilities

Abstract The Laser Arrival Time Monitor (LAM) is vital for ensuring precise timing synchronization in X-ray Free Electron Lasers (XFEL), which is crucial for high-resolution imaging and experiments. One effective LAM approach utilizes an Electro-Optic Modulator (EOM) to encode phase information of the modulation signal onto the amplitude of reference pulses. This method is advantageous due to its resolution, measuring range and stability. However, various key parameters of the EOM, including its modulation signal characteristics, significantly impact the resolution of the LAM system. In this study, we designed and constructed a Laser Arrival Time Measurement system tailored for large-scale XFEL facilities, detailing the system architecture and discussing key factors affecting the resolution of the LAM system, along with optimization strategies. Through an in-depth analysis of the signal’s spectral characteristics, we identified that certain frequency components within the 4-8 GHz range significantly impact the system’s performance. Targeted filtering and signal optimization significantly improved laser arrival time measurement accuracy and reliability by reducing signal-distorting frequency components.