Implementation of a high precision laser synchronization for pump-probe time-resolved experiments at TPS 15A

Abstract Synchrotron generates short and intense X-ray pulses to investigate the properties of materials. Scientists can observe the relaxation process of materials following the excitation by an intense laser pulse and subsequent probing with a precisely delayed X-ray pulse. The separation between these pulses needs to vary from picoseconds to 10 2 nanoseconds with picosecond precision. Traditionally, achieving such time delays has relied on mechanical or electrical methods. Mechanical approaches involve using optical delay lines to alter the optical path length or adjusting the length of cables to introduce the necessary time delay. Electrical methods employ delay generators, phase shifters, or analogue vector modulators (I-Q) to quickly vary the delay, but they typically offer precision in the order of 10 picoseconds due to nonlinearity and offset. Calibration is often required to improve precision, but it remains constrained. Using the delay functionality of accelerator’s event timing system is limited by delay step and jitter in the 10 psec order or more. Direct digital synthesizers (DDS) offer near-ideal phase-shifting capabilities. In our work, we have developed a laser synchronization and timing support device utilizing DDS to precisely control delay time, with time resolution limited by phase noise. The delayed signal is fed to a frequency divider, whose output serves as the reference for the laser oscillator and sync signal for the laser amplifier. The DDS approach surpasses I-Q-based devices in performance. Supported by a single-board computer operating in the EPICS environment, our device seamlessly integrates with experimental control systems. This paper provides detailed insights into the implementation and test results of our approach.