Synchrotron-based ultrafast x-ray diffraction at high repetition rates.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Ultrafast X-ray Diffraction (UXRD) is crucial for studying dynamic processes in materials.
• High repetition rate experiments present challenges in heat-load management and precise spatio-temporal alignment.

Purpose of the Study:

• To present and validate a novel UXRD setup at BESSY II optimized for high repetition rates.
• To address challenges associated with high heat-load and achieve precise laser-sample-X-ray synchronization.
• To investigate transient lattice dynamics in laser-excited materials.

Main Methods:

• Utilized a pump laser delivering 250 fs pulses at repetition rates from 208 kHz to 1.25 MHz.
• Implemented strategies for managing high heat-load and achieving 10 μm spatial overlap precision.
• Performed time-resolved X-ray diffraction on a laser-excited LSMO/STO superlattice.

Main Results:

• Achieved high spatial overlap precision and recorded transient lattice changes with an accuracy of δa/a(0) = 10(-6).
• Compared experimental time-resolved X-ray diffraction signals with phonon dynamics simulations.
• Determined X-ray pulse durations of 120 ps in standard mode and <10 ps in low-α mode.

Conclusions:

• The developed UXRD setup is effective for high-repetition-rate studies of ultrafast material dynamics.
• The system enables precise characterization of transient lattice changes and phonon dynamics.
• Accurate determination of X-ray pulse durations is critical for interpreting time-resolved data.