  Recent progress in laser wakefield acceleration has led to the emergence of a
new generation of electron and X-ray sources that may have enormous benefits
for ultrafast science. These novel sources promise to become indispensable
tools for the investigation of structural dynamics on the femtosecond time
scale, with spatial resolution on the atomic scale. Here, we demonstrate the
use of laser-wakefield-accelerated electron bunches for time-resolved electron
diffraction measurements of the structural dynamics of single-crystal silicon
nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept
study, we resolve the silicon lattice dynamics on a picosecond time scale by
deflecting the momentum-time correlated electrons in the diffraction peaks with
a static magnetic field to obtain the time-dependent diffraction efficiency.
Further improvements may lead to femtosecond temporal resolution, with
negligible pump-probe jitter being possible with future
laser-wakefield-accelerator ultrafast-electron-diffraction schemes.
