Fig. 1: Configuration for laser pump−electron probe experiments and diffraction patterns of Al single crystals at ambient (uncompressed) conditions.

a Experimental setup for in situ UED under dynamic compression. The 3.7-MeV electrons generated by a radio-frequency (RF) gun are focused by two separate solenoids onto the sample; the electron beam spot size at the sample location is ~184 μm × 250 μm (x × y), the electron bunch charge is ~90 fC and the pulse duration is ~0.6 ps. The sample is rotated around the y-axis by a certain angle to probe lattice planes with a desired orientation (see bottom panel). The sample is ablated by counter-propagating laser pulses (800 nm, 20 ps FWHM, ≤10 mJ) with a Gaussian-like intensity profile (~360 μm FWHM). The laser incident angle is close to normal incidence. The inset shows the time history of peak particle velocity and peak pressure in 200-nm-thick Al irradiated with a laser fluence of 4.3 J cm⁻², which are obtained by hydrodynamics simulation (see the “Methods” section). b The pump-probe spatial overlap viewed from the crystal lattice perspective, and the comparison of the ambient diffraction patterns between simulations and experiments. The simulated diffraction pattern is used to identify the detected lattice planes.