Dynamic X-ray imaging of shock evolution and plasma instability formation using a laser wakefield accelerator

Laser wakefield acceleration is a source of ultrafast, and spatially-coherent X-ray pulses with small source size suitable for high resolution imaging. In combination with a high-repetition-rate scheme, the radiation bursts permit recording submicron scale time-dependent systems such as hydrodynamic instabilities. In this work we performed dynamic phase-contrast X-ray imaging of the interaction of a long laser pulse with a liquid target, thus observing the evolution of a shock wave in water with unprecedented spatio-temporal resolution. CRASH hydrodynamic simulations complement the experimental results agreeing qualitatively well for t < 1ns, yet the data reveals unforeseen physics later in time. This includes multi-shock generation within the liquid jet, and plasma instability formation. It is suspected that the absence of charge separation in CRASH is responsible for some of the effects observed with the X-rays. To this end, innovative electron-beam radiography was used to probe the laser-plasma interplay finding evidence of bilateral heating of the water followed by strong electric field generation. These measurements help explaining some of the discrepancies between simulation and experiment and pave the way to better plasma diagnostic systems in HED physics experiments.