Exploiting ~100 picosecond coherent x-ray pulses in ultra high-speed imaging
Third generation storage ring light sources–the first being The European Synchrotron–gave access, not only to bright x-rays, but also to partially coherent x-ray beams. Partial spatial coherence is a necessary requirement to observe interference effects caused by the propagation of a wave field scattered by an object. The spatial coherence length of synchrotron hard x-rays, which measures up to several tens of micrometers, paved way to the development of novel x-ray phase-contrast imaging methods. When combined with ultra high-speed x-ray detection strategies, the exploitation of ~100 picosecond coherent synchrotron x-ray pulses with MHz repetition rates is a powerful diagnostic to observe instantaneous velocities and internal structures that can not be obtained from x-ray attenuation-contrast imaging, and can not or only partially be probed using optical shadowgraphy. At beamline ID19, single-pulse x-ray phase-contrast imaging with MHz frame rates is now routinely performed for various in situ materials characterization. I will describe our strategies to push the limits of time-resolved hard x-ray imaging and will show visualizations of various transient processes such as crack propagation, explosion during electric arc ignition, laser-induced micro-cavitations, jetting, and shock compression.