Solid progress for X-ray lasers

With the advent of free-electron lasers, the high intensities previously only achievable with optical lasers can be produced at X-ray wavelengths. This opens new opportunities for theory and experiment. Here, Vinko et al . report the first detailed study of intense X-ray radiation interacting with solid density matter, carried out on the Linac Coherent Light Source free-electron laser at the SLAC National Accelerator Facility in California. They observe the generation of a solid-density plasma and establish that collisions have a pivotal role. The results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological samples and materials science investigations.