Few-femtosecond resolved imaging of laser-driven nanoplasma expansion
Christian Peltz, J. A. Powell, Philipp Rupp, Adam M. Summers, T. Gorkhover, Markus Gallei, I. Halfpap, E. Antonsson, B. Langer, Carlos Trallero–Herrero, Christina Gräf, D. Ray, Qingcao Liu, T. Osipov, Maximilian Bucher, Ken Ferguson, Søren Møller, Sergey Zherebtsov, Daniel Rolles, E. Rühl, Giacomo Coslovich, Ryan Coffee, Christoph Bostedt, Artem Rudenko, Matthias F. Kling, Thomas Fennel
Abstract
Abstract The free expansion of a planar plasma surface is a fundamental non-equilibrium process relevant for various fields but as-yet experimentally still difficult to capture. The significance of the associated spatiotemporal plasma motion ranges from astrophysics and controlled fusion to laser machining, surface high-harmonic generation, plasma mirrors, and laser-driven particle acceleration. Here, we show that x-ray coherent diffractive imaging can surpass existing approaches and enables the quantitative real-time analysis of the sudden free expansion of laser-heated nanoplasmas. For laser-ionized SiO 2 nanospheres, we resolve the formation of the emerging nearly self-similar plasma profile evolution and expose the so far inaccessible shell-wise expansion dynamics including the associated startup delay and rarefaction front velocity. Our results establish time-resolved diffractive imaging as an accurate quantitative diagnostic platform for tracing and characterizing plasma expansion and indicate the possibility to resolve various laser-driven processes including shock formation and wave-breaking phenomena with unprecedented resolution.