Laser-driven low energy electron beams for single-shot ultra-fast probing of meso-scale materials and warm dense matter.

Laser wakefield acceleration has proven to be an excellent source of electrons and X-rays suitable for ultra-fast probing of matter. These novel beams have demonstrated unprecedented spatial and temporal resolution allowing for new discoveries in material science and plasma physics. In particular, the study of dynamic processes such as non-thermal melt and lattice changes on femtosecond time-scales have paved a way to completely new scientific horizons. Here, we demonstrate the first single-shot electron radiography measurement using an femtosecond electron source based on the downramp-density gradient laser-wakefield-acceleration with the use of a compact Ti:sapphire laser. A quasi-monoenergetic electron beam with mean energy of 1.9 ± 0.4 MeV and charge 77 ± 47 pC per shot was generated by the laser incident onto a gas target and collimated using a two ring-magnet beam path. High quality electron radiography of solid objects with spatial resolution better than 150 [Formula: see text]m was demonstrated. Further developments of this scheme have the potential to obtain single-shot ultrafast electron diffraction from dynamic lattices. This scheme poses a great promise for smaller scale university laboratories and facilities for efficient single-shot probing of warm dense matter, medical imaging and the study of dynamic processes in matter with broad application to inertial confinement fusion and meso-scale materials (mg g/cm[Formula: see text]).

Stable femtosecond X-rays with tunable polarization from a laser-driven accelerator.

Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications. In particular, electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays. This betatron source, which essentially reproduces the principle of a synchrotron at the millimeter scale, provides bright radiation with femtosecond duration and high spatial coherence. However, despite its unique features, the usability of the betatron source has been constrained by its poor control and stability. In this article, we demonstrate the reliable production of X-ray beams with tunable polarization. Using ionization-induced injection in a gas mixture, the orbits of the relativistic electrons emitting the radiation are reproducible and controlled. We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence. The polarization ratio reaches 80%, and the polarization axis can easily be rotated. We anticipate a broad impact of the source, as its unprecedented performance opens the way for new applications.