Ultrafast imaging of relativistic instabilities in solid-density plasmas

The streaming of relativistic charged particles gives rise to kinetic instabilities that magnetize astrophysical and laboratory plasmas. These (collective) fields impact plasma dynamics and their study is critical to a wide range of systems, from cosmic-ray transport in galaxies to the solar wind to fusion plasmas.

 Despite their importance, the direct experimental characterization of these instabilities has remained a challenge. I will discuss the results from experiments combining a high-intensity optical laser with a high peak-brightness X-ray laser at LCLS that successfully imaged relativistic kinetic instabilities in solid-density plasmas with an unprecedented spatial and temporal resolution of 200 nm and 50 fs.

The measured plasma density evolution, together with supporting theoretical analysis and kinetic simulations, reveal a unique interplay between space-charge, resistive effects and ion dynamics on the development of the instabilities. These findings further indicate that magnetic fields on the order of 1000 Tesla are produced, which help confine high-energy electrons with important implications for the transport of energetic particles in plasmas.