Fast and Furious: Ultrafast Collisional Dynamics in Plasmas

Abstract
Electron collisional dynamics controls energy transport, conductivity, diffusion, and relaxation in dense plasmas. The motivation to understand these processes is driven by the prevalence of dense plasmas in astrophysical environments, their growing importance in laser-plasma interactions, and their role in inertial fusion 
energy deposition. However, despite significant theoretical advances, experimental studies of collisional dynamics remain scarce. In this talk I present efforts to directly measure ultrafast collisional relaxation of non-thermal electrons using ultrafast hard x-rays. By tailoring the non-thermal electron distribution, we extract both electron-electron and electron-ion collision rates, discriminate between commonly used impact-ionisation models, and place an upper bound on the electron-electron thermalisation timescale at solid density. Our approach enables new opportunities to probe the fastest plasma dynamics on their natural timescales, helping us better understand extreme states of matter driven far from equilibrium.