Development of ultra-fast bright laser-driven x-ray probes with high intensity for Warm Dense Matter probing

Ultra-fast probing with x-ray sources for radiography and x-ray Thomson scattering is now of a great interest to plasma physics, in particular to study transport properties of WDM in relevance to astrophysical phenomena and inertial confinement fusion. Laser-driven K-alpha sources have proven to be excellent for this purpose, in particular for high energy laser experiments, however due to relatively low conversion efficiency in comparison to He-alpha and Ly-alpha sources, their applicability has been limited. Recent theoretical studies have shown that adding micro-scale structures to the laser-driven solid foils generating the x-rays can significantly enhance the flux of such sources. So far, only a handful of experimental studies of the use of these micro-structured targets has been carried out. We present experimental results developing bright x-ray sources driven by short-pulse lasers with copper foam targets. We have used low density copper nanowire foams driven by the Trident laser at ~10²⁰ W/cm² and 80 J energy. X-ray spectroscopy methods were used to characterize the laser-target interaction exploring the absorption efficiency of the laser and subsequent effect on the production of hot electrons and strongly enhanced target heating compared to flat foils. The experimental results were compared with atomic and particle-in-cell simulations.