X-ray Thomson Scattering of Fast-Electron-Heated Solid-Density Targets Using the LCLS XFEL

Non-thermal energetic electrons generated by high-intensity, short-pulse lasers are powerful sources for creating warm and hot dense matter and advancing fast ignition in inertial fusion energy. However, understanding the conditions of solid-density targets heated by such fast electron transport remains limited due to the lack of diagnostics capable of resolving rapid transitions and strong gradients across the target. To address these challenges, we used the LCLS X-ray Free Electron Laser (XFEL) to diagnose laser-irradiated solid targets with X-ray Thomson Scattering. In this experiment, titanium and plastic foils were irradiated by a relativistic-intensity, femtosecond laser. Hard X-ray pulses at 15 keV penetrated the preplasma and directly probed the solid-density region, while the femtosecond pulse duration and adjustable spot size enabled spatiotemporally resolved measurements. X-ray scattering signals were recorded using a heavily shielded X-ray transmission crystal spectrometer and HAPG spectrometer. Details of the experiment and results for cold and fast-electron-heated targets will be presented.