X-ray spectroscopy of hot dense plasmas using LLNL's upgraded Titan 2$ω$ short-pulse laser
We are developing an experimental platform at Lawrence Livermore National Laboratory's Jupiter Laser Facility to characterize X-ray emission from highly charged ions in the high-density ($n_e > 10^{23}$ cm$^{-3}$), high-temperature ($T_e \sim 1$ keV) regime, leveraging the recently upgraded frequency-doubled short-pulse Titan laser. These measurements will provide experimental benchmarks for high electron density effects on atomic structure, including Stark broadening, ionization potential depression, density-dependent line shifts, and suppression of dielectronic recombination, effects that are relevant to spectral modeling packages used by both the high-energy-density and astrophysics communities. Here, we describe the current status of the platform and present results from first experiments using the upgraded frequency-doubling capability, including calibrated K-shell spectra acquired from five time-integrated X-ray channels. Comparisons with MERL line shape calculations and with spectra recorded at AWE's Orion Laser Facility indicate that the upgraded Titan laser reliably produces the necessary plasma conditions, establishing a foundation for systematic benchmarking of high-density atomic physics in future campaigns.