X-ray Spectroscopy in Relativistic Laser-Solid Interactions

X-ray spectroscopy is a powerful technique to investigate the extreme states of matter created by relativistic laser-solid interactions, which are of great importance for high energy density physics, laboratory astrophysics, inertial confinement fusion, particle acceleration, and ultrafast x-ray sources. This talk will present the research of x-ray spectroscopy in relativistic laser-solid interactions concerning two aspects. First, laser-driven ultrafast x-ray sources from structured targets are investigated via K-shell emission spectroscopy, revealing a critical factor constraining the “cold” K-alpha emission yield despite the increase of hot electron production. In addition, an additional and novel heating mechanism is discovered in the nanowire foam targets except for the increased laser absorption, explaining the significant enhancement of He- and Ly-alpha emission. Second, the dynamics of ultrafast relativistic laser-plasma systems is studied via x-ray emission spectroscopy in combination with numerical simulations. Based on particle-in-cell (PIC), hydrodynamic, atomic kinetics simulations, and x-ray spectroscopy, a complex spatiotemporally resolved analysis of time- and space-integrated x-ray emission spectroscopy from relativistic laser plasmas is presented, enabling insights into relativistic laser-plasma dynamics across different timescales. The result demonstrates that the combination of x-ray spectroscopy, atomic physics, and multi-scale simulations is a promising method to characterize the evolution of internal conditions of plasmas created by short-pulse lasers and can also serve as an effective benchmark for numerical simulations.