High-repetition-rate lasers for measurements of the equation of state of boron nitride

Over the past decade, high-power laser experiments have enabled access to warm dense matter, an intermediate regime between solids and ideal plasmas, characterized by weak ionization, strong coupling, and partial degeneracy. In this regime, the equation of state (EoS) is a key quantity for describing the thermodynamic properties of matter. Although ab initio calculations provide increasingly accurate predictions for the EoS, experimental data that are both accurate and statistically significant remain essential to constrain theoretical models. However, most kilojoule-class laser systems operate at low repetition rates, limiting the amount of available data. The recently commissioned L4n beamline at ELI-Beamlines (Czech Republic) overcomes this limitation by combining kilojoule-scale energy with high-repetition-rate (HRR) operation. Leveraging this capability, we performed the first laser-driven shock compression experiment on hexagonal boron nitride (h-BN) at the L4n beamline, using Velocity Interferometer System for Any Reflector and streak optical pyrometry diagnostics to measure shock velocities. By complementing the existing experimental Hugoniot database for h-BN, this work demonstrates the capability of the HRR L4n beamline for EoS measurements, paving the way for larger experimental datasets in future experiments.