Study of Discrepancies in Deuterium Sound Speed Near 200 GPa

Accurately modeling the Equation of State (EOS) for hydrogen and its isotopes is crucial for understanding fundamental processes in Inertial Confinement Fusion (ICF) and astrophysical phenomena. In a recent study, D. E. Fratanduono et al. identified discrepancies in the sound speed of deuterium at pressures around 200 GPa, revealing limitations in current modeling capabilities. In this work, we report on an experiment conducted using the OMEGA 60 laser system to investigate this anomaly. Preliminary results from the experiment are presented, providing initial insights into the observed discrepancies. Additionally, we discuss the theoretical basis, including the potential role of the electrostatic acoustic mode in these anomalies. Complementary large-scale Particle-in-Cell (PIC) simulations of ion-acoustic waves are also presented, offering valuable context for interpreting the experimental findings.