Towards Characterizing Thermal Conductivity in Warm Dense Matter via Shock Ringing

Heat transport plays a fundamental role in inertial confinement fusion (ICF), where implosion performance is acutely sensitive to transport through shocked capsule materials. Despite this, scant experimental data exist to constrain models of thermal conductivity in warm dense matter (WDM) [1], and these models vary significantly in their predictions for even the best-studied materials at identical conditions [2]. We present computational evidence of coupling between ablator thermal conductivity and shock ringing in multi-layer targets irradiated by high-energy lasers. In such geometries, reverberating density waves arise from shock-interaction with the impedance gradients at material boundaries; using a Spitzer-Hãrm conduction model, we find that the amplitude and length scale of these waves depend strongly on conductivity. This relationship allows us to constrain simulated conductivities in ICF-relevant materials at WDM conditions with measurements of shock ringing in experimental targets. We present preliminary results for Kapton using data from experiments at the Linac Coherent Light Source (LCLS).

[1] T. G. White et al. Phil. Trans. Roy. Soc. A 381, 20220223 (2023).

[2] L. J. Stanek et al. Phys. Plasmas 31 (5): 052104 (2024).