Thermal Transport Study of warm dense CH and Be by Refraction-Enhanced X-ray Radiography with a Deep Neural Network analysis

Thermal transport properties of warm dense matter affect the evolution of many systems, ranging from geodynamo in the Earth's core, to hydrodynamic instability growth in inertial confinement fusion (ICF) capsules. We report thermal conductivity measurements of CH and Be in the warm dense matter regime using x-ray differential heating and time-resolved refraction-enhanced radiography. The experiments were performed at the Omega laser facility. A cylindrically curved interface between CH and Be was isochorically heated by x-rays. The subsequent evolution of the interface was recorded by x-ray radiography with refraction enhanced contrast. A novel technique with an untrained deep neural network has been developed to retrieve the detailed interface profiles. The phase information can be decoded from one single intensity measurement when we apply physics constraints to the result. Multiple transport phenomena including thermal diffusion and wave propagation were revealed. The sensitivity of this radiographic technique to density gradients allows simultaneous constraints on the density, temperature and thermal conductivity.