Characterization of the Thermal Conductivity of CH and Be by Refraction-Enhanced X-ray Radiography with a Deep Neural Network analysis

The thermal conductivity in the warm dense matter regime is critical for inertial confinement fusion experiments as it can impact the growth of hydro-instabilities at the ablator-fuel interface of the imploding capsule. Understanding it will also significantly extend the limits of knowledge in plasma physics as well as in other areas, such as astrophysics, planetary physics, geophysics and material science. We report the first measurement of thermal conductivity of CH and Be in the warm dense matter regime using a novel experimental platform based on x-ray differential heating and time-resolved refraction-enhanced radiography (RER). Additionally, we have developed a novel technique based on a deep neural network to retrieve the detailed interface density profiles. Our results indicate that the thermal conductivity of CH at about 8 eV at solid density is in reasonable agreement with four most widely used models but a correction term from electron-electron collisions has to be included. However, none of these models agree with the Be thermal conductivity in the range of 4–5 eV.