Equation of State Measurements for Proton Heated Warm Dense Aluminum

Understanding the properties of materials in the warm dense matter regime is crucial for advancing knowledge in fields ranging from astrophysics to high energy density physics. A key aspect is the equation of state (EOS), which defines the relationship between pressure, volume, temperature, and internal energy in a thermodynamic equilibrium. We present the measurement of the release isentrope of warm dense aluminum heated isochorically by a proton beam generated by the OMEGA EP short-pulse laser. The EP long-pulse beams were used to create an X-ray backlighter source for streaked X-ray radiography. We have probed a wide range of densities from under 0.01 g/cm³ to solid density. We have developed an analysis method based on the self-similar nature of the expansion, allowing us to precisely extract the pressure-density isentrope curve using a gradient descent algorithm. This model-independent measurement can subsequently be used to benchmark various EOS models.



This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.