Abstract
Using the SG-III prototype laser at China Academy of Engineering Physics, Mianyang, we irradiated polystyrene (CH) samples with a thermal radiation drive, reaching conditions on the principal Hugoniot up to P ≈ 1 TPa (10 Mbar), and away from the Hugoniot up to P ≈ 300 GPa (3 Mbar). The response of each sample was measured with a velocity interferometry diagnostic to determine the material and shock velocity, and hence the conditions reached, and the reflectivity of the sample, from which changes in the conductivity can be inferred. By applying the self-impedance mismatch technique with the measured velocities, the pressure and density of thermodynamic points away from the principal Hugoniot were determined. Our results show an unexpectedly large reflectivity at the highest shock pressures, while the off-Hugoniot points agree with previous work suggesting that shock-compressed CH conductivity is primarily temperature-dependent.
Highlights
The behavior of hydrocarbons under extreme conditions is of great interest across the field of high-energy-density science
Consisting of two of the most common elements within giant planets, they serve as an excellent example for study of the behavior of planetary interiors.1,2. They are used as pushers for shock compression experiments on other materials3 and to contain deuterium–tritium mixtures in inertial confinement fusion experiments.4. In many of these cases, the material is driven by a single shock, and so the state reached can be described by the Rankine–Hugoniot relations, the conditions in so-called off-Hugoniot states—reached by either ramp compression or subsequent shocks—are important, but are significantly harder to determine
We have demonstrated that self-impedance mismatch has the capability to apply the results of Hugoniot measurements on plastics to directly determine conditions away from the principal Hugoniot
Summary
The behavior of hydrocarbons under extreme conditions is of great interest across the field of high-energy-density science. Consisting of two of the most common elements within giant planets, they serve as an excellent example for study of the behavior of planetary interiors.1,2 They are used as pushers for shock compression experiments on other materials and to contain deuterium–tritium mixtures in inertial confinement fusion experiments.. Off-Hugoniot states will tend to have a lower temperature than if the same pressure were reached with single shock. At pressures reached by a single shock, we observe higher than expected reflectivity; under double-shocked conditions, the reflectivity is lower than would be expected for the same pressure in a single shock, but shows a similar relationship as a function of simulated temperature. This may indicate that the metallization of CH at the shock front is primarily temperature-dependent
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