Abstract
Material shock release generally happens in the targets of high-energy-density (HED) and inertial confinement fusion (ICF) experiments but has been challenging to study experimentally, theoretically, or computationally. Here, we report extensive studies of polystyrene (CH) shock release by employing large-scale nonequilibrium molecular dynamics and laser-drive experiments at various shock strengths. Our experimental design prevents radiation preheating of the sample and employs a witness foil to investigate the release of shocked CH across a vacuum gap. We observe earlier acceleration of the foil by the release of CH under stronger shocks as well as reflectivity changes in the interferometry data before the foil moves, which is strong evidence of hydrogen streaming ahead of carbon at the release front, consistent with findings from our simulations. Furthermore, our calculations show that lighter species or hydrogen isotopes can carry more mass by one to two orders of magnitude to farther distances during the release and that only less than 0.1 times thermal expansion as predicted by hydrodynamics is needed to explain the high velocities and large scale lengths of low-density plasmas observed in radiation-preheated CH release experiments. These results highlight the significant role of species separation in the shock release of compounds. This process shall be considered, and its potential effects shall be clarified, in the design, interpretation, and analysis of future HED and ICF experiments.
Highlights
The shock release of matter into vacuum or low-density gases is of great interest to those researching inertial confinement fusion (ICF), high-energy-density (HED) sciences [1,2,3,4], planetary sciences [5], and astrophysics [6] but is challenging to study both experimentally and theoretically
We extend the classical molecular-dynamics (CMD) simulation efforts to study the release of shocked CH by considering a broad range of shock strengths, multiple types of hydrogen isotopes, and different degrees of thermal expansion of the CH sample caused by radiation preheat, which are relevant to various ICF and HED campaigns [37,38,46,47,48]
We have combined large-scale nonequilibrium CMD simulations with laser-drive experiments to study the shock release of CH polystyrene at shock strengths spanning from 50 to 13 500 GPa
Summary
The shock release of matter into vacuum or low-density gases is of great interest to those researching inertial confinement fusion (ICF), high-energy-density (HED) sciences [1,2,3,4], planetary sciences [5], and astrophysics [6] but is challenging to study both experimentally and theoretically. The exclusion of atom-specific properties and chemical changes causes problems (such as kinetic effects [8,9,10,11,12,13,14,15,16,17]) for target design, performance, and even interpretation of experiments. This calls for a better understanding of shock release from a variety of matter in broad ranges of pressures, temperatures, and space and time scales.
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