Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter

Abstract

This Letter presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5-35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. These results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible.

Designing radiation transport tests: Simulation-driven uncertainty-quantification of the COAX temperature diagnostic

“…Figure 3 shows the temperature profile of 3 separate simulations at 2 ns with a 1, 5, and 10 eV preheat. The 10 eV preheat (larger than expected from past studies [5]), produces only a small (∼ 1 − 2 eV) difference in the profile temperature. Our analysis supports the practice in most radiation transport experiments that this heating is unimportant because both the amount of high-energy emission (electrons and photons) is small compared to the total emission and most of this emission streams through the target.…”

“…Non-thermal electrons produced in the hohlraum can stream into the target, preheating the target material prior to the launch of the radiation front. For low-drive experiments, a few eV pre-heat can alter the evolution of the shock front [5]. But, for the COAX experiment, even a 10 eV pre-heat does not significantly alter the flow of the much more powerful COAX drive.…”

The effect of pre-plasma formation under nonlocal transport conditions for ultra-relativistic laser-plasma interaction

“…Theimportance of thenonlocal electron transport has been recently observed experimentally, where it was demonstrated that theclassical diffusive hydrodynamics fails to model thereal behavior of the plasma. In contrast, theNTH model succeeds to predict acomplex plasma behavior [12].…”

“…The plasma profile and the temperature are strongly affected by these nonlocal processes[7], which may also lead to asignificant effect on thehigh-power laser interaction as demonstrated in this work. A correct treatment of the ablation process requires anaccurate nonlocal radiation-hydrodynamics, which has been demonstrated in[8][9][10][11][12] during last several decades.Ablation physics under nonlocal transport conditions is of importance for two main applications:…”

A Composite Ansatz for Calculation of Dynamical Structure Factor

“…In dense plasmas, DSF, usually probed in x-ray Thomson scattering experiments, is considered as an important, and sometimes irreplaceable, diagnostic tool to probe thermal properties, such as temperature and density, in the internal regime of dense plasmas. [5,[38][39][40][41][42] It is a common practice to calculate DSF in the framework of time-dependent density functional theory (TDDFT), [43,44] which avoids the cumbersome calculation of the Bethe-Salpeter equation [1,45] of the many-body perturbation theory (MBPT) approach, owing to the less important contribution of long-range exchange and correlation effect in the DSF. [1] It was shown [16,25,35,46,47] as a rule of the thumb that for |𝑞| smaller than twice of the plasmon cutoff wave vector 𝑞c, the method reproduced the experimental DSF well with lifetime broadening effects included semi-empirically.…”