Theoretical investigations on x-ray transport in radiation transport experiments on the Shenguang-III prototype laser facility

Guangwei Meng,Tianming Song,Min Wang,Jiamin Yang,Jun She

doi:10.1063/5.0043745

Abstract

Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-III prototype laser facility in 2012. In this paper, the radiation fluxes out of CH foam cylinders at different angles are analyzed theoretically using the two-dimensional radiation hydrodynamics code LARED-R. Owing to the difficulty in validating opacity and equation of state (EOS) data for high-Z plasmas, and to uncertainties in the measured radiation temperature Tr and the original foam density ρ0, multipliers are introduced to adjust the Au material parameters, Tr, and ρ0 in our simulations to better explain the measurements. The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf (defined as the time corresponding to the radiation flux at half-maximum) on the radiation source, opacity, EOS, and ρ0 scaling factors (ηsrc, ηop, ηeos, and ηρ) are investigated via numerical simulations combined with fitting. Then, with the uncertainties in the measured Tr and ρ0 fixed at 3.6% and 3.1%, respectively, experimental data are exploited as fiducial values to determine the ranges of ηop and ηeos. It is found that the ranges of ηop and ηeos fixed by this experiment overlap partially with those found in our previous work [Meng et al., Phys. Plasmas 20, 092704 (2013)]. Based on the scaled opacity and EOS parameters, the values of Fmax and thalf obtained via simulations are in good agreement with the measurements, with maximum errors ∼9.5% and within 100 ps, respectively.

Highlights

Radiation transport is of crucial importance to high-energydensity physics (HEDP)1,2 and is a fundamental energy transport mechanism in inertial confinement fusion (ICF)3 and in many laboratory and astrophysical plasmas.4–8 In indirect drive ICF, a high-Z hohlraum is used to convert large amounts of laser energy into high-temperature x-rays, which are absorbed by the ablator of a fusion capsule through radiation transport, with radiation hydrodynamic behavior ensuing
The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf on the radiation source, opacity, equation of state (EOS), and ρ0 scaling factors are investigated via numerical simulations combined with fitting
III A, we describe the radiation source in our simulations, present the simulation results calculated with LARED-R using the original Au material parameters, and discuss the possible physical factors resulting in discrepancies between simulations and scitation.org/journal/mre experiments

Summary

INTRODUCTION

Radiation transport is of crucial importance to high-energydensity physics (HEDP) and is a fundamental energy transport mechanism in inertial confinement fusion (ICF) and in many laboratory and astrophysical plasmas. In indirect drive ICF, a high-Z hohlraum is used to convert large amounts of laser energy into high-temperature x-rays, which are absorbed by the ablator of a fusion capsule through radiation transport, with radiation hydrodynamic behavior ensuing. A theoretical method was proposed to verify the opacity and equation of state (EOS) of high-Z plasmas in rarefactive states, based on two independent experimental measurements, namely, the propagation of heat waves and hydrodynamic motion in radiation ablation processes. Back et al. have performed experiments on lowdensity (40–50 mg/cm3) foams to study diffusive supersonic radiation transport, where the ratio of the diffusive radiation front velocity to the material sound speed exceeds 2, using the Omega laser facility. The propagation of heat waves within CH foam cylinders was explored experimentally on the Shenguang-III prototype laser facility in 2012. The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf (defined as the time corresponding to the radiation flux at half-maximum) on the radiation source, opacity, EOS, and ρ0 scaling factors (ηsrc, ηop, ηeos, and ηρ) are investigated via numerical simulations combined with fitting.

MODEL AND METHOD

RESULTS AND DISCUSSION

Simulation results using the original Au material parameters

CONCLUSIONS