Experimental and simulation studies of thermal transport based on plasma flow motion in laser-ablated dense regions of Au and CH

A practical experimental method is proposed to investigate thermal transport by characterizing the motion of plasma flows through a x-ray spectroscopic technique using tracers.By simultaneously measuring multiple parameters,namely,the mass-ablation rate,the temporal evolution of plasma flow velocities and trajectories and the temperature,it is possible to observe a variety of physical processes,such as shock wave compression,heating by thermal waves,and plasma thermal expansion,and to determine their relative importance in different phases during the irradiation of CH and Au targets.From a comparison with hydrodynamic simulations,we find significant differences in the motion of the plasma flows between CH and Au,which can be attributed to different sensitivities to the thermal transport process.There are also differences in the ablation and electron temperature histories of the two materials.These results confirm that velocities and trajectories of plasma motion can provide useful evidence in the investigation of thermal conduction,and the approach presented here deserves more attention in the context of inertial confinement fusion and high-energy-density physics.

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

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 densityρ0,multipliers are introduced to adjust the Au material parameters,Tr,andρ0 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,andρ0 scaling factors(η_(src),η_(op),η_(eos),and η_(ρ))are investigated via numerical simulations combined with fitting.Then,with the uncertainties in the measured Tr andρ0 fixed at 3.6%and 3.1%,respectively,experimental data are exploited as fiducial values to determine the ranges ofη_(op) andηeos.It is found that the ranges ofη_(op) andηeos 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 F_(max) and t_(half) obtained via simulations are in good agreement with the measurements,with maximum errors∼9.5%and within 100 ps,respectively.

Self-consistent and precise measurement of time-dependent radiative albedo of gold based on specially symmetrical triple-cavity Hohlraum

A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed.A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV.The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample.The results agree well owing to the symmetrical radiation in the secondary cavity.A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux,and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis,and also to agree well with the result of a simulation using the HYADES opacity.