Energy transfer dynamics in strongly inhomogeneous hot-dense-matter systems

Direct measurements of energy transfer across steep density and temperature gradients in a hot-dense-matter system are presented. Hot-dense-plasma conditions were generated by high-intensity laser irradiation of a thin-foil target containing a buried metal layer. Energy transfer to the layer was measured using picosecond time-resolved x-ray emission spectroscopy. The data show two x-ray flashes in time. Fully explicit, coupled particle-in-cell and collisional-radiative atomic kinetics model predictions reproduce these observations, connecting the two x-ray flashes with staged radial energy transfer within the target.

Figure 1

Time-resolved data from (a) pure-Al and (b) Al-Fe admixture targets. The spectrally integrated temporal evolution of the Al ${\mathrm{He}}_{\alpha }$ (blue) and broadband emission (black) is shown for the (c) pure-Al and (d) Al-Fe cases. The broadband emission in (c) has been scaled by a factor of 10 for presentation clarity.

Figure 2

Simultaneous ${\mathrm{He}}_{\alpha }$ (black) and broadband (blue) emission from Al-Fe admixtures. Scaled pure-Al data (orange) are overlaid for comparison. The irradiation conditions were (a) 10 J, 0.7 ps; (b) 15 J, 0.7 ps.

Figure 3

(a) The spatially resolved electron density is shown for the entire target at $t_0+20\mathrm{ps}$ for the pure-Al case. The shaded region is the initial location of the buried tracer. Detailed views of the spatially resolved ion density and electron temperature in the Al-Fe tracer [(b)–(e)] and Al tracer [(f)–(i)] are shown at 10-ps intervals. The laser pulse delivered 10 J in 0.7 ps to an $\sim 5\mu \mathrm{m}$ (FWHM) focal spot. The temperature scales are shown separately at right for the Al-Fe admixture and pure-Al cases.

Figure 4

Time-dependent Al ${\mathrm{He}}_{\alpha }$ radiation (blue) estimated from the PIC model is compared to the data (black) for the Al-Fe admixture (a) and pure-Al (b) cases. Thin blue traces show the individual contributions from on- and off-axis material in the model.