Properties of hot-spot emission in a warm plastic-shell implosion on the OMEGA laser system

A warm plastic-shell implosion is performed on the OMEGA laser system. The measured corona plasma evolution and shell trajectory in the acceleration phase are reasonably simulated by the one-dimensional lilac simulation including the nonlocal and cross-beam energy transfer models. The results from analytical thin-shell model reproduce the time-dependent shell radius by lilac simulation and also the hot-spot x-ray-emissivity profile at stagnation predicted by spect3d. In the spect3d simulations within a clean implosion, a U-shaped hot-spot radius evolution can be observed with the Kirkpatrick-Baez microscope response (the photon energy is from 4 to 8 keV). However, a fading-away hot-spot radius evolution is measured in OMEGA warm plastic-shell implosion because of mixings. To recover the measured hot-spot x-ray emissivity profile at stagnation, a nonisobaric hot-spot model is built and the normalized hot-spot temperature, density, and pressure profiles (normalized to the corresponding target-center values) are obtained.

Figure 1

(a) Target and (b) laser pulse intensity in the experiment. A fill tube of $30\mu \mathrm{m}$ outer diameter was used.

Figure 2

(a) Measured (by the channel H13B) and simulated scattered light by lilac and (b) measured and (c) simulated scattered-light spectra.

Figure 3

Simulated and measured corona temperatures at quarter-critical surface in corona plasma.

Figure 4

Simulated and measured shell-ablation-surface trajectories and the laser power pulse.

Figure 5

Comparison of measured neutron rate, lilac predicted neutron rate, and predicted $\rho R$ evolution.

Figure 6

Evolution of the shell radius by lilac simulation and thin-shell model without $\alpha$ heating. The start of the deceleration phase (the end of the laser pulse) is 0 ns.

Figure 7

(a) The spect3d-simulated hot-spot radius with the KBFRAMED response (the photon energy is 4–8 keV). (b) The KBFRAMED response. (c) Time-dependent emission of the implosion filtered with the KBFRAMED response.

Figure 8

Normalized profiles of hot-spot density and $T_e$ by lilac, x-ray emission by spect3d, and x-ray emission by an analytical thin-shell model. All the plots are at stagnation.

Figure 9

The spect3d-simulated U-shaped hot-spot radius and KBFRAMED measured hot-spot radius (shot 84 605).

Figure 10

The KBFRAMED images of hot-spot x-ray emission (shot 84 605).

Figure 11

(a) The PSF smoothed image of the hot spot recorded at stagnation by the KBFRAMED (shot 84 605). (b) Super-Gaussian fit of (a). (c) Measured and fitted intensity profiles taken through the centers of the x-ray images along the dashed lines in (a) and (b).

Figure 12

Hot-spot x-ray-emissivity profile by fitting, the emissivity profile after an inverse Abel transform, and the emissivity profile by the isobaric thin-shell model. (b) Normalized $T_e$ profiles by the thin-shell isobaric model and nonisobaric model with different parameters. (c) Normalized density profiles by the thin-shell isobaric model and nonisobaric model with different parameters. (d) Normalized pressure profiles by the thin-shell isobaric model and nonisobaric model with different parameters. All the $x$ axes are normalized to the hot-spot size of $38\mu \mathrm{m}$ at stagnation.