First Indirect Drive Experiment Using a Six-Cylinder-Port Hohlraum

The new hohlraum experimental platform and the quasi-3D simulation model are developed to enable the study of the indirect drive experiment using the six-cylinder-port hohlraum for the first time. It is also the first implosion experiment for the six laser-entrance-hole hohlraum to effectively use all the laser beams of the laser facility that is primarily designed for the cylindrical hohlraum. The experiments performed at the 100 kJ Laser Facility produce a peak hohlraum radiation temperature of $\sim 222\mathrm{eV}$ for $\sim 80\mathrm{kJ}$ and 2 ns square laser pulse. The inferred x-ray conversion efficiency $\eta \sim 87\%$ is similar to the cylindrical hohlraum and higher than the octahedral spherical hohlraum at the same laser facility, while the low laser backscatter is similar to the outer cone of the cylindrical hohlraum. The hohlraum radiation temperature and $M$-band ($>1.6\mathrm{keV}$) flux can be well reproduced by the quasi-3D simulation. The variations of the yield-over-clean and the hot spot shape can also be semiquantitatively explained by the calculated major radiation asymmetry of the quasi-3D simulation. Our work demonstrates the capability for the study of the indirect drive with the six-cylinder-port hohlraum at the cylindrically configured laser facility, which is essential for numerically assessing the laser energy required by the ignition-scale six-cylinder-port hohlraum.

Figure 1

The schematic scheme of the indirect drive experiment with the SCP hohlraum. The beams in orange (55°) and green (49.5°) are the outer beams of the cylindrical hohlraum, while the beams in blue (28.5°) and cyan (35°) are the inner beams.

Figure 2

(a) The normalized peak $T_r$ by the FXRDs with view sight shown at the bottom. The different colored symbols represent different shots. The laser spots on the wall are shown by the colored spots. The polar direction is shown by the black arrows. Here, $T_r$ is normalized to $E_l^{\mathrm{net}}=80\mathrm{kJ}$ by $T_r={(80\mathrm{kJ}/E_l^{\mathrm{net}})}^{0.25}{T}_r^{\exp }$. (b) The peak $T_r$ versus $E_l^{\mathrm{net}}$ for FXRD-3. The error bar of the $T_r$ is $\pm 2.5\%$.

Figure 3

(a) The schematic scheme of the quasi-3D simulation. The laser incident angle and the laser trajectory are also shown. (b) Comparisons of the $T_r$ and the $M$-band flux between the experiment and the simulation for N166.

Figure 4

The postprocessed capsule $T_r$ and radiation asymmetry for N166 (a) and N176 (b).

Figure 5

The yield degradation by radiation asymmetry for N166 (a) and N176 (b).

Figure 6

The equatorial hot spot self-emission images from the experiments [(a) and (c)] and simulations [(b) and (d)]. The dashed lines are the 30% contour. The 30% contour in panel (d) is overplotted on panel (c) since the noise level is too significant to analyze the asymmetry.