Fig. 1. (a) and (b) Schematic of Hohlraum and experimental setup. To suppress movement of the Au bubble, the Hohlraum is filled with neopentane (C₅H₁₂) gas at about 0.4 atm and has thin (0.5 μm) plastic membranes covering the laser entrance holes (LEHs) and diagnostic holes (DHs). (c) Laser power per beam. There is a small prepulse with duration of 1.0 ns arriving 0.5 ns before the main pulse to heat the membranes attached to the LEHs, causing them to expand and evaporate.

Fig. 2. (a)–(d) Simulated radiative temperature distribution of the secondary cavity wall with laser injection from (a) two sides and (b) one side at high temperature, and (c) two sides and (d) one side at low temperature. (e)–(h) Simulated incident radiative temperature distribution to the standard sample at the secondary cavity waist with laser injection from (e) two sides and (f) one side at high temperature, and (g) two sides and (h) one side at low temperature.

Fig. 3. Radiation fluxes measured by (a) D20/U42 FXRD detectors and (b) U16/U42/U64 FXRD detectors. The solid and dashed lines represent the results from the three-cavity Hohlraum shots, and the dotted line represents the result from the one-cavity Hohlraum shot. (c) Experimental reemission flux from the secondary cavity. It can be seen that the SRFD (whose field of view is represented by the white circle) is aimed at the center of the diagnostic hole (magenta circle), where the reemission is relatively uniform. (d) Shock velocity of aluminum–quartz sample. The inset is an example of an original interference fringe image measured by VISAR.

Fig. 4. (a) Incident flux and radiative albedo of secondary cavity from the multi-angle flux balance analysis (T_in0, α₀) and from an iterative analysis with the experimental shock velocity (T_in1, α₁), together with simulated radiative albedo for different opacity parameters. (b) Comparison between experimental shock velocity and simulation results with incident flux T_in0 from flux balance analysis and T_in1 from iterative analysis with D_exp.