Fig. 1. Illustration of the evolution of a massive molecular cloud, indicating the importance of SNR propagation in forming new stars.

Fig. 2. Experimental setup for N₂ at 11.4 mbar. Not to scale.

Fig. 3. Experimental results in N₂ at 11.4 mbar. (a) Expansion of a single BW, taken 100 ns after the main pulse, toward the obstacle located 7.07 mm from the carbon rod. (b) Expansion of a single BW, taken at 450 ns, toward the obstacle located 11 mm from the carbon rod. (c) Zoom of (b) showing the deviation of the morphology of the BW from spherical to nonspherical when interacting with the foam ball. (d) Interferogram corresponding to (a). (e) Simulated interferogram. (f) Electron density profile corresponding to (f). (g) Experimental BW radius R vs time taken as illustrated in (a), i.e., parallel to the rod orientation. (h) Instantaneous velocity deduced from radius measurements vs time.

Fig. 4. Comparison between PrismSPECT simulations and experimental data averaged between 138 and 162 ns, corresponding to the time of impact with the obstacle. The simulations were performed with an initial mass density ρ = 5 × 10⁻⁵ g/cm³. The best agreement is found for a temperature in the range of 4.5–4.9 eV.

Fig. 5. X-ray radiographs of the 150 mg/cm³ foam ball: (a) without the influence of a BW, for reference; (b) at t = 500 ns after the beginning of the main laser pulse.

Fig. 6. (a) Schlieren data showing the expansion of both BWs toward the obstacle t = 100 ns after the beginning of the interaction. The thin red arrow indicates the expansion of the interaction zone formed by the collision of the two BWs. (b)–(g) Corresponding x-ray radiographs of the 150 mg/cm³ foam ball at different times during the interaction: (b) without the influence of a BW; (c) at 300 ns; (d) at 500 ns; (e) at 700 ns; (f) at 1000 ns; (g) at 1500 ns. The green arrows in (c) show the trajectories of the two BWs.

Fig. 7. (a) Deformation of the foam. The inset shows the different ways measurements were performed. (b) Mass density retrieved from the data shown in Fig. 6 (here 0 corresponds to the middle of the foam).

Table 1. Summary of experimental and astrophysical parameters. Astrophysical data for the SNRs are taken from Ref. 32.