Fig. 1. Schematic representation of the octad LPI experiment on the Shenguang Octopus facility. The top left inset shows the incident power of each beam.

Fig. 2. (a)–(c) Measured angular distributions of SBS light for 1color, 2color+, and 2color− modes, respectively. (d) Statistics of measured FABS-SBS energy fraction. The red diamonds correspond to inner-cone averaging, the blue squares outer-cone averaging and the green stars octad averaging.

Fig. 3. Electron density n_e (in units of n_c) and electron temperature T_e (in keV) at t = 1.8 ns from the LARED-Integration code. The black solid lines indicate material boundaries, the black dashed rectangle indicates the LAP3D simulation box, and the blue dashed line indicate the ray where the CBET is evaluated in Fig. 4.

Fig. 4. (a) Coupling coefficient Γ_CBET along the ray indicated in Fig. 3 as a function of the wavelength shift Δλ = λ₂ − λ₁. (b) Relative energy gain of beam 2 as a function of Δλ.

Fig. 5. (a)–(c) Time-integrated angular distributions of SBS intensity obtained by LAP3D simulation, with the same linear color map used for all. (d)–(f) Angular distributions of common IAWs according to the theoretical prediction. The squares denote the backscattering IAWs of each beam. The circles denote all possible C82=28 IAWs shared by each pair of beams linked by a dashed line. (g)–(i) Time-integrated angular distributions of IAWs intensity obtained by LAP3D simulation, with the same linear color map used for all. (a), (d), and (g) are for the 1color mode, (b), (e), and (h) for the 2color+ mode, and (c), (f), and (i) for the 2color− mode. k₀ = 2π/λ₀ is the light wavenumber in vacuum.

Fig. 6. Sketch map of wave vector matching triangles when two SBS process share one IAW.