Fig. 1. (a) Schematic of N-L configuration in a direct–drive scheme, with the red box indicating the simulation domain. (b) Schematic of simulation setup. (c) B_z for case I at t = 1.0 ps. (d) Density perturbation of electrons n_p for case I at t = 2.0 ps. In (d), a Gaussian filter G(x,y)=e−(x2+y2)/2σ2/2πσ2 with σ = 2 is applied to reduce background noise.

Fig. 2. (a) Time and space evolution of ⟨np2⟩y in case I, with the pump depletion of Beam-N marked by the blue solid line and n_cr/4 by the white dashed line. Here, the brackets ⟨…⟩_y denote averaging over y. (b) Time and space evolution of ⟨np2⟩y in case II. (c) Time evolution of ⟨np2⟩ in cases I–V, where ⟨np2⟩ is the averaged value of np2 over the whole simulation domain. (d) Time evolution of ⟨np2⟩x in k_y space in case I. Here, ⟨np2⟩x denotes np2 averaged over x after Fourier transformation of n_p along the y direction.

Fig. 3. (a) n_p of case I at t = 2.0 ps in k_x–k_y space, with the wave vectors of the EPWs and of Beam-L near n_e = 0.25n_cr denoted by the green and black arrows, respectively. The red curves represent the maximum growth curves of TPD in the homogeneous plasma of Beam-L, while the blue curves depict the maximum growth curves of Beam-N. (b) Time evolution of ⟨np2⟩x in k_y space in case VI. Here, the black dashed line at t = 2.0 ps indicates the switch between Beam-L and Beam-N. (c) n_p of case VI at t = 2.0 ps in k_x–k_y space, with the difference in distribution compared with case I indicated by the blue circle. (d) n_p of case VI at t = 3.0 ps in k_x–k_y space, where the green and black arrows are the wave vectors of the EPWs and of Beam-N near n_e = 0.25n_cr, respectively. Here, the green solid and dashed arrows are the wave vectors of EPWs excited respectively before and after the incidence of Beam-N and the blue arrows represent the convective amplification process of the EPWs. (e) Time and space evolution of n_p with k_y = 0.07ω₀/c and of n_p along the x direction at t = 2 ps (black line) and t = 4.5 ps (red line) in case VI. (f) Time and space evolution of n_p with k_y = 0.9ω₀/c and of n_p along the x direction at t = 2 ps (black line) and t = 2.2 ps (red line) in case VI.

Fig. 4. (a) Wave-vector matching condition of the absolute instability of Beam-L. Here, k₁ and k₂ (green arrows) are the wave vectors of the paired daughter EPWs, while k_L (lack arrow) is the local wave vector of Beam-L. The red dashed curves represent the maximum growth curves of TPD in the homogeneous plasma of Beam-L. (b) Wave-vector matching condition of the convective instability of Beam-N. Here, k₁ and k₃ (green arrows) are the wave vectors of the paired daughter EPWs, while k_N (black arrow) is the local wave vector of Beam-N. The blue dashed curves are the maximum growth curves of Beam-N. (c) Wave-vector matching condition of the collective instability in the N-L system. Here, k₁ (red arrow) represents the EPW collectively driven by both Beam-L and Beam-N.

Fig. 5. (a) n_p of case I with mobile ions at t = 4.0 ps in k_x–k_y space, with the maximum growth curves of TPD in the homogeneous plasmas of Beam-L and Beam-N given by the red and blue curves, respectively; (b) n_p of case VII with fixed ions at t = 4.0 ps in k_x–k_y space. (c) Time evolution of ⟨npH2⟩y in case I, where n_pH is the density perturbation of H ions.

Fig. 6. (a) Time evolution of α for the left (red) and right (blue) boundaries and both sides (orange) in case I. Here, α represents the instantaneous energy flux carried by hot electrons (≥50 keV) monitored on the boundaries and has been normalized to the incident laser energy flux including both beams. (b) α_R in cases I–V. Here, α_R is the α for the right boundary and represents the hot electrons moving to the higher-density region. (c) Fitted temperatures of hot electrons T_hot in cases I, II, and V. (d) Charge density distribution of hot electrons in the p_x–x phase space at t = 6 ps in case I. The staged acceleration of electrons is indicated by the blue arrow.