Laser–plasma instabilities driven by 1 ω0 pulses at shock ignition conditions

Recent experiments using 1ω0 (λ0=1.314 μm) laser pulses at the PALS facility have demonstrated the excitation of multiple parametric instabilities. At peak intensities (I∼1016 W cm−2), the combination of high irradiance (Iλ2) and electron temperatures (∼ 3–4 keV) creates plasma conditions relevant to shock ignition. We present two-dimensional particle-in-cell simulations of laser–plasma instabilities at both low (∼1015 W cm−2) and high (∼1016 W cm−2) intensities. The simulations incorporate flow, density, and temperature profiles obtained from hydrodynamic modeling, as well as the effects of Coulomb collisions. In both regimes, stimulated Brillouin scattering emerges as the primary mechanism for backscattered electromagnetic radiation. At low intensity, two-plasmon decay (TPD) drives electron plasma wave activity, while stimulated Raman scattering (SRS) is suppressed by the short density scale length (Ln), limiting convective gain. At higher intensity, the onset of laser beam filamentation leads to a reduction in TPD activity, while the increased Ln facilitates the excitation of SRS within the resulting filaments. The resulting hot-electron populations follow thermal-like distributions with effective temperatures ranging between 17 and 37 keV with respect to laser intensity. The fraction of laser energy converted into electrons with E>100 keV increases from 0.2% to 0.7% between low and high intensity. In the low-intensity regime, resonance absorption near the critical density also enhances the hot-electron flux at the simulation boundary, especially for electrons with E≤100 keV. This contribution diminishes at higher intensities, where SRS near the quarter-critical density becomes the dominant source of hot-electron generation.