Hydrodynamic assessment of direct-drive inertial confinement fusion with mixed 2ω−3ω lasers

Ablation with mixed 2ω–3ω lasers is investigated as a drive strategy for direct-drive inertial confinement fusion, balancing hydrodynamic drive efficiency, ablative stabilization, and facility-level energy constraints. One-dimensional radiation-hydrodynamic simulations of planar CH targets are performed with the FLASH code [Fryxell et al., Astrophys. J., Suppl. Ser. 131, 273 (2000)], varying the total incident intensity from 100 to 1600 TW/cm2 and the 3ω intensity fraction f3ω from 0 to 100%. Increasing f3ω raises the ablation pressure and the ablation velocity, lowers the maximum linear Rayleigh–Taylor instability (RTI) gain evaluated with a Takabe-type model, and reduces the target-incident energy required to accelerate a foil to 300 km/s, because the 3ω light deposits its energy closer to the dense ablation region and enhances conductive heat transport toward the ablation front. When representative frequency-conversion efficiencies are folded into the energy budget, the required fundamental-frequency (1ω) energy becomes non-monotonic in f3ω at high intensity, with an interior minimum near f3ω≈20%–30% lying below both single-color drives. Because the energy landscape around this minimum is shallow, f3ω can be raised moderately above it to strengthen RTI stabilization and widen the sub-threshold window for two-plasmon decay at a 1ω energy cost of only a few percent. These results identify f3ω≈30%–50% as a preferred operating window and establish the wavelength-mixing ratio as an additional design degree of freedom for direct-drive target optimization.