Achieving Record Hot Spot Energies With Large Hdc Implosions On Nif In Hybrid-E

HYBRID-E is an inertial confinement fusion implosion design that increases energy coupled to the hot spot by increasing the capsule scale in cylindrical hohlraums while operating within the current experimental limits of the National Ignition Facility. HYBRID-E reduces the hohlraum scale at a fixed capsule size compared to previous HYBRID designs, thereby increasing the hohlraum efficiency and energy coupled to the capsule, and uses the cross-beam energy transfer (CBET) to control the implosion symmetry by operating the inner (23 degrees and 30 degrees) and outer (44 degrees and 50 degrees) laser beams at different wavelengths (Delta lambda > 0). Small case to capsule ratio designs can suffer from insufficient drive at the waist of the hohlraum. We show that only a small amount of wavelength separation between the inner and outer beams (Delta lambda 1-2 angstrom) is required to control the symmetry in low-gas-filled hohlraums (0.3mg/cm(3) He) with enough drive at the waist of the hohlraum to symmetrically drive capsules 1180 mu m in outer radius. This campaign is the first to use the CBET to control the symmetry in 0.3mg/cm(3) He-filled hohlraums, the lowest gas fill density yet fielded with Delta lambda > 0. We find a stronger sensitivity of hot spot P2 in mu m per Angstrom (40-50 mu m/angstrom wavelength separation) than observed in high-gas-filled hohlraums and previous longer pulse designs that used a hohlraum gas fill density of 0.6mg/cm(3). There is currently no indication of transfer roll-off with increasing Delta lambda, indicating that even longer pulses or larger capsules could be driven using the CBET in cylindrical hohlraums. We show that the radiation flux symmetry is well controlled during the foot of the pulse, and that the entire implosion can be tuned symmetrically in the presence of the CBET in this system, with low levels of laser backscatter out of the hohlraum and low levels of hot electron production from intense laser-plasma interactions. Radiation hydrodynamic simulations can accurately represent the early shock symmetry and be used as a design tool, but cannot predict the late-time radiation flux symmetry during the peak of the pulse, and semi-empirical models are used to design the experiments. Deuterium-tritium (DT)-layered tests of 1100 mu m inner radius implosions showed performance close to expectations from simulations at velocities up to similar to 360km/s, and record yields at this velocity, when increasing the DT fuel layer thickness to mitigate hydrodynamic mixing of the ablator into the hot spot as a result of defects in the ablator. However, when the implosion velocity was increased, mixing due to these defects impacted performance. The ratio of measured to simulated yield for these experiments was directly correlated with the level of observed mixing. These simulations suggest that reducing the mixing, e.g., by improving the capsule defects, could result in higher performance. In addition, future experiments are planned to reduce the coast time at this scale, delay between the peak compression and the end of the laser, to increase the hot spot Published under an exclusive license by AIP Publishing.convergence and pressure. To reduce the coast time by several hundred ps compared to the 1100 mu m inner radius implosions, HYBRID-E has also fielded 1050 mu m inner radius capsules, which resulted in higher hot spot pressure and a fusion energy yield of similar to 170 kJ.