Laboratory for Laser Energetics
Friday, November 22, 2019
Laser-direct-drive inertial confinement fusion involves the uniform laser irradiation of a plastic spherical shell target containing a thin layer of cryogenic, thermonuclear fuel [i.e., deuterium (D) and tritium (T)] with symmetrically arranged high-intensity overlapping beams to implode the target and form a central hot-spot fusion plasma. The best-performing implosions on the 60-beam, 30-kJ, 351‑nm OMEGA laser [V. Gopalaswamy et al., Nature 565, 581 (2019)] couple to the hot-spot internal energy (Ehot spot) at peak neutron production up to Ehot spot = 1 kJ out of an incident laser energy ELaser ~ 29 kJ with ~18 kJ absorbed by the target. When hydrodynamically scaled to ELaser =1.9 MJ available (1.1 MJ absorbed) on the National Ignition Facility (NIF), these implosions scale to Ehot spot = 60 kJ and the yield of Y ~ 500 kJ with yield amplification due to alpha heating of ~2.7x and scaled-ignition parameter cno-a = 0.73. Three-dimensional diagnostics are essential to study multidimensional effects on hot-spot formation of DT cryogenic implosions caused by target and laser low-mode perturbations. Nonuniformities in the imploding shell are characterized until the end of the acceleration phase using a four-axis, gated x-ray imaging system, and the measured implosion asymmetries during the acceleration phase are related to the stagnation phase. Three-dimensional nuclear and x-ray diagnostics are being developed to infer hot-spot flow velocity, spatial variations in the compressed areal density, electron and ion temperatures, and the shape of the hot spot. Progress in the diagnosis of low-mode multidimensional effects on hot-spot formation of OMEGA DT cryogenic implosions will be reported.
This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority.