Design of Inverted Corona neutron sources for NIF

We describe the design of gas-filled Inverted Corona neutron sources for the National Ignition Facility (NIF). In an Inverted Corona target, the inside of a spherical shell is illuminated by lasers. The ablating plasma from the inner liner launches a converging shock wave into a fusion fuel gas, generating neutrons in a similar manner to an exploding pusher. Targets were initially designed in 2D using the ICF code Hydra. Later 1D simulations with the hybrid Particle In Cell (PIC) code Chicago predicted non-Maxwellian ion distributions and species interpenetration in the plasma . Chicago simulations matched data trends in Omega experiments that Hydra could not reproduce. Recently, the targets have been simulated in 1D using the ICF code Ares. With its plasma diffusion model, Ares can reproduce some of the species mixing observed in Chicago. We are currently developing a 2D Ares model for making practical design choices for future NIF experiments, such as finding the optimum layer thickness, window thickness, and gas-fill density. The experimental design must also consider the debris wind, which can restrict the stand-off distance of objects under test.