Indirect-drive noncryogenic double-shell ignition targets for the National Ignition Facility: Design and analysis

Analysis and design of indirect-drive National Ignition Facility double-shell targets with hohlraum temperatures of 200 eV and 250 eV are presented. The analysis of these targets includes the assessment of two-dimensional radiation asymmetry and nonlinear mix. Two-dimensional integrated hohlraum simulations indicate that the x-ray illumination can be adjusted to provide adequate symmetry control in hohlraums specially designed to have high laser-coupling efficiency [Suter et al., Phys. Plasmas 7, 2092 (2000)]. These simulations also reveal the need to diagnose and control localized 10–15 keV x-ray emission from the high-Z hohlraum wall because of strong absorption by the high-Z inner shell. Preliminary estimates of the degree of laser backscatter from an assortment of laser–plasma interactions suggest comparatively benign hohlraum conditions. The application of a variety of nonlinear mix models and phenomenological tools, including buoyancy-drag models, multimode simulations and fall-line optimization, indicates a possibility of achieving ignition, i.e., fusion yields greater than 1 MJ. Planned experiments on the Omega laser will test current understanding of high-energy radiation flux asymmetry and mix-induced yield degradation in double-shell targets.