IGNITION TARGET DESIGN AND ROBUSTNESS STUDIES FOR THE NATIONAL-IGNITION-FACILITY

Recent results are presented from two-dimensional LASNEX [G. B. Zimmer man and W. L. Kruer, Comments Plasmas Phys. Controlled Thermonucl. Fus ion 2, 51 (1975)] calculations of the indirectly driven hohlraum and i gnition capsules proposed for the National Ignition Facility (NIF). Th e calculations concentrate on two capsule designs, the baseline design that has a bromine-doped plastic ablator, and the beryllium design th at has a copper-doped beryllium ablator. Both capsules have a cryogeni c fuel layer. Primary emphasis in these calculations is placed upon ro bustness studies detailing various sensitivities. Because of computer modeling limitations these studies fall into two categories: those per formed with integrated modeling where the capsule, hohlraum, and laser rays all are modeled simultaneously with the laser power levels as th e only energy input; and those performed in a capsule-only mode where an externally imposed radiative flux is applied to the exterior of the capsule, and only the capsule performance is modeled. Integrated mode ling calculations address sensitivities to, e.g., the laser pointing; among other things, capsule-only calculations address yield degradatio n due to the growth of hydrodynamic instabilities seeded by initial su rface roughnesses on the capsules. Limitations of the calculational mo dels and directions for future research are discussed. The results of the robustness studies performed to date enhance the authors' confiden ce that the NIF can achieve ignition and produce 10-15 MJ of capsule y ield with one or more capsule designs. (C) 1996 American Institute of Physics.