Shock structuring due to fabrication joints in targets

The use of copper-doped beryllium ablators on National Ignition Facility [J . A. Paisner , Laser Focus World 30, 75 (1994)] targets, in place of plasti c, can require the bonding together of hemispheres with a joint of differin g composition. Indirect drive experiments have been conducted on the Nova l aser [J. L. Emmet, W. F. Krupke, and J. B. Trenholme, Sov. J. Quantum Elect ron. 13, 1 (1983)], and the resulting shock structuring compared with code simulations. It is concluded that one of the available codes, the RAGE code [R. M. Baltrusaitis , Phys. Fluids 8, 2471 (1996)] provides useful insight into the effect of joints. This code is then employed to obtain a physical picture of the shock front nonuniformity in terms of a secondary rarefacti on and an oblique shock interacting with the main shock that propagates in the absence of the joint. A simple analysis reinforces this picture.(C) 199 9 American Institute of Physics. [S1070-664X(99)03008-6].