Using target shimming to compensate for asymmetric drive in ICF implosions

Proton emission imaging has been used to measure the size and shape of the nuclear burn region in D$^{3}$He-filled capsules imploded with direct drive at the OMEGA laser facility. We have shown that intentional P2 asymmetry in the thickness of a plastic capsule shell, in combination with symmetric laser illumination, results in a P2 asymmetry in the burn region. We have also shown that intentional P2 asymmetry in the laser illumination of a symmetric capsule results in a P2 asymmetry in the burn region together with diminished burn yield. The measured relationship between shell-asymmetry amplitude and burn-asymmetry amplitude has been combined with the measured relationship between drive-asymmetry amplitude and burn-asymmetry amplitude, together with simple models, to prediction how the thickness of a capsule shell could be varied to compensate for asymmetric drive and produce symmetric implosions. We will discuss application of this prediction to both ``Polar Direct Drive'' and indirect drive without ``shine shields'' at the NIF, each of which could produce prolate implosions without target shimming. \textit{This work was supported in part by LLE, LLNL, the U.S. DoE, and the N.Y.State Energy Research and Development Authority.}