Impact of beam smoothing method on direct-drive target performance for the NIF

Joshua E. Rothenberg; Stephen V. Weber

doi:10.1117/12.294251

8 December 1997 Impact of beam smoothing method on direct-drive target performance for the NIF

Joshua E. Rothenberg, Stephen V. Weber

Proceedings Volume 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference; (1997) https://doi.org/10.1117/12.294251
Event: Second International Conference on Solid State Lasers for Application to ICF, 1996, Paris, France

Abstract

The impact of smoothing method on the performance of a direct drive target is modeled and examined in terms of its l-mode spectrum. In particular, two classes of smoothing methods are compared, smoothing by spectral dispersion (SSD) and the induced spatial incoherence (ISI) method. It is found that SSD using sinusoidal phase modulation results in poor smoothing at low l-modes and therefore inferior target performance at both peak velocity and ignition. This disparity is most notable if the effective imprinting integration time of the target is small. However, using SSD with more generalized phase modulation can result in smoothing at low l-modes which is identical to that obtained with ISI. For either smoothing method, the calculations indicate that at peak velocity the surface perturbations are about 100 times larger than that which leads to nonlinear hydrodynamics. Modeling of the hydrodynamic nonlinearity shows that saturation can reduce the amplified nonuniformities to the level required to achieve ignition for either smoothing method. The low l-mode behavior at ignition is found to be strongly dependent on the induced divergence of the smoothing method. For the NIF parameters the target performance asymptotes for smoothing divergence larger than approximately 100 (mu) rad.

Citation Download Citation

Joshua E. Rothenberg and Stephen V. Weber "Impact of beam smoothing method on direct-drive target performance for the NIF", Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); https://doi.org/10.1117/12.294251

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