Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absor...

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Veröffentlicht in:Physics of plasmas 2018-05, Vol.25 (5)
Hauptverfasser: Marozas, J. A., Hohenberger, M., Rosenberg, M. J., Turnbull, D., Collins, T. J. B., Radha, P. B., McKenty, P. W., Zuegel, J. D., Marshall, F. J., Regan, S. P., Sangster, T. C., Seka, W., Campbell, E. M., Goncharov, V. N., Bowers, M. W., Di Nicola, J.-M. G., Erbert, G., MacGowan, B. J., Pelz, L. J., Moody, J., Yang, S. T.
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Sprache:eng
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Zusammenfassung:Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light–changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.5022181