Laser irradiance scaling in polar direct drive implosions on the National Ignition Facility

Polar-direct-drive experiments conducted at the National Ignition Facility [E. I. Moses, Fusion Sci. Technol. 54, 361 (2008)] performed at laser irradiance between 1 and 2×1015 W/cm2 exhibit increased hard x-ray emission, decreased neutron yield, and reduced areal density as the irradiance is increa...

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Bibliographic Details
Published in:Physics of plasmas 2015-09, Vol.22 (9)
Main Authors: Murphy, T. J., Krasheninnikova, N. S., Kyrala, G. A., Bradley, P. A., Baumgaertel, J. A., Cobble, J. A., Hakel, P., Hsu, S. C., Kline, J. L., Montgomery, D. S., Obrey, K. A. D., Shah, R. C., Tregillis, I. L., Schmitt, M. J., Kanzleiter, R. J., Batha, S. H., Wallace, R. J., Bhandarkar, S. D., Fitzsimmons, P., Hoppe, M. L., Nikroo, A., Hohenberger, M., McKenty, P. W., Rinderknecht, H. G., Rosenberg, M. J., Petrasso, R. D.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Computer simulation
Electron transport
Energy transfer
experiment design
hot carriers
Ignition
Implosions
Irradiance
Laser beams
Lasers
Neutron flux
neutrons
Plasma physics
Symmetry
X-ray imaging
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Summary:Polar-direct-drive experiments conducted at the National Ignition Facility [E. I. Moses, Fusion Sci. Technol. 54, 361 (2008)] performed at laser irradiance between 1 and 2×1015 W/cm2 exhibit increased hard x-ray emission, decreased neutron yield, and reduced areal density as the irradiance is increased. Experimental x-ray images at the higher irradiances show x-ray emission at the equator, as well as degraded symmetry, that is not predicted in hydrodynamic simulations using flux-limited energy transport, but that appear when non-local electron transport together with a model to account for cross beam energy transfer (CBET) is utilized. The reduction in laser power for equatorial beams required in the simulations to reproduce the effects of CBET on the observed symmetry also reproduces the yield degradation consistent with experimental data.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4931092