An initial assessment of three-dimensional polar direct drive capsule asymmetries for implosions at the National Ignition Facility

Journal Article · Sun Jan 15 04:00:00 EST 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3671972· OSTI ID:22043587

Krasheninnikova, Natalia S; Finnegan, Sean M; Schmitt, Mark J ^[1]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

The National Ignition Facility (NIF) provides a unique opportunity to study implosion physics with nuclear yield. The use of polar direct drive (PDD) [A. M. Cok, R. S. Craxton, and P. W. McKenty, Phys. Plasmas 15, 082705 (2008)] provides a simple platform for the experimental studies without expensive optics upgrades to NIF. To determine the optimum PDD laser pointing geometry on NIF and provide a baseline for validating inertial confinement fusion codes against experiments for symmetric and asymmetric implosions, computer simulations using the 3D radiation-hydrodynamics code hydra[M. M. Marinak, R. E. Tipton, O. L. Landen, T. J. Murphy, P. Amendt, S. W. Haan, S. P. Hatchett, C. J. Keane, R. McEachern, and R. Wallace, Phys. Plasmas 3, 2070 (1996)] were preformed. The upper hemisphere of a DT-filled CH capsule was imploded by 96 NIF beams in a PDD configuration. Asymmetries in both polar and equatorial directions around the capsule were observed, with the former dominating the latter. Analysis of the simulation results indicates that the lack of symmetry in the initial power density profile (during the first 200 ps of the implosion) is a primary cause of late-time asymmetry in the implosion as well as decreased yield. By adjusting the laser pointings, the symmetry and total neutron yield were improved. Simulations with dropped quads (four of the NIF laser system's 192 beamlines) without repointing worsen the overall symmetry by a factor of 10 (with respect to rms radial variation around the capsule) and reduce neutron yield by a factor of 2. Both of these degraded implosion characteristics are restored by azimuthal repointing of the remaining quads.

• OSTI ID: 22043587
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 1 Vol. 19; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ASYMMETRY
CAPSULES
COMPUTERIZED SIMULATION
CONFIGURATION
EXPLOSIONS
HYDRODYNAMICS
IMPLOSIONS
INERTIAL CONFINEMENT
LASER RADIATION
LIGHT TRANSMISSION
NEUTRONS
OPTICS
PLASMA
PLASMA SIMULATION
POWER DENSITY
SYMMETRY
THREE-DIMENSIONAL CALCULATIONS
US NATIONAL IGNITION FACILITY