Using laser entrance hole shields to increase coupling efficiency in indirect drive ignition targets for the National Ignition Facility

Journal Article · Mon May 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2196287· OSTI ID:20783155

Callahan, D A; Amendt, P A; Dewald, E L; Haan, S W; Hinkel, D E; Izurni, N; Jones, O S; Landen, O L; Lindl, J D; Pollaine, S M; Suter, L J; Tabak, M; Turner, R E ^[1]

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1. Lawrence Livermore National Laboratory, P.O. Box 808, Mail stop L-015, Livermore, California 94550 (United States)

Coupling efficiency, the ratio of the capsule absorbed energy to the driver energy, is a key parameter in ignition target designs. The hohlraum originally proposed for the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, S228 (2004)] coupled {approx}11% of the absorbed laser energy to the capsule as x rays. Described here is a second generation of the hohlraum target which has a higher coupling efficiency, {approx}16%. Because the ignition capsule's ability to withstand three-dimensional effects increases rapidly with absorbed energy, the additional energy can significantly increase the likelihood of ignition. The new target includes laser entrance hole (LEH) shields as a principal method for increasing coupling efficiency while controlling symmetry in indirect-drive inertial confinement fusion. The LEH shields are high Z disks placed inside the hohlraum on the symmetry axis to block the capsule's view of the relatively cold LEHs. The LEH shields can reduce the amount of laser energy required to drive a target to a given temperature via two mechanisms: (1) keeping the temperature high near the capsule pole by putting a barrier between the capsule and the pole; (2) because the capsule pole does not have a view of the cold LEHs, good symmetry requires a shorter hohlraum with less wall area. Current integrated simulations of this class of target couple 140 kJ of x rays to a capsule out of 865 kJ of absorbed laser energy and produce {approx}10 MJ of yield. In the current designs, which continue to be optimized, the addition of the LEH shields saves {approx}95 kJ of energy (about 10%) over hohlraums without LEH shields.

• OSTI ID: 20783155
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CAPSULES
COMPUTERIZED SIMULATION
COUPLING
DESIGN
EFFICIENCY
ELECTRON TEMPERATURE
ICF DEVICES
INERTIAL CONFINEMENT
ION TEMPERATURE
LASER-PRODUCED PLASMA
LASERS
LIGHT TRANSMISSION
PLASMA SIMULATION
SYMMETRY
THERMONUCLEAR IGNITION
THERMONUCLEAR REACTORS
THREE-DIMENSIONAL CALCULATIONS
US NATIONAL IGNITION FACILITY
X RADIATION
X-RAY SOURCES