Late-time radiography of beryllium ignition-target ablators in long-pulse gas-filled hohlraums

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

DOI:https://doi.org/10.1063/1.2181567· OSTI ID:20783152

Cobble, J A; Tierney, T E; Hoffman, N M; De Volder, B G; Swift, D C ^[1]

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

A multiple-laboratory campaign is underway to qualify beryllium as a fusion capsule ablator for the National Ignition Facility [Moses and Wuest, Fusion Sci. Technol. 43, 420 (2003)]. Although beryllium has many advantages over other ablator materials, individual crystals of beryllium have anisotropic properties, e.g., sound speed, elastic constants, and thermal expansion coefficients, which may seed hydrodynamic instabilities during the implosion phase of ignition experiments. Experiments based on modeling have begun at the OMEGA laser [Boehly, McCrory, Verdon et al., Fusion Eng. Design 44, 35 (1999)] to create a test bed for measuring instability growth rates with face-on radiography of perturbed beryllium samples with the goal of establishing a specification for microstructure in beryllium used as an ablator. The specification would include the size and distribution of sizes of grains and voids and the impurity content. The experimental platform is a 4 kJ laser-heated (for {approx}6 ns) hohlraum that is well modeled for radiation temperature and for shock pressure and breakout timing through the driven beryllium sample. A 1 atm methane gas fill has been used to maintain a clear line of sight through the hohlraum for radiography with acceptable plasma backscatter losses. The peak radiation temperature is 145 eV; the pressure early in the laser pulse is 1 Mbar for over 1 ns. Radiographs of sinusoidally perturbed copper-doped (0.9% by atom) beryllium samples have been obtained more than 10 ns after drive initiation. With the current laser drive, a growth factor approaching ten has been measured for initial 2.5 {mu}m perturbations with on-axis radiography.

• OSTI ID: 20783152
• Journal Information: Physics of Plasmas, Vol. 13, Issue 5; Other Information: DOI: 10.1063/1.2181567; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BERYLLIUM
CAPSULES
COMPUTERIZED SIMULATION
COPPER
DOPED MATERIALS
ELECTRON TEMPERATURE
EV RANGE
GROWTH FACTORS
ICF DEVICES
INSTABILITY GROWTH RATES
ION TEMPERATURE
LASERS
METHANE
OMEGA FACILITY
PLASMA
PLASMA DIAGNOSTICS
PLASMA HEATING
PLASMA INSTABILITY
PLASMA SIMULATION
PULSES
SHOCK WAVES
SOUND WAVES
THERMAL EXPANSION
THERMONUCLEAR IGNITION
THERMONUCLEAR REACTORS
US NATIONAL IGNITION FACILITY