High pressure solid state experiments on the NOVA laser Page: 4 of 14
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We are conducting experiments on the Nova laser  to study the plastic flow of metals at
high pressure and very high strain rates. Metal foils of copper are compressed by a factor of 1.5-
2.0 with staged shocks reaching peak pressures of about 3 Mbar. The Rayleigh-Taylor
instability is the observable "probe" in this experiment, with departures from classical (liquid)
behavior characterizing the material strength properties at high pressure and compression.
We present details in this paper of the hohlraum target design and x-ray drive characterization
for a Cu foil experiment. We also present calculations of the material state with this drive, and
results from instability growth experiments using thin Cu foils. We discuss the stability
boundaries for solid state plastic flow for the Nova experiments, and conclude with a discussion
of an improved experimental design using an Al foil where the foil remains solid throughout the
experiment and strength effects should be considerably enhanced.
The hydrodynamics experiments are conducted using an x-ray drive created in a cylindrical
gold hohlraum. This x-ray drive accelerates a metal foil payload by ablation of a brominated
polystyrene ablator layer. A preimposed sinusoidal modulation is located on the metal foil at the
embedded interface. The growth of this R-T unstable interface is then diagnosed by face-on x-ray
radiography using a gated x-ray framing camera. 
The target geometry is shown in Fig. 1. The hohlraum (Fig. la) is cylindrically symmetric
with internal shielding to prevent hard x-rays from preheating the Cu foil due to M-band
emission coming from the laser spots on the inner hohlraum wall. The hohlraum is 3.44 mm in
diameter, and 5.75 mm long. The laser entrance holes are 1.2 mm in diameter, and the holes in the
internal shields are 1.6 mm in diameter.
The hydrodynamics package (Fig. lb), consisting of a 20 Rm thick brominated polystyrene
(CH(Br)) foil pressed in contact with the metal foil, is mounted on the side of the hohlraum. The
CH(Br) ablator has a 3% atomic Br fraction to enhance the opacity to the soft x-rays. We
typically use 18-19 gm thick oxygen-free high conductivity Cu foils that have been rolled and
then machined to have a sinusoidal amplitude modulation.
backlighter foil t
backlighter beam x-ray heated cavity
Nova drive beam ternalbrominated plastic
axis - ------ - - - - -- - - - 2.5 pm_ 20 m
50 pm Cu foil
laser entrance hole aser heated cavity
x-ray drive CH(Br), Cu package
a) Hohlraum target b) Rayleigh-Taylor package
Fig. 1: (a) Schematic showing the internally shielded hohlraum and geometry for face-on
radiography. (b) Moduldated foil package mounted on the side of the hohlraum.
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Chandler, E A; Colvin, J D; Gold, D M; Hauer, A A; Kalantar, D H; Meyers, M A et al. High pressure solid state experiments on the NOVA laser, article, November 1, 1998; California. (digital.library.unt.edu/ark:/67531/metadc697040/m1/4/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.