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Shock propagation in deuterium-tritium-saturated foam
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View: Figures


Image of FIG. 1.
FIG. 1.

Density profiles at 4, 8, and 12 ps for a Mach-24 shock interacting with a CH fiber. The density ratio is 4:1.

Image of FIG. 2.
FIG. 2.

The fraction of fiber mass that lies outside the original fiber radius of the fiber’s center of mass as a function of time. As the fiber material is mixed with the ambient material, it is flung outside of its original boundaries. The solid line is a single fiber with a 4:1 density ratio with the interfiber material (see Fig. 1). The dashed line is from a simulation of fiber destruction in the presence of other fibers. Taking the 75% mark as an arbitrary measure of fiber destruction, the fiber is destroyed after for a single fiber and in the presence of other fibers, though in this case the fiber destruction is much more thorough.

Image of FIG. 3.
FIG. 3.

The total density (a) and CH density (b) at 96 ps for an 8-Mbar shock driven into wetted foam. The dotted line in the second panel frame shows the location of the shock front.

Image of FIG. 4.
FIG. 4.

The total mass density (gray scale) and the mass density (lines) of material from a “tagged” fiber initially at (1.93, ). The contour levels for the tagged fiber correspond to 10%, 32.5%, 55%, and 77.5% of the peak tagged-fiber density. The frames are from 30, 35, 45, 60, 80, and 100 ps.

Image of FIG. 5.
FIG. 5.

The -averaged density (a), pressure (b), and velocity at 300 ps for a simulation.

Image of FIG. 6.
FIG. 6.

The mix region (shaded), pusher, and unshocked material are shown as a function of time, in the frame of the main shock. The time averages are computed of the flow variables in the mix region between the shock and the pusher as functions of the distance behind the shock. For instance, the time average at a distance behind the shock is found by averaging from time to time .

Image of FIG. 7.
FIG. 7.

The rms variations of the time-averaged density (a), pressure (b), fraction of kinetic energy (in the preshock frame) (c), and vertical velocity (d) as functions of the distance behind the shock. These show a decay length comparable to a micron, for this foam density.

Image of FIG. 8.
FIG. 8.

The decay length behind the shock as a function of foam density. The decay length is approximated by the scale length of the time-averaged decay of pressure variations just behind the shock. The error bars are given by the uncertainty in the exponential fit.

Image of FIG. 9.
FIG. 9.

The vorticity is shown as the shock reaches for three dry-foam densities: 25, 75, and 125 mg/cc. The average interfiber distance is the same in all three cases, while the fiber radius is larger for higher foam densities.

Image of FIG. 10.
FIG. 10.

The time- and space-averaged density (a), pressure (b), ratio of kinetic to total energy (in the preshock frame) (c), and vertical velocity (d) as functions of the distance behind the shock front. The values given by the Rankine–Hugoniot jump conditions for a homogeneous mixture of the same density are also shown (dashed lines).

Image of FIG. 11.
FIG. 11.

The target gain as a function of first-shock mistiming for a high-gain, wetted-foam, direct-drive NIF target design.

Image of FIG. 12.
FIG. 12.

The rms shock-front perturbation amplitude as a function of shock position for a simulation consisting of of wetted foam and of DT. The transverse simulation size is .

Image of FIG. 13.
FIG. 13.

The density (a) and pressure (b) as functions of distance for a particular instance in time, for a simulation of a shock driven through wetted foam by a DT pusher. An equivalent homogeneous simulation is shown (dashed) as well as a simulation (dotted) in which pusher and foam are replaced by a homogeneous mixture with the same average density as the wetted foam.

Image of FIG. 14.
FIG. 14.

The magnitude of the inverse of the pressure scale length for a wetted-foam ignition target design in which the wetted-foam layer is overfilled, forming an external layer of DT. Shocks and rarefaction waves are labeled.

Image of FIG. 15.
FIG. 15.

The magnitude of the inverse of the pressure scale length for a wetted-foam ignition target design with an external layer of CH.

Image of FIG. 16.
FIG. 16.

The density (a) and pressure (b) as functions of distance are shown for a particular time, along with the values from a simulation of a corresponding homogeneous medium with the same avearge preshock density (dashed). The inflow boundary conditions correspond to a CH pusher.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Shock propagation in deuterium-tritium-saturated foam