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Asymmetrically driven implosionsa)
a)Paper NI2 3, Bull. Am. Phys. Soc. 54, 179 (2009).
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10.1063/1.3354113
/content/aip/journal/pop/17/5/10.1063/1.3354113
http://aip.metastore.ingenta.com/content/aip/journal/pop/17/5/10.1063/1.3354113
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Experimental arrangement for the asymmetrically driven capsule implosion experiment. The hohlraum target is divided at the midplane into cavities “A” and “B.” Asymmetry of drive arises as a result of only one set of laser beams used (to heat either cavity A or cavity B) and because of the choice of wall material (and thus albedo) for the indirectly heated cavity. Implosion of the capsule is diagnosed using a titanium area backlighter (illuminated by six laser beams) and an x-ray framing camera (XRFC).

Image of FIG. 2.
FIG. 2.

(Top) laser spot positions and (bottom) laser intensity distribution at the hohlraum wall. The figure shows the case of laser beams driving both cavity A and cavity B, although in practice only one-half of the hohlraum is heated in the asymmetrically driven experiments. The ten highest-intensity spots at each end of the hohlraum arise from laser beams entering the hohlraum at an angle of 59° relative to the hohlraum axis; the five lower intensity spots arise from beams at 42° relative to axis. The white circles show the positions of the two diagnostic holes in the wall of the hohlraum. The region of wall enclosed by the green line is the area visible to the Dante diagnostic, which views through the LEH in cavity A. Dante is prevented from viewing inward through one of the diagnostic holes by a target shield (top figure).

Image of FIG. 3.
FIG. 3.

Laser intensity distribution at the hohlraum wall in the 2D NYM hydrocode model of the hohlraum. The figure shows the case of laser beams driving both cavity A and cavity B, although in practice only one-half of the hohlraum is heated.

Image of FIG. 4.
FIG. 4.

Electron density (top) and radiation temperature (bottom) from a NYM simulation of the asymmetrically driven Au–Au hohlraum. The regions outlined by the dashed line are those in which the mean radiation temperature is calculated to obtain the “internal temperature” of the hohlraum, as discussed in the text.

Image of FIG. 5.
FIG. 5.

Cavity temperature from the NYM hohlraum model compared with experimental data. In the NYM simulation temperature is inferred from the flux radiated in the direction of the Dante diagnostic (“flux-equivalent”) and from the internal temperature within a small volume in the cavity (“internal”). The experimental data are grouped as follows: (a) are data for Au–Au and Au–Al hohlraums in which Dante views the gold wall heated by the laser; (b) are data for an Au–Au hohlraum in which Dante views the indirectly heated gold wall; and (c) are for a Au–Al hohlraum in which Dante views the indirectly heated aluminum wall.

Image of FIG. 6.
FIG. 6.

Amplitude of the first four Legendre moments from two experiments (solid and open circles) using silica-aerogel foam witness balls of similar initial density and diameter. Solid circles: density and diameter. Open circles: density and diameter.

Image of FIG. 7.
FIG. 7.

Comparison of experiment and simulation of aerogel foam witness-ball implosion. The hydrodynamics are characterized by the amplitudes of the first four Legendre moments: (top) and (bottom). Solid circles are the experimental data ( initial density and initial diameter foam ball); crosses represent simulation. The lines are linear fits constrained to pass, at , through the initial radius or zero and are included only to show the trend of the data.

Image of FIG. 8.
FIG. 8.

Experimental and simulated radiographs of the implosion of the thin-shell glass capsule in an Au–Au hohlraum: (a), (c), (e), and (g) are at nominally 2.7, 3.1, 3.5, and 3.9 ns after the onset of the radiation drive; (b), (d), (f), and (h) are simulated radiographs from postprocessed NYM-PETRA simulations at 2.8, 3.0, 3.2, and 3.6 ns after the onset of the radiation drive (times chosen to match the equatorial diameter of the capsule, as shown in Figs. 9 and 11).

Image of FIG. 9.
FIG. 9.

Intensity distribution through the equatorial diameter of radiographs of the thin-shell glass capsule. The black curves show the inferred transmission through the (closing) diagnostic holes measured in a separate experiment using a hohlraum without a capsule. The red curves are from the experimental data of Fig. 8, and (a), (b), (c), and (d) are at 2.7, 3.1, 3.5, and 3.9 ns after the onset of the radiation drive. The intensity scale of the experimental data has been normalized to match the transmission through the diagnostic hole for regions of the image where absorption by the capsule is insignificant. The blue curves are taken from simulation also shown in Fig. 8, and in this case (a), (b), (c), and (d) are at 2.8, 3.0, 3.2, and 3.6 ns after the onset of the radiation drive (times chosen to match the equatorial diameter of the capsule). The dashed blue curve is taken directly from the postprocessed image, and the solid blue curve is from a postprocessed image that has been convolved with the spatial response function of the XRFC. The tick marks (green) show values of transmission chosen for the isotransmission contours in Figs. 11 and 12.

Image of FIG. 10.
FIG. 10.

Equatorial diameter of thin-shell glass capsules. The experimental data shown represent all hohlraum types: Au–Au and Au–Al. The simulated data record the equatorial diameter measured in postprocessed NYM-PETRA modeling of the experiment.

Image of FIG. 11.
FIG. 11.

Comparison of isotransmission contours from the experimental (red) and simulated (blue) data in Fig. 8. Times for (a)–(d) are as stated in Fig. 9, and in each case the contours are for . This value of transmission was chosen to identify approximately the position of the glass shell-ablator interface.

Image of FIG. 12.
FIG. 12.

Comparison of isotransmission contours from the experimental (red) and simulated (blue) data in Fig. 8. Times for (a)–(d) are as stated in Fig. 9, and the contours are for (a) , (b) , (c) , and (d) . These values of transmission were chosen to quantify the apparent diameter, and the position of the tip, of the jet in experiment and simulation.

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2010-05-04
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Asymmetrically driven implosionsa)
http://aip.metastore.ingenta.com/content/aip/journal/pop/17/5/10.1063/1.3354113
10.1063/1.3354113
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