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Magneto-Rayleigh-Taylor experiments on a MegaAmpere linear transformer driver
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10.1063/1.3690088
/content/aip/journal/pop/19/3/10.1063/1.3690088
http://aip.metastore.ingenta.com/content/aip/journal/pop/19/3/10.1063/1.3690088

Figures

Image of FIG. 1.
FIG. 1.

(Color) CAD renderings of (a) the load assembly and (b) the transmission line/vacuum hardware. The tensioning system is removed from (b) for clarity.

Image of FIG. 2.
FIG. 2.

(Color online) The planar geometry used in development of MRT theory and experimental load design. For the experiment, the large offset case corresponded to the initial foil position x0 < 0, and the small offset case corresponded to the initial foil position x0 ≈ 0.

Image of FIG. 3.
FIG. 3.

(Color online) Laser timings and current trace overlays for (a) the large and (b) the small offset cases. Circles indicate an image from camera 1 and squares indicate an image from camera 2, which was delayed 9 ns.

Image of FIG. 4.
FIG. 4.

(Color) A sample laser shadowgraphy image at peak current for the large offset case, shot 301 at 199 ns and 603 kA, showing the region-of-interest used for the MRT growth rate analysis. The dashed yellow line represents the approximate location of pre-shot center of foil. The dashed red line represents the midplane between the original anode plate locations, which are shown in solid cyan. The magenta boxes represent the extents of plasma used in the analysis. The blue (left), green (middle), andred (right) lines within the magnified region-of-interest represent the locations corresponding to 85%, 50%, and 15% laser transmission thresholds, respectively. The figure-of-merit used to characterize the amplitude of the MRT structure was defined as the distance between the 85% and 15% thresholds.

Image of FIG. 5.
FIG. 5.

(Color) A laser shadowgraph image sequence for the large offset case: (a) shot 309 at 38 ns and 215 kA, (b) shot 310 at 90 ns and 468 kA, (c) shot 306 at 129 ns and 529 kA, and (d) shot 337 at 179 ns and 602 kA. The horizontal aspect ratio has been stretched and the contrast enhanced to aid in viewing the instability development. The yellow lines represent the center of the pre-shot foil location, the dashed red line represents the center plane between the return current electrodes, and the solid cyan lines represent the original return current electrode locations.

Image of FIG. 6.
FIG. 6.

The wavelength spectra taken from the left interface for the large offset case for (a) shot 309 at 38 ns and 215 kA and (b) shot 301 at 199 ns and 603 kA. The early time spectra (a) is dominated by the short wavelength structure from the ET instability (λ ∼ 0.4 mm), whereas the late time spectra (b) contains the longer wavelength MRT (λ > 0.7 mm) modulating the shorter wavelength structure.

Image of FIG. 7.
FIG. 7.

(Color online) The experimental figure-of-merit measurements characterizing the MRT amplitude for the large offset (a) left side and (b) right side. The red dashed line represents the empirical fit used to determine the average MRT growth rate.

Image of FIG. 8.
FIG. 8.

(Color online) The experimental figure-of-merit measurements characterizing the MRT amplitude for the small offset (a) left side and (b) right side. The red dashed line represents the empirical fit used to determine the average MRT growth rate.

Image of FIG. 9.
FIG. 9.

(Color online) Shadowgraphs with the probe laser parallel to foil current (i.e., along the y-direction in Fig. 2): (a) pre-shot and (b) 190 ns, 0.6 MA. False color has been added in (b) to aid the eye. MRT anisotropy is apparent by comparing Figs. 4 and 9(b).

Tables

Generic image for table
Table I.

A summary of MRT observations and e-folding times.

Generic image for table
Table II.

A direct measurement of the interface accelerations for laser transmission threshold locations as illustrated in Fig. 4.

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/content/aip/journal/pop/19/3/10.1063/1.3690088
2012-03-05
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Magneto-Rayleigh-Taylor experiments on a MegaAmpere linear transformer driver
http://aip.metastore.ingenta.com/content/aip/journal/pop/19/3/10.1063/1.3690088
10.1063/1.3690088
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