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High-resolution backlighters for high energy density experiments
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Image of FIG. 1.
FIG. 1.

Examples of high-energy-density experiments that require high-energy backlighters on NIF. The left panel is a configuration for a material strength experiment where the ripple growth factors are measured via face-on radiography. The right panel is the mid- to high-Z capsule implosion experiments where capsule implosion symmetry will be studied. The simulated radiography of these targets shows that all require radiography due to the high areal density thickness of the samples.

Image of FIG. 2.
FIG. 2.

Sketch of point projection radiography using thin 1D microfoil sources and wire microwire source for 2D radiography. For high-energy radiography, the x-ray radiation is confined within the fluorescent target material. The small size of the targets produces radiographs with high spatial resolution.

Image of FIG. 3.
FIG. 3.

Laser spot image at its best focus and in a defocused condition where the target is placed toward the parabola. 50% of the laser energy is contained within a radius at the best focus and within a radius for the defocused case.

Image of FIG. 4.
FIG. 4.

Titan experimental setup. Two different types of imaging devices (Image Plate and /CCD imagers) and two different spectrometers (single-photon counting camera and curved Qz crystal spectrometer) were employed to measure spatial resolution and conversion efficiencies.

Image of FIG. 5.
FIG. 5.

Fabricated microfoil and microwire targets. These are examples used for Au radiography. We have tested Mo, Ag, and Sm targets that are fabricated with similar geometries. The radiographs are taken along an axis providing an edge-on view of the microwire or micro dot.

Image of FIG. 6.
FIG. 6.

The results of Ag radiography with microwire target. The diagonal sections with , , and grids are denoted. The central grid region is well resolved.

Image of FIG. 7.
FIG. 7.

MTF analysis of the radiographs in Fig. 5. The point spread function is obtained by finding the best match of the data with an ideal grid image convoluted with the point spread function. We obtain an MTF for periods with the Titan laser. Improved MTFs are expected with higher-energy lasers.

Image of FIG. 8.
FIG. 8.

Test target for Au radiography . The target is made of thick Au material with edges machined using EDM.

Image of FIG. 9.
FIG. 9.

Radiography results from the Au microflag and microwire targets. The 1D and 2D nature of the images are clear. The edges were fit to an edge spread function (see text).

Image of FIG. 10.
FIG. 10.

Difference in yield between microflag and microwire targets measured by the Qz crystal spectrometer. The histograms are continuum background subtracted. After accounting for the difference in laser energy, the ratio in the yield between these two types of targets is .

Image of FIG. 11.
FIG. 11.

yield measurements using the single-photon counting camera (a) and the curved Qz crystal spectrometer (b) for various target materials. We measure absolute conversion efficiencies using the single-photon counting camera at and relative conversion efficiencies using Qz spectrometer at . By normalizing the conversion efficiencies at , we measure the absolute efficiencies from .

Image of FIG. 12.
FIG. 12.

Measurements of the conversion efficiency of different target materials. The two different data points correspond to the two different measurements of the same target types. The ITS Monte Carlo simulation is plotted as the solid line.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: High-resolution 17–75keV backlighters for high energy density experiments