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We have successfully demonstrated a 7.5 ns duration pinhole-apertured backlighter at the Omega laser facility. Pinhole-apertured point-projection backlighting for 8 ns will be useful for imaging evolving features in experiments at the National Ignition Facility. The backlighter consisted of a 20 μm diameter pinhole in a 75 μm thick Ta substrate separated from a Zn emitter (9 keV) by a 400 μm thick high-density carbon piece. The carbon prevented the shock from the laser-driven surface from reaching the substrate before 8 ns and helped minimize x-ray ablation of the pinhole substrate. Grid wires in x-ray framing camera images of a gold grid have a source-limited resolution significantly smaller than the pinhole diameter due to the high aspect ratio of the pinhole, but do not become much smaller at late times. [ABSTRACT FROM AUTHOR]

The article discusses the techniques of using ray tracing to guide the construction of freeform mirrors which can be applied to a variety of problems. The U.S. Defense Advanced Research Projects Agency has designed pinhole camera which allows the light to enter through single point to project three-dimensional image plane. Based on mathematical analysis, the images produced in a camera is distorted if a curved mirror intervenes between object and hole.

We have fielded a hard x-ray (>100 keV) imager with high aspect ratio pinholes to measure the spatially resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions and are a source of preheat to the deuterium-tritium fuel. First measurements show that hot electron preheat does not limit obtaining the fuel areal densities required for ignition and burn. [ABSTRACT FROM AUTHOR]