10 and 5 μm pinhole-assisted point-projection backlit imaging for the National Ignition Facility

In pinhole-assisted point-projection backlighting, pinholes are placed a small distance (of order 1 mm) away from the backlighter source to produce images with large field of view. Pinholes placed close to high-power backlighter sources can vaporize and, if sufficiently small, close due to x-ray driven ablation, thereby potentially limiting the usefulness of this method. A study of streaked one-dimensional backlit imaging of 25 μm W wires using the OMEGA laser at the University of Rochester is presented. The pinhole closure time scale for 10 μm pinholes placed 0.45 and 1 mm distant from a 0.6 TW Ti backlighter is 1.3 and 2.2 ns, respectively. Similar time scales for 5 μm pinholes is also presented. Successful wire imaging prior to pinhole closure is clearly demonstrated.