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

In pinhole-assisted point-projection backlighting, pinholes are placed a sm all distance (of order 1 mm) away from the backlighter source to produce im ages with large field of view. Pinholes placed close to high-power backligh ter sources can vaporize and, if sufficiently small, close due to x-ray dri ven ablation, thereby potentially limiting the usefulness of this method. A study of streaked one-dimensional backlit imaging of 25 mum W wires using the OMEGA laser at the University of Rochester is presented. The pinhole cl osure time scale for 10 mum 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 fo r 5 mum pinholes is also presented. Successful wire imaging prior to pinhol e closure is clearly demonstrated. (C) 2001 American Institute of Physics.