High Energy Back-lighting Coupled with an Offset and Shielded Collecting Optic

At the National Ignition Facility (NIF), we aim to radiograph rapidly changing, complex, and dense objects for several research goals. This requires a small high-energy and bright x-ray source. The Advanced Radiographic Capability (ARC) at the NIF and the Omega Extended Performance (EP) laser at the Laboratory for Laser Energetics (LLE) provide short pulse, high energy laser beams capable of irradiating backlighter foils, blocks, or wires to produce intense, high-energy x-ray (> 100keV) pulses. To enhance the coupling of the laser energy to the backlighter, a collecting optic shaped as a parabolic cone or a parabolic u-pipe has been employed. In most of these configurations, the optic is in direct contact with the backlighting material which results in the optic becoming an extended x-ray emitting source. In imaging applications where the resolution is a vital consideration and the detector responds to the x-rays emitted by the optic, an alternate setup is required that mitigates the signal from the optic. Here, we will detail a new configuration where the compound parabolic concentrator (CPC) optic is offset from a Tungsten wire backlighter and a Tantalum shield blocks the signal emanating from the CPC. Using the results from a series of experiments at Omega EP, we narrow the parameters necessary for a 20µm resolution x-ray source enhanced with a collecting optic.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-836630