Development of a high resolution x-ray radiography platform to study hydrodynamic instabilities in high energy density conditions

High resolution x-ray radiography (<10 µm resolution) in high-energy-density (HED) conditions will enable the study of fine structures present in hydrodynamic instabilities. In order to image the detailed dynamics occurring during the growth of these instabilities, the radiography platform needs to provide high spatial and temporal resolution on the order of ~5 µm and ~100 ps, respectively. We report on the development of such a platform at the National Ignition Facility (Lawrence Livermore National Laboratory) using doubly-bent crystal x-ray optics. By simultaneously characterizing the spatial resolution throughout the ~2mm deep volume of the subsequent HED experiments, the radiograph fluence and the backlighter temporal profile, we are able to optimize an integrated measurement platform. The highest spatial resolution so far is achieved by using a toroidal crystal coupled to x-ray film, while the temporal resolution is controlled by gating the radiograph via the x-ray source. We present our investigation of different short pulse x-ray backlighter configurations driven with either the ARC laser, NIF laser beams or a combination of both to find an optimized solution balancing the length and fluence of the emitted x-ray pulse. The resulting imaging platform configuration will be employed to radiograph shock-driven hydrodynamic instabilities to validate large-eddy simulations of mixing plasmas.

Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-866027.