Short pulse, high resolution, backlighters for point projection high-energy radiography at the National Ignition Facility

Abstract

High-resolution, high-energy X-ray backlighters are very active area of research for radiography experiments at the National Ignition Facility (NIF) [Miller et al., Nucl. Fusion 44, S228 (2004)], in particular those aiming at obtaining Compton-scattering produced radiographs from the cold, dense fuel surrounding the hot spot. We report on experiments to generate and characterize point-projection-geometry backlighters using short pulses from the advanced radiographic capability (ARC) [Crane et al., J. Phys. 244, 032003 (2010); Di Nicola et al., Proc. SPIE 2015, 93450I-12], at the NIF, focused on Au micro-wires. We show the first hard X-ray radiographs, at photon energies exceeding 60 keV, of static objects obtained with 30 ps-long ARC laser pulses, and the measurements of strength of the X-ray emission, the pulse duration and the source size of the Au micro-wire backlighters. For the latter, a novel technique has been developed and successfully applied.

Production of relativistic electrons at subrelativistic laser intensities

“…Of particular interest is the newly commissioned Advanced Radiographic Capability (ARC) laser [29] at the National Ignition Facility (NIF) [30], which provides a novel diagnostic to NIF experimental platforms. The ARC is unique as the high-est energy short pulse laser and is a source for highflux, moderate-energy x-ray radiography [31,32]; however peak intensities are only marginally relativistic due to the large spot size and long-focal length of the final optics. Previous experiments have hinted that electron temperatures exceeding ponderomotive scaling [33][34][35] may be possible at relatively low intensities.…”

Proof-of-concept Talbot–Lau x-ray interferometry with a high-intensity, high-repetition-rate, laser-driven K-alpha source

“…Regardless of these potential improvements, the level of resolution obtained here is already comparable to the resolution of other x-ray imaging diagnostics fielded at high-repetition-rate facilities, such as gated x-ray framing cameras [40], point-source radiography [41], and pinhole imagers [42]. However, because this diagnostic relies on phase-contrast techniques rather than absorption, it is able to observe regimes that would generally be undetectable to standard diagnostics without the large distances required for other phase-contrast diagnostics [6].…”

An optimized online filter stack spectrometer

“…2. The optimal Cond(E dep ) is 4×10 4 approximately, which has been significantly reduced compared with the unoptimized online FSS configuration, e.g., the CsI FSS reported previously [36] with Cond(E dep ) of 2×10 12 (also 15 channels are taken into account). The optimal configuration obtained in iterations is listed in TABLE.2.…”

“…Then, these electrons can generate X-rays through betatron radiation [2] , inverse Compton scattering [3][4][5] , and bremsstrahlung [6] , thus providing tabletop complements to large-scale conventional accelerator-based X-ray sources. These X-rays sources have advantages of femtosecond duration, micron source size, wide spectral range [7] , thus have tremendous potentials for applications [8] , e.g., biology radiagraphy [9] , non-destructive testing [10,11] , and high-energy-density physics [12,13] .…”