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Updated: Feb 3, 2026

Measurement of X-ray Beam Coherence along Multiple Directions Using 2-D Checkerboard Phase Grating
Published on: October 11, 2016
Using time-resolved penumbral imaging to measure low hot spot x-ray emission signals from capsule implosions at the
D T Bishel1, B Bachmann1, A Yi2
1Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Abstract:
We have developed and fielded a new x-ray pinhole-imaging snout that exploits time-resolved penumbral imaging of low-emission hot spots in capsule implosion experiments at the National Ignition Facility. We report results for a series of indirectly driven Be capsule implosions that aim at measuring x-ray Thomson scattering (XRTS) spectra at extreme density conditions near stagnation. In these implosions, x-ray emission at stagnation is reduced by 100-1000× compared to standard inertial confinement fusion (ICF) implosions to mitigate undesired continuum background in the XRTS spectra. Our snout design not only enables measurements of peak x-ray emission times, t , where standard ICF diagnostics would not record any signal, but also allows for inference of hot spot shapes. Measurement of t is crucial to account for shot-to-shot variations in implosion velocity and therefore to benchmark the achieved plasma conditions between shots and against radiation hydrodynamic simulations. Additionally, we used differential filtering to infer a hot spot temperature of 520 ± 80 eV, which is in good agreement with predictions from radiation hydrodynamic simulations. We find that, despite fluctuations of the x-ray flash intensity of up to 5×, the emission time history is similar from shot to shot and slightly asymmetric with respect to peak x-ray emission.
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