Single-Shot, Ultrafast, Multi-Frame X-Ray Imaging of Defect-Bearing Ablator Materials in Extreme Conditions
Characterization of the dynamic behavior of defect-bearing ablator materials subjected to extreme conditions is essential in advancing fusion energy as an reliable and abundant energy source. By understanding how materials evolve spatially and temporally we can minimize hydrodynamic instabilities, which are major contributing factors to energy yield degradation in inertial confinement fusion (ICF) experiments. In this thesis we demonstrate the capabilities of an ultrafast x-ray imaging (UXI) detector, the Icarus V2, where we capture multiple frames of single void-bearing sample compressed by a high-intensity laser shockwave. Using the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS), we conducted two experiments with the x-ray free electron laser (XFEL) multi-pulse mode, delivering four nanosecond-separated pulses to a sample impacted by a laser shockwave, obtaining multiframe images of a single sample in the holographic and direct imaging regime with the UXI detector. In contrast to the low temporal resolution provided by current cameras, the Icarus V2 can capture images with high temporal resolution, which can be used to determine the mechanisms that prevent thermonuclear ignition in ICF experiments. For images captured in the holographic regime at our XFEL energy of 8.23 keV, we realized that the shock front was obscured by strong phase-contrast effects. We recognized that by increasing the XFEL energy while in the holographic regime, more distinguishable features could be revealed behind and along the shock front. Alternatively, in the direct-imaging configuration we discovered that the evolution of microstructural features were directly recognizable in comparison to the holographic regime at lower XFEL energies. Overall, the images captured by the UXI in both regimes demonstrated our ability to obtain multiframe images of processes that occur over several nanoseconds for single samples, which has never been done before. Moreover, the capabilities of the UXI enable extraction of quantitative information over multiple frames, which can help with uncovering the underlying physics involved in high energy density (HED) physics experiments and other experiments involving non-repeatable ultrafast phenomena. Specifically, insight into the behavior of the void can be gained by performing phase retrieval on the images and obtaining the areal density of the materials during laser-shock ablation. Generally, the UXI improves data acquisition speed and operational efficiency, which extends this camera's functionality to experiments that occur at various time scales or experiments that require multiple images to be captured.
College and Department
Physical and Mathematical Sciences; Physics and Astronomy
BYU ScholarsArchive Citation
Hodge, Daniel S., "Single-Shot, Ultrafast, Multi-Frame X-Ray Imaging of Defect-Bearing Ablator Materials in Extreme Conditions" (2022). Theses and Dissertations. 9807.
ultrafast, x-ray, imaging, shock, void, Icarus V2, UXI, MEC, pulse, void-shock, heterogeneities, inhomogeneities, fusion, XFEL