Diagnosing hotspot asymmetries through simultaneous algebraic reconstruction tomography in direct-drive implosions on OMEGA

Understanding and mitigating hotspot asymmetries is crucial for achieving high performance in inertial confinement fusion (ICF) implosions. This talk presents recent advancements in diagnosing hotspot x-ray asymmetries in direct-drive implosions on OMEGA. A new TIM-based x-ray imager has been deployed on cryogenic implosions, using pinholes to project thousands of images onto an image plate. A novel algorithm has been developed to form composite images from these individual projections, resulting in high signal-to-noise levels. By matching the filtration of these images to those of two fixed x-ray imagers, up to six unique lines of sight capture time-integrated profiles with the same photon energy spectra. These images are then processed using a Simultaneous Algebraic Reconstruction Technique (SART) to form a three-dimensional understanding of the hotspot morphology. This work has revealed a persistent and systematic mode 2 asymmetry in the hotspot x-ray emission, consistently observed across a range of implosions. The origin of this systematic mode 2 is currently a topic of ongoing investigation, with potential implications for understanding energy coupling and implosion dynamics. Further research aims to identify the root cause of this asymmetry and explore strategies for its mitigation, ultimately contributing to improved ICF performance.