Visiting Student - XSD - Koda, Ryota - 10.21.26

This project proposes a real-time workflow for 3D X-ray ptychography that uses a sample-specific surrogate model to reduce reconstruction time. In 3D ptychography, a sample is illuminated from many angles, and a 2D image is recovered for each angle with iterative phase retrieval (e.g., ePIE) before the images are combined into a 3D volume. Because the phase retrieval is repeated for every direction, it dominates the total runtime. Earlier surrogate-model studies sped up this step but did not evaluate the whole workflow, and they typically required a training dataset prepared in advance. The proposed method instead builds the surrogate model on-the-fly. First, directional subsampling selects a subset of the projection angles. ePIE is run only on those angles, and the resulting diffraction pattern and object image pairs form a small training set. A surrogate model is trained on this set and predicts initial object estimates for the remaining angles. After preprocessing, these predictions initialize a second ePIE pass. The workflow will run on GPUs. Additional work will include the development of a foundation surrogate model for diverse samples and testing other surrogate architectures.

Education and Experience Requirements

•The entirety of the appointment must be conducted within the United States.

•Must be 18 years or older at the time the appointment begins.

•Applicants must be:

• Currently enrolled in undergraduate or graduate studies at an accreditedinstitution.
• Graduated from an accredited institution within the past 3 months; or
• Actively enrolled in a graduate program at an accredited institution.

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