Doctoral Defense

Development of High-Resolution Amorphous Selenium Detectors for X-Ray Imaging

Himanshu Goel

October 18, 2024
1:30pm
Light Engineering, Room 250
Advisor: Petar Djuric

Modern light sources like synchrotrons enable studies of materials at mesoscale and nanoscale levels. However, demand for beamline time exceeds availability. Detailed physical optics simulations of beamlines and experiments can facilitate efficient use of beamline time by allowing users to test experiment feasibility prior to utilizing valuable beamline time. Such simulations can also assist in testing and improving data processing methods for many experiments that are performed at synchrotron light sources. The Synchrotron Radiation Workshop (SRW) software package helps to make these high- fidelity simulations possible. While SRW supports detailed simulations of synchrotron radiation sources and beamlines, end-to-end simulations of coherent scattering experiments involving a partially coherent beam are impractical due to being too computationally expensive. To address this, support for GPU accelerated computation has been integrated into SRW. The design and implementation of this acceleration is discussed. Furthermore, a partially coherent simulation of an X-ray photon correlation spectroscopy (XPCS) experiment at NSLS-II’s coherent hard X-ray (CHX) scattering beamline is discussed as a motivating example of these kinds of end-to-end simulations, where GPU computation has been used to accelerate a significant portion of wavefront propagation calculations. A solution of silica nanoparticles suspended in water at room temperature is simulated using the LAMMPS molecular dynamics software and imported into SRW for use as a time-varying sample for XPCS. This sample is illuminated by partially coherent undulator radiation through the CHX beamline to produce scattering patterns for XPCS analysis. The accuracy of the simulation is compared against previously obtained experimental data. Additionally, end-to-end simulations of ptychography experiments based on the X-ray Pump Probe beamline at the Linac Coherent Light Source are described, serving as another example of the simulations these developments support and of the capabilities that can be enabled by being able to perform such sophisticated simulations.