Design and Modeling of Tabletop X-Ray Sources

High-brightness x-ray sources are essential tools of scientific discovery in a wide variety of fields, including biology, chemistry, and materials science. These sources rely on high-energy electron beams to generate x-rays, traditionally requiring large, expensive synchrotron facilities. Laser plasma acceleration (LPA) of electrons is characterized by ultra-high gradients, showing great promise for reducing the size and cost of accelerator-based x-ray sources. Indeed, GeV electron bunches have been obtained in cm-scale LPA experiments, and generation of x-rays from LPA electron sources has been experimentally demonstrated. Simulations have played a key role in supporting LPA developments. New capabilities are now needed to provide accurate, efficient, end-to-end simulations of LPA-based x-ray sources. These capabilities will enable rapid design iterations to improve the performance and reliability of tabletop light sources. Time-explicit particle-in-cell (PIC) simulations provide the most complete description of the laser plasma interaction and electron acceleration, but enhancements are needed to improve the accuracy of PIC simulations, and to extend the technique to include modeling of x-ray generation. We will use existing particle tracking capability to develop post-processing tools to compute emitted x-ray patterns. We will improve the accuracy of the LPA injection simulations by improving particle statistics, both statically using short, reduced-model simulations as a guide, and dynamically by implementing particle-splitting capabilities. Simulation results will be validated via comparison with experimental data.Commercial Applications and Other Benefits: The proposed approach to improving laser-plasma PIC simulations, together with post-processing techniques, will be published, to the benefit of the international plasma-based accelerator community. The enhanced parallel simulation code, validated against experimental measurements, will be available to DOE funded researchers and other institutions under appropriate commercial and noncommercial licenses. GeV-scale plasma-based electron accelerators show increasing promise not only for compact x-ray sources, but also for next-generation high-energy colliders, high-brightness ion sources, and compact light sources in the THz regime. There are therefore many applications of this work in medicine, science and national security