The Functional Materials Beamline at CHESS

Introduction In 2019, the Cornell High Energy Synchrotron Source (CHESS) completed its most significant upgrade in nearly 40 years of operation. This upgrade included removal of the three-story-tall particle physics detector, replacement of one-sixth of the Cornell Electron Storage Ring (CESR), and a complete remodel of the experimental floor, including installation of six new undulator-fed beamlines. These modifications enabled a transition from CESR’s historical running mode with counter-circulating positrons and electrons to single-beam operation, resulting in significant improvements to CESR’s properties and performance as an X-ray source. Completion of the upgrade coincided with adoption of a new model for CHESS funding, by which partner institutions sponsor one or more beamlines in addition to a portion of the operational funding of CHESS and CESR. Though beamlines remain owned and operated by Cornell, the mission, core capabilities, and beamtime allocation model of each beamline are determined by the partner. The Materials Solutions Network at CHESS (MSN-C) is one of several new sub-facilities emerging from this change. MSN-C is a sponsored program of the Air Force Research Laboratory based on two end stations with complementary capabilities: the Structural Materials Beamline (SMB/ID1A3) operates from 40 to 200 keV and is optimized for the study of metals and other high-density materials [1, 2], while the Functional Materials Beamline (FMB/ID3B) operates at a series of discrete energies from 10 to 30 keV and is optimized for soft materials such as polymer composites and thin films. Together, the resources and access model of MSN-C represent an unprecedented effort to develop and apply state-of-the-art synchrotronbased techniques to real-world manufacturing challenges faced by industry, such as determination of residual stress in as-manufactured parts [2]. This includes new challenges associated with emerging materials and processing, such as 3D printing of polymer composites, additive manufacturing of metals, and autonomous approaches to materials synthesis. This article describes the layout and capabilities of FMB, along with several examples showcasing its use. The design of FMB was driven by two primary goals. The first was to enable both real-space and reciprocal-space interrogation of heterogeneous components such as those based on polymer-matrix composites. This goal is addressed by implementation of two complementary modes of operation: scanning X-ray microdiffraction (XMD) [3] based on simultaneous smalland wide-angle X-ray scattering (SAXS and WAXS), and full-field imaging. XMD enables determination of variation in crystalline and molecular ordering, defects, and heterogeneities at the micron scale, but with data acquisition times limited by the need to raster a sample through the beam. Full-field imaging, referring here to imaging without the use of an imaging optic downstream of the sample, permits 2D images exhibiting radiographic and/or phase contrast to be collected in parallel at approximately 1 μm resolution and at frame rates limited only by detector frame rate and incident intensity. The second goal was to enable in-situ studies of highly non-equilibrium phenomena related to materials fabrication and processing, such as the evolution of microstructures, strain, and heterogeneities. This goal is addressed in several ways, especially the ability to accommodate large environments around the sample, custom detector configurations, python-based experimental control, synchronization of data acquisition with user-supplied equipment, and robust, flexible support for fly-scan operation, in which data acquisition occurs during continuous motor motion. A third FMB design priority was minimizing the time and labor required to accommodate different experimental systems and modalities. This priority is manifest in a highly automated, modular setup in the hutch in which the upstream flightpath and detector tables can easily switch among different configurations. Similarly, the sample table may be completely exchanged in about an hour, permitting complicated setups to be partially or wholly configured outside the hutch before the beamtime for which it is needed begins, then quickly transferred into place. Since first light at FMB in October 2019, this rare combination of capabilities has demonstrated unique utility for the study of soft materials.