Paul Northrup: The TES Beamline (8-BM) at NSLS-II: tender-energy spatially-resolved X-ray absorption spectroscopy and X-ray fluorescence imaging

I will present details of the TES Beamline at the National Synchrotron Light Source II, covering its design, commissioning, and early results. Its scientific mission includes static and in-situ/operando XRF imaging and spatially resolved (microbeam) XAS — in the tender energy range — for characterization of complex heterogeneous, structured and dynamic natural or engineered materials and systems. My approach for design of TES centered on two primary goals:
1) optimize for the tender energy range, which offers access to elements and edges not accessible (or not accessible with optimal performance) at either hard or soft X-ray beamlines.
2) bring the essential capabilities of an XAS beamline down to the microscale, so as to measure full EXAFS of a single particle or structure the same size as the probe beam.
TES offers routine operations from 2.0 to 5.5 keV, with capabilities to reach down to 1.2 keV with configuration change. It is also designed as an “EXAFS Microprobe” for applications of um-scale extended X-ray absorption spectroscopy fine structure to heterogeneous and small-particle samples. Beam size is user-tunable from ~2 um to 25 um. Energy may be scanned on-the-fly or in step scanning mode. Importantly, the position of the microbeam at the sample location does not move significantly during energy scanning, or when changing energy across the entire routine energy range. This enables full EXAFS of a particle or domain the same size as the probe beam, and measurement of the same spot at different energies. In addition, there is no measurable drift in energy calibration (repeatability) scan-to-scan and over >24 hours. This is critical in an energy range where simultaneous calibration measurements in transmission are generally not feasible, and for speciation mapping where precise and stable control of incident energy is essential. The sample environment is helium atmosphere at room pressure, with infrastructure for in-situ electrochemistry and catalysis in small sample cells or microreactors.

References:

1) P. Northrup, 2019. The TES Beamline (8-BM) at NSLS-II, J. Synch. Rad., 26, 2064-2074 (2019) https://doi.org/10.1107/S1600577519012761
2) A Leri, et al., A Marine Sink for Chlorine in Natural Organic Matter, Nature Geosci., 8, 620-624, 2015. https://doi.org/10.1038/ngeo2481
3) E. Ingall, et al, J. Synch. Rad., 18, 189-197. http://journals.iucr.org/s/issues/2011/02/00/hi5614/hi5614.pdf