An upgrade of the area detector for the FMX beamline at NSLS-II - Project Summary/Abstract We propose to upgrade the X-ray area detector of the Frontier Microfocusing Macromolecular Crystallography (FMX) beamline at the National Synchrotron Light Source-II (NSLS-II). The current detector, a DECTRIS Eiger X 16M will reach its end of support in 2025. We propose to upgrade it with an Eiger2 XE 9M detector with a 450 µm Silicon sensor. The new detector will ensure the beamline’s highly reliable operation for the US structural biology and biomedical user community. The five to ten times higher frame rate, and the three times higher count rate will enable users to align and interrogate crystals with higher resolution diffraction-based raster maps to collect higher resolution and higher fidelity data from smallest crystals and from inhomogeneous and hard to align crystals. The higher frame rate will increase the productivity of the measurements by allowing users to collect data from more crystals, for more efficient screening for best diffracting crystals, for sampling a larger parameter space in ligand screening and fragment screening measurement campaigns for drug research. The ability to collect frames faster and with a finer step size will allow the development of optimized and more automated workflows, for example for multi-crystal data collection to merge data from multiple marginal crystals, which previously may have required a time-consuming crystal optimization back in the researchers’ home laboratory. Location of smallest microcrystals with the smallest beam focus of 1 micrometer of the FMX beamline will allow collection of complete datasets from crystals that are intractable at other US beamlines. The Si sensor will enable data collection at longer wavelength to support the identification of functionally important ions and metals, for example in enzyme active sites. New triggering and gating modes will increase accessible time scales in dynamic and time-resolved crystallography. In summary, the new detector will ensure the beamline’s reliability, and will allow NIH-funded investigators and other researchers to collect more high-quality data faster, to support their scientific discovery.