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Figure 2
Components of the XFEL experiment. (a) Illustration of the setup in the experimental hutch with the drop-on-tape (DOT) sample-delivery method. The DOT method allows for precise illumination of the microcrystals including specific time-delay measurements with the free-space laser. The forward scattering leads to diffraction images, providing us with electron density maps and models. Measurement of fluorescence emission in the orthogonal direction provides us with spectroscopic information of the Mn cluster. (b) Microcrystals of PS II that have been optimized for XFEL experiments. Optimization steps include a seeding protocol for uniform size and a post-crystallization treatment protocol for isomorphous crystal batches. (c) Data-processing pipeline to obtain merged intensities from raw diffraction images. Precise merging of Bragg spots for PS II requires simultaneous refinement of the detector and crystal models to tighten their distributions. In the top box, the effect of the joint refinement is shown (blue: only crystal models from all shots are refined; green: crystal models and separate detector models for each shot refined; red: crystal models and single detector model across all shots refined). During live data collection, a fast-feedback mechanism via the cctbx.xfel GUI is used to provide a running analysis of the experiment, including spotfinding, indexing and merging statistics. In the lower box, a screenshot of the GUI is shown. In the top part, the blue trace shows the spotfinding statistics, in the middle part, the green trace shows the solvent hitrate, the blue trace shows the indexing rate and the pink trace shows the number of multiple lattices indexed. This feedback is used to further optimize sample conditions. Parts of (b) have been adapted from Ibrahim et al. (2015BB34) and (c) from Brewster et al. (2018BB9) and Brewster, Young et al. (2019BB10).

IUCrJ
Volume 10| Part 6| November 2023| Pages 642-655
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523008928