## 4 Results and Discussion  
Our simulations were performed using a range of configurations for the beamline components and X-ray focusing optics. The results of the simulations were used to evaluate the X-ray beam properties, including the flux, the spot size, and energy resolution for different configurations. First, we performed simulations of the beamline for the white beam mode, i.e., without any monochromator. To shape the X-ray spectrum, Al filters of variable thickness (0.01 mm, 0.05 mm, 0.1 mm, 0.25 mm, 0.5 mm, 1 mm) were simulated. White beam energy spectra and the total flux (denoted as N in the legend) were simulated for full vertical beam size and for 1 mrad horizontal slit opening (Figure 5). Figure 4: Visualizations of simulated rays at focal plane of polycapillary lens. The mean beam energy of 10 keV was achieved with DMM. White beam slits closed to 3.53 mm \(\times\) 1.06 mm. Figure 5: Simulated flux for unfocused white beam and Al filters with different thicknesses. In the figure legend, N denotes the energy-integrated flux. Next, we calculated the flux for both monochromator types, DCM and DMM. For DMM, both stripes were simulated for the relevant energy ranges. The results are shown in Figure 6.  
Subsequently, we focused on the prediction of achievable beam parameters, while using different capillary optics. For the sake of clarity, the next figures show results for only three types of polycapillary lenses and for one monocapillary lens. However, the supplementary materials present selected results for the other four available polycapillary lenses. The transmission efficiencies of the focusing elements (Figure 7) were calculated by performing the following steps: (i) slits were set to be fully opened in the vertical and horizontal directions, (ii) a simulation for the white beam was conducted (without any Al filters) for different energies, in the range of 4-15 keV, the step between the points was 0.5 keV, and bandwidth for every step was 0.1%, (iii) the flux N\({}_{0}\) was calculated for rays that were accepted into the optics entrance, (iv) the flux N was calculated in the focal spots, and (v) the transmission was calculated as T = N/N\({}_{0}\). The transmission efficiency for AEXML is significantly higher than for polycapillary optics since, in contrast to polycapillary optics, it relies on single-bounce transmission. AEXML optic has two distinguishable drops, which are caused by the L absorption edges of the platinum inner coating. The spot sizes in the focal planes (Figures 8 and 9) were estimated using the same white beam simulations as described above for transmission efficiencies. First, vertical and horizontal histograms of the rays were calculated, then histograms of FWHMs were determined for both axes and the average value was taken as the final spot size. For polycapillary lenses and for an ellipsoidal single-bounce monocapillary lens, the full energy spectra for the beams that passed through the optics were estimated during the simulations. These results were used to calculate the achievable fluxes in the focal spot. For the white beam mode, the different thicknesses of Al filters were used in simulations (Figure 10). The flux was also estimated for the beam that passed through one of the monochromators (DCM or DMM described in the previous section) and later focused by the lenses (Figure 11). The results for a subset of simulated lenses are presented in supplementary materials. Figure 6: Simulated flux for unfocused beam after DCM and DMM monochromators. For DCM, the beam was slit down vertically to keep a bandwidth of dE/E = 0.02%. Figure 8: Simulated spot sizes for polycapillary lens and an ellipsoidal monocapillary lens. Figure 7: Simulated transmission efficiencies for polycapillary lenses and an ellipsoidal monocapillary lens. All steps were performed by simulating white beam with fully opened slits in vertical and horizontal directions. Figure 9: Simulated spot sizes for polycapillary lenses.