Figure 3
From: 3D visualization of XFEL beam focusing properties using LiF crystal X-ray detector
Size of the HERMES focusing system apertures projection and XFEL beam vs defocusing (experiment and calculations).
Panel (a): comparison of vertical and horizontal sizes of the HERMES aperture measured along the beam propagation with calculated ones using geometrical optics. Panel (b): Calculated dimension of the Gaussian beam incident on the HERMES mirrors vs the beam quality factor M2 for the source size W0 = 60 μm. Shaded areas show, estimated according to the experimental data, the values of the beam quality factor M2 of the XFEL beam incident on the HERMES mirrors in horizontal (pink) and vertical (blue) directions. Arrows show the corresponding ranges of the beam quality factors for the case of W0 = 60 microns in both directions, which are M2H ~3.5 ÷ 4.0 and M2V ~3.6 ÷ 4.5. Panel (c): Experimental and calculated dependences of beam size W’exp vs the distance Δf from the focal plane of the HERMES system, independently for horizontal and vertical directions. Good overlap of experimental and calculated sizes for M2 = 3.8 in horizontal and M2 = 3.9 in vertical directions can be seen.
