Figure 5.

Flat-field synthesis. (a) Input data E; in total 150 empty images have been used as input. The selected empty images show the variation of intensity and movement of the illumination over the CRL’s aperture. (b) Components extracted by PCA. The strongest eight components out of 50 are shown. Each component has an ℓ2-norm of 1. (c) Empty beam images with approximately the same intensity. Only pulses from the bin with highest occurrence in the histogram Fig. 2 ▸ (700 µJ to 750 µJ) were selected. (d) The weights for the first nine components of the measurements shown in (c). Despite the similar FEL pulse energy, the measurements show some diversity in the mixing of the components. Color coding as in (c). The scale bar indicates 1 mm in the plane of the detector.