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![[Figure 2]](yi5010fig2mag.jpg)
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Figure 2
Beam profiles as measured on the Ce:YAG screen or profile monitor located roughly halfway between the Be lenses and the refocus plane. In both images shown, small lines and crosshairs are fiducials deposited on the Ce:YAG screen for resolution calibration. (a) Beam profile for the out of focus nanofocus beam after it is allowed to diverge for ∼3.1 m. These data were collected at 9.6 keV and show a magnified image of the pupil function of the nanofocus KB system at CXI. The two-lobe beam profile in the horizontal direction is caused by the limited size and the figure errors of the front-end enclosure offset mirrors (Barty et al., 2009  ). The beam profile in the vertical is not distorted owing to the horizontal deflection of these front-end mirrors. (b) Similar image of the beam profile on the Ce:YAG screen captured with the Be refocusing lenses inserted. The limited aperture of the lenses as required to produce the short focal lengths needed causes some obvious aperturing of the beam for refocusing purposes. Only the part of the beam within the circular area in the bottom left is refocused. The rest continues to diverge and is removed by using slits downstream of the lenses. The lens aperture is also seen to be wider than a single lobe of the horizontal beam profile which has an impact on the size of the refocused spot by effectively reducing the numerical aperture of the system. For both images shown, the beam profile extends almost to the edges of the plotted area where a sharp cutoff can be seen due to the finite nanofocus KB aperture. |
![[Figure 2]](yi5010fig2.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
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