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![[Figure 2]](pm5022fig2mag.jpg)
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Figure 2
Schematic of a scanning X-ray microprobe. An optic, in our case a Fresnel zone plate (Michette, 1986  ), produces an X-ray focus, through which the specimen is raster-scanned. The image is acquired by recording the detector signal(s) at each scan position. The focal spot size, and therefore the spatial resolution, is roughly equal to the finest features of the zone plate. It is typically around 30–50 nm in the soft and intermediate X-ray range (up to a few keV), and around 100 nm for hard X-rays (around 10 keV). A combination of a central stop on the zone plate and an order-sorting aperture (OSA) is used to isolate the first-order focus of the zone plate, leading to a hollow-cone illumination of the specimen (Kirz et al., 1995). Phase gradients in the specimen deflect the beam and lead to a redistribution of intensity on the transmission detector. In this illustration the difference signal between the green and red segments measures the horizontal beam shift. A single large-area transmission detector would only determine specimen absorption. A separate energy-dispersive detector measures fluorescence photons emitted by trace elements in the specimen. |
![[Figure 2]](pm5022fig2.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
