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Results: 14

1.
Figure 9

Figure 9. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Available segmentations of the detector chip (see text).

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
2.
Figure 4

Figure 4. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Simplified schematic of one channel of the charge integrating detector electronics (see text).

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
3.
Figure 7

Figure 7. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Linearity of the electronics with integration time (bottom axis) and with input signal (top axis). In both cases the error bars are too small to display. The residuals (increased by a factor of 200 in the plot) indicate a slight non-linearity.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
4.
Figure 3

Figure 3. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

X-ray penetration into silicon for various photon energies. The quantum efficiency of the detector chip is given by the fraction of photons absorbed. A 300 µm-thick chip is almost 100% efficient up to 8 keV. Beyond that, the chip can still be used up to 15 or 20 keV with reduced efficiency. Data from Henke et al. (1993 ▶).

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
5.
Figure 8

Figure 8. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Hardware components of the detector. The insets show the chip mounted on a ceramic carrier. Each chip has two segment structures, only one of which is used at a time (Feser et al., 2006 ▶). Left inset: back (n-) of the chip. This is the side where the X-rays will be incident. A wire connection on the upper right carries the bias voltage. Right inset: segmented front (p-) side. Wire bonds connect the detector segments to the carrier pins through a cut-out in the carrier.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
6.
Figure 6

Figure 6. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Detector readout scheme in step-scan mode. The dashed line shows schematically the output voltage of the integrating amplifier with periodic reset. The output of the sample-and-hold circuit (solid line) is ‘quasi-constant’ owing to the S/H being set to hold for most of the integration time. The pixel dwell time t dwell, indicated by the gray boxes, is much longer than the detector integration time t int. The short sampling period of the S/H circuit (about 20 µs) introduces a negligible inaccuracy.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
7.
Figure 1

Figure 1. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Number of photons required to see a 50 nm-thick protein structure in either air or 50 nm of water (Hornberger et al., 2006 ▶). The calculation is based on a simple projection (for absorption) and refraction [for differential phase contrast (DPC)] model with photon statistics as the only noise source. It applies the Rose criterion of a minimum signal-to-noise ratio of five for the detectability of features (Rose, 1946 ▶). Atomic scattering data from Henke et al. (1993 ▶).

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
8.
Figure 12

Figure 12. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Absorption (left) and DPC (right) images of a freeze-dried cardiac myocyte recorded at 10 keV photon energy at 2-ID-E. While the specimen is relatively thick and therefore visible in absorption contrast (here recorded with an ion chamber rather than the segmented detector), the phase-contrast image shows considerably more detail, in particular the cross-striations typical of heart muscle. Sample provided by B. M. Palmer, University of Vermont. Image recorded with the modified soft X-ray detector and an aluminium absorber. The step size is 200 nm, and the dwell time is 10 ms.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
9.
Figure 5

Figure 5. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Full integration cycle of the detector electronics. Trace 1 shows the output of the sample-and-hold (S/H) circuit. Traces 2 and 3 show the control pulses of the reset and S/H switches, respectively. Trace 4 represents the acquisition pulse sent to the ADC. The solid lines show a cycle with the S/H disabled (following permanently), so that we directly see the output of the integrating amplifier. The dashed lines show a cycle with the S/H enabled. The small step in the integrator output at the end of the reset period is due to charge injection from the parasitic capacitance of the FET switch S2 into the feedback capacitor.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
10.
Figure 11

Figure 11. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Absorption (left) and DPC (right) images of a diatom (phytoplankton cell) recorded at 10 keV photon energy at beamline 2-ID-E. As above, the specimen is completely invisible in absorption, but clearly visible in phase contrast. We have used the same 100 nm-outermost-zone-width zone plate as above, a step size of 100 nm and a pixel dwell time of 2 ms. Sample courtesy of Ben Twining and Stephen Baines (Marine Sciences Research Center, Stony Brook University).

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
11.
Figure 13

Figure 13. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Absorption (left) and DPC (right) images of a diatom (phytoplankton cell) recorded at 1790 eV photon energy at beamline 2-ID-B at the APS. This image was also obtained with the modified soft X-ray detector. While the specimen is visible in absorption, the DPC image shows considerably more detail. The diagonal line visible in both images is the edge of a silicon nitride window. The horizontal line is caused by a sudden change in X-ray intensity; thus it is almost invisible in the differential measurement. This image was recorded using a 50 nm-outermost-zone-width zone plate, 25 nm steps and 3 ms dwell time.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
12.
Figure 14

Figure 14. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Absorption (left) and DPC (right) images of 5 µm-diameter polystyrene spheres recorded at 2500 eV photon energy at beamline 2-ID-B. At this photon energy the spheres are visible in absorption, but show much more detail in DPC. The pedestal around the spheres is due to residual solution, and the small bump on the right-hand sphere is due to radiation damage caused by a 30 s exposure to the focused X-ray beam. This scan was performed with a 50 nm-outermost-zone-width zone plate, 25 nm steps and 5 ms dwell time.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
13.
Figure 10

Figure 10. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Absorption (left) and DPC (right) images of 5 µm-diameter polystyrene spheres recorded at 10 keV photon energy at beamline 2-ID-E at the APS. Both images are generated from the same data set, using different combinations of detector segments as indicated by the insets (see Fig. 9 ▶; green, added; red, subtracted; gray, not used). The spheres are completely invisible in absorption contrast, but well visible in DPC. We have used a zone plate with an outermost zone width of 100 nm, a step size of 50 nm and a pixel dwell time of 3 ms.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.
14.
Figure 2

Figure 2. From: Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

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.

B. Hornberger, et al. J Synchrotron Radiat. 2008 July 1;15(Pt 4):355-362.

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