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Figure 5
Close-ups of diffraction patterns from BTV crystals, collected on several different detectors/scanners at different beamlines at the ESRF and the SRS. (a) Diffraction from a BTV-1 SA crystal collected on a Mar 345 imaging plate using a pixel size of 150 µm. The crystal-to-plate distance was 600 mm, the wavelength was 0.99 Å and the crystal was oscillated through 0.2°. (b) The same image as (a) but recorded with the pixel size set to 100 µm, showing the improvement in spot separation. (c) Image recorded on a large 40 cm × 80 cm imaging plate using the EMBL off-line scanner, on EH3 ID14 at the ESRF. The crystal-to-plate distance was 1250 mm, the crystal was oscillated through 0.25° and the wavelength was 0.99 Å. Note the remarkable separation of the spots and the clear improvement in signal to noise (the background is essentially flat) with the sample-to-detector distance set to over 1.2 m. The resolution at the edge of the plate was 3.6 Å, comparable with Figs. 5[link](a) and 5[link](b). (d) Image taken from a BTV-1 SA crystal using an ADSC Quantum 4 2 × 2 CCD at beamline 9.6 at the SRS. The crystal-to-plate distance was 400 mm and the crystal oscillation angle was 0.25°. The pixel size of the ADSC CCD is 81.6 µm and the image has been scaled down accordingly. Note that even for an X-ray source such as beamline 9.6, with a far higher beam divergence than ID2, the spot separation with the crystal-to-plate distance of 400 mm is extremely good, presumably reflecting the very small point-spread function of the ADSC detector compared with the Mar 345 imaging plate. (e) Close up of a diffraction image from a crystal of BTV-10 USA, taken on ID2 using a MARresearch 300 mm imaging plate with a 150 µm pixel size. The separation of the spots within the row is c*, i.e. 1/1584 Å−1, and so the detector distance was maximized to 1050 mm. The crystal was oscillated through 0.25° and the resolution at the edge of the plate is about 6.5 Å.

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