Tables for
Volume F
Crystallography of biological molecules
Edited by M. G. Rossmann and E. Arnold

International Tables for Crystallography (2006). Vol. F, ch. 8.1, pp. 156-158   | 1 | 2 |

Section 8.1.4. Beam characteristics delivered at the crystal sample

J. R. Helliwella*

aDepartment of Chemistry, University of Manchester, M13 9PL, England
Correspondence e-mail:

8.1.4. Beam characteristics delivered at the crystal sample

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The sample acceptance, α [equation ([link]], is a quantity to which the synchrotron machine emittance [equation ([link]] should be matched, i.e., [\alpha = x \eta, \eqno(] where x is the sample size and η the mosaic spread. For example, if [x = 0.1\;\hbox{mm}] and [\eta = 1\;\hbox{mrad}] (0.057°), then [\alpha = 10^{-7}\;\hbox{m rad}] or 100 nm rad.

At the sample position, the intensity of the beam, usually focused, is a useful parameter: [\hbox{Intensity} = \hbox{photons per s per focal spot area}. \eqno(] Moreover, the horizontal and vertical convergence angles are ideally kept smaller than the mosaic spread, e.g. ~1 mrad, so as to measure reflection intensities with optimal peak-to-background ratio.

To produce a focal spot area that is approximately the size of a typical crystal (~0.3 mm) and with a convergence angle ~1 mrad sets a sample acceptance requirement to be met by the X-ray beam and machine emittance. A machine with an emittance that matches the acceptance of the sample greatly assists the simplicity and performance of the beamline optics (mirror and/or monochromator) design. The common beamline optics schemes are shown in Fig.[link].


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Common beamline optics modes. (a) Horizontally focusing cylindrical monochromator and vertical focusing mirror [shown here for station 9.6 at the SRS (adapted from Helliwell et al., 1986[link])]. (b) Rapidly tunable double-crystal monochromator and point-focusing toroid mirror [shown here for station 9.5 at the SRS (adapted from Brammer et al., 1988[link])].

In addition to the focal spot area and convergence angles, it is necessary to provide the appropriate spectral characteristics. In monochromatic applications, involving the rotating-crystal diffraction geometry, for example, a particular wavelength, λ, and narrow spectral bandwidth, [{\delta\lambda /\lambda}], are used. Fig.[link] shows an example of a monochromatic oscillation diffraction photograph from a rhinovirus crystal as an example recorded at CHESS, Cornell. Fig.[link] shows the prediction of a white-beam broad-band Laue diffraction pattern from a protein crystal recorded at the SRS wiggler, Daresbury, colour-coded for multiplicity.


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Single-crystal SR diffraction patterns. (a) Rhinovirus monochromatic oscillation photograph recorded at CHESS (Arnold et al. 1987[link]; see also Rossmann & Erickson, 1983[link]). (b) Prediction of a protein crystal Laue diffraction pattern (for an illuminating bandpass, without monochromator, [\sim \!0.4 \lt \lambda \lt 2.6 \;\hbox{\AA}]). The colour coding is according to the multiplicity of each spot: turquoise for singlet reflections, yellow for doublets, orange for triplets and blue for quartet or higher-multiplicity Laue spots. Reproduced with permission from Cruickshank et al. (1991[link]).

Table[link] lists the internet addresses of the SR facilities worldwide that currently have macromolecular beamlines.

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Internet addresses of SR facilities with macromolecular crystallography beamlines

Synchrotron-radiation sourceLocationAddress
ALS, Advanced Light Source Lawrence Berkeley Lab., Berkeley, California, USA
APS, Advanced Photon Source Argonne National Lab., Chicago, Illinois, USA
BESSY Berlin, Germany
BSRF, Beijing Synchrotron Radiation Facility Beijing, China
CAMD, Center for Advanced Microstructures and Devices Baton Rouge, Louisiana, USA
CHESS, Cornell High Energy Synchrotron Source Ithaca, New York, USA
Daresbury Laboratory CLRC Daresbury, England
Elettra Trieste, Italy
ESRF, European Synchrotron Radiation Facility Grenoble, France
HASYLAB DESY, Deutsches Elektronen-Synchrotron Hamburg, Germany
LNLS, National Synchrotron Light Laboratory Campinas, Brazil
LURE Orsay, France
MAXLab Lund, Sweden
NSLS, National Synchrotron Light Source Brookhaven National Lab., New York, USA
The Photon Factory, KEK Tsukuba, Japan
PLS, Pohang Light Source Pohang, Korea
SLS, Swiss Light Source Paul Scherrer Institut, Villigen, Switzerland
SPring-8, Super Photon Ring Riken Go, Japan
SRRC, Synchrotron Radiation Research Center Hsinchu City, Taiwan
SSRL, Stanford Synchrotron Radiation Laboratory SLAC, California, USA
VEPP-3 Novosibirsk, Russia

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