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

International Tables for Crystallography (2006). Vol. F, ch. 7.2, p. 148   | 1 | 2 |

Section 7.2.1. Overview

M. W. Tate,a* E. F. Eikenberryb and S. M. Grunera

aDepartment of Physics, 162 Clark Hall, Cornell University, Ithaca, NY 14853-2501, USA, and  bSwiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
Correspondence e-mail:  mwt5@.cornell.edu

7.2.1. Overview

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After more than 20 years of refinement, CCD (charge-coupled device) detectors have emerged as the most useable and accurate large-area detectors available for the X-ray energies of interest to crystallographers. CCDs are familiar as the imagers in television and digital cameras, but the scientific grade devices used in detectors are larger and have more pixels and a lower noise amplifier. CCD detectors are an assembly of several components: an energy converter (e.g. phosphor), an optical relay with or without gain (fibre optics, lenses and/or intensifier) and the imaging CCD.

Although many configurations have been used in the past, improvements in the size and quality of fibre-optic tapers have led to the possibility of direct coupling – eliminating intensifiers and lenses – so long as other components are carefully optimized at the same time (Eikenberry et al., 1991[link]). Optimizations include the phosphor, the CCD and electronics, and the elimination of unneeded optical interfaces. Current commercial designs employ just three elements: phosphor, taper and CCD (Fig. 7.2.1.1[link]). This concept enabled the use of large tapers, machined square at the front, that can be stacked together to form mosaic arrays. Consequently, there is now no inherent limit to the size of a CCD detector.

[Figure 7.2.1.1]

Figure 7.2.1.1 | top | pdf |

Schematic of a single-module CCD detector. The thin phosphor screen is behind a light- and vacuum-tight vacuum window and is coupled to a fibre-optic taper, which is, in turn, coupled to a CCD. The CCD is thermoelectrically cooled to 213 K and housed in a vacuum cryostat. Reproduced with permission from Tate et al. (1995[link]).

References

Eikenberry, E. F., Tate, M. W., Belmonte, A. L., Lowrance, J. L., Bilderback, D. & Gruner, S. M. (1991). A direct-coupled detector for synchrotron X-radiation using a large format CCD imaging array. IEEE Trans. Nucl. Sci. 38, 110–118.








































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