The Siemens SMART CCD Detector for Macromolecular Crystallography with Advanced X-ray Sources. J.C. Phillips, R.D. Durst, J.L. Chambers, Siemens Analytical X-ray Systems, Inc., 6300 Enterprise Lane, Madison, WI 53719-1173

There are several tradeoffs in the design of CCD detectors and these are best made with a specific application in mind. Detectors for small molecule crystallography, for example the Siemens SMART system, originally used Mo radiation, a suitably thick phosphor, a modest fiber optics taper and a 1K CCD chip and has been used with great success. For work at synchrotron sources, various wavelengths may be used so design which allows for convenient phosphor changes is required. For work with proteins in the laboratory, Cu radiation is normally used. This requires a larger detector to cover the diffraction pattern, as well as a more sensitive detector since the pattern is weaker, the background is higher and the Cu photons give intrinsically less signal. This work will present evidence that the SMART 2K CCD system has been designed to overcome these difficulties. In particular the large area, 2K CCD CHIP allows for a small demagnification (1.83) with consequent high gain and a large face while retaining spatial resolution. The small demagnification, together with a careful optimization of the phosphor allows very high gains and thus allows confident detection of weak signals from poorly diffracting samples. The Goebel mirror optics for rotating anode sources give high intensity and parallelism, which allows for study of long axes. The result is a high DQE detector with good coverage of diffraction patterns even from large cells. Examples of detector tests and applications will be given. A comparison of results using other detector configurations and Mo and synchrotron sources will be given in this and related papers.