Area detector design. Pt. 1

Classical expressions of area detector performance, the detective quantum efficiency (DQE) and the dynamic range (DR), provide a description of the fundamental properties of a detector. However, since they contain no information regarding the experimental context in which the detector will be used, they do not necessarily provide an accurate prediction of how the detector will perform during data collection. In this paper, the standard definitions of the DQE and DR are extended to provide four new expressions of an area detector's performance: (1) The detective collection efficiency (DCE) - the fraction of the required measurements which can be made at one time by the detector, multiplied by the DQE; (2) the experimental detective quantum efficiency (XDQE) - the ratio of the variance in the measurement of interest made with the detector to that made with an ideal detector; (3) the experimental detective collection efficiency (XDCE) - the fraction of the required measurements which can be made at one time by the detector, multiplied by the XDQE; (4) the experimental dynamic range (XDR) - the dynamic range of the detector for the measurement of interest. Using these general expressions, equations are developed to model the performance of a CCD-based detector for X-ray crystallography. This formulation allows experimental conditions such as the unit cell size, peak size and profile, maximum reciprocal-space resolution and beam characteristics to be incorporated into the design of an area detector. (orig.)