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Multiple CCD detector for macromolecular X‐ray crystallography
Author(s) -
Phillips Walter C.,
Stanton Martin,
Stewart Alexander,
Qian Hua,
Ingersoll Charles,
Sweet Robert M.
Publication year - 2000
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889899015666
Subject(s) - detective quantum efficiency , optics , optical transfer function , full width at half maximum , detector , physics , x ray detector , dot pitch , noise (video) , pixel , photon , synchrotron radiation , materials science , image quality , artificial intelligence , computer science , image (mathematics)
A charge‐coupled device (CCD)‐based detector designed for macromolecular crystallography is described. The detector has an area of 200 × 200 mm, a readout time of 1.6 s, and total noise equivalent to approximately three 12 keV X‐ray photons per pixel. The detector is constructed from a 2 × 2 array of four identical units, each unit consisting of a 4.1:1 demagnifying fiber‐optic taper bonded to a 1 k × 1 k, 24 µm pixel, CCD sensor. Each CCD is read out in parallel though four channels and digitized to 16 bits. A Gd 2 O 2 S phosphor X‐ray‐to‐light converter bonded to an aluminized‐plastic film is held in contact with the input surfaces of the fiber‐optic tapers with an air pillow. The full width at half‐maximum (FWHM) of the point response function is 120 µm, the response is linear to better than 1% over the entire range of intensity from background to nearly full well, the gain is 3.4 e per 8 keV incident X‐ray photon, the noise is 12.6 e per pixel for a 10 s integration time, the modulation transfer function (MTF) is 0.35 at 5 line pairs (lp) mm −1 (the Nyquest frequency), and the measured detective quantum efficiency (DQE) is 0.74 for relatively strong Bragg peaks. Data collected from crystallographic studies with synchrotron radiation are presented. In an anomalous difference Patterson map for a data set collected in 40 min on a monoclinic myoglobin crystal, the magnitude of the Fe–Fe peaks is 18 times the standard uncertainty of the map.