Charge-coupled-device fiber optic taper array x-ray detector for protein crystallography

Abstract

A large area, charge-couple-device (CCD) based fiberoptic taper array detector (APS-1) has been installed at the insertion-device beam line of the Structural Biology Center at the ANL Advanced Photon Source. The detector is used in protein crystallography diffraction experiments, where the objective is to measure the position and intensity of x-ray Bragg peaks in diffraction images. Large imaging area, very high spatial resolution, high x-ray sensitivity, good detective quantum efficiency, low noise, wide dynamic range, excellent stability and short readout time are all fundamental requirements in this application. The APS-1 detector converts the 2D x-ray patterns to a visible light images by a thin layer of x-ray sensitive phosphor. The phosphor coating is directly deposited on the large ends of nine fiberoptic tapers arranged in a 3 by 3 array. Nine, thermoelectrically cooled 1024 by 1024 pixel CCDs image the patterns, demagnified by the tapers. After geometrical and uniformity corrections, the nine areas give a continuous image of the detector face with virtually no gaps between the individual tapers. The 18 parallel analog signal- processing channels and analog-to-digital converters assure short readout time and low readout noise.