Status of the digital pixel array detector for protein crystallography

A two-dimensional photon counting digital pixel array detector is being des igned for static and time resolved protein crystallography. The room temper ature detector will significantly enhance monochromatic and polychromatic p rotein crystallographic through-put data rates by more than three orders of magnitude. The detector has an almost infinite photon counting dynamic ran ge and exhibits superior spatial resolution when compared to present crysta llographic phosphor imaging plates or phosphor coupled CCD detectors. The d etector is a high resistivity N-type Si with a pixel pitch of 150 x 150 mu m, and a thickness of 300 mu m, and is bump bonded to an application specif ic integrated circuit. The event driven readout of the detector is based on the column architecture and allows an independent pixel hit rate above 1 m illion photons/s/pixel. The device provides energy discrimination and spars e data readout which yields minimal dead-time. This type of architecture al lows a continuous (frameless) data acquisition, a feature not found in any current detector being used for protein crystallographic applications. For the targeted detector size of 1000 x 1000 pixels, average hit rates greater than 8 billion photons/s for the complete detector appears achievable. Thi s paper will present a review of the 8 x 8 detector array pixel performance which includes the analog amplifier response and the photon counting capab ilities. In addition, operational results of a 16 x 16 detector array proto type, that includes both the analog amplifier and digital readout circuitry functioning together on one integrated circuit. (C) 1999 Elsevier Science B.V. All rights reserved.