Overview of the DPAD detector for protein crystallography

A 2D photon counting digital pixel array detector is being designed for static and time resolved protein crystallography. This room temperature detector will significantly enhance monochromatic and polychromatic protein crystallographic throughput data rates by more than two or three orders of magnitude when compared to present data collection systems. The detector has an unbounded photon counting dynamic range and exhibits superior spatial resolution when compared to present crystallographic phosphor imaging plates or phosphor coupled CCD detectors. The detector is a high resistivity N-type Si with a pixel pitch of (150 X 150) microns, and a thickness of 300 microns that is bump bonded to an application specific integrated circuit. The event driven readout of the detector is based on the column architecture and allows an independent pixel bit rate above 1 million photons/sec. The device provides energy discrimination and sparse data readout that yields minimal dead time. This type of architecture allows an almost continuous (frame-less) 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 1011 photons/sec for the complete detector appears achievable. This paper will present an overview of the hybridized detector performance which includes the analog amplifier response and the photon counting capabilities of the (16 X 16) array operating with both digital and analog circuitry. Also the operation of the serial interface will be described.