A PIXEL ARRAY DETECTOR FOR PROTEIN CRYSTALLOGRAPHY

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In this revised application, funding is requested to design, build and test a modular 50 x 50 pixel array detector that can collect data extremely fast and that can sustain very high radiation level without damage. The Digital Pixel Array Detector will consist of an array of silicon pixel detectors of the size of 150 mu x 150 mu bump bonded to an array of readout circuits also with pixels of the same size. Using microelectronic methods, the readout circuitry, in the form of an ASIC chip, incorporated sophisticated electronics allowing a series of fast readouts in parallel to achieve the desired throughput rate. A 16x16 pixel prototype detector is now working and is being tested exhaustively. Funding is requested to extend this prototype to a modular 50 x 50 pixel detector that can be assembled later on to form a very large detector (up to 2000 x 2000 pixel). Each pixel would collect X-rays at a rate up to10 (6) photons/sec and the throughput rate for the whole detector will be 4x10(11) photons/sec. With almost no readout dead time, it is capable of collecting a complete monochromatic data in 90 seconds. It comes with an electronic shutter that can be timed down to a few microseconds, and is very well suited to time resolved Laue diffraction experiments since it will have enough histogram memory to store up to 8 or 16 successive pictures. For experiments that cannot be repeated, the exposure time would be about 10 ms or longer with enough statistics for a 3% data set. For repeatable experiments, the exposure time can be as small as a few milliseconds. Another property of this detector is that it can select a range of wavelengths of X-ray photons, therefore it can be very helpful in sorting out overlapping reflections in a Laue diffraction experiment.