PIXEL ARRAY DETECTOR FOR PROTEIN CRYSTALLOGRAPHY

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Funding is requested to build a very advanced Pixel Array Detector for protein crystallography, using the new Cadmium-Zinc-Telluride (CZT) material developed by a small company near UCSD (Aurora Technologies Corp.) and the new smart pixel readout circuitry developed at the Lawrence Berkeley Laboratory. While this detector could be used in a laboratory with a rotating x-ray anode, it really excels in a synchrotron beam. When finished, an array of these detectors would have a size of 15 cm x 15 cm with pixel size of 150 micromoles x 150 micromoles. It would be a direct x-ray photon counting device with an instantaneous readout and with a throughput of over 200 million counts per second. This detector is fast enough to collect a whole set of monochromatic data in 180 seconds (3 minutes). It will be more sensitive than a CCD detector and will come with an electronic shutter time down to a few microseconds. It can be used for time-resolved Laue diffraction experiments since it will have enough histogram memory to store up to 16 successive pictures. For experiments that can't be repeated, the exposure time for each picture would be about 50 ms or longer with enough counting statistics for a 3% data set. For repeatable experiments, the exposure time can be as short as a few milliseconds. Another property of this detector is that it can select a range of wavelength of the x-ray photons, therefore can be very helpful in sorting out overlapping reflections in a Laue diffraction experiment. When finished, this detector will very probably be used at the synchrotron beam for protein crystallography that is being built on the Advanced Light Source (ALS) at Berkeley Lawrence Laboratory. Since CZT material can detect high energy X-ray (up to 100 keV) very efficiently, this project will greatly help the development of advanced detectors for nuclear medicine and mammography.