MERCURIC IODIDE ARRAYS FOR SYNCHROTRON RADIATION

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The long term objective of this research is to develop the capability to build large arrays of energy dispersive x-ray detectors for installation and use at Synchrotron Radiation (SR) and other x-ray research facilities. Each array element would have energy resolution of 300 eV or better at 6 KeV and a count rate capability exceeding 50,000 cps. Completed arrays, containing upwards of 100 elements, could count at effective rates over 5x10'6 cps and are targeted to cost about $1000/elements. Coupled to the next generation of high brightness SR x- ray sources, these arrays would lead to a greatly enhanced ability to obtain the direct structural, bonding and compositional information which has been found to be so useful in unravelling the mechanisms by which proteins and enzymes function at the molecular level. The arrays could be organized either linearly, as diffraction detectors, or 2-dimensionally as fluorescence detectors for XANES,EXAFS or scanning fluorescence microscopy. The projected increases in countrate capability and solid angle collection efficiency would make research possible at ultra-low dilutions or as a function of time, temperature, or concentration which would otherwise be unfeasible or impossible. HgI2 was chosen because its room temperature operation and ease of passivation vastly simplify detector design and construction. The previous proposal showed that HgI2 can be arrayed by developing a 5 element detector+FET submodule package designed to be closely packed to create an array detector system front end. This proposal's specific goal is to complete working energy dispersive array detector systems of 20, 100 and 400 elements. The major intermediate development include: techniques to produce the submodules without degrading their performance,a submodules mounting technique to assure thermal contact and rigidity with electronic isolation; advanced miniaturized processing electronics to support the front end; and system hardware and software integration. The use of existing commercial electronics for the 400 element detector, for example, would cost over $1.2M and fill 5 racks with a tangle of equipment too complex for effective use. The proposed electronics modules would reduce costs by a factor of over 5, volume by 10, power consumption by 5, and would integrate amplifier, pileup rejection and single channel analysis functions into a single, computer controlled CAMAC package. All system functions, including calibration, energy tuning, data collection and fault detection will then by automated by creation of appropriate control software. The proposed advanced in electronic function will be accomplished by taking existing designs, simplifying, specializing and optimizing them for this specific application, and then miniaturizing them by the hybridization process. The completed detector systems will be deployed at national synchrotron laboratories in support of existing NIH biotechnology research programs.