X-RAY DIFFRACTIOMETER--RIGAKU, D/MAX-RVBX & PSPC/MDG

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This proposal is for the acquisition of a Rigaku X-ray diffractometer system, the D/max-B series and X-ray micro diffraction unit, to replace a 25 year-old X-ray diffractometer. X-ray diffractometry is an important technique which is used or required by investigators from most of the departments at this Institution (Physical Chemistry, Inorganic Chemistry, Biochemistry, Bioengineering, Cariology, Dental materials, Ultrastructure and Histology). Investigators in these departments are engaged in research in the following areas: dental cariogenesis, preparation and solubility studies of hydroxy- and fluorapatites as prototypes of biological apatites, mineralization and structure of tooth and bone, and dental materials. Effective work on problems in these areas requires a superior diffractometer, capable of efficient, qualitative and quantitative, and microanalytical approaches. The proposed instrument will meet these needs: a) high intensity supply using a rotating anode, b) alignment and data analysis by a computer, and c) microbeam diffraction techniques with the position sensitive proportional counter (PSPC). The high power supply will shorten the measuring times, improve the accuracy of measurements with a support from the computer, and provide sufficient intensity even if the generated x-ray beam is collimated for the microbeam diffraction (10, 30 and 100 um in diameters). A highly significant further issue is that the proposed instrument has major advantages with respect to safety in that operator exposure to X-radiation is negligible and the instrument has interlocks which prevent accidental exposure of operators to X-radiation. These feature are absent from the existing equipment. A significant number of the anticipated research projects involve correlating morphological and histological features with the crystallographic properties of mineralized tissues and dental materials. The proposed microbeam diffractometer will fulfil these needs by providing PSPC to simultaneously accumulate diffraction intensity data for a wide-range of 20 angles from 5 through 150: In addition, the diffraction data can be obtained, using the proposed instrument, from a large number of small areas in the specimen within reasonable working times, thus providing an invaluable tool to ascertain the degree of heterogeneity of specimens. For the foregoing reasons we strongly believe that the new equipment would constitute a very significant enhancement of our Institute's capabilities in the area of dental research.