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DOE OSTI2020

Materials Data on CdWO4 by Materials Project

CdWO4 is zeta iron carbide-derived structured and crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. W6+ is bonded to six O2- atoms to form distorted WO6 octahedra that share corners with eight equivalent CdO6 octahedra and edges with two equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 40–57°. There are a spread of W–O bond distances ranging from 1.83–2.14 Å. Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with eight equivalent WO6 octahedra and edges with two equivalent CdO6 octahedra. The corner-sharing octahedra tilt angles range from 40–57°. There are a spread of Cd–O bond distances ranging from 2.27–2.44 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent W6+ and one Cd2+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one W6+ and two equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗

NASA NTRS1994

X-ray remote sensing and in-situ spectroscopy for planetary exploration missions and gamma-ray remote sensing and in-situ spectroscopy for planetary exploration missions

Detectors that will be used for planetary missions must have their responses calibrated in a reproducible manner. A calibration facility is being constructed at Schlumberger-Doll Research for gamma and x ray detectors. With this facility the detector response can be determined in an invariant and reproducible fashion. Initial use of the facility is expected for the MARS94 detectors. Work is continuing to better understand the rare earth oxyorthosilicates and to define their characteristics. This will allow a better use of these scintillators for planetary missions. In a survey of scintillating materials two scintillators were identified as promising candidates besides GSO, LSO, and YSO. These are CdWO4 and CsI(Tl). It will be investigated if a detector with a better overall performance can be assembled with various photon converters. Considerable progress was achieved in photomultiplier design. The length of an 1 inch diameter PMT could be reduced from 4.2 to 2.5 inches without performance degradation. This technology is being employed in the gamma ray detector for the NEAR project. A further weight and size reduction of the detector package can be achieved with miniaturized integrated power supplies.

Mahdavi, M.↗