L. van den Berg

Constellation Technology (United States)

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C. Ortale

S.P.E.C.I.E.S.

R. B. James

Savannah River National Laboratory

W.F. Schnepple

Marina Del Rey Hospital

M. Schieber

Hebrew University of Jerusalem

T. E. Schlesinger

Johns Hopkins University

X. J. Bao

Shenyang Agricultural University

A. Bürger

Fisk University

A. Y. Cheng

Allen Institute

Kenneth R. Pohl

Sandia National Laboratories California

Bruce Steiner

National Institute of Standards and Technology

Cooperative Institutions

Constellation Technology (United States)

University of Alberta

Sandia National Laboratories California

National Institute of Standards and Technology

Sandia National Laboratories

Oak Ridge National Laboratory

Fisk University

Alabama Agricultural and Mechanical University

S.P.E.C.I.E.S.

Lawrence Livermore National Laboratory

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CHANGES IN SKELETAL STATUS IN OSTEOPOROSIS

Journal of Computer Assisted Tomography (1982)

L. van den Berg T. N. Hangartner T.R. Overton P. M. Crockford

van den Berg, L.; Hangartner, T. N.; Overton, T. R.; Crockford, P. M. Author Information

10.1097/00004728-198202000-00064

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A study of mercuric iodide near melting using differential scanning calorimetry, Raman spectroscopy and X-ray diffraction

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment (1989)

A. Bürger S. Morgan Haoran Jiang E. Silberman M. Schieber

10.1016/0168-9002(89)91348-x

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Citations (6)

Detached Melt and Vapor Growth of InI in SUBSA Hardware

A.G. Ostrogorsky Vladimir V. Riabov M. P. Volz L. van den Berg A. Churilov

Indium iodide (InI) is a promising wide energy band gap nuclear detector material. It is ideal for space experiments because it is non-toxic and has a relatively low melting point of only 351 degrees Centigrade. However, it has been established that melt-grown crystals contain a large amount of second phase inclusions/precipitates. The typical size of inclusions are 1 to 27 microns in diameter, while the volume fraction of all sizes is 300 to 600 parts per million. The SEM-EDS (Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy) analysis of the inclusions has revealed that they all contain oxygen and some contain carbon. At present, under sponsorship of NASA and CASIS (Center for the Advancement of Science in Space), we are conducting ground-based experiments with InI in preparation for the flight experiments to be conducted in the SUBSA (Solidification Using a Baffle in Sealed Ampoules) furnace in the Microgravity Science Glovebox at the International Space Station, planned for the summer/fall of 2017. Earth-based experiments include melt and vapor growth conducted in the SUBSA ground unit, measurements of the volumetric expansion coefficient of the melt, and measurements of the wetting angle of molten InI. Finite element modeling has been conducted to optimize the design of the flight ampoules. Alloying with Tl and Ga has given promising results.

Ampoule

Glovebox

Tray

Metallography

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Growth of HgI2 Single Crystalsin Spacelab I

Journal of Spacecraft and Rockets (1979)

W.F. Schnepple L. van den Berg N. Skinner

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Spacecraft design

Space environment

space technology

Space vehicle

10.2514/3.57682

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Citations (4)

<title>High-resolution synchrotron x-radiation diffraction imaging of crystals grown in microgravity and closely related terrestrial crystals</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1991)

Bruce Steiner R.C. Dobbyn David R. Black Harold E. Burdette M. Kuriyama

Irregularities in three crystals grown in space and four terrestrial crystals have been compared by high resolution monochromatic synchrotron x-radiation diffraction imaging. For two of the materials, mercuric iodide and lead tin telluride, features consistent with the presence of additional phases in terrestrial samples have been suppressed in the comparable crystals grown in microgravity. Comparison of the images of highly purified terrestrial mercuric iodide with those of lower purity space and terrestrial material suggests specific detector performance models. These models ascribe the improved performance of detectors made from space-grown mercuric iodide to reduction in a widely dispersed impurity phase rather than to extreme macroscopic lattice regularity. While the general grain structure of lead tin telluride is not strongly affected by growth in microgravity, the subgrain uniformity of the space crystal is substantially higher than that of the comparable terrestrial crystal. The greater uniformity is associated with suppression of the second phase that appears to be characteristic of the terrestrial crystal examined.

Crystal (programming language)

10.1117/12.49594

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Processing {alpha}-mercuric iodide by zone refining

A. Bürger S. H. Morgan D. O. Henderson Ye Biao K. Zhang

An investigation is being conducted on zone refining {alpha}-mercuric iodide. Analytical studies using differential scanning calorimetry and anion chromatography indicate that impurities are segregated mainly at the end where zone travel terminates. Early results indicate that single crystals can be readily grown from zone refined material, and the effects of the process on the performance of radiation detectors fabricated from {alpha}-mercuric iodide are being evaluated.

Zone melting

Refining (metallurgy)

Alpha (finance)

Source

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HgI2 near-band-gap photoluminescence structure and its relationship to nuclear detector quality

Journal of Applied Physics (1988)

Deniz Wong T. E. Schlesinger R. B. James C. Ortale L. van den Berg

The low-temperature photoluminescence spectra of several mercuric iodide detectors and off-stoichiometric bulk material have been characterized. Phonon energies have been determined with Raman spectroscopy over a range of temperatures. In earlier work some of the near-band-gap photoluminescence features were identified as phonon replicas. After careful examination of Raman and photoluminescence data, we find that one or perhaps more of these features is probably due to shallow electronic levels related to native defects. Suggestions as to the relationship between photoluminescence peaks and detector quality are made.

Photoluminescence excitation

Stoichiometry

10.1063/1.341711

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Citations (22)

Process and yield enhancements for epitaxially grown mercuric iodide crystals

L. van den Berg M.R. Saleno R.D. Vigil J. L. Baker Yuefeng Zhu

Mercuric iodide single crystals have been used successfully as gamma radiation detectors for many years. Recently a different growth method called `seeded homoepitaxy' has been studied. This method has the advantage of growing detector-sized volumes with a thickness of about 10mm in a highly accelerated timeframe. The electronic transport properties of a mercuric iodide detector have been shown to depend primarily upon two factors. The first is material quality, which is predominantly determined by the levels of organic and inorganic impurities and the compound stoichiometry. The second is the integrity of the crystalline structure (type and density of defects), which depends mostly upon the thermal growth profile, conditions inside the growth chamber, and seed preparation. Recent improvements made to the epitaxial process have resulted in a detector performance for both planar and pixelated devices that rivals that of traditional ampoule-grown crystals. This increases the usefulness of devices in field applications. Changes in the seed attachment and preparation methods have been successful at reducing crystalline defects by about 90%. This has been substantiated using a method of measuring and recording defect density that combines laser backscatter with digital photography. Improvements in the mercuric iodide growth process, bulk material impurity reduction, and the laser backscatter digital photography will be described and the results discussed.

10.1109/nssmic.2010.5874552

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AN EXPERIMENTAL STUDY OF THE ADFR PROCESS IN HUMAN SUBJECTS USING GAMMA RAY CT

Journal of Computer Assisted Tomography (1983)

C. Harley T. N. Hangartner T.R. Overton L. van den Berg P. M. Crockford

Harley, C. H.; Hangartner, T. N.; Overton, T. R.; van den Berg, L.; Crockford, P. M. Author Information

10.1097/00004728-198306000-00055

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Influence of temperature upon dislocation mobility and elastic limit of single crystal HgI/sub 2/

F. Milstein Bruce Farber K. Kim L. van den Berg W.F. Schnepple

The practical importance of studying mechanical properties and dislocation structure of HgI/sub 2/ is reviewed briefly. Specifically, the performance of single crystal HgI/sub 2/ radiation detectors is evidently sensitive to crystalline imperfections; the dislocation structure, in turn, can be altered during detector fabrication, depending upon the mechanical properties of the crystal and the stresses to which the crystal is subjected. The influence of temperature upon dislocation mobility and plasticity in vapor-grown crystals of mercuric iodide is examined. Dislocation mobiity is determined by measuring the lengths of the longest arms of dislocation etch pit rosettes on (001) surfaces following microhardness indentation and chemical etch. Measurements were made in the range from room temperature to the phase transition temperature of 127/sup 0/C. Dislocation mobility was found to be an increasing function of temperature, with the effect accelerating as the phase transition is approached. Increasing temperature was also found to lower the critical resolved shear stress for plastic deformation on slip on (001) planes. In these contexts, the vapor-grown crystals are clearly softer at their elevated growth temperatures. The results are discussed in terms of a dislocation model involving soft and hard glide dislocations.

Indentation

Atmospheric temperature range

Crystal (programming language)

10.2172/6715487

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