By incorporating advanced technology in fiberoptics, diode lasers, and holographic optical elements with knowledge gained from previous Spacelab work, we have produced a design of a versatile, miniaturized, stand alone, crystal solution growth chamber. Diagnostics instrumentation include the following: (1) crystal growth rate monitor, (2) growth/dissolution monitor with feedback, (3) solution diagnostics, (4) multiple wavelength holography, (5) single wavelength or color Schlieren with video recording. Availability of such a chamber will allow for much greater access to microgravity than is provided by presently available crystal growth research cells.
A need exists for understanding precisely how particles move and interact in a fluid in the absence of gravity. Such understanding is required, for example, for modeling and predicting crystal growth in space where crystals grow from solution around nucleation sites as well as for any study of particles or bubbles in liquids or in experiments where particles are used as tracers for mapping microconvection. We have produced an exact solution to the general equation of motion of particles at extremely low Reynolds number in microgravity that covers a wide range of interesting conditions. We have also developed diagnostic tools and experimental techniques to test the validity of the general equation . This program, which started in May, 1998, will produce the flight definition for an experiment in a microgravity environment of space to validate the theoretical model. We will design an experiment with the help of the theoretical model that is optimized for testing the model, measuring g, g-jitter, and other microgravity phenomena. This paper describes the goals, rational, and approach for the flight definition program. The first objective of this research is to understand the physics of particle interactions with fluids and other particles in low Reynolds number flows in microgravity. Secondary objectives are to (1) observe and quantify g-jitter effects and microconvection on particles in fluids, (2) validate an exact solution to the general equation of motion of a particle in a fluid, and (3) to characterize the ability of isolation tables to isolate experiments containing particle in liquids. The objectives will be achieved by recording a large number of holograms of particle fields in microgravity under controlled conditions, extracting the precise three-dimensional position of all of the particles as a function of time and examining the effects of all parameters on the motion of the particles. The feasibility for achieving these results has already been established in the ongoing ground-based NRA, which led to the virtual spaceflight chamber concept.
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.
During the International Microgravity Laboratory-1 (IML-1) mission it is planned to grow triglycine sulfate (TGS) crystals from aqueous solution using the modified Fluids Experiment System (FES). A special cooled sting technique will be used for solution crystal growth. The objectives of the experiment are as follows: (1) to grow crystals of TGS using the modified FES; (2) to perform holographic interferometric tomography of the fluid field in three dimensions; (3) to study the fluid motion due to g-jitter by multiple exposure holography of tracer particles; and (4) to study the influence of g-jitter on the growth rate.
Refinements of holographic instruments for the First International Microgravity Laboratory Spaceflight, scheduled for February 1992, are described. The refinements include addition of holographic optical elements (HOEs) to incorporate tomographic analysis of the solution concentration and particle image displacement velocimetry to measure convection. A variety of advanced diagnostic instruments were designed for future spaceflights and possibly in the space station. These new instruments employ fiber optics, diode lasers, and HOEs to enhance miniaturization and ruggedness and to reduce power requirements. The instruments can measure concentration, temperature, convection, and crystal growth rate. Instruments currently in use as well as the conceptual designs and applications of future laser- and holography-based instrumentation are described.
Ferroelectric Lithium Niobate (LN) possesses a combination of unique electrooptic, piezoelectric, pyroelectric, and photorefractive properties. These features make it suitable for applications in optical devices-as modulators, switches, and filters in communication systems and holographic recording medium, etc. Here, the growth of lithium Niobate doped with iron and doubly doped with iron and manganese ions will be described. The growth technique will be through Automatic Diameter Control Czochralski Design. From these grown crystals, critical electrooptical coefficients using null detection polarimetry are provided. The results of growth, electrooptic measurements, and some physical properties are compared and presented. Also, the use of doped LN crystals in devices is discussed.
Photonics/laser related technologies and applications rely on a steady supply of device quality single crystals. For more than a decade, the main focus has been on high performance nonlinear optical materials that comply with device manufacturing and end-use conditions such as high performance, high thermal, mechanical and chemical stability. To this end a variety of organic and semi-organic NLO materials have been successfully synthesized, purified and grown into bulk single crystals. In the process of growing bulk single crystals, various novel techniques and processes have been developed. In this presentation, results of synthesis and crystal growth processing of the various NLO materials such as methyl-(2,4-dinitrophenyl)-aminopropionate: 2-methyl-4-nitroaniline (MAP:MNA), L-arginine phosphate, L-Histidine tetrafluoroborate, L-arginie tetrafluoroborate and other isomorphs, pure and doped Bismuth silicon oxide, pure and doped Lithium niobate crystals will be discussed including challenges faced, novel techniques and experimental set-ups developed in growing large high quality crystals.
Abstract The voltage transformation behavior is obtained at unloaded condition in the piezoelect- ric transformers (PTs) for two different designs. One design involves disk-type (cylindrical shape) single-layer (piece) piezoelectric material, and another design involves two-layer rectangular-type piezoelectric materials. Each of these piezoelectric transformers possesses three terminals of which one terminal being common between the input pair of terminals and the output pair of terminals. The cylindrical disk-type PT is unipoled and designed with varying geometry of the electrode areas used as input and output terminals. The rectangular-type PT consists of two piezoelectric layers having each layer separately poled and designed with uniform thickness and rectangular electrode area. The disk PT has a ring electrode area (A R ) and a dot electrode area (A D ) on the same face used as input and output terminals. The common terminal has a full-face electrode on the opposite face. The ratio of the output dot electrode area to the input ring electrode area (A D /A R ) for the output voltage (V out = V D ) measured at the dot terminal and input voltage (V in = V R ) supplied at the ring terminal indicates leakage effect of the device attributing to the unelectroded region of the unipoled PTs. The same leakage effect is observed in the case of the reverse voltage transformation having switching input and output terminals (i.e., V in = V D and V out = V R such that A R /A D becomes the electrode area ratio). In both the cases (i.e., switching input and output terminals) of the voltage transformation the unipoled PTs exhibited step-up response except for the transformation factor. The results are presented in the form of output voltage as a function of applied frequency at fixed input voltage. The time dependence of the maximum output voltage corresponding to the peak applied frequency appears to exhibit transient response for the disk and rectangular PTs. Both step-up and step-down responses are noted for the rectangular PTs. *Present address of Ravindra B. Lal, Exploration Science and Technology Division, NASA-MSFC, Huntsville, AL 35812, USA. Keywords: Piezoelectric transformerinput voltageoutput voltagevoltage transforming ratiovoltage transformationfrequenciesetc. Acknowledgment This work is supported by Missile Defense Agency (MDA) contract # DAAD19-02-1-0365, and partial support of Mr. S. Seif for the Ph.D. dissertation is provided by NSF grant # NSF-HRD-0236425 and DEPSCoR grant # {DAAD19-01-1-0540}. Notes *Present address of Ravindra B. Lal, Exploration Science and Technology Division, NASA-MSFC, Huntsville, AL 35812, USA.
3-methoxy-4-hydroxy-benzaldehyde (MHBA) is one of the new organic materials that has become important for nonlinear optics in recent years because of its large second order nonlinear optical susceptibility and good blue transparency. Single crystals of MHBA were grown by a modified solution growth method. A study has been performed to select a suitable solvent for the growth of this material and to determine the effects of the solvent on the morphology of the crystals. These solvents were first studied to see their effects on the characteristic morphology of the material. From the results of morphology studies, methanol, ethanol, and MEK were selected as possible solvents for the growth. The solubility of MHBA was measured as a function of temperature in each solvent. From the solubility data, we discovered that a mixture of methanol to water (1:1) showed the most promise as a solvent for the growth of MHBA from solution. Crystals were grown using the three solvents in an effort to confirm the results of the solubility test. The properties of the material were studied using Differential Scanning Calorimetry, Vicker's hardness, and optical absorption spectrum. The results of the above measurements are described in this paper.
