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Sample records for horizontal-typed mocvd chamber

  1. Safety-Enclosure System For MOCVD Process Chamber

    NASA Technical Reports Server (NTRS)

    Singletery, James, Jr.; Velasquez, Hugo; Warner, Joseph

    1995-01-01

    Safety-enclosure system filled with nitrogen surrounds reaction chamber in which metallo-organic chemical vapor deposition (MOCVD) performed. Designed to protect against explosions and/or escaping toxic gases and particulates. Gas-purification subsystem ensures during loading and unloading of process materials, interior of MOCVD chamber exposed to less than 1 ppm of oxygen and less than 5 ppm of water in nitrogen atmosphere. Toxic byproducts of MOCVD process collected within inert atmosphere. Enclosure strong enough to contain any fragments in unlikely event of explosion.

  2. Solid source MOCVD system

    DOEpatents

    Hubert, Brian N.; Wu, Xin Di

    1998-01-01

    A system for MOCVD fabrication of superconducting and non-superconducting oxide films provides a delivery system for the feeding of metalorganic precursors for multi-component chemical vapor deposition. The delivery system can include multiple cartridges containing tightly packed precursor materials. The contents of each cartridge can be ground at a desired rate and fed together with precursor materials from other cartridges to a vaporization zone and then to a reaction zone within a deposition chamber for thin film deposition.

  3. Solid source MOCVD system

    DOEpatents

    Hubert, B.N.; Wu, X.D.

    1998-10-13

    A system for MOCVD fabrication of superconducting and non-superconducting oxide films provides a delivery system for the feeding of metallorganic precursors for multi-component chemical vapor deposition. The delivery system can include multiple cartridges containing tightly packed precursor materials. The contents of each cartridge can be ground at a desired rate and fed together with precursor materials from other cartridges to a vaporization zone and then to a reaction zone within a deposition chamber for thin film deposition. 13 figs.

  4. Vacuum MOCVD fabrication of high efficience cells

    NASA Technical Reports Server (NTRS)

    Partain, L. D.; Fraas, L. M.; Mcleod, P. S.; Cape, J. A.

    1985-01-01

    Vacuum metal-organic-chemical-vapor-deposition (MOCVD) is a new fabrication process with improved safety and easier scalability due to its metal rather than glass construction and its uniform multiport gas injection system. It uses source materials more efficiently than other methods because the vacuum molecular flow conditions allow the high sticking coefficient reactants to reach the substrates as undeflected molecular beams and the hot chamber walls cause the low sticking coefficient reactants to bounce off the walls and interact with the substrates many times. This high source utilization reduces the materials costs power device and substantially decreases the amounts of toxic materials that must be handled as process effluents. The molecular beams allow precise growth control. With improved source purifications, vacuum MOCVD has provided p GaAs layers with 10-micron minority carrier diffusion lengths and GaAs and GaAsSb solar cells with 20% AMO efficiencies at 59X and 99X sunlight concentration ratios. Mechanical stacking has been identified as the quickest, most direct and logical path to stacked multiple-junction solar cells that perform better than the best single-junction devices. The mechanical stack is configured for immediate use in solar arrays and allows interconnections that improve the system end-of-life performance in space.

  5. Monitoring of MOCVD reactants by UV absorption

    SciTech Connect

    Baucom, K.C.; Killeen, K.P.; Moffat, H.K.

    1995-07-01

    In this paper, we describe how UV absorption measurements can be used to measure the flow rates of metal organic chemical vapor deposition (MOCVD) reactants. This method utilizes the calculation of UV extinction coefficients by measuring the total pressure and absorbance in the neat reactant system. The development of this quantitative reactant flow rate monitor allows for the direct measurement of the efficiency of a reactant bubbler. We demonstrate bubbler efficiency results for TMGa, and then explain some discrepancies found in the TMAl system due to the monomer to dimer equilibrium. Also, the UV absorption spectra of metal organic and hydride MOCVD reactants over the wavelength range 185 to 400 nm are reported.

  6. Properties of boron-doped ZnO thin films grown by using MOCVD

    NASA Astrophysics Data System (ADS)

    Choi, In-Hwan

    2013-11-01

    Boron-doped ZnO thin films were prepared by using metal organic chemical-vapor deposition (MOCVD) with diethyl zinc and water as precursors and B2H6 as the dopant gas. The effects of the flow rates of H2O and B2H6 on the growth and the electrical properties of boron-doped ZnO thin film were investigated. The maximum carrier concentration and mobility and the minimum resistivity obtained under these experimental conditions were 7 × 1020 /cm3, 42 cm2 /V·sec and 4 × 10-4 Ω·cm, respectively, at room temperature. The electrical properties, growth rates, transmittances, and surface morphologies of the ZnO:B films grown using MOCVD are strongly affected by growth conditions such as the relative flow rates of the precursors and dopant gases and the chamber pressure, and these effects are discussed in detail in this article.

  7. Surface Science in an MOCVD Environment: Arsenic on Vicinal Ge(100)

    SciTech Connect

    McMahon, W. E.; Olson, J. M.

    1998-11-01

    Scanning tunneling microscope (STM) images of arsine-exposed vicinal Ge(100) surfaces show that most As/Ge steps are reconstructed, and that a variety of different step structures exist. The entire family of reconstructed As/Ge steps can be divided into two types, which we have chosen to call ''single-row'' steps and ''double-row'' steps. In this paper we propose a model for a double-row step created by annealing a vicinal Ge(100) substrate under an arsine flux in a metal-organic chemical vapor deposition (MOCVD) chamber.

  8. System innovations for aerosol MOCVD of YBCO superconducting thin films

    NASA Astrophysics Data System (ADS)

    Nelms, David Martin

    System innovations were developed for metallo-organic chemical vapor deposition (MOCVD) in order to achieve two main objectives: to fully characterize a novel feed system while and to demonstrate uniform, superconducting thin films over a 2 inch diameter. The novel aerosol feed system was fully characterized and improved by performing solubility and carbon tests with different metallo-organic solvents and by thermally mapping the heating section. The gas flow profiles in the reactor chamber were modeled with a finite-element software package called Fluent. This enabled us to study different nozzles for improving the uniformity of the velocity near the substrate and the uniformity of the depositions. Depositions were then performed to test the validity of the computer model and to determine correct molar feed ratios. The uniformity was measured with a scanning electron microscope (SEM) while the film compositions were analyzed with a X-Ray photoelectron spectroscopy system (XPS). Once the correct feed compositions were determined, this ratio was used along with the feed nozzle designed to deposit uniform, superconducting thin films.

  9. Flow chamber

    DOEpatents

    Morozov, Victor [Manassas, VA

    2011-01-18

    A flow chamber having a vacuum chamber and a specimen chamber. The specimen chamber may have an opening through which a fluid may be introduced and an opening through which the fluid may exit. The vacuum chamber may have an opening through which contents of the vacuum chamber may be evacuated. A portion of the flow chamber may be flexible, and a vacuum may be used to hold the components of the flow chamber together.

  10. Mocvd of Tin Oxide for Gas Sensors.

    NASA Astrophysics Data System (ADS)

    Weglicki, Peter Stanislaw

    1990-01-01

    Available from UMI in association with The British Library. Requires signed TDF. Thin films of a wide variety of materials can be produced using an assortment of physical and chemical techniques. Such techniques are reviewed and compared, with particular reference to the deposition of tin oxide films. In the present study, MOCVD (Metal organic chemical vapour deposition) was used to grow thin films of tin oxide from dibutyltin diacetate precursor on a variety of substrates. A series of reactor prototypes were developed in accordance with specific requirements of reproducibility and process control. The evolution of the designs leading to the final working system is detailed. The theory of MOCVD is given with particular reference to the reactor used in this project. The effects of various deposition parameters on tin oxide film growth rates were investigated, and the results are discussed with reference to the deposition kinetics in the system. Films were characterised by optical interferometry, optical and electron microscopy, X-ray diffraction, Rutherford backscattering and electrical measurements. The films were generally uniform, conducting and polycrystalline, and were comprised of very small grains, resulting in a high density. A specific application of metal oxide materials is in solid state gas sensors, which are available in various forms and operate according to different mechanisms. These are compared and a detailed account is given on the theory of operation of surface conductivity modulated devices. The application of such devices based on tin oxide in thin film form was investigated in the present work. The prepared sensor samples were comprised of very small grains, resulting in a high density. The observation that preferred (310) orientation occured in thicker films, can be attributed to dendritic growth. The sensors generally showed response to numerous reducing gas ambients, although there was evidence of a degree of selectivity against methane

  11. Transport phenomena and the effects of reactor geometry for epitaxial GaN growth in a vertical MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Tseng, Chien-Fu; Tsai, Tsung-Yen; Huang, Yen-Hsiu; Lee, Ming-Tsang; Horng, Ray-Hua

    2015-12-01

    In this study a numerical simulation was carried out to analyze the transport phenomena in a vertical type metal organic chemical vapor deposition (MOCVD) reactor for Gallium Nitride (GaN) growth. The simulated results were compared and validated by experiment. The effects of showerhead design and chamber height are investigated and discussed. It was found that, by properly adjusting the height of the chamber, both the growth rate and film uniformity could be significantly improved. This is attributed to the suppression of the thermal and mass transfer boundary layers by the injection flow of reacting gas mixtures, as well as the confined vertical vortices caused by the geometry of the reduced space. However, inappropriate design of the distance between the showerhead and the susceptor can result in uneven distribution of the organic source in the vicinity of the substrate surface resulting in an uneven growth rate of the GaN film. Consequently, there exists an optimal chamber height that will give the best growth rate and uniformity to the GaN film as discussed in this study. This study provides comprehensive insight into the transport phenomena of GaN growth that includes coupled heat and mass transfer as well as chemical reactions. The results provide important information in a succinct format and enable decisions to be made about the showerhead and the geometrical design and size of a vertical MOCVD reactor.

  12. Radiative efficiency of MOCVD grown QD lasers

    NASA Astrophysics Data System (ADS)

    Mawst, Luke; Tsvid, Gene; Dudley, Peter; Kirch, Jeremy; Park, J. H.; Kim, N.

    2010-02-01

    The optical spectral gain characteristics and overall radiative efficiency of MOCVD grown InGaAs quantum dot lasers have been evaluated. Single-pass, multi-segmented amplified spontaneous emission measurements are used to obtain the gain, absorption, and spontaneous emission spectra in real units. Integration of the calibrated spontaneous emission spectra then allows for determining the overall radiative efficiency, which gives important insights into the role which nonradiative recombination plays in the active region under study. We use single pass, multi-segmented edge-emitting in which electrically isolated segments allow to vary the length of a pumped region. In this study we used 8 section devices (the size of a segment is 50x300 μm) with only the first 5 segments used for varying the pump length. The remaining unpumped segments and scribed back facet minimize round trip feedback. Measured gain spectra for different pump currents allow for extraction of the peak gain vs. current density, which is fitted to a logarithmic dependence and directly compared to conventional cavity length analysis, (CLA). The extracted spontaneous emission spectrum is calibrated and integrated over all frequencies and modes to obtain total spontaneous radiation current density and radiative efficiency, ηr. We find ηr values of approximately 17% at RT for 5 stack QD active regions. By contrast, high performance InGaAs QW lasers exhibit ηr ~50% at RT.

  13. Bakeout Chamber Within Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    Taylor, Daniel M.; Soules, David M.; Barengoltz, Jack B.

    1995-01-01

    Vacuum-bakeout apparatus for decontaminating and measuring outgassing from pieces of equipment constructed by mounting bakeout chamber within conventional vacuum chamber. Upgrade cost effective: fabrication and installation of bakeout chamber simple, installation performed quickly and without major changes in older vacuum chamber, and provides quantitative data on outgassing from pieces of equipment placed in bakeout chamber.

  14. Bakeout Chamber Within Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    Taylor, Daniel M.; Soules, David M.; Barengoltz, Jack B.

    1995-01-01

    Vacuum-bakeout apparatus for decontaminating and measuring outgassing from pieces of equipment constructed by mounting bakeout chamber within conventional vacuum chamber. Upgrade cost effective: fabrication and installation of bakeout chamber simple, installation performed quickly and without major changes in older vacuum chamber, and provides quantitative data on outgassing from pieces of equipment placed in bakeout chamber.

  15. In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P.; Gallois, B.; Kear, B.

    1990-01-01

    Metalorganic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T( sub c) greater than 90 K and Jc approx. 10 to the 4th power A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  16. In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P. E.; Kear, B.; Gallois, B.

    1991-01-01

    Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  17. Exposure chamber

    DOEpatents

    Moss, Owen R.; Briant, James K.

    1983-01-01

    An exposure chamber includes an imperforate casing having a fluid inlet at the top and an outlet at the bottom. A single vertical series of imperforate trays is provided. Each tray is spaced on all sides from the chamber walls. Baffles adjacent some of the trays restrict and direct the flow to give partial flow back and forth across the chambers and downward flow past the lowermost pan adjacent a central plane of the chamber.

  18. Exposure chamber

    DOEpatents

    Moss, Owen R.

    1980-01-01

    A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

  19. Wire chamber

    DOEpatents

    Atac, Muzaffer

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  20. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  1. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Astrophysics Data System (ADS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-04-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  2. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1991-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectrics having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writing capability, complex device structures like three terminal hybrid semiconductor/superconductor transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray deffraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  3. Gas phase depletion and flow dynamics in horizontal MOCVD reactors

    NASA Astrophysics Data System (ADS)

    Van de Ven, J.; Rutten, G. M. J.; Raaijmakers, M. J.; Giling, L. J.

    1986-08-01

    Growth rates of GaAs in the MOCVD process have been studied as a function of both lateral and axial position in horizontal reactor cells with rectangular cross-sections. A model to describe growth rates in laminar flow systems on the basis of concentration profiles under diffusion controlled conditions has been developed. The derivation of the growth rate equations includes the definition of an entrance length for the concentration profile to developed. In this region, growth rates appear to decrease with the 1/3 power of the axial position. Beyond this region, an exponential decrease is found. For low Rayleigh number conditions, the present experimental results show a very satisfactory agreement with the model without parameter fitting for both rectangular and tapered cells, and with both H 2 and N 2 as carrier gases. Theory also predicts that uniform deposition can be obtained over large areas in the flow direction for tapered cells, which has indeed been achieved experimentally. The influence of top-cooling in the present MOCVD system has been considered in more detail. From the experimental results, conclusions could be drawn concerning the flow characteristics. For low Rayleigh numbers (present study ≲ 700) it follows that growth rate distributions correspond with forced laminar flow characteristics. For relatively high Rayleigh numbers (present work 1700-2800), free convective effects with vortex formation are important. These conclusions are not specific for the present system, but apply to horizontal cold-wall reactors in general. On the basis of the present observations, recommendations for a cell design to obtain large area homogeneous deposition have been formulated. In addition, this work supports the conclusion that the final decomposition of trimethylgallium in the MOCVD process mainly takes place at the hot substrate and susceptor and not in the gas phase.

  4. MOCVD of multimetal and noble metal films

    NASA Astrophysics Data System (ADS)

    Endle, James Patrick

    2000-11-01

    Carbon content in TiN films produced with tetrakis(dimethylamino)titanium (TDMAT) and methylhydrazine or dimethylhydrazine can be controlled at or below 10% with a N/Ti ratio of ˜1.3 at growth temperatures between 573 and 723 K. Post-dosing either hydrazine on a CVD TiN film results in additional N-Ti bonds, indicating a surface reaction between the two precursors occurs. Co-dosing hydrazine-like compounds with larger alkyl ligands than methyl resulted in additional carbon incorporation in the TiN film. A growth system, consisting of a load lock and growth chamber, and a precursor pyrolysis system were designed and built to study metalorganic chemical vapor deposition. Addition of a bubbler and a direct liquid injection system allowed for the vaporization of solid and liquid precursors and solutions of multiple precursors. A precursor pyrolysis system was designed for high and low vapor pressure precursors and high carrier gas flow rates. The systems were used to study (Al,Ti)N and Ir film growth. (Al,Ti)N was used as a template to study the incorporation of elements into a multimetal chemical vapor deposited film using NH3 and a DLI solution of TDMAT and the tris(dimethylarnino)alane dimer (TDMAA) in toluene-NH 3 significantly decreases the decomposition temperature of both precursors. Carbon was reduced by increasing the NH3 partial pressure, and the Al incorporation was increased by increasing the TDMAA/TDMAT ratio in the DLI solution. Exposure to ambient resulted in significant oxygen incorporation and the removal of carbon and nitrogen from the (AI,Ti)N film. Conformal (AI,Ti)N films were produced at 450 K in the presence of NH3 and at 550 K without NH3. The role of O2 in Ir film growth was studied with the newly designed equipment. O2 significantly decreases the decomposition temperature of (MeCp)Ir(COD) below 425 K by preventing a carbonaceous build-up on the iridium film. By decreasing the oxygen partial pressure, the island nucleation and coalescence

  5. IONIZATION CHAMBER

    DOEpatents

    Redman, W.C.; Shonka, F.R.

    1958-02-18

    This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

  6. Semiconductor Laser Diode Arrays by MOCVD (Metalorganic Chemical Vapor Deposition)

    DTIC Science & Technology

    1987-09-01

    Roberts. N. J1. Mason. and M. Robinson, J. Cryst. Growth 68, 422 (1984). ’M. R. Leys. C. van Opdorp. M. P. A. .’iegers, and H. J. Talen -van der Mheen...geometry effects is and superlattices has been dominated obtained by including one measured by the MOCVD growth technology . data point in the analysis...Dapkus, Gallium : Arsenide Technology , D.K. Ferry, Ed., tices i Howard W. Sams and Co., Indianapolis, hetero- 1985, p. 79. s is nec- G . 4. G. Costrini and

  7. Real-time physico-neural solutions for MOCVD

    SciTech Connect

    Kelkar, A.S.; Mahajan, R.L.; Sani, R.L.

    1995-12-31

    This paper presents an integrated physical neural network approach for the modeling and optimization of a vertical MOCVD reactor. A first-principles physical model for the reactor was solved numerically using the Fluid Dynamics Analysis Package (FIDAP). This transient model included property variation and thermodiffusion effects. Artificial Neural Network (ANN) models were then trained to predict the growth rate profiles within the reactor. The data used to train the network was obtained from FIDAP simulations for combinations of process parameters determined by statistical Design of Experiments (DOE) methodology. It is shown that the trained ANN predicts the behavior of the reactor accurately. Optimum process conditions to obtain a uniform thickness of the deposited film were determined and tested using the ANN model. The results demonstrate the power and robustness of ANNs for obtaining fast on-line responses to changing input conditions. This capability of ANNs is particularly important for implementing run-to-run and on-line control of the MOCVD process.

  8. MOCVD growth of vertically aligned InGaN nanowires

    NASA Astrophysics Data System (ADS)

    Kuo, H. C.; Su Oh, Tae; Ku, P.-C.

    2013-05-01

    In this work, we report the growth of vertically aligned bulk InGaN nanowires (NWs) on r-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). Through the optimization process of growth conditions, such as growth temperature and pressure, we obtained high density InGaN NWs consisting of one (0001) polar- and two equivalent {1101} semi-polar planes. We have shown the highest InGaN NWs wire density of 8×108 cm-2,with an average diameter of 300 nm and a length of 2 μm. From results of photoluminescence (PL) at 30 K and 300 K, we observed the intense and broad emission peak from InGaN NWs at around 595 nm, and confirmed that the luminescence could be tuned from 580 nm to 660 nm by controlling the indium flow (TMIn) rate. Our results indicate that MOCVD-grown InGaN NWs can be effective absorbers of the blue-green range of solar spectrum and may be one of the good candidates for high efficiency photovoltaic devices targeting at blue-green photons.

  9. Suppression of Mg propagation into subsequent layers grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Agarwal, Anchal; Tahhan, Maher; Mates, Tom; Keller, Stacia; Mishra, Umesh

    2017-01-01

    Low temperature (LT) flow modulation epitaxy (FME) or "pulsed" growth was successfully used to prevent magnesium from Metalorganic Chemical Vapor Deposition (MOCVD) grown p-GaN:Mg layers riding into subsequently deposited n-type layers. Mg concentration in the subsequent layers was lowered from ˜1 × 1018 cm-3 for a medium temperature growth at 950 °C to ˜1 × 1016 cm-3 for a low temperature growth at 700 °C via FME. The slope of the Mg concentration drop in the 700 °C FME sample was 20 nm/dec—the lowest ever demonstrated by MOCVD. For growth on Mg implanted GaN layers, the drop for a medium temperature regrowth at 950 °C was ˜10 nm/dec compared to >120 nm/dec for a high temperature regrowth at 1150 °C. This drop-rate obtained at 950 °C or lower was maintained even when the growth temperature in the following layers was raised to 1150 °C. A controlled silicon doping series using LT FME was also demonstrated with the lowest and highest achieved doping levels being 5 × 1016 cm-3 and 6 × 1019 cm-3, respectively.

  10. Electro-optic materials by solid source MOCVD

    SciTech Connect

    Hiskes, R.; Dicarolis, S.A.; Fouquet, J.; Lu, Z.; Feigelson, R.S.; Route, R.K.; Leplingard, F.; Foster, C.M.

    1993-12-01

    The solid source MOCVD technique, employing a single powder vaporization source composed of mixed beta-diketonate metalorganic compounds, has been used to grow thin films of a variety of electro-optic materials, including lithium niobate, strontium barium niobate, and potassium niobate. Preliminary results for potassium niobate films indicate that a volatile potassium organometallic source can be synthesized useful for growing potassium niobate by MOCVD. High single phase (001) oriented strontium barium niobate films have been deposited which exhibit waveguiding behavior. The most extensive work has been done on lithium niobate deposited epitaxially on a variety of substrates. Oriented z-axis (001) films have been grown on c-axis sapphire with and without a (111) oriented platinum base electrode and on a bulk grown lithium niobate substrate. Films grown directly on c-axis sapphire at 700 C exhibit x-ray rocking curve linewidths as low as .044 degrees, nearly perfect in-plane orientation as determined by x-ray phi scans, and peak-to-peak surface roughness less than 40 {Angstrom}. Optical waveguiding has been demonstrated by single prism coupling technique on similar films 1175--2000 {Angstrom} thick grown at 500 C, with optical losses of approximately 2 db/cm at 632.8 nm measured over 3.5 cm long films. Polarization vs. electric field measurements on 1100 {Angstrom} thick films grown on platinum show a hysteresis loop indicating ferroelectric behavior.

  11. Comparison of AlGaAs Oxidation in MBE and MOCVD Grown Samples

    DTIC Science & Technology

    2002-01-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012613 TITLE: Comparison of AlGaAs Oxidation in MBE and MOCVD Grown...Research Society H6.11 Comparison of AIGaAs Oxidation in MBE and MOCVD Grown Samples* Y. Chen, A. Roshko, K.A. Bertness, National Institute of Standards and...Simultaneous wet-thermal oxidation of MBE and MOCVD grown AlxGal_xAs layers (x = 0.1 to 1.0) showed that the epitaxial growth method does not influence

  12. MOCVD manifold switching effects on growth and characterization

    NASA Technical Reports Server (NTRS)

    Clark, Ivan O.; Fripp, Archibald L.; Jesser, William A.

    1991-01-01

    A combined modeling and experimental approach is used to quantify the effects of various manifold components on the switching speed in metalorganic chemical vapor deposition (MOCVD). In particular, two alternative vent-run high-speed switching manifold designs suitable for either continuous or interrupted growth have been investigated. Both designs are incorporated in a common manifold, instrumented with a mass spectrometer. The experiments have been performed using nitrogen as the transport gas and argon as the simulated source gas. The advantages and limitations of two designs are discussed. It is found that while constant flow manifold switching systems may have fluid dynamic advantages, care must be taken to minimize sections of the supply manifold with low flow rates if rapid changes in alloy composition are required.

  13. Optimization of GaN thin films via MOCVD

    NASA Technical Reports Server (NTRS)

    Dickens, Corey; Wilson, Sylvia L.

    1995-01-01

    A unique characteristic of every semiconductor is the amount of energy required to break an electron bond in the lowest band of allowed states, the valence band. The energy necessary to set an electron free and allow it to conduct in the material is termed the energy gap (Eg). Semiconductors with wide bandgap energies have been shown to possess properties for high power, high temperature, radiation resistance damage, and short wavelength optoelectronic applications. Gallium nitride, which has a wide gap of 3.39 eV, is a material that has demonstrated these characteristics. Various growth conditions are being investigated for quality gallium nitride heteroepitaxy growth via the technique of low pressure metal organic chemical vapor deposition (MOCVD) that can be used for device development.

  14. MOCVD growth of AlGaN UV LEDs

    SciTech Connect

    Han, J.; Crawford, M.H.

    1998-09-01

    Issues related to the MOCVD growth of AlGaN, specifically the gas-phase parasitic reactions among TMG, TMA, and NH{sub 3}, are studied using an in-situ optical reflectometer. It is observed that the presence of the well-known gas phase adduct (TMA: NH{sub 3}) could seriously hinder the incorporation behavior of TMGa. Relatively low reactor pressures (30--50 Torr) are employed to grow an AlGaN/GaN SCH QW p-n diode structure. The UV emission at 360 nm (FWHM {approximately} 10 nm) represents the first report of LED operation from an indium-free GaN QW diode.

  15. Optimization of GaN thin films via MOCVD

    NASA Technical Reports Server (NTRS)

    Dickens, Corey; Wilson, Sylvia L.

    1995-01-01

    A unique characteristic of every semiconductor is the amount of energy required to break an electron bond in the lowest band of allowed states, the valence band. The energy necessary to set an electron free and allow it to conduct in the material is termed the energy gap (Eg). Semiconductors with wide bandgap energies have been shown to possess properties for high power, high temperature, radiation resistance damage, and short wavelength optoelectronic applications. Gallium nitride, which has a wide gap of 3.39 eV, is a material that has demonstrated these characteristics. Various growth conditions are being investigated for quality gallium nitride heteroepitaxy growth via the technique of low pressure metal organic chemical vapor deposition (MOCVD) that can be used for device development.

  16. AlGaInN quaternary alloys by MOCVD

    SciTech Connect

    McIntosh, F.G.; Piner, E.; Boutros, K.; Roberts, J.C.; He, Y.; El-Masry, N.; Bedair, S.M.; Moussa, M.

    1996-11-01

    AlGaInN quaternary alloy based devices can cover the emission wavelength from deep UV to red. This quaternary alloy also offers lattice matched heterostructures for both optical and microwave devices. The authors report on the MOCVD growth of Al{sub x}Ga{sub 1{minus}x{minus}y}In{sub y}N (0 < x < 0.12), (0 < y < 0.15) at 750 C on sapphire substrates, using TMG, EDMIn, TMAl and NH{sub 3} precursors. Chemical composition, lattice constants and bandgaps of the grown films were determined by EDS, X-ray diffraction and room temperature PL. Data indicates that the lattice constants can also be deduced using Vegard`s law, indicating a solid solution of this alloy. PL showed band edge emission, however emission from deep levels was also observed. Optimized growth conditions and heterostructures using this quaternary alloy will be presented.

  17. InGaAs/InP PIN photodetector arrays made by MOCVD based zinc diffusion processes

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad; Feng, J. Y.; Berkovich, Andrew; Abshire, Pamela; Barrows, Geoffrey; Choa, Fow-Sen

    2016-05-01

    InGaAs based long-wavelength near infrared detector arrays are very important for high dynamic range imaging operations seamlessly from daylight environments to dark environments. These detector devices are usually made by open-hole diffusion technique which has the advantage of lower leakage current and higher reliability. The diffusion process is usually done in a sealed quartz ampoule with dopant compounds like ZnP2, ZnAs3, CdP2 etc. side by side with semiconductor samples. The ampoule needs to be prepared and sealing process needs to be done in very clean environment and each time can have variations. In this work we demonstrated using MOCVD growth chamber to perform the diffusion process. The advantages of such a process are that the tool is constantly kept in ultra clean environment and can reproducibly provide clean processes without introducing unexpected defects. We can independently control the temperature and flow rate of the dopant - they are not linked as in the ampoule diffusion case. The process can be done on full wafers with good uniformity through substrate rotation, which is good for large detector array fabrications. We have fabricated different types of InGaAs/InP detector arrays using dimethyl zinc as the dopant source and PH3 or AsH3 for surface protection. Pre-studies of Zn-diffusion profiles in InGaAs and InP at different temperatures, flow rates, diffusion times and followed annealing times were conducted to obtain good control of the process. Grown samples were measured by C-V profilometer to evaluate the diffusion depth and doping concentration. The dependence of the diffusion profile with temperature, dopant partial pressures, and annealing temperature and time and some of the fabricated device characteristics are reported.

  18. Chamber transport

    SciTech Connect

    OLSON,CRAIG L.

    2000-05-17

    Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system.

  19. Thermogravimetric evaluation of the suitability of precursors for MOCVD

    NASA Astrophysics Data System (ADS)

    Kunte, G. V.; Shivashankar, S. A.; Umarji, A. M.

    2008-02-01

    A method based on the Langmuir equation for the estimation of vapour pressure and enthalpy of sublimation of subliming compounds is described. The variable temperature thermogravimetric/differential thermogravimetric (TG/DTG) curve of benzoic acid is used to arrive at the instrument parameters. Employing these parameters, the vapour pressure-temperature curves are derived for salicylic acid and camphor from their TG/DTG curves. The values match well with vapour pressure data in the literature, obtained by effusion methods. By employing the Clausius-Clapeyron equation, the enthalpy of sublimation could be calculated. Extending the method further, two precursors for metal-organic chemical vapour deposition (MOCVD) of titanium oxide bis-isopropyl bis tert-butyl 2-oxobutanoato titanium, Ti(OiPr)2(tbob)2, and bis-oxo-bis-tertbutyl 2-oxobutanoato titanium, [TiO(tbob)2]2, have been evaluated. The complex Ti(OiPr)2(tbob)2 is found to be a more suitable precursor. This approach can be helpful in quickly screening for the suitability of a compound as a CVD precursor.

  20. Growth of InGaN HBTs by MOCVD

    NASA Astrophysics Data System (ADS)

    Chung, Theodore; Limb, Jae; Ryou, Jae-Hyun; Lee, Wonseok; Li, Peng; Yoo, Dongwon; Zhang, Xue-Bing; Shen, Shyh-Chiang; Dupuis, Russell D.; Keogh, David; Asbeck, Peter; Chukung, Ben; Feng, Milton; Zakharov, Dimitri; Lilienthal-Weber, Zusanne

    2006-04-01

    The design and growth of GaN/InGaN heterojunction bipolar transistors (HBTs) by metalorganic chemical vapor deposition (MOCVD) are studied. Atomic-force microscopy (AFM) images of p+InGaN base layers (˜100 nm) deposited under various growth conditions indicate that the optimal growth temperature is limited to the range between 810 and 830°C due to a trade-off between surface roughness and indium incorporation. At these temperatures, the growth pressure must be kept above 300 Torr in order to keep surface pit density under control. An InGaN graded-composition emitter is adopted in order to reduce the number of V-shaped defects, which appear at the interface between GaN emitter and InGaN base and render an abrupt emitter-base heterojunction nearly impossible. However, the device performance is severely limited by the high p-type base contact resistance due to surface etching damage, which resulted from the emitter mesa etch.

  1. Influence of Natural Convection and Thermal Radiation Multi-Component Transport in MOCVD Reactors

    NASA Technical Reports Server (NTRS)

    Lowry, S.; Krishnan, A.; Clark, I.

    1999-01-01

    The influence of Grashof and Reynolds number in Metal Organic Chemical Vapor (MOCVD) reactors is being investigated under a combined empirical/numerical study. As part of that research, the deposition of Indium Phosphide in an MOCVD reactor is modeled using the computational code CFD-ACE. The model includes the effects of convection, conduction, and radiation as well as multi-component diffusion and multi-step surface/gas phase chemistry. The results of the prediction are compared with experimental data for a commercial reactor and analyzed with respect to the model accuracy.

  2. High Throughput of Reel-to-reel MOCVD-YBCO on Different CSD-and MOCVD-buffered Cube Textured Ni-substrates

    NASA Astrophysics Data System (ADS)

    Muydinov, Ruslan; Stadel, Oliver; Falter, Martina; BŠcker, Michael

    Cheap chemical approaches: CSD/MOD and MOCVD were used and demonstrated to be feasible in 2G-wire production. New reel-to-reel MOCVD pilot system with higher throughput was examined, tuned and used in all YBCO depositions as well as for MgO, LMO, YSZ and CeO2 buffer layers fabrication. YBCO deposition process was found to be stable either at 10 m/h on 50 m long tapes or at 20 m/h on 100 m long tapes. All-layers-by-MOCVD approach allowed to get critical current up to Ic max > 90A/cm-width. On a single CSD-LZO (lanthanum zirconate) buffered Ni-alloy tapes 400 nm thick YBCO films with critical current density up to jc max = 1.5 MA/cm2 were obtained. On the basis of single CSD-LZO-buffered tapes, some multiple buffer sandwiches were created and compared in the same YBCO deposition. The best result was reached on CVD-CeO2/1×CSD-LZO/Ni5W buffer oxide system and showed for 650 nm thick YBCO rather stable over 2.5 m length Ic = 80-90 A.

  3. Growth and characterization of CdS buffer layers by CBD and MOCVD

    SciTech Connect

    Morrone, A.A.; Huang, C.; Li, S.S.

    1999-03-01

    Thin film CdS has been widely used in thin-film photovoltaic devices. The most efficient Cu(In,&hthinsp;Ga)Se{sub 2} (CIGS) solar cells reported to date utilized a thin CdS buffer layer prepared by a reactive solution growth technique known as chemical bath deposition (CBD). Considerable effort has been directed to better understand the role and find a replacement for the CBD CdS process in CIGS-based solar cells. We reported a low temperature ({approximately}150&hthinsp;{degree}C) Metalorganic Chemical Vapor Deposition (MOCVD) CdS thin film buffer layer process for CIGS absorbers. Many prior studies have reported that CBD CdS contains a mixture of crystal structures. Recent investigations of CBD CdS thin films by ellipsometry suggested a multilayer structure. In this study we compare CdS thin films prepared by CBD and MOCVD and the effects of annealing. TED and XRD are used to characterize the crystal structure, the film microstructure is studied by HRTEM, and the optical properties are studied by Raman and spectrophotometry. All of these characterization techniques reveal superior crystalline film quality for CdS films grown by MOCVD compared to those grown by CBD. Dual Beam Optical Modulation (DBOM) studies showed that the MOCVD and CBD CdS buffer layer processes have nearly the same effect on CIGS absorbers when combined with a cadmium partial electrolyte aqueous dip. {copyright} {ital 1999 American Institute of Physics.}

  4. Method for Improving Mg Doping During Group-III Nitride MOCVD

    DOEpatents

    Creighton, J. Randall; Wang, George T.

    2008-11-11

    A method for improving Mg doping of Group III-N materials grown by MOCVD preventing condensation in the gas phase or on reactor surfaces of adducts of magnesocene and ammonia by suitably heating reactor surfaces between the location of mixing of the magnesocene and ammonia reactants and the Group III-nitride surface whereon growth is to occur.

  5. Portable Hyperbaric Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, James P. (Inventor); DeLaFuente, Horacio (Inventor)

    2001-01-01

    A portable, collapsible hyperbaric chamber was developed. A toroidal inflatable skeleton provides initial structural support for the chamber, allowing the attendant and/or patient to enter the chamber. Oval hatches mate against bulkhead rings, and the hyperbaric chamber is pressurized. The hatches seal against an o-ring, and the internal pressure of the chamber provides the required pressure against the hatch to maintain an airtight seal. In the preferred embodiment, the hyperbaric chamber has an airlock to allow the attendant to enter and exit the patient chamber during treatment. Visual communication is provided through portholes in the patient and/or airlock chamber. Life monitoring and support systems are in communication with the interior of the hyperbaric chamber and/or airlock chamber through conduits and/or sealed feed-through connectors into the hyperbaric chamber.

  6. Portable Hyperbaric Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, James P. (Inventor); DeLaFuente, Horacio (Inventor)

    2001-01-01

    A portable, collapsible hyperbaric chamber was developed. A toroidal inflatable skeleton provides initial structural support for the chamber, allowing the attendant and/or patient to enter the chamber. Oval hatches mate against bulkhead rings, and the hyperbaric chamber is pressurized. The hatches seal against an o-ring, and the internal pressure of the chamber provides the required pressure against the hatch to maintain an airtight seal. In the preferred embodiment, the hyperbaric chamber has an airlock to allow the attendant to enter and exit the patient chamber during treatment. Visual communication is provided through portholes in the patient and/or airlock chamber. Life monitoring and support systems are in communication with the interior of the hyperbaric chamber and/or airlock chamber through conduits and/or sealed feed-through connectors into the hyperbaric chamber.

  7. A novel approach to grow ZnO nanowires and nanoholes by combined colloidal lithography and MOCVD deposition.

    PubMed

    Fragalà, Maria Elena; Satriano, Cristina; Malandrino, Graziella

    2009-02-21

    A hybrid approach of colloidal lithography and metalorganic chemical vapour deposition (MOCVD) has been used to fabricate ZnO nanowire bundles and nanoholes by using a silver metalorganic precursor as the growth catalyst.

  8. Improved Bakeout Chambers Within Vacuum Chambers

    NASA Technical Reports Server (NTRS)

    Johnson, Kenneth R.; Taylor, Daniel M.; Lane, Robert W.; Cortez, Maximo G.; Anderson, Mark R.

    1995-01-01

    Improved bakeout chamber incorporates hardware features that, in conjunction with improved bakeout procedure, reduce spurious contamination and increase accuracy of contamination measurements. When operated according to revised bakeout procedure, they yield measurements of contamination on vacuum-bake test articles more accurate than available previously, and potential for post-bake recontamination of vacuum-baked articles reduced. These chambers improved versions of one described in "Bakeout Chamber Within Vacuum Chamber" (NPO-18959). By enclosing test article in enclave and keeping walls of enclave hotter than test article during bakeout, one prevents condensation of contaminants on inner walls of enclave.

  9. Hardware Modifications to the US Army Research Laboratory’s Metalorganic Chemical Vapor Deposition (MOCVD) System for Optimization of Complex Oxide Thin Film Fabrication

    DTIC Science & Technology

    2015-04-01

    Substrate 17 4.2.3 Atomic Force Microscopy (AFM) AFM micrographs for the as- deposited STO thin film after hardware modifications were taken... layer -by- layer MOCVD of complex metal oxides and in situ process monitoring. Chemical Vapor Deposition . 2001;7:7–18. 39. Jones AC. MOCVD of...modeling of pulsed MOCVD with ultrasonic atomization of liquid precursor. Chemical Vapor Deposition . 2001;7:85–90. 51. Xie HY, Versteeg VA, Raj R

  10. The crystal morphology effect of Iridium tris-acetylacetonate on MOCVD iridium coatings

    NASA Astrophysics Data System (ADS)

    Shi, Jing; Hao, Yupeng; Yu, Xiaodong; Tan, Chengwen

    2017-07-01

    Iridium tris-acetylacetonate is the most commonly used precursor for the metal organic chemical vapour deposition (MOCVD) of iridium coating. In this paper, the crystal morphology effect of iridium tris-acetylacetonate on iridium coatings prepared by MOCVD was studied. Two kinds of Ir(acac)3 crystalline powder were prepared. A precursor sublimation experiment in a fixed bed reactor and an iridium deposition experiment in a cold-wall atmospheric CVD reactor were designed. It is found that the volatility of the hexagonal columnar crystals is better than that of the tetragonal flake crystals under the experimental conditions. It’s due to the hexagonal columnar crystals exposed more crystal faces than the tetragonal flake crystals, increasing its contact area with the transport gas. An adequate supply of iridium tris-acetylacetonate during the pre-deposition period contributed to obtain an iridium coating with a smooth and uniform continuity surface.

  11. Photoreflectance for in-situ characterization of MOCVD growth of semiconductors under micro-gravity conditions

    NASA Technical Reports Server (NTRS)

    Pollak, Fred H.

    1990-01-01

    A contactless electromodulation technique of photoreflectance (PR) was developed for in-situ monitoring of metal-organic chemical vapor deposition (MOCVD) semiconductor growth for micro-gravity applications. PR can be employed in a real MOCVD reactor including rotating substrate (approximately 500 rev/min) in flowing gases and through a diffuser plate. Measurements on GaAs and Ga(0.82)Al(0.18)As were made up to 690 C. The direct band gaps of In(x)Ga(1-x)As (x = 0.07 and 0.16) were evaluated up to 600 C. In order to address the question of real time measurement, the spectra of the direct gap of GaAs at 650 C was obtained in 30 seconds and 15 seconds seems feasible.

  12. A novel MOCVD reactor for growth of high-quality GaN-related LED layers

    NASA Astrophysics Data System (ADS)

    Hu, Shaolin; Liu, Sheng; Zhang, Zhi; Yan, Han; Gan, Zhiyin; Fang, Haisheng

    2015-04-01

    Gallium nitride (GaN), a direct bandgap semiconductor widely used in bright light-emitting diodes (LEDs), is mostly grown by metal-organic chemical vapor deposition (MOCVD) method. A good reactor design is critical for the production of high-quality GaN thin films. In this paper, we presented a novel buffered distributed spray (BDS) MOCVD reactor with vertical gas sprayers and horizontal gas inlets. Experiments based on a 36×2″ BDS reactor were conducted to examine influence of the process parameters, such as the operating pressure and the gas flow rate, on the growth efficiency and on the layer thickness uniformity. Transmission electron microscopy (TEM) and photoluminescence (PL) are further conducted to evaluate quality of the epitaxial layers and to check performance of the reactor. Results show that the proposed novel reactor is of high performance in growing high-quality thin films, including InGaN/GaN multiquantum wells (MQWs) structures.

  13. Copper iodide synthesized by iodization of Cu-films and deposited using MOCVD

    NASA Astrophysics Data System (ADS)

    Gottschalch, Volker; Blaurock, Steffen; Benndorf, Gabriele; Lenzner, Jörg; Grundmann, Marius; Krautscheid, Harald

    2017-08-01

    We report the thin film deposition of copper iodide with zincblende type structure (γ-CuI) via metal-organic chemical vapor deposition (MOCVD). Single crystals and thin films of Cu and γ-CuI could be formed on various substrates from cyclopentadienylcopper triethylphosphine (CpCuPEt3) and ethyliodide (C2H5I) as precursors for copper and iodine, respectively. Additionally, the chemical reaction behavior of thermally evaporated and MOCVD deposited elemental copper films with C2H5I is examined. SiO2 glass and various single crystalline oxides and semiconductors were used as substrates. For all cases X-ray diffraction measurements revealed polycrystalline γ-CuI with zincblende type structure; other CuI phases could not be detected. Photoluminescence measurements show a broadened peak at 420 nm due to donor-acceptor pair recombination. Intense peaks at shorter wavelengths are attributed to excitonic emissions.

  14. In-situ estimation of MOCVD growth rate via a modified Kalman filter

    SciTech Connect

    Woo, W.W.; Svoronos, S.A.; Sankur, H.O.; Bajaj, J.; Irvine, S.J.C.

    1996-05-01

    In-situ laser reflectance monitoring of metal-organic chemical vapor deposition (MOCVD) is an effective way to monitor growth rate and epitaxial layer thickness of a variety of III-V and II-VI semiconductors. Materials with low optical extinction coefficients, such as ZnTe/GaAs and AlAs/GaAs for a 6,328 {angstrom} HeNe laser, are ideal for such an application. An extended Kalman filter modified to include a variable forgetting factor was applied to the MOCVD systems. The filter was able to accurately estimate thickness and growth rate while filtering out process noise and cope with sudden changes in growth rate, reflectance drift, and bias. Due to the forgetting factor, the Kalman filter was successful, even when based on very simple process models.

  15. Multilayer porous structures of HVPE and MOCVD grown GaN for photonic applications

    NASA Astrophysics Data System (ADS)

    Braniste, T.; Ciers, Joachim; Monaico, Ed.; Martin, D.; Carlin, J.-F.; Ursaki, V. V.; Sergentu, V. V.; Tiginyanu, I. M.; Grandjean, N.

    2017-02-01

    In this paper we report on a comparative study of electrochemical processes for the preparation of multilayer porous structures in hydride vapor phase epitaxy (HVPE) and metal organic chemical vapor phase deposition (MOCVD) grown GaN. It was found that in HVPE-grown GaN, multilayer porous structures are obtained due to self-organization processes leading to a fine modulation of doping during the crystal growth. However, these processes are not totally under control. Multilayer porous structures with a controlled design have been produced by optimizing the technological process of electrochemical etching in MOCVD-grown samples, consisting of five pairs of thin layers with alternating-doping profiles. The samples have been characterized by SEM imaging, photoluminescence spectroscopy, and micro-reflectivity measurements, accompanied by transfer matrix analysis and simulations by a method developed for the calculation of optical reflection spectra. We demonstrate the applicability of the produced structures for the design of Bragg reflectors.

  16. Radiation effects on p+n InP junctions grown by MOCVD

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Walters, Robert J.; Panunto, M. J.; Summers, Geoffrey P.

    1994-01-01

    The superior radiation resistance of InP over other solar cell materials such as Si or GaAs has prompted the development of InP cells for space applications. The early research on radiation effects in InP was performed by Yamaguchi and co-workers who showed that, in diffused p-InP junctions, radiation-induced defects were readily annealed both thermally and by injection, which was accompanied by significant cell recovery. More recent research efforts have been made using p-InP grown by metalorganic chemical vapor deposition (MOCVD). While similar deep level transient spectroscopy (DLTS) results were found for radiation induced defects in these cells and in diffused junctions, significant differences existed in the annealing characteristics. After injection annealing at room temperature, Yamaguchi noticed an almost complete recovery of the photovoltaic parameters, while the MOCVD samples showed only minimal annealing. In searching for an explanation of the different annealing behavior of diffused junctions and those grown by MOCVD, several possibilities have been considered. One possibility is the difference in the emitter structure. The diffused junctions have S-doped graded emitters with widths of approximately 0.3 micrometers, while the MOCVD emitters are often doped with Si and have widths of approximately 300A (0.03 micrometers). The difference in the emitter thickness can have important effects, e.g. a larger fraction of the total photocurrent is generated in the n-type material for thicker emitters. Therefore the properties of the n-InP material may explain the difference in the observed overall annealing behavior of the cells.

  17. Final report on LDRD project : outstanding challenges for AlGaInN MOCVD.

    SciTech Connect

    Mitchell, Christine Charlotte; Follstaedt, David Martin; Russell, Michael J.; Cross, Karen Charlene; Wang, George T.; Creighton, James Randall; Allerman, Andrew Alan; Koleske, Daniel David; Lee, Stephen Roger; Coltrin, Michael Elliott

    2005-03-01

    The AlGaInN material system is used for virtually all advanced solid state lighting and short wavelength optoelectronic devices. Although metal-organic chemical vapor deposition (MOCVD) has proven to be the workhorse deposition technique, several outstanding scientific and technical challenges remain, which hinder progress and keep RD&A costs high. The three most significant MOCVD challenges are: (1) Accurate temperature measurement; (2) Reliable and reproducible p-doping (Mg); and (3) Low dislocation density GaN material. To address challenge (1) we designed and tested (on reactor mockup) a multiwafer, dual wavelength, emissivity-correcting pyrometer (ECP) for AlGaInN MOCVD. This system simultaneously measures the reflectance (at 405 and 550 nm) and emissivity-corrected temperature for each individual wafer, with the platen signal entirely rejected. To address challenge (2) we measured the MgCp{sub 2} + NH{sub 3} adduct condensation phase diagram from 65-115 C, at typical MOCVD concentrations. Results indicate that it requires temperatures of 80-100 C in order to prevent MgCp{sub 2} + NH{sub 3} adduct condensation. Modification and testing of our research reactor will not be complete until FY2005. A new commercial Veeco reactor was installed in early FY2004, and after qualification growth experiments were conducted to improve the GaN quality using a delayed recovery technique, which addresses challenge (3). Using a delayed recovery technique, the dislocation densities determined from x-ray diffraction were reduced from 2 x 10{sup 9} cm{sup -2} to 4 x 10{sup 8} cm{sup -2}. We have also developed a model to simulate reflectance waveforms for GaN growth on sapphire.

  18. Characteristics of CoxTi1-xO2 thin films deposited by MOCVD

    SciTech Connect

    McClure, A.; Kayani, A.; Idzerda, Y.U.; Arenholz, E.; Cruz, E.

    2008-05-09

    This paper deals with the growth and characterization of ferromagnetic cobalt doped TiO{sub 2} thin films deposited by liquid precursor metal organic chemical vapor deposition (MOCVD) using a new combination of the source materials Co(TMHD){sub 3}, tetrahydrofuran (THF), and titanium isopropoxide (TIP). An array of experiments reveals the intrinsic ferromagnetic nature of the grown films, and suggests that the magnetism is not generated by oxygen vacancies.

  19. CONTINUOUS ROTATION SCATTERING CHAMBER

    DOEpatents

    Verba, J.W.; Hawrylak, R.A.

    1963-08-01

    An evacuated scattering chamber for use in observing nuclear reaction products produced therein over a wide range of scattering angles from an incoming horizontal beam that bombards a target in the chamber is described. A helically moving member that couples the chamber to a detector permits a rapid and broad change of observation angles without breaching the vacuum in the chamber. Also, small inlet and outlet openings are provided whose size remains substantially constant. (auth)

  20. Progress in MOCVD growth of HgCdTe epilayers for HOT infrared detectors

    NASA Astrophysics Data System (ADS)

    Kebłowski, A.; Gawron, W.; Martyniuk, P.; Stepień, D.; Kolwas, K.; Piotrowski, J.; Madejczyk, P.; Kopytko, M.; Piotrowski, A.; Rogalski, A.

    2016-05-01

    In this paper we present progress in MOCVD growth of (100) HgCdTe epilayers achieved recently at the Institute of Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor doping and without post grown annealing. Particular progress has been achieved in the growth of (100) HgCdTe epilayers for long wavelength infrared photoconductors operated in HOT conditions. The (100) HgCdTe photoconductor optimized for 13-μm attain detectivity equal to 6.5x109 Jones and therefore outperform its (111) counterpart. The paper also presents technological progress in fabrication of MOCVD-grown (111) HgCdTe barrier detectors. The barrier device performance is comparable with state-of-the-art of HgCdTe photodiodes. The detectivity of HgCdTe detectors is close to the value marked HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07".

  1. Fast growth rate of epitaxial β-Ga2O3 by close coupled showerhead MOCVD

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Hertog, Brian; Osinsky, Andrei; Mukhopadhyay, Partha; Toporkov, Mykyta; Schoenfeld, Winston V.

    2017-10-01

    We report on the growth of epitaxial β-Ga2O3 thin films on c-plane sapphire substrates using a close coupled showerhead MOCVD reactor. Ga(DPM)3 (DPM = dipivaloylmethanate), triethylgallium (TEGa) and trimethylgallium (TMGa) metal organic (MO) precursors were used as Ga sources and molecular oxygen was used for oxidation. Films grown from each of the Ga sources had high growth rates, with up to 10 μm/hr achieved using a TMGa precursor at a substrate temperature of 900 °C. As confirmed by X-ray diffraction, the films grown from each of the Ga sources were the monoclinic (2 bar 0 1) oriented β-Ga2O3 phase. The optical bandgap of the films was also estimated to be ∼4.9 eV. The fast growth rate of β-Ga2O3 thin films obtained using various Ga-precursors has been achieved due to the close couple showerhead design of the MOCVD reactor as well as the separate injection of oxygen and MO precursors, preventing the premature oxidation of the MO sources. These results suggest a pathway to overcoming the long-standing challenge of realizing fast growth rates for Ga2O3 using the MOCVD method.

  2. Material utilisation when depositing CdTe layers by inline AP-MOCVD

    NASA Astrophysics Data System (ADS)

    Barrioz, V.; Kartopu, G.; Irvine, S. J. C.; Monir, S.; Yang, X.

    2012-09-01

    A study was undertaken to assess the efficiency of precursors' usage during deposition of cadmium telluride (CdTe) layers via atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) for thin film photovoltaic solar cells. Precursors were released from a showerhead assembly normal to the glass substrate 0.7 mm thick (5×7.5 cm2) being deposited which was kept stationary or moved under the showerhead assembly, with speed of upto 2.25 cm/min. In order to estimate the effective precursor utilisation, the weight deposit (layer) was compared against the theoretical values calculated for ideal molar supply. The layer thickness, composition, morphology, and crystallinity were also measured using profilometry, energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. It is shown that over 40% material utilisation can be achieved depending on the deposition parameters of substrate temperature and speed, partial pressure of precursors and total gas flow. The activation energy derived from an Arrhenius plot of deposition rate equals 49 kJ mol-1 and is consistent with previous reports of MOCVD CdTe using a horizontal reactor. This confirms that, despite the very different reactor geometry, the alkyl radical homolysis and reaction mechanism applies in the case of the inline injector geometry in the work presented here. These results demonstrate an alternative path to high throughput processing of CdTe thin film solar cells by inline AP-MOCVD.

  3. Recent progress in MOCVD growth for thermoelectrically cooled HgCdTe medium wavelength infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Gawron, W.; Martyniuk, P.; Kębłowski, A.; Kolwas, K.; Stępień, D.; Piotrowski, J.; Madejczyk, P.; Pędzińska, M.; Rogalski, A.

    2016-04-01

    The authors report on advanced metalorganic chemical vapour deposition (MOCVD) of Hg1-xCdxTe (HgCdTe) structures for high operating temperature, medium wavelength infrared (MWIR) detector application. MOCVD technology with wide range of composition and donor/acceptor doping and without post grown annealing was proved to be an excellent tool for HgCdTe heterostructure epitaxial growth used for uncooled photodetector design. The interdiffused multilayer process (IMP) technique was applied for the HgCdTe deposition. HgCdTe epilayers were grown at 350 °C with Hg source kept at 210 °C. The II/VI mole ratio was assumed in the range from 1.5 to 3 during CdTe/HgTe cycles of the IMP process. The MWIR detectors grown by MOCVD exhibit detectivity ∼7.3 × 1011 Jones at λPEAK = 3.5 μm and T = 230 K being determined by background limited photodetector (BLIP) condition.

  4. MOCVD for solar cells, a transition towards a chamberless inline process

    NASA Astrophysics Data System (ADS)

    Barrioz, V.; Monir, S.; Kartopu, G.; Lamb, D. A.; Brooks, W.; Siderfin, P.; Jones, S.; Clayton, A. J.; Irvine, S. J. C.

    2015-03-01

    MOCVD has been associated with batch processing of III-V opto-electronic devices for decades, with epitaxial structures deposited on up to 200 mm diameter wafers. Recent development in thin film PV has seen the gap in conversion efficiencies closing in on that of the commonly found multicrystalline Si wafer based PV. To further improve the conversion efficiency of thin film PV towards the theoretical limits of single junction solar cells requires a technique such as MOCVD with scalability potential. Preliminary results on the development of a chamberless inline process are reported for up to 15 cm wide float glass, progressively coating each layer in the CdTe solar cell as the heated substrate passes under each coating head in turn and entirely at atmospheric pressure. Emphasis is made on ensuring that the chamberless coating heads can be operated safely using a combination of nitrogen curtain flows and a balanced exhaust pressure system. Results are also presented on the exclusion of oxygen and moisture from the coating area, achieved using the same gas flow isolation process. This paper also reviews the achievements made to-date in the transfer of the high efficiency batch MOCVD produced CdTe solar cell to the chamberless inline process demonstrating device quality thin films deposition.

  5. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  6. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1998-05-05

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  7. Electron and Composite Fermion Transport in MOCVD Grown GaAs/AlGaAs Heterostructures

    NASA Astrophysics Data System (ADS)

    Zudov, M. A.; Du, R. R.; Simmons, J. A.; Chui, H. C.

    1996-03-01

    Previously, high quality fractional quantum Hall effect(FQHE) data was accessible only from MBE-grown heterostructures. Sandia National Labs has recently grown high purity MOCVD GaAs/AlGaAs heterostructure with 2DEG mobility of 2.0x10^6 cm^2/Vs[1]. Material parameters such as impurity potential profile, defects and interface quality are expected to be modified for MOCVD. While these are believed to affect predominantly the carrier scattering in 2DEG, their effects on quantum transport properties (in particular the experimental effective mass and spin g-factor of composite fermions) are also worth examination. We report on temperature-dependent Shubnikov -de Haas(SdH) oscillations near zero magnetic field, SdH near Landau level filling factor ν = 1/2, 3/2, and angular dependent magnetoresistance mesurements on the FQHE states around ν = 3/2 in high-density (up to 3.2x10^11 cm-2) MOCVD samples. Measurements were performed in a 20mK/20T ^3He-^4He mixture dilution refrigerator. Our results around ν = 3/2 conform to the same composite fermion level scheme obtained earlier for low-density MBE samples[2]. [1] H. C. Chui, B. E. Hammons, N. E. Harff, J. A. Simmons and M. E. Sherwin, to appear in Appl. Phys. Lett. [2] R. R. Du, A. S. Yeh, H. L. Stormer, D. C. Tsui, L. N. Pfeifer, K. W. West, Phys. Rev. Lett. 75, 3926(1995)

  8. Investigation of GaP/Si Heteroepitaxy on MOCVD Prepared Si(100) Surfaces

    SciTech Connect

    Warren, Emily L.; Kibbler, Alan E.; France, Ryan M.; Norman, Andrew G.; Olson, Jerry M.; McMahon, William E.

    2015-06-14

    Antiphase-domain (APD) free growth of GaP on Si has been achieved on Si surfaces prepared in situ by etching with AsH3. The pre-nucleation AsH3 etching removes O and C contaminants at a relatively low temperature, and creates a single-domain arsenic-terminated Si surface. The As-As dimer rows are all parallel to the step edges, and subsequent GaP growth by MOCVD retains this dimerization orientation. Both LEED and TEM indicate that the resulting epilayer is APD-free, and could thereby serve as a template for III-V/Si multijunction solar cells.

  9. Gas phase adduct reactions in MOCVD growth of GaN

    SciTech Connect

    Thon, A.; Kuech, T.F.

    1996-11-01

    Gas phase reactions between trimethylgallium (TMG) and ammonia were studied at high temperatures, characteristic to MOCVD of GaN reactors, by means of in situ mass spectroscopy in a flow tube reactor. It is shown, that a very fast adduct formation followed by elimination of methane occurs. The decomposition of TMG and the adduct-derived compounds are both first order and have similar apparent activation energy. The pre-exponential factor of the adduct decomposition is smaller, and hence is responsible for the higher full decomposition temperature of the adduct relative to that of TMG.

  10. Target chambers for gammashpere

    SciTech Connect

    Carpenter, M.P.; Falout, J.W.; Nardi, B.G.

    1995-08-01

    One of our responsibilities for Gammasphere, was designing and constructing two target chambers and associated beamlines to be used with the spectrometer. The first chamber was used with the early implementation phase of Gammasphere, and consisted of two spun-Al hemispheres welded together giving a wall thickness of 0.063 inches and a diameter of 12 inches.

  11. A soundproof pressure chamber.

    PubMed

    Kitahara, M; Kodama, A; Ozawa, H; Inoue, S

    1994-01-01

    For neurotological research we designed a soundproof pressure chamber in which pressure can be adjusted +/- 1000 mmH2O at the rate of less than 100 mmH2O per second. Noise in the chamber can be maintained under 30-35 dB while pressure is kept at a given level.

  12. Static diffusion cloud chambers

    NASA Technical Reports Server (NTRS)

    Ayers, G.

    1981-01-01

    The chamber geometry and optical arrangement are described. The supersaturation range is given and consists of readings taken at five fixed points: 0.25%, 0.5%, 0.75%, 1.0%, and 1.25%. The detection system is described including light source, cameras, and photocell detectors. The temperature control and the calibration of the chamber are discussed.

  13. High resolution drift chambers

    SciTech Connect

    Va'vra, J.

    1985-07-01

    High precision drift chambers capable of achieving less than or equal to 50 ..mu..m resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs.

  14. The Mobile Chamber

    NASA Technical Reports Server (NTRS)

    Scharfstein, Gregory; Cox, Russell

    2012-01-01

    A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

  15. 45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), VIEW LOOKING EAST. LEAD ENCLOSED PIPING IS DRAIN FROM BOILER CHAMBER No. 1 - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  16. Investigation of Er 2O 3 coating on liquid blanket components synthesized by the MOCVD process

    NASA Astrophysics Data System (ADS)

    Hishinuma, Y.; Tanaka, T.; Tanaka, T.; Nagasaka, T.; Yoshizawa, S.; Tasaki, Y.; Muroga, T.

    2011-10-01

    An electrical insulating coating on the blanket components such as ducts and walls is an attractive concept for reducting the Magneto Hydrodynamics pressure drop. Erbium oxide was shown to be a promising candidate coating because of its high stability in liquid lithium and high electrical resistivity. We have applied the Metal Organic Chemical Vapor Deposition (MOCVD) process to produce Er 2O 3 coating layers on the large areas and/or complicated shape components. Recently, we confirmed that Er 2O 3 coating layers were synthesized on a vanadium alloy and on silicon single crystal plates. In this work, we tried to form Er 2O 3 thin coating layer on the interior surface of the short quartz tube to demonstrate Er 2O 3 coating of components relevant to liquid blankets. The improvement found by the using an organic complex as the erbium source material and the effects of the deposition temperature for the further upgrading the MOCVD process were also evaluated.

  17. In situ stress measurements during MOCVD growth of thick N-polar InGaN

    NASA Astrophysics Data System (ADS)

    Al Balushi, Zakaria Y.; Redwing, Joan M.

    2017-08-01

    The growth of N-polar InGaN films by metalorganic chemical vapor deposition (MOCVD) on N-polar GaN was investigated in order to understand the evolution of growth stress and the dislocation microstructure of relatively thick InGaN films (140 nm) in the absence of hexagonal hillocks and V-pits, which are typically present in III-polar InGaN. During in situ stress measurements of N-polar InGaN, growth initiates under an initial low stress state, which gradually transitions to a constant compressive incremental stress for the remainder of the film thickness. This behavior in the growth stress evolution in N-polar InGaN occurs regardless of the stress state of the GaN base layer (i.e., compression or tension), which was controlled by varying the temperature of the initial low temperature layer in a two-step temperature growth process for N-polar GaN. A blue shift in the PL peak emission of N-polar InGaN was, however, observed with increasing incremental compressive stress in the N-polar GaN base layer. These results provide insight into potential mechanisms of plastic relaxation in high crystal quality thick N-polar InGaN films grown by MOCVD.

  18. Properties and orientation of antiferroelectric lead zirconate thin films grown by MOCVD.

    SciTech Connect

    Chen, N.

    1998-12-21

    Single-phase polycrystalline PbZrO{sub 3} (PZ) thin films, 3000-6000 {angstrom} thick, have been grown by metal-organic chemical vapor deposition (MOCVD) on (111)Pt/Ti/SiO{sub 2}/Si substrates at {approximately}525 C. X-ray diffraction analysis indicated that the PZ films grown on (111)Pt/Ti/SiO{sub 2}/Si (Pt/Ti/Si) showed preferred pseudocubic (110) orientation. In contrast, PZ films grown on 150 {angstrom} thick PbTiO{sub 3} (PT) template layers exhibited a pseudocubic (100) preferred orientation, and PZ films deposited on TiO{sub 2} template layers consisted of randomly oriented grains. The PZ films grown on Pt/Ti/Si with or without templates exhibited dielectric constants of 120-200 and loss tangents of 0.03-0.01. The PZ films with (110) orientation exhibited an electric-field-induced transformation from the antiferroelectric phase to the ferroelectric phase with a polarization of {approx}34 {micro}C/cm{sup 2}, and the energy that was stored during switching was 7.1 J/cm{sup 3}. The field needed to excite the ferroelectric state and that needed to revert to the antiferroelectric state were 350 and 250 kV/cm, respectively. Relationships between the MOCVD processing and the film microstructure and properties are discussed.

  19. Improvements in MOCVD growth of Hg1-xCdxTe heterostructures for uncooled infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Piotrowski, A.; Gawron, W.; Klos, K.; Pawluczyk, J.; Piotrowski, J.; Madejczyk, P.; Rogalski, A.

    2005-09-01

    We report here the recent progress at VIGO/MUT (Military University of Technology) MOCVD Laboratory in the growth of Hg1-xCdxTe multilayer heterostructures for various types of uncooled infrared devices. The detectors are optimized for any wavelength within 1-12 μm spectral range. Hg1-xCdxTe growth with interdiffused multilayer process (IMP) technique has been improved. The total flow of the carrier gas was optimized to improve lateral uniformity of the composition and doping. The parasitic transient stages between the CdTe and HgTe phases were reduced to reasonable minimum. As a result, we were able to grow layers with homogeneous composition and doping, characterized by steep interfaces. The additional benefits were improved morphology, reduced dislocation density, and minimized consumption of precursors. The other issues addressed in this work were growth of heavy As-doped low-x and heavy Idoped high-x materials. Special modification to IMP process has been applied for in-situ control of stoichiometry. To maintain low vacancy concentration, special growth finish procedure has been developed. No post-growth thermal anneal was necessary for device-quality material. The MOCVD grown heterostructures have been successfully used for advanced uncooled infrared photodetectors such as multiple heterojunction photodiodes, multicolor and specially shaped spectral response multiabsorber devices.

  20. Ab initio study of MOCVD synthesis of InN and GaN

    NASA Astrophysics Data System (ADS)

    Walkosz, Weronika; Zapol, Peter; Highland, Matthew J.; Fuoss, Paul H.; Stephenson, Gregory B.

    2011-03-01

    A detailed understanding of MOCVD growth of group III nitrides is important for improved control over their properties and performance in a wide range of applications. Because of the relative instability of InN, chemically active precursors such as NH3 are typically used to provide the high nitrogen activity needed for growth. Our goal is to understand the mechanism and species involved in active nitrogen formation on the growth surface. Here we present results of density functional theory calculations for the decomposition of NH3 on InN and GaN (0001) surfaces through reaction intermediates such as adsorbed NH2 and NH. The calculated equilibrium surface structures along with the reaction barriers for the dissociation pathways of NH3 on these surfaces are described. Kinetic modeling based on the calculated barriers to determine reaction mechanisms and effective nitrogen activities is discussed. The results will be used to elucidate chemical kinetics on GaN and InN (0001) surfaces under MOCVD growth conditions with the aim to optimize synthesis conditions and precursors for effective growth of metastable nitrides. Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

  1. Fabrication of GaN nanotubular material using MOCVD with aluminum oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-02-01

    GaN nanotubular material is fabricated with aluminum oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminum oxide membrane with ordered nano holes is used as template. Gallium nitride is deposited at the inner wall of the nano holes in aluminum oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis condition in MOCVD is obtained successfully for the gallium nitride nanotubular material in this research. The diameter of GaN nanotube fabricated is approximately 200 ~ 250 nm and the wall thickness is about 40 ~ 50 nm. GaN nanotubular material consists of numerous fine GaN particulates with sizes ranging 15 to 30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that grains in GaN nanotubular material have nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in aluminum oxide template.

  2. Epitaxial Growth of BGaAs and BGaInAs by MOCVD: Preprint

    SciTech Connect

    Geisz, J. F.; Friedman, D. J.; Kurtz, S. R.; Olson, J. M.; Kramer, C.; Young, M.; Barber, G.; Swartzlander, A. B.; Reedy, R. C.; Norman, A. G.

    2001-10-01

    Presented at the 2001 NCPV Program Review Meeting: Comparison of use of TMB, TEB, and BF3 to diborane for MOCVD growth of BGaInAs. BGaInAs can potentially be used in strain-free high-efficiency III-V solar cells, but the growth of sufficiently high-quality epitaxial BGaInAs using diborane has proven difficult. We compare the use of alternative boron precursors (trimethylboron [TMB], triethylboron [TEB], and boron trifluoride [BF{sub 3}]) with diborane for the MOCVD growth of these boron-containing III-V alloys. We find that TMB and BF{sub 3} do not result in significant boron incorporation into GaAs. TEB does result in boron incorporation in a manner very similar to diborane. Both diborane and TEB incorporate more efficiently using triethylgallium (TEG) rather than trimethylgallium (TMG), making TEG a preferred source of gallium for BGaAs epitaxy. Using TEB together with TEG, a higher boron composition (x = 4%-7%) has been achieved than has been previously reported, but we are still unable to achieve high- quality BGaInAs with the correct composition for solar cell applications.

  3. Fabrication of GaN nanotubular material using MOCVD with an aluminium oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-01-01

    GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200-250 nm and the wall thickness is about 40-50 nm. GaN nanotubular material consists of numerous fine GaN particulates with size range 15-30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that the grains in GaN nanotubular material have a nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in an aluminium oxide template.

  4. Comparison of the optical characteristics of GaAs photocathodes grown using MBE and MOCVD

    NASA Astrophysics Data System (ADS)

    Bourree, Loig E.; Chasse, David R.; Thamban, P. L. Stephan; Glosser, Robert

    2003-02-01

    Modern image tube intensifier photocathodes rely on a GaAs active layer, which has traditionally been grown using metallorganic chemical vapor deposition (MOCVD) due to its high throughput and lower cost of operation. Molecular beam epitaxy (MBE) processes have not been thoroughly investigated in that context. The latter technique demonstrates greater structural interface control as well as an improved growth quality for a multitude of applications. Still, at this point it is uncertain, considering actual fabrication techniques for image intensifiers, that the higher growth quality will result in an improvement of devices. Studies are being carried out to compare fundamental optical parameters between GaAs photocathodes grown by both MOCVD and MBE following the same growth and fabrication guidelines. These experiments involve using photoluminescence and Raman spectroscopy to obtain electron and phonon energy information on the materials. An atomic force microscope (AFM) is employed to compare the surface roughness of both methods. In addition, the white light responses of the photocathodes are also evaluated during the creation of a negative electron affinity (NEA) surface to observe any differences between the two growth techniques.

  5. The quest towards epitaxial BaMgF4 thin films: exploring MOCVD as a chemical scalable approach for the deposition of complex metal fluoride films.

    PubMed

    Battiato, Sergio; Deschanvres, Jean-Luc; Roussel, Hervé; Rapenne, Laetitia; Doisneau, Béatrice; Condorelli, Guglielmo G; Muñoz-Rojas, David; Jiménez, Carmen; Malandrino, Graziella

    2016-11-28

    Conventional and Pulsed Liquid Injection MOCVD processes (C-MOCVD and PLI-MOCVD) have been explored as synthetic routes for the growth of BaMgF4 on Si (100) and single crystalline SrTiO3 (100) substrates. For the two applied approaches, the volatile, thermally stable β-diketonate complexes Ba(hfa)2tetraglyme and Mg(hfa)2(diglyme)2(H2O)2 have been used as single precursors (C-MOCVD) or as a solution multimetal source (PLI-MOCVD). Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial BaMgF4 films on SrTiO3 substrates. Energy dispersive X-ray (EDX) analyses have been used to confirm composition and purity of deposited films. The impact of process parameters on film properties has been addressed, highlighting the strong influence of precursor ratio, deposition temperature and oxygen partial pressure on composition, microstructure and morphology of the films. Both methods appear well suited for the growth of the BaMgF4 phase, but while PLI-MOCVD yields a more straightforward control of the precursor composition that reflects on film stoichiometry, C-MOCVD provides easier control of the degree of texturing as a function of temperature.

  6. Acoustic-Levitation Chamber

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Granett, D.; Lee, M. C.

    1984-01-01

    Uncontaminated environments for highly-pure material processing provided within completely sealed levitation chamber that suspends particles by acoustic excitation. Technique ideally suited for material processing in low gravity environment of space.

  7. The Mars Chamber

    NASA Image and Video Library

    The Mars chamber is a box about the size of a refrigerator that re-creates the temperatures, pressures, and atmosphere of the Martian surface, essentially creating a Mars environment on Earth! Scie...

  8. Sleeve reaction chamber system

    SciTech Connect

    Northrup, M Allen; Beeman, Barton V; Benett, William J; Hadley, Dean R; Landre, Phoebe; Lehew, Stacy L; Krulevitch, Peter A

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  9. Thrust chamber life prediction

    NASA Technical Reports Server (NTRS)

    Kasper, H. J.

    1985-01-01

    The reusable life of the Space Shuttle main engine (SSME) is influenced by the cyclic life of the regeneratively liquid cooled main combustion chamber (MCC). During an operational duty cycle the MCC liner is subjected to a large transient thermal gradient that imparts a high thermal cyclic strain to the liner hot gas wall. Life predictions of such chambers have usually been based on low cycle fatigue (LCF) evaluations. Hot-fire testing, however, has shown significant mid-channel wall deformation and thinning during accrued cyclic testing. This phenomenon is termed cyclic creep and appears to be significantly accelerated at elevated temperatures. An analytical method that models the cyclic creep phenomenon and its application to thrust chamber life prediction is presented. The chamber finite element geometry is updated periodically to account for accrued wall thinning and distortion. Failure is based on the tensile instability failure criterion. Cyclic life results for several chamber life enhancing coolant channel designs are compared to the typically used LCF analysis that neglects cyclic creep. The results show that the usable cyclic creep life is approximately 30 to 50% of the commonly used LCF life.

  10. Improved Rhenium Thrust Chambers

    NASA Technical Reports Server (NTRS)

    O'Dell, John Scott

    2015-01-01

    Radiation-cooled bipropellant thrust chambers are being considered for ascent/ descent engines and reaction control systems on various NASA missions and spacecraft, such as the Mars Sample Return and Orion Multi-Purpose Crew Vehicle (MPCV). Currently, iridium (Ir)-lined rhenium (Re) combustion chambers are the state of the art for in-space engines. NASA's Advanced Materials Bipropellant Rocket (AMBR) engine, a 150-lbf Ir-Re chamber produced by Plasma Processes and Aerojet Rocketdyne, recently set a hydrazine specific impulse record of 333.5 seconds. To withstand the high loads during terrestrial launch, Re chambers with improved mechanical properties are needed. Recent electrochemical forming (EL-Form"TM") results have shown considerable promise for improving Re's mechanical properties by producing a multilayered deposit composed of a tailored microstructure (i.e., Engineered Re). The Engineered Re processing techniques were optimized, and detailed characterization and mechanical properties tests were performed. The most promising techniques were selected and used to produce an Engineered Re AMBR-sized combustion chamber for testing at Aerojet Rocketdyne.

  11. Target Chamber Manipulator

    NASA Astrophysics Data System (ADS)

    Tantillo, Anthony; Watson, Matthew

    2015-11-01

    A system has been developed to allow remote actuation of sensors in a high vacuum target chamber used with a particle accelerator. Typically, sensors of various types are placed into the target chamber at specific radial and angular positions relative to the beam line and target. The chamber is then evacuated and the experiments are performed for those sensor positions. Then, the chamber is opened, the sensors are repositioned to new angles or radii, and the process is repeated, with a separate pump-down cycle for each set of sensor positions. The new sensor positioning system allows scientists to pre-set the radii of up to a dozen sensors, and then remotely actuate their angular positions without breaking the vacuum of the target chamber. This reduces the time required to reposition sensors from 6 hours to 1 minute. The sensors are placed into one of two tracks that are separately actuated using vacuum-grade stepping motors. The positions of the sensors are verified using absolute optical rotary encoders, and the positions are accurate to 0.5 degrees. The positions of the sensors are electronically recorded and time-stamped after every change. User control is through a GUI using LabVIEW.

  12. MOCVD growth of CdO very thin films: Problems and ways of solution

    NASA Astrophysics Data System (ADS)

    Huerta-Barberà, Adelaida; Guia, Lluís Manel; Klymov, Oleksii; Marín-Borrás, Vicente; Martínez-Tomás, Carmen; Tamayo-Arriola, Julen; Kurtz, Alejandro; Montes Bajo, Miguel; Muñoz, Elias; Hierro, Adrian; Muñoz-Sanjosé, Vicente

    2016-11-01

    In this paper the growth of CdO by the MOCVD technique at atmospheric pressure has been studied in order to achieve very thin films of this material on r-sapphire substrates. The growth evolution of these films was discussed and the existence of a threshold thickness, below which island-shaped structures appear, was demonstrated. Some alternatives to reduce this threshold thickness have been proposed in the frame of the analysis of the crystal growth process. The morphology and structural properties of the films were analyzed by means of SEM and HRXRD. High-quality flat CdO samples were achieved with thicknesses up to 20 nm, which is five times thinner than the values previously reported in the literature.

  13. Monitoring and Controlling of Strain During MOCVD of AlGaN for UV Optoelectronics

    SciTech Connect

    Han, J.; Crawford, M.H.; Shul, R.J.; Hearne, S.J.; Chason, E.; Figiel, J.J.; Banas, M.

    1999-01-14

    The grown-in tensile strain, due to a lattice mismatch between AlGaN and GaN, is responsible for the observed cracking that seriously limits the feasibility of nitride-based ultraviolet (UV) emitters. We report in-situ monitoring of strain/stress during MOCVD of AlGaN based on a wafer-curvature measurement technique. The strain/stress measurement confirms the presence of tensile strain during growth of AlGaN pseudomorphically on a thick GaN layer. Further growth leads to the onset of stress relief through crack generation. We find that the growth of AlGaN directly on low-temperature (LT) GaN or AlN buffer layers results in a reduced and possibly controllable strain.

  14. Three-dimensional modelling of horizontal chemical vapor deposition. I - MOCVD at atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Ouazzani, Jalil; Rosenberger, Franz

    1990-01-01

    A systematic numerical study of the MOCVD of GaAs from trimethylgallium and arsine in hydrogen or nitrogen carrier gas at atmospheric pressure is reported. Three-dimensional effects are explored for CVD reactors with large and small cross-sectional aspect ratios, and the effects on growth rate uniformity of tilting the susceptor are investigated for various input flow rates. It is found that, for light carrier gases, thermal diffusion must be included in the model. Buoyancy-driven three-dimensional flow effects can greatly influence the growth rate distribution through the reactor. The importance of the proper design of the lateral thermal boundary conditions for obtaining layers of uniform thickness is emphasized.

  15. Growth of AlN nanostructure on GaN using MOCVD

    SciTech Connect

    Loganathan, R.; Ramesh, R.; Jayasakthi, M.; Prabakaran, K.; Kuppulingam, B.; Sankaranarayanan, M.; Balaji, M.; Arivazhagan, P.; Singh, Subra; Baskar, K.

    2015-06-24

    Aluminum nitride (AlN) nanowalls have been epitaxially grown on dislocation assisted GaN/Al{sub 2}O{sub 3} template by metal organic chemical vapor deposition (MOCVD) without any help of metal catalysts. A large number of nanowalls with thicknesses of 1.5-2.0 µm and height 400 nm have been deposited. The AlN nanowalls were found to have a preferred c-axis oriented with a hexagonal crystal structure. The AlN nanowalls and GaN/Al{sub 2}O{sub 3} template have been characterize at room temperature photoluminescence (PL) and high resolution X-ray diffraction (HRXRD)

  16. Formation of ohmic contacts to MOCVD grown p-GaN by controlled activation of Mg

    SciTech Connect

    Kaminska, E.; Piotrowska, A.; Barcz, A.; Bour, D.; Zielinski, M.; Jasinski, J.

    2000-11-27

    We report on the formation of low resistivity ohmic contacts to p-GaN, r{sub c} < 10{sup {minus}4}{Omega}cm{sup 2}, by increasing the concentration of the active Mg in the subcontact zone, via Zr-mediated release of hydrogen. We have investigated the process of evolution of hydrogen from MOCVD grown p-GaN via Zr-based metallization, and determined the optimum processing conditions (temperature and gas ambient) for fabrication of low resistance ohmic contacts. When the process is conducted in N{sub 2} flow, the metallization remains stable at temperatures required to achieve the ohmic behavior, and the morphology of the metal/semiconductor interface is unaltered by such a heat treatment. The processing in O{sub 2}, on the contrary, causes the interdiffusion of metallization constituents and the incorporation of oxygen into the semiconductor subcontact region, which could be responsible for increased resistivity of these contacts.

  17. Growth of III-V nitride materials by MOCVD for device applications

    NASA Astrophysics Data System (ADS)

    Eiting, Christopher James

    This dissertation describes an investigation of the growth of gallium nitride (GaN) and aluminum gallium nitride (AlxGa1-x N) semiconductor materials by metalorganic chemical vapor deposition (MOCVD) for heterojunction field-effect transistor (HFET) and photodetector device applications. In Chapter I, the III-V nitride material system is discussed, and the current status of growth and device research in this material system is reviewed. Chapter 2 presents a detailed discussion of two important tensor properties of the wurtzite III-V nitrides: elasticity and piezoelectricity. In this discussion, a series of equations are developed that are used throughout this work to calculate properties such as strain, composition, and piezoelectric charge. In Chapter 3, the characterization techniques used to gather data for this dissertation are described. Particular attention is given to x-ray diffraction because of the usefulness and versatility of this technique. Chapter 4 is a description of the MOCVD reactor used to grow all of the films in this work. Chapter 5 presents a complete discussion of the growth and doping of GaN epitaxial layers. This chapter is divided into five sections: buffer layer optimization, GaN:ud growth, GaN:Si growth, Si-implantation of GaN, and GaN:Mg growth. In Chapter 6, the focus shifts to AlGaN epitaxial growth. The first part of the chapter is devoted to the growth and doping of AlGaN layers, while the second part deals with the characteristics of AlGaN/GaN heterostructures. Chapter 7 displays some of the device data from HFETs and photodetectors fabricated from the material described in Chapter 5 and Chapter 6. Finally, this dissertation concludes with Chapter 8, a summary of results and a discussion of potential research for the future.

  18. Study of GaP single crystal layers grown on GaN by MOCVD

    SciTech Connect

    Li, Shuti; Liu, Chao; Ye, Guoguang; Xiao, Guowei; Zhou, Yugang; Su, Jun; Fan, Guanghan; Zhang, Yong; Liang, Fubo; Zheng, Shuwen

    2011-11-15

    Highlights: {yields} We investigated the growth of GaP layers on GaN by MOCVD. {yields} A single crystal GaP layer could be grown on GaN. {yields} The V/III ratio played an important role to improve GaP layer quality. {yields} The GaP:Mg layer with hole concentration of 4.2 x 10{sup 18} cm{sup -3} was obtained. -- Abstract: The performance of GaN based devices could possibly be improved by utilizing the good p-type properties of GaP layer and it provides the possibility of the integration of InAlGaN and AlGaInP materials to produce new devices, if high quality GaP compounds can be grown on III-nitride compounds. In this paper, the growth of GaP layers on GaN by metalorganic chemical vapor deposition (MOCVD) has been investigated. The results show that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature GaP growth. Using a 40 nm thick GaP buffer layer, a single crystal GaP layer, whose full-width at half-maximum of the (1 1 1) plane measured by double crystal X-ray diffraction is 580'', can be grown on GaN. The V/III ratio plays an important role in the GaP layer growth and an appropriate V/III ratio can improve the quality of GaP layer. The GaP:Mg layer with hole carrier concentration of 4.2 x 10{sup 18} cm{sup -3} has been obtained.

  19. Automated Electrostatics Environmental Chamber

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Lewis, Dean C.; Buchanan, Randy K.; Buchanan, Aubri

    2005-01-01

    The Mars Electrostatics Chamber (MEC) is an environmental chamber designed primarily to create atmospheric conditions like those at the surface of Mars to support experiments on electrostatic effects in the Martian environment. The chamber is equipped with a vacuum system, a cryogenic cooling system, an atmospheric-gas replenishing and analysis system, and a computerized control system that can be programmed by the user and that provides both automation and options for manual control. The control system can be set to maintain steady Mars-like conditions or to impose temperature and pressure variations of a Mars diurnal cycle at any given season and latitude. In addition, the MEC can be used in other areas of research because it can create steady or varying atmospheric conditions anywhere within the wide temperature, pressure, and composition ranges between the extremes of Mars-like and Earth-like conditions.

  20. Antipollution combustion chamber

    SciTech Connect

    Caruel, J.E.; Gastebois, P.M.

    1981-01-27

    The invention concerns a combustion chamber for turbojet engines. The combustion chamber is of the annular type and consists of two coaxial flame tubes opening into a common dilution and mixing zone. The inner tube is designed for low operating ratings of the engine, the outer tube for high ratings. Air is injected as far upstream as possible into the dilution zone, to enhance the homogenization of the gaseous flow issuing from the two tubes prior to their passage into the turbine and to assure the optimum radial distribution of temperatures. The combustion chamber according to the invention finds application in a particularly advantageous manner in turbojet engines used in aircraft propulsion because of the reduced emission of pollutants it affords.

  1. Filament wound rocket motor chambers

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The design, analysis, fabrication and testing of a Kevlar-49/HBRF-55A filament wound chamber is reported. The chamber was fabricated and successfully tested to 80% of the design burst pressure. Results of the data reduction and analysis from the hydrotest indicate that the chamber design and fabrication techniques used for the chamber were adequate and the chamber should perform adequately in a static test.

  2. Automated soil gas monitoring chamber

    DOEpatents

    Edwards, Nelson T.; Riggs, Jeffery S.

    2003-07-29

    A chamber for trapping soil gases as they evolve from the soil without disturbance to the soil and to the natural microclimate within the chamber has been invented. The chamber opens between measurements and therefore does not alter the metabolic processes that influence soil gas efflux rates. A multiple chamber system provides for repetitive multi-point sampling, undisturbed metabolic soil processes between sampling, and an essentially airtight sampling chamber operating at ambient pressure.

  3. Electrostatic Levitator Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (beam passes through the window at left), positioning lasers (one port is at center), and lamps to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  4. Improved wire chamber

    DOEpatents

    Atac, M.

    1987-05-12

    An improved gas mixture for use with proportional counter devices, such as Geiger-Mueller tubes and drift chambers. The improved gas mixture provides a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor. 2 figs.

  5. Parmitano with MDCA chamber

    NASA Image and Video Library

    2013-07-24

    ISS036-E-025481 (24 July 2013) --- European Space Agency astronaut Luca Parmitano, Expedition 36 flight engineer, works on the Multi-User Droplet Combustion Apparatus (MDCA) Chamber Insert Assembly (CIA) at a maintenance work station in the Harmony node of the International Space Station.

  6. Metabolic simulation chamber

    NASA Technical Reports Server (NTRS)

    Bartlett, R. G.; Hendricks, C. M.

    1972-01-01

    Metabolic simulation combustion chamber was developed as subsystem for breathing metabolic simulator. Entire system is used for evaluation of life support and resuscitation equipment. Metabolism subsystem simulates a human by consuming oxygen and producing carbon dioxide. Basic function is to simulate human metabolic range from rest to hard work.

  7. Flame-Test Chamber

    NASA Technical Reports Server (NTRS)

    Bjorklund, R. A.

    1984-01-01

    Experimental chamber provides controlled environment for observation and measurement of flames propagating in expanding plume of flammable air/fuel mixture under atmospheric conditions. Designed to evaluate quenching capability of screen-type flame arresters in atmospheric vents of fuel cargo tanks aboard marine cargo vessels.

  8. Liquid Wall Chambers

    SciTech Connect

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  9. Temperature coefficients and radiation induced DLTS spectra of MOCVD grown n(+)p InP solar cells

    NASA Technical Reports Server (NTRS)

    Walters, Robert J.; Statler, Richard L.; Summers, Geoffrey P.

    1991-01-01

    The effects of temperature and radiation on n(+)p InP solar cells and mesa diodes grown by metallorganic chemical vapor deposition (MOCVD) were studied. It was shown that MOCVD is capable of consistently producing good quality InP solar cells with Eff greater than 19 percent which display excellent radiation resistance due to minority carrier injection and thermal annealing. It was also shown that universal predictions of InP device performance based on measurements of a small group of test samples can be expected to be quite accurate, and that the degradation of an InP device due to any incident particle spectrum should be predictable from a measurement following a single low energy proton irradiation.

  10. Study of high {Tc} superconducting thin films grown by MOCVD. Final report, July 1, 1986--April 30, 1990

    SciTech Connect

    Erbil, A.

    1990-12-31

    Work is described briefly, which was carried out on development of techniques to grow metal-semiconductor superlattices (artificially layered materials) and on the copper oxide based susperconductors (naturally layered materials). The current growth technique utilized is metalorganic chemical vapor deposition (MOCVD). CdTe, PbTe, La, LaTe, and Bi{sub 2}Te{sub 3} were deposited, mostly on GaAs. Several YBa{sub 2}Cu{sub 3}O{sub 7} compounds were obtained with possible superconductivity at temperatures up to 550 K (1 part in 10{sup 4}). YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} and Tl{sub 2}CaBa{sub 2}Cu{sub 2}O{sub y} thin films were deposited by MOCVD on common substrates such as glass.

  11. Interface Structures in AlGaAs/GaAs Quantum Wells Grown by Metalorganic Chemical Vapor Deposition (MOCVD)

    NASA Astrophysics Data System (ADS)

    Ikuta, Kenji; Shinohara, Masanori; Inoue, Naohisa

    1995-02-01

    AlGaAs/GaAs quantum wells (QWs) were grown by metalorganic chemical vapor deposition (MOCVD) with controlled growth modes: step propagation, and mixtures of step propagation and two-dimensional nucleation. Surface structure on the multilayers was characterized by atomic force microscopy. Photoluminescence (PL) spectra from the QWs with such well-controlled and well-characterized interfaces were obtained for the first time, and PL linewidths were explained by the observed surface structures and growth modes.

  12. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-06-27

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  13. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-10-17

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  14. Combustor with fuel preparation chambers

    NASA Technical Reports Server (NTRS)

    Zelina, Joseph (Inventor); Myers, Geoffrey D. (Inventor); Srinivasan, Ram (Inventor); Reynolds, Robert S. (Inventor)

    2001-01-01

    An annular combustor having fuel preparation chambers mounted in the dome of the combustor. The fuel preparation chamber comprises an annular wall extending axially from an inlet to an exit that defines a mixing chamber. Mounted to the inlet are an air swirler and a fuel atomizer. The air swirler provides swirled air to the mixing chamber while the atomizer provides a fuel spray. On the downstream side of the exit, the fuel preparation chamber has an inwardly extending conical wall that compresses the swirling mixture of fuel and air exiting the mixing chamber.

  15. 44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), LOOKING NORTHEAST SHOWING DRAIN PIPE FROM SUMP - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  16. 72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR AND CANAL (LOCATION T) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  17. Process in manufacturing high efficiency AlGaAs/GaAs solar cells by MO-CVD

    NASA Technical Reports Server (NTRS)

    Yeh, Y. C. M.; Chang, K. I.; Tandon, J.

    1984-01-01

    Manufacturing technology for mass producing high efficiency GaAs solar cells is discussed. A progress using a high throughput MO-CVD reactor to produce high efficiency GaAs solar cells is discussed. Thickness and doping concentration uniformity of metal oxide chemical vapor deposition (MO-CVD) GaAs and AlGaAs layer growth are discussed. In addition, new tooling designs are given which increase the throughput of solar cell processing. To date, 2cm x 2cm AlGaAs/GaAs solar cells with efficiency up to 16.5% were produced. In order to meet throughput goals for mass producing GaAs solar cells, a large MO-CVD system (Cambridge Instrument Model MR-200) with a susceptor which was initially capable of processing 20 wafers (up to 75 mm diameter) during a single growth run was installed. In the MR-200, the sequencing of the gases and the heating power are controlled by a microprocessor-based programmable control console. Hence, operator errors can be reduced, leading to a more reproducible production sequence.

  18. Three chamber negative ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.; Hiskes, John R.

    1985-01-01

    A negative ion vessel is divided into an excitation chamber, a negative ionization chamber and an extraction chamber by two magnetic filters. Input means introduces neutral molecules into a first chamber where a first electron discharge means vibrationally excites the molecules which migrate to a second chamber. In the second chamber a second electron discharge means ionizes the molecules, producing negative ions which are extracted into or by a third chamber. A first magnetic filter prevents high energy electrons from entering the negative ionization chamber from the excitation chamber. A second magnetic filter prevents high energy electrons from entering the extraction chamber from the negative ionizing chamber. An extraction grid at the end of the negative ion vessel attracts negative ions into the third chamber and accelerates them. Another grid, located adjacent to the extraction grid, carries a small positive voltage in order to inhibit positive ions from migrating into the extraction chamber and contour the plasma potential. Additional electrons can be suppressed from the output flux using ExB forces provided by magnetic field means and the extractor grid electric potential.

  19. Multiwire proportional chamber development

    NASA Technical Reports Server (NTRS)

    Doolittle, R. F.; Pollvogt, U.; Eskovitz, A. J.

    1973-01-01

    The development of large area multiwire proportional chambers, to be used as high resolution spatial detectors in cosmic ray experiments is described. A readout system was developed which uses a directly coupled, lumped element delay-line whose characteristics are independent of the MWPC design. A complete analysis of the delay-line and the readout electronic system shows that a spatial resolution of about 0.1 mm can be reached with the MWPC operating in the strictly proportional region. This was confirmed by measurements with a small MWPC and Fe-55 X-rays. A simplified analysis was carried out to estimate the theoretical limit of spatial resolution due to delta-rays, spread of the discharge along the anode wire, and inclined trajectories. To calculate the gas gain of MWPC's of different geometrical configurations a method was developed which is based on the knowledge of the first Townsend coefficient of the chamber gas.

  20. Crystals in magma chambers

    NASA Astrophysics Data System (ADS)

    Higgins, M.

    2011-12-01

    Differentiation processes in igneous systems are one way in which the diversity of igneous rocks is produced. Traditionally, magmatic diversity is considered as variations in the overall chemical composition, such as basalt and rhyolite, but I want to extend this definition to include textural diversity. Such textural variations can be manifested as differences in the amount of crystalline (and immiscible liquid) phases and in the origin and identity of such phases. One important differentiation process is crystal-liquid separation by floatation or decantation, which clearly necessitates crystals in the magma. Hence, it is important to determine if magmas in chambers (sensu lato) have crystals. The following discussion is framed in generalities - many exceptions occur. Diabase (dolerite) dykes are a common, widespread result of regional mafic magmatism. The rims of most diabase dykes have few or no phenocrysts and crystals in the cores are commonly thought to have crystallized in place. Hence, this major mafic magmatic source did not have crystals, although compositional diversity of these dykes is commonly explained by crystal-liquid separation. This can be resolved if crystallisation was on the walls on the magma chamber. Similarly, most flood basalts are low in crystals and separation of those that are present cannot always explain the observed compositional diversity. Crystal-rich flows do occur, for example the 'Giant Plagioclase Basalts' of the Deccan series, but the crystals are thought to form or accumulate in a crystal-rich zone beneath the roof of the chamber - the rest of the chamber probably has few crystals. Some magmas from Hawaii contain significant amounts of olivine crystals, but most of these are deformed and cannot have crystallised in the chamber. In this case the crystals are thought to grow as the magma passes through a decollement zone. They may have grown on the walls or been trapped by filters. Basaltic andesite ignimbrites generally have

  1. Electrostatic Levitator Vacuum Chambers

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (such as the deuterium arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  2. Digital optical spark chambers

    NASA Technical Reports Server (NTRS)

    Evenson, Paul; Tuska, Evelyn

    1989-01-01

    The authors constructed and tested a prototype digital readout system for optical spark chambers using a linear, solid-state charge-coupled-device detector array. Position resolution of 0.013 mm (sigma) over a 25-cm field of view has been demonstrated. It is concluded that this technique should permit the construction of economical, lightweight and low-power trajectory hodoscopes for use in cosmic-ray instrumentation on balloons and in spacecraft.

  3. Columbium Chamber Fabrication Study

    DTIC Science & Technology

    1984-07-01

    materials. Demonstrate CVO close-out of slotted, filled, C103 columbium alloy panels and subsequent removal of the filler materials. 1.0, Introduction...their removal subsequent to CV0 of a columbium close-out. C103 columbium alloy plate, procured to Aeronautical Materials Specification (SAE) -- AMS 7852...into the chamber. Surface oxygen contamination of the C103 columbium alloy wcs evident in all metallographic sections. 8.1 LOW TEMPERATURE DEPOSIT

  4. Combustion chamber noise suppressor

    SciTech Connect

    Livingston, A.M.

    1986-08-19

    A combustion chamber is described for a hot fog generating machine comprising a hollow cylindrical combustion chamber shell having a closure plate at one end and outlet means at the opposite end for directing hot combustion gasses to a fogging nozzle, air inlet means disposed adjacent the outlet means, fuel inlet means and ignition means mounted in the closure plate and liner means disposed concentrically within the cylindrical combustion chamber for controlling the flow of air and combustion gasses within the shell. The liner means includes a liner base having a frustroconical configuration with the smaller diameter end thereof disposed in communication with the outlet means and with the larger diameter end thereof disposed in spaced relation to the shell, circumferentially spaced, longitudinally extending fins extending outwardly from the liner base intermediate the liner base and the shell, a cylindrical liner midsection having circumferentially spaced fins extending outwardly therefrom between the midsection and the shell with the fins supporting the midsection on the larger diameter end of the liner base.

  5. Advanced indium phosphide based monolithic integration using quantum well intermixing and MOCVD regrowth

    NASA Astrophysics Data System (ADS)

    Raring, James W.

    The proliferation of the internet has fueled the explosive growth of telecommunications over the past three decades. As a result, the demand for communication systems providing increased bandwidth and flexibility at lower cost continues to rise. Lightwave communication systems meet these demands. The integration of multiple optoelectronic components onto a single chip could revolutionize the photonics industry. Photonic integrated circuits (PIC) provide the potential for cost reduction, decreased loss, decreased power consumption, and drastic space savings over conventional fiber optic communication systems comprised of discrete components. For optimal performance, each component within the PIC may require a unique epitaxial layer structure, band-gap energy, and/or waveguide architecture. Conventional integration methods facilitating such flexibility are increasingly complex and often result in decreased device yield, driving fabrication costs upward. It is this trade-off between performance and device yield that has hindered the scaling of photonic circuits. This dissertation presents high-functionality PICs operating at 10 and 40 Gb/s fabricated using novel integration technologies based on a robust quantum-well-intermixing (QWI) method and metal organic chemical vapor deposition (MOCVD) regrowth. We optimize the QWI process for the integration of high-performance quantum well electroabsorption modulators (QW-EAM) with sampled-grating (SG) DBR lasers to demonstrate the first widely-tunable negative chirp 10 and 40 Gb/s EAM based transmitters. Alone, QWI does not afford the integration of high-performance semiconductor optical amplifiers (SOA) and photodetectors with the transmitters. To overcome this limitation, we have developed a novel high-flexibility integration scheme combining MOCVD regrowth with QWI to merge low optical confinement factor SOAs and 40 Gb/s uni-traveling carrier (UTC) photodiodes on the same chip as the QW-EAM based transmitters. These high

  6. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1999-03-16

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  7. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  8. Seedling-Size Fumigation Chambers

    Treesearch

    Keith F. Jensen; Frederick W. Bender

    1977-01-01

    The design of fumigation chambers is described. Each chamber has individual temperature, humidity, light, and pollutant control. Temperature is variable from 15 to 35ºC and controlled within ± 1ºC. Humidity is variable from 25 to 95 percent and controlled within ± 3 percent. Seedlings have been successfully grown in these chambers...

  9. Multi-anode ionization chamber

    DOEpatents

    Bolotnikov, Aleksey E.; Smith, Graham; Mahler, George J.; Vanier, Peter E.

    2010-12-28

    The present invention includes a high-energy detector having a cathode chamber, a support member, and anode segments. The cathode chamber extends along a longitudinal axis. The support member is fixed within the cathode chamber and extends from the first end of the cathode chamber to the second end of the cathode chamber. The anode segments are supported by the support member and are spaced along the longitudinal surface of the support member. The anode segments are configured to generate at least a first electrical signal in response to electrons impinging thereon.

  10. Deep Level Donor-like Centers in MOCVD-grown n-type GaN

    NASA Astrophysics Data System (ADS)

    Ahoujja, Mo; Yeo, Y. K.; Hengehold, R. L.; Johnstone, D. K.

    2002-03-01

    Defects in semiconductors are of high importance because they adversely affect device performance. For example, defects may act as carrier trap and generation centers which may lead to premature current leakage, and they may also act as non-radiative recombination centers that may reduce the quantum efficiency of electro-optical devices. Therefore understanding the dynamical properties of deep level defects is an important step toward improving device performance. In this work, deep level defects in GaN grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been investigated using isothermal capacitance transient spectroscopy (ICTS) and current voltage temperature (IVT) measurements. ICTS analyses show that there are two deep levels of E3 and E4 with emission activation energies of 0.55 and 0.61 eV below the conduction band, respectively, at room temperature. The E4 trap center was found to be the most dominant defect having a larger cross section, smaller capture barrier, and higher concentration. The results from the I-V-T measurements show that this deep center is at about 0.54 eV below the conduction band, and decreases with increasing reverse bias voltage, indicating characteristics of a center with a donor nature. Further analyses of the trap filling dynamics reveal a coupled behavior nature between E3 and E4 traps.

  11. EFFECTS OF Au ON THE GROWTH OF ZnO NANOSTRUCTURES ON Si BY MOCVD

    NASA Astrophysics Data System (ADS)

    Cong, Chen; Fan, Lu Yang; Ping, He Hai; Wei, Wu Ke; Zhen, Ye Zhi

    2013-06-01

    The effects of Au on the growth of ZnO nanostructures on Si by metal organic chemical vapor deposition (MOCVD) at a relatively low temperature (450°C) were investigated. The experimental results showed that Au nanoparticles played a critical role during the growth of the ZnO nanostructures and affected their morphology and optical properties. It was found that Au nanoparticles particularly affected the nucleation of ZnO nanostructures during the growth process and the Au-assisted growth mechanism of ZnO nanostructures should be ascribed to the vapor-solid (VS) mechanism. The formation of a nanoneedle may be attributed to a more reactive interface between Au and ZnO, which leads to more zinc gaseous species absorbed near the interface. Different nucleation sites on ZnO nuclei resulted in the disorder of ZnO nanoneedles. Moreover, the crystalline quality of nano-ZnO was improved due to the presence of Au, according to the smaller full width at half maximum (FWHM) of the low-temperature exciton emission. We confirmed that ZnO nanoneedles showed better crystalline quality than ZnO nanorods through the HRTEM images and the SAED patterns. The reason for the improvement of the crystalline quality of nano-ZnO may be due to the less lattice mismatch.

  12. Structural and optical properties of anatase TiO2 heteroepitaxial films prepared by MOCVD

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Feng, Xianjin; Xiao, Hongdi; Luan, Caina; Ma, Jin

    2016-11-01

    High-quality single-crystal anatase TiO2(a-TiO2) thin films have been obtained on SrTiO3 (STO) substrates using the metalorganic chemical vapor deposition (MOCVD) method. The optimal preparation process was explored. The lattice structure and epitaxial relationship were investigated by X-ray diffraction (XRD, both θ-2θ and Φ scans) and transmission electron microscopy (TEM). The results indicated that the film prepared at 550 °C with the Ti precursor molar flow rate of 4×10-7 mol/min had the best single crystalline quality, for which a clear epitaxial relationship of a-TiO2 (001)||STO (100) with a-TiO2 [100]||STO [001bar] could be inferred. The elemental composition and proportion were studied by the X-ray photoelectron spectroscopy (XPS) method, which proved the deposited film approximated stoichiometric TiO2. The samples showed high transparency of 70-80% in the visible range.

  13. Effect of Deposition Temperature on the Properties of TIO2 Thin Films Deposited by Mocvd

    NASA Astrophysics Data System (ADS)

    Khalifa, Zaki S.

    2016-02-01

    Crystal structure, microstructure, and optical properties of TiO2 thin films deposited on quartz substrates by metal-organic chemical vapor deposition (MOCVD) in the temperature range from 250∘C to 450∘C have been studied. The crystal structure, thickness, microstructure, and optical properties have been carried out using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), and UV-visible transmittance spectroscopy, respectively. XRD patterns show that the obtained films are pure anatase. Simultaneously, the crystal size calculated using XRD peaks, and the grain size measured by AFM decrease with the increase in deposition temperature. Moreover, the texture of the films change and roughness decrease with the increase in deposition temperature. The spectrophotometric transmittance spectra have been used to calculate the refractive index, extinction coefficient, dielectric constant, optical energy gap, and porosity of the deposited films. While the refractive index and dielectric constant decrease with the increase of deposition temperature, the porosity shows the opposite.

  14. Process control of MOCVD growth for LEDs by in-situ photoluminescence

    NASA Astrophysics Data System (ADS)

    Prall, C.; Haberland, K.; Kaspari, C.; Brunner, F.; Weyers, M.; Rueter, D.

    2016-03-01

    Development and manufacturing of LED structures is still driven by production cost reduction and performance improvements. Therefore, in-situ monitoring during the epitaxial process plays a key role in view of further yield improvement and process optimization. With the continuing trend towards larger wafers, stronger bow and increased aspherical curvature are additional challenges the growers have to face, leading to non-uniform LED-emission. Compared to traditional in-situ metrology like curvature measurement and near UV pyrometry, in-situ photoluminescence measurements can provide a more direct access to the quantum well emission already during growth. In this paper we show how in-situ photoluminescence measurements can be used in a production type multi-wafer MOCVD system to characterize the quantum well emission already during growth. We also demonstrate how deviations from the desired wavelength can be detected and corrected in the same growth run. Since the method is providing spatially resolved line-scans across the wafer, also the uniformity of the emission wavelength can be characterized already during growth. Comparison of in-situ and ex-situ photoluminescence data show excellent agreement with respect to wavelength uniformity on 4 inch wafers.

  15. Influence of AlN thickness on AlGaN epilayer grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jayasakthi, M.; Juillaguet, S.; Peyre, H.; Konczewicz, L.; Baskar, K.; Contreras, S.

    2016-10-01

    AlGaN/AlN layers were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The AlN buffer thickness was varied from 400 nm to 800 nm. The AlGaN layer thickness was 1000 nm. The crystalline quality, thickness and composition of AlGaN were determined using high resolution X-ray diffraction (HRXRD). The threading dislocation density (TDD) was found to decrease with increase of AlN layer thickness. Reciprocal space mapping (RSM) was used to estimate the strain and relaxation between AlGaN and AlN. The optical properties of AlGaN layers were investigated by temperature dependent photoluminescence (PL). PL intensities of AlGaN layers increases with increasing the AlN thickness. The surface morphology of AlGaN was studied by atomic force microscopy (AFM). Root mean square (RMS) roughness values were found to be decreased while increase of AlN thickness.

  16. DC characteristics improvement of recessed gate GaN-based HFETs grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Cheng, A. T.; Su, Y. K.; Lai, W. C.; Huang, C. H.

    2007-01-01

    The effect of the recessed gate structure on DC characteristics of n-channel depletion mode heterostructure field effect transistors (HFETs) grown by metalorganic chemical vapor deposition (MOCVD) was demonstrated. The recessed gate process was carried out by using photo-enhanced chemical (PEC) wet etching. There were improvements on the electrical characteristics after using the recessed gate AlGaN/GaN and AlGaN/GaN/InGaN/GaN HFET structures because of the better gate controllability to the drain current. It was also found that the gate voltage, VGS, of the transconductance peak value shifted toward positive bias for the recessed gate structure. The leakage current, the transconductance ( Gm) and the saturation current of the recessed gate AlGaN/GaN/InGaN/GaN HFET with a 30-nm-thick Si-doped GaN cap layer are 1.95 mA/mm, 94.82 mA/mm and 230 mA/mm, respectively. This performance is quite better than that of the device with no recessed gate structure.

  17. Microstructure Characteristics of High Lift Factor MOCVD REBCO Coated Conductors With High Zr Content

    SciTech Connect

    Galstyan, E; Gharahcheshmeh, MH; Delgado, L; Xu, AX; Majkic, G; Selvamanickam, V

    2015-06-01

    We report the microstructural characteristics of high levels of Zr-added REBa2Cu3O7-x (RE = Gd, Y rare earth) coated conductors fabricated by Metal Organic Chemical Vapor Deposition (MOCVD). The enhancements of the lift factor defined as a ratio of the in-field (3 T, B parallel to c-axis) critical current density (J(c)) at 30 K and self-field J(c) at 77 K have been achieved for Zr addition levels of 20 and 25 mol% via optimization of deposition parameters. The presence of strong flux pinning is attributed to the aligned nanocolumns of BaZrO3 and nanoprecipitates embedded in REBa2Cu3O7-x matrix with good crystal quality. A high density of BZO nanorods with a typical size 6-8 nm and spacing of 20 nm has been observed. Moreover, the high Zr content was found to induce a high density of intrinsic defects, including stacking faults and dislocations. The correlation between in-field performance along the c-axis and microstructure of (Gd, Y) BCO film with a high level of Zr addition is discussed.

  18. Effect of silicon doping in InGaN/GaN heterostructure grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Surender, S.; Pradeep, S.; Prabakaran, K.; Singh, Shubra; Baskar, K.

    2017-05-01

    In this work the effect of Si doped InGaN/GaN heterostructure is systematically studied. The n-InGaN /GaN heterostructure are grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD). The heterostructure samples are investigated by structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature Photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. The composition of indium in n-InGaN/GaN heterostructure was calculated as 15.9% using epitaxy smooth fit software. The energy band gap (Eg) of the InGaN epilayer has been calculated as 2.78 eV using vigard's law. PL emission obtained at 446 nm for n-InGaN epilayer. AFM results indicate that the Si doped InGaN/GaN heterostructure has the root mean square (rms) roughness of about 0.59 nm for a scan area of 5×5 µm2 which has island like growth. Moreover, Hall measurements results shows that Si doped InGaN/GaN heterostructure possess carrier concentration of 4.2 × 1018cm-3 and mobility of 257 cm2/V s at room temperature.

  19. MOCVD synthesis of group III-nitride heterostructure nanowires for solid-state lighting.

    SciTech Connect

    Wang, George T.; Creighton, James Randall; Talin, Albert Alec

    2006-11-01

    Solid-state lighting (SSL) technologies, based on semiconductor light emitting devices, have the potential to reduce worldwide electricity consumption by more than 10%, which could significantly reduce U.S. dependence on imported energy and improve energy security. The III-nitride (AlGaInN) materials system forms the foundation for white SSL and could cover a wide spectral range from the deep UV to the infrared. For this LDRD program, we have investigated the synthesis of single-crystalline III-nitride nanowires and heterostructure nanowires, which may possess unique optoelectronic properties. These novel structures could ultimately lead to the development of novel and highly efficient SSL nanodevice applications. GaN and III-nitride core-shell heterostructure nanowires were successfully synthesized by metal organic chemical vapor deposition (MOCVD) on two-inch wafer substrates. The effect of process conditions on nanowire growth was investigated, and characterization of the structural, optical, and electrical properties of the nanowires was also performed.

  20. MOCVD of aluminium oxide films using aluminium β-diketonates as precursors

    NASA Astrophysics Data System (ADS)

    Devi, A.; Shivashankar, S. A.; Samuelson, A. G.

    2002-06-01

    Deposition of Al203 coatings by CVD is of importance because they are often used as abrading material in cemented carbide cutting tools. The conventionally used CVD process for Al203 involves the corrosive reactant AICl3. In this paper, we report on the thermal characterisation of the metalorganic precursors namely aluminium tris-tetramethyl-heptanedionate [ Al(thd)3] and aluminium tris-acetylacetonate [ Al(acac)3] and their application to the CVD of Al203 films. Crystalline A1203 films were deposited by MOCVD at low temperatures by the pyrolysis of Al(thd)3 and AI(acac)3. The films were deposited on a TiN-coated tungsten carbide (TiN/WC) and Si(100) substrates in the temperature range 500-1100 °C. The as-deposited films were characterised by x-ray diffraction, optical microscopy, scanning and transmission electron microscopy, Auger electron spectroscopy. The observed crystallinity of films grown at low temperatures, their microstructure, and composition may be interpreted in terms of a growth process that involves the melting of the metalorganic precursor on the hot growth surface.

  1. Growth of GaAs in a rotating disk MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Thompson, A. G.; Sundaram, V. S.; Girard, G. R.; Fraas, L. M.

    1989-04-01

    We report the growth of GaAs homoepitaxial films from trimethylgallium and arsine in a multi-wafer rotating disk reactor. In this configuration the substrates are mounted on a disk that is spun at high speed (> 1000 rpm) in a sub-atmospheric (<100 Torr) environment. The spinning disk pumps the reactant and carrier gases radially outwards; under optimum conditions, convective recirculating cells are avoided, thus facilitating rapid transitions in doping and composition in the grown layers. In this paper we look at the morphology, growth rate and electrical properties of the GaAs epitaxial layers as a function of substrate temperature, V/III ratio, dopant type, spin speed and hydrogen carrier flow conditions. These results are compared with those obtained in conventional MOCVD reactors. Silicon and tellurium doping over a wide range of carrier concentrations has been achieved with excellent mobilities and uniformity across the wafers. Preliminary results on MESFET's fabricated from n +/n/buffer structures show good device characteristics.

  2. Temperature variations in electrical and photoluminescence properties of ZnSe grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Giapis, Konstantinos P.; Lu, Da-Chen; Jensen, Klavs F.; Potts, John E.

    1990-07-01

    The effect of growth temperature on the optoelectronic properties of epitaxial ZnSe grown by metalorganic chemical vapor deposition (MOCVD) on GaAs (100) from dimethyl zinc and hydrogen selenide has been investigated in a vertical reactor. Chlorine was found to be the main donor impurity originating from Se, used to produce the hydrogen selenide. The deposited films were single crystalline for growth temperatures above 225°C and were characterized by low-temperature photoluminescence. With increasing growth temperature, the donor-bound excitonic emission decreased in intensity and linewidth, while the 77 K electron mobility increased. The trend continued until the free exciton became the dominant near-band-edge emission at a growth temperature of 350°C, at which point the films turned out to be highly resistive and Hall measurements could not be performed. High electron mobilities of 8000-9000 cm 2/V·s at 77 K were measured for growth temperatures of 325°C. The transition tto high resistivity was found to be accompanied by a sharp increase in the photoluminescence intensity of the Y0 emission, related to extended defects. Thermally activated dislocations and changes in the charge state of the Y0-related defect are proposed as possible mechanisms for these experimental observations.

  3. [The influential factors of MOCVD growth of InP in opals].

    PubMed

    Tan, Chun-hua; Fan, Guang-han; Huang, Xu-guang

    2008-12-01

    The key problem of fabricating the 3-D InP inverse opal photonic crystal is to increase the loading of InP in opals. In the present paper, low-pressure metal-organic chemical-vapour deposition (MOCVD) was used to infill the voids within synthetic opals with InP. The morphologies and optical properties of SiO2-InP photonic crystal were characterized by scanning electron microscopy and ultraviolet-visible spectrophotometry (UV-Vis). Several series of experiments were carried out in order to analyze the factors that influence the loading of InP in opals and determine the optimal InP growth conditions. The results of optical experiments are in good agreement with those derived from the theoretical considerations: By increasing the extent of InP infilling within the voids, the extent of refractive index contrast between the silica spheres and the void as well as the extent of natural optical properties change of the photonic crystal were increased. Cycle growth, low-pressure growth, and using the match substrate and the same configuration character between SiOi and InP are beneficial to increaseing the extent of InP infilling within the opal voids. The process has been optimized to achieve SiO2-InP photonic crystal with higher loading of InP. The study provides a scientific basis for manufacturing three-dimensional InP inverse opal photonic crystals.

  4. MOCVD growth of ZnO nanowire arrays for advanced UV detectors

    NASA Astrophysics Data System (ADS)

    Rivera, Abdiel; Mazady, Anas; Zeller, John; Anwar, Mehdi; Manzur, Tariq; Sood, Ashok

    2013-03-01

    Zinc oxide (ZnO) is a biocompatible and versatile functional material having a bandgap of 3.37 eV that exhibits both semiconducting and piezoelectric properties and has a diverse group of growth morphologies. We have grown highly ordered vertical arrays of ZnO nanowires (NWs) using a metal organic chemical vapor deposition (MOCVD) growth process on various substrates. The NWs were grown on p-Si (100), SiO2, and m-plane sapphire substrates. The structural and optical properties of the grown vertically aligned ZnO NW arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. The unique diffraction pattern for ZnO (002) concurred with the SEM inspection indicating vertical orientation of the NWs. UV detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity for applications such as missile plume detection and threat warning. Compared to the photomultiplier tubes (PMTs) prevalent in current missile warning systems, the NW detector arrays are expected to exhibit low noise, extended lifetimes, and low power requirements for UV detector applications.

  5. MOCVD-growth of thin zinc oxide films from zinc acetylacetonate and air

    NASA Astrophysics Data System (ADS)

    Pflitsch, Christian; Nebatti, Abdelkader; Brors, Georg; Atakan, Burak

    2012-06-01

    The metalorganic chemical vapour deposition (MOCVD) of thin zinc oxide films on borosilicate glass and silicon substrates in a hot-wall CVD-reactor (HWR) was studied. Zinc acetylacetonate (Zn(acac)2) and air were used as precursors. The aim of this work was to optimize the deposition parameters, such as pressure and deposition temperature, with respect to the film quality, structure, and homogeneity. Most experiments were performed at atmospheric pressure; this approach avoids the usage of an expensive vacuum system. It turned out that polycrystalline zinc oxide is grown at deposition temperatures above 613 K. Above 823 K, they additionally are c-axis orientated. At atmospheric pressure and lower temperature (<773 K) the film deposition is homogeneously over the whole tube furnace while at higher temperature inhomogeneous film growth and particle formation are observed, indicating a shift of the growth mechanism to the diffusion controlled regime. Although the homogeneity is improved by using higher flow velocities at atmospheric pressure, particle growth cannot be suppressed. Only at reduced pressure, which was 200 mbar in the present case, the deposition at 823 K is kinetically controlled and without particle formation, resulting in the homogeneous growth of well adhering ZnO films with c-axis orientation.

  6. Studies on the effect of ammonia flow rate induced defects in gallium nitride grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Suresh, S.; Lourdudoss, S.; Landgren, G.; Baskar, K.

    2010-10-01

    Gallium nitride (GaN) epitaxial layers were grown with different V/III ratios by varying the ammonia (NH 3) flow rate, keeping the flow rate of the other precursor, trimethylgallium (TMG), constant, in an MOCVD system. X-ray rocking curve widths of a (1 0 2) reflection increase with an increase in V/III ratio while the (0 0 2) rocking curve widths decrease. The dislocation density was found to increase with an increase in ammonia flow rate, as determined by hot-wet chemical etching and atomic force microscopy. 77 K photoluminescence studies show near band emission at 3.49 eV and yellow luminescence peaking at 2.2 eV. The yellow luminescence (YL) intensity decreases with an increase in V/III ratio. Positron annihilation spectroscopy studies show that the concentration of Ga-like vacancies increases with an increase in ammonia flow rate. This study confirms that the yellow luminescence in the GaN arises due to deep levels formed by gallium vacancies decorated with oxygen atoms.

  7. The controlled growth of GaN microrods on Si(111) substrates by MOCVD

    NASA Astrophysics Data System (ADS)

    Foltynski, Bartosz; Garro, Nuria; Vallo, Martin; Finken, Matthias; Giesen, Christoph; Kalisch, Holger; Vescan, Andrei; Cantarero, Andrés; Heuken, Michael

    2015-03-01

    In this paper, a selective area growth (SAG) approach for growing GaN microrods on patterned SiNx/Si(111) substrates by metal-organic chemical vapor deposition (MOCVD) is studied. The surface morphology, optical and structural properties of vertical GaN microrods terminated by pyramidal shaped facets (six { 10 1 bar 1} planes) were characterized using scanning electron microscopy (SEM), room temperature photoluminescence (PL) and Raman spectroscopy, respectively. Measurements revealed high-quality GaN microcolumns grown with silane support. Characterized structures were grown nearly strain-free (central frequency of Raman peak of 567±1 cm-1) with crystal quality comparable to bulk crystals (FWHM=4.2±1 cm-1). Such GaN microrods might be used as a next-generation device concept for solid-state lighting (SSL) applications by realizing core-shell InGaN/GaN multi-quantum wells (MQWs) on the n-GaN rod base.

  8. The APS ceramic chambers

    SciTech Connect

    Milton, S.; Warner, D.

    1994-07-01

    Ceramics chambers are used in the Advanced Photon Source (APS) machines at the locations of the pulsed kicker and bumper magnets. The ceramic will be coated internally with a resistive paste. The resistance is chosen to allow the low frequency pulsed magnet field to penetrate but not the high frequency components of the circulating beam. Another design goal was to keep the power density experienced by the resistive coating to a minimum. These ceramics, their associated hardware, the coating process, and our recent experiences with them are described.

  9. Wire chambers revisited.

    PubMed

    Ott, R J

    1993-04-01

    Detectors used for radioisotope imaging have, historically, been based on scintillating crystal/photomultiplier combinations in various forms. From the rectilinear scanner through to modern gamma cameras and positron cameras, the basic technology has remained much the same. Efforts to overcome the limitations of this form of technology have foundered on the inability to reproduce the required sensitivity, spatial resolution and sensitive area at acceptable cost. Multiwire proportional chambers (MWPCs) have long been used as position-sensitive charged particle detectors in nuclear and high-energy physics. MWPCs are large-area gas-filled ionisation chambers in which large arrays of fine wires are used to measure the position of ionisation produced in the gas by the passage of charged particles. The important properties of MWPCs are high-spatial-resolution, large-area, high-count-rate performance at low cost. For research applications, detectors several metres square have been built and small-area detectors have a charged particle resolution of 0.4 mm at a count rate of several million per second. Modification is required to MWPCs for nuclear medicine imaging. As gamma rays or X-rays cannot be detected directly, they must be converted into photo- or Compton scatter electrons. Photon-electron conversion requires the use of high atomic number materials in the body of the chamber. Pressurised xenon is the most useful form of "gas only" photon-electron convertor and has been used successfully in a gamma camera for the detection of gamma rays at energies below 100 keV. This camera has been developed specifically for high-count-rate first-pass cardiac imaging. This high-pressure xenon gas MWPC is the key to a highly competitive system which can outperform scintillator-based systems. The count rate performance is close to a million counts per second and the intrinsic spatial resolution is better than the best scintillator-based camera. The MWPC camera produces quantitative

  10. Ionization chamber dosimeter

    DOEpatents

    Renner, Tim R.; Nyman, Mark A.; Stradtner, Ronald

    1991-01-01

    A method for fabricating an ion chamber dosimeter collecting array of the type utilizing plural discrete elements formed on a uniform collecting surface which includes forming a thin insulating layer over an aperture in a frame having surfaces, forming a predetermined pattern of through holes in the layer, plating both surfaces of the layer and simultaneously tilting and rotating the frame for uniform plate-through of the holes between surfaces. Aligned masking and patterned etching of the surfaces provides interconnects between the through holes and copper leads provided to external circuitry.

  11. Peculiarities of photoluminescence of vertical n +/ n-GaAs/Al0.25Ga0.75As MBE- and MOCVD-grown structures designed for microwave detectors

    NASA Astrophysics Data System (ADS)

    Čerškus, Aurimas; Kundrotas, Jurgis; Sužiedėlis, Algirdas; Gradauskas, Jonas; Ašmontas, Steponas; Johannessen, Eric; Johannessen, Agne

    2015-09-01

    Vertical MBE- and MOCVD-grown structures used for microwave electronics have been studied with continuous wave and time-correlated single photon counting dynamic photoluminescence technique. The photoluminescence spectra and light emission lifetimes are used to explain the recombination mechanisms of the excited carriers. This paper presents results showing the differences in recombination characteristics of layers grown using MBE process compared with MOCVD process. One of these differences is that the PL spectrum of the MOCVD-grown layer is shifted towards the forbidden energy gap region, as well as the characteristic recombination time is longer than for the MBE-grown sample. This peculiarity can be attributed to the formation of the localised band tails in the MOCVD-grown sample. The proposed analytical model explains the differences in microwave detection properties of the samples grown by MBE and MOCVD processes.

  12. Diogene pictorial drift chamber

    SciTech Connect

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  13. Mush Column Magma Chambers

    NASA Astrophysics Data System (ADS)

    Marsh, B. D.

    2002-12-01

    Magma chambers are a necessary concept in understanding the chemical and physical evolution of magma. The concept may well be similar to a transfer function in circuit or time series analysis. It does what needs to be done to transform source magma into eruptible magma. In gravity and geodetic interpretations the causative body is (usually of necessity) geometrically simple and of limited vertical extent; it is clearly difficult to `see' through the uppermost manifestation of the concentrated magma. The presence of plutons in the upper crust has reinforced the view that magma chambers are large pots of magma, but as in the physical representation of a transfer function, actual magma chambers are clearly distinct from virtual magma chambers. Two key features to understanding magmatic systems are that they are vertically integrated over large distances (e.g., 30-100 km), and that all local magmatic processes are controlled by solidification fronts. Heat transfer considerations show that any viable volcanic system must be supported by a vertically extensive plumbing system. Field and geophysical studies point to a common theme of an interconnected stack of sill-like structures extending to great depth. This is a magmatic Mush Column. The large-scale (10s of km) structure resembles the vertical structure inferred at large volcanic centers like Hawaii (e.g., Ryan et al.), and the fine scale (10s to 100s of m) structure is exemplified by ophiolites and deeply eroded sill complexes like the Ferrar dolerites of the McMurdo Dry Valleys, Antarctica. The local length scales of the sill reservoirs and interconnecting conduits produce a rich spectrum of crystallization environments with distinct solidification time scales. Extensive horizontal and vertical mushy walls provide conditions conducive to specific processes of differentiation from solidification front instability to sidewall porous flow and wall rock slumping. The size, strength, and time series of eruptive behavior

  14. Microwave characterization of normal and superconducting states of MOCVD made YBCO tapes

    NASA Astrophysics Data System (ADS)

    Wosik, Jarek; Krupka, Jerzy; Qin, Kuang; Ketharnath, Dhivya; Galstyan, Eduard; Selvamanickam, Venkat

    2017-03-01

    We have used a microwave, non-contact, non-destructive, dielectric resonator (DR) technique to characterize complex conductivity of different quality YBCO/Hastelloy tapes for the purpose of exploring such a technique as a potential quality control method for fabrication of YBCO tapes. The tapes were deposited at different temperatures on Hastelloy-supported oxide buffer layers using the MOCVD technique. The buffer stack consisted of aluminum oxide (Al2O3), yttrium oxide (Y2O3), and textured ion beam assisted deposition-MgO and LaMnO3 layers. Two dielectric resonators (DRs), the single post DR, consisting of high-permittivity barium zirconium titanate ceramic operating at 13 GHz in quasi-TE01δ mode, and the rod DR, consisting of rutile single crystal disk operating at 9.4 GHz in-TE011 mode, were designed to meet sensitivity requirements for characterization of conductivity of the superconductor at normal and superconducting states, respectively. For calculations of complex conductivity from experimental data of Q-factor and resonant frequency shift, a commercial electromagnetic simulator HFSS, based on finite elements analysis, was used. The theoretical Q-factor and resonant frequency on conductivity functions obtained from full wave numerical simulations of microwave fields were matched with the experimental data to determine conductivity of the YBCO tapes in both normal and superconducting states. In addition, for comparison purposes, 280 nm thick high-quality YBCO epitaxial film deposited on a dielectric substrate was also characterized, including frequency dependence of the complex conductivity. Discussion about feasibility of using DR microwave techniques as a quality control tool via measurements of conductivity versus temperature slope of the YBCO/Hastelloy tape in normal state is included. Also, microwave conductivity values of Hastelloy substrate as a function of temperature are reported.

  15. Characterization of Defects on MOCVD Grown Gallium Nitride Using Transient Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Kasani, Sujan Phani Kumar

    Since the invention of the first visible spectrum (red) LED by Holonyak in 1962, there has been a need for more efficient, more reliable and less expensive LEDs. The III-nitrides revolutionized semiconductor technology with their applications in the blue LED's. However the internal quantum efficiency of LED's are limited by the deep level traps in GaN substrate. Traps are defects in the crystal lattice, which depends on growth parameters. These traps act as non-radiative centers where non-radiative recombination occurs without conversion of available energy into light. Characterization of these traps in a material is necessary for better understanding of the material growth quality and resulting device performance. In this work Capacitance-Voltage (C-V) and Deep Level Transient Spectroscopy (DLTS) are conducted which provide electronic properties of trap centers like activation energy, doping concentration and capture cross-section. In n-GaN grown by Metalorganic Chemical Vapor Deposition (MOCVD) on Sapphire two defects types are detected and are characterized by Capacitance-Voltage and Deep Level Transient Spectroscopy. Two deep levels E1 and E2 are typically observed in n-GaN with the activation energies of 0.21eV and 0.53eV at 125°K and 325°K, respectively. The deep level E1 is caused by linear line defects along dislocation cores while deep level E2 is related to point defects. The characterization techniques, experimental systems and preliminary characterization results are discussed in detail.

  16. Thermal annealing study of as-grown n-type MOCVD GaAs

    NASA Astrophysics Data System (ADS)

    Naz, Nazir A.; Qurashi, Umar S.; Zafar Iqbal, M.

    2007-12-01

    Results of isochronal annealing up to a temperature of 660 K of n-type GaAs grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) are reported. Deep-level transient spectroscopy (DLTS) reveals EL2 as the only electron-emitting deep-level defect in our as-grown material, whereas three hole-emitting levels at Ev+0.09 eV, Ev+0.40 eV and Ev+0.93 eV are observed in the minority-carrier injection spectra. While yielding interesting results on the behavior of these pre-existing deep-level defects, thermal annealing is found to introduce at least four new defects, three in the upper half of the band gap at Ec-0.13 eV, Ec-0.16 eV and Ec-0.36 eV, and one in the lower half at Ev+0.19 eV. Two of these defects, one at Ec-0.16 eV and the other at Ec-0.36 eV, are identified with previously reported annealed-in deep levels in n-GaAs, while the other two defects cannot be identified with any of the deep levels reported in the literature. Data on the annealing behavior and other characteristics of these annealed-in levels are presented. All the pre-existing inadvertent deep-level defects in the as-grown material were found to be stable up to 600 K, beyond which the minority-carrier emitting levels start to anneal out, but EL2 tends to show a slight increase with annealing temperature.

  17. Doubly charged state of EL2 defect in MOCVD-grown GaAs

    NASA Astrophysics Data System (ADS)

    Naz, Nazir A.; Qurashi, Umar S.; Majid, Abdul; Zafar Iqbal, M.

    2007-12-01

    EL2 is the ubiquitous native defect in crystalline GaAs grown by a variety of different techniques. It has been proposed to be a doubly charged deep-level center with two states having distinct energy levels in the band gap. While the singly charged state has been the subject of many experimental studies and is, therefore, well established, the doubly charged state has only been occasionally alluded to in the literature. This paper provides evidence for a dominant inadvertent deep level in p-type GaAs most likely to be the doubly charged state of the EL2 center. Deep-level transient spectroscopy (DLTS) has been applied to characterize epitaxial layers of p-type GaAs grown on p + GaAs substrates by low-pressure metal organic chemical vapor deposition (LP-MOCVD). A pronounced peak is observed in the majority carrier (hole) emission deep-level spectra. Thermal emission rate of holes from the corresponding deep level is found to exhibit a strong electric field dependence, showing an increase of more than two orders of magnitude with an increase of the electric field by a factor of ∼2. The thermal activation energy for this level is found to vary from 0.29 to 0.61 eV as the electric field is varied from 2.8×10 5 to 1.4×10 5 V/cm. Direct pulse-filling measurements point to a temperature-dependent behavior of the hole capture cross section of this level. We identify this inadvertent deep-level defect, commonly observed in p-type GaAs grown by a variety of different methods, with the doubly charged state of the well-known As Ga antisite related defect, EL2.

  18. Optoelectronic and structural properties of InGaN nanostructures grown by plasma-assisted MOCVD

    NASA Astrophysics Data System (ADS)

    Seidlitz, Daniel; Senevirathna, M. K. I.; Abate, Y.; Hoffmann, A.; Dietz, N.

    2015-09-01

    This paper presents optoelectronic and structural layer properties of InN and InGaN epilayers grown on sapphire templates by Migration-Enhanced Plasma Assisted Metal Organic Chemical Vapor Deposition (MEPA-MOCVD). Real-time characterization techniques have been applied during the growth process to gain insight of the plasma-assisted decomposition of the nitrogen precursor and associated growth surface processes. Analyzed Plasma Emission Spectroscopy (PES) and UV Absorption Spectroscopy (UVAS) provide detection and concentrations of plasma generated active species (N*/NH*/NHx*). Various precursors have been used to assess the nitrogen-active fragments that are directed from the hollow cathode plasma tube to the growth surface. The in-situ diagnostics results are supplemented with ex-situ materials structures investigation results of nanoscale structures using Scanning Near-field Optical Microscopy (SNOM). The structural properties have been analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) reflectance. The Optoelectronic and optical properties were extracted by modeling the FTIR reflectance (e.g. free carrier concentration, high frequency dielectric constant, mobility) and optical absorption spectroscopy. The correlation and comparison between the in-situ metrology results with the ex-situ nano-structural and optoelectronic layer properties provides insides into the growth mechanism on how plasma-activated nitrogen-fragments can be utilized as nitrogen precursor for group III-nitride growth. The here assessed growth process parameter focus on the temporal precursor exposure of the growth surface, the reactor pressure, substrate temperature and their effects of the properties of the InN and InGaN epilayers.

  19. Effect of growth temperature on InGaN/GaN heterostructures grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Surender, S.; Prabakaran, K.; Loganathan, R.; Pradeep, S.; Singh, Shubra; Baskar, K.

    2017-06-01

    InGaN/GaN heterostructured samples were grown at different temperatures varying from 680 °C to 760 °C on c-plane sapphire substrates using a horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD) reactor. Systematic investigation of structural, optical, morphological and electrical properties has been carried out using High Resolution X-Ray Diffraction (HRXRD), Photoluminescence (PL), Atomic Force Microscope (AFM) and Hall Measurement respectively. From the HRXRD results, the respective Indium (In) composition in the InGaN/GaN heterostructures can be calculated using InGaN (0002) peaks. In incorporation is very much sensitive to the temperature and incorporation of In in InGaN epilayer was found to decrease with increase in growth temperature. PL spectra reveal a shift towards higher energy side because of In incorporation with increasing reactor temperature. AFM images of the sample grown at 680 °C shows the In rich clusters due to compositional inhomogeneity. With further increase in the growth temperature, decomposition of InN starts and hence decreases the surface roughness. Hall Effect studies confirm that with increasing growth temperature bulk electron concentration of the InGaN thin films decrease and mobility increases. Maximum bulk electron concentration of 4.5×1019 cm-3 and a mobility of 295 cm2/V-s was obtained for 19% of In. Efforts are being made to optimize the incorporation of In content in InGaN/GaN heterostructures for photovoltaic application.

  20. MOCVD growth and characterization of ZnO nanowire arrays for advanced ultraviolet detectors

    NASA Astrophysics Data System (ADS)

    Rivera, Abdiel; Zeller, John; Manzur, Tariq; Sood, Ashok; Anwar, Mehdi

    2012-10-01

    Zinc oxide (ZnO) provides a unique wide bandgap biocompatible material system exhibiting both semiconducting and piezoelectric properties, and is a versatile functional material that has a diverse group of growth morphologies. Bulk ZnO has a bandgap of 3.37 eV that corresponds to emissions in the solar blind ultraviolet (UV) spectral band (240-280 nm). We have grown highly ordered vertical arrays of ZnO nanowires (NWs) and nanorods using a metal organic chemical vapor deposition (MOCVD) growth process on Si(111), SiO2, and sapphire substrates. The structural and optical properties of the grown vertically aligned ZnO nanostructure arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. The unique diffraction pattern for ZnO(002) concurred with the SEM inspection indicating vertical orientation of the NWs and nanorods. UV detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity for applications such as missile plume detection and threat warning. An analytical model that can predict sensor performance with and without gain for a desired UV band of interest has also been developed that has the potential for substantial improvements in sensor performance and reduction in size for a variety of threat warning applications. In addition, testing and characterization of photomultiplier tubes (PMTs) exposed to eight individual UV LEDs having peak wavelengths ranging from 248 nm to 370 nm has been performed to provide a relative UV detection performance benchmark. Compared to PMTs, the NW arrays are expected to exhibit low noise, extended lifetimes, high quantum efficiency, and very low power requirements.

  1. Fabrication of InGaN quantum dots by periodically interrupted growth in MOCVD

    NASA Astrophysics Data System (ADS)

    Choi, Seung-Kyu; Jang, Jae-Min; Yi, Sung-Hak; Kim, Jung-A.; Jung, Woo-Gwang

    2008-03-01

    Self-assembled InGaN quantum dots are fabricated in a two-flow horizontal MOCVD reactor maintained at the pressure of 200 torr. The precursors were trimethyl-gallium (TMG) and trimethyl-indium (TMI) and ammonia (NH 3), and the carrier gas was N II and H II. The optimum condition for periodically interrupted growth (PIG) mode was deduced to fabricate the InGaN quantum dots. NH 3 was supplied in PIG mode with the interval of 3 seconds and 5 seconds while TMG and TMI were supplied continuously. The carrier gas was N II in QDs growth, while H II in nucleation and buffer layer growth. The influence of number of periodic interrupted NH 3 on the structural and optical properties of InGaN quantum dots was investigated by AFM, FE-SEM and low temperature photoluminescence (LT-PL). The AFM images give the size of InGaN QDs with diameter of 20 ~ 50 nm, height of 3 ~ 10 nm and density of 10 10 #/cm2 ~ 10 11 #/cm2. A strong peak at 362.2 nm (3.41eV) and broad emission peak in 435 nm (2.86 eV) were evolved in the photoluminescence measurement using Nd-YAG laser. The composition of QDs was estimated to be In 0.14Ga 0.86N from the relation between peak energy and indium content. Hence. The periodic interruption growth enables the fabrication of self- assembled InGaN QDs with high density and uniform size.

  2. Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

    SciTech Connect

    Gaubas, E. Čeponis, T.; Jasiunas, A.; Jelmakas, E.; Juršėnas, S.; Kadys, A.; Malinauskas, T.; Tekorius, A.; Vitta, P.

    2013-11-15

    The MOCVD grown GaN epi-layers of different thickness have been examined in order to clarify a role of surface recombination, to separate an impact of radiative and non-radiative recombination and disorder factors. The microwave probed –photoconductivity (MW-PC) and spectrally resolved photo-luminescence (PL) transients were simultaneously recorded under ultraviolet (UV) light 354 nm pulsed 500 ps excitation. The MW-PC transients exhibited the carrier decay components associated with carrier decay within micro-crystals and the disordered structure on the periphery areas surrounding crystalline columns. Three PL bands were resolved within PL spectrum, namely, the exciton ascribed UV-PL band edge for hν>3.3 eV, blue B-PL band for 2.5 < hν < 3.0 eV and yellow Y-PL band with hν < 2.4 eV. It has been obtained that intensity of UV-PL band increases with excitation density, while intensity of B-PL band is nearly invariant. However, intensity of the Y-PL increases with reduction of the excitation density. The Y-PL can be associated with trapping centers. A reduction of UV excitation density leads to a decrease of the relative amplitude of the asymptotic component within the MW-PC transients and to an increase of the amplitude as well as duration of the yellow spectral band (Y-PL) asymptotic component. Fractional index α with values 0.5 < α < 0.8 was evaluated for the stretched-exponent component which fits the experimental transients determined by the disordered structure ascribed to the periphery areas surrounding the crystalline columns.

  3. HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF PLENUM WITH ATTACHED DRAFT REGULATOR. - Hot Springs National Park, Bathhouse Row, Superior Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

  4. Small rocket flowfield diagnostic chambers

    NASA Technical Reports Server (NTRS)

    Morren, Sybil; Reed, Brian

    1993-01-01

    Instrumented and optically-accessible rocket chambers are being developed to be used for diagnostics of small rocket (less than 440 N thrust level) flowfields. These chambers are being tested to gather local fluid dynamic and thermodynamic flowfield data over a range of test conditions. This flowfield database is being used to better understand mixing and heat transfer phenomena in small rockets, influence the numerical modeling of small rocket flowfields, and characterize small rocket components. The diagnostic chamber designs include: a chamber design for gathering wall temperature profiles to be used as boundary conditions in a finite element heat flux model; a chamber design for gathering inner wall temperature and static pressure profiles; and optically-accessible chamber designs, to be used with a suite of laser-based diagnostics for gathering local species concentration, temperature, density, and velocity profiles. These chambers were run with gaseous hydrogen/gaseous oxygen (GH2/GO2) propellants, while subsequent versions will be run on liquid oxygen/hydrocarbon (LOX/HC) propellants. The purpose, design, and initial test results of these small rocket flowfield diagnostic chambers are summarized.

  5. LRL 25-inch Bubble Chamber

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Gow, J. D.; Barrera, F.; Eckman, G.; Shand, J.; Watt, R.; Norgren, D.; Hernandez, H. P.

    1964-07-08

    The recently completed 25-inch hydrogen bubble chamber combines excellent picture quality with a fast operating cycle. The chamber has a unique optical system and is designed to take several pictures each Bevatron pulse, in conjunction with the Bevatron rapid beam ejection system.

  6. Fast-response cloud chamber

    NASA Technical Reports Server (NTRS)

    Fogal, G. L.

    1977-01-01

    Wall structure keeps chambers at constant, uniform temperature, yet allows them to be cooled rapidly if necessary. Wall structure, used in fast-response cloud chamber, has surface heater and coolant shell separated by foam insulation. It is lightweight and requires relatively little power.

  7. National Ignition Facility Target Chamber

    SciTech Connect

    Wavrik, R W; Cox, J R; Fleming, P J

    2000-10-05

    On June 11, 1999 the Department of Energy dedicated the single largest piece of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. The ten (10) meter diameter aluminum target high vacuum chamber will serve as the working end of the largest laser in the world. The output of 192 laser beams will converge at the precise center of the chamber. The laser beams will enter the chamber in two by two arrays to illuminate 10 millimeter long gold cylinders called hohlraums enclosing 2 millimeter capsule containing deuterium, tritium and isotopes of hydrogen. The two isotopes will fuse, thereby creating temperatures and pressures resembling those found only inside stars and in detonated nuclear weapons, but on a minute scale. The NIF Project will serve as an essential facility to insure safety and reliability of our nation's nuclear arsenal as well as demonstrating inertial fusion's contribution to creating electrical power. The paper will discuss the requirements that had to be addressed during the design, fabrication and testing of the target chamber. A team from Sandia National Laboratories (SNL) and LLNL with input from industry performed the configuration and basic design of the target chamber. The method of fabrication and construction of the aluminum target chamber was devised by Pitt-Des Moines, Inc. (PDM). PDM also participated in the design of the chamber in areas such as the Target Chamber Realignment and Adjustment System, which would allow realignment of the sphere laser beams in the event of earth settlement or movement from a seismic event. During the fabrication of the target chamber the sphericity tolerances had to be addressed for the individual plates. Procedures were developed for forming, edge preparation and welding of individual plates. Construction plans were developed to allow the field construction of the target chamber to occur parallel to other NIF construction activities. This was

  8. Ion chamber based neutron detectors

    DOEpatents

    Derzon, Mark S; Galambos, Paul C; Renzi, Ronald F

    2014-12-16

    A neutron detector with monolithically integrated readout circuitry, including: a bonded semiconductor die; an ion chamber formed in the bonded semiconductor die; a first electrode and a second electrode formed in the ion chamber; a neutron absorbing material filling the ion chamber; and the readout circuitry which is electrically coupled to the first and second electrodes. The bonded semiconductor die includes an etched semiconductor substrate bonded to an active semiconductor substrate. The readout circuitry is formed in a portion of the active semiconductor substrate. The ion chamber has a substantially planar first surface on which the first electrode is formed and a substantially planar second surface, parallel to the first surface, on which the second electrode is formed. The distance between the first electrode and the second electrode may be equal to or less than the 50% attenuation length for neutrons in the neutron absorbing material filling the ion chamber.

  9. High performance of Ga-doped ZnO transparent conductive layers using MOCVD for GaN LED applications.

    PubMed

    Horng, Ray-Hua; Shen, Kun-Ching; Yin, Chen-Yang; Huang, Chiung-Yi; Wuu, Dong-Sing

    2013-06-17

    High performance of Ga-doped ZnO (GZO) prepared using metalorganic chemical vapor deposition (MOCVD) was employed in GaN blue light-emitting diodes (LEDs) as transparent conductive layers (TCL). By the post-annealing process, the annealed 800°C GZO films exhibited a high transparency above 97% at wavelength of 450 nm. The contact resistance of GZO decreased with the annealing temperature increasing. It was attributed to the improvement of the GZO crystal quality, leading to an increase in electron concentration. It was also found that some Zn atom caused from the decomposition process diffused into the p-GaN surface of LED, which generated a stronger tunneling effect at the GZO/p-GaN interface and promoted the formation of ohmic contact. Moreover, contrast to the ITO-LED, a high light extraction efficiency of 77% was achieved in the GZO-LED at injection current of 20 mA. At 350 mA injection current, the output power of 256.51 mW of GZO-LEDs, corresponding to a 21.5% enhancement as compared to ITO-LEDs was obtained; results are promising for the development of GZO using the MOCVD technique for GaN LED applications.

  10. Role of H2 supply for Sn incorporations in MOCVD Ge1-xSnx epitaxial growth

    NASA Astrophysics Data System (ADS)

    Suda, Kohei; Sawamoto, Naomi; Machida, Hideaki; Ishikawa, Masato; Sudoh, Hiroshi; Ohshita, Yoshio; Hirosawa, Ichiro; Ogura, Atsushi

    2017-06-01

    In this paper, we propose a new method of using H2 supply in the atmosphere to increase Sn concentration in a Ge1-xSnx film epitaxially grown on a Ge substrate using MOCVD (metal organic chemical vapor deposition). H2 supplied in the atmosphere accelerates decomposition of Sn precursors and suppresses surface migration of Sn atoms during epitaxial growth of a Ge1-xSnx film. The proposed method is new and fundamentally different from the existing methods that increase Sn concentration through either crystallizing α-Ge1-xSnx or lowering growth temperature. The proposed method uses H2 supply in the atmosphere to increase Sn concentration. In order to show the effectiveness of the proposed method, we conducted experiments with varying ratios of supplying H2 in the atmosphere and epitaxially grew a Ge1-xSnx film on a Ge substrate using MOCVD. MO precursors that we used in our experiments (tertiarybutylgermane and tetraethyl tin) are new and safe. In our experiments, we observed that Sn concentration increased with H2 supply during growth, while maintaining a high growth rate of a Ge1-xSnx film.

  11. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  12. DLTS study of n-type GaN grown by MOCVD on GaN substrates

    NASA Astrophysics Data System (ADS)

    Tokuda, Y.; Matsuoka, Y.; Ueda, H.; Ishiguro, O.; Soejima, N.; Kachi, T.

    2006-10-01

    Electron traps in n-type GaN layers grown homoepitaxially by MOCVD on free-standing GaN substrates have been characterized using DLTS for vertical Schottky diodes. Two free-standing HVPE GaN substrates (A and B), obtained from two different sources, are used. The Si-doped GaN layers with the thickness of 5 μm are grown on an area of 0.9×0.9 cm 2 of substrate A and on an area of 1×1 cm 2 of substrate B. Two traps labeled B1 (Ec-0.23 eV) and B2 (Ec-0.58 eV) are observed with trap B2 dominant in GaN on both substrates. There exist no dislocation-related traps which have been previously observed in MOCVD GaN on sapphire. This might be correlated to the reduction in dislocation density due to the homoepitaxial growth. However, it is found that there is a large variation, more than an order of magnitude, in trap B2 concentration and that the B2 spatial distributions are different between the two substrates used.

  13. Electrical properties of ferroelectric-gate FETs with SrBi2Ta2O9 formed using MOCVD technique

    NASA Astrophysics Data System (ADS)

    Yan, Kang; Takahashi, Mitsue; Sakai, Shigeki

    2012-09-01

    Ferroelectric-gate field-effect transistors (FeFETs) with a Pt/SrBi2Ta2O9/Hf-Al-O/Si gate stack were fabricated using the metal-organic chemical vapor deposition (MOCVD) technique to prepare the SrBi2Ta2O9 (SBT) ferroelectric layer. A good threshold voltage ( V th) distribution was found for more than 90 n-channel FeFETs in one chip with a 170 nm SBT layer owing to the good film uniformity of the SBT layer deposited by MOCVD. The average memory window (Vw^{av}) and the standard deviations ( σ thl, σ thr) of the left- and right-side branches of the drain-gate voltage curves of the FeFETs yielded a Vw^{av}/(σ_{thl} + σ_{thr}) value of 5.45, indicating that the FeFETs can be adapted for large-scale-integration. The electric field, the energy band profile in the gate stack, and the gate leakage current were also investigated at high gate voltages. We found that the effect of Fowler-Nordheim tunneling appeared under these conditions. Because of the tunneling injection and trapping of electrons into the gate insulators, the operation voltage ranges of the FeFETs were limited by this tunneling.

  14. Growth and conduction mechanism of As-doped p-type ZnO thin films deposited by MOCVD

    SciTech Connect

    Ma, Y.; Gao, Q.; Wu, G.G.; Li, W.C.; Gao, F.B.; Yin, J.Z.; Zhang, B.L.; Du, G.T.

    2013-03-15

    Highlight: ► P-type As-doped ZnO thin films was fabricated by MOCVD after post-growth annealing. ► The formation mechanism of p-ZnO with high hole concentration above 10{sup 19} cm{sup −3} was elucidated. ► Besides As{sub Zn}–2V{sub Zn} complex, C impurities also played an important role in realizing p-ZnO. ► The formations of As{sub O} and O-C-O complex were partially contributed to the p-type ZnO: As films. - Abstract: As-doped p-type ZnO thin films were fabricated by metal organic chemical vapor deposition (MOCVD) after in situ annealing in a vacuum. The p-type conduction mechanism was suggested by the analysis of X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy. It was found that most of the As dopants in p-ZnO thin films formed As{sub Zn}–2V{sub Zn} shallow acceptor complex, simultaneously, carbon impurities also played an important role in realizing p-type conductivity in ZnO. Substitutional carbon on oxygen site created passivated defect bands by combining with Ga atoms due to the donor-acceptor pair Coulomb binding, which shifted the valence-band maximum upwards for ZnO and thus increased the hole concentration.

  15. Structural and photocatalytic properties of TiO2 films fabricated on silicon substrates by MOCVD method.

    PubMed

    Yang, Jia-long; Li, Ying; Wang, Fu; Zuo, Liang; Yi, Gu-Chul; Choi, Wong Yong

    2005-01-01

    Silicon ( 111) and Silicon(100) were employed for fabrication of TiO2 films by metal organic chemical vapor deposition( MOCVD). Titanium(IV) isopropoxide(Ti[O(C3H7)4] ) was used as a precursor. The as-deposited TiO2 films were characterized with FE-SEM, XRD and AFM. The photocatalytic properties were investigated by decomposition of aqueous Orange II . And UV-VIS photospectrometer was used for checking the absorption characteristics and photocatalytic degradation activity. The crystalline and structural properties of TiO2 film had crucial influences on the photodegradation efficiency. For MOCVD in-situ deposited films on Si substrates, the photoactivities varied following a shape of "M": at lower(350 degrees C ), middle(500 degrees C ) and higher(800 degrees C ) temperature of deposition, relative lower photodegradation activities were observed. At 400 degrees C and 700 degrees C of deposition, relative higher efficiencies of degradation were obtained, because one predominant crystallite orientation could be obtained as deposition at the temperature of two levels, especially a single anatase crystalline TiO2 film could be obtained at 700 degrees C.

  16. Fabrication of GdBa2Cu3O7-δ films by photo-assisted-MOCVD process

    NASA Astrophysics Data System (ADS)

    Li, Wei; Li, Guoxing; Zhang, Baolin; Chou, Penchu; Liu, Suping; Ma, Xiaoyu

    2014-06-01

    Pure GdBa2Cu3O7-δ (GdBCO) films were deposited on (1 0 0)-oriented LaAlO3 (LAO) substrates by photo-assisted metal organic chemical vapor deposition (PhA-MOCVD) technique. The effects of substrate temperature (Ts) and oxygen partial pressure (Po2) on microstructure, growth rate and superconducting critical current density (Jc) were investigated. A dense and no grain boundary visible, single-crystal-like cross-sectional morphology was observed. For the GdBCO film sample obtained at Ts of 810 °C and Po2 of 4 Torr, the full width at half-maximum were 0.08° and 0.41° for out-of-plane and in-plane orientations, respectively. Such low values were similar to that of single crystal GdBCO. Optimally processed GdBCO samples exhibited Jc of 2.5 MA/cm2 at 77 K in self-field. A relatively high growth rate of 0.104 μm/min for the GdBCO film is realized by the PhA-MOCVD technique.

  17. Influence of Mg and In on defect formation in GaN; bulk and MOCVD grown samples

    SciTech Connect

    Liliental-Weber, Z.; Benamara, M.; Jasinski, J.; Swider, W.; Washburn, J.; Grzegory, I.; Porowski, S.; Bak-Misiuk, J.; Domagala, J.; Bedair, S.; Eiting, C.J.; Dupuis, R.D.

    2000-11-22

    Transmission electron microscopy studies were applied to study GaN crystals doped with Mg. Both: bulk GaN:Mg crystals grown by a high pressure and high temperature process and those grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering (formation of polytypoids) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects with base on the basal planes and with walls inclined about 45O to these planes, empty inside (pinholes) were observed. A high concentration of these pyramidal defects was also observed in the MOCVD grown crystals. For samples grown with Mg delta doping planar defects were also observed especially at the early stages of growth followed by formation of pyramidal defects. TEM and x-ray studies of InxGa{sub 1{minus}x}N crystals for the range of 28-45% nominal In concentration shows formation of two sub-layers: strained and relaxed, with a much lower In concentration in the strained layer. Layers with the highest In concentration were fully relaxed.

  18. The growth of mid-infrared lasers and AIAs{sub x}Sb{sub 1-x} by MOCVD

    SciTech Connect

    Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R.

    1996-07-01

    We have grown AlSb and AlAs{sub x}Sb{sub 1-x} epitaxial layers by metal-organic chemical vapor deposition (MOCVD) using trimethylamine or ethyldimethylamine alane, triethylantimony and arsine. These layers were successfully doped p- or n-type using diethylzinc or tetraethyltin, respectively. We examined the growth of AlAs{sub x}Sb{sub 1-x} using temperatures of 500 to 600{degrees}C, pressures of 65 to 630 torr, V/III ratios of 1-17, and growth rates of 0.3 to 3.7 {mu}m/hour in a horizontal quartz reactor. We have also fabricated gain-guided, injection lasers using AlAs{sub x}Sb{sub 1-x} for optical confinement and a strained InAsSb/InAs multi-quantum well active region using MOCVD. In pulsed mode, the laser operated up to 210 K with an emission wavelength of 3.8-3.9 {mu}m.

  19. The high momentum spectrometer drift chambers

    NASA Astrophysics Data System (ADS)

    Abbott, D.; Baker, O. K.; Beaufait, J.; Bennett, C.; Bryant, E.; Carlini, R.; Kross, B.; McCauley, A.; Naing, W.; Shin, T.; Vulcan, W.

    1992-12-01

    The High Momentum Spectrometer in Hall C will use planar drift chambers for charged particle track reconstruction. The chambers are constructed using well understood technology and a conventional gas mixture. Two (plus one spare) drift chambers will be constructed for this spectrometers. Each chamber will contain 6 planes of readout channels. This paper describes the chamber design and gas handling system used.

  20. High-efficiency solar cells fabricated by vacuum MO-CVD

    NASA Technical Reports Server (NTRS)

    Fraas, L. M.; Cape, J. A.; Partain, L. D.; Mcleod, P. S.

    1984-01-01

    High-efficiency, monolithic, two-color, three-terminal solar cells were fabricated by a novel growth technique, vacuum metal-organic chemical vapor deposition. The technique uses the expensive metal alkyls efficiently and toxic gases sparingly. The fact that the outer chamber is constructed of nonbreakable stainless steel is an attractive safety feature associated with this deposition system.

  1. Neutron detection via bubble chambers.

    PubMed

    Jordan, D V; Ely, J H; Peurrung, A J; Bond, L J; Collar, J I; Flake, M; Knopf, M A; Pitts, W K; Shaver, M; Sonnenschein, A; Smart, J E; Todd, L C

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

  2. A high rate proportional chamber

    SciTech Connect

    Henderson, R.; Fraszer, W.; Openshaw, R.; Sheffer, G.; Salomon, M.; Dew, S.; Marans, J.; Wilson, P.

    1987-02-01

    Gas mixtures with high specific ionization allow the use of small interelectrode distances while still maintaining full efficiency. With the short electron drift distances the timing resolution is also improved. The authors have built and operated two 25 cm/sup 2/ chambers with small interelectrode distances. Also single wire detector cells have been built to test gas mixture lifetimes. Various admixtures of CF/sub 4/, DME, Isobutane, Ethane and Argon have been tested. Possible applications of such chambers are as beam profile monitors, position tagging of rare events and front end chambers in spectrometers.

  3. Vaporization chambers and associated methods

    DOEpatents

    Turner, Terry D.; Wilding, Bruce M.; McKellar, Michael G.; Shunn, Lee P.

    2017-02-21

    A vaporization chamber may include at least one conduit and a shell. The at least one conduit may have an inlet at a first end, an outlet at a second end and a flow path therebetween. The shell may surround a portion of each conduit and define a chamber surrounding the portion of each conduit. Additionally, a plurality of discrete apertures may be positioned at longitudinal intervals in a wall of each conduit, each discrete aperture of the plurality of discrete apertures sized and configured to direct a jet of fluid into each conduit from the chamber. A liquid may be vaporized by directing a first fluid comprising a liquid into the inlet at the first end of each conduit, directing jets of a second fluid into each conduit from the chamber through discrete apertures in a wall of each conduit and transferring heat from the second fluid to the first fluid.

  4. Cyclically controlled welding purge chamber

    NASA Technical Reports Server (NTRS)

    Gallagher, Robert L. (Inventor)

    1996-01-01

    An arrangement for butt-welding cylindrical sections of large, thin-wall tanks includes a rotatable mandrel with side-by-side sets of radial position adjusters. Each set of adjusters bears on one of the tank sections adjacent the seam, to prevent the sections from sagging out-of-round. The mandrel rotates relative to the welder, so that a continuous seam is formed. A purge chamber is fixed in position behind the seam at the weld head, and is flushed with inert gas. The purge chamber includes a two-sided structure which is contiguous with the cylindrical sections and a circumferential vane to form an open-ended tube-like structure, through which the radial position adjusters pass as the mandrel and cylindrical workpiece sections rotate. The tube-like structure is formed into a chamber by a plurality of movable gates which are controlled to maintain a seal while allowing adjusters to progress through the purge chamber.

  5. The multigap resistive plate chamber

    SciTech Connect

    Zeballos, E. Cerron; Crotty, I.; Hatzifotiadou, D.; Valverde, J. Lamas; Neupane, S.; Williams, M. C. S.; Zichichi, A.

    2015-02-03

    The paper describes the multigap resistive plate chamber (RPC). This is a variant of the wide gap RPC. However it has much improved time resolution, while keeping all the other advantages of the wide gap RPC design.

  6. Extra Terrestrial Environmental Chamber Design

    NASA Technical Reports Server (NTRS)

    Hughes, David W.

    2008-01-01

    A vacuum chamber designed to simulate the dusty environment on the Moon or Mars has been built for Goddard Space Flight Center. The path from concept to delivery is reviewed, with lessons learned and pitfalls highlighted along the way.

  7. IRIS Leaves Thermal Vacuum Chamber

    NASA Image and Video Library

    This video shows the transportation of the IRIS observatory from the thermal vacuum chamber back to the clean tent for final testing and preparations for delivery to the launch site at Vandenberg A...

  8. Webb Instrument Inside Test Chamber

    NASA Image and Video Library

    2011-08-18

    The Mid-Infrared Instrument, a component of NASA James Webb Space Telescope, underwent testing inside the thermal space test chamber at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space in Oxfordshire, England.

  9. Light diffusing fiber optic chamber

    DOEpatents

    Maitland, Duncan J.

    2002-01-01

    A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

  10. Compound Walls For Vacuum Chambers

    NASA Technical Reports Server (NTRS)

    Frazer, Robert E.

    1988-01-01

    Proposed compound-wall configuration enables construction of large high-vacuum chambers without having to use thick layers of expensive material to obtain necessary strength. Walls enclose chambers more than 1 m in diameter and several kilometers long. Compound wall made of strong outer layer of structural-steel culvert pipe welded to thin layer of high-quality, low-outgassing stainless steel.

  11. Magnetic and magneto-transport properties of Ga 1-xMn xN grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Yang, Xuelin; Chen, Zhitao; Wu, Jiejun; Pan, Yaobo; Zhang, Yan; Yang, Zhijian; Yu, Tongjun; Zhang, Guoyi

    2007-07-01

    The Ga 1-xMn xN epitaxial films were grown by metalorganic chemical vapor deposition (MOCVD) with tricarbonyl (methycyclopentadienyl) manganese ((MCP) 2Mn) as dopant source. Magnetic measurements indicate that the films are n-type conductivity ( x=0.01), ferromagnetic ordering with Curie temperature above room temperature. The magnetic moment per Mn atom decreases when the Mn concentration changes from 0.01 to 0.03. Magneto-transport properties were performed in the temperature range of 2-300 K. The magneto-resistance (MR) changes from negative effect to positive effect with increasing temperature. The negative MR effect at low temperature is due to the reduction of the magnetic scattering of the Mn ions under the applied magnetic field. Furthermore, the zero-field-cooled (ZFC)/field-cooled (FC) and MR behavior at low temperature confirm that the ferromagnetism and paramagnetism coexist in Ga 1-xMn xN films.

  12. Driving Down HB-LED Costs. Implementation of Process Simulation Tools and Temperature Control Methods of High Yield MOCVD Growth

    SciTech Connect

    Quinn, William

    2012-04-30

    The overall objective of this multi-faceted program is to develop epitaxial growth systems that meet a goal of 75% (4X) cost reduction in the epitaxy phase of HB-LED manufacture. A 75% reduction in yielded epitaxy cost is necessary in order to achieve the cost goals for widespread penetration of HB-LED's into back-lighting units (BLU) for LCD panels and ultimately for solid-state lighting (SSL). To do this, the program will address significant improvements in overall equipment Cost of Ownership, or CoO. CoO is a model that includes all costs associated with the epitaxy portion of production. These aspects include cost of yield, capital cost, operational costs, and maintenance costs. We divide the program into three phases where later phases will incorporate the gains of prior phases. Phase one activities are enabling technologies. In collaboration with Sandia National Laboratories we develop a Fluent-compatible chemistry predictive model and a set of mid-infrared and near-ultraviolet pyrometer monitoring tools. Where previously the modeling of the reactor dynamics were studied within FLUENT alone, here, FLUENT and Chemkin are integrated into a comprehensive model of fluid dynamics and the most advanced transport equations developed for Chemkin. Specifically, the Chemkin model offered the key reaction terms for gas-phase nucleation, a key consideration in the optimization of the MOCVD process. This new predictive model is used to design new MOCVD reactors with optimized growth conditions and the newly developed pyrometers are used monitor and control the MOCVD process temperature to within 0.5°C run-to-run and within each wafer. This portion of the grant is in collaboration with partners at Sandia National Laboratories. Phase two activities are continuous improvement projects which extend the current reactor platform along the lines of improved operational efficiency, improved systems control for throughput, and carrier modifications for increased yield

  13. Adsorbed Molecules and Surface Treatment Effect on Optical Properties of ZnO Nanowires Grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jabri, S.; Souissi, H.; Sallet, V.; Lusson, A.; Meftah, A.; Galtier, P.; Oueslati, M.

    2017-07-01

    We have investigated the optical properties of ZnO nanowires grown by metalorganic chemical vapor deposition (MOCVD) with nitrous oxide (N2O) as oxygen precursor. Photoluminescence (PL) and Raman measurements showed the influence of adsorbed molecules on the optical properties. Low-temperature (4 K) PL studies on the surface exciton (SX) at 3.3660 eV elucidated the nature and origin of this emission. In particular, surface treatment by annealing at high temperature under inert gas reduced the emission intensity of SX. Raman vibrational spectra proved that presence of a considerable amount of adsorbed molecules on the surface of ZnO nanowires plays a key role in the occurrence of surface excitons.

  14. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    DOE PAGES

    Mbamara, U. S.; Olofinjana, B.; Ajayi, O. O.; ...

    2016-02-01

    Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS) and X-ray Diffraction (XRD). The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-facemore » surfaces were examined to assess the wear dimension and failure mechanism. In conclusion, both friction behavior and wear (in the ball counter-face) were observed to be dependent on the crystallinity and thickness of the thin film coatings.« less

  15. DLTS and MCTS analysis of the influence of growth pressure on trap generation in MOCVD GaN

    NASA Astrophysics Data System (ADS)

    Shah, P. B.; Dedhia, R. H.; Tompkins, R. P.; Viveiros, E. A.; Jones, K. A.

    2012-12-01

    We demonstrate with DLTS and MCTS how changing growth pressure during MOCVD growth of GaN affects the majority and minority carrier trap signatures. Results indicate which specific traps are most strongly connected with the increased carbon concentration that lower growth pressure has led to. Carbon concentration is also verified with SIMS measurements. DLTS and MCTS measurements, related to carrier thermalization from traps, made up to a temperature of 450 K have found four majority carrier and two minority carrier traps. Using a lower growth pressures, at which greater incorporation of carbon is possible, has lead to larger concentrations of most of the traps; just as others have observed. However, the trap at EC - 0.48 eV is the least affected by the growth pressure. We relate all the traps found from DLTS and MCTS to those identified by others and mention the constituent atoms that the research community identifies with these traps.

  16. The anti-surfactant effect of silane on the facets-controlled growth of GaN nanorods by MOCVD

    NASA Astrophysics Data System (ADS)

    Li, J. Z.; Chen, Z. Z.; Li, S. F.; Jiao, Q. Q.; Feng, Y. L.; Jiang, S. X.; Chen, Y. F.; Yu, T. J.; Shen, B.; Zhang, G. Y.

    2016-08-01

    N-polar GaN nanorods were selective area grown by continuous mode metalorganic chemical vapor deposition (MOCVD) under a Ga-rich and high silane flow condition. The interruption comparing with continuous supply of silane flow was performed to study the role of silane flux. High resolution scanning electron microscopy (SEM), x-ray diffraction (XRD), cathodoluminescence (CL) and x-ray photoelectron spectroscopy (XPS) measurements were performed. The enhanced vertical growth rate was achieved as 42 μm/h and sharp smooth m-plane, r-plane and c-plane facets were obtained for the nanorods with high silane flux. Sisbnd N bonds were clarified to be formed on the surface of the nanorod by XPS spectra. The silane acting as anti-surfactant was suggested to explain the diffusion and incorporation of the species on the facets of GaN nanorods.

  17. Initial stages of TiO 2 thin films MOCVD growth studied by in situ surface analyses

    NASA Astrophysics Data System (ADS)

    Brevet, A.; Peterlé, P. M.; Imhoff, L.; Marco de Lucas, M. C.; Bourgeois, S.

    2005-02-01

    In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS) were performed to understand the initial stages of TiO 2 thin-film MOCVD growth. Deposits on Si (1 0 0), a few nanometres thick, were obtained at a fixed temperature of 650 °C and for two different pressures, 2.9 and 0.05 mbar, using titanium tetraisopropoxide (TTIP) as precursor. Pressure lowering led to a higher deposit growth rate. Reduction of titanium with respect to stoichiometric titanium dioxide and oxidation of the wet-cleaned silicon substrate are observed from decomposition of the Ti 2p and Si 2p peaks. The formation of a TiSi xO y mixed oxide is also pointed out and confirmed by the presence of a characteristic component in the O 1 s peak.

  18. Optical Properties of Novel GaN 3D Structures Grown by Metal-Organic Chemical Vapor Deposition (MOCVD)

    NASA Astrophysics Data System (ADS)

    Sacilotti, Marco; Imhoff, Luc; Dumas, Colette; Viste, Pierre; Vial, Jean-Claude; Baldeck, Patrice; Colombier, Isabelle; Donatini, Fabrice

    2004-06-01

    Optical properties of novel micrometer-size Ga and GaN three-dimensional structures obtained by the metal-organic chemical vapour deposition (MOCVD) technique are presented in this letter. These structures are obtained as metallic three dimensions (3D) micrometer-size objects on an appropriate substrate by metalorganic (TMGa) pyrolisis and then GaN transformed on annealing under NH3 atmosphere at 650-750°C. These 3D GaN structures are analysed by optical means, using two-photon excitation (800 nm) and by UV Hg lamp fluorescent spectroscopy techniques, adapted to two-optical-microscopes apparatus. Very intense and blue/yellow light emission is observed from these 3D structures under 800 nm two-photon laser excitation and under UV Hg lamp excitation.

  19. Species transport and chemical reaction in a MOCVD reactor and their influence on the GaN growth uniformity

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Fang, Haisheng; Yao, Qingxia; Yan, Han; Gan, Zhiyin

    2016-11-01

    Fluid flow, heat transfer, and species transport with chemical reactions have been investigated for gallium nitride (GaN) growth in a commercial metal-organic chemical vapor deposition (MOCVD) reactor. Both the growth rate and the growth uniformity are investigated zone by zone, as the wafers are divided into three zones/groups according to their distances to the susceptor center. The results show that species transport in the reactor is affected by the inlet conditions, i.e., the premixed or non-premixed inlet, the inlet temperature, the total gas flow rate, and the V/III component ratio, and reveal that the premixed inlet condition is preferred for uniform growth. Especially, a large total flow rate or a low V/III ratio results in both increase of the growth rate and improvement of the growth uniformity.

  20. Resistive switching phenomena of HfO2 films grown by MOCVD for resistive switching memory devices

    NASA Astrophysics Data System (ADS)

    Kim, Hee-Dong; Yun, Min Ju; Kim, Sungho

    2016-08-01

    The resistive switching phenomena of HfO2 films grown by using metal organic chemical vapor deposition (MOCVD) was studied for the application of resistive random access memory (ReRAM) devices. In the fabricated Pt/HfO2/TiN memory cells, bipolar resistive switching characteristics were observed, and the set and reset states were measured to be as low as 7 μA and 4 μA, respectively, at V READ = 1 V. Regarding the resistive switching performance, stable resistive switching (RS) performance was observed under 40 repetitive dc cycles with small variations of set/reset voltages and the currents and good retention characteristics of over 105 s in both the low-resistance state (LRS) and the high-resistance state (HRS). These results show the possibility of using MOCVDgrown HfO2 films as a promising resistive switching materials for ReRAM applications.

  1. High Brightness InGaN/GaN Blue Light Emitting Diode Realized by a 6× 2'' MOCVD System

    NASA Astrophysics Data System (ADS)

    Ju, Jin-Woo; Lee, Cheul-Ro; Baek, Jong-Hyeob; Lee, Young Hee; Lee, In-Hwan

    2005-04-01

    We have fabricated high brightness blue light emitting diode (LED) with InGaN/GaN multi-quantum well (MQW) which is sandwiched simply between n-GaN and p-GaN. The LED epitaxial structure was grown by a newly designed metal organic chemical vapor deposition (MOCVD) system with RF heater and vertical gas injection type showerhead. The reactor exhibited a good uniformity of temperature and gas velocity. The uniformity of layer thickness and PL wavelength was less 2% and 1.2 nm, respectively. The epoxy molded LED lamp showed radiant power of 4 mW at a forward current of 20 mA. We note that the power is very high considering such a simple LED structure.

  2. Effect of 100 MeV Ni9+ ion irradiation on MOCVD grown n-GaN

    NASA Astrophysics Data System (ADS)

    Suresh Kumar, V.; Kumar, J.; Puviarasu, P.; Munawar Basha, S.; Kanjilal, D.; Asokan, K.

    2011-11-01

    Metal-organic chemical vapor deposition (MOCVD) grown n-type Gallium nitride (GaN) has been irradiated with 100 MeV Ni9+ ions at room temperature. Atomic force microscopy (AFM) images show the nano-clusters' formation upon irradiation and the irradiated GaN surface roughness increases with the increasing ion fluences. High-resolution X-ray diffraction (HR-XRD) analysis reveals the formation of Ga2O3 due to the interface mixing of GaN/Al2O3 upon irradiation. FWHM values of GaN (0 0 0 2) increases due to the lattice disorder. Photoluminescence studies show reduced band edge emission and yellow luminescence (YL) intensity with the increasing ion fluences. Change in the band gap energy between 3.38 and 3.04 eV was measured by UV-visible optical absorption spectrum on increasing the ion fluences.

  3. In situ pre-growth calibration using reflectance as a control strategy for MOCVD fabrication of device structures

    SciTech Connect

    Breiland, W.G.; Hou, H.Q.; Chui, H.C.; Hammons, B.E.

    1996-08-01

    In situ normal incidence reflectance, combined with a virtual interface model, is being used routinely on a commercial MOCVD reactor to measure growth rates of compound semiconductor films. The technique serves as a pre-growth calibration tool analogous to the use of RHEED in MBE as well as a real-time monitor throughout the run. An application of the method to the growth of a vertical cavity surface emitting laser (VCSEL) device structure is presented. All necessary calibration information can be obtained using a single run lasting less than one hour. Working VCSEL devices are obtained on the first try after calibration. Repeated runs have yielded {+-} 0.3% reproducibility of the Fabry-Perot cavity wavelength over the course of more than 100 runs.

  4. Controlled low Si doping and high breakdown voltages in GaN on sapphire grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Agarwal, Anchal; Gupta, Chirag; Enatsu, Yuuki; Keller, Stacia; Mishra, Umesh

    2016-12-01

    Controlled n-type doping down to 2 × 1015 cm-3 was achieved in GaN grown on sapphire by MOCVD by balancing the n-type Si doping with respect to the background carbon and oxygen levels. A dopant level of ˜1 × 1016 cm-3 displayed a very high mobility of 899 cm2 V-1 s-1. High electron mobility in the drift layer leads to a low on resistance and high current densities without compromising on any other properties of the device. Schottky diodes processed on these low n-type layers showed low R on values, while the p-n diodes display high reverse breakdown voltages in excess of 1000 V for 8 μm thick drift layers with a doping of 2 × 1015 cm-3.

  5. 63. Interior view, kitchen chamber, north elevation. The kitchen chamber ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. Interior view, kitchen chamber, north elevation. The kitchen chamber was completed in the first stages of phase III construction. The paneled wall to the fireplace's right displays a phase III molding profile. The mark between the cabinet doors and on the large lower panel indicates the former position of a partition wall. The chimney-breast paneling bears a phase I profile and might have been moved to the room when the fireplace mass in the hall was reduced. - John Bartram House & Garden, House, 54th Street & Lindbergh Boulevard, Philadelphia, Philadelphia County, PA

  6. Emulsion Chamber Technology Experiment (ECT)

    NASA Technical Reports Server (NTRS)

    Gregory, John C.; Takahashi, Yoshiyuki

    1996-01-01

    The experimental objective of Emulsion Chamber Technology (ECT) was to develop space-borne emulsion chamber technology so that cosmic rays and nuclear interactions may subsequently be studied at extremely high energies with long exposures in space. A small emulsion chamber was built and flown on flight STS-62 of the Columbia in March 1994. Analysis of the several hundred layers of radiation-sensitive material has shown excellent post-flight condition and suitability for cosmic ray physics analysis at much longer exposures. Temperature control of the stack was 20 +/-1 C throughout the active control period and no significant deviations of temperature or pressure in the chamber were observed over the entire mission operations period. The unfortunate flight attitude of the orbiter (almost 90% Earth viewing) prevented any significant number of heavy particles (Z greater than or equal to 10) reaching the stack and the inverted flow of shower particles in the calorimeter has not allowed evaluation of absolute primary cosmic ray-detection efficiency nor of the practical time limits of useful exposure of these calorimeters in space to the level of detail originally planned. Nevertheless, analysis of the observed backgrounds and quality of the processed photographic and plastic materials after the flight show that productive exposures of emulsion chambers are feasible in low orbit for periods of up to one year or longer. The engineering approaches taken in the ECT program were proven effective and no major environmental obstacles to prolonged flight are evident.

  7. Plasma chemistry in wire chambers

    SciTech Connect

    Wise, J.

    1990-05-01

    The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

  8. Neutron Detection via Bubble Chambers

    SciTech Connect

    Jordan, David V.; Ely, James H.; Peurrung, Anthony J.; Bond, Leonard J.; Collar, J. I.; Flake, Matthew; Knopf, Michael A.; Pitts, W. K.; Shaver, Mark W.; Sonnenschein, Andrew; Smart, John E.; Todd, Lindsay C.

    2005-10-06

    The results of a Pacific Northwest National Laboratory (PNNL) exploratory research project investigating the feasibility of fast neutron detection using a suitably prepared and operated, pressure-cycled bubble chamber are described. The research was conducted along two parallel paths. Experiments with a slow pressure-release Halon chamber at the Enrico Fermi Institute at the University of Chicago showed clear bubble nucleation sensitivity to an AmBe neutron source and insensitivity to the 662 keV gammas from a 137Cs source. Bubble formation was documented via high-speed (1000 frames/sec) photography, and the acoustic signature of bubble formation was detected using a piezo-electric transducer element mounted on the base of the chamber. The chamber’s neutron sensitivity as a function of working fluid temperature was mapped out. The second research path consisted of the design, fabrication, and testing of a fast pressure-release Freon-134a chamber at PNNL. The project concluded with successful demonstrations of the PNNL chamber’s AmBe neutron source sensitivity and 137Cs gamma insensitivity. The source response tests of the PNNL chamber were documented with high-speed photography.

  9. Plant growth chamber M design

    NASA Technical Reports Server (NTRS)

    Prince, R. P.; Knott, W. M.

    1986-01-01

    Crop production is just one of the many processes involved in establishing long term survival of man in space. The benefits of integrating higher plants into the overall plan was recognized early by NASA through the Closed Ecological Life Support System (CELSS) program. The first step is to design, construct, and operate a sealed (gas, liquid, and solid) plant growth chamber. A 3.6 m diameter by 6.7 m high closed cylinder (previously used as a hypobaric vessel during the Mercury program) is being modified for this purpose. The chamber is mounted on legs with the central axis vertical. Entrance to the chamber is through an airlock. This chamber will be devoted entirely to higher plant experimentation. Any waste treatment, food processing or product storage studies will be carried on outside of this chamber. Its primary purpose is to provide input and output data on solids, liquids, and gases for single crop species and multiple species production using different nutrient delivery systems.

  10. Iridium-Coated Rhenium Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

    1994-01-01

    Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

  11. Iridium-Coated Rhenium Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

    1994-01-01

    Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

  12. Holography in small bubble chambers

    SciTech Connect

    Lecoq, P.

    1984-01-01

    This chapter reports on an experiment to determine the total charm cross section at different incident momenta using the small, heavy liquid bubble chamber HOBC. Holography in liquid hydrogen is also tested using the holographic lexan bubble chamber HOLEBC with the aim of preparing a future holographic experiment in hydrogen. The high intensity tests show that more than 100 incident tracks per hologram do not cause a dramatic effect on the picture quality. Hydrogen is more favorable than freon as the bubble growth is much slower in hydrogen. An advantage of holography is to have the maximum resolution in the full volume of the bubble chamber, which allows a gain in sensitivity by a factor of 10 compared to classical optics as 100 tracks per hologram look reasonable. Holograms are not more difficult to analyze than classical optics high-resolution pictures. The results show that holography is a very powerful technique which can be used in very high resolution particle physics experiments.

  13. The CLAS drift chamber system

    SciTech Connect

    Mestayer, M.D.; Carman, D.S.; Asavaphibhop, B.

    1999-04-01

    Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on a toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.

  14. Hydrostatic Hyperbaric Chamber Ventilation System

    NASA Technical Reports Server (NTRS)

    Sargusingh, Miriam M.

    2011-01-01

    The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications, including the treatment of medical conditions. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy available in the developing world for the treatment of a variety of medical conditions. Specifically, hyperbaric oxygen therapy is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. Hyperbaric oxygen therapy is simply too expensive and too dangerous to implement in the developing world using standard equipment. The hydrostatic hyperbaric chamber technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system that will provide controlled pressurization of the system, and provide adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the

  15. Annular-Cross-Section CFE Chamber

    NASA Technical Reports Server (NTRS)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.

  16. Annular-Cross-Section CFE Chamber

    NASA Technical Reports Server (NTRS)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.

  17. Double window viewing chamber assembly

    NASA Technical Reports Server (NTRS)

    Keller, V. W. (Inventor); Owen, R. B. (Inventor); Elkins, B. R. (Inventor); White, W. T. (Inventor)

    1986-01-01

    A viewing chamber which permits observation of a sample retained therein includes a pair of double window assemblies mounted in opposed openings in the walls thereof so that a light beam can directly enter and exit from the chamber. A flexible mounting arrangement for the outer windows of the window assemblies enables the windows to be brought into proper alignment. An electrical heating arrangement prevents fogging of the outer windows whereas desiccated air in the volume between the outer and inner windows prevents fogging of the latter.

  18. Test chamber for alpha spectrometry

    DOEpatents

    Larsen, Robert P.

    1977-01-01

    Alpha emitters for low-level radiochemical analysis by measurement of alpha spectra are positioned precisely with respect to the location of a surface-barrier detector by means of a chamber having a removable threaded planchet holder. A pedestal on the planchet holder holds a specimen in fixed engagement close to the detector. Insertion of the planchet holder establishes an O-ring seal that permits the chamber to be pumped to a desired vacuum. The detector is protected against accidental contact and resulting damage.

  19. CHAMBERS FERRY ROADLESS AREA, TEXAS.

    USGS Publications Warehouse

    Houser, B.B.; Ryan, George S.

    1984-01-01

    A geologic and geochemical investigation of the Chambers Ferry Roadless Area, Texas was conducted. The area has probable mineral-resource potential for oil and gas and for lignite. No metallic or additional energy resources were identified in the investigation. Detailed analyses of well logs from the vicinity of the Chambers Ferry Roadless Area, in conjunction with seismic data, are necessary to determine if the subsurface stratigraphy and structure are favorable for the accumulation of oil and gas. A shallow drilling program involving coring on a close-space grid is necessary for determination of the rank and continuity of seams of lignitic sediments in the area.

  20. Comparative study of deep levels in HVPE and MOCVD GaN by combining O-DLTS and pulsed photo-ionization spectroscopy

    NASA Astrophysics Data System (ADS)

    Pavlov, J.; Čeponis, T.; Gaubas, E.; Meskauskaite, D.; Reklaitis, I.; Vaitkus, J.; Grigonis, R.; Sirutkaitis, V.

    2015-12-01

    Operational characteristics of sensors made of GaN significantly depend on technologically introduced defects acting as rapid traps of excess carriers which reduce charge collection efficiency of detectors. In order to reveal the prevailing defects in HVPE and MOCVD grown GaN, the carrier lifetime and photo-ionization spectra have been simultaneously measured by using microwave probed photo-conductivity transient technique. Several traps ascribed to impurities as well as vacancy and anti-site type defects have been identified in HVPE GaN material samples by combining photo-ionization and electron spin resonance spectroscopy. The optical deep level transient spectroscopy technique has been applied for spectroscopy of the parameters of thermal emission from the traps ascribed to technological defects in the Schottky barrier terrace structures fabricated on MOCVD GaN.

  1. Monolithic Integration of Sampled Grating DBR with Electroabsorption Modulator by Combining Selective-Area-Growth MOCVD and Quantum-Well Intermixing

    NASA Astrophysics Data System (ADS)

    Liu, Hong-Bo; Zhao, Ling-Juan; Pan, Jiao-Qing; Zhu, Hong-Liang; Zhou, Fan; Wang, Bao-Jun; Wang, Wei

    2008-10-01

    We present the monolithic integration of a sampled-grating distributed Bragg reflector (SG-DBR) laser with a quantum-well electroabsorption modulator (QW-EAM) by combining ultra-low-pressure (55mbar) selective-area-growth (SAG) metal-organic chemical vapour deposition (MOCVD) and quantum-well intermixing (QWI) for the first time. The QW-EAM and the gain section can be grown simultaneously by using SAG MOCVD technology. Meanwhile, the QWI technology offers an abrupt band-gap change between two functional sections, which reduces internal absorption loss. The experimental results show that the threshold current Ith = 62 mA, and output power reaches 3.6mW. The wavelength tuning range covers 30nm, and all the corresponding side mode suppression ratios are over 30 dB. The extinction ratios at available wavelength channels can reach more than 14 dB with bias of -5 V.

  2. DC and High Frequency Characterization of Metalorganic Chemical Vapor Deposition (MOCVD) Grown InP/InGaAs PNP Heterojunction Bipolar Transistor

    NASA Astrophysics Data System (ADS)

    Cui, Delong; Hsu, Shawn S. H.; Pavlidis, Dimitris

    2002-02-01

    InP/InGaAs PNP heterojunction bipolar transistor (HBT) layers have been grown by metalorganic chemical vapor deposition (MOCVD) and devices have been fabricated using a self-aligned processing technology. A zinc-doped InP layer has been employed as the wide-bandgap emitter layer for the PNP HBT. The base layer used a 500 Å thick n-type InGaAs layer doped at 5× 1018 cm-3. Successful high frequency operation of these devices has been demonstrated. A single-emitter 1× 20 μm2 MOCVD-grown PNP InP/InGaAs HBT achieved current gain cutoff frequency (fT) of more than 11 GHz at a current density (JC) of 8.25× 104 A/cm2.

  3. Growth of isolated InAs quantum dots on core-shell GaAs/InP nanowire sidewalls by MOCVD

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Tang, Fengling; Wu, Yao; Li, Bang; Zhang, Xia; Ren, Xiaomin

    2017-06-01

    We demonstrate the growth of isolated InAs quantum dots on the sidewalls of core-shell GaAs/InP nanowires based on the vapor-liquid-solid MOCVD method. The quantum dots are grown under the Stranski-Krastanov mode and exhibit defect-free zinc blende structure. Discrete sharp emission peaks are observed in the range of 1.37-1.39 eV, with linewidths ranging from several hundred μeV to 1 meV or more. Excitonic and biexcitonic emissions are observed, exhibiting different power-dependent intensity and linewidth behavior. This work may open a way for the fabrication of single photon devices based on the vapor-liquid-solid MOCVD method.

  4. Lightweight Chambers for Thrust Assemblies

    NASA Technical Reports Server (NTRS)

    Elam, Sandra K.; Lee, Jonathan; Holmes, Richard; Zimmerman, Frank; Effinger, Mike; Turner, James E. (Technical Monitor)

    2001-01-01

    The Marshall Space Flight Center (MSFC) of the National Aeronautics and Space Administration (NASA) has successfully applied new materials and fabrication techniques to create actively cooled thrust chambers that operate 200-400 degrees hotter and weigh 50% lighter than conventional designs. In some vehicles, thrust assemblies account for as much as 20% of the engine weight. So, reducing the weight of these components and increasing their operating range will benefit many engines and vehicle designs, including Reusable Launch Vehicle (RLV) concepts. Obviously, copper and steel alloys have been used successfully for many years in the chamber components of thrust assemblies. Yet, by replacing the steel alloys with Polymer Matrix Composite (PMC) and/or Metal Matrix Composite (MMC) materials, design weights can be drastically reduced. In addition, replacing the traditional copper alloys with a Ceramic Matrix Composite (CMC) or an advanced copper alloy (Cu-8Cr-4Nb, also known as GRCop-84) significantly increases allowable operating temperatures. Several small MMC and PMC demonstration chambers have recently been fabricated with promising results. Each of these designs included GRCop-84 for the cooled chamber liner. These units successfully verified that designs over 50% lighter are feasible. New fabrication processes, including advanced casting technology and a low cost vacuum plasma spray (VPS) process, were also demonstrated with these units. Hot-fire testing at MSFC is currently being conducted on the chambers to verify increased operating temperatures available with the GRCop-84 liner. Unique CMC chamber liners were also successfully fabricated and prepared for hot-fire testing. Yet, early results indicate these CMC liners need significantly more development in order to use them in required chamber designs. Based on the successful efforts with the MMC and PMC concepts, two full size "lightweight" chambers are currently being designed and fabricated for hot

  5. Lightweight Chambers for Thrust Assemblies

    NASA Technical Reports Server (NTRS)

    Elam, Sandra K.; Lee, Jonathan; Holmes, Richard; Zimmerman, Frank; Effinger, Mike; Turner, James E. (Technical Monitor)

    2001-01-01

    The Marshall Space Flight Center (MSFC) of the National Aeronautics and Space Administration (NASA) has successfully applied new materials and fabrication techniques to create actively cooled thrust chambers that operate 200-400 degrees hotter and weigh 50% lighter than conventional designs. In some vehicles, thrust assemblies account for as much as 20% of the engine weight. So, reducing the weight of these components and increasing their operating range will benefit many engines and vehicle designs, including Reusable Launch Vehicle (RLV) concepts. Obviously, copper and steel alloys have been used successfully for many years in the chamber components of thrust assemblies. Yet, by replacing the steel alloys with Polymer Matrix Composite (PMC) and/or Metal Matrix Composite (MMC) materials, design weights can be drastically reduced. In addition, replacing the traditional copper alloys with a Ceramic Matrix Composite (CMC) or an advanced copper alloy (Cu-8Cr-4Nb, also known as GRCop-84) significantly increases allowable operating temperatures. Several small MMC and PMC demonstration chambers have recently been fabricated with promising results. Each of these designs included GRCop-84 for the cooled chamber liner. These units successfully verified that designs over 50% lighter are feasible. New fabrication processes, including advanced casting technology and a low cost vacuum plasma spray (VPS) process, were also demonstrated with these units. Hot-fire testing at MSFC is currently being conducted on the chambers to verify increased operating temperatures available with the GRCop-84 liner. Unique CMC chamber liners were also successfully fabricated and prepared for hot-fire testing. Yet, early results indicate these CMC liners need significantly more development in order to use them in required chamber designs. Based on the successful efforts with the MMC and PMC concepts, two full size "lightweight" chambers are currently being designed and fabricated for hot

  6. Simulation of Layered Magma Chambers.

    ERIC Educational Resources Information Center

    Cawthorn, Richard Grant

    1991-01-01

    The principles of magma addition and liquid layering in magma chambers can be demonstrated by dissolving colored crystals. The concepts of density stratification and apparent lack of mixing of miscible liquids is convincingly illustrated with hydrous solutions at room temperature. The behavior of interstitial liquids in "cumulus" piles…

  7. Nondestructive test of regenerative chambers

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Stauffis, R.; Wood, R.

    1972-01-01

    Flat panels simulating internally cooled regenerative thrust chamber walls were fabricated by electroforming, brazing and diffusion bonding to evaluate the feasibility of nondestructive evaluation techniques to detect bonds of various strength integrities. Ultrasonics, holography, and acoustic emission were investigated and found to yield useful and informative data regarding the presence of bond defects in these structures.

  8. Simulation of Layered Magma Chambers.

    ERIC Educational Resources Information Center

    Cawthorn, Richard Grant

    1991-01-01

    The principles of magma addition and liquid layering in magma chambers can be demonstrated by dissolving colored crystals. The concepts of density stratification and apparent lack of mixing of miscible liquids is convincingly illustrated with hydrous solutions at room temperature. The behavior of interstitial liquids in "cumulus" piles…

  9. Chamber Music for Better Bands.

    ERIC Educational Resources Information Center

    Brown, Michael R.

    1998-01-01

    Considers why students should participate in a chamber music ensemble: (1) students develop a sense of collegiality and self-worth; (2) ensembles encourage practice time; and (3) ensembles provide flexible performance opportunities. Highlights the different aspects of creating an ensemble from the availability of faculty to selecting challenging…

  10. Dopant species with Al-Si and N-Si bonding in the MOCVD of AlN implementing trimethylaluminum, ammonia and silane

    NASA Astrophysics Data System (ADS)

    dos Santos, R. B.; Rivelino, R.; de Brito Mota, F.; Gueorguiev, G. K.; Kakanakova-Georgieva, A.

    2015-07-01

    We have investigated gas-phase reactions driven by silane (SiH4), which is the dopant precursor in the metalorganic chemical vapor deposition (MOCVD) of aluminum nitride (AlN) doped by silicon, with prime focus on determination of the associated energy barriers. Our theoretical strategy is based on combining density-functional methods with minimum energy path calculations. The outcome of these calculations is suggestive for kinetically plausible and chemically stable reaction species with Al-Si bonding such as (CH3)2AlSiH3 and N-Si bonding such as H2NSiH3. Within this theoretical perspective, we propose a view of these reaction species as relevant for the actual MOCVD of Si-doped AlN, which is otherwise known to be contributed by the reaction species (CH3)2AlNH2 with Al-N bonding. By reflecting on experimental evidence in the MOCVD of various doped semiconductor materials, it is anticipated that the availability of dopant species with Al-Si, and alternatively N-Si bonding near the hot deposition surface, can govern the incorporation of Si atoms, as well as other point defects, at the AlN surface.

  11. Highly conformal and high-ionic conductivity thin-film electrolyte for 3D-structured micro batteries: Characterization of LiPON film deposited by MOCVD method

    NASA Astrophysics Data System (ADS)

    Fujibayashi, Takashi; Kubota, Yusuke; Iwabuchi, Katsuhiko; Yoshii, Naoki

    2017-08-01

    This paper reports a lithium phosphorus oxynitride (LiPON) thin-film electrolyte deposited using a metalorganic-chemical vapor deposition (MOCVD) method for 3D-structured micro batteries. It is shown that the MOCVD-LiPON film has both highly-conformal step coverage on a patterned substrate with line/space=2μm/2μm and aspect ratio=1 (51±3 nm) and high-ionic conductivity for very thin films deposited at 4.7 nm/min (5.9×10-6 S/cm for 190 nm and 5.3×10-6 S/cm for 95 nm). Detailed material characterization attributes the enhancement in ionic conductivity to a decrease in nanocrystallite size and improvement in chemical-composition uniformity in the film. In addition, electrochemical characterization of an all-solid-state thin-film battery fabricated with the 190 nm-thick LiPON film (Si substrate/Ti/Pt/LiCoO2/LiPON/a-Si:H/Cu) demonstrates that the LiPON film can successfully act as the electrolyte for lithium-ion batteries. Therefore, the MOCVD-LiPON film is a promising candidate material to realize 3D-structured micro batteries in the near future.

  12. Multi-wafer growth of GaInAs photodetectors on 4" InP by MOCVD for SWIR imaging applications

    NASA Astrophysics Data System (ADS)

    Furlong, Mark J.; Mattingley, Mark; Lim, Sung Wook; Geen, Matthew; Jones, Wynne

    2014-06-01

    Photodiodes based on the GaInAs/InP material system responding in the 1.3-1.7 μm wavelength range are of interest in a wide range of applications, from optical power and channel monitors in telecommunication systems through to advanced night vision imaging using large format focal plane type detectors for defense and security applications. Here we report on our results of GaInAs PIN photo detector structures grown on 2", 3" and 4" InP substrates by low pressure Metalorganic Chemical Vapor Deposition (MOCVD) in both standard and new larger volume format reactor configurations. High quality, lattice matched InP/GaInAs epitaxial layers were grown and we demonstrate that when moving to larger platen configurations, high degree of thickness uniformity (<3%, FTIR), lattice mismatch (<0.1%, XRD) and compositional uniformity (<2 nm, PL) can be maintained. The surface quality of epitaxial wafers will be assessed by various surface analytical techniques. We also make comparisons with the performance of 2", 3" and 4" photodetector structures grown, this demonstrating that MOCVD production processes have been successfully scaled. We conclude by discussing the material requirements for large area infrared focal plane array photodetectors and describe how MOCVD growth technology will address industry's requirements for increasing device sizes with improved performance.

  13. Multi-wafer growth of GaInAs photodetectors on 4" InP by MOCVD for SWIR imaging applications

    NASA Astrophysics Data System (ADS)

    Furlong, Mark J.; Mattingley, Mark; Lim, Sung Wook; Geen, Matthew; Jones, Wynne

    2013-12-01

    Photodiodes based on the GaInAs/InP material system responding in the 1.3-1.7 μm wavelength range are of interest in a wide range of applications, from optical power and channel monitors in telecommunication systems through to advanced night vision imaging using large format focal plane type detectors for defense and security applications. Here we report on our results of GaInAs PIN photo detector structures grown on 2", 3" and 4" InP substrates by low pressure Metalorganic Chemical Vapor Deposition (MOCVD) in both standard and new larger volume format reactor configurations. High quality, lattice matched InP/GaInAs epitaxial layers were grown and we demonstrate that when moving to larger platen configurations, high degree of thickness uniformity (<3%, FTIR), lattice mismatch (<0.1%, XRD) and compositional uniformity (<2 nm, PL) can be maintained. The surface quality of epitaxial wafers will be assessed by various surface analytical techniques. We also make comparisons with the performance of 2", 3" and 4" photodetector structures grown, this demonstrating that MOCVD production processes have been successfully scaled. We conclude by discussing the material requirements for large area infrared focal plane array photodetectors and describe how MOCVD growth technology will address industry's requirements for increasing device sizes with improved performance.

  14. Chamber Clearing First Principles Modeling

    SciTech Connect

    Loosmore, G

    2009-06-09

    LIFE fusion is designed to generate 37.5 MJ of energy per shot, at 13.3 Hz, for a total average fusion power of 500 MW. The energy from each shot is partitioned among neutrons ({approx}78%), x-rays ({approx}12%), and ions ({approx}10%). First wall heating is dominated by x-rays and debris because the neutron mean free path is much longer than the wall thickness. Ion implantation in the first wall also causes damage such as blistering if not prevented. To moderate the peak-pulse heating, the LIFE fusion chamber is filled with a gas (such as xenon) to reduce the peak-pulse heat load. The debris ions and majority of the x-rays stop in the gas, which re-radiates this energy over a longer timescale (allowing time for heat conduction to cool the first wall sufficiently to avoid damage). After a shot, because of the x-ray and ion deposition, the chamber fill gas is hot and turbulent and contains debris ions. The debris needs to be removed. The ions increase the gas density, may cluster or form aerosols, and can interfere with the propagation of the laser beams to the target for the next shot. Moreover, the tritium and high-Z hohlraum debris needs to be recovered for reuse. Additionally, the cryogenic target needs to survive transport through the gas mixture to the chamber center. Hence, it will be necessary to clear the chamber of the hot contaminated gas mixture and refill it with a cool, clean gas between shots. The refilling process may create density gradients that could interfere with beam propagation, so the fluid dynamics must be studied carefully. This paper describes an analytic modeling effort to study the clearing and refilling process for the LIFE fusion chamber. The models used here are derived from first principles and balances of mass and energy, with the intent of providing a first estimate of clearing rates, clearing times, fractional removal of ions, equilibrated chamber temperatures, and equilibrated ion concentrations for the chamber. These can be used

  15. Hydrostatic Hyperbaric Chamber Ventilation System

    NASA Technical Reports Server (NTRS)

    Sarguisingh, Miriam J.

    2012-01-01

    The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy (HBOT) available in the developing world for the treatment of a variety of medical conditions. Specifically, HBOT is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. HBOT is simply too expensive and too dangerous to implement in the developing world using standard equipment. The HHC technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system to provide controlled pressurization and adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the patient and operating personnel, and physiological considerations. The simple schematic, comprised of easily acquired commercial hardware

  16. Computational analysis of GaN/InGaN deposition in MOCVD vertical rotating disk reactors

    NASA Astrophysics Data System (ADS)

    Kadinski, L.; Merai, V.; Parekh, A.; Ramer, J.; Armour, E. A.; Stall, R.; Gurary, A.; Galyukov, A.; Makarov, Yu.

    2004-01-01

    Calculation models that adequately represent the effects of process parameters (such as reactor pressure, shroud and reactants flow) and reactor geometry (such as injector and reactor chamber design) on growth rate and uniformity of GaN/InGaN in the EMCORE's D180 and E300 platforms have been developed. It has been proven that the use of very detailed three-dimensional geometrical models is of crucial importance for accurate predictions. Recent modeling of growth processes within the D180 and E300 systems has lead to improvements in the design and operation of the tools for the growth of GaN/InGaN structures. The following paper outlines the results of one of these improvements: a modification to the alkyl injection system, which improves growth uniformity and alkyl efficiency while optimizing uniformity tuning for a variety of reactor conditions during LED process development.

  17. Reduced pressure MOCVD of C-axis oriented BiSrCaCuO thin films

    NASA Technical Reports Server (NTRS)

    Hamaguchi, Norihito; Vigil, J.; Gardiner, R.; Kirlin, P. S.

    1990-01-01

    BiSrCaCuO thin films were deposited on MgO (100) single-crystal substrates by metalorganic chemical vapor deposition at 500 C and 2 torr using fluorinated beta-diketonate complexes of Sr, Ca, and Cu and triphenylbismuth. An inverted vertical reaction chamber allowed uniform film growth over large areas (7.7 cm diameter). The as-deposited films were amorphous mixtures of oxides and fluorides; a two-step annealing protocol (750 C + 850-870 C) was developed which gives c-axis oriented films of Bi2Sr2Ca1Cu2O(x). The postannealed films showed onsets in the resistive transition of 110 K, and zero resistivity was achieved by 83 K. Critical current densities as high as 11,000 A/sq cm were obtained at 25 K.

  18. Reduced pressure MOCVD of C-axis oriented BiSrCaCuO thin films

    NASA Technical Reports Server (NTRS)

    Hamaguchi, Norihito; Vigil, J.; Gardiner, R.; Kirlin, P. S.

    1990-01-01

    BiSrCaCuO thin films were deposited on MgO (100) single-crystal substrates by metalorganic chemical vapor deposition at 500 C and 2 torr using fluorinated beta-diketonate complexes of Sr, Ca, and Cu and triphenylbismuth. An inverted vertical reaction chamber allowed uniform film growth over large areas (7.7 cm diameter). The as-deposited films were amorphous mixtures of oxides and fluorides; a two-step annealing protocol (750 C + 850-870 C) was developed which gives c-axis oriented films of Bi2Sr2Ca1Cu2O(x). The postannealed films showed onsets in the resistive transition of 110 K, and zero resistivity was achieved by 83 K. Critical current densities as high as 11,000 A/sq cm were obtained at 25 K.

  19. Chamber dynamic research with pulsed power

    SciTech Connect

    PETERSON,ROBERT R.; OLSON,CRAIG L.; RENK,TIMOTHY J.; ROCHAU,GARY E.; SWEENEY,MARY ANN

    2000-05-15

    In Inertial Fusion Energy (IFE), Target Chamber Dynamics (TCD) is an integral part of the target chamber design and performance. TCD includes target output deposition of target x-rays, ions and neutrons in target chamber gases and structures, vaporization and melting of target chamber materials, radiation-hydrodynamics in target chamber vapors and gases, and chamber conditions at the time of target and beam injections. Pulsed power provides a unique environment for IFE-TCD validation experiments in two important ways: they do not require the very clean conditions which lasers need and they currently provide large x-ray and ion energies.

  20. Single wire drift chamber design

    SciTech Connect

    Krider, J.

    1987-03-30

    This report summarizes the design and prototype tests of single wire drift chambers to be used in Fermilab test beam lines. The goal is to build simple, reliable detectors which require a minimum of electronics. Spatial resolution should match the 300 ..mu..m rms resolution of the 1 mm proportional chambers that they will replace. The detectors will be used in beams with particle rates up to 20 KHz. Single track efficiency should be at least 99%. The first application will be in the MT beamline, which has been designed for calibration of CDF detectors. A set of four x-y modules will be used to track and measure the momentum of beam particles.

  1. Space Chambers for Crop Treatment

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Vacuum chambers, operated by McDonnell Douglas Corporation to test spacecraft, can also be used to dry water-soaked records. The drying temperature is low enough to allow paper to dry without curling or charging. Agricultural crops may also be dried using a spinoff system called MIVAC, which has proven effective in drying rice, wheat, soybeans, corn, etc. The system is energy efficient and can incorporate a sanitation process for destroying insects without contamination.

  2. 21 CFR 868.5470 - Hyperbaric chamber.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... than atmospheric pressure. This device does not include topical oxygen chambers for extremities (§ 878... hyperbaric chamber is a device that is intended to increase the environmental oxygen pressure to promote...

  3. NASA Goddard's Acoustic Test Chamber

    NASA Image and Video Library

    2017-09-28

    At Goddard, the engineers use the Acoustic Test Chamber, a 42-foot-tall chamber, with 6-foot-diameter speaker horns to replicate the launch environment. The horns use an altering flow of gaseous nitrogen to produce a sound level as high as 150 decibels for two-minute tests. That’s about the level of sound heard standing next to a jet engine during takeoff. The 6-foot-wide horns in this 42-foot-tall chamber can produce noise at levels as high as 150 dB. During the acoustics test, the speakers can still be heard outside of its insulated massive metal doors. Credits: NASA/Goddard/Chris Gunn NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  4. The crop growth research chamber

    NASA Technical Reports Server (NTRS)

    Wagenbach, Kimberly

    1993-01-01

    The Crop Growth Research Chamber (CGRC) has been defined by CELSS principle investigators and science advisory panels as a necessary ground-based tool in the development of a regenerative life support system. The focus of CGRC research will be on the biomass production component of the CELSS system. The ground-based Crop Growth Research Chamber is for the study of plant growth and development under stringently controlled environments isolated from the external environment. The chamber has importance in three areas of CELSS activities: (1) crop research; (2) system control and integration, and (3) flight hardware design and experimentation. The laboratory size of the CGRC will be small enough to allow duplication of the unit, the conducting of controlled experiments, and replication of experiments, but large enough to provide information representative of larger plant communities. Experiments will focus on plant growth in a wide variety of environments and the effects of those environments on plant production of food, water, oxygen, toxins, and microbes. To study these effects in a closed system, tight control of the environment is necessary.

  5. Rocket Engine Thrust Chamber Assembly

    NASA Technical Reports Server (NTRS)

    Cornelius, Charles S. (Inventor); Counts, Richard H. (Inventor); Myers, W. Neill (Inventor); Lackey, Jeffrey D. (Inventor); Peters, Warren (Inventor); Shadoan, Michael (Inventor); Sparks, David L. (Inventor); Lawrence, Timothy W. (Inventor)

    2001-01-01

    A thrust chamber assembly for liquid fueled rocket engines and the method of making it wherein a two-piece mandrel having the configuration of an assembly having a combustion chamber portion connected to a nozzle portion through a throat portion is wrapped with a silica tape saturated with a phenolic resin, the tape extending along the mandrel and covering the combustion chamber portion of the mandrel to the throat portion. The width of the tape is positioned at an angle of 30 to 50 deg. to the axis of the mandrel such that one edge of the tape contacts the mandrel while the other edge is spaced from the mandrel. The phenolic in the tape is cured and the end of the wrap is machined to provide a frusto-conical surface extending at an angle of 15 to 30 deg. with respect to the axis of the mandrel for starting a second wrap on the mandrel to cover the throat portion. The remainder of the mandrel is wrapped with a third silica tape having its width positioned at a angle of 5 to 20 deg. from the axis of the mandrel. The resin in the third tape is cured and the assembly is machined to provide a smooth outer surface. The entire assembly is then wrapped with a tow of graphite fibers wetted with an epoxy resin and, after the epoxy resin is cured, the graphite is machined to final dimensions.

  6. The LIFE Dynamic Chamber System

    NASA Astrophysics Data System (ADS)

    Rhodes, Mark; Kane, Jave; Latkowski, Jeffery; Cook, Andrew; Divol, Laurent; Loosmore, Gwendolen; Scott, Howard; Scullard, Christian; Tabak, Max; Wilks, Scott; Moses, Gregory; Heltemes, Thad; Sacks, Ryan; Pantano, Carlos; Kramer, Richard

    2011-10-01

    Dry-wall IFE designs such as LIFE utilize Xe fill gas to protect the target chamber first wall from x-ray heating and ionic debris. A key question is how cool, settled and clean the Xe must be to permit beam propagation and target transport, and how to reach this state at a 10+ Hz shot repetition rate. Xe is at low density in the target chamber, and purified Xe is reinjected at higher density and lower temperature into the larger outer chamber. Maintenance of this density difference due to blast waves generated by implosion of the target capsules is being assessed with HYDRA and 3D VTF, and possible validation experiments are being investigated. Detailed gas response near the wall is being studied using 3D Miranda. A laboratory-scale theta pinch experiment will study cooling and beam propagation in Xe. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. Effects of growth parameters on layer properties for InP and related alloys grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Eguchi, K.; Ohba, Y.; Kushibe, M.; Funamizu, M.; Nakanisi, T.

    1988-12-01

    The effects of group-V and group-III source flow rates on epi-layer properties have been studied for the MOCVD growth of InP and GaInPAs. For InP, the surface morphology and photoluminescence (PL) intensity were almost completely determined by PH 3 flow rate, independent of TMIn flow rate. On the other hand, the PL full width at half maximum (FWHM) and electron mobility were determined by the {V}/{III} ratio. The carrier concentration of Se-doped InP was unchanged by both PH 3 and TMIn flow rate, differing from that of Se-doped GaAs. The composition ratio of As to P for GaInPAs was mainly determined by the flow ratio of AsH 3 to PH 3, but affected by the total group-V flow rate (AsH 3+PH 3) and by the group-III alloy composition. It was found that the absolute PH 3 pressure in the vapor phase was one of the most important growth parameters in determining the epi-layer properties.

  8. Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

    PubMed

    Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

    2013-04-07

    We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

  9. Structural and optical properties of AlGaN/GaN quantum well structures grown by MOCVD on sapphire

    SciTech Connect

    Niebuhr, R.; Bachem, K.H.; Behr, D.

    1997-12-31

    AlGaN/GaN single quantum wells (QW) have been grown on 2 in. sapphire substrates (c-plane) by metal-organic chemical vapor deposition (MOCVD). The well width was varied between 20 and 40 {angstrom} for barriers containing 4% and 16% of aluminum. Cathodoluminescence (CL) and Photoluminescence (PL) spectra of the samples show, as expected, a shift of the quantum well emission to higher energies with decreasing well width, whereas the barrier luminescence stays at constant energy. Examination of the QWs by resonant Raman spectroscopy tuned to the gap of the well, clearly shows the GaN A{sub 1}(LO) phonon besides the AlGaN A{sub 1}(LO) phonon from the barrier. For a well width of 20 {angstrom} the authors observe a shift of the A{sub 1}(LO) GaN phonon indicating a certain degree of intermixing at the GaN/AlGaN interface. Atomic Force Microscopy (AFM) reveals that the layers are growing in a 2-dimensional step flow growth mode with step heights of 3 and 6 {angstrom} corresponding to mono- and biatomic steps. High Resolution Transmission Electron Microscopy (HRTEM) micrographs of the 40 {angstrom} well show a very low interface roughness of 1--2 atomic layers.

  10. Advanced light-scattering materials: Double-textured ZnO:B films grown by LP-MOCVD

    NASA Astrophysics Data System (ADS)

    Addonizio, M. L.; Spadoni, A.; Antonaia, A.

    2013-12-01

    Double-textured ZnO:B layers with enhanced optical scattering in both short and long wavelength regions have been successfully fabricated using MOCVD technique through a three step process. Growth of double-textured structures has been induced by wet etching on polycrystalline ZnO surface. Our double-layer structure consists of a first ZnO:B layer wet etched and subsequently used as substrate for a second ZnO:B layer deposition. Polycrystalline ZnO:B layers were etched by utilizing diluted solutions of fluoridic acid (HF), chloridric acid (HCl) and phosphoric acid (H3PO4) and their effect on surface morphology modification was systematically investigated. The morphology of the second deposited ZnO layer strongly depended on the surface properties of the etched ZnO first layer. Growth of cauliflower-like texture was induced by protrusions presence on the HCl etched surface. Optimized double-layer structure shows a cauliflower-like double texture with higher RMS roughness and increased spectral haze values in both short and long wavelength regions, compared to conventional pyramidal-like single texture. Furthermore, this highly scattering structure preserves excellent optical and electrical properties.

  11. Multi-Aperture Shower Design for the Improvement of the Transverse Uniformity of MOCVD-Derived GdYBCO Films.

    PubMed

    Zhao, Ruipeng; Liu, Qing; Xia, Yudong; Zhang, Fei; Lu, Yuming; Cai, Chuanbing; Tao, Bowan; Li, Yanrong

    2017-09-15

    A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO₃/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y₂O₃-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (Jc) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm² through adopting the micro-bridge four-probe method.

  12. Multi-Aperture Shower Design for the Improvement of the Transverse Uniformity of MOCVD-Derived GdYBCO Films

    PubMed Central

    Zhao, Ruipeng; Liu, Qing; Xia, Yudong; Zhang, Fei; Lu, Yuming; Cai, Chuanbing; Tao, Bowan; Li, Yanrong

    2017-01-01

    A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO3/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (Jc) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm2 through adopting the micro-bridge four-probe method. PMID:28914793

  13. Investigation on structural, optical and electrical properties of Cp2Mg flow varied p-GaN grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Surender, S.; Pradeep, S.; Ramesh, R.; Baskar, K.

    2016-05-01

    In this work the effect of different concentration of Magnesium doped GaN (p-GaN) were systematically studied. The p-GaN epilayers were grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD) with various flow rates of 100 sccm to 300 sccm using bis-(cyclopentadienyl) - magnesium (Cp2Mg) precursor. The samples were subjected to structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. Results indicated that the Mg doped GaN of 200 sccm Cp2Mg has the root mean square (rms) roughness of about 0.3 nm for a scan area of 5×5 µm2 which has good two dimensional growth. Moreover, Hall measurements results shows that (200 sccm Cp2Mg) Mg-doped GaN possess the highest hole concentration of 5.4×1017cm-3 and resistivity of 1.7 Ωcm at room temperature.

  14. Catalyst-free growth of ZnO nanowires by metal-organic chemical vapour deposition (MOCVD) and thermal evaporation

    SciTech Connect

    Lee, Woong; Jeong, Min-Chang; Myoung, Jae-Min

    2004-08-02

    ZnO nanowires were grown on GaAs(0 0 2) substrates using metal-organic chemical vapour deposition (MOCVD) and on Si(0 0 1) substrates using thermal evaporation of source powders, respectively. It was demonstrated that well-aligned single crystalline nanowires could be grown with controlled sizes using a typical thin film deposition technique without catalysts. Arsenic doping of the ZnO nanowires grown on GaAs substrate was possible using post-growth heat-treatment, proposing a possible way of producing p-type ZnO nanowires. It was also shown that simplified process of carrier-free thermal evaporation without catalyst could be employed to grow nanowires with high yield while maintaining good crystalline and optical properties. Application potential of the nanowires as probes of atomic force microscopes (AFMs) was discussed by predicting their structural compatibility with AFM cantilevers based on continuum elasticity. It was predicted that the nanowires fabricated herein are structurally compatible with typical AFM cantilevers suggesting that they are promising candidates for high aspect ratio probes.

  15. MOCVD of ZnO thin films for potential use as compliant layers for GaN on Si

    NASA Astrophysics Data System (ADS)

    Black, Kate; Jones, Anthony C.; Chalker, Paul R.; Gaskell, Jeffrey M.; Murray, Robert T.; Joyce, Tim B.; Rushworth, Simon A.

    2008-03-01

    This paper explores the use of nanostructured zinc oxide (ZnO) films as a compliant buffer layer for the growth of gallium nitride (GaN) on silicon substrates. Thin films of ZnO have been deposited on silicon (1 1 1) substrates by liquid injection metalorganic chemical vapour deposition (MOCVD) using dimethyl zinc-tetrahydrofuran adduct and oxygen. The use of the adduct complex avoids pre-reaction between the dialkyl zinc complex and oxygen which has been observed elsewhere. ZnO films deposited by this method were stoichiometric and of high purity, with no detectable carbon contamination. Films were deposited over a temperature range 350-550 °C, and exhibited a nanowire-like morphology. Subsequent deposition of GaN layers grown by molecular beam epitaxy (MBE) on the ZnO film resulted in the transformation of the nanowires to gallium oxide, accompanied by virtually complete removal of zinc from the layer. A heteroepitaxially oriented ( c-axis) GaN/gallium oxide/silicon structure was produced after the nitride deposition which consisted of characteristic columnar GaN with the GaN[0 0 0 1]||Si [1 1 1]. Selective area electron diffraction of the by-product oxide interlayer showed a polycrystalline-like behaviour that gave rise to a random azimuthal distribution of the GaN grains.

  16. Broad Temperature Pinning Study of 15 mol.% Zr-Added (Gd, Y)-Ba-Cu-O MOCVD Coated Conductors

    SciTech Connect

    Xu, AX; Khatri, N; Liu, YH; Majkic, G; Galstyan, E; Selvamanickam, V; Chen, YM; Lei, CH; Abraimov, D; Hu, XB; Jaroszynski, J; Larbalestier, D

    2015-06-01

    BaZrO3 (BZO) nanocolumns have long been shown to be very effective for raising the pinning force F-p of REBa2Cu3Ox (REBCO, where RE = rare earth) films at high temperatures and recently at low temperatures too. We have successfully incorporated a high density of BZO nanorods into metal organic chemical vapor deposited (MOCVD) REBCO coated conductors via Zr addition. We found that, compared to the 7.5% Zr-added coated conductor, dense BZO nanorod arrays in the 15% Zr-added conductor are effective over the whole temperature range from 77 K down to 4.2 K. We attribute the substantially enhanced J(c) at 30 K to the weak uncorrelated pinning as well as the strong correlated pinning. Meanwhile, by tripling the REBCO layer thickness to similar to 2.8 mu m, the engineering critical current density J(e) at 30 K exceeds J(e) of optimized Nb-Ti wires at 4.2 K.

  17. Investigation on structural, optical and electrical properties of Cp2Mg flow varied p-GaN grown by MOCVD

    SciTech Connect

    Surender, S.; Pradeep, S.; Ramesh, R.; Baskar, K.

    2016-05-23

    In this work the effect of different concentration of Magnesium doped GaN (p-GaN) were systematically studied. The p-GaN epilayers were grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD) with various flow rates of 100 sccm to 300 sccm using bis-(cyclopentadienyl) - magnesium (Cp2Mg) precursor. The samples were subjected to structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. Results indicated that the Mg doped GaN of 200 sccm Cp2Mg has the root mean square (rms) roughness of about 0.3 nm for a scan area of 5×5 µm{sup 2} which has good two dimensional growth. Moreover, Hall measurements results shows that (200 sccm Cp2Mg) Mg-doped GaN possess the highest hole concentration of 5.4×10{sup 17}cm{sup −3} and resistivity of 1.7 Ωcm at room temperature.

  18. Investigation of the optimal annealing temperature for the enhanced thermoelectric properties of MOCVD-grown ZnO films

    NASA Astrophysics Data System (ADS)

    Mahmood, K.; Ali, A.; Arshad, M. I.; Ajaz un Nabi, M.; Amin, N.; Faraz Murtaza, S.; Rabia, S.; Azhar Khan, M.

    2017-04-01

    In this study, we demonstrate the optimization of the annealing temperature for enhanced thermoelectric properties of ZnO. Thin films of ZnO are grown on a sapphire substrate using the metal organic chemical Vapor Deposition (MOCVD) technique. The grown films are annealed in an oxygen environment at 600-1000°C, with a step of 100°C for one hour. Seebeck measurements at room temperature revealed that the Seebeck coefficient of the sample that was not annealed was 152 μV/K, having a carrier concentration of N D 1.46 × 1018 cm-3. The Seebeck coefficient of the annealed films increased from 212 to 415 μV/K up to 900°C and then decreased at 1000°C. The power factor is calculated and found to have an increasing trend with the annealing temperature. This observation is explained by the theory of Johnson and Lark-Horovitz that thermoelectric properties are enhanced by improving the structure of ZnO thin films. The Hall measurements and PL data strongly justify the proposed argument.

  19. Material growth and characterization of gallium arsenic antimide on gallium arsenide grown by MOCVD for long wavelength laser applications

    NASA Astrophysics Data System (ADS)

    Noh, Min-Soo

    Due to the demand for faster and higher bit rate optical communication, long wavelength vertical cavity surface emitting laser (VCSEL) has been attracting great interests because of its ability of 2D array application. Although InGaAsP/InP edge emitting lasers (EEL) have been well developed and commercially available, the lack of high contrast distributed Bragg reflector (DBR) for the material system forced to find new active materials that can be grown on GaAs substrate to exploit AlGaAs/GaAs DBR pairs. For the purpose, GaAsSb has been studied as the active material. This dissertation describes and discusses the GaAsSb semiconductor material growth, the optimization of the growth conditions, and the characterization of the laser devices fabricated from GaAsSb QW structures. Based on the optimal growth conditions, EELs operating at room temperature in CW mode at the wavelength of 1.27 mum have been demonstrated from the GaAsSb QW structure with GaAsP barriers grown monolithically by MOCVD.

  20. MOCVD Growth and Optical Characterization of Strain-Induced Quantum Dots with InP Island Stressors

    SciTech Connect

    Hanna, M. C.; Lu, Z. H.; Cahill, A. F.; Heben, M. J.; Nozik, A. J.

    1997-01-01

    Coherent InP islands, grown by low pressure metal organic chemical vapor deposition (MOCVD), were used to produce quantum dots by strain confinement. Lateral confinement of carriers in a GaAs/AlGaAs quantum well located near the surface was obtained from the inhomogeneous strain produced by the InP islands. The evolution of the InP islands on Al0.3Ga0.7As surfaces with increasing InP coverage at different growth temperatures and substrate orientations was studied using atomic force microscopy. Under certain growth conditions, a fairly uniform distribution of coherent InP islands was obtained which had an average apparent diameter of 140 nm with a standard deviation of 12.2 nm and height of 19.5 {+-} 1.1 nm. Lateral confinement depths up to 100 meV were obtained when using the islands as stressors. Photoluminescence from ensembles of the strain-induced dots exhibit peaks, narrow line widths (16 meV) and high efficiency up to room temperature.

  1. Monolithic integration of MQW wavelength tunable DBR lasers with external cavity electroabsorption modulators by selective-area MOCVD

    NASA Astrophysics Data System (ADS)

    Lammert, Robert M.; Smith, Gary M.; Hughes, J. S.; Osowski, Mark L.; Jones, A. M.; Coleman, James J.

    1997-01-01

    The design and operation of multiple-quantum well (MQW) wavelength tunable distributed Bragg reflector (DBR) lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area metal-organic chemical vapor deposition (MOCVD) are presented. Uncoated devices exhibit cw threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet and 0.06 W/A from the modulator facet. After the application of facet coatings, slope efficiencies from the modulator facet increase to 0.14 W/A. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibit high extinction ratios of 40 dB at a modulator bias of 1.25 V. Photo-generated current versus optical power plots indicate that the extinction ratios are not limited by carrier build- up in the modulator quantum wells.

  2. Observation of important current-limiting defects in a recent high pinning force MOCVD IBAD-MgO coated conductor

    NASA Astrophysics Data System (ADS)

    Li, Pei; Abraimov, Dmytro; Xu, Aixia; Larbalestier, David

    2012-02-01

    Optimization of vortex pinning in REBCO coated conductors has been very successful in recent years, but here we report that strong current-limiting effects can still be present in even highly optimized samples. We studied a state-of-the-art MOCVD IBAD-MgO coated conductor, finding it to have a global pinning force Fpmax(77 K, H ∥ c axis) that reached 11 GN m-3. Using low temperature laser scanning microscopy (LTLSM), we found that the local electric field in the flux-flow state was very inhomogeneous and dominated by a high density of a-axis grains, which obstruct current flow on dimensions of several µm. By carefully cutting narrow tracks without such grains in the path, Fpmax rose to 17 GN m-3, a value exceeding all but a very few, carefully made research films. That today’s coated conductors can develop exceptional vortex pinning properties, while still losing a significant fraction of the current density to blocking by growth defects, emphasizes that coated conductor development requires simultaneous attention both to enhancement of vortex pinning and to minimization of current-blocking defects.

  3. In situ monitoring and control of multicomponent gas-phase streams for growth of GaN via MOCVD

    NASA Astrophysics Data System (ADS)

    Johnson, M. C.; Poochinda, K.; Ricker, N. L.; Rogers, J. W., Jr.; Pearsall, T. P.

    A monitoring method based on ultraviolet absorption spectroscopy (UVAS) coupled with a multivariate analysis technique was developed to measure the partial pressure of several metalorganic reactant species and the hydride commonly used for III-V nitride growth. Trimethylaluminum, triethylgallium, dimethylethylamine alane and ammonia are all shown to absorb strongly in the UV with highly overlapping spectra. It was found that a single absorption spectrum can be decomposed to obtain accurate predictions of pure component partial pressures in a multicomponent stream. This method was used to monitor and control the gas-phase concentrations for the multicomponent mixture of triethylgallium and ammonia diluted in nitrogen, which is used to grow GaN thin films via MOCVD. There was a 5% average error for the predicted partial pressure of TEGa in the range 245-700 mTorr and a 2% average error for the predicted partial pressure of NH 3 in the range 15-35 Torr. A detection limit of 10 mTorr and 1 Torr were measured for TEGa and NH 3, respectively. For simple feedback control and using this method as a measurement device, settling times of 1 min for TEGa and 30 s for NH 3 to reach within 2% of the desired partial pressure have been obtained. Control tests included both setpoint tracking and gas-phase disturbance rejection. These settling times were found to be no greater than {1}/{40} of the total growth time for a commonly grown GaN thin film.

  4. Gas turbine combustion chamber with air scoops

    SciTech Connect

    Mumford, S.E.; Smed, J.P.

    1989-12-19

    This patent describes a gas turbine combustion chamber. It comprises: means for admission of fuel to the upstream end thereof and discharge of hot gases from the downstream end thereof, and a combustion chamber wall, having an outer surface, with apertures therethrough, and air scoops provided through the apertures to direct air into the combustion chamber.

  5. Making a Fish Tank Cloud Chamber

    ERIC Educational Resources Information Center

    Green, Frances

    2012-01-01

    The cloud chambers described here are large, made from readily available parts, simple to set up and always work. With no source in the chamber, background radiation can be observed. A large chamber means that a long rod containing a weakly radioactive material can be introduced, increasing the chance of seeing decays. Details of equipment and…

  6. Uniform-Temperature Walls for Cloud Chambers

    NASA Technical Reports Server (NTRS)

    Fleischman, G.

    1985-01-01

    Flat heat pipes rapidly transfer heat to and from experimental volumes. Heat pipe vapor chamber carries heat to and from thermo electric modules. Critical surface acts as evaporator or condenser in cloud physics experiments. Used as walls of spaceborne atmospheric cloud chambers. On Earth, used as isothermal floors for environmental test chambers.

  7. A Sensitive Cloud Chamber without Radioactive Sources

    ERIC Educational Resources Information Center

    Zeze, Syoji; Itoh, Akio; Oyama, Ayu; Takahashi, Haruka

    2012-01-01

    We present a sensitive diffusion cloud chamber which does not require any radioactive sources. A major difference from commonly used chambers is the use of a heat sink as its bottom plate. The result of a performance test of the chamber is given. (Contains 8 figures.)

  8. A Sensitive Cloud Chamber without Radioactive Sources

    ERIC Educational Resources Information Center

    Zeze, Syoji; Itoh, Akio; Oyama, Ayu; Takahashi, Haruka

    2012-01-01

    We present a sensitive diffusion cloud chamber which does not require any radioactive sources. A major difference from commonly used chambers is the use of a heat sink as its bottom plate. The result of a performance test of the chamber is given. (Contains 8 figures.)

  9. Uniform-Temperature Walls for Cloud Chambers

    NASA Technical Reports Server (NTRS)

    Fleischman, G.

    1985-01-01

    Flat heat pipes rapidly transfer heat to and from experimental volumes. Heat pipe vapor chamber carries heat to and from thermo electric modules. Critical surface acts as evaporator or condenser in cloud physics experiments. Used as walls of spaceborne atmospheric cloud chambers. On Earth, used as isothermal floors for environmental test chambers.

  10. Making a Fish Tank Cloud Chamber

    ERIC Educational Resources Information Center

    Green, Frances

    2012-01-01

    The cloud chambers described here are large, made from readily available parts, simple to set up and always work. With no source in the chamber, background radiation can be observed. A large chamber means that a long rod containing a weakly radioactive material can be introduced, increasing the chance of seeing decays. Details of equipment and…

  11. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry…

  12. EPA GAS PHASE CHEMISTRY CHAMBER STUDIES

    EPA Science Inventory

    Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

  13. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry…

  14. EPA GAS PHASE CHEMISTRY CHAMBER STUDIES

    EPA Science Inventory

    Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

  15. Chamber B Thermal/Vacuum Chamber: User Test Planning Guide

    NASA Technical Reports Server (NTRS)

    Montz, Mike E.

    2012-01-01

    Test process, milestones and inputs are unknowns to first-time users of Chamber B. The User Test Planning Guide aids in establishing expectations for both NASA and non-NASA facility customers. The potential audience for this guide includes both internal and commercial spaceflight hardware/software developers. It is intended to assist their test engineering personnel in test planning and execution. Material covered includes a roadmap of the test process, roles and responsibilities of facility and user, major milestones, facility capabilities, and inputs required by the facility. Samples of deliverables, test article interfaces, and inputs necessary to define test scope, cost, and schedule are included as an appendix to the guide.

  16. Chambers Air and Space Dictionary.

    NASA Astrophysics Data System (ADS)

    Walker, P. M. B.

    This dictionary is concerned with the sciences and technologies of everything above the Earth's surface. It has been developed from the database of Chambers Science and Technology Dictionary with many new and revised definitions in this group of fast-changing subjects. The book contains some 6000 definitions, including 1500 in aeronautics, 600 in astronomy, 500 in meteorology and 400 for space and radar. The special articles, placed in separate panels, are a major feature of the dictionary. These, many of which are illustrated, supply fuller treatments of major topics within each subject.

  17. The DELPHI time projection chamber

    SciTech Connect

    Brand, C.; Cairanti, G.; Charpentier, P.; Clara, M.P.; Delikaris, D.; Foeth, H.; Heck, B.W.; Hilke, H.J.; Sulkowski, K.; Aubret, C.

    1989-02-01

    The central tracking device of the DELPHI Experiment at LEP is a Time Projection Chamber (TPC) with an active volume of 2 x 1.34m in length and 2.22m in diameter. Since spring 1988 the TPC has undergone extensive tests in a cosmic ray set-up. It will be installed in the LEP tunnel by early 1989. This report covers the construction, the read-out electronics and the contribution of the TPC to the DELPHI trigger. Emphasis is given to novelties which are not used in similar detectors.

  18. Portable Ethylene Oxide Sterilization Chamber

    PubMed Central

    Songer, J. R.; Mathis, R. G.

    1969-01-01

    A portable ethylene oxide sterilization chamber was designed, constructed, and tested for use in the sterilization of embolectomy catheters. The unit can accommodate catheters up to 40 inches (101.6 cm) in length and can be operated for less than 4 cents per cycle. A constant concentration of 500 mg of ethylene oxide per liter of space and holding periods of 4 and 6 hr at 43 and 22 C, respectively, were adequate when tested with B. subtilis spores. The estimated cost of construction was $165.00. If temperature control is unnecessary, the cost is approximately $80.00. Images PMID:4977644

  19. Basic Aerodynamics of Combustion Chambers,

    DTIC Science & Technology

    1981-05-20

    8217, tie imnrulse foree eyuilibr-um c’ the bomd’~ leye - is 173 pv-:irJ p~76vJbK 2sO) IL !-. = Zn pT -- a , bV T. z -,,r y.re C era 3oia * ~~I" onc art-=e...heat by combustion all have very large influences on the capabilities of a combustion chamber. A yellow- colored flame represents diffusion combustion in...the wakes of fuel droplets. Blue- colored flames represent gaseous combustion of evaporated vapors which have already left the fuel droplets. The

  20. Thrust chamber material technology program

    NASA Astrophysics Data System (ADS)

    Andrus, J. S.; Bordeau, R. G.

    1989-03-01

    This report covers work performed at Pratt & Whitney on development of copper-based materials for long-life, reusable, regeneratively cooled rocket engine thrust chambers. The program approached the goal of enhanced cyclic life through the application of rapid solidification to alloy development, to introduce fine dispersions to strengthen and stabilize the alloys at elevated temperatures. After screening of alloy systems, copper-based alloys containing Cr, Co, Hf, Ag, Ti, and Zr were processed by rapid-solidification atomization in bulk quantities. Those bulk alloys showing the most promise were characterized by tensile testing, thermal conductivity testing, and elevated-temperature, low-cycle fatigue (LFC) testing. Characterization indicated that Cu- 1.1 percent Hf exhibited the greatest potential as an improved-life thrust chamber material, exhibiting LCF life about four times that of NASA-Z. Other alloys (Cu- 0.6 percent Zr, and Cu- 0.6 percent Zr- 1.0 percent Cr) exhibited promise for use in this application, but needed more development work to balance properties.

  1. Thrust chamber material technology program

    NASA Technical Reports Server (NTRS)

    Andrus, J. S.; Bordeau, R. G.

    1989-01-01

    This report covers work performed at Pratt & Whitney on development of copper-based materials for long-life, reusable, regeneratively cooled rocket engine thrust chambers. The program approached the goal of enhanced cyclic life through the application of rapid solidification to alloy development, to introduce fine dispersions to strengthen and stabilize the alloys at elevated temperatures. After screening of alloy systems, copper-based alloys containing Cr, Co, Hf, Ag, Ti, and Zr were processed by rapid-solidification atomization in bulk quantities. Those bulk alloys showing the most promise were characterized by tensile testing, thermal conductivity testing, and elevated-temperature, low-cycle fatigue (LFC) testing. Characterization indicated that Cu- 1.1 percent Hf exhibited the greatest potential as an improved-life thrust chamber material, exhibiting LCF life about four times that of NASA-Z. Other alloys (Cu- 0.6 percent Zr, and Cu- 0.6 percent Zr- 1.0 percent Cr) exhibited promise for use in this application, but needed more development work to balance properties.

  2. MPD thrust chamber flow dynamics

    NASA Astrophysics Data System (ADS)

    1990-08-01

    Flow within the thrust chamber of a Magnetoplasmadynamic (MPD) arcjet is examined experimentally and modeled with a 2-D magnetohydrodynamic code. Two quasi-steady MPD thrusters are considered under the same input conditions of current (21 kA) and total mass flow rate (0.006 kg/s, argon + 1.5 percent hydrogen). The arcjets have the same basic design, consisting of a central cathode, 3.8 cm diameter and 5 cm long, separated from a coaxial anode of equal length by a uniform gap of 2.3 cm. Two different mass injection arrangements are used (100 percent at mid-radius, and 50 percent at the cathode base, with the remainder at mid-radius). A new spectroscopic analysis procedure is developed that allows distributions of radial speed, heavy particle temperature and turbulent speed to be extracted from chordal measurements of light emission by the two species in the plasma flow. Good qualitative (and reasonable quantitative) agreement exists with distributions calculated by the MHD code, indicating that flow within the thrust chamber expands from an electromagnetically pumped plasma base (vs a pumped jet off the cathode tip). The significant variation of internal flow dynamics with mass injector arrangement implies the need for extensive experimentally validated code modeling in order to evaluate the potential performance of MPD thrusters.

  3. Sc2O3, Er2O3, and Y2O3 thin films by MOCVD from volatile guanidinate class of rare-earth precursors.

    PubMed

    Milanov, Andrian P; Xu, Ke; Cwik, Stefan; Parala, Harish; de los Arcos, Teresa; Becker, Hans-Werner; Rogalla, Detlef; Cross, Richard; Paul, Shashi; Devi, Anjana

    2012-12-07

    Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)(3)] (1), tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)(3)] (2) and tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)(3)] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films, respectively, by metal-organic chemical vapor deposition (MOCVD). Uniform Sc(2)O(3), Er(2)O(3) and Y(2)O(3) films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350-700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1-3 are very good precursors for MOCVD yielding Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.

  4. Tubular copper thrust chamber design study

    NASA Technical Reports Server (NTRS)

    Masters, A. I.; Galler, D. E.

    1992-01-01

    The use of copper tubular thrust chambers is particularly important in high performance expander cycle space engines. Tubular chambers have more surface area than flat wall chambers, and this extra surface area provides enhanced heat transfer for additional energy to power the cycle. This paper was divided into two sections: (1) a thermal analysis and sensitivity study; and (2) a preliminary design of a selected thrust chamber configuration. The thermal analysis consisted of a statistical optimization to determine the optimum tube geometry, tube booking, thrust chamber geometry, and cooling routing to achieve the maximum upper limit chamber pressure for a 25,000 pound thrust engine. The preliminary design effort produced a layout drawing of a tubular thrust chamber that is three inches shorter than the Advanced Expander Test Bed (AETB) milled channel chamber but is predicted to provide a five percent increase in heat transfer. Testing this chamber in the AETB would confirm the inherent advantages of tubular chamber construction and heat transfer.

  5. Rocket thrust chamber thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Quentmeyer, R. J.

    1985-01-01

    Subscale rocket thrust chamber tests were conducted to evaluate the effectiveness and durability of thin yttria stabilized zirconium oxide coatings applied to the thrust chamber hot-gas side wall. The fabrication consisted of arc plasma spraying the ceramic coating and bond coat onto a mandrell and then electrodepositing the copper thrust chamber wall around the coating. Chambers were fabricated with coatings .008, and .005 and .003 inches thick. The chambers were thermally cycled at a chamber pressure of 600 psia using oxygen-hydrogen as propellants and liquid hydrogen as the coolant. The thicker coatings tended to delaminate, early in the cyclic testing, down to a uniform sublayer which remained well adhered during the remaining cycles. Two chambers with .003 inch coatings were subjected to 1500 thermal cycles with no coating loss in the throat region, which represents a tenfold increase in life over identical chambers having no coatings. An analysis is presented which shows that the heat lost to the coolant due to the coating, in a rocket thrust chamber design having a coating only in the throat region, can be recovered by adding only one inch to the combustion chamber length.

  6. Structural and optical investigations of Al xGa 1- xAs:Si/GaAs(1 0 0) MOCVD heterostructures

    NASA Astrophysics Data System (ADS)

    Seredin, P. V.; Glotov, A. V.; Domashevskaya, E. P.; Arsentyev, I. N.; Vinokurov, D. A.; Tarasov, I. S.

    2010-11-01

    Al xGa 1- xAs:Si/GaAs(1 0 0) heterostructure and homoepitaxial GaAs:Si/GaAs(1 0 0) structures grown by MOCVD were investigated. The changes observed in our experiments with highly doped Al xGa 1- xAs alloys, led not only to the reconstruction of the electron density and formation of deep levels (DX-centers) with subsequent relaxation of the crystal lattice in the alloy, but also indicate at the formation of quaternary Al xGa 1- x- ySi y+ zAs 1- z substitution-type alloy grown on GaAs(1 0 0).

  7. Composite fermions in 2 x 10{sup 6} cm{sup 2}/Vs mobility A1GaAs/GaAs heterostructures grown by MOCVD

    SciTech Connect

    Simmons, J.A., Chui, H.C., Harff, N.E., Hammons, B.E.; Du, R.R., Zudov, M.A.

    1996-12-31

    Recent growth by MOCVD (metalorganic chemical vapor deposition) of 2.0x10{sup 6} cm{sup 2}/Vs mobility heterostructures are reported. These mobilities, the highest reported to date, are attributed to use of tertiarybutylarsine as the arsenic precursor. Measurements in tilted magnetic fields of the fractional quantum Hall effect states near filling factor 3/2 are consistent with a spin-split composite fermion (CF) model proposed earlier. Extracted values of the product of the CF g-factor and CF effective mass agree with values previously obtained for MBE samples.

  8. Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation

    NASA Astrophysics Data System (ADS)

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.

    2005-08-01

    A novel device of tandem MQW EAMs monolithically integrated with a DFB laser is fabricated by an ultra-low-pressure (22 mbar) selective area growth MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled to a single mode fibre. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10 GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained.

  9. Tandem electro-absorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short-pulse generation

    NASA Astrophysics Data System (ADS)

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.

    2005-11-01

    A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area growth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled into a single mode fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

  10. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Analysis and finite element simulation of electromagnetic heating in the nitride MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Ming; Hao, Yue; Zhang, Jin-Cheng; Xu, Sheng-Rui; Ni, Jin-Yu; Zhou, Xiao-Wei

    2009-11-01

    Electromagnetic field distribution in the vertical metal organic chemical vapour deposition (MOCVD) reactor is simulated by using the finite element method (FEM). The effects of alternating current frequency, intensity, coil turn number and the distance between the coil turns on the distribution of the Joule heat are analysed separately, and their relations to the value of Joule heat are also investigated. The temperature distribution on the susceptor is also obtained. It is observed that the results of the simulation are in good agreement with previous measurements.

  11. Growth and characterization of In{sub X}Ga{sub 1-X}N/GaN single quantum well prepared by MOCVD

    SciTech Connect

    Prabakaran, K.; Ramesh, R.; Jayasakthi, M.; Loganathan, R.; Arivazhagan, P.; Baskar, K.

    2015-06-24

    The InGaN/GaN SQW structures were grown on c-plane sapphire substrate using metal-organic chemical vapor deposition (MOCVD). The thickness and indium composition of the InGaN was determined by HRXRD. From simulation fit the composition of indium was found to be 10% and thickness was around 5nm and 10nm. The Photoluminescence emission was found to be shifited towards lower wavelength as 479nm, 440nm on increasing the thickness. The photoluminescence intensity was degrades with increases of InGaN thickness. Atomic force microscopy studies were also carried out and the results are discussed in detail.

  12. Influence of stress in GaN crystals grown by HVPE on MOCVD-GaN/6H-SiC substrate

    PubMed Central

    Zhang, Lei; Yu, Jiaoxian; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Shao, Yongliang; Zhang, Haodong; Tian, Yuan

    2014-01-01

    GaN crystals without cracks were successfully grown on a MOCVD-GaN/6H-SiC (MGS) substrate with a low V/III ratio of 20 at initial growth. With a high V/III ratio of 80 at initial growth, opaque GaN polycrystals were obtained. The structural analysis and optical characterization reveal that stress has a great influence on the growth of the epitaxial films. An atomic level model is used to explain these phenomena during crystal growth. It is found that atomic mobility is retarded by compressive stress and enhanced by tensile stress. PMID:24569601

  13. Influence of stress in GaN crystals grown by HVPE on MOCVD-GaN/6H-SiC substrate.

    PubMed

    Zhang, Lei; Yu, Jiaoxian; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Shao, Yongliang; Zhang, Haodong; Tian, Yuan

    2014-02-26

    GaN crystals without cracks were successfully grown on a MOCVD-GaN/6H-SiC (MGS) substrate with a low V/III ratio of 20 at initial growth. With a high V/III ratio of 80 at initial growth, opaque GaN polycrystals were obtained. The structural analysis and optical characterization reveal that stress has a great influence on the growth of the epitaxial films. An atomic level model is used to explain these phenomena during crystal growth. It is found that atomic mobility is retarded by compressive stress and enhanced by tensile stress.

  14. Transferring calibration coefficients from ionisation chambers used for diagnostic radiology to transmission chambers.

    PubMed

    Yoshizumi, Maíra T; Caldas, Linda V E

    2012-07-01

    In this work, the response of a double volume transmission ionisation chamber, developed at the Instituto de Pesquisas Energéticas e Nucleares, was compared to that of a commercial transmission chamber. Both ionisation chambers were tested in different X-ray beam qualities using secondary standard ionisation chambers as reference dosimeters. These standard ionisation chambers were a parallel-plate and a cylindrical ionisation chambers, used for diagnostic radiology and mammography beam qualities, respectively. The response of both transmission chambers was compared to that of the secondary standard chambers to obtain coefficients of equivalence. These coefficients allow the transmission chambers to be used as reference equipment. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. High and low energy proton radiation damage in p/n InP MOCVD solar cells

    NASA Technical Reports Server (NTRS)

    Rybicki, George; Weinberg, Irving; Scheiman, Dave; Vargas-Aburto, Carlos

    1995-01-01

    InP p(+)nn(+) MOCVD solar cells were irradiated with 0.2 MeV and 10 MeV protons to a fluence of 10(exp 13)/sq cm. The degradation of power output, IV behavior, carrier concentration and defect concentration were observed at intermediate points throughout the irradiations. The 0.2 MeV proton irradiated solar cells suffered much greater and more rapid degradation in power output than those irradiated with 10 meV protons. The efficiency losses were accompanied by larger increases in the recombination currents in the 0.2 MeV proton irradiated solar cells. The low energy proton irradiations also had a larger impact on the series resistance of the solar cells. Despite the radiation induced damage, the carrier concentration in the base of the solar cells showed no reduction after 10 MeV or 0.2 MeV proton irradiations and even increased during irradiation with 0.2 MeV protons. In a DLTS study of the irradiated samples, the minority carrier defects H4 and H5 at E(v) + 0.33 and E(v) + 0.52 eV and the majority carrier defects E7 and E10 at E(c)- 0.39 and E(c)-0.74 eV, were observed. The defect introduction rates for the 0.2 MeV proton irradiations were about 20 times higher than for the 10 MeV proton irradiations. The defect E10, observed here after irradiation, has been shown to act as a donor in irradiated n-type InP and may be responsible for obscuring carrier removal. The results of this study are consistent with the much greater damage produced by low energy protons whose limited range causes them to stop in the active region of the solar cell.

  16. Monomeric malonate precursors for the MOCVD of HfO2 and ZrO2 thin films.

    PubMed

    Pothiraja, Ramasamy; Milanov, Andrian; Parala, Harish; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-01-28

    New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical beta-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 degrees C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.

  17. LP-MOCVD growth of GaAlN/GaN heterostructures on silicon carbide: application to HEMT devices

    NASA Astrophysics Data System (ADS)

    di Forte Poisson, M.-A.; Magis, M.; Tordjman, M.; Aubry, R.; Sarazin, N.; Peschang, M.; Morvan, E.; Delage, S. L.; di Persio, J.; Quéré, R.; Grimbert, B.; Hoel, V.; Delos, E.; Ducatteau, D.; Gaquiere, C.

    2004-12-01

    This paper reports on the LP-MOCVD growth optimisation of GaAlN/GaN heterostructures grown on silicon carbide substrates for HEMT applications, and on the first device performances obtained with these structures. The critical impact of some growth parameters on the physical properties of the GaAlN/GaN epilayers has been identified and studied using high-resolution X-ray diffraction, AFM, C-V and sonogauge measurements. SiC substrates from different suppliers were evaluated and their influence on the physical properties of the GaAlN/GaN HEMT structures were investigated. We show that the static characteristics of the devices such as maximum drain current Idss or pinch-off voltage are correlated with the nucleation layer composition ( GaN or GaAlN) of the HEMT structure and with the defect density of the SiC substrate. A maximum drain current Idss around 1 A/mm and a pinch-off voltage of -5 V have been measured for devices with a gate length of 0.3 μm and a GaN nucleation layer, to be compared to an Idss up to 1.3 A/mm obtained for devices with the same geometry but with a GaAlN nucleation layer. I-V characteristics measured under pulsed measurements have also evidenced a clear impact of the nucleation layer composition on the trap density in the GaAlN/GaN HEMT structure. The first devices related to HEMT wafers with GaN nucleation layers were measured at 10 GHz using a load pull system. They show a CW output power in excess of 2.8 W/mm for a gate length of 0.5 μm, while devices related to HEMT wafers with GaAlN nucleation layer exhibit output power up to 4 W/mm at 10 GHz.

  18. Tests of anechoic chamber for aeroacoustics investigations

    NASA Astrophysics Data System (ADS)

    Palchikovskiy, V. V.; Bersenev, Yu. V.; Makashov, S. Yu.; Belyaev, I. V.; Korin, I. A.; Sorokin, E. V.; Khramtsov, I. V.; Kustov, O. Yu.

    2016-10-01

    The paper presents the results of qualification tests in the new anechoic chamber of Perm National Research Polytechnic University (PNRPU) built in 2014-2015 and evaluation of the chamber quality in aeroacoustic experiments. It describes design features of the chamber and its sound-absorption lining. The qualification tests were carried out with tonal and broadband noise sources in the frequency range 100 Hz - 20 kHz for two different cases of the source arrangement. In every case, measurements were performed in three directions by traverse microphones. Qualification tests have determined that in the chamber there is a free acoustic field within radius of 2 m for tonal noise and 3 m for broadband noise. There was also evaluated acoustic quality of the chamber by measurements of the jet noise and vortex ring noise. The results of the experiments demonstrate that PNRPU anechoic chamber allows the aeroacoustic measurements to be performed to obtain quantitative results.

  19. Neutron-chamber detectors and applications

    SciTech Connect

    Fehlau, P.E.; Atwater, H.F.; Coop, K.L.

    1990-01-01

    Detector applications in Nuclear Safeguards and Waste Management have included measuring neutrons from fission and (alpha,n) reactions with well-moderated neutron proportional counters, often embedded in a slab of polyethylene. Other less-moderated geometries are useful for detecting both bare and moderated fission-source neutrons with good efficiency. The neutron chamber is an undermoderated detector design comprising a large, hollow, polyethylene-walled chamber containing one or more proportional counters. Neutron-chamber detectors are relatively inexpensive; can have large apertures, usually through a thin chamber wall; and offer very good detection efficiency per dollar. Neutron-chamber detectors have also been used for monitoring vehicles and for assaying large crates of transuranic waste. Our Monte Carlo calculations for a new application (monitoring low-density waste for concealed plutonium) illustrate the advantages of the hollow-chamber design for detecting moderated fission sources. 9 refs., 6 figs., 2 tabs.

  20. The ARGUS microvertex drift chamber

    NASA Astrophysics Data System (ADS)

    Michel, E.; Schmidt-Parzefall, W.; Appuhn, R. D.; Buchmüller, J.; Kolanoski, H.; Kreimeier, B.; Lange, A.; Siegmund, T.; Walther, A.; Edwards, K. W.; Fernholz, R. C.; Kapitza, H.; MacFarlane, D. B.; O'Neill, M.; Parsons, J. A.; Prentice, J. D.; Seidel, S. C.; Tsipolitis, G.; Ball, S.; Babaev, A.; Danilov, M.; Tichomirov, I.

    1989-11-01

    The ARGUS collaboration is currently building a new microvertex drift chamber (μVDC) as an upgrade of their detector. The μVDC is optimized for B-meson physics at DORIS energies. Important design features are minimal multiple scattering for low-momentum particles and three-dimensional reconstruction of decay vertices with equal resolutions in r- φ and r- z. Vertex resolutions of 15-25 μm are expected. Prototypes of the μVDC have been tested with different gas mixtures at various pressures. Spatial resolutions as small as 20 μm were obtained using CO 2/propane at 4 bar and DME at 1 bar. New readout electronics have been developed for the μVDC aiming at low thresholds for the TDC measurements. Employing a novel idea for noise and cross-talk suppression, which is based on a discrimination against short pulses, very low threshold settings are possible.

  1. An airborne isothermal haze chamber

    NASA Technical Reports Server (NTRS)

    Hindman, E. E.

    1981-01-01

    Thermal gradient diffusion cloud chambers (TGDCC) are used to determine the concentrations of cloud condensation nuclei (CCN) with critical supersaturations greater than or equal to about 0.2%. The CCN concentrations measured with the airborne IHC were lower than theoretically predicted by factors ranging between 7.9 and 9.0. The CCN concentrations measured with the airborne IHC were lower than the concentrations measured with the larger laboratory IHC's by factors ranging between 3.9 and 7.5. The bounds of the supersaturation ranges of the airborne IHC and the CSU-Mee TGDCC do not overlap. Nevertheless, the slopes of the interpolated data between the bounds agree favorably with the theoretical slopes.

  2. Variable oven chamber heating level

    SciTech Connect

    Minasov, A.M.; Sergeev, S.S.; Likhogyb, E.P.

    1984-01-01

    Changes in oven chambers were developed to prevent the uneven heating of a charge in a coke oven. The changes basically altered the heat flow to a charge into the upper section upon a variation in the shrinkage properties of a charge. The engineering modifications are described and illustrated. A damper placed in a converted door is sufficiently easily shifted in the vertical plane and is firmly fixed in the upper position. The distribution of temperatures in the upper part of coke cake is changed within the limits of 80/sup 0/C, depending on the location of the damper in the converted door. When the damper is in the lower position, heating of the upper part of the coke cake increases, and the difference in the temperatures of the coke relative to height is decreased, and vice versa.

  3. IFE Chamber Technology - Status and Future Challenges

    SciTech Connect

    Meier, W.R.; Raffray, A.R.; Abdel-Khalik, S.I.; Kulcinski, G.L.; Latowski, J.F.; Najmabadi, F.; Olson, C.L.; Peterson, P.F.; Ying, A.; Yoda, M.

    2003-07-15

    Significant progress has been made on addressing critical issues for inertial fusion energy (IFE) chambers for heavy-ion, laser and Z-pinch drivers. A variety of chamber concepts are being investigated including drywall (currently favored for laser IFE), wetted-wall (applicable to both laser and ion drivers), and thick-liquid-wall (favored by heavy ion and z-pinch drivers). Recent progress and remaining challenges in developing IFE chambers are reviewed.

  4. Fluidized wall for protecting fusion chamber walls

    DOEpatents

    Maniscalco, James A.; Meier, Wayne R.

    1982-01-01

    Apparatus for protecting the inner wall of a fusion chamber from microexplosion debris, x-rays, neutrons, etc. produced by deuterium-tritium (DT) targets imploded within the fusion chamber. The apparatus utilizes a fluidized wall similar to a waterfall comprising liquid lithium or solid pellets of lithium-ceramic, the waterfall forming a blanket to prevent damage of the structural materials of the chamber.

  5. Free-Flow Open-Chamber Electrophoresis

    NASA Technical Reports Server (NTRS)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Free-flow open-chamber electrophoresis variant of free-flow electrophoresis performed in chamber with open ends and in which velocity of electro-osmotic flow adjusted equal to and opposite mean electrophoretic velocity of sample. Particles having electrophoretic mobilities greater than mean mobility of sample particles move toward cathode, those with mobilities less move toward anode. Technique applied to separation of components of mixtures of biologically important substances. Sensitivity enhanced by use of tapered chamber.

  6. Drift chamber tracking with neural networks

    SciTech Connect

    Lindsey, C.S.; Denby, B.; Haggerty, H.

    1992-10-01

    We discuss drift chamber tracking with a commercial log VLSI neural network chip. Voltages proportional to the drift times in a 4-layer drift chamber were presented to the Intel ETANN chip. The network was trained to provide the intercept and slope of straight tracks traversing the chamber. The outputs were recorded and later compared off line to conventional track fits. Two types of network architectures were studied. Applications of neural network tracking to high energy physics detector triggers is discussed.

  7. IFE Chamber Technology - Status and Future Challenges

    SciTech Connect

    Meier, W R; Raffrary, A R; Abdel-Khalik, S; Kulcinski, G; Latkowski, J F; Najmabadi, F; Olson, C L; Peterson, P F; Ying, A; Yoda, M

    2002-11-15

    Significant progress has been made on addressing critical issues for inertial fusion energy (IFE) chambers for heavy-ion, laser and Z-pinch drivers. A variety of chamber concepts are being investigated including dry-wall (currently favored for laser IFE), wetted-wall (applicable to both laser and ion drivers), and thick-liquid-wall favored by heavy ion and z-pinch drivers. Recent progress and remaining challenges in developing IFE chambers are reviewed.

  8. D0 central tracking chamber performance studies

    SciTech Connect

    Pizzuto, Domenico

    1991-12-01

    The performance of the completed DO central tracking chamber was studied using cosmic rays at the State University of New York at Stony Brook. Also studied was a prototype tracking chamber identical in design to the completed DO tracking chamber. The prototype chamber was exposed to a collimated beam of 150 GeV pions at the Fermilab NWA test facility. Results indicate an RΦ tracking resolution compatible with the limitations imposed by physical considerations, excellent 2 track resolution, and a high track reconstruction efficiency along with a good rejection power against γ → e + e- events.

  9. Engineering verification of the biomass production chamber

    NASA Technical Reports Server (NTRS)

    Prince, R. P.; Knott, W. M., III; Sager, J. C.; Jones, J. D.

    1992-01-01

    The requirements for life support systems, both biological and physical-chemical, for long-term human attended space missions are under serious study throughout NASA. The KSC 'breadboard' project has focused on biomass production using higher plants for atmospheric regeneration and food production in a special biomass production chamber. This chamber is designed to provide information on food crop growth rate, contaminants in the chamber that alter plant growth requirements for atmospheric regeneration, carbon dioxide consumption, oxygen production, and water utilization. The shape and size, mass, and energy requirements in relation to the overall integrity of the biomass production chamber are under constant study.

  10. Thrust chamber thermal barrier coating techniques

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.

    1988-01-01

    Methods for applying thermal barrier coatings to the hot-gas side wall of rocket thrust chambers in order to significantly reduce the heat transfer in high heat flux regions was the focus of technology efforts for many years. This paper describes a successful technique developed by the Lewis Research Center that starts with the coating of a mandrel and then builds the thrust chamber around it by electroforming appropriate materials. This results in a smooth coating with exceptional adherence, demonstrated in hot fire rig tests. The low cycle fatigue life of chambers with coatings applied in this manner was increased dramatically compared to uncoated chambers.

  11. Thrust chamber thermal barrier coating techniques

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.

    1989-01-01

    Methods for applying thermal barrier coatings to the hot-gas side wall of rocket thrust chambers in order to significantly reduce the heat transfer in high heat flux regions has been the focus of technology efforts for many years. A successful technique developed by NASA-Lewis that starts with the coating on a mandrel and then builds the thrust chamber around it by electroforming appropriate materials is described. This results in a smooth coating with exceptional adherence, as was demonstrated in hot fire rig tests. The low cycle fatigue life of chambers with coatings applied in this manner was increased dramatically compared to uncoated chambers.

  12. The Mark II Vertex Drift Chamber

    SciTech Connect

    Alexander, J.P.; Baggs, R.; Fujino, D.; Hayes, K.; Hoard, C.; Hower, N.; Hutchinson, D.; Jaros, J.A.; Koetke, D.; Kowalski, L.A.

    1989-03-01

    We have completed constructing and begun operating the Mark II Drift Chamber Vertex Detector. The chamber, based on a modified jet cell design, achieves 30 {mu}m spatial resolution and <1000 {mu}m track-pair resolution in pressurized CO{sub 2} gas mixtures. Special emphasis has been placed on controlling systematic errors including the use of novel construction techniques which permit accurate wire placement. Chamber performance has been studied with cosmic ray tracks collected with the chamber located both inside and outside the Mark II. Results on spatial resolution, average pulse shape, and some properties of CO{sub 2} mixtures are presented. 10 refs., 12 figs., 1 tab.

  13. Correlation of local structure peculiarities and critical current density of 2G MOCVD YBCO tapes with BaZrO3 nanoinclusions

    NASA Astrophysics Data System (ADS)

    Menushenkov, A. P.; Ivanov, V. G.; Chepikov, V. N.; Nygaard, R. R.; Soldatenko, A. V.; Rudnev, I. A.; Osipov, M. A.; Mineev, N. A.; Kaul, A. R.; Mathon, O.; Monteseguro, V.

    2017-04-01

    We have studied the influence of BaZrO3 nanoinclusions on the local structure and critical current density of second-generation high temperature superconducting tapes based on YBa2Cu3O7‑δ (YBCO) films. The films were made by metal–organic chemical vapor deposition (MOCVD). The crystal and local structure of the materials under study were analysed by x-ray diffraction and x-ray absorption spectroscopy (EXAFS + XANES). We have found that, being added at MOCVD process, Zr forms BaZrO3 nanoinclusions in YBCO matrix. The distance between Zr and the neighboring atoms is shorter than that one in a bulk crystalline BaZrO3, so we conclude that the nanoinclusions are in compressed state. The incorporation of 5 mol% BaZrO3 minimizes the static disorder of Cu–O bonds and maximizes their stiffness in YBCO. We show that the local structure peculiarities correlate well with the observed critical current behavior and consider this to be additional evidence in favor of small amounts of BaZrO3 nanoinclusions as efficient pinning centers.

  14. MOCVD growth and characterization of multi-stacked InAs/GaAs quantum dots on misoriented Si(100) emitting near 1.3 μm

    NASA Astrophysics Data System (ADS)

    Liu, Hao; Wang, Qi; Chen, Jia; Liu, Kai; Ren, Xiaomin

    2016-12-01

    We report near 1.3 μm strong photoluminescence (PL) emission from 5-stacked InAs/GaAs quantum dots (QDs) monolithically grown on Si (1 0 0) substrates with 4° miscut towards [110] direction by metal organic chemical vapor deposition (MOCVD). The metamorphic QD samples on Si were grown by three-step method, in which bottom Al0.8Ga0.2As cladding and GaAs waveguide layers were simultaneously incorporated in order to fabricate Si-based QD light emitting devices later. In particular, the GaAs waveguide layer grown with low and high temperature alternated significantly suppresses the upwards propagating of threading dislocations (TDs) into QD region and flattens the surface for latter adjacent nucleation of QDs. As a result, room-temperature photoluminescence intensity of as-grown Si-based InAs/GaAs QD sample attains 87% of that on GaAs and its PL peak as long as 1280 nm with the full width at half maximum value up to 78 nm (i.e., 60 meV). Our study shows the great opportunity of using MOCVD grown Si-based metamorphic QDs for 1.3 μm band light emitting devices.

  15. Raymond J. Chambers--A Personal Reflection

    ERIC Educational Resources Information Center

    Gaffikin, Michael

    2012-01-01

    This paper is presented as a tribute to Raymond J. Chambers. As its title suggests, it is a personal reflection through the eyes of someone who worked closely with him over a period of 10 years during a latter part of his career, and who completed a doctoral thesis with aspects of the work of Chambers as its subject. During this time, author…

  16. Incinerator system arrangement with dual scrubbing chambers

    SciTech Connect

    Domnitch, I.

    1987-01-13

    An incinerator arrangement is described comprising: an incinerator housing located near the lowest point in a building, the housing containing incinerator elements therein; a chute-flue having a first end in communication with the incinerator housing, a second end at the top of the building for evacuation of combustion gases to the atmosphere therethrough, and at least one intermediately located waste disposal opening through which waste is dropped into the incinerator housing; the incinerator elements including: a main combustion chamber, an opening between the main combustion chamber and the first end of the chute-flue and a flue-damper covering the opening. The flue-damper is biased in a closed position and being operable by the weight of waste to admit the waste into the combustion chamber; a scrubbing chamber located exteriorly along the top of the combustion chamber and having a first opening into the combustion chamber and a second opening into the chute-flue; and water spraying means in the scrubbing chamber for directing a water spray at the combustion gases to wash particulate matter from the gases before the gases enter the chute-flue whereby the water spraying means which are located adjacent the combustion chamber are protected against freezing and the elements.

  17. Studying Phototropism Using a Small Growth Chamber.

    ERIC Educational Resources Information Center

    Fisher, Maryanna, F.; Llewellyn, Gerald C.

    1978-01-01

    Describes a simple and inexpensive way to construct two small growth chambers for studying phototropism in the science classroom. One chamber is designed to illustrate how plants grow around obstacles to reach light and the other to illustrate directional light responses. (HM)

  18. Space Power Facility Reverberation Chamber Calibration Report

    NASA Technical Reports Server (NTRS)

    Lewis, Catherine C.; Dolesh, Robert J.; Garrett, Michael J.

    2014-01-01

    This document describes the process and results of calibrating the Space Environmental Test EMI Test facility at NASA Plum Brook Space Power Facility according to the specifications of IEC61000-4-21 for susceptibility testing from 100 MHz to 40 GHz. The chamber passed the field uniformity test, in both the empty and loaded conditions, making it the world's largest Reverberation Chamber.

  19. Raymond J. Chambers--A Personal Reflection

    ERIC Educational Resources Information Center

    Gaffikin, Michael

    2012-01-01

    This paper is presented as a tribute to Raymond J. Chambers. As its title suggests, it is a personal reflection through the eyes of someone who worked closely with him over a period of 10 years during a latter part of his career, and who completed a doctoral thesis with aspects of the work of Chambers as its subject. During this time, author…

  20. 21 CFR 866.2120 - Anaerobic chamber.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Anaerobic chamber. 866.2120 Section 866.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2120 Anaerobic chamber. (a...

  1. 21 CFR 866.2120 - Anaerobic chamber.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Anaerobic chamber. 866.2120 Section 866.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2120 Anaerobic chamber. (a...

  2. 21 CFR 866.2120 - Anaerobic chamber.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Anaerobic chamber. 866.2120 Section 866.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2120 Anaerobic chamber. (a...

  3. Promoting "Minds-on" Chamber Music Rehearsals

    ERIC Educational Resources Information Center

    Berg, Margaret H.

    2008-01-01

    Chamber music provides myriad opportunities to develop students' ability to think like professional musicians while engaged in the authentic task of working closely with and learning from peers. However, the potential for musical growth inherent in chamber music participation is often unrealized due to either a lack of teacher guidance and support…

  4. 21 CFR 868.5470 - Hyperbaric chamber.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... hyperbaric chamber is a device that is intended to increase the environmental oxygen pressure to promote the movement of oxygen from the environment to a patient's tissue by means of pressurization that is greater than atmospheric pressure. This device does not include topical oxygen chambers for extremities (§...

  5. 21 CFR 868.5470 - Hyperbaric chamber.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... hyperbaric chamber is a device that is intended to increase the environmental oxygen pressure to promote the movement of oxygen from the environment to a patient's tissue by means of pressurization that is greater than atmospheric pressure. This device does not include topical oxygen chambers for extremities (§...

  6. 21 CFR 868.5470 - Hyperbaric chamber.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... hyperbaric chamber is a device that is intended to increase the environmental oxygen pressure to promote the movement of oxygen from the environment to a patient's tissue by means of pressurization that is greater than atmospheric pressure. This device does not include topical oxygen chambers for extremities (§...

  7. 21 CFR 868.5470 - Hyperbaric chamber.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... hyperbaric chamber is a device that is intended to increase the environmental oxygen pressure to promote the movement of oxygen from the environment to a patient's tissue by means of pressurization that is greater than atmospheric pressure. This device does not include topical oxygen chambers for extremities (§...

  8. 21 CFR 866.2120 - Anaerobic chamber.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Anaerobic chamber. 866.2120 Section 866.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2120 Anaerobic chamber. (a...

  9. 21 CFR 866.2120 - Anaerobic chamber.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Anaerobic chamber. 866.2120 Section 866.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2120 Anaerobic chamber. (a...

  10. MOCVD Grown InP and Related Thin Films on Silicon Substrates for Electron and Photonic Devices Applications

    NASA Astrophysics Data System (ADS)

    Zhong, Zhenyu

    Heterogeneous integration of III-V compound semiconductor with silicon is attracting renewed attention in recent years due to its potential in electronic and photonic applications. For electronic applications, a robust integration allows low-voltage and high-speed III-V based transistors to couple with mature silicon-based technologies for functional circuit blocks. Several successful demonstrations have been achieved by molecular beam epitaxy (MBE). In regard to photonic applications, silicon photonics is an important area of research with its possible replacement of copper interconnects. The well-developed III-V photonic devices can be utilized on a silicon platform if a seamless integration can be realized. This concept has been extensively demonstrated by wafer bonding, whereas the manufacturing complexity, reliability and yield are main challenges in this transfer technique. In this thesis, demonstration of heterogeneous integration of III-V based electron and photonic devices on silicon substrates is described, using Metal organic chemical vapor deposition (MOCVD), which is considered more compatible with CMOS processes with good potential for wafer level manufacturing. In this work, InP thin films with smooth surface morphology were firstly achieved by introducing thin GaAs buffer layers. The GaAs buffer was optimized based on the surface morphology, crystalline quality and in situ RAS signal. The total thickness of the buffer layer was finally reduced to 1.2mum by trimming the GaAs buffers as a thin buffer is more desirable for process integration. On top of the thin InP buffer layers, high performance metamorphic high electron mobility transistors (mHEMTs) have been demonstrated for the first time. To implement photonic devices on the buffers, the epitaxial films quality was further improved utilizing novel post-treatment techniques, including thermal process and strained layers for defects reduction. InGaAs p-i-n photodetectors lattice-matched to In

  11. High and Low Energy Proton Radiation Damage in p/n InP MOCVD Solar Cells

    NASA Technical Reports Server (NTRS)

    Rybicki, George; Weinberg, Irv; Scheiman, Dave; Vargas-Aburto, Carlos; Uribe, Roberto

    1995-01-01

    InP p(+)/n/n(+) solar cells, fabricated by metal organic chemical vapor deposition, (MOCVD) were irradiated with 0.2 MeV and 10 MeV protons to a fluence of 10(exp 13)/sq cm. The power output degradation, IV behavior, carrier concentration and defect concentration were observed at intermediate points throughout the irradiations. The 0.2 MeV proton-irradiated solar cells suffered much greater and more rapid degradation in power output than those irradiated with 10 MeV protons. The efficiency losses were accompanied by larger increases in the recombination currents in the 0.2 MeV proton-irradiated solar cells. The low energy proton irradiations also had a larger impact on the series resistance of the solar cells. Despite the radiation induced damage, the carrier concentration in the base of the solar cells showed no reduction after 10 MeV or 0.2 MeV proton irradiations and even increased during irradiation with 0.2 MeV protons. In a deep level transient spectroscopy (DLTS) study of the irradiated samples, the minority carrier defects H4 and H5 at E(sub v) + 0.33 and E(sub v) + 0.52 eV and the majority carrier defects E7 and El0 at E(sub c) - 0.39 and E(sub c) - 0.74 eV, were observed. The defect introduction rates for the 0.2 MeV proton irradiations were about 20 times higher than for the 10 MeV proton irradiations. The defect El0, observed here after irradiation, has been shown to act as a donor in irradiated n-type InP and may be responsible for obscuring carrier removal. The results of this study are consistent with the much greater damage produced by low energy protons whose limited range causes them to stop in the active region of the solar cell.

  12. Preparation of ZnO:CeO{sub 2-x} thin films by AP-MOCVD: Structural and optical properties

    SciTech Connect

    Torres-Huerta, A.M.; Dominguez-Crespo, M.A.; Brachetti-Sibaja, S.B.; Dorantes-Rosales, H.; Hernandez-Perez, M.A.; Lois-Correa, J.A.

    2010-09-15

    The growth of columnar CeO{sub 2}, ZnO and ZnO:CeO{sub 2-x} films on quartz and AA6066 aluminum alloy substrates by economic atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) is reported. A novel and efficient combination of metal acetylacetonate precursors as well as mild operating conditions were used in the deposition process. The correlation among crystallinity, surface morphology and optical properties of the as-prepared films was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV-vis spectroscopy. The synthesized films showed different crystallographic orientations depending on the ZnO and CeO{sub 2} lattice mismatch, cerium content and growth rate. The CeO{sub 2} films synthesized in this work showed plate-like compact structures as a result of the growth process typical of CVD. Both pure and ZnO:CeO{sub 2-x} films were obtained with a hexagonal structure and highly preferred orientation with the c-axis perpendicular to both substrates under the optimal deposition conditions. The microstructure was modified from dense, short round columns to round structures with cavities ('rose-flower-like' structures) and the typical ZnO morphology by controlling the cerium doping the film and substrate nature. High optical transmittance (>87%) was observed in the pure ZnO films. As for the ZnO:CeO{sub 2-x} films, the optical transmission was decreased and the UV absorption increased, which subsequently was affected by an increase in cerium content. This paper assesses the feasibility of using ZnO:CeO{sub 2-x} thin films as UV-absorbers in industrial applications. - Graphical abstract: TEM micrographs and their corresponding SAED pattern obtained for the as-deposited ZnO-CeO{sub 2-x} thin films for a Zn/Ce metallic ratio 16:9.

  13. Compact ion chamber based neutron detector

    DOEpatents

    Derzon, Mark S.; Galambos, Paul C.; Renzi, Ronald F.

    2015-10-27

    A directional neutron detector has an ion chamber formed in a dielectric material; a signal electrode and a ground electrode formed in the ion chamber; a neutron absorbing material filling the ion chamber; readout circuitry which is electrically coupled to the signal and ground electrodes; and a signal processor electrically coupled to the readout circuitry. The ion chamber has a pair of substantially planar electrode surfaces. The chamber pressure of the neutron absorbing material is selected such that the reaction particle ion trail length for neutrons absorbed by the neutron absorbing material is equal to or less than the distance between the electrode surfaces. The signal processor is adapted to determine a path angle for each absorbed neutron based on the rise time of the corresponding pulse in a time-varying detector signal.

  14. Anechoic chamber qualification at ultrasonic frequencies

    NASA Astrophysics Data System (ADS)

    Jenny, Trevor; Anderson, Brian

    2010-10-01

    Qualifying an anechoic chamber for frequencies that extend into the ultrasonic range is necessary for research work involving airborne ultrasonic sound. For example, an anechoic chamber allows for measurements of the direct sound radiated by an object without reflections from walls. The ANSI S12.55/ISO 3745 standard which covers anechoic chamber qualification does not extend into the ultrasonic frequency range, nor have others discussed this frequency range in the literature. An increasing number of technologies are employing ultrasound; hence the need to develop facilities to conduct basic research studies on airborne ultrasound. This presentation will discuss the challenges associated with chamber qualification and present the results for qualification of a chamber at Brigham Young University. [This work has been funded by the Los Alamos National Laboratory

  15. Ionization-chamber smoke detector system

    DOEpatents

    Roe, Robert F.

    1976-10-19

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system is designed to reduce false alarms caused by fluctuations in ambient temperature. Means are provided for periodically firing the gas discharge triode and each time recording the triggering voltage required. A computer compares each triggering voltage with its predecessor. The computer is programmed to energize an alarm if the difference between the two compared voltages is a relatively large value indicative of particulates in the measuring chamber and to disregard smaller differences typically resulting from changes in ambient temperature.

  16. Note: Small anaerobic chamber for optical spectroscopy

    SciTech Connect

    Chauvet, Adrien A. P. Chergui, Majed; Agarwal, Rachna; Cramer, William A.

    2015-10-15

    The study of oxygen-sensitive biological samples requires an effective control of the atmosphere in which they are housed. In this aim however, no commercial anaerobic chamber is adequate to solely enclose the sample and small enough to fit in a compact spectroscopic system with which analysis can be performed. Furthermore, spectroscopic analysis requires the probe beam to pass through the whole chamber, introducing a requirement for adequate windows. In response to these challenges, we present a 1 l anaerobic chamber that is suitable for broad-band spectroscopic analysis. This chamber has the advantage of (1) providing access, via a septum, to the sample and (2) allows the sample position to be adjusted while keeping the chamber fixed and hermetic during the experiment.

  17. Advanced tube-bundle rocket thrust chamber

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Pavli, Albert J.

    1990-01-01

    An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

  18. An atmospheric exposure chamber for small animals

    NASA Technical Reports Server (NTRS)

    Glaser, R. M.; Weiss, H. S.; Pitt, J. F.; Grimard, M.

    1982-01-01

    The purpose of this project was to design a long-term environmental exposure chamber for small animals. This chamber is capable of producing hypoxic, normoxic and hyperoxic atmospheres which are closely regulated. The chamber, which is of the recycling type, is fashioned after clear plastic germ-free isolators. Oxygen concentration is set and controlled by a paramagnetic O2 analyzer and a 3-way solenoid valve. In this way either O2 or N2 may be provided to the system by way of negative O2 feedback. Relative humidity is maintained at 40-50 percent by a refrigeration type dryer. Carbon dioxide is absorbed by indicating soda lime. A diaphragm pump continuously circulates chamber gas at a high enough flow rate to prevent buildup of CO2 and humidity. This chamber has been used for numerous studies which involve prolonged exposure of small animals to various O2 concentrations.

  19. Multispecimen dual-beam irradiation damage chamber

    SciTech Connect

    Packan, N.H.; Buhl, R.A.

    1980-06-01

    An irradiation damage chamber that can be used to rapidly simulate fast neutron damage in fission or fusion materials has been designed and constructed. The chamber operates in conjunction with dual Van de Graaff accelerators at ORNL to simulate a wide range of irradiation conditions, including pulsed irradiation. Up to six experiments, each with up to nine 3-mm disk specimens, can be loaded into the ultrahigh vacuum chamber. Specimen holders are heated with individual electron guns, and the temperature of each specimen can be monitored during bombardment by an infrared pyrometer. Three different dose levels may be obtained during any single bombardment, and the heavy-ion flux on each of the nine specimens can be measured independently with only a brief interruption of the beam. The chamber has been in service for nearly three years, during which time approximately 250 bombardments have been successfully carried out. An appendix contains detailed procedures for operating the chamber.

  20. Advanced tube-bundle rocket thrust chamber

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Pavli, Albert J.

    1990-01-01

    An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

  1. An atmospheric exposure chamber for small animals

    NASA Technical Reports Server (NTRS)

    Glaser, R. M.; Weiss, H. S.; Pitt, J. F.; Grimard, M.

    1982-01-01

    The purpose of this project was to design a long-term environmental exposure chamber for small animals. This chamber is capable of producing hypoxic, normoxic and hyperoxic atmospheres which are closely regulated. The chamber, which is of the recycling type, is fashioned after clear plastic germ-free isolators. Oxygen concentration is set and controlled by a paramagnetic O2 analyzer and a 3-way solenoid valve. In this way either O2 or N2 may be provided to the system by way of negative O2 feedback. Relative humidity is maintained at 40-50 percent by a refrigeration type dryer. Carbon dioxide is absorbed by indicating soda lime. A diaphragm pump continuously circulates chamber gas at a high enough flow rate to prevent buildup of CO2 and humidity. This chamber has been used for numerous studies which involve prolonged exposure of small animals to various O2 concentrations.

  2. Aging in large CDF tracking chambers

    SciTech Connect

    M. Binkley et al.

    2001-03-19

    The experience of the Collider Detector at Fermilab (CDF) with aging in the large axial drift chamber responsible for tracking in the central region is presented. Premature aging in the Run 1 chamber was observed after only 0.02 C/cm. After cleaning much of the gas system and making modifications to reduce aerosols from the alcohol bubbler, the observed aging rate fell dramatically in test chambers. Considerable effort has been made to better understand the factors that affect aging since the replacement chamber for Run 2 will accumulate about 1.0 C/cm. Current test chambers using the full CDF gas system show aging rates of less than 5%/C/cm.

  3. Signal propagation in long wire chambers

    NASA Astrophysics Data System (ADS)

    Bock, P.; Engelfried, J.; Friedrich, T.; Heintze, J.; Lennert, P.; Russ, M.; Zimmer, M.

    2012-09-01

    The propagation of signals in long proportional counters or multi-wire tracking chambers is simulated, using numerical solutions of the multi-wire telegraph equations. The results are compared to experimental data, recorded with a proportional counter and a multi-wire test chamber. The signal shape, the charge division ratio and, in the case of the drift chamber, also the cross talk between the wires, are well reproduced. Similar shapes for signals and their cross talk can be obtained with a properly chosen electrical termination. It is shown how data from a multi-wire chamber can then be corrected for cross talk. The effects limiting the precision of position measurements along the wires with the charge division method are discussed. The simulation was applied to the reconstruction of tracks measured with the OPAL JET chamber.

  4. Note: Small anaerobic chamber for optical spectroscopy.

    PubMed

    Chauvet, Adrien A P; Agarwal, Rachna; Cramer, William A; Chergui, Majed

    2015-10-01

    The study of oxygen-sensitive biological samples requires an effective control of the atmosphere in which they are housed. In this aim however, no commercial anaerobic chamber is adequate to solely enclose the sample and small enough to fit in a compact spectroscopic system with which analysis can be performed. Furthermore, spectroscopic analysis requires the probe beam to pass through the whole chamber, introducing a requirement for adequate windows. In response to these challenges, we present a 1 l anaerobic chamber that is suitable for broad-band spectroscopic analysis. This chamber has the advantage of (1) providing access, via a septum, to the sample and (2) allows the sample position to be adjusted while keeping the chamber fixed and hermetic during the experiment.

  5. The SAMURAI Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Dye, Steven

    2011-10-01

    The SAMURAI Time Projection Chamber (TPC) will be used to study particle collisions by colliding a beam of particles with a stationary gas which will be contained in a field cage inside the TPC. When the beam collides with the gas, charged particles are accelerated into the pad plane by an electric field. The paths of these particles will be curved by a magnetic field created by the SAMURAI magnet at the RIKEN facility in Japan. The charged particles will then collide with the pad plane which will be located on the bottom of the TPC. The pad plane will take these collisions and create electrical signals and send them to supporting electronics where the data can be interpreted. The TPC will be used to help determine the Equation of State for asymmetric nuclear matter. Measurements of neutron, proton, 3H and 3He flow will be taken with the NEBULA array which consists of nebula scintillators. The poster will contain information on the laser calibration system and the electronics that will be used for the TPC. The electronics used are the same electronics used in the STAR TPC experiment.

  6. RADIATION MONITOR CONTAINING TWO CONCENTRIC IONIZATION CHAMBERS AND MEANS FOR INSULATING THE SEPARATE CHAMBERS

    DOEpatents

    Braestrup, C.B.; Mooney, R.T.

    1964-01-21

    This invention relates to a portable radiation monitor containing two concentric ionization chambers which permit the use of standard charging and reading devices. It is particularly adapted as a personnel x-ray dosimeter and to this end comprises a small thin walled, cylindrical conductor forming an inner energy dependent chamber, a small thin walled, cylindrical conductor forming an outer energy independent chamber, and polymeric insulation means which insulates said chambers from each other and holds the chambers together with exposed connections in a simple, trouble-free, and compact assembly substantially without variation in directional response. (AEC)

  7. The biocompatibility of titanium in a buffer solution: compared effects of a thin film of TiO2 deposited by MOCVD and of collagen deposited from a gel.

    PubMed

    Popescu, Simona; Demetrescu, Ioana; Sarantopoulos, Christos; Gleizes, Alain N; Iordachescu, Dana

    2007-10-01

    This study aims at evaluating the biocompatibility of titanium surfaces modified according two different ways: (i) deposition of a bio-inert, thin film of rutile TiO(2) by chemical vapour deposition (MOCVD), and (ii) biochemical treatment with collagen gel, in order to obtain a bio-interactive coating. Behind the comparison is the idea that either the bio-inert or the bio-active coating has specific advantages when applied to implant treatment, such as the low price of the collagen treatment for instance. The stability in buffer solution was evaluated by open circuit potential (OCP) for medium time and cyclic voltametry. The OCP stabilized after 5.10(4) min for all the specimens except the collagen treated sample which presented a stable OCP from the first minutes. MOCVD treated samples stabilized to more electropositive values. Numeric results were statistically analysed to obtain the regression equations for long time predictable evolution. The corrosion parameters determined from cyclic curves revealed that the MOCVD treatment is an efficient way to improve corrosion resistance. Human dermal fibroblasts were selected for cell culture tests, taking into account that these cells are present in all bio-interfaces, being the main cellular type of connective tissue. The cells grew on either type of surface without phenotype modification. From the reduction of yellow, water-soluble 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT cytotoxicity test), MOCVD treated samples offer better viability than mechanically polished Ti and collagen treated samples as well. Cell spreading, as evaluated from microscope images processed by the program Sigma Scan, showed also enhancement upon surface modification. Depending on the experimental conditions, MOCVD deposited TiO(2) exhibits different nanostructures that may influence biological behaviour. The results demonstrate the capacity of integration in simulated physiologic liquids for an implant pretreated by

  8. The emulsion chamber technology experiment

    NASA Technical Reports Server (NTRS)

    Gregory, John C.

    1992-01-01

    Photographic emulsion has the unique property of recording tracks of ionizing particles with a spatial precision of 1 micron, while also being capable of deployment over detector areas of square meters or 10's of square meters. Detectors are passive, their cost to fly in Space is a fraction of that of instruments of similar collecting. A major problem in their continued use has been the labor intensiveness of data retrieval by traditional microscope methods. Two factors changing the acceptability of emulsion technology in space are the astronomical costs of flying large electronic instruments such as ionization calorimeters in Space, and the power and low cost of computers, a small revolution in the laboratory microscope data-taking. Our group at UAH made measurements of the high energy composition and spectra of cosmic rays. The Marshall group has also specialized in space radiation dosimetry. Ionization calorimeters, using alternating layers of lead and photographic emulsion, to measure particle energies up to 10(exp 15) eV were developed. Ten balloon flights were performed with them. No such calorimeters have ever flown in orbit. In the ECT program, a small emulsion chamber was developed and will be flown on the Shuttle mission OAST-2 to resolve the principal technological questions concerning space exposures. These include assessments of: (1) pre-flight and orbital exposure to background radiation, including both self-shielding and secondary particle generation; the practical limit to exposure time in space can then be determined; (2) dynamics of stack to optimize design for launch and weightlessness; and (3) thermal and vacuum constraints on emulsion performance. All these effects are cumulative and affect our ability to perform scientific measurements but cannot be adequately predicted by available methods.

  9. The Japanese Radon and Thoron Reference Chambers

    SciTech Connect

    Tokonami, Shinji; Ishikawa, Tetsuo; Sorimachi, Atsuyuki; Takahashi, Hiroyuki; Miyahara, Nobuyuki

    2008-08-07

    Passive detectors used for large-scale and long-term surveys are generally calibrated in a well-controlled environment such as a radon chamber. It has been also pointed out that some of them are sensitive to thoron. Thus it is necessary to check the thoron contribution to the detector response with the proposed or similar test before practical use. The NIRS accommodates radon/aerosol and thoron chambers for quality assurance and quality control of radon measurements. Thus both chambers work so well that they can supply us with the calibration technique and consequently, a good level of knowledge of the radon and thoron issue.

  10. Sample chambers with mother-daughter mode

    SciTech Connect

    Wilk, P.A.; Gregorich, K.E.; Hoffman, D.C.

    2001-07-12

    A set of eight stand-alone sample chambers with a common interface were constructed at LBNL for improved detection of alpha and fission decay chains over currently used designs. The stainless steel chambers (see Figure 1 for a schematic and Figure 2 for a photograph of a completed chamber) were constructed to allow for low background detection of a daughter event by removal of the sample following the detection of a parent event. This mother-daughter mode of operation has been utilized successfully with our Merry-go-Round (MG) detection system [Gregorich 1994].

  11. Performance of NIRS Thoron Chamber System

    NASA Astrophysics Data System (ADS)

    Sorimachi, Atsuyuki; Tokonami, Shinji; Takahashi, Hiroyuki; Kobayashi, Yosuke

    2008-08-01

    In order to carry out thoron sensitivity test for passive radon detectors, a thoron chamber system has been set up at NIRS, Japan. The thoron chamber system consists of four components: the exposure, monitoring, calibration, and humidity control systems, which was mounted in this study due to humidity dependence on the thoron concentration emanated from lantern mantles as the thoron source. The thoron concentration in the thoron chamber is controlled by humidity passed through the thoron source and the weight of the lantern mantle.

  12. Performance of NIRS Thoron Chamber System

    SciTech Connect

    Sorimachi, Atsuyuki; Tokonami, Shinji; Takahashi, Hiroyuki; Kobayashi, Yosuke

    2008-08-07

    In order to carry out thoron sensitivity test for passive radon detectors, a thoron chamber system has been set up at NIRS, Japan. The thoron chamber system consists of four components: the exposure, monitoring, calibration, and humidity control systems, which was mounted in this study due to humidity dependence on the thoron concentration emanated from lantern mantles as the thoron source. The thoron concentration in the thoron chamber is controlled by humidity passed through the thoron source and the weight of the lantern mantle.

  13. Test stand system for vacuum chambers

    NASA Technical Reports Server (NTRS)

    Newman, D. F. (Inventor)

    1973-01-01

    A test stand system for supporting test items in a vacuum chamber is described. The system consists of a frame adapted to conform to the inside of the vacuum chamber and supporting a central vertical shaft. The shaft rotates on bearings located at each end of the shaft. Several vertically spaced plates which fixed to the vertical shaft may be adjusted for height to support the test equipment as required. The test equipment may be rotated during tests without disturbing the vacuum by a manually actuated drive external to the vacuum chamber.

  14. APS Storage Ring vacuum chamber fabrication

    SciTech Connect

    Goeppner, G.A.

    1990-01-01

    The 1104-m circumference Advanced Photon Source Storage Ring Vacuum System is composed of 240 individual sections, which are fabricated from a combination of aluminum extrusions and machined components. The vacuum chambers will have 3800 weld joints, each subject to strict vacuum requirements, as well as a variety of related design criteria. The vacuum criteria and chamber design are reviewed, including a discussion of the weld joint geometries. The critical fabrication process parameters for meeting the design requirements are discussed. The experiences of the prototype chamber fabrication program are presented. Finally, the required facilities preparation for construction activity is briefly described. 6 refs., 6 figs., 1 tab.

  15. Filling arrangement for coke oven chambers

    SciTech Connect

    Galow, M.

    1984-03-27

    An arrangement for filling at least one coke oven chamber has a transport device arranged to transport coal, a chute member located under the transport device to guide coal to a filling opening of the coke oven chamber, at least one closing member arranged between the chute member and the filling opening of the coke oven chamber, and a sliding plate moveable in a housing above the chute member between open and closed positions, wherein the sliding plate and the housing in its region in which the sliding plate is in its open position are inclined toward a horizontal.

  16. Simple cloud chambers using gel ice packs

    NASA Astrophysics Data System (ADS)

    Kamata, Masahiro; Kubota, Miki

    2012-07-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry ice or liquid nitrogen. The gel can be frozen in normal domestic freezers, and can be used repeatedly by re-freezing. The tracks of alpha-ray particles can be observed continuously for about 20 min, and the operation is simple and easy.

  17. 30 CFR 77.305 - Access to drying chambers, hot gas inlet chambers and ductwork; installation and maintenance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... chambers and ductwork; installation and maintenance. 77.305 Section 77.305 Mineral Resources MINE SAFETY... drying chambers, hot gas inlet chambers and ductwork; installation and maintenance. Drying chambers, hot gas inlet chambers and all ductwork in which coal dust may accumulate shall be equipped with...

  18. DETAIL OF THE GROOVED RIM ON TOP FACE OF CHAMBER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF THE GROOVED RIM ON TOP FACE OF CHAMBER SHELL, ALTITUDE CHAMBER L, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  19. 11. Detail view west from airlock chamber of typical refrigerator ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Detail view west from airlock chamber of typical refrigerator door into Trophic Chamber. - Natick Research & Development Laboratories, Climatic Chambers Building, U.S. Army Natick Research, Development & Engineering Center (NRDEC), Natick, Middlesex County, MA

  20. HYLIFE-II reactor chamber design refinements

    SciTech Connect

    House, P.A.

    1994-06-01

    Mechanical design features of the reactor chamber for the HYLIFE-II inertial confinement fusion power plant are presented. A combination of oscillating and steady, molten salt streams (Li{sub 2}BeF{sub 4}) are used for shielding and blast protection of the chamber walls. The system is designed for a 6 Hz repetition rate. Beam path clearing, between shots, is accomplished with the oscillating flow. The mechanism for generating the oscillating streams is described. A design configuration of the vessel wall allows adequate cooling and provides extra shielding to reduce thermal stresses to tolerable levels. The bottom portion of the reactor chamber is designed to minimize splash back of the high velocity (>12 m/s) salt streams and also recover up to half of the dynamic head. Cost estimates for a 1 GWe and 2 GWe reactor chamber are presented.

  1. LDCM TIRS: Cracking open the chamber

    NASA Image and Video Library

    Engineers at Goddard Space Flight Center inspect and move the Thermal Infrared Sensor (TIRS) after two months of testing in the thermal vacuum chamber. TIRS completed its first round of thermal vac...

  2. Aeroacoustic sound generation in simple expansion chambers.

    PubMed

    English, Emmet J; Holland, Keith R

    2010-11-01

    A method is presented for measuring the aeroacoustic source strength in ducts with flow at frequencies at which the wave motion can be considered substantially one-dimensional. The method is based on coherent power flux measurements using pairs of microphones positioned both upstream and downstream of the source region. The method is applied to a flow excited expansion chamber with aeroacoustic source measurements presented for chambers with a range of flow velocities and chamber lengths. The results indicate locked-on flow tones are generated in the chamber. The frequency of these locked-on flow tones is compared with that predicted using describing function theory applied to resonators with a grazing flow as well as that of other literature.

  3. Developing Cloud Chambers with High School Students

    NASA Astrophysics Data System (ADS)

    Ishizuka, Ryo; Tan, Nobuaki; Sato, Shoma; Zeze, Syoji

    The result and outcome of the cloud chamber project, which aims to develop a cloud chamber useful for science education is reported in detail. A project includes both three high school students and a teacher as a part of Super Science High School (SSH) program in our school. We develop a dry-ice-free cloud chamber using salt and ice (or snow). Technical details of the chamber are described. We also argue how the project have affected student's cognition, motivation, academic skills and behavior. The research project has taken steps of professional researchers, i.e., in planning research, applying fund, writing a paper and giving a talk in conferences. From interviews with students, we have learnt that such style of scientific activity is very effective in promoting student's motivation for learning science.

  4. The structure of BaCu 3O 4 particles occurring on thin HoBa 2Cu 3O 7 films prepared by MOCVD

    NASA Astrophysics Data System (ADS)

    Zandbergen, H. W.; Jansen, J.; Svetchnikov, V. L.; Graboy, I. E.; Samoylenkov, S.; Gorbenko, O.; Kaul, A. R.

    1999-12-01

    The structure of BaCu 3O 4 phase occurring as particles on the surface of (001) RBa 2Cu 3O 7 epitaxial films prepared by metalorganic chemical vapor deposition (MOCVD) has been investigated with quantitative electron diffraction and HREM. The orthorhombic unit cell is a=1.097(9) nm, b=0.554(3) nm, c=0.394(2) nm with space group Cmmm, the values being in agreement with X-ray diffraction (XRD) study. The structure consists of alternating Cu 3O 4 and Ba layers along the c-axis. The compound is stabilised due to the formation of low-energy coherent boundaries with RBa 2Cu 3O 7 and/or perovskite substrate.

  5. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    SciTech Connect

    Mbamara, U. S.; Olofinjana, B.; Ajayi, O. O.; Lorenzo-Martin, C.; Obiajunwa, E. I.; Ajayi, E. O. B.

    2016-02-01

    Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS) and X-ray Diffraction (XRD). The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-face surfaces were examined to assess the wear dimension and failure mechanism. In conclusion, both friction behavior and wear (in the ball counter-face) were observed to be dependent on the crystallinity and thickness of the thin film coatings.

  6. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Growth and Characteristics of Epitaxial AlxGa1-xN by MOCVD

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Guo, Li-Wei; Chen, Yao; Xu, Pei-Qiang; Ding, Guo-Jian; Peng, Ming-Zeng; Jia, Hai-Qiang; Zhou, Jun-Ming; Chen, Hong

    2009-06-01

    AlxGa1-xN epilayers with a wide Al composition range (0.2 <= x <= 0.68) were grown on AlN/sapphire templates by low-pressure metalorganic chemical vapour deposition (LP-MOCVD). X-ray diffraction results reveal that both the (0002) and (10bar 15) full widths at half-maximum (FWHM) of the AlxGa1-xN epilayer decrease with increasing Al composition due to the smaller lattice mismatch to the AlN template. However, the surface morphology becomes rougher with increasing Al composition due to the weak migration ability of Al atoms. Low temperature photoluminescence (PL) spectra show pronounced near band edge (NBE) emission and the NBE FWHM becomes broader with increasing Al composition mainly caused by alloy disorder. Meanwhile, possible causes of the low energy peaks in the PL spectra are discussed.

  7. The use of metalorganics in the preparation of semiconductor materials. VIII - Feasibility studies of the growth of Group III-Group V compounds of boron by MOCVD

    NASA Technical Reports Server (NTRS)

    Manasevit, H. M.; Hewitt, W. B.; Nelson, A. J.; Mason, A. R.

    1989-01-01

    The MOCVD growth of B-As and B-P films on Si, sapphire, and Si-on-sapphire substrates is described; in this process, trimethylborane (TMB) or triethylborane (TEB) is pyrolyzed in the presence of AsH3 or PH3 in an H2 atmosphere. The procedures employed are outlined, and the results are presented in graphs, tables, and micrographs. It is found that the growth rate of the primarily amorphous films is dependent on the TMB or TEB concentration but approximately constant for TEB and AsH3 at 550-900 C. The nominal compositions of films grown using TMB are given as B(12-16)As2 and B(1-1.3)P. Carbon impurities and significant stress, bowing, and crazing are observed in the films grown on Si substrates, with the highest carbon content in the films grown from TMB and PH3.

  8. The use of metalorganics in the preparation of semiconductor materials. VIII - Feasibility studies of the growth of Group III-Group V compounds of boron by MOCVD

    NASA Technical Reports Server (NTRS)

    Manasevit, H. M.; Hewitt, W. B.; Nelson, A. J.; Mason, A. R.

    1989-01-01

    The MOCVD growth of B-As and B-P films on Si, sapphire, and Si-on-sapphire substrates is described; in this process, trimethylborane (TMB) or triethylborane (TEB) is pyrolyzed in the presence of AsH3 or PH3 in an H2 atmosphere. The procedures employed are outlined, and the results are presented in graphs, tables, and micrographs. It is found that the growth rate of the primarily amorphous films is dependent on the TMB or TEB concentration but approximately constant for TEB and AsH3 at 550-900 C. The nominal compositions of films grown using TMB are given as B(12-16)As2 and B(1-1.3)P. Carbon impurities and significant stress, bowing, and crazing are observed in the films grown on Si substrates, with the highest carbon content in the films grown from TMB and PH3.

  9. MOCVD of tungsten nitride (WN x) thin films from the imido complex Cl 4(CH 3CN)W(N iPr)

    NASA Astrophysics Data System (ADS)

    Bchir, Omar J.; Johnston, Steven W.; Cuadra, Amalia C.; Anderson, Timothy J.; Ortiz, Carlos G.; Brooks, Benjamin C.; Powell, David H.; McElwee-White, Lisa

    2003-02-01

    Thin films of tungsten nitride (WN x) were deposited by MOCVD from the single-source precursor Cl 4(CH 3CN)W(N iPr). Films were analyzed by X-ray diffraction (XRD), Auger electron spectroscopy (AES) and cross-section scanning electron microscopy (X-SEM), while the film resistivity was determined by four-point probe. Film growth rates ranged from 10 to 27 Å/min within a temperature range of 450-700°C. The apparent activation energy for film growth in the kinetically controlled regime was 0.84 eV. Films grown at temperatures below 500°C were amorphous, with minimum film resistivity and sheet resistance of 750 μΩ cm and 47 Ω/□, respectively, occurring for deposition at 450°C.

  10. ZnO-Based Transparent Thin-Film Transistors with MgO Gate Dielectric Grown by in-situ MOCVD

    NASA Astrophysics Data System (ADS)

    Zhao, Wang; Dong, Xin; Zhao, Long; Shi, Zhi-Feng; Wang, Jin; Wang, Hui; Xia, Xiao-Chuan; Chang, Yu-Chun; Zhang, Bao-Lin; Du, Guo-Tong

    2010-12-01

    ZnO transparent thin-film transistors with MgO gate dielectric were fabricated by in-situ metal organic chemical vapor deposition (MOCVD) technology. We used an uninterrupted growth method to simplify the fabrication steps and to avoid the unexpectable contaminating during epitaxy process. MgO layer is helpful to reduce the gate leakage current, as well as to achieve high transparency in visible light band, due to the wide band gap (7.7eV) and high dielectric constant (9.8). The XRD measurement indicates that the ZnO layer has high crystal quality. The field effect mobility and the on/off current ratio of the device is 2.69 cm2 V-1s-1 and ~ 1 × 104, respectively.

  11. Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE-MOCVD) for phase-change random access memory applications

    NASA Astrophysics Data System (ADS)

    Aoukar, M.; Szkutnik, P. D.; Jourde, D.; Pelissier, B.; Michallon, P.; Noé, P.; Vallée, C.

    2015-07-01

    Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced—metal organic chemical vapor deposition (PE-MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained.

  12. Influence of TBAs flow in MOCVD growth on nitrogen incorporation in GaAsN alloy and its optical quality detected by photoreflectance

    NASA Astrophysics Data System (ADS)

    Rudno-Rudzinski, W.; Kudrawiec, R.; Misiewicz, J.; Derluyn, J.; Moerman, I.

    2004-02-01

    In this work there has been studied GaNAs bulk layers grown by metal organic chemical vapour deposition (MOCVD) with different tributylarsine (TBAs) flow and the same flow of triethylgallium (TEGa) and unsymmetrical dimethyl-hydrazine (DMHy). High resolution X-ray diffraction (HR-XRD) and room temperature photoreflectance (PR) have been carried out in order to evaluate the nitrogen content and bandgap energy and quality of the GaAsN layer. It has been observed that the TBAs flow influences of the nitrogen incorporation. The variation of the TBAs from 37 to 1182 mol/min causes variation of nitrogen content in GaAsN layer in the range of 1.5-4 % . The best optical quality of GaAsN layer and the highest nitrogen incorporation have been found for the TBAs flow in the range of 296 and 591 mol/min.

  13. Effect of Al-mole fraction in Al{sub x}Ga{sub 1−x}N grown by MOCVD

    SciTech Connect

    Jayasakthi, M. Ramesh, R. Prabakaran, K. Loganathan, R. Kuppulingam, B. Balaji, M. Arivazhagan, P. Sankaranarayanan, S. Singh, Shubra Baskar, K.

    2014-04-24

    AlGaN/AlN layers were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The Al{sub x}Ga{sub 1−x}N layer composition was varied from 15% to 25%. The crystalline quality, thickness and aluminum (Al) composition of AlGaN were determined using high resolution X-ray diffraction (HRXRD). The growth rate decreases on increasing Al composition. Reciprocal space mapping (RSM) was used to estimate the strain and relaxation between AlGaN and AlN. The optical properties of AlGaN layers were investigated by room temperature Photoluminescence (PL). The AlGaN peak shifts towards lower wavelength with Al composition. The surface morphology of AlGaN was studied by atomic force microscopy (AFM). Root mean square (RMS) roughness values were found to be increased in AlGaN layers with composition.

  14. Interfaces in InAsSb/InGaAs strained-layer superlattices grown by MOCVD for use in infrared emitters

    SciTech Connect

    Biefeld, R.M.; Follstaedt, D.M.; Kurtz, S.R.; Baucom, K.C.

    1995-02-01

    The authors have prepared InAsSb/InGaAs strained-layer superlattices (SLSs) using metal-organic chemical vapor deposition (MOCVD). X-ray diffraction was used to determine lattice matching as well as composition and structure of the SLS`s. The presence of an InGaAsSb interface layer was indicated by x-ray diffraction for samples grown under non-optimized conditions. Interfacial layers were also identified with transmission electron microscopy (TEM). Two types of interfaces were observed by TEM. The different contrasts observed by TEM could be due to a difference in composition at the interfaces. The width of the x-ray peaks can be explained by a variation of the layer thickness.

  15. Cloud chamber visualization of primary cosmic rays

    SciTech Connect

    Earl, James A.

    2013-02-07

    From 1948 until 1963, cloud chambers were carried to the top of the atmosphere by balloons. From these flights, which were begun by Edward P. Ney at the University of Minnesota, came the following results: discovery of heavy cosmic ray nuclei, development of scintillation and cherenkov detectors, discovery of cosmic ray electrons, and studies of solar proton events. The history of that era is illustrated here by cloud chamber photographs of primary cosmic rays.

  16. Robust Acoustic Transducers for Bubble Chambers

    NASA Astrophysics Data System (ADS)

    Wells, Jonathan

    2015-04-01

    The PICO collaboration utilizes bubble chambers filled with various superheated liquids as targets for dark matter. Acoustic sensors have proved able to distinguish nuclear recoils from radioactive background on an event-by-event basis. We have recently produced a more robust transducer which should be able to operate for years, rather than months, in the challenging environment of a heated high pressure hydraulic fluid outside these chambers. Indiana University South Bend.

  17. RF plasma MOCVD of Y2O3 thin films: Effect of RF self-bias on the substrates during deposition

    NASA Astrophysics Data System (ADS)

    Chopade, S. S.; Barve, S. A.; Thulasi Raman, K. H.; Chand, N.; Deo, M. N.; Biswas, A.; Rai, Sanjay; Lodha, G. S.; Rao, G. M.; Patil, D. S.

    2013-11-01

    Yttrium oxide (Y2O3) thin films have been deposited by radio frequency plasma assisted metal organic chemical vapor deposition (MOCVD) process using (2,2,6,6-tetramethyl-3,5-heptanedionate) yttrium (commonly known as Y(thd)3) precursor in a plasma of argon and oxygen gases at a substrate temperature of 350 °C. The films have been deposited under influence of varying RF self-bias (-50 V to -175 V) on silicon, quartz, stainless steel and tantalum substrates. The deposited coatings are characterized by glancing angle X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and scanning electron microscopy (SEM). GIXRD and FTIR results indicate deposition of Y2O3 (BCC structure) in all cases. However, XPS results indicate nonstoichiometric cubic phase deposition on the surface of deposited films. The degree of nonstoichiometry varies with bias during deposition. Ellipsometry results indicate that the refractive index for the deposited films is varying from 1.70 to 1.83 that is typical for Y2O3. All films are transparent in the investigated wavelength range 300-1200 nm. SEM results indicate that the microstructure of the films is changing with applied bias. Results indicate that it is possible to deposit single phase cubic Y2O3 thin films at low substrate temperature by RF plasma MOCVD process. RF self-bias that decides about the energy of impinging ions on the substrates plays an important role in controlling the texture of deposited Y2O3 films on the substrates. Results indicate that to control the structure of films and its texture, it is important to control the bias on the substrate during deposition. The films deposited at high bias level show degradation in the crystallinity and reduction of thickness.

  18. 12. View north of Tropic Chamber. Natick Research & ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. View north of Tropic Chamber. - Natick Research & Development Laboratories, Climatic Chambers Building, U.S. Army Natick Research, Development & Engineering Center (NRDEC), Natick, Middlesex County, MA

  19. 13. View south of Arctic Chamber. Natick Research & ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. View south of Arctic Chamber. - Natick Research & Development Laboratories, Climatic Chambers Building, U.S. Army Natick Research, Development & Engineering Center (NRDEC), Natick, Middlesex County, MA

  20. Development of sputtered techniques for thrust chambers

    NASA Technical Reports Server (NTRS)

    Mullaly, J. R.; Hecht, R. J.; Schmid, T. E.; Torrey, C. T.

    1975-01-01

    Techniques and materials were developed and evaluated for the fabrication and coating of advanced, long life, regeneratively cooled thrust chambers. Materials were analyzed as fillers for sputter application of OFHC copper as a closeout layer to channeled inner structures; of the materials evaluated, aluminum was found to provide the highest bond strength and to be the most desirable for chamber fabrication. The structures and properties were investigated of thick sputtered OFHC copper, 0.15 Zr-Cu, Al2O3,-Cu, and SiC-Cu. Layered structures of OFHC copper and 0.15 Zr-Cu were investigated as means of improving chamber inner wall fatigue life. The evaluation of sputtered Ti-5Al-2.5Sn, NASA IIb-11, aluminum and Al2O3-Al alloys as high strength chamber outer jackets was performed. Techniques for refurbishing degraded thrust chambers with OFHC copper and coating thrust chambers with protective ZrO2 and graded ZrO2-copper thermal barrier coatings were developed.

  1. Liquid-filled ionization chamber temperature dependence

    NASA Astrophysics Data System (ADS)

    Franco, L.; Gómez, F.; Iglesias, A.; Pardo, J.; Pazos, A.; Pena, J.; Zapata, M.

    2006-05-01

    Temperature and pressure corrections of the read-out signal of ionization chambers have a crucial importance in order to perform high-precision absolute dose measurements. In the present work the temperature and pressure dependences of a sealed liquid isooctane filled ionization chamber (previously developed by the authors) for radiotherapy applications have been studied. We have analyzed the thermal response of the liquid ionization chamber in a ˜20C interval around room temperature. The temperature dependence of the signal can be considered linear, with a slope that depends on the chamber collection electric field. For example, a relative signal slope of 0.27×10-2 K-1 for an operation electric field of 1.67×106 V m-1 has been measured in our detector. On the other hand, ambient pressure dependence has been found negligible, as expected for liquid-filled chambers. The thermal dependence of the liquid ionization chamber signal can be parametrized within the Onsager theory on initial recombination. Considering that changes with temperature of the detector response are due to variations in the free ion yield, a parametrization of this dependence has been obtained. There is a good agreement between the experimental data and the theoretical model from the Onsager framework.

  2. Expandable Purge Chambers Would Protect Cryogenic Fittings

    NASA Technical Reports Server (NTRS)

    Townsend, Ivan I., III

    2004-01-01

    Expandable ice-prevention and cleanliness-preservation (EIP-CP) chambers have been proposed to prevent the accumulation of ice or airborne particles on quick-disconnect (QD) fittings, or on ducts or tubes that contain cryogenic fluids. In the original application for which the EIP-CP chambers were conceived, there is a requirement to be able to disconnect and reconnect the QD fittings in rapid succession. If ice were to form on the fittings by condensation and freezing of airborne water vapor on the cold fitting surfaces, the ice could interfere with proper mating of the fittings, making it necessary to wait an unacceptably long time for the ice to thaw before attempting reconnection. By keeping water vapor away from the cold fitting surfaces, the EIP-CP chambers would prevent accumulation of ice, preserving the ability to reconnect as soon as required. Basically, the role of an EIP-CP chamber would be to serve as an enclosure for a flow of dry nitrogen gas that would keep ambient air away from QD cryogenic fittings. An EIP-CP chamber would be an inflatable device made of a fabriclike material. The chamber would be attached to an umbilical plate holding a cryogenic QD fitting.

  3. High-pressure promoted combustion chamber

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A. (Inventor); Stoltzfus, Joel M. (Inventor)

    1991-01-01

    In the preferred embodiment of the promoted combusiton chamber disclosed herein, a thick-walled tubular body that is capable of withstanding extreme pressures is arranged with removable upper and lower end closures to provide access to the chamber for dependently supporting a test sample of a material being evaluated in the chamber. To facilitate the real-time analysis of a test sample, several pressure-tight viewing ports capable of withstanding the simulated environmental conditions are arranged in the walls of the tubular body for observing the test sample during the course of the test. A replaceable heat-resistant tubular member and replaceable flame-resistant internal liners are arranged to be fitted inside of the chamber for protecting the interior wall surfaces of the combustion chamber during the evaluation tests. Inlet and outlet ports are provided for admitting high-pressure gases into the chamber as needed for performing dynamic analyses of the test sample during the course of an evaluation test.

  4. Chamber study of polychlorinated biphenyl {PCB} emissions ...

    EPA Pesticide Factsheets

    The sorption of airborne polychlorinated biphenyls (PCBs) by twenty building materials and their subsequent re-emission (desorption) from concrete were investigated using two 53-L environmental chambers connected in series with a field-collected caulk in the source chamber serving as a stable source of PCBs and building materials in the test chamber. During the tests, the PCB concentrations in the outlet air of the test chamber were monitored and the building materials were removed from the test chamber at different times to determine their PCB content. Among the materials tested, a petroleum-based paint, a latex paint, and a certain type of carpet were among the strongest sinks. Solvent-free epoxy coating, certain types of flooring materials, and brick were among the weakest sinks. For a given sink material, PCB congeners with lower vapor pressures were sorbed in larger quantities. Rough estimates of the partition and diffusion coefficients were obtained by applying a sink model to the data acquired from the chamber studies. A desorption test with the concrete panels showed that re-emission is a slow process, suggesting that PCB sinks, e.g. concrete, can release PCBs into the air for a prolonged period of time (years or decades). This study could fill some of the data gaps associated with the characterization of PCB sinks in contaminated buildings. This paper summarizes the laboratory research results for PCB transport from primary sources to PCB sinks, includ

  5. Upright Imaging of Drosophila Egg Chambers

    PubMed Central

    Manning, Lathiena; Starz-Gaiano, Michelle

    2015-01-01

    Drosophila melanogaster oogenesis provides an ideal context for studying varied developmental processes since the ovary is relatively simple in architecture, is well-characterized, and is amenable to genetic analysis. Each egg chamber consists of germ-line cells surrounded by a single epithelial layer of somatic follicle cells. Subsets of follicle cells undergo differentiation during specific stages to become several different cell types. Standard techniques primarily allow for a lateral view of egg chambers, and therefore a limited view of follicle cell organization and identity. The upright imaging protocol describes a mounting technique that enables a novel, vertical view of egg chambers with a standard confocal microscope. Samples are first mounted between two layers of glycerin jelly in a lateral (horizontal) position on a glass microscope slide. The jelly with encased egg chambers is then cut into blocks, transferred to a coverslip, and flipped to position egg chambers upright. Mounted egg chambers can be imaged on either an upright or an inverted confocal microscope. This technique enables the study of follicle cell specification, organization, molecular markers, and egg development with new detail and from a new perspective. PMID:25867882

  6. Chamber study of polychlorinated biphenyl (PCB) emissions ...

    EPA Pesticide Factsheets

    The sorption of airborne polychlorinated biphenyls (PCBs) by twenty building materials and their subsequent re-emission (desorption) from concrete were investigated using two 53-L environmental chambers connected in series with a field-collected caulk in the source chamber serving as a stable source of PCBs and building materials in the test chamber. During the tests, the PCB concentrations in the outlet air of the test chamber were monitored and the building materials were removed from the test chamber at different times to determine their PCB content. Among the materials tested, a petroleum-based paint, a latex paint, and a certain type of carpet were among the strongest sinks. Solvent-free epoxy coating, certain types of flooring materials, and brick were among the weakest sinks. For a given sink material, PCB congeners with lower vapor pressures were sorbed in larger quantities. Rough estimates of the partition and diffusion coefficients were obtained by applying a sink model to the data acquired from the chamber studies. A desorption test with the concrete panels showed that re-emission is a slow process, suggesting that PCB sinks, e.g. concrete, can release PCBs into the air for a prolonged period of time (years or decades). This study could fill some of the data gaps associated with the characterization of PCB sinks in contaminated buildings. This paper summarizes the laboratory research results for PCB transport from primary sources to PCB sinks, includ

  7. Chamber for Growing and Observing Fungi

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Molina, Thomas C.

    2005-01-01

    A chamber has been designed to enable growth and observation of microcolonies of fungi in isolation from the external environment. Unlike prior fungus-growing apparatuses, this chamber makes it possible to examine a fungus culture without disrupting it. Partly resembling a small picture frame, the chamber includes a metal plate having a rectangular through-thethickness opening with recesses for a top and a bottom cover glass, an inlet for air, and an inlet for water. The bottom cover glass is put in place and held there by clips, then a block of nutrient medium and a moisture pad are placed in the opening. The block is inoculated, then the top cover glass is put in place and held there by clips. Once growth is evident, the chamber can be sealed with tape. Little (if any) water evaporates past the edges of the cover glasses, and, hence there is little (if any) need to add water. A microscope can be used to observe the culture through either cover glass. Because the culture is sealed in the chamber, it is safe to examine the culture without risking contamination. The chamber can be sterilized and reused.

  8. Laser peripheral iridotomy changes anterior chamber architecture.

    PubMed

    Theinert, Christian; Wiedemann, Peter; Unterlauft, Jan D

    2017-01-19

    The pressure gradient between anterior and posterior chamber in acute angle closure (AAC) and primary angle closure suspects is balanced by a sufficient laser peripheral iridotomy (LPI). The anterior chamber changes induced by LPI in patients with unilateral AAC were examined and compared to healthy eyes to define threshold values, which may help to discriminate between healthy and diseased eyes. Using Scheimpflug photography, anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), and central corneal thickness (CCT) were measured before and after LPI in both eyes of unilateral AAC cases. These measurements were compared to a group of healthy control eyes to determine threshold values for ACD, ACV, and ACA. The ACD, ACV, and ACA increased significantly in the 25 AAC eyes after LPI. The ACD, ACV, ACA, and CCT values in the AAC eyes obtained before LPI were compared to a control group of 59 healthy eyes with wide open chamber angles. The cutoff values revealed by receiver operating characteristic analysis were 2.1 mm for ACD, 90.5 mm2 for ACV, and 27.25° for ACA. Our results confirm the significant changes of the anterior segments architecture induced by LPI in AAC eyes. The found threshold values for ACD, ACV, and ACA may help in daily clinical routine to discriminate between healthy eyes and those in need for a prophylactic LPI.

  9. Cyclic fatigue analysis of rocket thrust chambers. Volume 1: OFHC copper chamber low cycle fatigue

    NASA Technical Reports Server (NTRS)

    Miller, R. W.

    1974-01-01

    A three-dimensional finite element elasto-plastic strain analysis was performed for the throat section of a regeneratively cooled rocket combustion chamber. The analysis employed the RETSCP finite element computer program. The analysis included thermal and pressure loads, and the effects of temperature dependent material properties, to determine the strain range corresponding to the chamber operating cycle. The analysis was performed for chamber configuration and operating conditions corresponding to a hydrogen-oxygen combustion chamber which was fatigue tested to failure. The computed strain range at typical chamber operating conditions was used in conjunction with oxygen-free, high-conductivity (OHFC) copper isothermal fatigue test data to predict chamber low-cycle fatigue life.

  10. A Customizable Chamber for Measuring Cell Migration.

    PubMed

    Chowdhury, Aniqa N; Vo, Huu Tri; Olang, Sharon; Mappus, Elliott; Peterson, Brian; Hlavac, Nora; Harvey, Tyler; Dean, Delphine

    2017-03-12

    Cell migration is a vital part of immune responses, growth, and wound healing. Cell migration is a complex process that involves interactions between cells, the extracellular matrix, and soluble and non-soluble chemical factors (e.g., chemoattractants). Standard methods for measuring the migration of cells, such as the Boyden chamber assay, work by counting cells on either side of a divider. These techniques are easy to use; however, they offer little geometric modification for different applications. In contrast, microfluidic devices can be used to observe cell migration with customizable concentration gradients of soluble factors(1)(,)(2). However, methods for making microfluidics based assays can be difficult to learn. Here, we describe an easy method for creating cell culture chambers to measure cell migration in response to chemical concentration gradients. Our cell migration chamber method can create different linear concentration gradients in order to study cell migration for a variety of applications. This method is relatively easy to use and is typically performed by undergraduate students. The microchannel chamber was created by placing an acrylic insert in the shape of the final microchannel chamber well into a Petri dish. After this, poly(dimethylsiloxane) (PDMS) was poured on top of the insert. The PDMS was allowed to harden and then the insert was removed. This allowed for the creation of wells in any desired shape or size. Cells may be subsequently added to the microchannel chamber, and soluble agents can be added to one of the wells by soaking an agarose block in the desired agent. The agarose block is added to one of the wells, and time-lapse images can be taken of the microchannel chamber in order to quantify cell migration. Variations to this method can be made for a given application, making this method highly customizable.

  11. Tuned Chamber Core Panel Acoustic Test Results

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.

    2016-01-01

    This report documents acoustic testing of tuned chamber core panels, which can be used to supplement the low-frequency performance of conventional acoustic treatment. The tuned chamber core concept incorporates low-frequency noise control directly within the primary structure and is applicable to sandwich constructions with a directional core, including corrugated-, truss-, and fluted-core designs. These types of sandwich structures have long, hollow channels (or chambers) in the core. By adding small holes through one of the facesheets, the hollow chambers can be utilized as an array of low-frequency acoustic resonators. These resonators can then be used to attenuate low-frequency noise (below 400 Hz) inside a vehicle compartment without increasing the weight or size of the structure. The results of this test program demonstrate that the tuned chamber core concept is effective when used in isolation or combined with acoustic foam treatments. Specifically, an array of acoustic resonators integrated within the core of the panels was shown to improve both the low-frequency absorption and transmission loss of the structure in targeted one-third octave bands.

  12. Chamber, Target and Final Focus Integrated Design

    SciTech Connect

    Moir, R.W.

    2000-03-03

    Liquid wall protection, which challenges chamber clearing, has such advantages it's Heavy Ion Fusion's (HIF) main line chamber design. Thin liquid protection from x rays is necessary to avoid erosion of structural surfaces and thick liquid makes structures behind 0.5 m of Flibe (7 mean free paths for 14 MeV neutrons), last the life of the plant. Liquid wall protection holds the promise of greatly increased economic competitiveness. Driver designers require {approx}200 beams to illuminate recent target designs from two sides. The illumination must be compatible with liquid wall protection. The ''best'' values for driver energy, gain, yield and pulse rate comes out of well-known trade-off studies. The chamber design is based on several key assumptions, which are to be proven before HIF can be shown to be feasible. The chamber R&D needed to reduce the unknowns and risks depend on resolving a few technical issues such as jet surface smoothness and rapid chamber clearing.

  13. 78 FR 76750 - Drawbridge Operation Regulation; Chambers Creek, Steilacoom, WA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-19

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Chambers Creek, Steilacoom, WA AGENCY... (BNSF) Chambers Creek Railway Bridge across Chambers Creek, mile 0.0, at Steilacoom, WA. The deviation... Bridge across Chambers Creek, mile 0.0, near Steilacoom, WA. The ] bridge provides 50 feet of vertical...

  14. In-School Student Chamber of Commerce Program.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    An In-School Student Chamber of Commerce Enhancement Program was established in elementary, middle, and senior high school settings in Dade County, Florida. The student Chamber, modeled after the local Chamber, serves as a role model in the following ways: (1) by guiding students to develop a Chamber; (2) by teaching students about the work world;…

  15. Convection and mixing in magma chambers

    NASA Astrophysics Data System (ADS)

    Turner, J. S.; Campbell, I. H.

    1986-08-01

    This paper reviews advances made during the last seven years in the application of fluid dynamics to problems of igneous petrology, with emphasis on the laboratory work with which the authors have been particularly involved. Attention is focused on processes in magma chambers which produce diversity in igneous rocks, such as fractional crystallization, assimilation and magma mixing. Chamber geometry, and variations in the density and viscosity of the magma within it, are shown to play a major role in determining the dynamical behaviour and the composition of the erupted or solidified products. Various convective processes are first reviewed, and in particular the phenomenon of double-diffusive convection. Two types of double-diffusive interfaces between layers of different composition and temperature are likely to occur in magma chambers. A diffusive interface forms when a layer of hot dense magma is overlain by cooler less dense magma. Heat is transported between the layers faster than composition, driving convection in both layers and maintaining a sharp interface between them. If a layer of hot slightly less dense magma overlies a layer of cooler, denser but compositionally lighter magma, a finger interface forms between them, and compositional differences are transported downwards faster than heat (when each is expressed in terms of the corresponding density changes). Processes leading to the establishment of density, compositional and thermal gradients or steps during the filling of a magma chamber are considered next. The stratification produced, and the extent of mixing between the inflowing and resident magmas, are shown to depend on the flow rate and on the relation between the densities and viscosities of the two components. Slow dense inputs of magma may mix very little with resident magma of comparable viscosity as they spread across the floor of the chamber. A similar pulse injected with high upward momentum forms a turbulent "fountain", which is a

  16. Thermal Vacuum Chamber Repressurization with Instrument Purging

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael

    2016-01-01

    At the end of James Webb Space Telescope (JWST) OTIS (Optical Telescope Element-OTE-Integrated Science Instrument Module-ISIM) cryogenic vacuum testing in NASA Johnson Space Centers (JSCs) thermal vacuum (TV) Chamber A, contamination control (CC) engineers are mooting the idea that chamber particulate material stirred up by the repressurization process may be kept from falling into the ISIM interior to some degree by activating instrument purge flows over some initial period before opening the chamber valves. This memo describes development of a series of models designed to describe this process. These are strung together in tandem to estimate overpressure evolution from which net outflow velocity behavior may be obtained. Creeping flow assumptions are then used to determine the maximum particle size that may be kept suspended above the ISIM aperture, keeping smaller particles from settling within the instrument module.

  17. Thermal vacuum chamber repressurization with instrument purging

    NASA Astrophysics Data System (ADS)

    Woronowicz, Michael S.

    2016-09-01

    At the conclusion of cryogenic vacuum testing of the James Webb Space Telescope Optical Telescope Element Integrated Science Instrument Module (JWST-OTIS) in NASA Johnson Space Center's (JSCs) thermal vacuum (TV) Chamber A, contamination control (CC) engineers are postulating that chamber particulate material stirred up by the repressurization process may be kept from falling into the Integrated Science Instrument Module (ISIM) interior to some degree by activating instrument purge flows over some initial period before opening the chamber valves. This manuscript describes development of a series of models designed to describe this process. The models are strung together in tandem with a fictitious set of conditions to estimate overpressure evolution from which net outflow velocity behavior may be obtained. Creeping flow assumptions are then used to determine the maximum particle size that may be kept suspended above the ISIM aperture, keeping smaller particles from settling within the instrument module.

  18. Commissioning of SLAC SLD 45-Degree Chambers

    SciTech Connect

    Eschenburg, Vance O.

    2002-07-19

    The SLD experiment at the Stanford Linear Accelerator Center had a significant gap in its muon tracking coverage, provided by the Warm Iron Calorimeter. Supplemental planes of limited streamer tube chambers were added to improve the coverage in the vicinity of the gap at 0.65 < |cos{theta}| < 0.85. A software effort to upgrade the tracking software for this system is detailed. The commissioning of the forty-five degree chamber region of the SLAC SLD Warm Iron Calorimeter is presented. This task involved the completion of the forty-five degree chamber region geometry for the Warm Iron Calorimeter's fitter and swimmer and the changing of the way multiple scattering effects are treated in the fitter algorithm.

  19. High temperature thrust chamber for spacecraft

    NASA Technical Reports Server (NTRS)

    Chazen, Melvin L. (Inventor); Mueller, Thomas J. (Inventor); Kruse, William D. (Inventor)

    1998-01-01

    A high temperature thrust chamber for spacecraft (20) is provided herein. The high temperature thrust chamber comprises a hollow body member (12) having an outer surface and an internal surface (16) defining the high temperature chamber (10). The body member (12) is made substantially of rhenium. An alloy (18) consisting of iridium and at least alloying metal selected of the group consisting of rhodium, platinum and palladium is deposited on at least a portion of the internal surface (16) of the body member (12). The iridium and the alloying metal are electrodeposited onto the body member (12). A HIP cycle is performed upon the body member (12) to cause the coating of iridium and the alloying metal to form the alloy (18) which protects the body member (12) from oxidation.

  20. Chamber LIDAR measurements of aerosolized biological simulants

    NASA Astrophysics Data System (ADS)

    Brown, David M.; Thrush, Evan P.; Thomas, Michael E.; Siegrist, Karen M.; Baldwin, Kevin; Quizon, Jason; Carter, Christopher C.

    2009-05-01

    A chamber aerosol LIDAR is being developed to perform well-controlled tests of optical scattering characteristics of biological aerosols, including Bacillus atrophaeus (BG) and Bacillus thuringiensis (BT), for validation of optical scattering models. The 1.064 μm, sub-nanosecond pulse LIDAR allows sub-meter measurement resolution of particle depolarization ratio or backscattering cross-section at a 1 kHz repetition rate. Automated data acquisition provides the capability for real-time analysis or recording. Tests administered within the refereed 1 cubic meter chamber can provide high quality near-field backscatter measurements devoid of interference from entrance and exit window reflections. Initial chamber measurements of BG depolarization ratio are presented.

  1. Thermal Vacuum Chamber Repressurization with Instrument Purging

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael

    2017-01-01

    At the end of James Webb Space Telescope (JWST) OTIS (Optical Telescope Element-OTE-Integrated Science Instrument Module-ISIM) cryogenic vacuum testing in NASA Johnson Space Centers (JSCs) thermal vacuum (TV) Chamber A, contamination control (CC) engineers are mooting the idea that chamber particulate material stirred up by the repressurization process may be kept from falling into the ISIM interior to some degree by activating instrument purge flows over some initial period before opening the chamber valves. This memo describes development of a series of models designed to describe this process. These are strung together in tandem to estimate overpressure evolution from which net outflow velocity behavior may be obtained. Creeping flow assumptions are then used to determine the maximum particle size that may be kept suspended above the ISIM aperture, keeping smaller particles from settling within the instrument module.

  2. The ARL/FED anechoic chamber

    NASA Astrophysics Data System (ADS)

    Marboe, R. C.; Fitzgerald, J. M.

    1981-08-01

    This report documents the design and acoustic characteristics of the Applied Research Laboratory Department anechoic chamber. It is located on the above-console deck of the Garfield Thomas Water Tunnel situated so as to allow its use in conjunction with the Axial Flow Research Fan (AFRF). The internal free dimensions of the chamber are 2.74 x 3.05 x 1.98 meters (9 x 10 x 6.5 ft.). The sound absorbing walls are composed of polyurethane foam acoustic wedges, air voids, embossed acoustic foam wall lining, plywood and wood frame members. Air intake ducts, baffled and lined with a lead-foam sheet, provide an adequate air volume for the AFRF. Based on measurements of transmission loss and inverse square law, the chamber is considered anechoic for frequencies above 230 Hz and semi-anechoic for lower frequencies.

  3. Thermal Vacuum Chamber Repressurization with Instrument Purging

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael S.

    2014-01-01

    At the conclusion of cryogenic vacuum testing of the James Webb Space Telescope Optical Telescope Element Integrated Science Instrument Module (JWST-OTIS) in NASA Johnson Space Center’s (JSCs) thermal vacuum (TV) Chamber A, contamination control (CC) engineers are postulating that chamber particulate material stirred up by the repressurization process may be kept from falling into the Integrated Science Instrument Module (ISIM) interior to some degree by activating instrument purge flows over some initial period before opening the chamber valves. This manuscript describes development of a series of models designed to describe this process. The models are strung together in tandem with a fictitious set of conditions to estimate overpressure evolution from which net outflow velocity behavior may be obtained. Creeping flow assumptions are then used to determine the maximum particle size that may be kept suspended above the ISIM aperture, keeping smaller particles from settling within the instrument module.

  4. Anterior chamber collapse syndrome in a koala.

    PubMed

    Liddle, Vl; Naranjo, C; Bernays, Me

    2014-05-01

    Anterior chamber collapse syndrome has been recognised in various species and is associated with early-life ocular disease or trauma. It is important to differentiate this acquired condition from a congenital malformation. An adult female koala (Phascolarctos cinereus) was referred for assessment of buphthalmos and severe keratitis of the right eye. The degree of keratitis obstructed examination of intraocular structures. Enucleation of the affected eye was performed and the histopathological diagnosis was anterior chamber collapse syndrome and secondary glaucoma. This case contributes to the limited information available in the literature on anterior chamber collapse syndrome, a disease unique in having secondary glaucoma with minimal or no inflammation. The case also expands the literature available on ocular disease in koalas. More specifically, this is the only reported case of glaucoma, of any aetiology, in the koala. © 2014 Australian Veterinary Association.

  5. Central Drift Chamber for Belle-II

    NASA Astrophysics Data System (ADS)

    Taniguchi, N.

    2017-06-01

    The Central Drift Chamber (CDC) is the main device for tracking and identification of charged particles for Belle-II experiment. The Belle-II CDC is cylindrical wire chamber with 14336 sense wires, 2.3 m-length and 2.2 m-diameter. The wire chamber and readout electronics have been completely replaced from the Belle CDC. The new readout electronics system must handle higher trigger rate of 30 kHz with less dead time at the design luminosity of 8 × 1035 cm-2s-1. The front-end electronics are located close to detector and send digitized signal through optical fibers. The Amp-Shaper-Discriminator chips, FADC and FPGA are assembled on a single board. Belle-II CDC with readout electronics has been installed successfully in Belle structure in October 2016. We will present overview of the Belle-II CDC and status of commissioning with cosmic ray.

  6. Silicone oil in the anterior chamber.

    PubMed

    Gao, R L; Neubauer, L; Tang, S; Kampik, A

    1989-01-01

    A total of 42 cases (42 eyes) with silicone oil in the anterior chamber after pars plana vitrectomy (PPV) and after silicone oil injection into the vitreous cavity (SIV) were analyzed. The main complications caused by silicone oil were corneal endothelial cell damage and secondary glaucoma. Specular microscopy showed decreased cell density, apparent pleomorphism of endothelial cells, and increased corneal thickness. In some cases, edematous and necrotic endothelial cells were found. The characteristic optical artifacts resulting from silicone oil coming into contact with the endothelium, such as a bright reflex, reversed pattern of illumination, and interference fringes, were also observed. There was a definite correlation between elevated intraocular pressure (IOP) and the presence of silicone oil in the anterior chamber; the IOP dropped significantly on removal of the oil. The treatment and prevention of conditions involving silicone oil in the anterior chamber are briefly discussed.

  7. Lightweight Chambers for Thrust Cell Applications

    NASA Technical Reports Server (NTRS)

    Elam, S.; Effinger, M.; Holmes, R.; Lee, J.; Jaskowiak, M.

    2000-01-01

    Traditional metals like steel and copper alloys have been used for many years to fabricate injector and chamber components of thruster assemblies. While the materials perform well, reducing engine weights would help existing and future vehicles gain performance and payload capability. It may now be possible to reduce current thruster weights up to 50% by applying composite materials. In this task, these materials are being applied to an existing thrust cell design to demonstrate new fabrication processes and potential weight savings. Two ceramic matrix composite (CMC) designs, three polymer matrix composite (PMC) designs, and two metal matrix composite (MMC) designs are being fabricated as small chamber demonstration units. In addition, a new alloy of copper, chrome, and niobium (Cu-8Cr-4Nb) is being investigated for thrust chamber liners since it offers higher strength and increased cycle life over traditional alloys. This new alloy is being used for the liner in each MMC and PMC demonstration unit. During June-August of 2000, hot-fire testing of each unit is planned to validate designs in an oxygen/hydrogen environment at chamber pressures around 850 psi. Although the weight savings using CMC materials is expected to be high, they have proven to be much harder to incorporate into chamber designs based on current fabrication efforts. However, the PMC & MMC concepts using the Cu-8Cr-4Nb liner are nearly complete and ready for testing. Additional efforts intend to use the PMC & MMC materials to fabricate a full size thrust chamber (60K lb(sub f) thrust class). The fabrication of this full size unit is expected to be complete by October 2000, followed by hot-fire testing in November-December 2000.

  8. Microstructures of GaN and In{sub x}Ga{sub 1-x}N films grown by MOCVD on free-standing GaN templates

    SciTech Connect

    Jasinski, J.; Liliental-Weber, Z.; Huang, D.; Reshchikov, M.A.; Yun, F.; Morkoc, H.; Sone, C.; Park, S.S.; Lee, K.Y.

    2002-04-30

    We summarize structural properties of thick HVPE GaN templates from the point of view of their application as substrates for growth of nitride layers. This is followed by the results of optical and structural studies, mostly transmission electron microscopy, of nitride layers grown by MOCVD on top of the HVPE substrates. The results indicate high structural quality of these layers with a low density of threading dislocations (in the range of 10{sup 6} cm{sup -2}). Convergent beam electron diffraction studies showed that the MOCVD GaN films have Ga-polarity, the same polarity as the HVPE GaN substrates. Structural studies of an InGaN layer grown on top of the MOCVD GaN film showed the presence of two layers, which differed in lattice parameter and composition. The upper layer, on the top of the structure had a c-lattice parameter about 2% larger than that of GaN and contained 10.3 {+-} 0.8% of In. Values measured for the thinner, intermediate layer adjacent to the GaN layer were about 2 .5 times lower.

  9. Space shuttle orbit maneuvering engine reusable thrust chamber program

    NASA Technical Reports Server (NTRS)

    Pauckert, R. P.; Yost, M. C.; Tobin, R. D.

    1973-01-01

    Tests were conducted on the regenerative cooled thrust chamber of the space shuttle orbit maneuvering engine. The conditions for the tests and the durations obtained are presented. The tests demonstrated thrust chamber operation over the nominal ranges of chamber pressure mixture ratio. Variations in auxiliary film coolant flowrate were also demonstrated. High pressure tests were conducted to demonstrate the thrust chamber operation at conditions approaching the design chamber pressure for the derivative space tug application.

  10. Sealed Plant-Growth Chamber For Clinostat

    NASA Technical Reports Server (NTRS)

    Brown, Christopher S.; Dreschel, Thomas W.

    1993-01-01

    Laboratory chamber for growing plants used to measure photosynthesis and respiration in simulated microgravity. Holds plant specimens while rotated on clinostat, see article, "Clinostat Delivers Power To Plant-Growth Cabinets" (KSC-11537). Provides way of comparing gas-exchange rates of plants rotated horizontally on clinostat with those of stationary or vertically rotated plants. Gas extracted for analysis without stopping clinostat. Chamber includes potlike base and cylindrical cover, both made of transparent acrylic pipe. Gasket forms seal between cover and bottom plate of base. Cover bolted to pot baseplate, which in turn bolted to clinostat.

  11. The chamber-scarification test for irritancy.

    PubMed

    Frosch, P J; Kligman, A M

    1976-12-01

    A procedure has been designed (the chamber-scarification test), which possesses greatly increased sensitivity for assessing the irritancy of topically applied materials. A forearm test site is criss-cross scarified by drawing a 30-gauge needle over the skin with just enough pressure to cleave the epidermis without drawing blood. The test agent is applied in an aluminum chamber once daily for 3 days. The advantages of the method over conventional patch testing are: enhanced capacity to measure mild irritants, reduced time (3 days versus 10 to 21 days), less effort, less cost, less discomfort for the volunteers and greater reproducibility.

  12. Almond test body. [for microwave anechoic chambers

    NASA Technical Reports Server (NTRS)

    Dominek, Allen K. (Inventor); Wood, Richard M. (Inventor); Gilreath, Melvin C. (Inventor)

    1989-01-01

    The invention is an almond shaped test body for use in measuring the performance characteristics of microwave anechoic chambers and for use as a support for components undergoing radar cross-section measurements. The novel aspect of this invention is its shape, which produces a large dynamic scattered field over large angular regions making the almond valuable for verifying the performance of microwave anechoic chambers. As a component mount, the almond exhibits a low return that does not perturb the measurement of the component and it simulates the backscatter characteristics of the component as if over an infinite ground plane.

  13. Sealed Plant-Growth Chamber For Clinostat

    NASA Technical Reports Server (NTRS)

    Brown, Christopher S.; Dreschel, Thomas W.

    1993-01-01

    Laboratory chamber for growing plants used to measure photosynthesis and respiration in simulated microgravity. Holds plant specimens while rotated on clinostat, see article, "Clinostat Delivers Power To Plant-Growth Cabinets" (KSC-11537). Provides way of comparing gas-exchange rates of plants rotated horizontally on clinostat with those of stationary or vertically rotated plants. Gas extracted for analysis without stopping clinostat. Chamber includes potlike base and cylindrical cover, both made of transparent acrylic pipe. Gasket forms seal between cover and bottom plate of base. Cover bolted to pot baseplate, which in turn bolted to clinostat.

  14. Crew Training - Apollo 9 (Alt. Chamber) - KSC

    NASA Image and Video Library

    1968-01-01

    S68-55255 (6 Nov. 1968) --- Overhead view of Altitude Chamber "L" in the Kennedy Space Center's Manned Spacecraft Operations Building showing a member of the Apollo 9 backup crew preparing to ingress the Apollo 9 spacecraft for egress test and simulated altitude run. The Apollo 9 backup crew consists of astronauts Charles Conrad Jr., Richard F. Gordon Jr., and Alan L. Bean.

  15. Multiphysics Nuclear Thermal Rocket Thrust Chamber Analysis

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See

    2005-01-01

    The objective of this effort is t o develop an efficient and accurate thermo-fluid computational methodology to predict environments for hypothetical thrust chamber design and analysis. The current task scope is to perform multidimensional, multiphysics analysis of thrust performance and heat transfer analysis for a hypothetical solid-core, nuclear thermal engine including thrust chamber and nozzle. The multiphysics aspects of the model include: real fluid dynamics, chemical reactivity, turbulent flow, and conjugate heat transfer. The model will be designed to identify thermal, fluid, and hydrogen environments in all flow paths and materials. This model would then be used to perform non- nuclear reproduction of the flow element failures demonstrated in the Rover/NERVA testing, investigate performance of specific configurations and assess potential issues and enhancements. A two-pronged approach will be employed in this effort: a detailed analysis of a multi-channel, flow-element, and global modeling of the entire thrust chamber assembly with a porosity modeling technique. It is expected that the detailed analysis of a single flow element would provide detailed fluid, thermal, and hydrogen environments for stress analysis, while the global thrust chamber assembly analysis would promote understanding of the effects of hydrogen dissociation and heat transfer on thrust performance. These modeling activities will be validated as much as possible by testing performed by other related efforts.

  16. A reusable prepositioned ATP reaction chamber

    NASA Technical Reports Server (NTRS)

    Hoffman, D. G.

    1972-01-01

    Luminescence biometer detects presence of life by means of light-emitting chemical reaction of luciferin and luciferase with adenosine triphosphate (ATP) that occurs in all living cells. Amount of light in reaction chamber is measured to determine presence and extent of life.

  17. Acoustical-Levitation Chamber for Metallurgy

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Trinh, E.; Wang, T. G.; Elleman, D. D.; Jacobi, N.

    1983-01-01

    Sample moved to different positions for heating and quenching. Acoustical levitation chamber selectively excited in fundamental and second-harmonic longitudinal modes to hold sample at one of three stable postions: A, B, or C. Levitated object quickly moved from one of these positions to another by changing modes. Object rapidly quenched at A or C after heating in furnace region at B.

  18. Is Climate Simulation in Growth Chambers Necessary?

    Treesearch

    Z.M. Wang; K.H. Johnsen; M.J. Lechowicz

    1999-01-01

    In the expression of their genetic potential as phenotypes, trees respond to environmental cues such as photoperiod, temperature and soil and atmospheric water. However, growth chamber experiments often utilize simple and standard environmental conditions that might not provide these important environmental signals. We conducted a study to compare seedling growth in...

  19. Chamber transport for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Olson, Craig L.

    2014-01-01

    A brief review is given of research on chamber transport for HIF (heavy ion fusion) dating from the first HIF Workshop in 1976 to the present. Chamber transport modes are categorized into ballistic transport modes and channel-like modes. Four major HIF reactor studies are summarized (HIBALL-II, HYLIFE-II, Prometheus-H, OSIRIS), with emphasis on the chamber transport environment. In general, many beams are used to provide the required symmetry and to permit focusing to the required small spots. Target parameters are then discussed, with a summary of the individual heavy ion beam parameters required for HIF. The beam parameters are then classified as to their line charge density and perveance, with special emphasis on the perveance limits for radial space charge spreading, for the space charge limiting current, and for the magnetic (Alfven) limiting current. The major experiments on ballistic transport (SFFE, Sabre beamlets, GAMBLE II, NTX, NDCX) are summarized, with specific reference to the axial electron trapping limit for charge neutralization. The major experiments on channel-like transport (GAMBLE II channel, GAMBLE II self-pinch, LBNL channels, GSI channels) are discussed. The status of current research on HIF chamber transport is summarized, and the value of future NDCX-II transport experiments for the future of HIF is noted.

  20. Wave Phenomena in an Acoustic Resonant Chamber

    ERIC Educational Resources Information Center

    Smith, Mary E.; And Others

    1974-01-01

    Discusses the design and operation of a high Q acoustical resonant chamber which can be used to demonstrate wave phenomena such as three-dimensional normal modes, Q values, densities of states, changes in the speed of sound, Fourier decomposition, damped harmonic oscillations, sound-absorbing properties, and perturbation and scattering problems.…

  1. Heat-barrier coatings for combustion chambers

    NASA Technical Reports Server (NTRS)

    Carpenter, H. W.

    1970-01-01

    Arc-plasma-sprayed layered coating of graded Inconel and zirconia protects film-coolant ring below injector plate of rocket engine combustion chamber. Interfacial temperature is designed for minimum buildup of stress and to avoid melting of the metal phase in the graded layers.

  2. Detecting dark matter with scintillating bubble chambers

    NASA Astrophysics Data System (ADS)

    Zhang, Jianjie; Dahl, C. Eric; Jin, Miaotianzi; Baxter, Daniel

    2016-03-01

    Threshold based direct WIMP dark matter detectors such as the superheated bubble chambers developed by the PICO experiment have demonstrated excellent electron-recoil and alpha discrimination, excellent scalability, ease of change of target fluid, and low cost. However, the nuclear-recoil like backgrounds have been a limiting factor in their dark matter sensitivity. We present a new type of detector, the scintillating bubble chamber, which reads out the scintillation pulse of the scattering events as well as the pressure, temperature, acoustic traces, and bubble images as a conventional bubble chamber does. The event energy provides additional handle to discriminate against the nuclear-recoil like backgrounds. Liquid xenon is chosen as the target fluid in our prototyping detector for its high scintillation yield and suitable vapor pressure which simplifies detector complexity. The detector can be used as an R&D tool to study the backgrounds present in the current PICO bubble chambers or as a prototype for standalone dark matter detectors in the future. Supported by DOE Grant DE-SC0012161.

  3. Isolation of Drosophila egg chambers for imaging.

    PubMed

    Parton, Richard M; Vallés, Ana Maria; Dobbie, Ian M; Davis, Ilan

    2010-04-01

    The fruit fly Drosophila melanogaster is an important model for basic research into the molecular mechanisms underlying cell function and development, as well as a major biomedical research tool. A significant advantage of Drosophila is the ability to apply live cell imaging to a variety of living tissues that can be dissected and imaged in vivo, ex vivo, or in vitro. Drosophila egg chambers, for example, have proven to be a useful model system for studying border cell migration, Golgi unit transport, the rapid movement of mRNA and protein particles, and the role of microtubules in meiosis and oocyte differentiation. A crucial first step before imaging is preparation of the experimental material to ensure physiological relevance and to achieve the best conditions for image quality. Early- to mid-stage egg chambers cannot be mounted in an aqueous-based medium, because this causes a change in microtubule organization and follicle cell morphology. Such egg chambers survive better in Halocarbon oil, which allows free diffusion of oxygen, has low viscosity, and thus prevents dehydration and hypoxia. With a refractive index similar to glycerol, Halocarbon oil also has good optical properties for imaging. It also provides a good environment for injection and is particularly useful for long-term imaging of embryos. However, unlike with aqueous solutions, changes in the medium are not possible. This protocol describes the isolation of Drosophila egg chambers.

  4. Chamber of Commerce reception for Dr. Lucas

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Dr. William R. Lucas, Marshall's fourth Center Director (1974-1986), delivers a speech in front of a picture of the lunar landscape with Earth looming in the background while attending a Huntsville Chamber of Commerce reception honoring his achievements as Director of Marshall Space Flight Center (MSFC).

  5. Wave Phenomena in an Acoustic Resonant Chamber

    ERIC Educational Resources Information Center

    Smith, Mary E.; And Others

    1974-01-01

    Discusses the design and operation of a high Q acoustical resonant chamber which can be used to demonstrate wave phenomena such as three-dimensional normal modes, Q values, densities of states, changes in the speed of sound, Fourier decomposition, damped harmonic oscillations, sound-absorbing properties, and perturbation and scattering problems.…

  6. Anterior Chamber Live Loa loa: Case Report

    PubMed Central

    Kagmeni, G.; Cheuteu, R.; Bilong, Y.; Wiedemann, P.

    2016-01-01

    We reported a case of unusual intraocular Loa loa in a 27-year-old patient who presented with painful red eye. Biomicroscopy revealed a living and active adult worm in the anterior chamber of the right eye. After surgical extraction under local anesthesia, parasitological identification confirmed L. loa filariasis. PMID:27441005

  7. Anterior Chamber Live Loa loa: Case Report.

    PubMed

    Kagmeni, G; Cheuteu, R; Bilong, Y; Wiedemann, P

    2016-01-01

    We reported a case of unusual intraocular Loa loa in a 27-year-old patient who presented with painful red eye. Biomicroscopy revealed a living and active adult worm in the anterior chamber of the right eye. After surgical extraction under local anesthesia, parasitological identification confirmed L. loa filariasis.

  8. Lifetime tests for MAC vertex chamber

    SciTech Connect

    Nelson, H.N.

    1986-07-01

    A vertex chamber for MAC was proposed to increase precision in the measurement of the B hadron and tau lepton lifetimes. Thin-walled aluminized mylar drift tubes were used for detector elements. A study of radiation hardness was conducted under the conditions of the proposed design using different gases and different operating conditions. (LEW)

  9. Simple chamber facilitates chemiluminescent detection of bacteria

    NASA Technical Reports Server (NTRS)

    Marts, E. C.; Wilkins, J. R.

    1970-01-01

    Test chamber enables rapid estimation of bacteria in a test sample through the reaction of luminol and an oxidant with the cytochrome C portion of certain species of bacteria. Intensity of the light emitted in the reaction is a function of the specific bacteria in the test sample.

  10. GRCop-84 Development for Combustion Chamber Liners

    NASA Technical Reports Server (NTRS)

    Ellis, David; Nathal, Michael; Yun, Hee Man; Lerch, Bradley; Greenbauer-Seng, Leslie; Thomas-Ogbuji, Linus; Holmes, Richard

    2000-01-01

    The development, test, and thermophysical & mechanical properties of a GRCop-84 alloy for combustion chamber liners is discussed. Topics discussed include: History of GRCop-84 development, GRCop-84 thermal expansion, thermal conductivity of GRCop-84, yield strength of GRCop-84, GRCop-84 creep lives, GrCop-84 low cycle fatigue (LCF) lives, and hot fire testing of GRCop-84 spool pieces.

  11. Monitoring the Atmosphere in an Anaerobic Chamber

    PubMed Central

    Sudo, Sara Z.; Hersch, Paul A.

    1974-01-01

    The Couloximeter, a fuel cell designed to measure trace amounts of oxygen, was used to monitor the atmosphere in an anaerobic chamber. The device, easy to operate and to maintain, allowed both major and minor fluctuations in oxygen concentration to be measured. Using a hose attached to the outlet within the box, defective (ruptured) gloves were consistently distinguishable from intact gloves. PMID:16350004

  12. Sandra Magnus Training in ETA Chamber

    NASA Image and Video Library

    2002-06-05

    JSC2002-E-23122 (5 June 2002) --- Astronaut Sandra H. Magnus, STS-112 mission specialist, dons a training version of the Extravehicular Mobility Unit (EMU) space suit prior to a mission training session in the Environmental Test Article (ETA) Chamber in the Crew Systems Laboratory at Johnson Space Center (JSC).

  13. Evaluation of Microwave Anechoic Chamber Absorbing Materials

    DTIC Science & Technology

    1988-05-01

    Labs: Mcgraw-Hill, vol. 11, pp. 612-616, 1947. [14] B. F. Lawrence, "RF anechoic chamber test facilities," Second ESTEC spacecraft EMC seminar... Noordwijk , Netherlands, 1982. [15] E. B. McMillan, and H. J. Schmitt, "Doppler method for absorber testing," Microwave Journal. vol. 3, pp. 64- 68, nov

  14. Try Chamber Music--Here's How.

    ERIC Educational Resources Information Center

    Rudaitis, Cheryl

    1995-01-01

    Profiles four middle school teachers maintaining early chamber music programs. The teachers advise varying degrees of musical competency before students begin the program, but all of them caution against starting too soon. They also stress the importance of purchasing early music scores and establishing rehearsal times. (MJP)

  15. Miniature reaction chamber and devices incorporating same

    DOEpatents

    Mathies, Richard A.; Woolley, Adam T.

    2000-10-17

    The present invention generally relates to miniaturized devices for carrying out and controlling chemical reactions and analyses. In particular, the present invention provides devices which have miniature temperature controlled reaction chambers for carrying out a variety of synthetic and diagnostic applications, such as PCR amplification, nucleic acid hybridization, chemical labeling, nucleic acid fragmentation and the like.

  16. Chamber of Commerce reception for Dr. Lucas

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Dr. William R. Lucas, Marshall's fourth Center Director (1974-1986), delivers a speech in front of a picture of the lunar landscape with Earth looming in the background while attending a Huntsville Chamber of Commerce reception honoring his achievements as Director of Marshall Space Flight Center (MSFC).

  17. Chamber for Aerosol Deposition of Bioparticles

    NASA Technical Reports Server (NTRS)

    Kern, Roger; Kirschner, Larry

    2008-01-01

    Laboratory apparatus is depicted that is a chamber for aerosol deposition of bioparticles on surfaces of test coupons. It is designed for primary use in inoculating both flat and three-dimensional objects with approximately reproducible, uniform dispersions of bacterial spores of the genus Bacillus so that the objects could be used as standards for removal of the spores by quantitative surface sampling and/or cleaning processes. The apparatus is also designed for deposition of particles other than bacterial spores, including fungal spores, viruses, bacteriophages, and standard micron-sized beads. The novelty of the apparatus lies in the combination of a controllable nebulization system with a settling chamber large enough to contain a significant number of test coupons. Several companies market other nebulizer systems, but none are known to include chambers for deposition of bioparticles to mimic the natural fallout of bioparticles. The nebulization system is an expanded and improved version of commercially available aerosol generators that include nebulizers and drying columns. In comparison with a typical commercial aerosol generator, this system includes additional, higher-resolution flowmeters and an additional pressure regulator. Also, unlike a typical commercial aerosol generator, it includes stopcocks for separately controlling flows of gases to the nebulizer and drying column. To maximize the degree of uniformity of dispersion of bioaerosol, the chamber is shaped as an axisymmetrical cylinder and the aerosol generator is positioned centrally within the chamber and aimed upward like a fountain. In order to minimize electric charge associated with the aerosol particles, the drying column is made of aluminum, the drying column is in direct contact with an aluminum base plate, and three equally spaced Po-210 antistatic strips are located at the exit end of the drying column. The sides and top of the chamber are made of an acrylic polymer; to prevent

  18. Measurement of surface alpha contamination using electret ion chambers.

    PubMed

    Dua, S K; Biswas, S K; Szerszen, P; Boudreaux, J; Ebadian, M A

    1999-06-01

    Electret ion chambers are inexpensive, light-weight, commercially available, passive charge-integrating devices for accurate measurement of different radiations. Performance of electret ion chambers for surface alpha contamination measurement was evaluated. Ion chambers of two types and electrets of three thicknesses were used for the study. Calibration of the electret ion chambers was performed using reference alpha standards of different energies and radioactivities. Effects of various parameters such as chamber dimensions, electret thickness, alpha particle energy, position of alpha source from the chamber centerline, source localized or uniformly distributed, level of alpha contamination, Mylar window covering the chamber, and ambient radon and gamma radiation on the response of the electret ion chambers were determined. Suitable combinations of chambers and electrets to measure surface alpha contamination were determined.

  19. Test plan pressure fed thrust chamber technology

    NASA Technical Reports Server (NTRS)

    Dunn, Glenn

    1990-01-01

    Aerojet is developing the technology for the design of a reliable, low cost, efficient, and lightweight LOX/RP-1 pressure fed engine. This technology program is a direct result of Aerojet's liquid rocket booster (LRB) study and previous NASA studies that identified liquid engines using high bulk density hydrocarbon fuels as very attractive for a space transportation system (STS). Previous large thrust LOX/RP-1 engine development programs were characterized by costly development problems due to combustion instability damage. The combustion stability solution was typically obtained through trial and error methods of minimizing instability damage by degrading engine performance. The approach to this program was to utilize existing and newly developed combustion analysis models and design methodology to create a thrust chamber design with features having the potential of producing reliable and efficient operation. This process resulted in an engine design with a unique high thrust-per-element OFO triplet injector utilizing a low cost modular approach. Cost efficient ablative materials are baselined for the injector face and chamber. Technology demonstration will be accomplished through a hot fire test program using appropriately sized subscale hardware. This subscale testing will provide a data base to supplement the current industry data bank and to anchor and validate the applied analysis models and design methodology. Once anchored and validated, these analysis models and design methodology can be applied with greatly increased confidence to design and characterize a large scale pressure fed LOX/RP-1 thrust chamber. The objective of this test program is to generate a data base that can be used to anchor and validate existing analysis models and design methodologies and to provide early concept demonstration of a low cost, efficient LOX/RP-1 thrust chamber. Test conditions and hardware instrumentation were defined to provide data sufficient to characterize combustion

  20. Chamber construction for internal combustion engine

    SciTech Connect

    Leydorf, G.F. Jr.; Pulick, M.A.

    1987-10-13

    A method is described of assembling an internal combustion engine, comprising: (a) defining a three piece construction to define the combustion chambers, camshaft case, water jacket, and crankshaft case of the internal combustion engine. The three pieces consist of a cast metal monoblock defining combustion chambers aligned along a central plane. The monoblock contains wear resistant surfaces comprising cylinder bores, valve seats and valve guides, a pair of cast metal complementary clamshell housing sections having margins mateable along the central plane and effective to support and envelope the monoblock in spaced relationship therein to define a water jacket chamber about the combustion chambers. The sections each contain peripheral grooves in the margins about the water jacket perimeter for reception of means to seal the chamber and to join the sections together in a fixed relationship; (b) laying one of the clamshell housing sections in a horizontal position so that the margins of the mating plane is in a horizontal position; (c) inserting functional subassemblies into and onto the monoblock. The subassemblies comprise the camshaft, cam followers, springs and valve trains to constitute a valve train, piston, sealing members, and connecting rod assembly, and a crankshaft assembly; (d) laying the monoblock containing the subassemblies into the horizontally prone clamshell section in a manner so that the facing surfaces on the monoblock oppose the grooves in the margins; (e) interposing sealing means into the groove of the one section; and (f) placing the other clamshell section over and onto the first clamshell section to close the construction in such a manner that the groove and lip surface between the monoblock and second clamshell section are opposing each other; the closed sections then being fixedly joined to complete the engine construction.

  1. Four chamber pacing in dilated cardiomyopathy.

    PubMed

    Cazeau, S; Ritter, P; Bakdach, S; Lazarus, A; Limousin, M; Henao, L; Mundler, O; Daubert, J C; Mugica, J

    1994-11-01

    A 54-year-old man received a four chamber pacing system for severe congestive heart failure (NYHA functional Class IV). His ECG showed a left bundle branch block (200-msec QRS duration) with 200-msec PR interval, normal QRS axis, and 90-msec interatrial interval. An acute hemodynamic study with insertion of four temporary leads was performed prior to the implant, which demonstrated a significant increase in cardiac output and decrease of pulmonary capillary wedge pressure. A permanent pacemaker was implanted based on the encouraging results of the acute study. The right chamber leads were introduced by cephalic and subclavian approaches. The left atrium was paced with a coronary sinus lead, Medtronic SP 2188-58 model. An epicardial Medtronic 5071 lead was placed on the LV free wall. The four leads were connected to a standard bipolar DDD pacemaker, Chorus 6234. The two atrial leads were connected via a Y-connector to the atrial channel of the pacemaker with a bipolar pacing configuration. The two ventricular leads were connected in a similar fashion to the ventricular channel of the device. The right chamber leads were connected to the distal poles. The left chamber leads were connected to the proximal poles of the pacemaker. Six weeks later, the patient's clinical status improved markedly with a weight loss of 17 kg and disappearance of peripheral edema. His functional class was reduced to NYHA II. Four chamber pacing is technically feasible. In patients with evidence of interventricular dyssynchrony, this original pacing mode probably provides a mechanical activation sequence closer to the natural one.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. A new plant chamber facility PLUS coupled to the atmospheric simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

    2015-11-01

    A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been build and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees are mixed with synthetic air and are transferred to the SAPHIR chamber where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOC) can be studied in detail. In PLUS all important enviromental parameters (e.g. temperature, PAR, soil RH etc.) are well-controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leafes of the plants is constructed such that gases are exposed to FEP Teflon film and other Teflon surfaces only to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 LED panels which have an emission strength up to 800 μmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOC) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light and temperature dependent BVOC emissions are studied using six Quercus Ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus Ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental set up and the utility of the newly added plant chamber.

  3. A new plant chamber facility, PLUS, coupled to the atmosphere simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

    2016-03-01

    A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been built and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow-through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees is mixed with synthetic air and transferred to the SAPHIR chamber, where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOCs) can be studied in detail. In PLUS all important environmental parameters (e.g., temperature, photosynthetically active radiation (PAR), soil relative humidity (RH)) are well controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leaves of the plants is constructed such that gases are exposed to only fluorinated ethylene propylene (FEP) Teflon film and other Teflon surfaces to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 light-emitting diode (LED) panels, which have an emission strength up to 800 µmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOCs) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light- and temperature- dependent BVOC emissions are studied using six Quercus ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental setup and the utility of the newly added plant chamber.

  4. Convective Regimes in Crystallizing Basaltic Magma Chambers

    NASA Astrophysics Data System (ADS)

    Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.

    2015-12-01

    Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may convect, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible convective modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. Convection in this system is driven thermally, simulating magma convection above and within a porous cumulate pile. We observe a range of possible convective regimes, enabling us to produce a regime diagram. In addition to modes characterised by convection of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by convection in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional convection within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a

  5. Alleviation of parasitic reactions for III-nitride epitaxy in MOCVD with a spatial separated source delivery method by controlling the main reaction type

    NASA Astrophysics Data System (ADS)

    Yang, Haojun; Wu, Haiyan; Hu, Wei; Ma, Ziguang; Jiang, Yang; Wang, Wenxin; Jia, Haiqiang; Zhou, Junming; Chen, Hong

    2017-05-01

    A spatial separated source delivery (SSSD) method has been proposed to alleviate parasitic reactions between group III precursors and ammonia (NH3) in gas phase using the MOCVD. AlGaN alloys and GaN films grown on sapphire has been prepared with this method. The influence of parasitic reactions on the qualities and properties of AlGaN and GaN films is investigated in detail. High-resolution X-ray diffraction (HRXRD) measurements show that the aluminum composition in materials rises up close to the ratio of trimethylaluminum (TMAl) supply when the supply ratio of TMAl is 0.2, 0.3 and 0.4 respectively, which demonstrates that the parasitic reactions are suppressed mostly. In-situ monitor reflectometer spectra for GaN show that the growth rate gets a 20% increase in comparison with materials grown without the SSSD method. Subsequently, the relationship between parasitic reactions and other reaction types are elucidated. The effect of the SSSD method on parasitic reactions is also systematically studied. Reactions are controlled to change from combination reactions to pyrolysis reactions and surface reactions with the SSSD method. A 2-inch GaN/AlGaN heterostructure is also prepared to evaluate the uniform electrical properties grown with this method. The result indicates that the SSSD method provides a better way to prepare high-quality III-nitride materials, especially for AlN and related alloys.

  6. Hetero-epitaxy of Lg = 0.13-μm metamorphic AlInAs/GaInAs HEMT on Si substrates by MOCVD for logic applications

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Li, Ming; Zhao, Qian; Gu, Wen-Wen; Lau, Kei-May

    2015-08-01

    In this work, a hetero-epitaxial Al0.49In0.51As/Ga0.47In0.53As metamorphic high electron mobility transistor (mHEMT) grown by metal-organic chemical vapor deposition (MOCVD) on p-type silicon substrate has been successfully demonstrated. A novel AlGaAs/AlAs period multiple quantum well (MQW) composite buffer scheme is developed to effectively tune the leakage current from the buffer layer. The quantized room-temperature Hall mobility of the two-dimensional electron gas (2DEG) is larger than 7800 cm2/V·s, with an average sheet carrier density of 4.6×1012 cm - 2. Two-stage electron beam (EB) lithography technology by a JBX-6300 e-beam lithography system is developed to realize a 0.13-μm mHEMT device on Si substrate. A maximum transconductance Gm of up to 854 mS/mm is achieved, and is comparable to that of mHEMT technology on GaAs substrate with the same dimension. The fT and fmax are 135 GHz and 120 GHz, respectively. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61401373), the Fundamental Research Funds for Central University, China (Grant Nos. XDJK2013B004 and 2362014XK13), and the Chongqing Natural Science Foundation, China (Grant No. cstc2014jcyjA40038).

  7. Electron microscopy study of MOCVD-grown TiO sub 2 thin films and TiO sub 2 /Al sub 2 O sub 3 interfaces

    SciTech Connect

    Gao, Y.; Merkle, K.L.; Chang, H.L.M.; Zhang, T.J.; Lam, D. J.

    1990-11-01

    TiO{sub 2} thin films grown on (11{bar 2}0) sapphire at 800{degree}C by the MOCVD technique have been characterized by transmission electron microscopy. The TiO{sub 2} thin films are single crystalline and have the rutile structure. The epitaxial orientation relationship between the TiO{sub 2} thin films (R) and the substrate (S) has been found to be: (101)(0{bar 1}0){sub R}{parallel}(11{bar 2}0)(0001){sub S}. Growth twins in the films are commonly observed with the twin plane {l brace}101{r brace} and twinning direction {l angle}011{r angle}. Detailed atomic structures of the twin boundaries and TiO{sub 2}/{alpha}-Al{sub 2}O{sub 3} interfaces have been investigated by high-resolution electron microscopy (HREM). When the interfaces are viewed in the direction of (0{bar 1}0){sub R}/(0001){sub S}, the interfaces are found to be structurally coherent in the direction of ({bar 1}01){sub R}/(1{bar 1}00){sub S}, in which the lattice mismatch at the interfaces is about 0.5%. 8 refs., 4 figs.

  8. Power recovery of radiation damaged MOCVD grown indium phosphide on silicon solar cells through argon-ion laser annealing. Master`s thesis

    SciTech Connect

    Boyer, L.L.

    1996-06-01

    This thesis reports the results of a laser annealing technique used to remove defect sites from radiation damaged indium phosphide on silicon MOCVD grown solar cells. This involves the illumination of damaged solar cells with a continuous wave laser to produce a large forward-biased current. The InP/Si cells were irradiated with 1 MeV electrons to a given fluence, and tested for degradation. Light from an argon laser was used to illuminate four cells with an irradiance of 2.5 W/sq cm, producing a current density 3 to 5 times larger than AMO conditions. Cells were annealed at 19 deg C with the laser and at 25 deg C under AMO conditions. Annealing under laser illumination of n/p-type cells resulted in recovery of 48%. P/n type cells lost 4 to 12% of the assumed degradaton. Annealing under AMO conditions resulted in power recovery of 70% in n/p type cells. P/n-type cells recovered approximately 16% of lost power. Results indicate that significant power recovery results from the annealing of defects within n/p type InP/Si solar cells.

  9. High mobility, large linear magnetoresistance, and quantum transport phenomena in Bi2Te3 films grown by metallo-organic chemical vapor deposition (MOCVD).

    PubMed

    Jin, Hyunwoo; Kim, Kwang-Chon; Seo, Juhee; Kim, Seong Keun; Cheong, Byung-Ki; Kim, Jin-Sang; Lee, Suyoun

    2015-11-07

    We investigated the magnetotransport properties of Bi2Te3 films grown on GaAs (001) substrate by a cost-effective metallo-organic chemical vapor deposition (MOCVD). We observed the remarkably high carrier mobility and the giant linear magnetoresistance (carrier mobility ∼ 22 000 cm(2) V(-1) s(-1), magnetoresistance ∼ 750% at 1.8 K and 9 T for a 100 nm thick film) that depends on the film thickness. In addition, the Shubnikov-de Haas oscillation was observed, from which the effective mass was calculated to be consistent with the known value. From the thickness dependence of the Shubnikov-de Haas oscillation, it was found that a two dimensional electron gas with the conventional electron nature coexists with the topological Dirac fermion states and dominates the carrier transport in the Bi2Te3 film with thickness higher than 300 nm. These results are attributed to the intrinsic nature of Bi2Te3 in the high-mobility transport regime obtained by a deliberate choice of the substrate and the growth conditions.

  10. MOCVD Growth of High-Quality and Density-Tunable GaAs Nanowires on ITO Catalyzed by Au Nanoparticles Deposited by Centrifugation.

    PubMed

    Wu, Dan; Tang, Xiaohong; Yoon, Ho Sup; Wang, Kai; Olivier, Aurelien; Li, Xianqiang

    2015-12-01

    High-quality and density-tunable GaAs nanowires (NWs) are directly grown on indium tin oxide (ITO) using Au nanoparticles (NPs) as catalysts by metal organic chemical vapor deposition (MOCVD). Au catalysts were deposited on ITO glass substrate using a centrifugal method. Compared with the droplet-only method, high-area density Au NPs were uniformly distributed on ITO. Tunable area density was realized through variation of the centrifugation time, and the highest area densities were obtained as high as 490 and 120 NP/μm(2) for 10- and 20-nm diameters of Au NPs, respectively. Based on the vapor-liquid-solid growth mechanism, the growth rates of GaAs NWs at 430 °C were 18.2 and 21.5 nm/s for the highest area density obtained of 10- and 20-nm Au NP-catalyzed NWs. The growth rate of the GaAs NWs was reduced with the increase of the NW density due to the competition of precursor materials. High crystal quality of the NWs was also obtained with no observable planar defects. 10-nm Au NP-induced NWs exhibit wurtzite structure whereas zinc-blende is observed for 20-nm NW samples. Controllable density and high crystal quality of the GaAs NWs on ITO demonstrate their potential application in hybrid a solar cell.

  11. Novel Neo-Pentoxide Precursors for MOCVD Thin Films of TiO(2) and ZrO(2).[1

    SciTech Connect

    Boyle, Timothy J.; Francisco, Laila P.; Gallegos, Jesus J.; Rodriguez, Mark A.; Ward, Timothy L.

    1999-07-14

    Two novel Group IV precursors, titanium (IV) neo-pentoxide, [Ti({mu}-ONep)(ONep){sub 3}]{sub 2} (l), and zirconium (IV) neo-pentoxide, [Zr({mu}-ONep)(ONep){sub 3}]{sub 2} (2), were reported to possess relatively high volatility at low temperatures. These compounds were therefore investigated as MOCVD precursors using a lamp-heated cold-wall CVD reactor and direct sublimation without carrier gas. The ONep derivatives proved to be competitive precursors for the production of thin films of the appropriate MO{sub 2} (M = Ti or Zr) materials in comparison to other metallo-organic precursors. Compound 1 was found to sublime at 120 C with a deposition rate of {approximately}0.350 {mu}m/min onto a substrate at 330 C forming the anatase phase with < 1% residual C found in the final film. Compound 2 was found to sublime at 160 C and deposited as crystalline material at 300 C with < 1% residual C found in the final film. A comparison to standard alkoxide and {beta}-diketonates is presented where appropriate.

  12. Selective-Area MOCVD Growth and Carrier-Transport-Type Control of InAs(Sb)/GaSb Core-Shell Nanowires.

    PubMed

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Yang, Tao

    2016-12-14

    We report the first selective-area growth of high quality InAs(Sb)/GaSb core-shell nanowires on Si substrates using metal-organic chemical vapor deposition (MOCVD) without foreign catalysts. Transmission electron microscopy (TEM) analysis reveals that the overgrowth of the GaSb shell is highly uniform and coherent with the InAs(Sb) core without any misfit dislocations. To control the structural properties and reduce the planar defect density in the self-catalyzed InAs core nanowires, a trace amount of Sb was introduced during their growth. As the Sb content increases from 0 to 9.4%, the crystal structure of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB) structure to a perfect ZB phase. Electrical measurements reveal that both the n-type InAsSb core and p-type GaSb shell can work as active carrier transport channels, and the transport type of core-shell nanowires can be tuned by the GaSb shell thickness and back-gate voltage. This study furthers our understanding of the Sb-induced crystal-phase control of nanowires. Furthermore, the high quality InAs(Sb)/GaSb core-shell nanowire arrays obtained here pave the foundation for the fabrication of the vertical nanowire-based devices on a large scale and for the study of fundamental quantum physics.

  13. Properties variation with composition of single-crystal Pb(Zr{sub x}Ti{sub 1-x})O{sub 3} thin films prepared by MOCVD

    SciTech Connect

    Foster, C.M.; Bai, G.R.; Li, Z.; Jammy, R.; Wills, L.A.; Hiskes, R.

    1995-12-01

    Single-crystal thin films covering the full range of PZT 0{le}x{le}1 have been deposited by metal-organic chemical vapor deposition (MOCVD). The films were grown on epitaxial, RF-sputter-deposited SrRuO{sub 3} thin film electrodes on (001) SrTiO{sub 3} substrates. X-ray diffraction, energy-dispersive electron spectroscopy and optical waveguiding were used to characterize the crystalline structure, composition, refractive index, and film thickness. We found that the PZT films were single-crystalline for all compositions exhibiting cube-on-cube epitaxy with the substrate with very high degrees of crystallinity and orientation. We report the systematic variations in the optical, dielectric, polarization, and transport properties as a function of composition and the epitaxy-induced modifications in the solid-solution phase diagram of this system. These films exhibited electronic properties which showed clear systematic variations with composition. High values of remnant polarization (30--55 {mu}C/cm{sup 2}) were observed at all ferroelectric compositions. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225--650. Coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm at the (70/30) composition. In addition, these films exhibited both high resistivity and dielectric-breakdown strength ({approximately}10{sup 13} {Omega}-cm at 100 kV/cm and >300 kV/cm, respectively) without any compensative doping.

  14. Influence of high-temperature AlN intermediate layer on the optical properties of MOCVD grown AlGaN films

    NASA Astrophysics Data System (ADS)

    Xie, Deng; Qiu, Zhi Ren; Liu, Yao; Talwar, Devki N.; Wan, Lingyu; Zhang, Xiong; Mei, Ting; Ferguson, Ian T.; Feng, Zhe Chuan

    2017-02-01

    By combining spectroscopic ellipsometry (SE) and optical transmission (OT) characterization methods we have systematically investigated the influence of AlN intermediate layer and AlN transition layer on the optical properties of AlGaN epilayers grown on sapphire by metalorganic chemical vapor deposition (MOCVD) method. Most dielectric functions of III-nitrides obtained by different research groups show significant band-tail absorption—which is not anticipated for such a direct band gap material. The dielectric functions are studied for a series of AlGaN/AlN/Al2O3 structures, with a four-layer model taking into account both high temperature grown AlN layer and low temperature grown AlN layer. The results obtained by fitting the optical parameters to experimental data show that the band-tail absorption should originate from the transition layer. AlGaN film without high temperature AlN epilayer exhibited a redshift of band gap around 0.24 eV.

  15. Low-temperature MOCVD growth of oriented PbZr{sub x}Ti{sub 1-x}O{sub 3} thin films on Si substrates.

    SciTech Connect

    Chen, N.

    1998-05-08

    Polycrystalline Pb(Zr{sub 0.6}Ti{sub 0.4})O{sub 3} (PZT) thin films, 3000-6000 {angstrom} thick, have been grown by metal-organic chemical vapor deposition (MOCVD) on (111)Pt/Ti/SiO{sub 2}/Si substrates at temperatures as low as 450-525 C. Random and (111)-oriented, or occasionally (100)-oriented, PZT films can be deposited directly on (111)Pt/Ti/SiO{sub 2}/Si. In addition, highly (100)-oriented films can be deposited consistently by using 150-250 {angstrom} thick (100)-oriented PbTiO{sub 3} (PT) or TiO{sub 2} as a template. Films were characterized by X-ray diffraction, electron microscopy, and electrical measurements. The as-grown (100)-oriented films on (111)Pt/TiSiO{sub 2}/Si substrates exhibited dielectric constants ({var_epsilon}{sub r}) of up to 600, remnant polarization (P{sub r}) of 40 {micro}C/cm{sup 2}, coercive field of 55 kV/cm, and breakdown field of 2-6 x 10{sub 7} V/m.

  16. Impact of photoluminescence temperature and growth parameter on the exciton localized in BxGa1-xAs/GaAs epilayers grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Hidouri, Tarek; Saidi, Faouzi; Maaref, Hassen; Rodriguez, Philippe; Auvray, Laurent

    2016-10-01

    In this work, BxGa1-xAs/GaAs epilayers with three different boron compositions were elaborated by metal organic chemical vapor deposition (MOCVD) on GaAs (001) substrate. Structural study using High resolution X-ray diffraction (HRXRD) spectroscopy and Atomic Force Microscopy (AFM) have been used to estimate the boron fraction. The luminescence keys were carried out as functions of temperature in the range 10-300 K, by the techniques of photoluminescence (PL). The low PL temperature has shown an abnormal emission appeared at low energy side witch attributed to the recombination through the deep levels. In all samples, the PL peak energy and the full width at half maximum (FWHM), present an anomalous behavior as a result of the competition process between localized and delocalized carriers. We propose the Localized-state Ensemble model to explain the unusual photoluminescence behaviors. Electrical carriers generation, thermal escape, recapture, radiative and non-radiative lifetime are taken into account. The temperature-dependent photoluminescence measurements were found to be in reasonable agreement with the model of localized states. We controlled the evolution of such parameters versus composition by varying the V/III ratio to have a quantitative and qualitative understanding of the recombination mechanisms. At high temperature, the model can be approximated to the band-tail-state emission.

  17. Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoqing; Zhong, Jiebin; So, Hongyun; Norvilas, Aras; Sommerhalter, Christof; Senesky, Debbie G.; Tang, Mary

    2016-11-01

    In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG) properties of AlGaN/GaN high electron mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition (MOCVD) on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72%) across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/Vṡs at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/Vṡs which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

  18. Physical property analysis of C-doped GaAs as function of the carrier concentration grown by MOCVD using elemental arsenic as precursor

    NASA Astrophysics Data System (ADS)

    Díaz-Reyes, J.; Avendaño, M. A.; Galván-Arellano, M.; Peña-Sierra, R.

    2006-03-01

    This work presents the characterization of GaAs layers grown in a metallic-arsenic-based-MOCVD system. The gallium precursor was the compound trimethylgallium (TMG) and elemental arsenic as precursor of arsenic. The most important parameters of the growth process include the substrate temperature and the composition of the carrier gas; an N2+H2 gas mixture. The influence of carbon doping on the optical and electrical properties of GaAs layers have been studied by photoluminescence (PL) spectroscopy, Photoreflectance (PR) and Hall Effect measurements. To carry out doping with carbon in the range of around 1016 to 1020 cm-3, it was necessary to modifying the hydrogen activity in the reacting atmosphere with the control of the N{2}+H{2}, mixture which was used as carrier gas. The PL response of the samples is strongly dependent on the growth temperature and showed mainly two radiative transitions, band-to-band and band-to C-acceptor. PR spectra present transitions associated to GaAs. Besides, short period oscillations near the GaAs band-gap energy are observed, interpreted as Franz-Keldysh oscillations associated to the hole-ionized acceptor (h-A-) pair modulations. For investigating the chemical bonds of impurity-related species in the GaAs layers optical absorption was measured using a FT-IR spectrometer. Device quality GaAs layers have been grown in a broad range of growth temperatures.

  19. Drift chambers in BM@N Experiment

    NASA Astrophysics Data System (ADS)

    Fedorišin, Ján

    2017-03-01

    Drift chambers (DCH) constitute an important part of the tracking system of BM@N experiment designed to study the production of baryonic matter at the Nuclotron energies. The method of particle hit and track reconstruction in the drift chambers is proposed and tested on the BM@N deuteron beam data. In first step, the radius vs drift time calibration curve is estimated and applied to calculate DCH hit closest approach coordinates. These coordinates are used to construct hits in each DCH under the assumption of track linearity. Hits in both the DCHs are subsequently aligned and fitted to produce global linear track candidates. Eventually the hit and track reconstruction is optimized by the autocalibration method. The coordinate resolutions are estimated from Gaussian fits of the DCH hit residual spectra for different DCH planes. Furthermore, the deuteron beam momentum value is reconstructed in order to check reliability of the employed track reconstruction algorithm.

  20. Tailored vacuum chambers for ac magnets

    SciTech Connect

    Harvey, A.

    1985-01-01

    The proposed LAMPF-II accelerator has a 60-Hz booster synchrotron and a 3-Hz main ring. To provide a vacuum enclosure inside the magnets with low eddy-current losses and minimal field distortion, yet capable of carrying rf image currents and providing beam stabilization, we propose an innovative combination pipe. Structurally, the enclosure is high-purity alumina ceramic, which is strong, radiation resistant, and has good vacuum properties. Applied to the chamber are thin, spaced, silver conductors using adapted thick-film technology. The conductor design can be tailored to the stabilization requirements, for example, longitudinal conductors for image currents, circumferential for transverse stabilization. The inside of the chamber has a thin, resistive coating to avoid charge build-up. The overall 60-Hz power loss is less than 100 W/m.

  1. Method of electroforming a rocket chamber

    NASA Technical Reports Server (NTRS)

    Fortini, A. (Inventor)

    1974-01-01

    A transpiration cooled rocket chamber is made by forming a porous metal wall on a suitably shaped mandrel. The porous wall may be made of sintered powdered metal, metal fibers sintered on the mandrel or wires woven onto the mandrel and then sintered to bond the interfaces of the wires. Intersecting annular and longitudinal ribs are then electroformed on the porous wall. An interchamber wall having orifices therein is then electroformed over the annular and longitudinal ribs. Parallel longitudinal ribs are then formed on the outside surface of the interchamber wall after which an annular jacket is electroformed over the parallel ribs to form distribution passages therewith. A feed manifold communicating with the distribution passages may be fabricated and welded to the rocket chamber or the feed manifold may be electroformed in place.

  2. Bubble chamber as a trace chemical detector.

    PubMed

    Luo, X; McCreary, E I; Atencio, J H; McCown, A W; Sander, R K

    1998-08-20

    A novel concept for trace chemical analysis in liquids has been demonstrated. The technique utilizes light absorption in a superheated liquid. Although a superheated liquid is thermodynamically unstable, a high degree of superheating can be dynamically achieved for a short period of time. During this time the superheated liquid is extremely sensitive to boiling at nucleation sites produced by energy deposition. Observation of bubbles in the superheated liquid in some sense provides amplification of the initial energy deposition. Bubble chambers containing superheated liquids have been used to detect energetic particles; now a bubble chamber is used to detect a trace chemical in superheated liquid propane by observing bubble formation initiated by optical absorption. Crystal violet is used as a test case and can be detected at the subpart-per-10(12) level by using a Nd:YAG laser. The mechanism for bubble formation and ideas for further improvement are discussed.

  3. Space station auxiliary thrust chamber technology

    NASA Technical Reports Server (NTRS)

    Senneff, J. M.

    1987-01-01

    A program to design, fabricate, and test a 50 lb sub f (222 N) thruster was undertaken to demonstrate the applicability of the reverse flow concept as an item of auxillary propulsion for the Space Station. The thruster was to operate at a mixture ratio (O/F) of 4, be capable of operating for 2 million lb sub f-seconds (8.896 million N-seconds) impulse with a chamber pressure of 75 psia (52N/sq cm) and a nozzle area ratio of 40. A successful demonstration of an (0/F) of 4 thruster, was followed by the design objective of operating at (O/F) of 8. The demonstration of this thruster resulted in the order of and additional (O/F) of 8 thruster chamber under the present NAS 3-24883 contract. The effort to fabricate and test the second (0/F) of 8 thruster is documented.

  4. Lightweight Chambers for Thrust Cell Applications

    NASA Technical Reports Server (NTRS)

    Elam, Sandy; Effinger, Mike; Holmes, Dick; Lee, Jonathan; Jaskowiak, Martha; Turner, Jim E. (Technical Monitor)

    2000-01-01

    This is a viewgraph presentation which reviews the progress in the development of lightweight chambers for thrust cell applications. The objective of the program is to reduce thrust assembly weights to create lighter engines which will allow for an increase in the payload. Using new composite materials and fabrication technologies the team has constructed 7 different thrust cell demonstration units. The materials used in the demonstration units are reviewed.

  5. CFD Code Survey for Thrust Chamber Application

    NASA Technical Reports Server (NTRS)

    Gross, Klaus W.

    1990-01-01

    In the quest fo find analytical reference codes, responses from a questionnaire are presented which portray the current computational fluid dynamics (CFD) program status and capability at various organizations, characterizing liquid rocket thrust chamber flow fields. Sample cases are identified to examine the ability, operational condition, and accuracy of the codes. To select the best suited programs for accelerated improvements, evaluation criteria are being proposed.

  6. Development of sputtered techniques for thrust chambers

    NASA Technical Reports Server (NTRS)

    Mullaly, J. R.; Allard, P. A.

    1979-01-01

    The 0.152 cm thick sputtered and copper deposits were electron beam welded to wrought copper. Tensile specimens were machined from the weld assemblies and tested at room temperature. Tensile strength approached the strength of wrought material. Elongations up to 25% were measured. Sputtered aluminum was used to fill 0.157 cm wide by 0.127 cm deep grooves in thrust chamber spool piece liners. The liners were closed out by sputtering copper from post and hollow cathodes.

  7. Image digitizer system for bubble chamber laser

    SciTech Connect

    Haggerty, H

    1986-12-08

    An IBM PC-based image digitizer system has been assembled to monitor the laser flash used for holography at the 15 foot bubble chamber. The hardware and the operating software are outlined. For an operational test of the system, an array of LEDs was flashed with a 10 microsecond pulse and the image was grabbed by one of the operating programs and processed. (LEW)

  8. Compact Vapor Chamber Cools Critical Components

    NASA Technical Reports Server (NTRS)

    2015-01-01

    Advancements in the production of proton exchange membrane fuel cells have NASA considering their use as a power source for spacecraft and robots in future space missions. With SBIR funding from Glenn Research Center, Lancaster, Pennsylvania-based Thermacore Inc. developed strong, lightweight titanium vapor chambers to keep the fuel cells operating at optimum temperatures. The company is now selling the technology for cooling electronic components.

  9. Iris fixation of posterior chamber intraocular lenses.

    PubMed

    Yazdani-Abyaneh, Alireza; Djalilian, Ali R; Fard, Masoud Aghsaei

    2016-12-01

    We introduce a technique for iris fixation of a posterior chamber intraocular lens (IOL) in which most of the procedure is done outside the eye. This minimizes intraocular manipulation, maximizes corneal endothelial preservation, and avoids the risk for IOL drop into the vitreous cavity intraoperatively. The IOL is fixated to the most peripheral part of the iris, resulting in a rounder pupil. Sutures are placed at exact positions on the haptics, resulting in a well-centered IOL.

  10. A Nanosecond Pulse Generator for Spark Chambers,

    DTIC Science & Technology

    1979-12-04

    nsec. The generator consists of an Arkad’yev- Marx generator (impulse voltage generator - GIN), a stor- age capacitor and discharge chamber (nanosecond...the generator is given in fig. 2. El. Fig. 1. Generator circuit diagram. 1 - NOM-10 transformer; 2 - filament transformer; 3 - Arkad’yev- Marx ...charge circuit abcd, the primary current will initially be given to the load by Cg, not by the surge capacitance of the Arkad’yev- Marx generator. The

  11. Visual-Inspection Probe For Cryogenic Chamber

    NASA Technical Reports Server (NTRS)

    Friend, Steve; Valenzuela, James; Yoshinaga, Jay

    1990-01-01

    Visual-inspection probe that resembles borescope enables observer at ambient temperature to view objects immersed in turbulent flow of liquid oxygen, liquid nitrogen, or other cryogenic fluid. Design of probe fairly conventional, except special consideration given to selection of materials and to thermal expansion to provide for expected range of operating temperatures. Penetrates wall of cryogenic chamber to provide view of interior. Similar probe illuminates scene. View displayed on video monitor.

  12. USAF Hyperbaric Animal Transfer Chamber System.

    DTIC Science & Technology

    1988-01-01

    gauge stainless-steel woven wire cloth. Cage floors are 1/2-in. mesh, 12-gauge, polished stainless-steel woven cloth. All edges and corners are... diaper , paper, or sponge. The additional humidity in the chamber environment will help eliminate the problem of static discharge from the animal’s dry...Compressed gas cylinders should be sampled before initial use and after any major repairs. During extended periods of non -use, the syste,, should ol

  13. Crosstalk Studies of a Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Ryer, Jonathan

    2008-10-01

    The crosstalk between various pads of a Time Projection Chamber (TPC) developed for the experiment MuSun was studied. Crosstalk between TPC pads must be studied and understood in order for proper muon path reconstruction to be obtained. A printed circuit board was developed to use capacitive coupling to transmit a signal pulse onto the TPC, where the crosstalk of the transmitted signal was studied.

  14. High pressure hydrogen time projection chamber

    SciTech Connect

    Goulianos, K.

    1983-01-01

    We describe a high pressure hydrogen gas time projection chamber which consists of two cylindrical drift regions each 45 cm in diameter and 75 cm long. Typically, at 15 atm of H/sub 2/ with 2 kV/cm drift field and 7 kV on the 35..mu.. sense wires, the drift velocity is about 0.5 cm/..mu..sec and the spatial resolution +-200..mu...

  15. Magma chamber dynamics and Vesuvius eruption forecasting

    NASA Astrophysics Data System (ADS)

    Dobran, F.

    2003-04-01

    Magma is continuously or periodically refilling an active volcano and its eruption depends on the mechanical, fluid, thermal, and chemical aspects of the magma storage region and its surroundings. A cyclically loaded and unloaded system can fail from a weakness in the system or its surroundings, and the fluctuating stresses can produce system failures at stress levels that are considerably below the yield strength of the material. Magma in a fractured rock system within a volcano is unstable and propagates toward the surface with the rate depending on the state of the system defined by the inertia, gravity, friction, and permeability parameters of magma and its source region. Cyclic loading and unloading of magma from a reservoir caused by small- or medium-scale eruptions of Vesuvius can produce catastrophic plinian eruptions because of the structural failure of the system and the quiescent periods between these eruptions increase with time until the next eruption cycle which will be plinian or subplinian and will occur with a very high probability this century. Such a system behavior is predicted by a Global Volcanic Simulator of Vesuvius developed for simulating different eruption scenarios for the purpose of urban planning the territory, reducing the number of people residing too close to the cone of the volcano, and providing safety to those beyond about 5 km radius of the crater. The magma chamber model of the simulator employs a thermomechanical model that includes magma inflow and outflow from the chamber, heat and mass transfer between the chamber and its surroundings, and thermoelastoplastic deformation of the shell surrounding the magma source region. These magma chamber, magma ascent, and pyroclastic dispersion models and Vesuvius eruption forecasting are described in Dobran, F., VOLCANIC PROCESSES, Kluwer Academic/Plenum Publishers, 2001, 590 pp.

  16. Chamber For Testing Polymers In Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F.

    1990-01-01

    Apparatus holds polymer specimen at constant temperature while exposing it to oxygen plasma. Copper tube (part of cooling coil) extends into plasma chamber, supporting copper block and thermoelectric module on which specimen mounted. Copper block made small - 4.4 by 3.8 by 1.6 cm - having little effect on plasma. Used to evaluate resistances of polymer materials to plasma environments, and for analysis of gases produced by attack of plasma on polymer specimen.

  17. Visual-Inspection Probe For Cryogenic Chamber

    NASA Technical Reports Server (NTRS)

    Friend, Steve; Valenzuela, James; Yoshinaga, Jay

    1990-01-01

    Visual-inspection probe that resembles borescope enables observer at ambient temperature to view objects immersed in turbulent flow of liquid oxygen, liquid nitrogen, or other cryogenic fluid. Design of probe fairly conventional, except special consideration given to selection of materials and to thermal expansion to provide for expected range of operating temperatures. Penetrates wall of cryogenic chamber to provide view of interior. Similar probe illuminates scene. View displayed on video monitor.

  18. Space Station Live: Historic Vacuum Chamber to Test Webb Telescope

    NASA Image and Video Library

    NASA Public Affairs Officer Dan Huot recently visited Johnson Space Center’s 400,000 cubic foot vacuum chamber, Chamber A, and spoke with Mary Cerimele, the lab manager for this historic facility.

  19. DETAIL OF VACUUM PIPE OPENING WITHIN ALTITUDE CHAMBER R, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF VACUUM PIPE OPENING WITHIN ALTITUDE CHAMBER R, FACING SOUTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  20. DESIGN, CONSTRUCTION, AND EVALUATION OF A CHAMBER FOR AEROBIOLOGY

    EPA Science Inventory

    A chamber was designed and constructed for aeromicrobiology applications. An ultraviolet (UV) radiation source was incorporated to sterilize the chamber between trials. Twelve bacterial species originally isolated from air samples and obtained from the American Type Culture Colle...

  1. Vacuum Chamber Documentation for U of H Collection

    NASA Image and Video Library

    2006-06-16

    Documentation for the University of Houston (UH) Clear Lake collection of their library books after the Vacuum Chamber runs were performed to remove the water from them. Vacuum Chamber B in Building 32 was used.

  2. INTERIOR OF ALTITUDE CHAMBER L FROM TOP LEVEL OF ACCESS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF ALTITUDE CHAMBER L FROM TOP LEVEL OF ACCESS PLATFORMS, FACING WEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  3. EXTERIOR VIEW OF AIRLOCK FOR ALTITUDE CHAMBER R, FACING SOUTHEAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EXTERIOR VIEW OF AIRLOCK FOR ALTITUDE CHAMBER R, FACING SOUTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  4. UPPER HALF OF THE INTERIOR OF ALTITUDE CHAMBER R, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    UPPER HALF OF THE INTERIOR OF ALTITUDE CHAMBER R, LOOKING UP FROM BOTTOM LEVEL, FACING NORTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  5. INTERIOR OF ALTITUDE CHAMBER L, LOOKING UP FROM BOTTOM LEVEL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF ALTITUDE CHAMBER L, LOOKING UP FROM BOTTOM LEVEL OF INTERNAL PLATFORMS, FACING EAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  6. EXTERIOR OF ALTITUDE CHAMBERS R (TO LEFT) AND L (TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EXTERIOR OF ALTITUDE CHAMBERS R (TO LEFT) AND L (TO RIGHT), FACING NORTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  7. VIEW OF THE CONTROL ROOM FOR THE ALTITUDE CHAMBERS, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF THE CONTROL ROOM FOR THE ALTITUDE CHAMBERS, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  8. BOTTOM LEVEL OF ALTITUDE CHAMBER L, FACING SOUTHWEST Cape ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOTTOM LEVEL OF ALTITUDE CHAMBER L, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  9. DETAIL OF DOMED BOTTOM, ALTITUDE CHAMBER R, FACING EAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF DOMED BOTTOM, ALTITUDE CHAMBER R, FACING EAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  10. VIEW OF PUMP ROOM FOR ALTITUDE CHAMBERS, FACING SOUTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF PUMP ROOM FOR ALTITUDE CHAMBERS, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  11. EXTERIOR AND INTERIOR VIEW OF AIRLOCK FOR ALTITUDE CHAMBER R, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EXTERIOR AND INTERIOR VIEW OF AIRLOCK FOR ALTITUDE CHAMBER R, FACING SOUTH - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  12. DETAIL OF REPRESSURIZATION AIR PIPE, ALTITUDE CHAMBER L, FACING SOUTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF RE-PRESSURIZATION AIR PIPE, ALTITUDE CHAMBER L, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  13. DETAIL OF DOMED BOTTOM, ALTITUDE CHAMBER L, FACING NORTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF DOMED BOTTOM, ALTITUDE CHAMBER L, FACING NORTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  14. DETAIL OF WALLMOUNTED STAIRS ON INTERIOR OF ALTITUDE CHAMBER L, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF WALL-MOUNTED STAIRS ON INTERIOR OF ALTITUDE CHAMBER L, FACING SOUTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  15. INTERIOR OF AIRLOCK FROM INTERIOR OF ALTITUDE CHAMBER R, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF AIRLOCK FROM INTERIOR OF ALTITUDE CHAMBER R, FACING NORTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  16. LOWER HALF OF THE INTERIOR OF ALTITUDE CHAMBER R, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LOWER HALF OF THE INTERIOR OF ALTITUDE CHAMBER R, LOOKING UP FROM BOTTOM LEVEL, FACING NORTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  17. DETAIL OF PLATFORM SUPPORT BRACKET, ALTITUDE CHAMBER L, FACING NORTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF PLATFORM SUPPORT BRACKET, ALTITUDE CHAMBER L, FACING NORTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  18. INTERIOR OF ALTITUDE CHAMBER R, LOOKING DOWN FROM AIRLOCK, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF ALTITUDE CHAMBER R, LOOKING DOWN FROM AIRLOCK, FACING NORTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  19. EXTERIOR OF ALTITUDE CHAMBERS R (TO LEFT) AND L (TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EXTERIOR OF ALTITUDE CHAMBERS R (TO LEFT) AND L (TO RIGHT), FACING NORTHWEST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  20. Andy Chambers Homestead, Chicken Coop, Saddle Shop, and Granary, looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Andy Chambers Homestead, Chicken Coop, Saddle Shop, and Granary, looking northeast - Andy Chambers Homestead, 0.4 mile south of Antelope Flats Road on the east side of Mormon Row Road, Kelly, Teton County, WY