Science.gov

Sample records for algaas top solar

  1. Development of N/P AlGaAs free-standing top solar cells for tandem applications

    NASA Technical Reports Server (NTRS)

    Negley, Gerald H.; Dinetta, Louis C.; Cummings, John R.; Hannon, Margaret H.; Sims, Paul E.; Barnett, Allen M.

    1991-01-01

    The combination of a free standing AlGaAs top solar cell and an existing bottom solar cell is the highest performance, lowest risk approach to implementing the tandem cell concept. The solar cell consists of an AlGaAs substrate layer, an AlGaAs base layer, an AlGaAs emitter, and an ultra-thin AlGaAs window layer. The window layer is compositionally graded which minimizes reflection at the window layer/emitter interface and creates a built-in electric field to improve quantum response in the blue region of the spectrum. Liquid phase epitaxy (LPE) is the only viable method to produce this free standing top solar cell. Small (0.125 sq cm), transparent p/n AlGaAs top solar cells were demonstrated with optimum bandgap for combination with a silicon bottom solar cell. The efficiency of an AlGaAs/Si stack using the free standing AlGaAs device upon an existing silicon bottom solar cell is 24 pct. (1X, Air Mass Zero (AM0). The n/p AlGaAs top solar cell is being developed in order to facilitate the wiring configuration. The two terminal tandem stack will retain fit, form, and function of existing silicon solar cells. Progress in the development of large area (8 and 16 sq cm), free standing AlGaAs top solar cells is discussed.

  2. AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

    NASA Technical Reports Server (NTRS)

    Dinetta, L. C.; Hannon, M. H.; Mcneely, J. B.; Barnett, A. M.

    1991-01-01

    The AstroPower self-supporting, transparent AlGaAs top solar cell can be stacked upon any well-developed bottom solar cell for improved system performance. This is an approach to improve the performance and scale of space photovoltaic power systems. Mechanically stacked tandem solar cell concentrator systems based on the AlGaAs top concentrator solar cell can provide near term efficiencies of 36 percent (AMO, 100x). Possible tandem stack efficiencies greater than 38 percent (100x, AMO) are feasible with a careful selection of materials. In a three solar cell stack, system efficiencies exceed 41 percent (100x, AMO). These device results demonstrate a practical solution for a state-of-the-art top solar cell for attachment to an existing, well-developed solar cell.

  3. A three solar cell system based on a self-supporting, transparent AlGaAs top solar cell

    NASA Technical Reports Server (NTRS)

    Negley, Gerald H.; Rhoads, Sandra L.; Terranova, Nancy E.; Mcneely, James B.; Barnett, Allen M.

    1989-01-01

    Development of a three solar cell stack can lead to practical efficiencies greater than 30 percent (1x,AM0). A theoretical efficiency limitation of 43.7 percent at AM0 and one sun is predicted by this model. Including expected losses, a practical system efficiency of 36.8 percent is anticipated. These calculations are based on a 1.93eV/1.43eV/0.89eV energy band gap combination. AlGaAs/GaAs/GaInAsP materials can be used with a six-terminal wiring configuration. The key issues for multijunction solar cells are the top and middle solar cell performance and the sub-bandgap transparency. AstroPower has developed a technique to fabricate AlGaAs solar cells on rugged, self-supporting, transparent AlGaAs substrates. Top solar cell efficiencies greater than 11 percent AM0 have been achieved. State-of-the-art GaAs or InP devices will be used for the middle solar cell. GaInAsP will be used to fabricate the bottom solar cell. This material is lattice-matched to InP and offers a wide range of bandgaps for optimization of the three solar cell stack. Liquid phase epitaxy is being used to grow the quaternary material. Initial solar cells have shown open-circuit voltages of 462 mV for a bandgap of 0.92eV. Design rules for the multijunction three solar cell stack are discussed. The progress in the development of the self-supporting AlGaAs top solar cell and the GaInAsP bottom solar cell is presented.

  4. AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

    NASA Technical Reports Server (NTRS)

    Dinetta, L. C.; Hannon, M. H.; Cummings, J. R.; Mcneeley, J. B.; Barnett, Allen M.

    1990-01-01

    Free-standing, transparent, tunable bandgap AlxGa1-xAs top solar cells have been fabricated for mechanical attachment in a four terminal tandem stack solar cell. Evaluation of the device results has demonstrated 1.80 eV top solar cells with efficiencies of 18 percent (100 X, and AM0) which would yield stack efficiencies of 31 percent (100 X, AM0) with a silicon bottom cell. When fully developed, the AlxGa1-xAs/Si mechanically-stacked two-junction solar cell concentrator system can provide efficiencies of 36 percent (AM0, 100 X). AlxGa1-xAs top solar cells with bandgaps from 1.66 eV to 2.08 eV have been fabricated. Liquid phase epitaxy (LPE) growth techniques have been used and LPE has been found to yield superior AlxGa1-xAs material when compared to molecular beam epitaxy and metal-organic chemical vapor deposition. It is projected that stack assembly technology will be readily applicable to any mechanically stacked multijunction (MSMJ) system. Development of a wide bandgap top solar cell is the only feasible method for obtaining stack efficiencies greater than 40 percent at AM0. System efficiencies of greater than 40 percent can be realized when the AlGaAs top solar cell is used in a three solar cell mechanical stack.

  5. Graded-bandgap AlGaAs solar cells for AlGaAs/Ge cascade cells

    NASA Technical Reports Server (NTRS)

    Timmons, M. L.; Venkatasubramanian, R.; Colpitts, T. S.; Hills, J. S.; Hutchby, J. A.; Iles, P. A.; Chu, C. L.

    1991-01-01

    Some p/n graded-bandgap Al(x)Ga(1-x)As solar cells were fabricated and show AMO conversion efficiencies in excess of 15 percent without antireflection (AR) coatings. The emitters of these cells are graded between 0.008 is less than or equal to x is less than or equal to 0.02 during growth of 0.25 to 0.30 micron thick layers. The keys to achieving this performance were careful selection of organometallic sources and scrubbing oxygen and water vapor from the AsH3 source. Source selection and growth were optimized using time-resolved photoluminescence. Preliminary radiation-resistance measurements show AlGaAs cells degraded less than GaAs cells at high 1 MeV electron fluences, and AlGaAs cells grown on GaAs and Ge substrates degrade comparably.

  6. GaAs/AlGaAs quantum wells with indirect-gap AlGaAs barriers for solar cell applications

    SciTech Connect

    Noda, T. Otto, L. M.; Elborg, M.; Jo, M.; Mano, T.; Kawazu, T.; Han, L.; Sakaki, H.

    2014-03-24

    We have fabricated GaAs/AlGaAs quantum well (QW) solar cells in which 3 nm-thick QWs and indirect-gap Al{sub 0.78}Ga{sub 0.22}As barriers are embedded, and we studied extraction processes of photogenerated carriers in this QW system. The photocurrent under 700 nm light illumination at voltages close to the open-circuit voltage shows only a small reduction, indicating that the carrier recombination inside QWs is largely suppressed. We attribute this result to an efficient extraction of electrons from the QWs through the X-valley of AlGaAs. The insertion of QWs is shown to be effective in extending the absorption wavelengths and in enhancing the photocurrent. The use of indirect-gap materials as barriers is found to enhance carrier extraction processes, and result in an improved performance of QW solar cells.

  7. Method of Making Self-Aligned GAAS/ALGAAS FET’s.

    DTIC Science & Technology

    having a predetermined crystalline structure is obtained having a heavily doped top GaAs layer, having a heavily doped AlGaAs layer under the top layer...recess is wider at the base of the recess than at the top of the recess because of the predetermined crystalline structure and the orientation-dependent

  8. Top-grid monolayer graphene/Si Schottkey solar cell

    SciTech Connect

    Wang, Yusheng; Chen, Caiyun; Fang, Xiao; Li, Zhipeng; Qiao, Hong; Sun, Baoquan; Bao, Qiaoliang

    2015-04-15

    Monolayer graphene/Si Schottkey solar cell was fabricated using a top-grid structure. In comparison with the prevailing “top-window” structure, the newly-designed device structure has simplified the fabrication procedures to avoid ultraviolet (UV) photolithography and SiO{sub 2}-eching. We systematically investigated the effect of chemical doping as well as device area on the device performance. It was found that a power conversion efficiency (PCE) of 5.9% can be achieved by engineering the work function of graphene through chemical doping. Our study indicates that top grid structure is suitable to make low-cost, large area and high efficiency graphene/Si Schottkey solar cell. - Graphical abstract: The engineering of the work function of graphene through chemical doping is an effective approach to improve the performance of monolayer graphene/Si Schottky solar cell. - Highlights: • Monolayer graphene/Si Schottkey solar cell was fabricated. • Chemical doping can effectively tune the work function of graphene film. • Chemical doping has significant effect on the device performance. • The top-grid device structure with graphene is promising with low-cost and high efficiency.

  9. Exterior direct view of (nonoriginal), solar heating panels, and top ...

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

    Exterior direct view of (non-original), solar heating panels, and top of typical rectangular trash-dump tower at roof of Building 6, looking north - North Beach Place, 401 Bay Street, 500 Francisco Street, 401 Bay Street, 500 Francisco Street, San Francisco, San Francisco County, CA

  10. Enhanced solar energy harvesting using top n-contact GaAs solar cell

    NASA Astrophysics Data System (ADS)

    Das, N. C.

    2015-05-01

    We fabricated single-junction solar cell on molecular beam epitaxially grown p-n junction on n-type gallium arsenide (GaAs) substrate. We used a germanium (Ge)/gold (Au)/nickel (Ni)/Au metal contact from the top side on a highly doped n+ epitaxial layer as well as the bottom side on an n-type GaAs substrate. We observed 10-15% increase in solar cell power when the top contact is used for the n+ GaAs epi layer compared to the bottom side n-type GaAs substrate. Solar cell fill factor, sheet, and shunt resistances are same for both the top and bottom contact type devices. We also observed higher external quantum efficiency (EQE) for top contact devices compared to bottom contact devices. We conclude that to achieve higher power, it is advantageous to use an n-type contact from a highly doped top n+ epitaxial layer rather than a bottom n-type GaAs substrate.

  11. GaAs, AlGaAs and InGaP Tunnel Junctions for Multi-Junction Solar Cells Under Concentration: Resistance Study

    SciTech Connect

    Wheeldon, Jeffrey F.; Valdivia, Christopher E.; Walker, Alex; Kolhatkar, Gitanja; Hall, Trevor J.; Hinzer, Karin; Masson, Denis; Riel, Bruno; Fafard, Simon; Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent

    2010-10-14

    The following four TJ designs, AlGaAs/AlGaAs, GaAs/GaAs, AlGaAs/InGaP and AlGaAs/GaAs are studied to determine minimum doping concentration to achieve a resistance of <10{sup -4} {omega}{center_dot}cm{sup 2} and a peak tunneling current suitable for MJ solar cells up to 1500-suns concentration (operating current of 21 A/cm{sup 2}). Experimentally calibrated numerical models are used to determine how the resistance changes as a function of doping concentration. The AlGaAs/GaAs TJ design is determined to require the least doping concentration to achieve the specified resistance and peak tunneling current, followed by the GaAs/GaAs, and AlGaAs/AlGaAs TJ designs. The AlGaAs/InGaP TJ design can only achieve resistances >5x10{sup -4} {omega}cm{sup 2}.

  12. Performance Comparison of Top and Bottom Contact Gallium Arsenide (GaAs) Solar Cell

    DTIC Science & Technology

    2014-09-01

    Performance Comparison of Top and Bottom Contact Gallium Arsenide (GaAs) Solar Cell by Naresh C Das ARL-TR-7054 September 2014...September 2014 Performance Comparison of Top and Bottom Contact Gallium Arsenide (GaAs) Solar Cell Naresh C Das Sensors and Electron...From - To) 01/02/2014–07/15/2014 4. TITLE AND SUBTITLE Performance Comparison of Top and Bottom Contact Gallium Arsenide (GaAs) Solar Cell 5a

  13. Ternary semitransparent organic solar cells with a laminated top electrode

    PubMed Central

    Makha, Mohammed; Testa, Paolo; Anantharaman, Surendra Babu; Heier, Jakob; Jenatsch, Sandra; Leclaire, Nicolas; Tisserant, Jean-Nicolas; Véron, Anna C.; Wang, Lei; Nüesch, Frank; Hany, Roland

    2017-01-01

    Abstract Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film. PMID:28179960

  14. Ternary semitransparent organic solar cells with a laminated top electrode.

    PubMed

    Makha, Mohammed; Testa, Paolo; Anantharaman, Surendra Babu; Heier, Jakob; Jenatsch, Sandra; Leclaire, Nicolas; Tisserant, Jean-Nicolas; Véron, Anna C; Wang, Lei; Nüesch, Frank; Hany, Roland

    2017-01-01

    Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film.

  15. Growth and photoluminescence characteristics of AlGaAs nanowires

    NASA Astrophysics Data System (ADS)

    Wu, Z. H.; Sun, M.; Mei, X. Y.; Ruda, H. E.

    2004-07-01

    Growth of high-quality single-crystal AlGaAs nanowires was demonstrated using the vapor-liquid-solid (VLS) mechanism with molecular-beam epitaxy (MBE). Highly ordered AlGaAs nanowire arrays and GaAs /AlGaAs multilayer nanowires were also prepared. Photoluminescence (PL) from homogeneous AlGaAs and GaAs /AlGaAs multilayer nanowires was measured. The Al composition of the AlGaAs nanowires was found to be significantly lower than that for planar MBE films grown under the same conditions, as determined from PL and energy-dispersive x-ray spectroscopy measurements. This is explained in terms of the different growth mechanisms for VLS and normal MBE. Such AlGaAs nanowires are expected to have a wide range of applications in electronic and photonic devices.

  16. Theoretical Study of the Effect of an AlGaAs Double Heterostructure on Metal-Semiconductor-Metal Photodetector Performance

    NASA Technical Reports Server (NTRS)

    Salem, Ali F.; Smith, Arlynn W.; Brennan, Kevin F.

    1994-01-01

    The impulse and square-wave input response of different GaAs metal-semiconductor-metal photodetector (MSM) designs are theoretically examined using a two dimensional drift- diffusion numerical calculation with a thermionic-field emission boundary condition model for the heterojunctions. The rise time and the fall time of the output signal current are calculated for a simple GaAs, epitaxially grown, MSM device as well as for various double-heterostructure barrier devices. The double heterostructure devices consist of an AlGaAs layer sandwiched between the top GaAs active, absorption layer and the bottom GaAs substrate. The effect of the depth of the AlGaAs layer on the speed and responsivity of the MSM devices is examined. It is found that there is an optimal depth, at fixed applied bias, of the AlGaAs layer within the structure that provides maximum responsivity at minimal compromise in speed.

  17. Perovskite solar cells: On top of commercial photovoltaics

    NASA Astrophysics Data System (ADS)

    Albrecht, Steve; Rech, Bernd

    2017-01-01

    The efficiency of single-junction solar cells is intrinsically limited and high efficiency multi-junctions are not cost effective yet. Now, semi-transparent perovskite solar cells suggest that low cost multi-junctions could be within reach.

  18. III-V compound semiconductor multi-junction solar cells fabricated by room-temperature wafer-bonding technique

    NASA Astrophysics Data System (ADS)

    Arimochi, Masayuki; Watanabe, Tomomasa; Yoshida, Hiroshi; Tange, Takashi; Nomachi, Ichiro; Ikeda, Masao; Dai, Pan; He, Wei; Ji, Lian; Lu, Shulong; Yang, Hui; Uchida, Shiro

    2015-05-01

    We have developed III-V compound semiconductor multi-junction solar cells by a room-temperature wafer-bonding technique to avoid the formation of dislocations and voids due to lattice mismatch and thermal damage during a conventional high-temperature wafer-bonding process. First, we separately grew an (Al)GaAs top cell on a GaAs substrate and an InGaAs bottom cell on an InP substrate by metal solid source molecular beam epitaxy. Thereafter, we successfully bonded these sub-cells by the room-temperature wafer-bonding technique and fabricated (Al)GaAs ∥ InGaAs wafer-bonded solar cells. To the best of our knowledge, the obtained GaAs ∥ InGaAs and AlGaAs ∥ InGaAs wafer-bonded solar cells exhibited the lowest electrical and optical losses ever reported. The AlGaAs ∥ InGaAs solar cells reached the maximum efficiency of 27.7% at 120 suns. These results suggest that the room-temperature wafer-bonding technique has high potential for achieving higher conversion efficiencies.

  19. Building America Top Innovations 2012: High-Performance with Solar Electric Reduced Peak Demand

    SciTech Connect

    none,

    2013-01-01

    This Building America Top Innovations profile describes Building America solar home research that has demonstrated the ability to reduce peak demand by 75%. Numerous field studies have monitored power production and system effectiveness.

  20. Top-side ionosphere response to extreme solar events

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Yeh, H.-C.; Chao, J.-K.; Veselovsky, I. S.; Su, S.-Y.; Fu, C. C.

    2006-07-01

    Strong X-flares and solar energetic particle (SEP) fluxes are considered as sources of topside ionospheric disturbances observed by the ROCSAT-1/IPEI instrument during the Bastille Day event on 14 July 2000 and the Halloween event on 28 October-4 November 2003. It was found that within a prestorm period in the dayside ionosphere at altitudes of ~600 km the ion density increased up to ~80% in response to flare-associated enhancements of the solar X-ray emission. Ionospheric response to the SEP events was revealed both at sunlit and nightside hemispheres, where the ion density increased up to ~40% and 100%, respectively. We did not find any prominent response of the ion temperature to the X-ray and SEP enhancements. The largest X-ray and SEP impacts were found for the X17 solar flare on 28 October 2003, which was characterized by the most intense fluxes of solar EUV (Tsurutani et al., 2005) and relativistic solar particles (Veselovsky et al., 2004). Solar events on 14 July 2000 and 29 October 2003 demonstrate weaker impacts with respect to their X-ray and SEP intensities. The weakest ionospheric response is observed for the limb X28 solar flare on 4 November 2003. The topside ionosphere response to the extreme solar events is interpreted in terms of the short-duration impact of the solar electromagnetic radiation and the long-lasting impact of the SEP.

  1. Building America Top Innovations 2012: Community Scale High Performance with Solar - Pulte Homes

    SciTech Connect

    none,

    2013-01-01

    This Building America Top Innovations profile describes Pulte Homes of Tucson’s work with Building America to apply a suite of energy-efficiency measures integrated with passive solar design and solar water heating that reduced energy use more than 50% for a community of more than 1,000 homes.

  2. Solar water disinfection (SODIS): a review from bench-top to roof-top.

    PubMed

    McGuigan, Kevin G; Conroy, Ronán M; Mosler, Hans-Joachim; du Preez, Martella; Ubomba-Jaswa, Eunice; Fernandez-Ibañez, Pilar

    2012-10-15

    Solar water disinfection (SODIS) has been known for more than 30 years. The technique consists of placing water into transparent plastic or glass containers (normally 2L PET beverage bottles) which are then exposed to the sun. Exposure times vary from 6 to depending on the intensity of sunlight and sensitivity of the pathogens. Its germicidal effect is based on the combined effect of thermal heating of solar light and UV radiation. It has been repeatedly shown to be effective for eliminating microbial pathogens and reduce diarrhoeal morbidity including cholera. Since 1980 much research has been carried out to investigate the mechanisms of solar radiation induced cell death in water and possible enhancement technologies to make it faster and safer. Since SODIS is simple to use and inexpensive, the method has spread throughout the developing world and is in daily use in more than 50 countries in Asia, Latin America, and Africa. More than 5 million people disinfect their drinking water with the solar disinfection (SODIS) technique. This review attempts to revise all relevant knowledge about solar disinfection from microbiological issues, laboratory research, solar testing, up to and including real application studies, limitations, factors influencing adoption of the technique and health impact.

  3. Evaluation of AlsubxGasub1-xsubAs solar cells

    NASA Technical Reports Server (NTRS)

    Loo, R. Y.; Kamath, G. S.; Knechtli, R. C.; Narayanan, A.; Li, S. S.

    1985-01-01

    Single junction GaAs solar cells have already attained an efficiency of 19% AMO which could potentially be increased to approx 20%, with some optimization. To achieve the higher efficiency the concept of multibandgap solar cells which utilizes a wider region of the solar spectrum should be sed. One of the materials for fabricating the top cell in a multibandgap solar cell is AlGaAs because it is compatible with GaAs in bandgap and lattice match. This is a very important consideration from the materials technology point of view, and the viability of this approach is evaluated.

  4. Screen printed silver top electrode for efficient inverted organic solar cells

    SciTech Connect

    Kim, Junwoo; Duraisamy, Navaneethan; Lee, Taik-Min; Kim, Inyoung; Choi, Kyung-Hyun

    2015-10-15

    Highlights: • Screen printing of silver pattern. • X-ray diffraction pattern confirmed the face centered cubic structure of silver. • Uniform surface morphology of silver pattern with sheet resistance of 0.06 Ω/sq. • The power conversion efficiency of fabricated solar cell is found to be 2.58%. - Abstract: The present work is mainly focused on replacement of the vacuum process for top electrode fabrication in organic solar cells. Silver top electrode deposited through solution based screen printing on pre-deposited polymeric thin film. The solution based printing technology provides uniform top electrode without damaging the underlying organic layers. The surface crystallinity and surface morphology of silver top electrode are examined through X-ray diffraction, field-emission scanning electron microscope and atomic force microscope. The purity of silver is examined through X-ray energy dispersive spectroscopy. The top electrode exhibits face centered cubic structure with homogeneous morphology. The sheet resistance of top electrode is found to be 0.06 Ω/sq and an average pattern thickness of ∼15 μm. The power conversion efficiency is 2.58%. Our work demonstrates that the solution based screen printing is a significant role in the replacement of vacuum process for the fabrication of top electrode in organic solar cells.

  5. An optimized top contact design for solar cell concentrators

    NASA Technical Reports Server (NTRS)

    Desalvo, Gregory C.; Barnett, Allen M.

    1985-01-01

    A new grid optimization scheme is developed for point focus solar cell concentrators which employs a separated grid and busbar concept. Ideally, grid lines act as the primary current collectors and receive all of the current from the semiconductor region. Busbars are the secondary collectors which pick up current from the grids and carry it out of the active region of the solar cell. This separation of functions leads to a multithickness metallization design, where the busbars are made larger in cross section than the grids. This enables the busbars to carry more current per unit area of shading, which is advantageous under high solar concentration where large current densities are generated. Optimized grid patterns using this multilayer concept can provide a 1.6 to 20 percent increase in output power efficiency over optimized single thickness grids.

  6. Preliminary results of fluid dynamic model calculation of convective motion induced by solar heating at the Venus cloud top level.

    NASA Astrophysics Data System (ADS)

    Lee, Yeon Joo; Imamura, Takeshi; Maejima, Yasumitsu; Sugiyama, Ko-ichiro

    The thick cloud layer of Venus reflects solar radiation effectively, resulting in a Bond albedo of 76% (Moroz et al., 1985). Most of the incoming solar flux is absorbed in the upper cloud layer at 60-70 km altitude. An unknown UV absorber is a major sink of the solar energy at the cloud top level. It produces about 40-60% of the total solar heating near the cloud tops, depending on its vertical structure (Crisp et al., 1986; Lee et al., in preparation). UV images of Venus show a clear difference in morphology between laminar flow shaped clouds on the morning side and convective-like cells on the afternoon side of the planet in the equatorial region (Titov et al., 2012). This difference is probably related to strong solar heating at the cloud tops at the sub-solar point, rather than the influence from deeper level convection in the low and middle cloud layers (Imamura et al., 2014). Also, small difference in cloud top structures may trigger horizontal convection at this altitude, because various cloud top structures can significantly alter the solar heating and thermal cooling rates at the cloud tops (Lee et al., in preparation). Performing radiative forcing calculations for various cloud top structures using a radiative transfer model (SHDOM), we investigate the effect of solar heating at the cloud tops on atmospheric dynamics. We use CReSS (Cloud Resolving Storm Simulator), and consider the altitude range from 35 km to 90 km, covering a full cloud deck.

  7. A Statistical Analysis of Loop-Top Motion in Solar Limb Flares

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.; Sui, Linhui; Brosius, D. G.; Dennis, Brian R.

    2005-01-01

    Previous studies of hot, thermal solar flare loops imaged with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) have identified several flares for which the loop top shrinks downward early in the impulsive phase and then expands upward later in the impulsive phase (Sui & Holman 2003; Sui, Holman & Dennis 2004; Veronig et al. 2005). This early downward motion is not predicted by flare models. We study a statistical sample of RHESSI flares to assess how common this evolution is and to better characterize it. In a sample of 88 flares near the solar lin$ that show identifiable loop structure in RHESSI images, 66% (58 flares) showed downward loop-top motion followed by upward motion. We therefore conclude that the early downward motion is a frequent characteristic of flare loops. We obtain the distribution of the timing of the change from downward to upward motion relative to flare start and peak times. We also obtain the distributions of downward and upward speeds.

  8. GaAsP on GaP top solar cells

    NASA Technical Reports Server (NTRS)

    Mcneely, J. B.; Negley, G. H.; Barnett, A. M.

    1985-01-01

    GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.

  9. Plasma dynamics above solar flare soft x-ray loop tops

    SciTech Connect

    Doschek, G. A.; Warren, H. P.; McKenzie, D. E.

    2014-06-10

    We measure non-thermal motions in flare loop tops and above the loop tops using profiles of highly ionized spectral lines of Fe XXIV and Fe XXIII formed at multimillion-degree temperatures. Non-thermal motions that may be due to turbulence or multiple flow regions along the line of sight are extracted from the line profiles. The non-thermal motions are measured for four flares seen at or close to the solar limb. The profile data are obtained using the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. The multimillion-degree non-thermal motions are between 20 and 60 km s{sup –1} and appear to increase with height above the loop tops. Motions determined from coronal lines (i.e., lines formed at about 1.5 MK) tend to be smaller. The multimillion-degree temperatures in the loop tops and above range from about 11 MK to 15 MK and also tend to increase with height above the bright X-ray-emitting loop tops. The non-thermal motions measured along the line of sight, as well as their apparent increase with height, are supported by Solar Dynamics Observatory Atmospheric Imaging Assembly measurements of turbulent velocities in the plane of the sky.

  10. Low temperature processed planar heterojunction perovskite solar cells employing silver nanowires as top electrode

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhua; Li, Fushan; Yang, Kaiyu; Veeramalai, Chandrasekar Perumal; Guo, Tailiang

    2016-04-01

    In this paper, we reported a low temperature processed planar heterojunction perovskite solar cell employing silver nanowires as the top electrode and ZnO nanoparticles as the electron transport layer. The CH3NH3PbI3 perovskite was grown as the light absorber via two-step spin-coating technique. The as-fabricated perovskite solar cell exhibited the highest power conversion efficiency of 9.21% with short circuit current density of 19.75 mA cm-2, open circuit voltage of 1.02, and fill factor value of 0.457. The solar cell's performance showed negligible difference between the forward and reverse bias scan. This work paves a way for realizing low cost solution processable solar cells.

  11. Seasonal north-south asymmetry in solar radiation at the top of Jupiter's atmosphere

    NASA Technical Reports Server (NTRS)

    Beebe, R.; Suggs, R.

    1986-01-01

    A selected set of planetocentric latitudes is used in calculations of the seasonal solar radiation pattern incident on top of the Jovian atmosphere, thereby demonstrating the combined effect of solar distance and declination. Attention is given to hemispheric asymmetries in the Jovian atmosphere's average zonal winds and cloud system morphologies. Marked hemispheric asymmetries are noted in the cloud morphology and in the magnitude and latitudinal position of eastward and westward maxima in the average zonal winds, suggesting seasonal forcing on the order of magnitude presently considered. Supporting observations by Voyagers 1 and 2 are cited.

  12. Aluminum oxide-n-Si field effect inversion layer solar cells with organic top contact

    NASA Astrophysics Data System (ADS)

    Erickson, A. S.; Kedem, N. K.; Haj-Yahia, A. E.; Cahen, D.

    2012-12-01

    We demonstrate a solar cell that uses fixed negative charges formed at the interface of n-Si with Al2O3 to generate strong inversion at the surface of n-Si by electrostatic repulsion. Built-in voltages of up to 755 mV are found at this interface. In order to harness this large built-in voltage, we present a photovoltaic device where the photocurrent generated in this inversion layer is extracted via an inversion layer induced by a high work function transparent organic top contact, deposited on top of a passivating and dipole-inducing molecular monolayer. Results of the effect of the molecular monolayer on device performance yield open-circuit voltages of up to 550 mV for moderately doped Si, demonstrating the effectiveness of this contact structure in removing the Fermi level pinning that has hindered past efforts in developing this type of solar cell with n-type Si.

  13. Table-top solar flares produced with laser driven magnetic reconnections

    NASA Astrophysics Data System (ADS)

    Zhong, J. Y.; Li, Y. T.; Wang, X. G.; Wang, J. Q.; Dong, Q. L.; Liu, X.; Lin, X. X.; Yuan, D. W.; Du, F.; Wang, S. J.; Zhang, L.; An, L.; Xiao, C. J.; Wei, H. G.; Zhang, K.; Wang, F. L.; Jiang, S. E.; Ding, Y. K.; Cao, Z. R.; Yuan, Z.; Zhang, H. Y.; Yang, Z. W.; Zhu, J. Q.; He, X. T.; Cai, H. B.; Zhao, G.; Zhang, J.

    2013-11-01

    The American Nuclear Society (ANS) has presented the prestigious Edward Teller award to Dr. Bruce A. Remington during the 2011 IFSA conference due to his "pioneering scientific work in the fields of inertial confinement fusion (ICF), and especially developing an international effort in high energy density laboratory astrophysics" [1,2]. This is a great acknowledgement to the subject of high energy density laboratory astrophysics. In this context, we report here one experiment conducted to model solar flares in the laboratory with intense lasers [3]. The mega-gauss -scale magnetic fields produced by laser produced plasmas can be used to make magnetic reconnection topology. We have produced one table-top solar flare in our laboratory experiment with the same geometric setup as associated with solar flares.

  14. Solar Energetic Particle Spectrum on 13 December 2006 Determined by IceTop

    SciTech Connect

    IceCube Collaboration; Klein, Spencer

    2008-10-11

    The IceTop air shower array now under construction at the South Pole as the surface component of the IceCube neutrino telescope (Achterberg et al. 2006) detected an unusual near-solar-minimum Ground Level Enhancement (GLE) after a solar flare on 13 December 2006. Beginning at 0220 UT, the 4B class flare occurred at solar coordinates S06 W24, accompanied by strong (X3.4) X-ray emission and type II and IV radio bursts. The LASCO coronagraph on the SOHO spacecraft observed a halo CME launch from the Sun at {approx} 0225 UT with speed estimated to be {approx} 1770 km/s. We have begun (Bieber et al. 2007) a comprehensive analysis of the propagation of solar energetic particles in this event. However the focus of this Letter is the new and unique ability of IceTop to derive the energy spectrum of these particles in the multi-GeV regime from a single detector with a well defined viewing direction. When completed, IceTop will have approximately 500 square meters of ice Cherenkov collecting area arranged in an array of 80 stations on a 125 m triangular grid to detect air showers from one PeV to one EeV. Each station consists of two, two meter diameter tanks filled with ice to a depth of 90 cm. Tanks are instrumented with two Digital Optical Modules (DOM) operated at different gain settings to provide appropriate dynamic range to cover both large and small air showers. Each DOM contains a 10 inch photomultiplier and an advanced readout system capable of digitizing the full waveform. For historical reasons, the two discriminator counting rates recorded in each DOM are termed SPE (Single Photo Electron), and MPE (Multi Photo Electron). In the present analysis the SPE threshold corresponds approximately to 20 photoelectrons (PE), and the MPE threshold to 100 PE. Due to the high altitude (2835m) and the nearly zero geomagnetic cutoff at the South Pole, secondary particle spectra at the detector retain a significant amount of information on the spectra of the primary particles

  15. Efficient Colorful Perovskite Solar Cells Using a Top Polymer Electrode Simultaneously as Spectrally Selective Antireflection Coating.

    PubMed

    Jiang, Youyu; Luo, Bangwu; Jiang, Fangyuan; Jiang, Fuben; Fuentes-Hernandez, Canek; Liu, Tiefeng; Mao, Lin; Xiong, Sixing; Li, Zaifang; Wang, Tao; Kippelen, Bernard; Zhou, Yinhua

    2016-12-14

    Organometal halide perovskites have shown excellent optoelectronic properties and have been used to demonstrate a variety of semiconductor devices. Colorful solar cells are desirable for photovoltaic integration in buildings and other aesthetically appealing applications. However, the realization of colorful perovskite solar cells is challenging because of their broad and large absorption coefficient that commonly leads to cells with dark-brown colors. Herein, for the first time, we report a simple and efficient strategy to achieve colorful perovskite solar cells by using the transparent conducting polymer (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS) as a top electrode and simultaneously as an spectrally selective antireflection coating. Vivid colors across the visible spectrum are attained by engineering optical interference effects among the transparent PEDOT:PSS polymer electrode, the hole-transporting layer and the perovskite layer. The colored perovskite solar cells display power conversion efficiency values from 12.8 to 15.1% (from red to blue) when illuminated from the FTO glass side and from 11.6 to 13.8% (from red to blue) when illuminated from the PEDOT:PSS side. The new approach provides an advanced solution for fabricating colorful perovskite solar cells with easy processing and high efficiency.

  16. Unresolved Fine-scale Structure in Solar Coronal Loop-tops

    NASA Astrophysics Data System (ADS)

    Scullion, E.; Rouppe van der Voort, L.; Wedemeyer, S.; Antolin, P.

    2014-12-01

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop substructures, through taking advantage of the resolving power of the Swedish 1 m Solar Telescope/CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory/Atmospheric Image Assembly (AIA). High-resolution imaging of the chromospheric Hα 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in Hα) known as a coronal rain, to investigate their fine-scale structure. We identify, through analysis of three data sets, large-scale catastrophic cooling in coronal loop-tops and the existence of multi-thermal, multi-stranded substructures. Many cool strands even extend fully intact from loop-top to footpoint. We discover that coronal loop fine-scale strands can appear bunched with as many as eight parallel strands within an AIA coronal loop cross-section. The strand number density versus cross-sectional width distribution, as detected by CRISP within AIA-defined coronal loops, most likely peaks at well below 100 km, and currently, 69% of the substructure strands are statistically unresolved in AIA coronal loops.

  17. Unresolved fine-scale structure in solar coronal loop-tops

    SciTech Connect

    Scullion, E.; Van der Voort, L. Rouppe; Wedemeyer, S.; Antolin, P.

    2014-12-10

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop substructures, through taking advantage of the resolving power of the Swedish 1 m Solar Telescope/CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory/Atmospheric Image Assembly (AIA). High-resolution imaging of the chromospheric Hα 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in Hα) known as a coronal rain, to investigate their fine-scale structure. We identify, through analysis of three data sets, large-scale catastrophic cooling in coronal loop-tops and the existence of multi-thermal, multi-stranded substructures. Many cool strands even extend fully intact from loop-top to footpoint. We discover that coronal loop fine-scale strands can appear bunched with as many as eight parallel strands within an AIA coronal loop cross-section. The strand number density versus cross-sectional width distribution, as detected by CRISP within AIA-defined coronal loops, most likely peaks at well below 100 km, and currently, 69% of the substructure strands are statistically unresolved in AIA coronal loops.

  18. A Statistical Analysis of Loop-Top Motion in Solar Limb Flares

    NASA Astrophysics Data System (ADS)

    Holman, G. D.; Sui, L.; Brosius, D. G.; Dennis, B. R.

    2005-12-01

    Previous studies of hot, thermal solar flare loops imaged with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) have identified several flares for which the loop top shrinks downward early in the impulsive phase and then expands upward later in the impulsive phase (Sui & Holman 2003; Sui, Holman & Dennis 2004; Veronig et al. 2005). This early downward motion is not predicted by flare models. We study a statistical sample of RHESSI flares to assess how common this evolution is and to better characterize it. In a sample of 88 flares near the solar limb that show identifiable loop structure in RHESSI images, 66% (58 flares) showed downward loop-top motion followed by upward motion. We therefore conclude that the early downward motion is a frequent characteristic of flare loops. We obtain the distribution of the timing of the change from downward to upward motion relative to flare start and peak times. We also obtain the distributions of downward and upward speeds. This work was supported in part by NASA SEC Guest Investigator Grant 370-16-20-16 and by the RHESSI project.

  19. Silver Nanowire Top Electrodes in Flexible Perovskite Solar Cells using Titanium Metal as Substrate.

    PubMed

    Lee, Minoh; Ko, Yohan; Min, Byoung Koun; Jun, Yongseok

    2016-01-08

    Flexible perovskite solar cells (FPSCs) have various applications such as wearable electronic textiles and portable devices. In this work, we demonstrate FPSCs on a titanium metal substrate employing solution-processed silver nanowires (Ag NWs) as the top electrode. The Ag NW electrodes were deposited on top of the spiro-MeOTAD hole transport layer by a carefully controlled spray-coating method at moderate temperatures. The power conversion efficiency (PCE) reached 7.45 % under AM 1.5 100 mW cm(-2) illumination. Moreover, the efficiency for titanium-based FPSCs decreased only slightly (by 2.6 % of the initial value) after the devices were bent 100 times. With this and other advances, fully solution-based indium-free flexible photovoltaics, advantageous in terms of price and processing, have the potential to be scaled into commercial production.

  20. Semitransparent organic solar cells with hybrid monolayer graphene/metal grid as top electrodes

    NASA Astrophysics Data System (ADS)

    Lin, Peng; Choy, Wallace C. H.; Zhang, Di; Xie, Fengxian; Xin, Jianzhuo; Leung, C. W.

    2013-03-01

    Hybrid transparent monolayer graphene/metal grid is proposed as top electrode of semitransparent organic solar cells. The hybrid electrode using gold grid on flexible polyethylene terephthalate substrate shows very low sheet resistance of 22 ± 3 Ω/□ and high optical transmittance of 81.4%, which is comparable to conventional indium tin oxide/glass electrode. Using lamination process, the layer of poly(3,4-ethylenedioythiophene):poly(styrenesulfonate) doped with D-sorbitol plays an important role in the electrical performance of the laminated devices. In addition, the devices show best power convention efficiency of 3.1% and fill factor of 55.0%, which are much better than those of similar graphene-based semitransparent organic solar cells.

  1. A transparent, solvent-free laminated top electrode for perovskite solar cells

    PubMed Central

    Makha, Mohammed; Fernandes, Silvia Letícia; Jenatsch, Sandra; Offermans, Ton; Schleuniger, Jürg; Tisserant, Jean-Nicolas; Véron, Anna C.; Hany, Roland

    2016-01-01

    Abstract A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of ~30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes. PMID:27877878

  2. Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

    SciTech Connect

    Yan, Wensheng Gu, Min; Tao, Zhikuo; Ong, Thiam Min Brian

    2015-03-02

    The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The J{sub sc} values are 12.1, 13.0, and 14.3 mA/cm{sup 2} and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer.

  3. A transparent, solvent-free laminated top electrode for perovskite solar cells.

    PubMed

    Makha, Mohammed; Fernandes, Silvia Letícia; Jenatsch, Sandra; Offermans, Ton; Schleuniger, Jürg; Tisserant, Jean-Nicolas; Véron, Anna C; Hany, Roland

    2016-01-01

    A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of ~30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes.

  4. Top laminated graphene electrode in a semitransparent polymer solar cell by simultaneous thermal annealing/releasing method.

    PubMed

    Lee, Yu-Ying; Tu, Kun-Hua; Yu, Chen-Chieh; Li, Shao-Sian; Hwang, Jeong-Yuan; Lin, Chih-Cheng; Chen, Kuei-Hsien; Chen, Li-Chyong; Chen, Hsuen-Li; Chen, Chun-Wei

    2011-08-23

    In this article, we demonstrate a semitransparent inverted-type polymer solar cell using a top laminated graphene electrode without damaging the underlying organic photoactive layer. The lamination process involves the simultaneous thermal releasing deposition of the graphene top electrode during thermal annealing of the photoactive layer. The resulting semitransparent polymer solar cell exhibits a promising power conversion efficiency of approximately 76% of that of the standard opaque device using an Ag metal electrode. The asymmetric photovoltaic performances of the semitransparent solar cell while illuminated from two respective sides were further analyzed using optical simulation and photocarrier recombination measurement. The devices consisting of the top laminated transparent graphene electrode enable the feasible roll-to-roll manufacturing of low-cost semitransparent polymer solar cells and can be utilized in new applications such as power-generated windows or multijunction or bifacial photovoltaic devices.

  5. GaAsP Top Solar Cells for Increased Solar Conversion Efficiency

    DTIC Science & Technology

    1989-01-01

    samples were prepared by an aqua regia etch of both faces: some texturing of the Ga > face was observed in all samples. Reflec- tion and transmission...Space Power 19. ABSTRACT 𔃻opnjnue on reverse if nedeuuary and identify by block numbert The development of multijunction solar cells is the key to...approaches have demonstrated good device y~oete. No other approach has made acceptable devic 7.s.etis (See Reverse ) 2o 3i,.;IIIuI0N/AVAILAI3ILi r 7 7 j, ;TstAt

  6. Optimization of a polymer top electrode for inverted semitransparent organic solar cells

    SciTech Connect

    Zhou, Yinhua; Cheun, Hyeunseok; Choi, Seungkeun; Fuentes-Hernandez, Canek; Kippelen, Bernard

    2011-05-01

    We report on semitransparent organic solar cells using a single-layer blend based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the top electrode. The PEDOT:PSS blend was prepared by mixing a high-conductivity formulation of PEDOT:PSS (H.C. Starck CLEVIOS PH-1000) and another formulation of PEDOT:PSS (H.C. Starck CLEVIOS CPP 105D). The PEDOT:PSS blend yields good wetting properties on the hydrophobic surface of a blend of poly(3-hexylthiophene) (P3HT) with phenyl-C61-butyric acid methyl ester (PC60 BM), and shows a conductivity over 400 S cm-1. Semitransparent organic solar cells using the PEDOT:PSS blend as the top electrode with a structure of glass/ITO/ZnO/P3HT:PC60BM/PEDOT:PSS-blend exhibited an average power conversion efficiency of 2.4% estimated for 100 mW cm-2 AM 1.5G illumination.

  7. Multilayer Transparent Top Electrode for Solution Processed Perovskite/Cu(In,Ga)(Se,S)2 Four Terminal Tandem Solar Cells.

    PubMed

    Yang, Yang Michael; Chen, Qi; Hsieh, Yao-Tsung; Song, Tze-Bin; Marco, Nicholas De; Zhou, Huanping; Yang, Yang

    2015-07-28

    Halide perovskites (PVSK) have attracted much attention in recent years due to their high potential as a next generation solar cell material. To further improve perovskites progress toward a state-of-the-art technology, it is desirable to create a tandem structure in which perovskite may be stacked with a current prevailing solar cell such as silicon (Si) or Cu(In,Ga)(Se,S)2 (CIGS). The transparent top electrode is one of the key components as well as challenges to realize such tandem structure. Herein, we develop a multilayer transparent top electrode for perovskite photovoltaic devices delivering an 11.5% efficiency in top illumination mode. The transparent electrode is based on a dielectric/metal/dielectric structure, featuring an ultrathin gold seeded silver layer. A four terminal tandem solar cell employing solution processed CIGS and perovskite cells is also demonstrated with over 15% efficiency.

  8. High-performance semitransparent perovskite solar cells with solution-processed silver nanowires as top electrodes.

    PubMed

    Guo, Fei; Azimi, Hamed; Hou, Yi; Przybilla, Thomas; Hu, Mengyao; Bronnbauer, Carina; Langner, Stefan; Spiecker, Erdmann; Forberich, Karen; Brabec, Christoph J

    2015-02-07

    In this work, we report efficient semitransparent perovskite solar cells using solution-processed silver nanowires (AgNWs) as top electrodes. A thin layer of zinc oxide nanoparticles is introduced beneath the AgNWs, which fulfills two essential functionalities: it ensures ohmic contact between the PC60BM and the AgNWs and it serves as a physical foundation that enables the solution-deposition of AgNWs without causing damage to the underlying perovskite. The as-fabricated semitransparent perovskite cells show a high fill factor of 66.8%, Voc = 0.964 V, Jsc = 13.18 mA cm(-2), yielding an overall efficiency of 8.49% which corresponds to 80% of the reference devices with reflective opaque electrodes.

  9. Working from Both Sides: Composite Metallic Semitransparent Top Electrode for High Performance Perovskite Solar Cells.

    PubMed

    Dai, Xuezeng; Zhang, Ye; Shen, Heping; Luo, Qiang; Zhao, Xingyue; Li, Jianbao; Lin, Hong

    2016-02-01

    We report herein perovskite solar cells using solution-processed silver nanowires (AgNWs) as transparent top electrode with markedly enhanced device performance, as well as stability by evaporating an ultrathin transparent Au (UTA) layer beneath the spin-coated AgNWs forming a composite transparent metallic electrode. The interlayer serves as a physical separation sandwiched in between the perovskite/hole transporting material (HTM) active layer and the halide-reactive AgNWs top-electrode to prevent undesired electrode degradation and simultaneously functions to significantly promote ohmic contact. The as-fabricated semitransparent PSCs feature a Voc of 0.96 V, a Jsc of 20.47 mA cm(-2), with an overall PCE of over 11% when measured with front illumination and a Voc of 0.92 V, a Jsc of 14.29 mA cm(-2), and an overall PCE of 7.53% with back illumination, corresponding to approximately 70% of the value under normal illumination conditions. The devices also demonstrate exceptional fabrication repeatability and air stability.

  10. Growth and characterization of GaAs, AlGaAs and their heterostructures by organometallic vapor phase epitaxy

    SciTech Connect

    Shealy, J.R.

    1983-01-01

    Organometallic Vapor Phase Epitaxy (OMVPE) is a cold wall vapor desposition technique using organometallic and/or hydride sources for the fabrication of a variety of epitaxial compound semiconductor alloys on suitable substrates. The use of the OMVPE process to produce high quality GaAs, AlGaAs, and their heterostructures on GaAs substrates using trimethygalium (TMG), trimethylalumium (TMA), and arsine is described. For GaAs epitaxial films, the unintentional residual donor sand acceptors have been identified using far-infrared photo-ionization data, and low temperature photoluminescence, respectively, and their concentrations have been evaluated using Hall data. For the growth of AlGaAs films, it was observed that poor quality films were obtained due to oxygen contamination of the layer during growth. A series of graded bandgap heterostructures and abrupt quantum well heterostructures were grown over a variety of growth conditions. Composition gradings were controlled over a full range of alloy compositions on distances as small as 500 - 1000 A, and a 40 A quantum well heterostructure was obtained at low growth temperatures (550/sup 0/C). Finally, results are presented on a few devices which incorporate metallurgical junctions and heterojunctions with the GaAs/AlGaAs system. These devices include a microwave vertical FET structure, graded bandgap solar cells, and light emitting diodes.

  11. A Challenge Beyond Bottom Cells: Top-Illuminated Flexible Organic Solar Cells with Nanostructured Dielectric/Metal/Polymer (DMP) Films.

    PubMed

    Ham, Juyoung; Dong, Wan Jae; Park, Jae Yong; Yoo, Chul Jong; Lee, Illhwan; Lee, Jong-Lam

    2015-07-15

    Top-illuminated flexible organic solar cells with a high power conversion efficiency (≈6.75%) are fabricated using a dielectric/metal/polymer (DMP) electrode. Employing a polymer layer (n = 1.49) makes it possible to show the high transmittance, which is insensitive to film thickness, and the excellent haze induced by well-ordered nanopatterns on the DMP electrode, leading to a 28% of enhancement in efficiency compared to bottom cells.

  12. AlGaAs diode pumped tunable chromium lasers

    DOEpatents

    Krupke, William F.; Payne, Stephen A.

    1992-01-01

    An all-solid-state laser system is disclosed wherein the laser is pumped in the longwave wing of the pump absorption band. By utilizing a laser material that will accept unusually high dopant concentrations without deleterious effects on the crystal lattice one is able to compensate for the decreased cross section in the wing of the absorption band, and the number of pump sources which can be used with such a material increases correspondingly. In a particular embodiment a chromium doped colquiriite-structure crystal such as Cr:LiSrAlF.sub.6 is the laser material. The invention avoids the problems associated with using AlGaInP diodes by doping the Cr:LiSrAlF.sub.6 heavily to enable efficient pumping in the longwave wing of the absorption band with more practical AlGaAs diodes.

  13. Selective oxidation of buried AlGaAs for fabrication of vertical-cavity lasers

    SciTech Connect

    Choquette, K.D.; Geib, K.M.; Chui, H.C.; Hou, H.Q.; Hull, R.

    1996-06-01

    The authors discuss the selective conversion of buried layers of AlGaAs to a stable oxide and the implementation of this oxide into high performance vertical-cavity surface emitting lasers (VCSELs). The rate of lateral oxidation is shown to be linear with an Arrhenius temperature dependence. The measured activation energies vary with Al composition, providing a high degree of oxidation selectivity between AlGaAs alloys. Thus buried oxide layers can be selectively fabricated within the VCSEL through small compositional variations in the AlGaAs layers. The oxidation of AlGaAs alloys, as opposed to AlAs, is found to provide robust processing of reliable lasers. The insulating and low refractive index oxide provides enhanced electrical and optical confinement for ultralow threshold currents in oxide-apertured VCSELs.

  14. State diagnostics of RTD based on nanoscale multilayered AlGaAs heterostructures

    NASA Astrophysics Data System (ADS)

    Makeev, M. O.; Meshkov, S. A.; Sinyakin, V. Yu

    2016-08-01

    In the present work the problems of technical diagnostics of RTD based on nanoscale multilayered AlGaAs heterostructures are being solved. The technique and the algorithms of RTD functionality region developing are being considered.

  15. The Role of Kelvin-Helmholtz Instability for Producing Loop-top Hard X-Ray Sources in Solar Flares

    NASA Astrophysics Data System (ADS)

    Fang, Xia; Yuan, Ding; Xia, Chun; Van Doorsselaere, Tom; Keppens, Rony

    2016-12-01

    We propose a model for the formation of loop-top hard X-ray (HXR) sources in solar flares through the inverse Compton mechanism, scattering the surrounding soft X-ray (SXR) photons to higher energy HXR photons. We simulate the consequences of a flare-driven energy deposit in the upper chromosphere in the impulsive phase of single loop flares. The consequent chromosphere evaporation flows from both footpoints reach speeds up to hundreds of kilometers per second, and we demonstrate how this triggers Kelvin-Helmholtz instability (KHI) in the loop top, under mildly asymmetric conditions, or more toward the loop flank for strongly asymmetric cases. The KHI vortices further fragment the magnetic topology into multiple magnetic islands and current sheets, and the hot plasma within leads to a bright loop-top SXR source region. We argue that the magnetohydrodynamic turbulence that appears at the loop apex could be an efficient accelerator of non-thermal particles, which the island structures can trap at the loop-top. These accelerated non-thermal particles can upscatter the surrounding thermal SXR photons emitted by the extremely hot evaporated plasma to HXR photons.

  16. TOPS: Toward Other Planetary Systems. A report by the solar system exploration division

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This report describes a general plan and the pertinent technological requirements for TOPS (Toward Other Planetary Systems), a staged program to ascertain the prevalence and character of other planetary systems and to construct a definitive picture of the formation of stars and their planets. The first stages focus on discovering and studying a significant number of fully formed planetary systems, as well as expanding current studies of protoplanetary systems. As the TOPS Program evolves, emphasis will shift toward intensive study of the discovered systems and of individual planets. Early stages of the TOPS Program can be undertaken with ground-based observations and space missions comparable in scale to those now being performed. In the long term, however, TOPS will become an ambitious program that challenges our capabilities and provides impetus for major space initiatives and new technologies.

  17. The influence of top electrode of InGaAsN/GaAs solar cell on their electrical parameters extracted from illuminated I-V characteristics

    NASA Astrophysics Data System (ADS)

    Dawidowski, Wojciech; Ściana, Beata; Zborowska-Lindert, Iwona; Mikolášek, Miroslav; Bielak, Katarzyna; Badura, Mikołaj; Pucicki, Damian; Radziewicz, Damian; Kováč, Jaroslav; Tłaczała, Marek

    2016-06-01

    In the presented work the growth and fabrication process of dilute nitride based solar cells were reported. We fabricated three different solar cells to investigate the influence of top contact on their electrical parameters. Test devices were characterized by the means of current-voltage measurements carried out under the sunlight simulator. The obtained I-V results were scrutinized using a single diode equivalent circuit of a solar cell. We employed the Lambert W approach to find the solvable solution of the modified Shockley equation, in order to determine the basic solar cell electrical parameters such as: ideality factor n, series and shunt resistances (Rs and Rsh), saturation current I0 and photocurrent Iph generated in the solar cell structure. It was found that electrical parameters obtained from the fitting procedure depend on solar cell design. The type of top electrode influences the values of parasitic resistances, open circuit voltage and short circuit current.

  18. Vacuum-free laminated top electrode with conductive tapes for scalable manufacturing of efficient perovskite solar cells

    SciTech Connect

    Shao, Yuchuan; Wang, Qi; Dong, Qingfeng; Yuan, Yongbo; Huang, Jinsong

    2015-06-25

    The efficiency of organometal trihalide perovskites (OTP) solar cells have reached that parity of single crystal silicon, and its nature abundant raw material and solution-process capability promise a bright future for commercialization. However, the vacuum based techniques for metal electrode deposition and additional encapsulation layer increase the cost of the perovskite solar cells dramatically and impede their commercialization process. Here, we report a vacuum-free low temperature lamination technique to fabricate the top electrode by commercial conductive tapes (C-tape). The simple fabrication method yields good quality contact and high efficiency device of 12.7%. The C-tapes also encapsulated the devices effectively, resulting in greatly improved device stability. As a result, the combination of lamination of electrodes and encapsulation layers into a single step significantly reduce the cost of device fabrication.

  19. Vacuum-free laminated top electrode with conductive tapes for scalable manufacturing of efficient perovskite solar cells

    DOE PAGES

    Shao, Yuchuan; Wang, Qi; Dong, Qingfeng; ...

    2015-06-25

    The efficiency of organometal trihalide perovskites (OTP) solar cells have reached that parity of single crystal silicon, and its nature abundant raw material and solution-process capability promise a bright future for commercialization. However, the vacuum based techniques for metal electrode deposition and additional encapsulation layer increase the cost of the perovskite solar cells dramatically and impede their commercialization process. Here, we report a vacuum-free low temperature lamination technique to fabricate the top electrode by commercial conductive tapes (C-tape). The simple fabrication method yields good quality contact and high efficiency device of 12.7%. The C-tapes also encapsulated the devices effectively, resultingmore » in greatly improved device stability. As a result, the combination of lamination of electrodes and encapsulation layers into a single step significantly reduce the cost of device fabrication.« less

  20. Importance of energy and angular resolutions in top-hat electrostatic analysers for solar wind proton measurements

    NASA Astrophysics Data System (ADS)

    De Marco, R.; Marcucci, M. F.; Bruno, R.; D'Amicis, R.; Servidio, S.; Valentini, F.; Lavraud, B.; Louarn, P.; Salatti, M.

    2016-08-01

    We use a numerical code which reproduces the angular/energy response of a typical top-hat electrostatic analyser starting from solar wind proton velocity distribution functions (VDFs) generated by numerical simulations. The simulations are based on the Hybrid Vlasov-Maxwell numerical algorithm which integrates the Vlasov equation for the ion distribution function, while the electrons are treated as a fluid. A virtual satellite launched through the simulation box measures the particle VDFs. Such VDFs are moved from the simulation Cartesian grid to energy-angular coordinates to mimic the response of a real sensor in the solar wind. Different energy-angular resolutions of the analyser are investigated in order to understand the influence of the phase-space resolution in existing and upcoming space missions, with regards to determining the key parameters of plasma dynamics.

  1. Survey of Thermoelectric and Solar Technologies as Alternative Energy Solutions

    DTIC Science & Technology

    2012-02-01

    the AlGaAs layers on the carrier transport properties , the n-i-p structures should be regrown on p-type GaAs substrates rather than beryllium (Be...thermoelectric power generation, enabling full diurnal operation. This report discusses measurements of the properties and efficiency of a...10 Figure 10. I-V characteristics of solar cells with and without an AlGaAs layer (left) a p-i-n

  2. AlGaAs phased array laser for optical communications

    NASA Technical Reports Server (NTRS)

    Carlson, N. W.

    1989-01-01

    Phased locked arrays of multiple AlGaAs diode laser emitters were investigated both in edge emitting and surface emitting configurations. CSP edge emitter structures, coupled by either evanescent waves or Y-guides, could not achieve the required powers (greater than or similar to 500 mW) while maintaining a diffraction limited, single lobed output beam. Indeed, although the diffraction limit was achieved in this type of device, it was at low powers and in the double lobed radiation pattern characteristic of out-of-phase coupling. Grating surface emitting (GSE) arrays were, therefore, investigated with more promising results. The incorporation of second order gratings in distribute Bragg reflector (DBR) structures allows surface emission, and can be configured to allow injection locking and lateral coupling to populate 2-D arrays that should be able to reach power levels commensurate with the needs of high performance, free space optical communications levels. Also, a new amplitude modulation scheme was developed for GSE array operation.

  3. The application of highly doped single-layer graphene as the top electrodes of semitransparent organic solar cells.

    PubMed

    Liu, Zhike; Li, Jinhua; Sun, Zhen-Hua; Tai, Guoan; Lau, Shu-Ping; Yan, Feng

    2012-01-24

    A single-layer graphene film with high conductance and transparency was realized by effective chemical doping. The conductance of single-layer graphene was increased for more than 400% when it was doped with Au nanoparticles and poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid). Then semitransparent organic solar cells based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with single-layer graphene and indium tin oxide (ITO) as the top and bottom electrodes, respectively. The performance of the devices was optimized by tuning the active layer thickness and doping the single-layer graphene electrodes. The maximum efficiency of 2.7% was observed in the devices with the area of 20 mm(2) illuminated from graphene electrode under the AM1.5 solar simulator. It is notable that all of the devices showed higher efficiency from the graphene than ITO side, which was attributed to the better transmittance of the graphene electrodes. In addition, the influence of the active area of the organic solar cell on its photovoltaic performance was studied. We found that, when the active areas increased from 6 to 50 mm(2), the power conversion efficiencies decreased from 3% to 2.3% because of the increased series resistances and the decreased edge effect of the devices.

  4. Selective thermal terahertz emission from GaAs and AlGaAs

    SciTech Connect

    Požela, K. Širmulis, E.; Kašalynas, I.; Šilėnas, A.; Požela, J.; Jucienė, V.

    2014-09-01

    The selective thermally stimulated terahertz (THz) radiation emission from GaAs and AlGaAs alloys are experimentally observed at frequencies of coupled oscillations of free electron plasma and different branches of interface AlGaAs optical phonons. The effect of strong absorption of incident radiation with large oblique angle (26°) by heated GaAs and AlGaAs is revealed. The coherent THz radiation emission with the frequency of 7.6 THz from the heated high conductivity GaAs (n = 4 × 10{sup 18 }cm{sup −3}) layer is observed. The results are highly relevant to application in optoelectronic THz devices.

  5. 18.4%-Efficient Heterojunction Si Solar Cells Using Optimized ITO/Top Electrode.

    PubMed

    Kim, Namwoo; Um, Han-Don; Choi, Inwoo; Kim, Ka-Hyun; Seo, Kwanyong

    2016-05-11

    We optimize the thickness of a transparent conducting oxide (TCO) layer, and apply a microscale mesh-pattern metal electrode for high-efficiency a-Si/c-Si heterojunction solar cells. A solar cell equipped with the proposed microgrid metal electrode demonstrates a high short-circuit current density (JSC) of 40.1 mA/cm(2), and achieves a high efficiency of 18.4% with an open-circuit voltage (VOC) of 618 mV and a fill factor (FF) of 74.1% as result of the shortened carrier path length and the decreased electrode area of the microgrid metal electrode. Furthermore, by optimizing the process sequence for electrode formation, we are able to effectively restore the reduction in VOC that occurs during the microgrid metal electrode formation process. This work is expected to become a fundamental study that can effectively improve current loss in a-Si/c-Si heterojunction solar cells through the optimization of transparent and metal electrodes.

  6. Comparison of degradation and recaesiation between GaAs and AlGaAs photocathodes in an unbaked vacuum system.

    PubMed

    Feng, Cheng; Zhang, Yijun; Shi, Feng; Qian, Yunsheng; Cheng, Hongchang; Zhang, Junju; Liu, Xinxin; Zhang, Xiang

    2017-03-20

    The lifetime and reliability of a photocathode during operation are always raised problems and the photocathode performance depends on the vacuum condition. With the purpose of investigating the stability and reliability of a GaAs-based photocathode in a harsher vacuum environment, reflection-mode exponential-doped GaAs and AlGaAs photocathodes are metalorganic vapor-phase epitaxial grown and then (Cs, O) activated inside an unbaked vacuum chamber. The degraded photocurrents are compared after activation and recaesiations between GaAs and AlGaAs photocathdoes under illumination with an equal initial photocurrent and an equal optical flux, respectively. It is found that the performance on degradation and recaesiations between GaAs and AlGaAs photocathodes are different. In the unbaked vacuum system, the stability of an AlGaAs photocathode after (Cs, O) activation is always better than that of a GaAs photocathode. After multiple recaesiations, the photocurrent decay curves of the AlGaAs photocathode are nearly coincident, which means a nearly constant operational lifetime. Moreover, operational lifetime of an AlGaAs photocathode is longer than that of a GaAs photocathode, which further illuminates that AlGaAs photocathodes are superior to GaAs photocathodes in stability and repeatability under markedly harsher vacuum conditions.

  7. Progress in GaAs/CuInSe2 tandem junction solar cells

    NASA Technical Reports Server (NTRS)

    Kim, N. P.; Burgess, R. M.; Mickelsen, R. A.; Stanbery, B. J.; Mcclelland, R. W.; King, B. D.; Gale, R. P.

    1991-01-01

    Much more power is required for spacecraft of the future than current vehicles. To meet this increased demand for power while simultaneously meeting other requirements for launch, deployment, and maneuverability, the development of higher-efficiency, lighter-weight, and more radiation resistant photovoltaic cells is essential. Mechanically stacked tandem junction solar cells based on (AlGaAs)GaAs thin film CLEFT (Cleavage of Lateral Epitaxial Film for Transfer) top cells and CuInSe2(CIS) thin film bottom cells are being developed to meet these power needs. The mechanically stacked tandem configuration is chosen due to its interconnect flexibility allowing more efficient array level performance. It also eliminates cell fabrication processing constraints associated with monolithically integrated multi-junction approaches, thus producing higher cell fabrication yields. The GaAs cell is used as the top cell due to its demonstrated high efficiency, and good radiation resistance. Furthermore, it offers a future potential for bandgap tuning using AlGaAs as the absorber to maximize cell performance. The CuInSe2 cell is used as the bottom cell due to superb radiation resistance, stability, and optimal bandgap value in combination with an AlGaAs top cell. Since both cells are incorporated as thin films, this approach provides a potential for very high specific power. This high specific power (W/kg), combined with high power density (W/sq m) resulting from the high efficiency of this approach, makes these cells ideally suited for various space applications.

  8. High Resistivity Molecular Beam Epitaxial AlGaAs for Device Applications.

    DTIC Science & Technology

    1980-02-01

    V MESFET technology requires, in part, the improvement of semi-insulating materials used in today’s device fabrication. The properties of currently...overall improvement in low temperature Hall mobility. Several techniques have been used to characterize AlGaAs properties. Basic determinations of impurity...available chromium-doped GaAs substrates impose restrictions on the performance of devices and monolithic circuits presently being produced in research

  9. Analysis of urban land use in the megacity of Dhaka, Bangladesh: Roof-top detection in the context of assessing solar photovoltaic potential

    NASA Astrophysics Data System (ADS)

    Jaegermeyr, J.; Kabir, H.; Endlicher, W.

    2009-12-01

    The megacity of Dhaka, Bangladesh is considered to be one of the world’s fastest growing urban centers. With nearly 14 million people Dhaka currently faces tremendous power crisis. The available power supply of Dhaka Megacity is currently 1000-1200 MW against the maximum demand of nearly 2000 MW. The objective of this study is to classify land cover of Dhaka to locate roof-top areas which are adequate for solar photovoltaic applications. Usually this task is performed with additional building-heights data. With lack of that, we present an object-based classification approach which is based on high resolution Quickbird data only. Extensive formal buildings in Dhaka mostly have flat roof-tops made from concrete which are well suited for PV applications. The classification is focused to detect these ‘Bright Roof-Tops’ to assess a lower limit for potential PV areas. With that conservative approach bright roof-top areas of 10.554 km2 out of the city’s 134.282 km2 could be found. The overall classification accuracy is 0.918, the producer’s accuracy of ‘Bright Roof-Tops’ is 0.833. Preliminary result of the PhD work of Humayun Kabir indicates that the application of only 75 Wp stand-alone solar modules on these available bright roof-tops can generate nearly 1,000 MW of electricity. The application of solar modules with high capacity (i.e., >200 Wp) preferably through grid-connected PV systems can substantially meet-up the city’s power demand, although several techno-economic and socio-political factors are certainly involved.

  10. Results of the Air Force high efficiency cascaded multiple bandgap solar cell programs

    NASA Technical Reports Server (NTRS)

    Rahilly, W. P.

    1980-01-01

    The III-V semiconductor materials system that was selected for continued cascade cell development was the AlGaAs cell on GaAs cell structure. The tunnel junction used as transparent ohmic contact between the top cell and the bottom cell continued to be the central difficulty in achieving the program objective of 25 percent AMO efficiency at 25 C. During the tunnel junction and top cell developments it became apparent that the AlGaAs cell has potential for independent development as a single junction converter and is a logical extension of the present GaAs heteroface technology.

  11. Influence of thin metal as a top electrode on the characteristics of P-I-N a- Si:H solar cells

    SciTech Connect

    Han, M.; Anderson, W.A.; Lahri, R.; Coleman, J.

    1981-04-01

    Hydrogenated amorphous silicon (a-Si:H) p-n junction solar cells have been fabricated which utilize various metals (Cr, Cu, Al, Pd, Ag) as a top electrode. Experimental and theoretical analysis of photovolatic performance in a-Si:H solar cells as a function of resistivity, optical transmittance, and work function of thin metal films are presented. Metal work function changes the effective built-in potential of p-n junction diodes. Furthermore, a lower work function metal forms a good Ohmic contact for substrate --P/sup +/-I-N/sup +/-- electrode cells, and high work function metals improve V/sub oc/ of substrate -N-I-P cells. Typical V/sub o/c values are 760 mV with Cr--, Cu--, and Al--N-I-P--stainless steel (SS), 700 mV with Pd--N-I-P-SS, 600 mV with Pd--P-I-N-SS, and 540 mV with Cr--P-I-N-SS. J/sub sc/ is strongly dependent on transmittance and resistivity of the metal films. Fill factor is independent of the choice of a top electrode. An efficient of 2% has been obtained on a 2 cm/sup 2/ solar cell.

  12. Minimizing optical losses in monolithic perovskite/c-Si tandem solar cells with a flat top cell.

    PubMed

    Santbergen, Rudi; Mishima, Ryota; Meguro, Tomomi; Hino, Masashi; Uzu, Hisashi; Blanker, Johan; Yamamoto, Kenji; Zeman, Miro

    2016-09-05

    In a monolithic perovskite/c-Si tandem device, the perovskite top cell has to be deposited onto a flat c-Si bottom cell without anti-reflective front side texture, to avoid fabrication issues. We use optical simulations to analyze the reflection losses that this induces. We then systematically minimize these losses by introducing surface textures in combination with a so-called burial layer to keep the perovskite top cell flat. Optical simulations show that, even with a flat top cell, the monolithic perovskite/c-Si tandem device can reach a matched photocurrent density as high as 19.57 mA/cm2.

  13. Theoretical performance of multi-junction solar cells combining III-V and Si materials.

    PubMed

    Mathews, Ian; O'Mahony, Donagh; Corbett, Brian; Morrison, Alan P

    2012-09-10

    A route to improving the overall efficiency of multi-junction solar cells employing conventional III-V and Si photovoltaic junctions is presented here. A simulation model was developed to consider the performance of several multi-junction solar cell structures in various multi-terminal configurations. For series connected, 2-terminal triple-junction solar cells, incorporating an AlGaAs top junction, a GaAs middle junction and either a Si or InGaAs bottom junction, it was found that the configuration with a Si bottom junction yielded a marginally higher one sun efficiency of 41.5% versus 41.3% for an InGaAs bottom junction. A significant efficiency gain of 1.8% over the two-terminal device can be achieved by providing an additional terminal to the Si bottom junction in a 3-junction mechanically stacked configuration. It is shown that the optimum performance can be achieved by employing a four-junction series-connected mechanically stacked device incorporating a Si subcell between top AlGaAs/GaAs and bottom In0.53Ga0.47As cells.

  14. High-power AlGaAs channeled substrate planar diode lasers for spaceborne communications

    NASA Technical Reports Server (NTRS)

    Connolly, J. C.; Goldstein, B.; Pultz, G. N.; Slavin, S. E.; Carlin, D. B.; Ettenberg, M.

    1988-01-01

    A high power channeled substrate planar AlGaAs diode laser with an emission wavelength of 8600 to 8800 A was developed. The optoelectronic behavior (power current, single spatial and spectral behavior, far field characteristics, modulation, and astigmatism properties) and results of computer modeling studies on the performance of the laser are discussed. Lifetest data on these devices at high output power levels is also included. In addition, a new type of channeled substrate planar laser utilizing a Bragg grating to stabilize the longitudinal mode was demonstrated. The fabrication procedures and optoelectronic properties of this new diode laser are described.

  15. Photoluminescence of individual doped GaAs /AlGaAs nanofabricated quantum dots

    NASA Astrophysics Data System (ADS)

    Kalliakos, Sokratis; García, César Pascual; Pellegrini, Vittorio; Zamfirescu, Marian; Cavigli, Lucia; Gurioli, Massimo; Vinattieri, Anna; Pinczuk, Aron; Dennis, Brian S.; Pfeiffer, Loren N.; West, Ken W.

    2007-04-01

    Dilute arrays of GaAs /AlGaAs modulation-doped quantum dots with same sizes fabricated by electron beam lithography and low impact reactive ion etching exhibit highly uniform luminescence lines. Single quantum dots display spectral emission with peak energies and linewidths linked largely to the geometrical diameter of the dot and to the built-in electron population. Multicharged excitonic and biexcitonic emission intensities have activation energy of about 2meV. These results highlight the potential of high quality nanofabricated quantum dots for applications in areas that require fine control of optical emission.

  16. Photon pair sources in AlGaAs: from electrical injection to quantum state engineering

    NASA Astrophysics Data System (ADS)

    Autebert, C.; Boucher, G.; Boitier, F.; Eckstein, A.; Favero, I.; Leo, G.; Ducci, S.

    2015-11-01

    Integrated quantum photonics is a very active field of quantum information, communication, and processing. One of the main challenges to achieve massively parallel systems for complex operations is the generation, manipulation, and detection of many qubits within the same chip. Here, we present our last achievements on AlGaAs quantum photonic devices emitting nonclassical states of light at room temperature by spontaneous parametric down conversion (SPDC). The choice of this platform combines the advantages of a mature fabrication technology, a high nonlinear coefficient, a SPDC wavelength in the C-telecom band and the possibility of electrical injection.

  17. THz laser based on quasi-periodic AlGaAs superlattices

    SciTech Connect

    Malyshev, K V

    2013-06-30

    The use of quasi-periodic AlGaAs superlattices as an active element of a quantum cascade laser of terahertz range is proposed and theoretically investigated. A multi-colour emission, having from three to six peaks of optical gain, is found in Fibonacci, Thue-Morse, and figurate superlattices in electric fields of intensity F = 11 - 13 kV cm{sup -1} in the frequency range f = 2 - 4 THz. The peaks depend linearly on the electric field, retain the height of 20 cm{sup -1}, and strongly depend on the thickness of the AlGaAs-layers. (lasers)

  18. Enhancing the Photocurrent of Top-Cell by Ellipsoidal Silver Nanoparticles: Towards Current-Matched GaInP/GaInAs/Ge Triple-Junction Solar Cells

    PubMed Central

    Bai, Yiming; Yan, Lingling; Wang, Jun; Su, Lin; Yin, Zhigang; Chen, Nuofu; Liu, Yuanyuan

    2016-01-01

    A way to increase the photocurrent of top-cell is crucial for current-matched and highly-efficient GaInP/GaInAs/Ge triple-junction solar cells. Herein, we demonstrate that ellipsoidal silver nanoparticles (Ag NPs) with better extinction performance and lower fabrication temperature can enhance the light harvest of GaInP/GaInAs/Ge solar cells compared with that of spherical Ag NPs. In this method, appropriate thermal treatment parameters for Ag NPs without inducing the dopant diffusion of the tunnel-junction plays a decisive role. Our experimental and theoretical results confirm the ellipsoidal Ag NPs annealed at 350 °C show a better extinction performance than the spherical Ag NPs annealed at 400 °C. The photovoltaic conversion efficiency of the device with ellipsoidal Ag NPs reaches 31.02%, with a nearly 5% relative improvement in comparison with the device without Ag NPs (29.54%). This function of plasmonic NPs has the potential to solve the conflict of sufficient light absorption and efficient carrier collection in GaInP top-cell devices.

  19. Enhancing the Photocurrent of Top-Cell by Ellipsoidal Silver Nanoparticles: Towards Current-Matched GaInP/GaInAs/Ge Triple-Junction Solar Cells.

    PubMed

    Bai, Yiming; Yan, Lingling; Wang, Jun; Su, Lin; Yin, Zhigang; Chen, Nuofu; Liu, Yuanyuan

    2016-05-25

    A way to increase the photocurrent of top-cell is crucial for current-matched and highly-efficient GaInP/GaInAs/Ge triple-junction solar cells. Herein, we demonstrate that ellipsoidal silver nanoparticles (Ag NPs) with better extinction performance and lower fabrication temperature can enhance the light harvest of GaInP/GaInAs/Ge solar cells compared with that of spherical Ag NPs. In this method, appropriate thermal treatment parameters for Ag NPs without inducing the dopant diffusion of the tunnel-junction plays a decisive role. Our experimental and theoretical results confirm the ellipsoidal Ag NPs annealed at 350 °C show a better extinction performance than the spherical Ag NPs annealed at 400 °C. The photovoltaic conversion efficiency of the device with ellipsoidal Ag NPs reaches 31.02%, with a nearly 5% relative improvement in comparison with the device without Ag NPs (29.54%). This function of plasmonic NPs has the potential to solve the conflict of sufficient light absorption and efficient carrier collection in GaInP top-cell devices.

  20. The 1.1 micrometer and visible emission semiconductor diode lasers. [(AlGa)As lasers

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Nuese, C. J.; Kressel, H.

    1978-01-01

    In (AlGa)As, the first of three alloy systems studied, Continuous Wave (CW) operation was obtained at room temperature at a wavelength as low as 7260 A. Reliability in this system was studied in the incoherent mode. Zinc doped devices had significant degradation, whereas Ge or Ge plus Zi doped devices had none. The Al2O3 facet coatings were shown to significantly reduce facet deterioration in all types of lasers, longer wavelength units of that type having accumulated (at the time of writing) 22,000 hours with little if any degradation. A CL study of thin (AlGa)As layers revealed micro fluctuation in composition. A macro-scale fluctuation was observed by electroreflectance. An experimental and theoretical study of the effect of stripe width on the threshold current was carried out. Emission below 7000 A was obtained in VPE grown Ga(AsP) (In,Ga)P with CW operation at 10 C. Lasers and LED's were made by LPE in (InGa) (AsP). Laser thresholds of 5 kA/cm2 were obtained, while LED efficiences were on the order of 2%. Incoherent life test over 6000 hours showed no degradation.

  1. CAB-DWTM for 5 μm trace-width deposition of solar cell metallization top-contacts

    SciTech Connect

    Justin Hoey; Drew Thompson; Matt Robinson; Zakaria Mahmud; Orven F. Swenson; Iskander S. Akhatov; Douglas L. Schulz

    2009-06-08

    This paper reviews methods for creating solar cell grid contacts and explores how cell efficiency can be increased using CAB-DW{trademark}. Specifically, the efficiency of p-i-n structure solar cells built in-house with 90 {micro}m sputtered lines and 5 {micro}m CAB-DW lines were compared. Preliminary results of the comparison show a marked improvement in solar cell efficiency using CAB-DW. In addition to this, a theoretical and experimental analysis of the dynamics of particle impaction on a substrate (i.e. whether particle stick or bounce) will be discussed including how this analysis may lead to further improvement of CAB-DW.

  2. AlGaAs film growth using thermionic vacuum arc (TVA) and determination of its physical properties

    NASA Astrophysics Data System (ADS)

    Özen, Soner; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan

    2015-06-01

    In this research, an AlGaAs film was deposited on a microscope slide by means of the thermionic vacuum arc (TVA) technique which is a novel plasma production technique. AlGaAs structures were grown by this deposition technique for the first time and this process occurred in a very short period of time. In order to characterize the produced film, nano-structural, nano-mechanical, optical, and surface properties were determined by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray diffractometer (XRD) and interferometer. According to the results of the measurements, the mean thickness value of the produced film was obtained as 1.8 μm. The band gap value was determined as 2eV from the Kubelka-Munk plot. The refractive index value was obtained as approximately 3.4. Hardness value was determined as 2 GPa from the Oliver-Pharr method. All these values are consistent with the reported values in the literature for the AlGaAs films produced by different methods. TVA technique appeared as a suitable and promising technique for the production of AlGaAs films.

  3. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  4. Pressure-dependent DLTS (Deep Level Transient Spectroscopy) experiments on Si-doped AlGaAs

    NASA Astrophysics Data System (ADS)

    Farmer, J. W.; Hjalmarson, H. P.; Samara, G. A.

    Pressure dependent Deep Level Transient Spectroscopy (DLTS) experiments are used to measure the properties of the deep donors (DX-centers) responsible for the persistent photoconductivity effect in Si-doped AlGaAs. The sample dependence of the DLTS spectra shows evidence for a defect complex involved in the DX-center.

  5. Relativistic Electrons Produced by Reconnecting Electric Fields in a Laser-driven Bench-top Solar Flare

    NASA Astrophysics Data System (ADS)

    Zhong, J. Y.; Lin, J.; Li, Y. T.; Wang, X.; Li, Y.; Zhang, K.; Yuan, D. W.; Ping, Y. L.; Wei, H. G.; Wang, J. Q.; Su, L. N.; Li, F.; Han, B.; Liao, G. Q.; Yin, C. L.; Fang, Y.; Yuan, X.; Wang, C.; Sun, J. R.; Liang, G. Y.; Wang, F. L.; Ding, Y. K.; He, X. T.; Zhu, J. Q.; Sheng, Z. M.; Li, G.; Zhao, G.; Zhang, J.

    2016-08-01

    Laboratory experiments have been carried out to model the magnetic reconnection process in a solar flare with powerful lasers. Relativistic electrons with energy up to megaelectronvolts are detected along the magnetic separatrices bounding the reconnection outflow, which exhibit a kappa-like distribution with an effective temperature of ˜109 K. The acceleration of non-thermal electrons is found to be more efficient in the case with a guide magnetic field (a component of a magnetic field along the reconnection-induced electric field) than in the case without a guide field. Hardening of the spectrum at energies ≥500 keV is observed in both cases, which remarkably resembles the hardening of hard X-ray and γ-ray spectra observed in many solar flares. This supports a recent proposal that the hardening in the hard X-ray and γ-ray emissions of solar flares is due to a hardening of the source-electron spectrum. We also performed numerical simulations that help examine behaviors of electrons in the reconnection process with the electromagnetic field configurations occurring in the experiments. The trajectories of non-thermal electrons observed in the experiments were well duplicated in the simulations. Our numerical simulations generally reproduce the electron energy spectrum as well, except for the hardening of the electron spectrum. This suggests that other mechanisms such as shock or turbulence may play an important role in the production of the observed energetic electrons.

  6. High power master oscillator power amplifier (MOPA) AlGaAs laser for intersatellite communications

    NASA Technical Reports Server (NTRS)

    Cornwell, Donald M., Jr.

    1992-01-01

    A master oscillator power amplifier (MOPA) configuration has been developed using an anti-reflection-coated AlGaAs semiconductor broad area laser in a reflective amplifier mode. For CW injection, the MOPA produced 340 mW of diffraction-limited power. The semiconductor MOPA configuration also produced peak diffraction-limited powers of 360 mW and 320 mW for quaternary pulse position Q-PPM modulation rates of 50 Mbps and 325 Mbps, respectively, for a peak injected power of 100 mW. Angular beamsteering during modulation was minimized by collimating the injected beam. The diffraction-limited peak power was limited by the frequency chirp of the master oscillator and also by the coupling losses of the injected beam.

  7. AlGaAs growth by OMCVD using an excimer laser

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Wilt, David M.; Pouch, John J.; Aron, Paul R.

    1986-01-01

    AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H2, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.

  8. Progress in a-SiOx:H thin film solar cells with patterned MgF2 dielectric for top cell of multi-junction system

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Won; Sichanugrist, Porponth; Konagai, Makoto

    2016-07-01

    We successfully designed and experimentally demonstrated an application of patterned MgF2 dielectric material at rear Al-doped ZnO (AZO)/Ag interface in thin film amorphous silicon oxide ( a-SiOx:H) solar cells. When it was realized in practical device process, MgF2 coverage with patterned morphology was employed to allow for current flow between the AZO and Ag against highly resistive MgF2 material. On the basis of the suggested structure, we found an improvement in quantum efficiency of the solar cells with the patterned MgF2. In addition, an enhancement of open circuit voltage ( V oc ) and fill factor ( FF) was observed. A remarkable increase in shunt resistance of the cells with the MgF2 would possibly indicate that the highly resistive MgF2 layer can partly suppress physical shunting across top and bottom electrodes caused by very thin absorber thickness of only 100 nm. The approach showed that our best-performing device revealed an essential improvement in conversion efficiency from 7.83 to 8.01% with achieving markedly high V oc (1.013 V) and FF (0.729). [Figure not available: see fulltext.

  9. Recent advancements in monolithic AlGaAs/GaAs solar cells for space applications

    NASA Technical Reports Server (NTRS)

    Wickham, K. R.; Chung, B.-C.; Klausmeier-Brown, M.; Kuryla, M. S.; Ristow, M. Ladle; Virshup, G. F.; Werthen, J. G.

    1991-01-01

    High efficiency, two terminal, multijunction AlGaAs/GaAs solar cells were reproducibly made with areas of 0.5 sq cm. The multiple layers in the cells were grown by Organo Metallic Vapor Phase Epitaxy (OMVPE) on GaAs substrates in the n-p configuration. The upper AlGaAs cell has a bandgap of 1.93 eV and is connected in series to the lower GaAs cell (1.4 eV) via a metal interconnect deposited during post-growth processing. A prismatic coverglass is installed on top of the cell to reduce obscuration caused by the gridlines. The best 0.5 sq cm cell has a two terminal efficiency of 23.0 pct. at 1 sun, air mass zero (AM0) and 25 C. To date, over 300 of these cells were grown and processed for a manufacturing demonstration. Yield and efficiency data for this demonstration are presented. As a first step toward the goal of a 30 pct. efficient cell, a mechanical stack of the 0.5 sq cm cells described above, and InGaAsP (0.95 eV) solar cells was made. The best two terminal measurement to date yields an efficiency of 25.2 pct. AM0. This is the highest reported efficiency of any two terminal, 1 sun space solar cell.

  10. AlGaAs-GaAs cascade solar cell

    NASA Technical Reports Server (NTRS)

    Lamorte, M. F.; Abbott, D. H.

    1980-01-01

    Computer modeling studies are reported for a monolithic, two junction, cascade solar cell using the AlGaAs GaAs materials combination. An optimum design was obtained through a serial optimization procedure by which conversion efficiency is maximized for operation at 300 K, AM 0, and unity solar concentration. Under these conditions the upper limit on efficiency was shown to be in excess of 29 percent, provided surface recombination velocity did not exceed 10,000 cm/sec.

  11. Black silicon solar thin-film microcells integrating top nanocone structures for broadband and omnidirectional light-trapping

    NASA Astrophysics Data System (ADS)

    Xu, Zhida; Yao, Yuan; Brueckner, Eric P.; Li, Lanfang; Jiang, Jing; Nuzzo, Ralph G.; Logan Liu, Gang

    2014-08-01

    Recently developed classes of monocrystalline silicon solar microcells (μ-cell) can be assembled into modules with characteristics (i.e., mechanically flexible forms, compact concentrator designs, and high-voltage outputs) that would be impossible to achieve using conventional, wafer-based approaches. In this paper, we describe a highly dense, uniform and non-periodic nanocone forest structure of black silicon (bSi) created on optically-thin (30 μm) μ-cells for broadband and omnidirectional light-trapping with a lithography-free and high-throughput plasma texturizing process. With optimized plasma etching conditions and a silicon nitride passivation layer, black silicon μ-cells, when embedded in a polymer waveguiding layer, display dramatic increases of as much as 65.7% in short circuit current, as compared to a bare silicon device. The conversion efficiency increases from 8.1% to 11.5% with a small drop in open circuit voltage and fill factor.

  12. Observation of Ge bottom cells in InGaP/InGaAs/Ge triple-junction solar cells

    NASA Astrophysics Data System (ADS)

    Jung, Haeyong; Jung, Sang Hyun; Kim, Chang Zoo; Jun, Dong Hwan; Kang, Ho Kwan; Kim, Hogyoung

    2014-10-01

    After growing InGaP/InGaAs/Ge triple-junction solar cells, we prepared two different Ge cells by etching down to the GaAs buffer layer (sample A) and the AlGaAs layer (sample B). Then, the photovoltaic properties of these two Ge cells were investigated under various light concentrations in order to find the factors affecting the overall performance of the triple-junction solar cells. Under concentrated light, the open-circuit voltage ( V OC ), fill factor and conversion efficiency were higher for sample A than for sample B. The external quantum efficiency was shown to have a slightly higher value for sample A. Both the tunnel junction layer and the top contact resistance increased the series resistance, which also provided defects acting as leakage path. A comparison to previous works suggests that the conversion efficiency of Ge bottom, if present, is degraded marginally after the growth of the full structure of triple-junction solar cells.

  13. Multi-user quantum key distribution with entangled photons from an AlGaAs chip

    NASA Astrophysics Data System (ADS)

    Autebert, C.; Trapateau, J.; Orieux, A.; Lemaître, A.; Gomez-Carbonell, C.; Diamanti, E.; Zaquine, I.; Ducci, S.

    2016-12-01

    In view of real-world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip-emitting polarisation entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.

  14. Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs.

    PubMed

    Heyn, Christian; Zocher, Michel; Schnüll, Sandra; Hansen, Wolfgang

    2016-12-01

    Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

  15. Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs

    NASA Astrophysics Data System (ADS)

    Heyn, Christian; Zocher, Michel; Schnüll, Sandra; Hansen, Wolfgang

    2016-09-01

    Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

  16. Quasiperiodic AlGaAs superlattices for neuromorphic networks and nonlinear control systems

    SciTech Connect

    Malyshev, K. V.

    2015-01-28

    The application of quasiperiodic AlGaAs superlattices as a nonlinear element of the FitzHugh–Nagumo neuromorphic network is proposed and theoretically investigated on the example of Fibonacci and figurate superlattices. The sequences of symbols for the figurate superlattices were produced by decomposition of the Fibonacci superlattices' symbolic sequences. A length of each segment of the decomposition was equal to the corresponding figurate number. It is shown that a nonlinear network based upon Fibonacci and figurate superlattices provides better parallel filtration of a half-tone picture; then, a network based upon traditional diodes which have cubic voltage-current characteristics. It was found that the figurate superlattice F{sup 0}{sub 11}(1) as a nonlinear network's element provides the filtration error almost twice less than the conventional “cubic” diode. These advantages are explained by a wavelike shape of the decreasing part of the quasiperiodic superlattice's voltage-current characteristic, which leads to multistability of the network's cell. This multistability promises new interesting nonlinear dynamical phenomena. A variety of wavy forms of voltage-current characteristics opens up new interesting possibilities for quasiperiodic superlattices and especially for figurate superlattices in many areas—from nervous system modeling to nonlinear control systems development.

  17. Quasiperiodic AlGaAs superlattices for neuromorphic networks and nonlinear control systems

    NASA Astrophysics Data System (ADS)

    Malyshev, K. V.

    2015-01-01

    The application of quasiperiodic AlGaAs superlattices as a nonlinear element of the FitzHugh-Nagumo neuromorphic network is proposed and theoretically investigated on the example of Fibonacci and figurate superlattices. The sequences of symbols for the figurate superlattices were produced by decomposition of the Fibonacci superlattices' symbolic sequences. A length of each segment of the decomposition was equal to the corresponding figurate number. It is shown that a nonlinear network based upon Fibonacci and figurate superlattices provides better parallel filtration of a half-tone picture; then, a network based upon traditional diodes which have cubic voltage-current characteristics. It was found that the figurate superlattice F011(1) as a nonlinear network's element provides the filtration error almost twice less than the conventional "cubic" diode. These advantages are explained by a wavelike shape of the decreasing part of the quasiperiodic superlattice's voltage-current characteristic, which leads to multistability of the network's cell. This multistability promises new interesting nonlinear dynamical phenomena. A variety of wavy forms of voltage-current characteristics opens up new interesting possibilities for quasiperiodic superlattices and especially for figurate superlattices in many areas—from nervous system modeling to nonlinear control systems development.

  18. Status of GaAs/Ge solar cells

    NASA Technical Reports Server (NTRS)

    Iles, P. A.; Ho, F.; Yeh, Y. C. M.

    1991-01-01

    With experience at increasing production levels, GaAs/Ge cells are proving their effectiveness for some demanding missions. The experience in producing inactive-Ge structures should benefit parallel work on forming monolithic cascade cells using AlGaAs or GaAs top cell layers grown on Ge or other bottom cell materials. The adjustments needed to ensure that the GaAs/Ge interface is inactive are more likely to preserve the properties of a separately optimized bottom cell.

  19. In-Situ Fabrication of a Self-Aligned Selective Emitter Silicon Solar Cell Using the Gold Top Contacts To Facilitate the Synthesis of a Nanostructured Black Silicon Antireflective Layer Instead of an External Metal Nanoparticle Catalyst.

    PubMed

    Lu, Yen-Tien; Barron, Andrew R

    2015-06-10

    Silicon solar cells with nanopore-type black silicon (b-Si) antireflection (AR) layers and self-aligned selective emitter (SE) are reported in which the b-Si structure is prepared without the traditional addition of a nanoparticle (NP) catalyst. The contact-assisted chemical etching (CACE) method is reported here for the first time, in which the metal top contacts on silicon solar cell surfaces function as the catalysts for b-Si fabrication and the whole etching process can be done in minutes at room temperature. The CACE method is based on the metal-assisted chemical etching (MACE) solution but without or metal precursor in the Si etchant (HF:H2O2:H2O), and the Au top contacts, or catalysts, are not removed from the solar cell surface after the etching. The effects of etching time, HF and H2O2 concentration, and the HF:H2O2 ratio on the b-Si morphology, surface reflectivity, and solar cell efficiency have been investigated. Higher [HF] and [H2O2] with longer etching time cause collapse of the b-Si nanoporous structure and penetration of the p-n junctions, which are detrimental to the solar cell efficiency. The b-Si solar cell fabricated with the HF:H2O2:H2O volume ratio of 3:3:20 and a 3 min etch time shows the highest efficiency 8.99% along with a decrease of reflectivity from 36.1% to 12.6% compared to that of the nonetched Si solar cell.

  20. A top-down approach to determine carbon monoxide (CO) emissions in the Mexico Megacity using ground based FTIR solar and lunar absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Stremme, Wolfgang; Ortega, Ivan; Garcia, Agustin; Grutter, Michel

    2010-05-01

    The carbon monoxide (CO) total column has been measured by ground based solar and lunar FTIR absorption spectroscopy with 0.5 cm-1 resolution since October 2007 at the UNAM Campus in Mexico City (19,33°N, 99.18°W). The CO column density is retrieved using the SFIT2 retrieval code based on the optimal estimation theory (Rodgers 1976). The time series of the CO-column retrievals show different diurnal behaviours compared to the surface CO concentration. This is explained by the change in the vertical distribution which is dominated by the evolution of the mixing layer height (MLH). The CO column shows a diurnal and weekly pattern depending on the wind speed and traffic, but is not directly dependent on the mixing layer height. A comparison of the measured CO-column, CO-surface concentration and the reconstructed MLH with results from regional MCCM (Grell et al , 2000) model will be presented. Based on the information of the vertical structure, the surface wind fields and surface CO concentrations that are provided by LIDAR measurements, the meteorological and air quality networks, it is possible to estimate the horizontal CO-transport. The CO surface emissions can therefore be calculated from the CO column growth rate. For horizontal homogeneous conditions, the CO column density growth-rate directly gives the surface emission. A first top-down CO emission estimation is presented and compared with the official inventory (bottom-up approach) and other estimations used in recent studies on Mexico City. Monitoring of CO columns in megacities provides new information of the anthropogenic emissions on a regional scale and helps to link the understanding of the CO budget from local to the global scale.

  1. DLTS study of deep centers created by Ar-ion bombardment in n- and p-type MBE AlGaAs

    NASA Astrophysics Data System (ADS)

    Kaniewska, M.; Sadowski, J.; Guziewicz, M.

    2004-07-01

    The thermal emission rate of dominant traps in molecular beam epitaxial n- and p-type AlGaAs subjected to Ar-ion beam etching has been studied by deep level transient spectroscopy. Emission signatures were determined and compared with results obtained by other authors for irradiation induced and grown-in defects in GaAs and AlGaAs. The most significant result of this study is the observation that the process-induced defects in n- as well as p-type AlGaAs exhibit emission signatures, which are characteristic of native defects found in GaAs. The effect is discussed in terms of a compensation effect and related band bending.

  2. GaAs (AlGaAs)/CuInSe2 tandem solar cells. Technology status and future directions

    NASA Technical Reports Server (NTRS)

    Kim, N. P.; Burgess, R. M.; Gale, R. P.; Mcclelland, R. W.

    1991-01-01

    Mechanically stacked, high efficiency, lightweight, and radiation resistant photovoltaic cells based on a GaAs thin film top and CuInSe2 thin film bottom cells were developed, and are considered one of the most promising devices for planar solar array applications. The highest efficiency demonstrated so far using the 4 sq cm design is 23.1 pct. AM0, one sun efficiency when measured in four-terminal configuration. The current status of the GaAs(AlGaAs)/CuInSe2 tandem cell program is presented and future directions that will lead to cell efficiencies higher than 26 pct. Air Mass Zero (AM0). A new 8 sq cm cell design developed for a two terminal and voltage matched configuration to minimize wiring complexity is discussed. Optimization of the GaAs structure for a higher end-of-life performance and further improvement of tandem cells by utilizing AlGaAs as an top absorber are described. Results of environmental tests conducted with these thin film GaAs/CuInSe2 tandem cells are also summarized.

  3. Interface induced uniaxial magnetic anisotropy in amorphous CoFeB films on AlGaAs(001).

    PubMed

    Hindmarch, A T; Kinane, C J; MacKenzie, M; Chapman, J N; Henini, M; Taylor, D; Arena, D A; Dvorak, J; Hickey, B J; Marrows, C H

    2008-03-21

    We demonstrate an isolated magnetic interface anisotropy in amorphous CoFeB films on (Al)GaAs(001), similar to that in epitaxial films but without a magnetocrystalline anisotropy term. The direction of the easy axis corresponds to that due to the interfacial interaction proposed for epitaxial films. We show that the anisotropy is determined by the relative orbital component of the atomic magnetic moments. Charge transfer is ruled out as the origin of the interface anisotropy, and it is postulated that the spin-orbit interaction in the semiconductor is crucial in determining the magnetic anisotropy.

  4. Structural dependences of localization and recombination of photogenerated carriers in the top GaInP Subcells of GaInP/GaAs double-junction tandem solar cells.

    PubMed

    Deng, Zhuo; Ning, Jiqiang; Su, Zhicheng; Xu, Shijie; Xing, Zheng; Wang, Rongxin; Lu, Shulong; Dong, Jianrong; Zhang, Baoshun; Yang, Hui

    2015-01-14

    In high-efficiency GaInP/GaAs double-junction tandem solar cells, GaInP layers play a central role in determining the performance of the solar cells. Therefore, gaining a deeper understanding of the optoelectronic processes in GaInP layers is crucial for improving the energy conversion efficiency of GaInP-based photovoltaic devices. In this work, we firmly show strong dependences of localization and recombination of photogenerated carriers in the top GaInP subcells in the GaInP/GaAs double-junction tandem solar cells on the substrate misorientation angle with excitation intensity- and temperature-dependent photoluminescence (PL). The entire solar cell structures including GaInP layers were grown with metalorganic chemical vapor deposition on GaAs substrates with misorientation angles of 2° (denoted as Sample 2°) and 7° (Sample 7°) off (100) toward (111)B. The PL spectral features of the two top GaInP subcells, as well as their excitation-power and temperature dependences exhibit remarkable variation on the misorientation angle. In Sample 2°, the dominant localization mechanism and luminescence channels are due to the energy potential minima caused by highly ordered atomic domains; In Sample 7°, the main localization and radiative recombination of photogenerated carriers occur in the atomically disordered regions. Our results reveal a more precise picture on the localization and recombination mechanisms of photogenerated carriers in the top GaInP subcells, which could be the crucial factors in controlling the optoelectronic efficiency of the GaInP-based multijunction photovoltaic devices.

  5. Architectural Tops

    ERIC Educational Resources Information Center

    Mahoney, Ellen

    2010-01-01

    The development of the skyscraper is an American story that combines architectural history, economic power, and technological achievement. Each city in the United States can be identified by the profile of its buildings. The design of the tops of skyscrapers was the inspiration for the students in the author's high-school ceramic class to develop…

  6. Accelerated aging of GaAs concentrator solar cells

    SciTech Connect

    Gregory, P.E.

    1982-04-01

    An accelerated aging study of AlGaAs/GaAs solar cells has been completed. The purpose of the study was to identify the possible degradation mechanisms of AlGaAs/GaAs solar cells in terrestrial applications. Thermal storage tests and accelerated AlGaAs corrosion studies were performed to provide an experimental basis for a statistical analysis of the estimated lifetime. Results of this study suggest that a properly designed and fabricated AlGaAs/GaAs solar cell can be mechanically rugged and environmentally stable with projected lifetimes exceeding 100 years.

  7. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Line width of a single longitudinal mode emitted by an AlGaAs heterojunction laser

    NASA Astrophysics Data System (ADS)

    Bogatov, Alexandr P.; Eliseev, P. G.; Luk'yanov, S. A.; Pak, G. T.; Petrakova, T. V.

    1988-11-01

    A nonmonotonic dependence of the emission line width on the power was observed for a single longitudinal mode of an AlGaAs heterojunction laser. This behavior could be due to the dependence of the waveguide coefficient of the amplitude-phase coupling on the nature of operation of the laser.

  8. Temperature coefficients of multijunction solar cells

    NASA Technical Reports Server (NTRS)

    Virshup, G. F.; Chung, B.-C.; Ladle Ristow, M.; Kuryla, M. S.; Brinker, D.

    1990-01-01

    Temperature coefficients measured in solar simulators with those measured under AM0 solar illumination are compared to illustrate the challenges in making these measurements. It is shown that simulator measurements of the short-circuit current (delta Jsc/delta T) are inaccurate due to the mismatch between the solar spectrum and the simulators at the bandgaps of the solar cells. Especially susceptible to error is the delta Jsc/delta T of cells which are components in monolithic multijunction solar cells, such as GaAs filtered by 1.93-eV AlGaAs, which has an AM0 coefficient of 6.82 micro-A/sq cm/deg C, compared to a Xenon simulator coefficient of 22.2 micro-A/sq cm/deg C.

  9. High-power single spatial mode AlGaAs channeled-substrate-planar semiconductor diode lasers for spaceborne communications

    NASA Technical Reports Server (NTRS)

    Connolly, J. C.; Carlin, D. B.; Ettenberg, M.

    1989-01-01

    A high power single spatial mode channeled substrate planar AlGaAs semiconductor diode laser was developed. The emission wavelength was optimized at 860 to 880 nm. The operating characteristics (power current, single spatial mode behavior, far field radiation patterns, and spectral behavior) and results of computer modeling studies on the performance of the laser are discussed. Reliability assessment at high output levels is included. Performance results on a new type of channeled substrate planar diode laser incorporating current blocking layers, grown by metalorganic chemical vapor deposition, to more effectively focus the operational current to the lasing region was demonstrated. The optoelectronic behavior and fabrication procedures for this new diode laser are discussed. The highlights include single spatial mode devices with up to 160 mW output at 8600 A, and quantum efficiencies of 70 percent (1 W/amp) with demonstrated operating lifetimes of 10,000 h at 50 mW.

  10. Measuring the Degeneracy of Discrete Energy Levels Using a GaAs /AlGaAs Quantum Dot

    NASA Astrophysics Data System (ADS)

    Hofmann, A.; Maisi, V. F.; Gold, C.; Krähenmann, T.; Rössler, C.; Basset, J.; Märki, P.; Reichl, C.; Wegscheider, W.; Ensslin, K.; Ihn, T.

    2016-11-01

    We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs /AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.

  11. Distinguishing impurity concentrations in GaAs and AlGaAs using very shallow undoped heterostructures

    NASA Astrophysics Data System (ADS)

    Mak, W. Y.; Das Gupta, K.; Beere, H. E.; Farrer, I.; Sfigakis, F.; Ritchie, D. A.

    2010-12-01

    We have developed a method of fabricating very shallow, gateable, undoped two-dimensional electron gases (2DEG) and making very low resistivity contacts to these. We studied the evolution of mobility as a function of the depth of the 2DEG (from 310 to 30 nm). We extract quantitative information about the background impurity concentrations in GaAs and AlGaAs, the interface roughness, and the charge in the surface states. Surface charge sets an intrinsic limit to the mobility of very shallow 2DEGs. It is probably impossible to fabricate such shallow high-mobility 2DEGs using modulation doping due to the need to accommodate a spacer layer.

  12. Optical reflection from the Bragg lattice of AsSb metal nanoinclusions in an AlGaAs matrix

    SciTech Connect

    Ushanov, V. I.; Chaldyshev, V. V.; Preobrazhenskii, V. V.; Putyato, M. A.; Semyagin, B. R.

    2013-08-15

    The optical properties of metal-semiconductor metamaterials based on an AlGaAs matrix are studied. The specific feature of these materials is that there are As and AsSb nanoinclusion arrays which modify the dielectric properties of the material. These nanoinclusions are randomly arranged in the medium or form a Bragg structure with a reflectance peak at a wavelength close to 750 nm, corresponding to the transparency region of the matrix. The reflectance spectra are studied for s- and p-polarized light at different angles of incidence. It is shown that (i) As nanoinclusion arrays only slightly influence the optical properties of the medium in the wavelength range 700-900 nm, (ii) chaotic AsSb nanoinclusion arrays cause strong scattering of light, and (iii) the spatial periodicity in the arrangement of AsSb nanoinclusions is responsible for Bragg resonance in the optical reflection.

  13. Long-term temperature effects on GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Heinbockel, J. H.; Hong, K. H.

    1979-01-01

    The thermal degradation of AlGaAs solar cells resulting from a long-term operation in a space environment is investigated. The solar cell degradation effects caused by zinc and aluminum diffusion as well as deterioration by arsenic evaporation are presented. Also, the results are presented of experimental testing and measurements of various GaAs solar cell properties while the solar cell was operating in the temperature range of 27 C to 350 C. In particular, the properties of light current voltage curves, dark current voltage curves, and spectral response characteristics are given. Finally, some theoretical models for the annealing of radiation damage over various times and temperatures are included.

  14. High-Absorption-Efficiency Superlattice Solar Cells by Excitons

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Onomitsu, Koji; Horikoshi, Yoshiji

    2013-11-01

    The effect of excitonic absorption on solar cell efficiency has been investigated using solar cells with AlGaAs/GaAs superlattice structures. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption of bulk GaAs. Excitonic absorption shows strong and sharp peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of the superlattice solar cells are quite similar to the calculated absorption spectra considering the excitonic effect. The superlattice solar cells are confirmed to have high absorption coefficient compared with the GaAs and AlGaAs bulk solar cells. These results suggest that the enhanced absorption by excitons can increase the quantum efficiency of solar cells. This effect is more prominent for the solar cells with small absorption layer thicknesses.

  15. Terrestrial solar thermionic energy conversion systems concept

    NASA Technical Reports Server (NTRS)

    Shimada, K.; Swerdling, M.

    1975-01-01

    Results obtained from studies of a (1) solar concentrator, (2) solar energy receiver - thermionic converter system, and (3) solar thermionic topping system are described. Peripheral subsystems, which are required for any solar energy conversion system, are also discussed.

  16. The influence of Sb doping on the growth and electronic properties of GaAs(100) and AlGaAs(100)

    NASA Technical Reports Server (NTRS)

    Jamison, K. D.; Chen, H. C.; Bensaoula, A.; Lim, W.; Trombetta, L.

    1989-01-01

    Isoelectronic doping using antimony has been shown to reduce traps and improve material properties during epitaxial growth of Si doped GaAs(100) and AlGaAs(100). In this study, the effect of the antimony dopant on the optimal growth temperature is examined with the aim of producing high-quality heterostructures at lower temperatues. High-quality films of GaAs and AlGaAs have been grown by molecular-beam epitaxy at the normal growth temperatures of 610 and 700 C, respectively, and 50-100 C below this temperature using varying small amounts of Sb as a dopant. Electrical properties of the films were then examined using Hall mobility measurements and deep-level transient spectroscopy.

  17. Progress toward a 30 percent-efficient, monolithic, three-junction, two-terminal concentrator solar cell for space applications

    NASA Technical Reports Server (NTRS)

    Partain, L. D.; Chung, B.-C.; Virshup, G. F.; Schultz, J. C.; Macmillan, H. F.; Ristow, M. Ladle; Kuryla, M. S.; Bertness, K. A.

    1991-01-01

    Component efficiencies of 0.2/sq cm cells at approximately 100x AMO light concentration and 80 C temperatures are not at 15.3 percent for a 1.9 eV AlGaAs top cell, 9.9 percent for a 1.4 eV GaAs middle cell under a 1.9 eV AlGaAs filter, and 2.4 percent for a bottom 1.0 eV InGaAs cell under a GaAs substrate. The goal is to continue improvement in these performance levels and to sequentially grow these devices on a single substrate to give 30 percent efficient, monolithic, two-terminal, three-junction space concentrator cells. The broad objective is a 30 percent efficient monolithic two-terminal cell that can operate under 25 to 100x AMO light concentrations and at 75 to 100 C cell temperatures. Detailed modeling predicts that this requires three junctions. Two options are being pursued, and both use a 1.9 eV AlGaAs top junction and a 1.4 eV GaAs middle junction grown by a 1 atm OMVPE on a lattice matched substrate. Option 1 uses a low-doped GaAs substrate with a lattice mismatched 1.0 eV InGaAs cell formed on the back of the substrate. Option 2 uses a Ge substrate to which the AlGaAs and GaAs top junctions are lattice matched, with a bottom 0.7 eV Ge junction formed near the substrate interface with the GaAs growth. The projected efficiency contributions are near 16, 11, and 3 percent, respectively, from the top, middle, and bottom junctions.

  18. Gap/silicon Tandem Solar Cell with Extended Temperature Range

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A. (Inventor)

    2006-01-01

    A two-junction solar cell has a bottom solar cell junction of crystalline silicon, and a top solar cell junction of gallium phosphide. A three (or more) junction solar cell has bottom solar cell junctions of silicon, and a top solar cell junction of gallium phosphide. The resulting solar cells exhibit improved extended temperature operation.

  19. Measurement and simulation of top- and bottom-illuminated solar-blind AlGaN metal-semiconductor-metal photodetectors with high external quantum efficiencies

    SciTech Connect

    Brendel, Moritz Helbling, Markus; Knigge, Andrea; Brunner, Frank; Weyers, Markus

    2015-12-28

    A comprehensive study on top- and bottom-illuminated Al{sub 0.5}Ga{sub 0.5}N/AlN metal-semiconductor-metal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold and saturation behavior as a function of applied bias voltage up to 50 V reaching about 50% for 0.1 μm and 67% for 0.5 μm thick absorber layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion modeling results. By taking into account macroscopic polarization effects in the hexagonal metal-polar +c-plane AlGaN/AlN heterostructures, new insights into the general device functionality of AlGaN-based MSM photodetectors are obtained. The observed threshold/saturation behavior is caused by a bias-dependent extraction of photoexcited holes from the Al{sub 0.5}Ga{sub 0.5}N/AlN interface. While present under bottom illumination for any AlGaN layer thickness, under top illumination this mechanism influences the EQE-bias characteristics only for thin layers.

  20. Excitation and de-excitation mechanisms of Er-doped GaAs and AlGaAs

    NASA Astrophysics Data System (ADS)

    Elsaesser, David W.

    1992-12-01

    Electrical and optical characterization have been performed on GaAs and Al(x)Ga(1-x)As samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (ErGa) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial position (Er(i)). Annealing studies performed on Er-implanted GaAs indicated that the ErGa center preferentially formed at higher annealing temperatures (greater than 850 C), with the Er(i) reaching a maximum concentration at an annealing temperature of around 750 C. Optical characterization performed by Photoluminescence (PL) measurements showed that the Er(i) center gave a much stronger Er-related intra-4f shell emission. Mechanisms for the excitation of the 4f shells of these two centers are discussed. Similar optically active Eri centers may be forming in AlGaAs.

  1. Quantum-well lasers for direct solar photopumping

    NASA Astrophysics Data System (ADS)

    Unnikrishnan, Sreenath; Anderson, Neal G.

    1993-09-01

    Semiconductor lasers directly photopumped by focused sunlight may be viable sources of coherent light for intersatellite communications and other low-power spaceborne applications. In this work, we theoretically explore the possibility of realizing such devices. We specifically assess solar pumped operation of separate-confinement-quantum-well heterostructure (SCQWH) lasers based on InGaAs, GaAs, and AlGaA, as fabrication technology for these lasers is mature and they can operate at very low thresholds. We develop a model for step-index single-well SCQWH lasers photopumped by sunlight, examine how threshold solar photoexcitation intensities depend upon material and structure parameters, design optimum structures for solar-pumped operation, and identify design tradeoffs. Our results suggest that laser action should be possible in properly designed structures at readily achievable solar concentrations and that optimum designs for solar-pumped SCQWH lasers differ significantly from those for analogous current injection devices.

  2. Material quality frontiers of MOVPE grown AlGaAs for minority carrier devices

    NASA Astrophysics Data System (ADS)

    Heckelmann, S.; Lackner, D.; Dimroth, F.; Bett, A. W.

    2017-04-01

    In this study, secondary ion mass spectroscopy of oxygen, deep level transient spectroscopy and power dependent relative photoluminescence are compared regarding their ability to resolve differences in AlxGa1-xAs material quality. AlxGa1-xAs samples grown with two different trimethylaluminum sources showing low and high levels of oxygen contamination are compared. As tested in the growth of minority carrier devices, i.e. AlxGa1-xAs solar cells, the two precursors clearly lead to different device characteristics. It is shown that secondary ion mass spectroscopy could not resolve the difference in oxygen concentration, whereas deep level transient spectroscopy and photoluminescence based measurements indicate the influence of the precursor oxygen level on the material quality.

  3. High-efficiency ({eta} = 39.6%, AM 1.5D) cascade of photoconverters in solar splitting systems

    SciTech Connect

    Khvostikov, V. P. Vlasov, A. S.; Sorokina, S. V.; Potapovich, N. S.; Timoshina, N. Kh.; Shvarts, M. Z.; Andreev, V. M.

    2011-06-15

    A concentrator photovoltaic module with spectral splitting of solar radiation is developed. The module is based on a Fresnel lens and two dichroic filters. Solar cells based on AlGaAs and GaAs are grown by low-temperature liquid-phase epitaxy. GaSb photoconverters are fabricated by zinc gas-phase diffusion into a base epitaxial layer or an n-type GaSb substrate. The total efficiency of three solar cells developed for the spectral splitting module reached 39.6% (AM 1.5D spectrum).

  4. Electrical activation of carbon δ-doped (Al,Ga)As grown by metalorganic vapour-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Li, G.; Petravić, M.; Jagadish, C.

    1997-04-01

    Carbon δ-doped (Al,Ga)As was grown by metalorganic vapour-phase epitaxy using trimethylaluminium (TMAl) or trimethylgallium (TMGa) as a doping precursor. The best C δ-doped Al 0.3Ga 0.7As has a peak hole density of 1.6 × 10 19 (1.4 × 10 19 for GaAs) cm -3 with a full hole profile width at half maximum of 85 Å (84 Å for GaAs). For C δ-doped Al 0.3Ga 0.7 As grown at 630°C, the use of TMGa as a doping precursor leads to both the sheet C atom density and the free hole density increasing with an increase in the total TMGa moles introduced during a δ-doping step. As a result, the electrical activation remains almost constant with the change of TMGa moles supplied. The sheet C atom density always increases with increasing supply of TMAl, but approaches its maximum value at an amount of TMAl of 6.4 × 10 -7 mol. The electrical activation reduces from > 90% to < 10% when the supply of TMAl increases from 2.1 × 10 -7 to 8 × 10 -7 mol. Regardless of the doping precursors, the hole density weakly decreases and the C atom density significantly increases with increasing growth temperature. Low growth temperatures are required for high electrical activation. Using optimised growth conditions, C δ-doped pipi doping superlattices with different average hole densities are fabricated to obtain C bulk-doped-like layers.

  5. Quantum-well intermixing for the control of second-order nonlinear effects in AlGaAs multiple-quantum-well waveguides.

    PubMed

    Street, M W; Whitbread, N D; Hutchings, D C; Arnold, J M; Marsh, J H; Aitchison, J S; Kennedy, G T; Sibbett, W

    1997-11-01

    We present experimental evidence to demonstrate the feasibility of a promising new quasi-phase-matching technique in AlGaAs multiple-quantum-well waveguides. Non-phase-matched second-harmonic-generation measurements indicate that, for sub-half-bandgap excitation near 1.5 microm , quantum-well intermixing by impurity-free vacancy disordering results in a reduction of the nonlinear susceptibility chi((2))(zxy) (~340 pm/V) by 17%. Relatively low intermixed waveguide losses, and the high spatial resolution of the impurity-free vacancy disordering process, suggest that periodic intermixing along the direction of propagation should lead to useful frequency-conversion efficiencies.

  6. Top physics at CDF

    SciTech Connect

    Julia Thom

    2004-06-24

    Precision studies of top quark properties are a primary goal of the Run II physics program at the Fermilab Tevatron. Marking the first stages of this program, the CDF collaboration presents recent results on top pair production cross section, single top physics and top mass, using between 109 and 200 pb{sup -1} of Run II data.

  7. Space concentrator solar cells based on multilayer LPE grown AlGaAs/GaAs heterostructure

    NASA Technical Reports Server (NTRS)

    Khvostikov, V. P.; Larionov, V. R.; Paleeva, E. V.; Sorokina, S. V.; Chosta, O. I.; Shvarts, M. Z.; Zimogorova, N. S.

    1995-01-01

    The high efficiency solar cells based on multilayer AlGaAs/GaAs heterostructures, prepared by low temperature liquid phase epitaxy (LPE), were developed and tested. An investigation of the low temperature LPE process for the crystallization of AlGaAs heterostructures of as high as 24.0 to 24.7 percent under AMO conditions at concentration ratios of 20 to 100x, were reached. Developed solar cells show substantial radiation resistance to the damage induced by 3.75 MeV electrons.

  8. Effects of surface barrier layer in AlGaAs/GaAs solar cells

    NASA Astrophysics Data System (ADS)

    Urabe, Hiroyuki; Kuramoto, Makoto; Nakano, Tomohiro; Kawaharazuka, Atsushi; Makimoto, Toshiki; Horikoshi, Yoshiji

    2015-09-01

    In this paper, we report the effects of surface barrier layers on the characteristics of AlGaAs/GaAs solar cells. The external quantum efficiency (EQE) spectra for AlGaAs barrier samples with different barrier layer AlAs fractions and thickness of the surface barrier layer were measured to increase the solar cell efficiency. The results show that the surface barrier layer is effective to block diffusing photoexcited electrons to the surface while the thicker barrier layer absorbs higher energy photons to generate carriers which recombine at the surface. The optimal surface barrier structure is a 50 nm thick Al0.7Ga0.3As.

  9. Response of silicon solar cell to pulsed laser illumination

    NASA Technical Reports Server (NTRS)

    Willowby, D.; Alexander, D.; Edge, T.; Herren, K.

    1993-01-01

    The response of silicon solar cell(s) to pulsed laser illumination is discussed. The motivation was due to the interest of Earth to space/Moon power beaming applications. When this work began, it was not known if solar cells would respond to laser light with pulse lengths in the nanosecond range and a repetition frequency in the kHz range. This is because the laser pulse would be shorter than the minority carrier lifetime of silicon. A 20-nanosecond (ns) full width half max (FWHM) pulse from an aluminum-gallium/arsenide (Al-Ga-As) diode laser was used to illuminate silicon solar cells at a wavelength of 885 nanometers (nm). Using a high-speed digital oscilloscope, the response of the solar cells to individual pulses across various resistive loads was observed and recorded.

  10. GaAs solar cell development

    NASA Technical Reports Server (NTRS)

    Knechtli, R. C.; Kamath, S.; Loo, R.

    1977-01-01

    The motivation for developing GaAs solar cells is based on their superior efficiency when compared to silicon cells, their lower degradation with increasing temperature, and the expectation for better resistance to space radiation damage. The AMO efficiency of GaAs solar cells was calculated. A key consideration in the HRL technology is the production of GaAs cells of large area (greater than 4 sg cm) at a reasonable cost without sacrificing efficiency. An essential requirement for the successful fabrication of such cells is the ability to grow epitaxially a uniform layer of high quality GaAs (buffer layer) on state-of-the-art GaAs substrates, and to grow on this buffer layer the required than layer of (AlGa)As. A modified infinite melt liquid phase epitaxy (LPE) growth technique is detailed.

  11. Top quark physics

    SciTech Connect

    Ahmadov, A.; Azuelos, G.; Bauer, U.; Belyaev, A.; Berger, E. L.; Sullivan, Z.; Tait, T. M. P.

    2000-03-24

    The top quark, when it was finally discovered at Fermilab in 1995 completed the three-generation structure of the Standard Model (SM) and opened up the new field of top quark physics. Viewed as just another SM quark, the top quark appears to be a rather uninteresting species. Produced predominantly, in hadron-hadron collisions, through strong interactions, it decays rapidly without forming hadrons, and almost exclusively through the single mode t {r_arrow} Wb. The relevant CKM coupling V{sub tb} is already determined by the (three-generation) unitarity of the CKM matrix. Rare decays and CP violation are unmeasurable small in the SM. Yet the top quark is distinguished by its large mass, about 35 times larger than the mass of the next heavy quark, and intriguingly close to the scale of electroweak (EW) symmetry breaking. This unique property raises a number of interesting questions. Is the top quark mass generated by the Higgs mechanism as the SM predicts and is its mass related to the top-Higgs-Yukawa coupling? Or does it play an even more fundamental role in the EW symmetry breaking mechanism? If there are new particles lighter than the top quark, does the top quark decay into them? Could non-SM physics first manifest itself in non-standard couplings of the top quark which show up as anomalies in top quark production and decays? Top quark physics tries to answer these questions. Several properties of the top quark have already been examined at the Tevatron. These include studies of the kinematical properties of top production, the measurements of the top mass, of the top production cross-section, the reconstruction of t{bar t}pairs in the fully hadronic final states, the study of {tau} decays of the top quark, the reconstruction of hadronic decays of the W boson from top decays, the search for flavor changing neutral current decays, the measurement of the W helicity in top decays, and bounds on t{bar t} spin correlations. Most of these measurements are limited by

  12. High-efficiency GaAs/CuInSe2 and AlGaAs/CuInSe2 thin-film tandem solar cells

    NASA Astrophysics Data System (ADS)

    Gale, R. P.; McClelland, R. W.; Dingle, B. D.; Gormley, J. V.; Burgess, R. M.

    Tandem cell throughput has been increased, and quantities of cells that produce tens of watts of power in total were fabricated. An improved efficiency of 23.1 percent AM0/one sun at 28 C has been obtained for 4-sq cm tandem cells. The mechanically stacked tandem cells consist of an n(+):AlGaAs/n:GaAs/p:GaAs/p(+):AlGaAs thin-film top cell and an n(+):CdZnS/p:CuInSe2 thin-film bottom cell. In addition to being highly efficient, the cells are light in weight and radiation resistant. Large numbers of tandem cells have been completed, and individual cell performances exceeded 20 percent for the GaAs top cell and 3 percent for the CuInSe2 (CIS) bottom cell. To attain increased radiation resistance and even higher end-of-life efficiencies, the use of an AlGaAs high-bandgap cell for the upper cell was investigated. Large areas of thin-film AlGaAs were produced using the CLEFT process, and filters to simulate AlGaAs cell structures to be used over the CIS cells were fabricated. CIS cells have been tested under these filters. Results of these measurements indicate that significantly higher efficiencies can be expected from the lower cell in this configuration, and very high end-of-life efficiencies are possible with this approach.

  13. Spherical Tippe Tops

    ERIC Educational Resources Information Center

    Cross, Rod

    2013-01-01

    A tippe top (see Fig. 1) is usually constructed as a truncated sphere with a cylindrical peg on top, as indicated in Fig. 2(a). When spun rapidly on a horizontal surface, a tippe top spins about a vertical axis while rotating slowly about a horizontal axis until the peg touches the surface. At that point, weight is transferred to the peg, the…

  14. Dare We Teach Tops?

    ERIC Educational Resources Information Center

    Featonby, David

    2010-01-01

    "Tops" are mentioned in classical literature and references are even found in the ancient world. For many children a top is one of the first mechanical toys that they play with by themselves, yet a full appreciation of their motion is rare. My hope is that this article will stimulate the reader's interest in tops, will help with the first stages…

  15. Experimental Study of Top Heat Mode Thermosyphon

    NASA Astrophysics Data System (ADS)

    Hirashima, Masao; Kimura, Kenichiro; Utsumi, Yoichi; Kimura, Kenichi; Negishi, Kanji

    The purpose of this study is to develop the top heat mode thermosyphon that is very attractive means, for example, to accumulate directly the summer solar energy into the underground soil for the winter season. In this case, it can exclude the complex piping and mechanical pump to circulate the hot water absorbed the solar energy through the piping system buried in the soil layer. The several ideas concerning the top heat thermosyphon had been proposed, however, there were few reports on the definite experiments. The authors have carried out the experimental study of the top heat mode thermosyphon, with a simple lifting pipe, which could draw the working liquid from the under condenser to the upper evaporator section. The improvement of the main construction parts such as evaporator, lifting pipe, liquid reservoir trap and vapour nozzle have been performed in the present experiment in order to obtain the optimum operation range.

  16. CDF Top Physics

    DOE R&D Accomplishments Database

    Tartarelli, G. F.; CDF Collaboration

    1996-05-01

    The authors present the latest results about top physics obtained by the CDF experiment at the Fermilab Tevatron collider. The data sample used for these analysis (about 110 pb{sup{minus}1}) represents almost the entire statistics collected by CDF during four years (1992--95) of data taking. This large data size has allowed detailed studies of top production and decay properties. The results discussed here include the determination of the top quark mass, the measurement of the production cross section, the study of the kinematics of the top events and a look at top decays.

  17. CDF top physics

    SciTech Connect

    Tartarelli, G.F.; CDF Collaboration

    1996-05-01

    The authors present the latest results about top physics obtained by the CDF experiment at the Fermilab Tevatron collider. The data sample used for these analysis (about 110 pb{sup {minus}1}) represents almost the entire statistics collected by CDF during four years (1992--95) of data taking. This large data size has allowed detailed studies of top production and decay properties. The results discussed here include the determination of the top quark mass, the measurement of the production cross section, the study of the kinematics of the top events and a look at top decays.

  18. AlGaAs ridge laser with 33% wall-plug efficiency at 100 °C based on a design of experiments approach

    NASA Astrophysics Data System (ADS)

    Fecioru, Alin; Boohan, Niall; Justice, John; Gocalinska, Agnieszka; Pelucchi, Emanuele; Gubbins, Mark A.; Mooney, Marcus B.; Corbett, Brian

    2016-04-01

    Upcoming applications for semiconductor lasers present limited thermal dissipation routes demanding the highest efficiency devices at high operating temperatures. This paper reports on a comprehensive design of experiment optimisation for the epitaxial layer structure of AlGaAs based 840 nm lasers for operation at high temperature (100 °C) using Technology Computer-Aided Design software. The waveguide thickness, Al content, doping level, and quantum well thickness were optimised. The resultant design was grown and the fabricated ridge waveguides were optimised for carrier injection and, at 100 °C, the lasers achieve a total power output of 28 mW at a current of 50 mA, a total slope efficiency 0.82 W A-1 with a corresponding wall-plug efficiency of 33%.

  19. Tuning the g-factor of neutral and charged excitons confined to self-assembled (Al,Ga)As shell quantum dots

    SciTech Connect

    Corfdir, P. Van Hattem, B.; Phillips, R. T.; Fontana, Y.; Russo-Averchi, E.; Heiss, M.; Fontcuberta i Morral, A.

    2014-12-01

    We study the neutral exciton (X) and charged exciton (CX) transitions from (Al,Ga)As shell quantum dots located in core-shell nanowires, in the presence of a magnetic field. The g-factors and the diamagnetic coefficients of both the X and the CX depend on the orientation of the field with respect to the nanowire axis. The aspect ratio of the X wavefunction is quantified based on the anisotropy of the diamagnetic coefficient. For specific orientations of the magnetic field, it is possible to cancel the g-factor of the bright states of the X and the CX by means of an inversion of the sign of the hole's g-factor, which is promising for quantum information processing applications.

  20. In-situ analysis of optoelectronic properties of twin boundaries in AlGaAs by polarized cathodoluminescence spectroscopy in a TEM.

    PubMed

    Ohno, Yutaka

    2010-08-01

    Optoelectronic properties of nanoscale twin boundaries (TBs) in indirect-gap AlGaAs layers were studied by polarized cathodoluminescence spectroscopy in a transmission electron microscope. TBs arranged orderly in a short range, i.e. four or more parallel TBs arranged at regular intervals of nanometre length, emitted an intense monochromatic light polarized parallel to the boundaries. The intensity and the photon energy of the light were examined at different temperatures with different electron fluxes, and the origin of the light was discussed based on a twinning superlattice model. According to the study, it was suggested that the photon energy is tunable by controlling the intervals of TBs, without changing the crystal structure and the composition.

  1. Factors influencing doping control and abrupt metallurgical transitions during atmospheric pressure MOVPE growth of AlGaAs and GaAs

    NASA Astrophysics Data System (ADS)

    Roberts, J. S.; Mason, N. J.; Robinson, M.

    1984-09-01

    Atmospheric pressure MOVPE of GaAs and AlGaAs has been investigated using two gas handling systems and a conventional horizontal reactor. Initially a simple source/carrier gas manifold design was assessed but severe retention of reagents in the pipework resulted in poor control of doping and interface abruptness. However, integration of the reagent and carrier gas in a pressure balanced vent/run configuration gave a significant improvement. AlGaAs/GaAs multilayers and n +/n - GaAs transitions have been used to assess the performance of both systems. Abrupt p-type doping transitions using bis-cyclopentadienylmagnesium proved unsuccessful as long doping tails were observed.

  2. The Top Triangle Moose

    NASA Astrophysics Data System (ADS)

    Chivukula, R. S.; Christensen, N. D.; Coleppa, B.; Simmons, E. H.

    2011-01-01

    We introduce a deconstructed model that incorporates both Higgsless and top-color mechanisms. The model alleviates the typical tension in Higgsless models between obtaining the correct top quark mass and keeping Δρ small. It does so by singling out the top quark mass generation as arising from a Yukawa coupling to an effective top-Higgs which develops a small vacuum expectation value, while electroweak symmetry breaking results largely from a Higgsless mechanism. As a result, the heavy partners of the SM fermions can be light enough to be seen at the LHC.

  3. Top Physics at CDF

    SciTech Connect

    Moon, Chang-Seong

    2011-06-01

    We present the recent results of top-quark physics using up to 6 fb{sup -1} of p{bar p} collisions at a center of mass energy of {radical}s = 1.96 TeV analyzed by the CDF collaboration. Thanks to this large data sample, precision top quark measurements are now a reality at the Tevatron. Further, several new physics signals could appear in this large dataset. We will present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.

  4. Training Top 125

    ERIC Educational Resources Information Center

    Training, 2011

    2011-01-01

    Top companies realize how vital training is to their success and continue to invest in it, even in trying times. This article presents "Training" magazine's 11th annual ranking of the top companies with employee-sponsored workforce training and development. First-time No. 1 winner Farmers Insurance puts such a premium on learning that its new…

  5. The Driven Spinning Top

    ERIC Educational Resources Information Center

    Grosu, Ioan; Featonby, David

    2016-01-01

    This driven top is quite a novelty and can, with some trials, be made using the principles outlined here. This new top has many applications in developing both understanding and skills and these are detailed in the article. Depending on reader's available time and motivation they may feel an urge to make one themselves, or simply invest a few…

  6. Training Top 125

    ERIC Educational Resources Information Center

    Training, 2012

    2012-01-01

    The best learning and development organizations support business initiatives tactically "and" help drive strategic change. Verizon did just that, earning it the No. 1 spot for the first time on the Training Top 125. Verizon and the other 2012 Top 125 winners continued to invest in training, collectively dedicating a mean of 4.52 percent of their…

  7. Top search at CDF

    SciTech Connect

    Contreras, M.; The CDF Collaboration

    1991-10-01

    We review top quark searches carried out at CDF with data collected during the 1988--1989 Collider Run. The latest analyses give a lower limit on the top quark mass of 91 GeV/c{sup 2} at the 95% confidence level, assuming Standard Model decays. 8 refs., 6 figs., 1 tab.

  8. Solar sail

    SciTech Connect

    Drexler, K.E.

    1986-09-30

    This patent describes a solar sail propulsion system comprising: solar sail means for intercepting light pressure to produce thrust, the solar sail means being a thin metal film; tension truss means having two ends attached at one end to the solar sail means for transferring the thrust from the solar sail and for preventing gross deformation of the solar sail under light pressure, the solar sail means being a plurality of separate generally two-dimensional pieces joined by springs to the tension truss means; a payload attached to the other end of the tension truss means, the tension truss means comprising a plurality of attachment means for attaching shroud lines to the top of the tension truss means and a plurality of the shroud lines attached to the attachment means at one of their ends and the payload at the other; a plurality of reel means attached to the shroud lines for controllably varying the length of the lines; and a plurality of reflective panel means attached to the sail means for controlling the orientation of the system.

  9. Top physics at CDF

    SciTech Connect

    Hughes, R.E.

    1997-01-01

    We report on top physics results using a 100 pb{sup -1} data sample of p{bar p} collisions at {radical}s = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). We have identified top signals in a variety of decay channels, and used these channels to extract a measurement of the top mass and production cross section. A subset of the data (67 pb{sup -1}) is used to determine M{sub top} = 176 {+-} 8(stat) {+-} 10(syst) and {sigma}(tt) = 7.6 {sub -2.0}{sup +2.4} pb. We present studies of the kinematics of t{bar t} events and extract the first direct measurement of V{sub tb}. Finally, we indicate prospects for future study of top physics at the Tevatron.

  10. Top quark mass measurement

    SciTech Connect

    Maki, Tuula

    2008-03-18

    The top quark is the heaviest elementary particle. Its mass is one of the fundamental parameters of the standard model of particle physics, and an important input to precision electroweak tests. This thesis describes three measurements of the top-quark mass in the dilepton decay channel. The dilepton events have two neutrinos in the final state; neutrinos are weakly interacting particles that cannot be detected with a multipurpose experiment. Therefore, the signal of dilepton events consists of a large amount of missing energy and momentum carried off by the neutrinos. The top-quark mass is reconstructed for each event by assuming an additional constraint from a top mass independent distribution. Template distributions are constructed from simulated samples of signal and background events, and parametrized to form continuous probability density functions. The final top-quark mass is derived using a likelihood fit to compare the reconstructed top mass distribution from data to the parametrized templates. One of the analyses uses a novel technique to add top mass information from the observed number of events by including a cross-section-constraint in the likelihood function. All measurements use data samples collected by the CDF II detector.

  11. The effects of concentrated system on the electrical parameters of GaInP/GaAs solar cell

    NASA Astrophysics Data System (ADS)

    Kınacı, Barış

    2017-02-01

    III-V concentrator solar cells are suitable materials in order to reduce the cost of photovoltaic electricity. By using Fresnel lens in concentrating photovoltaic technology is an effective way to entirely use the sunlight. In the present study, the research on the efficiency analysis of the GaInP/GaAs concentrated solar cell structure with AlGaAs tunnel junction was performed. The electrical output parameters of this structure were determined by concentrated system with Fresnel lens. The current-voltage measurements of concentrated solar cell were carried out at room temperature under both dark and air mass 1.5 global radiations. The parameters of GaInP/GaAs concentrated solar cell at 1 Sun and at 32 Suns are compared. It is obtained that the integration of the concentrated system on the solar cell structure improves the device performance by ≈7.5%.

  12. Top physics at CDF

    SciTech Connect

    Palencia, Enrique; /Cantabria Inst. of Phys.

    2006-06-01

    The top quark is the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the Standard Model (SM). This article focuses on the latest top physics results from CDF based on 320-750 pb{sup -1} of p{bar p} collision data at {radical}s = 1.96 TeV. The t{bar t} cross section and the top mass have been measured in different decay channels and using different methods. They have also searched for massive t{bar t} resonances.

  13. Top quark mass measurements

    SciTech Connect

    Hill, Christopher S.; /UC, Santa Barbara

    2004-12-01

    The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.

  14. Top physics: CDF results

    SciTech Connect

    K. Bloom

    2004-06-23

    The top quark plays an important role in the grand scheme of particle physics, and is also interesting on its own merits. We present recent results from CDF on top-quark physics based on 100-200 pb{sup -1} of p{bar p} collision data. We have measured the t{bar t} cross section in different decay modes using several different techniques, and are beginning our studies of top-quark properties. New analyses for this conference include a measurement of {sigma}{sub t{bar t}} in the lepton-plus-jets channel using a neural net to distinguish signal and background events, and measurements of top-quark branching fractions.

  15. Top quark properties

    SciTech Connect

    Hong, Ziqing

    2014-10-31

    The top quark physics has entered the precision era. The CDF and D0 collaborations are finalizing their legacy results of the properties of the top quark after the shutdown of the Fermilab Tevatron three years ago. The ATLAS and CMS collaborations have been publishing results from the LHC Run I with 7 TeV and 8 TeV proton-proton collisions, with many more forthcoming. We present a selection of recent results produced by the Tevatron and LHC experiments.

  16. Cleaner for Solar-Collector Covers

    NASA Technical Reports Server (NTRS)

    Frickland, P. O.; Cleland, E. L.

    1983-01-01

    Simple self-contained cleaning system proposed for solar collectors or solar-collector protective domes. Perforated transparent plastic cap attached to top of protective dome in heliostat solar-energy collection system distributes cleaning fluid over surface of dome without blocking significant fraction of solar radiation.

  17. Kernel mucking in top

    SciTech Connect

    LeFebvre, W.

    1994-08-01

    For many years, the popular program top has aided system administrations in examination of process resource usage on their machines. Yet few are familiar with the techniques involved in obtaining this information. Most of what is displayed by top is available only in the dark recesses of kernel memory. Extracting this information requires familiarity not only with how bytes are read from the kernel, but also what data needs to be read. The wide variety of systems and variants of the Unix operating system in today`s marketplace makes writing such a program very challenging. This paper explores the tremendous diversity in kernel information across the many platforms and the solutions employed by top to achieve and maintain ease of portability in the presence of such divergent systems.

  18. Top-ophilia

    SciTech Connect

    Quigg, Chris; /Fermilab

    2008-01-01

    Almost from the moment in June 1977 when the discovery of the Upsilon resonance revealed the existence of what we now call the bottom quark, physicists began searching for its partner. Through the years, as we established the electric charge and weak isospin of the b-quark, and detected the virtual influence of its mate, it became clear that the top quark must exist. Exactly at what mass, we couldn't say, but we knew just how top events would look. We also knew that top events would be rare--if the Tevatron could make them at all--and that picking out the events would pose a real challenge for the experimenters and their detectors.

  19. Direct detection optical intersatellite link at 220 Mbps using AlGaAs laser diode and silicon APD with 4-ary PPM signaling

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Davidson, Frederic M.

    1990-01-01

    A newly developed 220 Mbps free-space 4-ary pulse position modulation (PPM) direct detection optical communication system is described. High speed GaAs integrated circuits were used to construct the PPM encoder and receiver electronic circuits. Both PPM slot and word timing recovery were provided in the PPM receiver. The optical transmitter consisted of an AlGaAs laser diode (Mitsubishi ML5702A, lambda=821nm) and a high speed driver unit. The photodetector consisted of a silicon avalanche photodiode (APD) (RCA30902S) preceded by an optical interference filter (delta lambda=10nm). Preliminary tests showed that the self-synchronized PPM receiver could achieve a receiver bit error rate of less than 10(exp -6) at 25 nW average received optical signal power or 360 photons per transmitted information bit. The relatively poor receiver sensitivity was believed to be caused by the insufficient electronic bandwidth of the APD preamplifier and the poor linearity of the preamplifier high frequency response.

  20. High-power low-threshold graded-index separate confinement heterostructure AlGaAs single quantum well lasers on Si substrates

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Hoon; Lang, Robert J.; Radhakrishnan, Gouri; Katz, Joseph; Narayanan, Authi A.

    1989-01-01

    A high-power low-threshold graded-index separate confinement heterostructure AlGaAs single quantum well laser on Si substrates has been demonstrated for the first time by a hybrid growth of migration-enhanced molecular beam epitaxy followed by metalorganic vapor phase epitaxy. The quantum well laser showed an output power of more than 400 mW per facet under pulsed conditions. A room-temperature threshold current of 300 mA was obtained with a differential quantum efficiency of 40 percent without facet coating. The threshold current density was 550 A/sq cm for a cavity length of 500 microns. These results show the highest peak power reported to date for low-threshold lasers on Si substrates. The full width at half maximum of the far-field pattern parallel to the junction was 6 deg. Threshold current densities as low as 250 A/sq cm were obtained for lasers on GaAs substrates.

  1. Performance of AlGaAs, GaAs and InGaAs cells after 1 MeV electron irradiation

    NASA Technical Reports Server (NTRS)

    Curtis, Henry B.; Hart, Russell E., Jr.

    1987-01-01

    Electron irradiations were made on three different types of III-V cells. AlGaAs, GaAs, and InGaAs cells with bandgaps of approximately 1.72, 1.43, and 1.1 eV, respectively, were tested. All of the cells were concentrator cells and performance data from one sun to beyond 100x AMO were taken. The total 1 MeV electron fluence was 3 times 10 to the 15th power e/square cm with data taken at several intermediate fluences. Cell performance is presented as a function of electron fluence for various concentration ratios and two different temperatures (25 and 80 C). Since these three cell types are potential candidates for the individual cells in a cascade structure, it is possible to calculate the loss in performance of cascade cells under 1 MeV irradiation. Data are presented which show the calculated performance of both series-connected and separately connected cascade cells.

  2. TOPS optical correlation program

    NASA Astrophysics Data System (ADS)

    Lindell, Scott D.

    1993-09-01

    Martin Marietta is conducting a TOPS optical correlation program in which several algorithms and four optical correlators involving two spatial light modulator technologies will be developed and tested. The program will culminate in 1994 with an automatic target recognition flight demonstration using a UH-1 helicopter flying a Fiber Optic Guide Missile (FOG-M) mission profile. The flight demonstration will be conducted by US Army Missile Command (MICOM) and Martin Marietta and will involve detecting, locating and tracking a M60A2 tank positioned among an array of five vehicle types. Current status of the TOPS program will be given.

  3. TOPping off meiosis.

    PubMed

    Haber, James E

    2015-02-19

    Double-strand breaks (DSBs) threaten chromosome integrity. The most accurate repair of DSBs is by homologous recombination (HR), catalyzed by recombination proteins such as Rad51. Three papers in this issue of Molecular Cell (Fasching et al., 2015; Kaur et al., 2015; Tang et al., 2015) now reveal the role of three of these proteins in budding yeast: Sgs1 (BLM homolog), Top3 (TOPIIIα homolog), and Rmi1. They demonstrate several steps where all three proteins act together, and find additional functions of the Top3-Rmi1 subcomplex that are critical for the completion of meiosis.

  4. A new high volume MOVPE reactor for III-V solar cells

    SciTech Connect

    Ermer, J.; Vijaykumar, P.S.; Chang, K.I.; Lillington, D.R.; Cavicchi, B.T.; Woelk, E.; Strauch, G.; Schmitz, D.; Jurgensen, H.

    1994-12-31

    A new MOVPE reactor is described which allows cost effective manufacturing of GaAs/Ge solar cells. The reactor, which has a batch size in excess of 0.25 m{sup 2}, was co-developed by Spectrolab and Aixtron Semiconductor Technologies over a two year time frame and was installed at Spectrolab in late 1993. Manufacturing readiness data on large area single junction GaAs/Ge solar cells show that the thickness and compositional uniformity of GaAs and AlGaAs layers grown in the system are {+-} 3%, and {+-} 1.5% respectively. There is excellent correlation between empirical data and simulations performed during the initial reactor development phase. The minimum average AM0, 28 C efficiencies of 7 mil and 5.5 mil single junction GaAs/Ge solar cells, recently manufactured from material grown on this system, are over 18.5%.

  5. Towards Other Planetary Systems (TOPS): A technology needs identification workshop

    NASA Technical Reports Server (NTRS)

    Black, David C.; Nishioka, Kenji

    1991-01-01

    The workshop identified a strong commonality between the technology needs for NASA's TOPS program and the technology needs that were identified for NASA's astrophysics program through its Astrotech 21 survey. The workshop encourages NASA to have the Solar System Exploration and Astrophysics Div. work cooperatively to share in technology studies that are common to both programs, rather than to conduct independent studies. It was also clear, however, that there are technology needs specific to TOPS, and these should be pursued by the Solar System Exploration Div. There are two technology areas that appear to be particularly critical to realizing the ultimate performance that is being sought under the TOPS program, these areas are metrology and optics. The former is critical in calibration and verification of instrument performance, while the latter is needed to provide optical systems of sufficient quality to conduct a search for and characterization of other planetary systems at the more extreme levels of performance identified in TOPS program.

  6. Top quark physics: Future measurements

    SciTech Connect

    Frey, R.; Vejcik, S.; Berger, E.L.

    1997-04-04

    The authors discuss the study of the top quark at future experiments and machines. Top`s large mass makes it a unique probe of physics at the natural electroweak scale. They emphasize measurements of the top quark`s mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

  7. Ten Top Tech Trends

    ERIC Educational Resources Information Center

    McLester, Susan

    2008-01-01

    In this article, the author discusses the major technical issues, products, and practices of the day. The top ten tech trends are listed and discussed. These include: (1) data mining; (2) cyberbullying; (3) 21st century skills; (4) digital content; (5) learning at leisure; (6) personal responders; (7) mobile tools; (8) bandwidth; (9) open-source…

  8. Choosing a Top Ten.

    ERIC Educational Resources Information Center

    IUCN Bulletin, 1984

    1984-01-01

    Presents an annotated list of 34 animals and 32 plants which are candidates for a list of the top 10 endangered species. Also presents the criteria used to formulate these lists. They include the conservation value (urgency prominance, biological value) and operational considerations (such as cost factors) for each species. (JN)

  9. Tension solar mirror

    SciTech Connect

    Russo, W.P.

    1986-09-02

    A solar collector is described comprising a central tower having a solar receiver thereon; tension towers positioned concentrically about the central tower;a rigid inner ring disposed about the central tower and sized to permit vertical movement relative to the central tower; cables extending between the inner ring and the tops of each of the tension towers; and a reflectively-coated sheet of flexible material attached to the upper surface of the cables; whereby the action of gravity on the cables and the sheet form a concave reflector for focusing solar energy onto the solar receiver.

  10. Exploring Venus by Solar Airplane

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    2001-01-01

    A solar-powered airplane is proposed to explore the atmospheric environment of Venus. Venus has several advantages for a solar airplane. At the top of the cloud level, the solar intensity is comparable to or greater than terrestrial solar intensities. The Earthlike atmospheric pressure means that the power required for flight is lower for Venus than that of Mars, and the slow rotation of Venus allows an airplane to be designed for continuous sunlight, with no energy storage needed for night-time flight. These factors mean that Venus is perhaps the easiest planet in the solar system for flight of a long-duration solar airplane.

  11. Quantum-well lasers for direct solar photopumping

    NASA Astrophysics Data System (ADS)

    Unnikrishnan, Sreenath; Anderson, Neal G.

    1993-09-01

    Semiconductor lasers directly photopumped by focused sunlight may be viable sources of coherent light for intersatellite communications and other low-power spaceborne applications. In this work, we theoretically explore the possibility of realizing such devices. We specifically assess solar pumped operation of separate-confinement-quantum-well heterostructure (SCQWH) lasers based on InGaAs, GaAs, and AlGaAs, as fabrication technology for these lasers is mature and they can operate at very low thresholds. We develop a model for step-index single-well SCQWH lasers photopumped by sunlight, examine how threshold solar photoexcitation intensities (or solar magnification requirements) depend upon material and structure parameters, design optimum structures for solar-pumped operation, and identify design trade offs. Our results suggest that laser action should be possible in properly designed structures at readily achievable solar concentrations (103-104 suns under air-mass-zero conditions), and that optimum designs for solar-pumped SCQWH lasers differ significantly from those for analogous current injection devices.

  12. Four tops for LHC

    NASA Astrophysics Data System (ADS)

    Alvarez, Ezequiel; Faroughy, Darius A.; Kamenik, Jernej F.; Morales, Roberto; Szynkman, Alejandro

    2017-02-01

    We design a search strategy for the Standard Model t t bar t t bar production at the LHC in the same-sign dilepton and trilepton channels. We study different signal features and, given the small expected number of signal events, we scrutinize in detail all reducible and irreducible backgrounds. Our analysis shows that by imposing a basic set of jet and lepton selection criteria, the SM pp → t t bar t t bar process could be evidenced in the near future, within Run-II, when combining both multi-lepton search channels. We argue that this search strategy should also be used as a guideline to test New Physics coupling predominantly to top-quarks. In particular, we show that a non-resonant New Physics enhancement in the four-top final state would be detectable through this search strategy. We study two top-philic simplified models of this kind, a neutral scalar boson and a Z‧, and present current and future exclusion limits on their mass and couplings.

  13. 22. Top Lateral Bracing & Top Chord, Vertical Tension Member ...

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

    22. Top Lateral Bracing & Top Chord, Vertical Tension Member 6, end Vertical Compression Members 5 & 4; South Swing Span; looking N. - Pacific Shortline Bridge, U.S. Route 20,spanning Missouri River, Sioux City, Woodbury County, IA

  14. Cloud top entrainment instability and cloud top distributions

    NASA Technical Reports Server (NTRS)

    Boers, Reinout; Spinhirne, James D.

    1990-01-01

    Classical cloud-top entrainment instability condition formulation is discussed. A saturation point diagram is used to investigate the details of mixing in cases where the cloud-top entrainment instability criterion is satisfied.

  15. 7. DETAIL VIEW OF TOP CHORD AND TOP CHORD CONNECTION ...

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

    7. DETAIL VIEW OF TOP CHORD AND TOP CHORD CONNECTION - Springfield-Des Arc Bridge, Spanning North Branch of Cadron Creek at Old Springfield-Des Arc Road (County Road 222), Springfield, Conway County, AR

  16. Top quark physics at CDF

    SciTech Connect

    Nielsen, Jason

    2004-04-30

    The existence of the top quark, discovered by CDF and D0 in 1995, has been re-established in the burgeoning dataset being collected in Run 2 of the Tevatron at Fermilab. Results from CDF on the top quark production cross section and top quark mass are consistent with the Standard Model expectations. The well-characterized top data samples will make it possible in the future to probe further for new physics in the top quark sector. This report summarizes recent CDF top quark physics results.

  17. Light-Emitting Devices Based on Top-down Fabricated GaAs Quantum Nanodisks

    PubMed Central

    Higo, Akio; Kiba, Takayuki; Tamura, Yosuke; Thomas, Cedric; Takayama, Junichi; Wang, Yunpeng; Sodabanlu, Hassanet; Sugiyama, Masakazu; Nakano, Yoshiaki; Yamashita, Ichiro; Murayama, Akihiro; Samukawa, Seiji

    2015-01-01

    Quantum dots photonic devices based on the III–V compound semiconductor technology offer low power consumption, temperature stability, and high-speed modulation. We fabricated GaAs nanodisks (NDs) of sub-20-nm diameters by a top-down process using a biotemplate and neutral beam etching (NBE). The GaAs NDs were embedded in an AlGaAs barrier regrown by metalorganic vapor phase epitaxy (MOVPE). The temperature dependence of photoluminescence emission energies and the transient behavior were strongly affected by the quantum confinement effects of the embedded NDs. Therefore, the quantum levels of the NDs may be tuned by controlling their dimensions. We combined NBE and MOVPE in a high-throughput process compatible with industrial production systems to produce GaAs NDs with tunable optical characteristics. ND light emitting diode exhibited a narrow spectral width of 38 nm of high-intensity emission as a result of small deviation of ND sizes and superior crystallographic quality of the etched GaAs/AlGaAs layer. PMID:25792119

  18. New approaches for high-efficiency solar cells. Final report

    SciTech Connect

    Bedair, S M; El-Masry, N A

    1997-12-01

    This report summarizes the activities carried out in this subcontract. These activities cover, first the atomic layer epitaxy (ALE) growth of GaAs, AlGaAs and InGaP at fairly low growth temperatures. This was followed by using ALE to achieve high levels of doping both n-type and p-type required for tunnel junctions (Tj) in the cascade solar cell structures. Then the authors studied the properties of AlGaAs/InGaP and AlGaAs/GaAs tunnel junctions and their performances at different growth conditions. This is followed by the use of these tunnel junctions in stacked solar cell structures. The effect of these tunnel junctions on the performance of stacked solar cells was studied at different temperatures and different solar fluences. Finally, the authors studied the effect of different types of black surface fields (BSF), both p/n and n/p GaInP solar cell structures, and their potential for window layer applications. Parts of these activities were carried in close cooperation with Dr. Mike Timmons of the Research Triangle Institute.

  19. Performance of antireflecting coating-AlGaAs window layer coupling for terrestrial concentrator GaAs solar cells

    SciTech Connect

    Valle, C.A. del; Alcaraz, M.F.

    1997-09-01

    In this paper, the authors present the performance of optical coating systems coupled with AlGaAs window layers over GaAs solar cells. Single, double, and triple antireflecting coatings and window layers with constant and graded aluminum content are considered. Comparison between constant and graded window layers is established. To better represent reality, practical factors such as absorption of materials even for antireflecting coatings and the oxidation at window layer surface due to its high aluminum content are also included in the calculations. The design criteria to determine the optimum thickness of each layer is the achievement of maximum photogenerated current density. For this purpose and to account for terrestrial concentrators GaAs solar cells, the inclusion of direct terrestrial solar spectrum together with the internal spectral response of the device are taken into account. Finally, the best antireflecting coating/AlGaAs window layer couplings for different cases are presented.

  20. Top quark physics: Future Measurements

    SciTech Connect

    Frey, Raymond; Gerdes, David; Jaros, John; Vejcik, Steve; Berger, Edmond L.; Chivukula, R. Sekhar; Cuypers, Frank; Drell, Persis S.; Fero, Michael; Hadley, Nicholas; Han, Tao; Heinson, Ann P.; Knuteson, Bruce; Larios, Francisco; Miettinen, Hannu; Orr, Lynne H.; Peskin, Michael E.; Rizzo, Thomas; Sarid, Uri; Schmidt, Carl; Stelzer, Tim; Sullivan, Zack

    1996-12-31

    We discuss the study of the top quark at future experiments and machines. Top's large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark's mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

  1. Top physics results at CDF

    SciTech Connect

    Vickey, Trevor; /Illinois U., Urbana

    2005-05-01

    The most recent results on top quark physics at CDF are reported. Measurements of cross-section and mass are presented, and the status of single top quark production searches are discussed. The results obtained from probing various top quark properties are also presented.

  2. Curly Top Disease of Tomato

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Curly top disease, caused by viruses in the genus, Curtovirus, has impacted western US agriculture for over a century; and is a significant threat to tomato production. The two most abundant curtovirus species today are Beet severe curly top virus (BSCTV) and Beet mild curly top virus (BMCTV) but ot...

  3. Solar collection

    NASA Astrophysics Data System (ADS)

    Cole, S. I.

    1984-08-01

    Solar dishes, photovoltaics, passive solar building and solar hot water systems, Trombe walls, hot air panels, hybrid solar heating systems, solar grain dryers, solar greenhouses, solar hot water worhshops, and solar workshops are discussed. These solar technologies are applied to residential situations.

  4. CDF results on top

    SciTech Connect

    Beretvas, A.; CDF Collaboration

    1995-08-01

    CDF has established the existence of the top quark. Results from p{anti p} collisions at {radical}s = 1.8 TeV are presented. In the dilepton final state the authors found seven events with a background of 1.3 {+-} 0.3. In the e, {mu} + {nu} + jets channel with a b identified via a secondary vertex detector (SVX), they found twenty one events with a background of 5.5 {+-} 1.8. They measure the top quark mass to be 176 {+-} 8 (stat) {+-} 10 (syst) GeV/c{sup 2}, and the t{anti t} production cross section to be 7.6{sub {minus}2.0}{sup +2.4} pb. The integrated luminosity for the results presented in this talk is 67 pb{sup {minus}1}. The CDF detector needs to be upgraded for the next run. The integrated luminosity for the next run is expected to be more than 1,000 pb{sup {minus}1}.

  5. Top quark mass measurements

    SciTech Connect

    L. Cerrito

    2004-07-16

    Preliminary results on the measurement of the top quark mass at the Tevatron Collider are presented. In the dilepton decay channel, the CDF Collaboration measures m{sub t} = 175.0{sub -16.9}{sup +17.4}(stat.){+-}8.4(syst.) GeV/c{sup 2}, using a sample of {approx} 126 pb{sup -1} of proton-antiproton collision data at {radical}s = 1.96 TeV (Run II). In the lepton plus jets channel, the CDF Collaboration measures 177.5{sub -9.4}{sup +12.7}(stat.) {+-} 7.1(syst.) GeV/c{sup 2}, using a sample of {approx} 102 pb{sup -1} at {radical}s = 1.96 TeV. The D0 Collaboration has newly applied a likelihood technique to improve the analysis of {approx} 125 pb{sup -1} of proton-antiproton collisions at {radical}s = 1.8 TeV (Run I), with the result: m{sub t} = 180.1 {+-} 3.6(stat.) {+-}3.9(syst.) GeV/c{sup 2}. The latter is combined with all the measurements based on the data collected in Run I to yield the most recent and comprehensive experimental determination of the top quark mass: m{sub t} = 178.0 {+-} 2.7(stat.) {+-} 3.3(syst.) GeV/c{sup 2}.

  6. Top properties at the Tevatron

    SciTech Connect

    Chiarelli, G.; The CDF Collaboration

    1997-05-01

    We present the latest results associated with top properties at the Tevatron. The large data set collected in four years of running has allowed, after top discovery, the study of various top properties. The results presented here include the measurement of the CKM matrix element {vert_bar}V{sub if}{vert_bar}, the search for top FCNC, the study of properties of W in t decays and the search for heavy states decaying to tt pairs. Future measurements in top physics at the Tevatron are briefly discussed.

  7. Top quark pair production and top quark properties at CDF

    SciTech Connect

    Moon, Chang-Seong

    2016-06-02

    We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $|V_{tb}|$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($A_{FB}$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $t\\bar t$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.

  8. Top quark physics

    SciTech Connect

    Menzione, A.

    1995-10-01

    Most of the material presented in this report, comes from contributions to the parallel session PL20 of this conference. We summarise the experimental results of direct production of Top quarks, coming from the CDF and C0 Collaborations at Fermilab, and compare these results to what one expects within current theoretical understanding. Particular attention is given to new results such as all hadronic modes of t{bar t} decay. As far as the mass is concerned, a comparison is made with precision measurements of related quantities, coming from LEP and other experiments. An attempt is made to look at the medium-term future and understand which variables and with what accuracy one can measure them with increased integrated luminosity.

  9. Top-Higgs and top-pion phenomenology in the top triangle moose model

    NASA Astrophysics Data System (ADS)

    Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam

    2011-03-01

    We discuss the deconstructed version of a topcolor-assisted technicolor model wherein the mechanism of top quark mass generation is separated from the rest of electroweak symmetry breaking. The minimal deconstructed version of this scenario is a “triangle moose” model, where the top quark gets its mass from coupling to a top-Higgs field, while the gauge boson masses are generated from a Higgsless sector. The spectrum of the model includes scalar (top-Higgs) and pseudoscalar (top-pion) states. In this paper, we study the properties of these particles, discuss their production mechanisms and decay modes, and suggest how best to search for them at the LHC.

  10. Top-Higgs and top-pion phenomenology in the top triangle moose model

    SciTech Connect

    Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam

    2011-03-01

    We discuss the deconstructed version of a topcolor-assisted technicolor model wherein the mechanism of top quark mass generation is separated from the rest of electroweak symmetry breaking. The minimal deconstructed version of this scenario is a ''triangle moose'' model, where the top quark gets its mass from coupling to a top-Higgs field, while the gauge boson masses are generated from a Higgsless sector. The spectrum of the model includes scalar (top-Higgs) and pseudoscalar (top-pion) states. In this paper, we study the properties of these particles, discuss their production mechanisms and decay modes, and suggest how best to search for them at the LHC.

  11. Top physics results from CDF

    SciTech Connect

    Gomez, Gervasio; /Cantabria Inst. of Phys.

    2005-05-01

    The top quark is by far the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the Standard Model. They present recent top physics results from CDF based on 160-320 pb{sup -1} of p{bar p} collision data at {radical}s = 1.96 TeV. The t{bar t} cross section and the top mass have been measured in different decay channels and using different methods. they have searched for evidence of single top production, setting upper limits on its production rate. Other results shown in this conference include studies of the polarization of W bosons from top decays, a search for charged Higgs decaying from top, and a search for additional heavy t' quarks.

  12. Solar astronomy

    NASA Technical Reports Server (NTRS)

    Rosner, Robert; Noyes, Robert; Antiochos, Spiro K.; Canfield, Richard C.; Chupp, Edward L.; Deming, Drake; Doschek, George A.; Dulk, George A.; Foukal, Peter V.; Gilliland, Ronald L.

    1991-01-01

    An overview is given of modern solar physics. Topics covered include the solar interior, the solar surface, the solar atmosphere, the Large Earth-based Solar Telescope (LEST), the Orbiting Solar Laboratory, the High Energy Solar Physics mission, the Space Exploration Initiative, solar-terrestrial physics, and adaptive optics. Policy and related programmatic recommendations are given for university research and education, facilitating solar research, and integrated support for solar research.

  13. Dark matter on top

    SciTech Connect

    Gómez, M.A.; Jackson, C.B.; Shaughnessy, G. E-mail: chris@uta.edu

    2014-12-01

    We consider a simplified model of fermionic dark matter which couples exclusively to the right-handed top quark via a renormalizable interaction with a color-charged scalar. We first compute the relic abundance of this type of dark matter and investigate constraints placed on the model parameter space by the latest direct detection data. We also perform a detailed analysis for the production of dark matter at the LHC for this model. We find several kinematic variables that allow for a clean signal extraction and we show that the parameter space of this model will be well probed during LHC Run-II. Finally, we investigate the possibility of detecting this type of dark matter via its annihilations into gamma rays. We compute the continuum and the line emission (which includes a possible ''Higgs in Space!'' line) and its possible discovery by future gamma-ray telescopes. We find that the annihilation spectrum has distinctive features which may distinguish it from other models.

  14. 4. DETAIL VIEW OF TOP CHORD AND TOP CHORD CONNECTIONS ...

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

    4. DETAIL VIEW OF TOP CHORD AND TOP CHORD CONNECTIONS NEAR NORTH CORNER OF BRIDGE, LOOKING WEST - Springfield-Des Arc Bridge, Spanning North Branch of Cadron Creek at Old Springfield-Des Arc Road (County Road 222), Springfield, Conway County, AR

  15. Properties of the Top Quark

    SciTech Connect

    Déliot, Frédéric; Hadley, Nicholas; Parke, Stephen; Schwarz, Tom

    2014-10-01

    The top quark is the heaviest known elementary particle, and it is often seen as a window to search for new physics processes in particle physics. A large program to study the top-quark properties has been performed both at the Tevatron and LHC colliders by the D0, CDF, ATLAS and CMS experiments. The most recent results are discussed in this article.

  16. A new high-efficiency GaAs solar cell structure using a heterostructure back-surface field

    NASA Technical Reports Server (NTRS)

    Gale, R. P.; Fan, J. C. C.; Turner, G. W.; Chapman, R. L.

    1984-01-01

    Shallow-homojunction GaAs solar cells are fabricated with a back-surface field (BSF) produced by a GaAs/Al(0.2)Ga(0.8)As heterostructure. These cells exhibit higher open-circuit voltages and conversion efficiencies than control cells made with a p-GaAs/p(+)-GaAs BSF. Conversion efficiencies of over 22 percent (AM1, total area) have been obtained with this new structure. The use of a higher bandgap material below the active region not only provides an enhanced BSF but will also permit the implementation of two solar-cell designs: a GaAs cell with a back-surface reflector and an AlGaAs cell that can be used as the upper cell in tandem configurations.

  17. Naturalness from a composite top?

    NASA Astrophysics Data System (ADS)

    Pierce, Aaron; Zhao, Yue

    2017-01-01

    We consider a theory with composite top quarks but an elementary Higgs boson. The hierarchy problem can be solved by supplementing TeV scale top compositeness with either supersymmetry or Higgs compositeness appearing at the multi-TeV scale. The Higgs boson couples to uncolored partons within the top quark. We study how this approach can give rise to a novel screening effect that suppresses production of the colored top partners at the LHC. Strong constraints arise from Z to overline{b}b , as well potentially from flavor physics. Independent of flavor considerations, current constraints imply a compositeness scale ≳ TeV; this implies that the model is likely tuned at the percent level. Four top quark production at the LHC is a smoking-gun probe of this scenario. New CP violation in D meson mixing is also possible.

  18. Wave Engine Topping Cycle Assessment

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.

    1996-01-01

    The performance benefits derived by topping a gas turbine engine with a wave engine are assessed. The wave engine is a wave rotor that produces shaft power by exploiting gas dynamic energy exchange and flow turning. The wave engine is added to the baseline turboshaft engine while keeping high-pressure-turbine inlet conditions, compressor pressure ratio, engine mass flow rate, and cooling flow fractions fixed. Related work has focused on topping with pressure-exchangers (i.e., wave rotors that provide pressure gain with zero net shaft power output); however, more energy can be added to a wave-engine-topped cycle leading to greater engine specific-power-enhancement The energy addition occurs at a lower pressure in the wave-engine-topped cycle; thus the specific-fuel-consumption-enhancement effected by ideal wave engine topping is slightly lower than that effected by ideal pressure-exchanger topping. At a component level, however, flow turning affords the wave engine a degree-of-freedom relative to the pressure-exchanger that enables a more efficient match with the baseline engine. In some cases, therefore, the SFC-enhancement by wave engine topping is greater than that by pressure-exchanger topping. An ideal wave-rotor-characteristic is used to identify key wave engine design parameters and to contrast the wave engine and pressure-exchanger topping approaches. An aerodynamic design procedure is described in which wave engine design-point performance levels are computed using a one-dimensional wave rotor model. Wave engines using various wave cycles are considered including two-port cycles with on-rotor combustion (valved-combustors) and reverse-flow and through-flow four-port cycles with heat addition in conventional burners. A through-flow wave cycle design with symmetric blading is used to assess engine performance benefits. The wave-engine-topped turboshaft engine produces 16% more power than does a pressure-exchanger-topped engine under the specified topping

  19. Status of the top quark: Top production cross section and top properties

    SciTech Connect

    Boisvert, V.; /Rochester U.

    2006-08-01

    This report describes the latest cross section and property measurements associated with the top quark at the Tevatron Run II. The largest data sample used is 760 pb{sup -1} of integrated luminosity. Due to its large mass, the top quark might be involved in the process of electroweak symmetry breaking, making it a useful probe for signs of new physics.

  20. Properties of the top quark

    SciTech Connect

    Jung, A. W.

    2014-09-24

    Recent measurements of top-quark properties at the LHC and the Tevatron are presented. Most recent measurements of the top quark mass have been carried out by CMS using $19.7/$fb of $\\sqrt{s} = 8$ TeV data including the study of the dependence on event kinematics. ATLAS uses the full Run I data at $\\sqrt{s} = 7$ TeV for a "3D" measurement that significantly reduces systematic uncertainties. D0 employs the full Run II data using the matrix element method to measure the top quark mass with significantly reduced systematic uncertainties. Many different measurements of the top quark exist to date and the most precise ones per decay channel per experiment have been combined into the first world combination with a relative precision of 0.44%. Latest updates of measurements of production asymmetries include the measurement of the \\ttbar production asymmetry by D0 employing the full Run II data set, by CMS and ATLAS (including the polarization of the top quark) employing both the full data set at $\\sqrt{s} = 7$ TeV. CMS uses the full $\\sqrt{s} = 8$ TeV data to measure the top quark polarization in single top production, the ratio ${\\cal R}$ of the branching fractions ${\\cal B}(t \\rightarrow Wb) / {\\cal B}(t \\rightarrow Wq)$ and to search for flavor changing neutral currents. The results from all these measurements agree well with their respective Standard Model expectation.

  1. Nanoscale optimization of quantum dot solar sells

    NASA Astrophysics Data System (ADS)

    Li, Yanshu; Sergeev, Andrei; Vagidov, Nizami; Mitin, Vladimir; Sablon, Kimberly; State Univ of NY-Buffalo Team; Army Research Laboratory Team

    2015-03-01

    Quantum dots (QDs) offer possibilities for nanoscale control of photoelectron processes via engineering the band structure and potential profile. Nanoscale potential profile (potential barriers) and nanoscale band engineering (AlGaAs atomically thin barriers) effectively suppress the photoelectron capture to QDs. QDs also increase conversion efficiency of the above-bandgap photons due to extraction of electrons from QDs via Coulomb interaction with hot electrons that excited by high-energy photons. To study the effects of the band structure engineering and nanoscale potential barriers on the photovoltaic performance we fabricated 3- μm base GaAs devices with various InAs quantum dot media and selective doping. All quantum dot devices show improvement in conversion efficiency compared with the reference cell. Quantum efficiency measurements allow us to associate the spectral characteristics of photoresponse enhancement with nanoscale structure of QD media. The dark current analysis provides valuable information about recombination in QD solar cells. The two-diode model well fit the scope of data and recovers the measured open circuit voltage.

  2. Saltless solar pond

    NASA Technical Reports Server (NTRS)

    Lin, E. I. H. (Inventor)

    1984-01-01

    A solar pond adapted for efficiently trapping and storing radiant solar energy without the use of a salt concentration gradient in the pond is disclosed. A body of water which may be fresh, saline, relatively clear or turbid, is substantially covered by a plurality of floating honeycomb panels. The honeycomb panels are made of a material such as glass which is pervious to short wave solar radiation but impervious to infrared radiation. Each honeycomb panel includes a multitude of honeycomb cells. The honeycomb panels are divided into the elongated honeycomb cells by a multitude of intermediate plates disposed between a bottom plate and top plate of the panel. The solar pond is well suited for providing hot water of approximately 85 to 90 C temperature for direct heating applications, and for electrical power generation.

  3. Electrostatically clean solar array

    NASA Technical Reports Server (NTRS)

    Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

    2004-01-01

    Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

  4. Current and lattice matched tandem solar cell

    DOEpatents

    Olson, Jerry M.

    1987-01-01

    A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga.sub.x In.sub.1-x P (0.505.ltoreq.X.ltoreq.0.515) top cell semiconductor lattice matched to a GaAs bottom cell semiconductor at a low-resistance heterojunction, preferably a p+/n+ heterojunction between the cells. The top and bottom cells are both lattice matched and current matched for high efficiency solar radiation conversion to electrical energy.

  5. Flat-top and patterned-topped cone gratings for visible and mid-infrared antireflective properties.

    PubMed

    Brückner, Jean-Baptiste; Le Rouzo, Judikaël; Escoubas, Ludovic; Berginc, Gérard; Gourgon, Cécile; Desplats, Olivier; Simon, Jean-Jacques

    2013-07-01

    Achieving a broadband antireflection property from material surfaces is one of the highest priorities for those who want to improve the efficiency of solar cells or the sensitivity of photo-detectors. To lower the reflectance of a surface, we are concerned with the study of the optical response of flat-top and patterned-topped cone shaped silicon gratings, based on previous work exploring pyramid gratings. Through rigorous numerical methods such as Finite Different Time Domain, we first designed several flat-top structures that theoretically demonstrate an antireflective character within the middle infrared region. From the opto-geometrical parameters such as period, depth and shape of the pattern determined by numerical analysis, these structures have been fabricated using controlled slope plasma etching processes. In order to extend the antireflective properties up to the visible wavelengths, patterned-topped cones have been fabricated as well. Afterwards, optical characterizations of several samples were carried out. Thus, the performances of the flat-top and patterned-topped cones have been compared in the visible and mid infrared range.

  6. Low temperature Zn diffusion for GaSb solar cell structures fabrication

    NASA Technical Reports Server (NTRS)

    Sulima, Oleg V.; Faleev, Nikolai N.; Kazantsev, Andrej B.; Mintairov, Alexander M.; Namazov, Ali

    1995-01-01

    Low temperature Zn diffusion in GaSb, where the minimum temperature was 450 C, was studied. The pseudo-closed box (PCB) method was used for Zn diffusion into GaAs, AlGaAs, InP, InGaAs and InGaAsP. The PCB method avoids the inconvenience of sealed ampoules and proved to be simple and reproducible. The special design of the boat for Zn diffusion ensured the uniformality of Zn vapor pressure across the wafer surface, and thus the uniformity of the p-GaSb layer depth. The p-GaSb layers were studied using Raman scattering spectroscopy and the x-ray rocking curve method. As for the postdiffusion processing, an anodic oxidation was used for a precise thinning of the diffused GaSb layers. The results show the applicability of the PCB method for the large-scale production of the GaSb structures for solar cells.

  7. Australia's Next Top Fraction Model

    ERIC Educational Resources Information Center

    Gould, Peter

    2013-01-01

    Peter Gould suggests Australia's next top fraction model should be a linear model rather than an area model. He provides a convincing argument and gives examples of ways to introduce a linear model in primary classrooms.

  8. Trajectory correction propulsion for TOPS

    NASA Technical Reports Server (NTRS)

    Long, H. R.; Bjorklund, R. A.

    1972-01-01

    A blowdown-pressurized hydrazine propulsion system was selected to provide trajectory correction impulse for outer planet flyby spacecraft as the result of cost/mass/reliability tradeoff analyses. Present hydrazine component and system technology and component designs were evaluated for application to the Thermoelectric Outer Planet Spacecraft (TOPS); while general hydrazine technology was adequate, component design changes were deemed necessary for TOPS-type missions. A prototype hydrazine propulsion system was fabricated and fired nine times for a total of 1600 s to demonstrate the operation and performance of the TOPS propulsion configuration. A flight-weight trajectory correction propulsion subsystem (TCPS) was designed for the TOPS based on actual and estimated advanced components.

  9. Forum outlines top emerging technologies

    NASA Astrophysics Data System (ADS)

    Extance, Andy

    2015-04-01

    Additive manufacturing, next-generation robotics, "sense and avoid" drones that fly themselves, artificial intelligence and "neuromorphic" computing have all made it into the World Economic Forum's top 10 emerging technologies for 2015.

  10. Top 10 Products of 2011

    ERIC Educational Resources Information Center

    American School & University, 2011

    2011-01-01

    In 2011, American School & University (AS&U) showcased some of the hottest products in the industry. This article presents the top ten most requested products as determined by readers. The top one on the list is the Bulb crusher which can cut recycling costs by 50%, can hold 1,350 4-foot lamps in a single 55-gallon drum, can crush a 4-foot lamp in…

  11. Uncovering the single top: observation of electroweak top quark production

    SciTech Connect

    Benitez, Jorge Armando

    2009-01-01

    The top quark is generally produced in quark and anti-quark pairs. However, the Standard Model also predicts the production of only one top quark which is mediated by the electroweak interaction, known as 'Single Top'. Single Top quark production is important because it provides a unique and direct way to measure the CKM matrix element Vtb, and can be used to explore physics possibilities beyond the Standard Model predictions. This dissertation presents the results of the observation of Single Top using 2.3 fb-1 of Data collected with the D0 detector at the Fermilab Tevatron collider. The analysis includes the Single Top muon+jets and electron+jets final states and employs Boosted Decision Tress as a method to separate the signal from the background. The resulting Single Top cross section measurement is: (1) σ(p$\\bar{p}$→ tb + X, tqb + X) = 3.74-0.74+0.95 pb, where the errors include both statistical and systematic uncertainties. The probability to measure a cross section at this value or higher in the absence of signal is p = 1.9 x 10-6. This corresponds to a standard deviation Gaussian equivalence of 4.6. When combining this result with two other analysis methods, the resulting cross section measurement is: (2) σ(p$\\bar{p}$ → tb + X, tqb + X) = 3.94 ± 0.88 pb, and the corresponding measurement significance is 5.0 standard deviations.

  12. Variability of Solar Mesogranulation

    DTIC Science & Technology

    1988-01-01

    the method of local correlation tracking /2,3/.. These data show that solar granules mov~e like test particles ("corks") on top of larger-scale lne...distribution unlimited D T I C S ELECTEJUN& ZA 994 U 4 U From white--light photographs of solar granulation obtained with the SOUP instrument on Space...Shuttle Flioht STS-19 we have measured the motions of granules using local correlation tracking techniques. The cranules are or.anized into lar-er-gcale

  13. Heterostructure solar cells

    NASA Technical Reports Server (NTRS)

    Chang, K. I.; Yeh, Y. C. M.; Iles, P. A.; Morris, R. K.

    1987-01-01

    The performance of gallium arsenide solar cells grown on Ge substrates is discussed. In some cases the substrate was thinned to reduce overall cell weight with good ruggedness. The conversion efficiency of 2 by 2 cm cells under AMO reached 17.1 percent with a cell thickness of 6 mils. The work described forms the basis for future cascade cell structures, where similar interconnecting problems between the top cell and the bottom cell must be solved. Applications of the GaAs/Ge solar cell in space and the expected payoffs are discussed.

  14. 75 FR 76453 - Top of the World Wind Energy, LLC; Kit Carson Windpower, LLC; Chestnut Flats Wind, LLC; Minco...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-08

    ...-000; EG10-70-000; EG10-71-000] Top of the World Wind Energy, LLC; Kit Carson Windpower, LLC; Chestnut Flats Wind, LLC; Minco Wind, LLC; Arizona Solar One LLC; Criterion Power Partners, LLC; Sundevil...

  15. Building America Top Innovations 2012: Zero Net-Energy Homes Production Builder Business Case: California/Florida Production Builders

    SciTech Connect

    none,

    2013-01-01

    This Building America Top Innovations profile describes Grupe Homes of Sacramento’s work with Building America to design California’s first production-scale community of solar homes. The homes outsold neighboring developments two to one.

  16. SW New Mexico Oil Well Formation Tops

    SciTech Connect

    Shari Kelley

    2015-10-21

    Rock formation top picks from oil wells from southwestern New Mexico from scout cards and other sources. There are differing formation tops interpretations for some wells, so for those wells duplicate formation top data are presented in this file.

  17. Solar Water-Heater Design and Installation

    NASA Technical Reports Server (NTRS)

    Harlamert, P.; Kennard, J.; Ciriunas, J.

    1982-01-01

    Solar/Water heater system works as follows: Solar--heated air is pumped from collectors through rock bin from top to bottom. Air handler circulates heated air through an air-to-water heat exchanger, which transfers heat to incoming well water. In one application, it may reduce oil use by 40 percent.

  18. Perovskite Solar Cells with Large-Area CVD-Graphene for Tandem Solar Cells.

    PubMed

    Lang, Felix; Gluba, Marc A; Albrecht, Steve; Rappich, Jörg; Korte, Lars; Rech, Bernd; Nickel, Norbert H

    2015-07-16

    Perovskite solar cells with transparent contacts may be used to compensate for thermalization losses of silicon solar cells in tandem devices. This offers a way to outreach stagnating efficiencies. However, perovskite top cells in tandem structures require contact layers with high electrical conductivity and optimal transparency. We address this challenge by implementing large-area graphene grown by chemical vapor deposition as a highly transparent electrode in perovskite solar cells, leading to identical charge collection efficiencies. Electrical performance of solar cells with a graphene-based contact reached those of solar cells with standard gold contacts. The optical transmission by far exceeds that of reference devices and amounts to 64.3% below the perovskite band gap. Finally, we demonstrate a four-terminal tandem device combining a high band gap graphene-contacted perovskite top solar cell (Eg = 1.6 eV) with an amorphous/crystalline silicon bottom solar cell (Eg = 1.12 eV).

  19. High-efficiency nanostructured window GaAs solar cells.

    PubMed

    Liang, Dong; Kang, Yangsen; Huo, Yijie; Chen, Yusi; Cui, Yi; Harris, James S

    2013-10-09

    Nanostructures have been widely used in solar cells due to their extraordinary optical properties. In most nanostructured cells, high short circuit current has been obtained due to enhanced light absorption. However, most of them suffer from lowered open circuit voltage and fill factor. One of the main challenges is formation of good junction and electrical contact. In particular, nanostructures in GaAs only have shown unsatisfactory performances (below 5% in energy conversion efficiency) which cannot match their ideal material properties and the record photovoltaic performances in industry. Here we demonstrate a completely new design for nanostructured solar cells that combines nanostructured window layer, metal mesa bar contact with small area, high quality planar junction. In this way, we not only keep the advanced optical properties of nanostructures such as broadband and wide angle antireflection, but also minimize its negative impact on electrical properties. High light absorption, efficient carrier collection, leakage elimination, and good lateral conductance can be simultaneously obtained. A nanostructured window cell using GaAs junction and AlGaAs nanocone window demonstrates 17% energy conversion efficiency and 0.982 V high open circuit voltage.

  20. GaAs quantum dot solar cell under concentrated radiation

    SciTech Connect

    Sablon, K.; Little, J. W.; Hier, H.; Li, Y.; Mitin, V.; Vagidov, N.; Sergeev, A.

    2015-08-17

    Effects of concentrated solar radiation on photovoltaic performance are investigated in well-developed GaAs quantum dot (QD) solar cells with 1-Sun efficiencies of 18%–19%. In these devices, the conversion processes are enhanced by nanoscale potential barriers and/or AlGaAs atomically thin barriers around QDs, which prevent photoelectron capture to QDs. Under concentrated radiation, the short circuit current increases proportionally to the concentration and the open circuit voltage shows the logarithmic increase. In the range up to hundred Suns, the contributions of QDs to the photocurrent are proportional to the light concentration. The ideality factors of 1.1–1.3 found from the V{sub OC}-Sun characteristics demonstrate effective suppression of recombination processes in barrier-separated QDs. The conversion efficiency shows the wide maximum in the range of 40–90 Suns and reaches 21.6%. Detailed analysis of I-V-Sun characteristics shows that at low intensities, the series resistance decreases inversely proportional to the concentration and, at ∼40 Suns, reaches the plateau determined mainly by the front contact resistance. Improvement of contact resistance would increase efficiency to above 24% at thousand Suns.

  1. GaAs solar cells for concentrator systems in space

    NASA Technical Reports Server (NTRS)

    Loo, R. Y.; Knechtli, R. C.; Kamath, G. S.

    1983-01-01

    Cells for operation in space up to more than 100 suns were made, and an AMO efficiency of 21% at 100 suns with these cells was obtained. The increased efficiency resulted not only from the higher open circuit voltage associated with the higher light intensity (higher short circuit current); it also benefitted from the increase in fill factor caused by the lower relative contribution of the generation recombination current to the forward bias current when the cell's operating current density is increased. The experimental cells exhibited an AMO efficiency close to 16% at 200 C. The prospect of exploiting this capability for the continuous annealing of radiation damage or for high temperature missions (e.g., near Sun missions) remains therefore open. Space systems with concentration ratios on the order of 100 suns are presently under development. The tradeoff between increased concentration ratio and increased loss due to the cell's series resistance remains attractive even for space applications at a solar concentrator ratio of 100 suns. In the design of contact configuration with low enough series resistance for such solar concentration ratios, the shallow junction depth needed for good radiation hardness and the thin AlGaAs layer thickness needed to avoid excessive optical absorption losses have to be retained.

  2. Recombination current in AlGaAs/GaAs superlattice solar-cells grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kawaharazuka, A.; Nishinaga, J.; Horikoshi, Y.

    2015-09-01

    We investigate the effect of the recombination current of p-i-n junction solar-cells. We develop a simple evaluation method of the recombination and diffusion current component of the solar-cells based on the measured three characteristic values: short circuit current, open circuit voltage, and fill factor without the knowledge in the details of the device structure. The advantage of the developed technique is its simplicity and wide applicability to various p-i-n junction solar-cells. We apply the method to GaAs bulk and AlGaAs/GaAs superlattice solar-cells. Obtained parameters well reproduce the whole current-voltage characteristics. The diode current is almost dominated by the recombination current at the maximum-output voltage for both GaAs bulk and superlattice cells. The higher contribution of the recombination current in the superlattice solar-cell is due to the quality of the AlGaAs barriers and the AlGaAs/GaAs interfaces. This result indicates that the good crystalline quality is important to enhance the efficiency of the solar-cells.

  3. Computer modeling of high intensity solar cells

    NASA Astrophysics Data System (ADS)

    Gray, J. L.; Lundstrom, M. S.; Schwartz, R. J.

    1987-01-01

    The purpose of this program is to provide general analytic support to Sandia National Laboratories' effort to develop high efficiency, high concentration solar cells. This report covers work performed between November 5, 1984, and December 31, 1985, and includes reprints of three papers presented at the 18th IEEE Photovoltaic Specialists' Conference. In the first paper, the factors that presently prevent achieving the predicted theoretical efficiencies (in excess of 30% at concentration) are examined. It is demonstrated, by two-dimensional computer simulations, that these efficiencies might be obtained by improved light trapping techniques and by fabrication of low resistance heteroface contacts. The second paper examines the Rose-Weaver lifetime and surface recombination velocity measurement technique. It is shown that the very small uncertainties in the measured quantities lead to large uncertainties in the computed lifetime and surface recombination velocity. This leads to radically different interpretations of how the recombination is distributed throughout the device, and therefore limits the usefulness of the measurement technique. Design options and constraints of GaAs concentrator cells are examined in the third paper. The effectiveness of various design options is assessed. It is shown that although such design options are of little use in increasing the efficiency of heteroface cells, they can improve the efficiency of shallow junction cells so that it is comparable to that of heteroface cells, In addition, documentation describing the use of both the one- and two-dimensional silicon codes, SCAP1D and SCAP2D, as well as the one-dimensional AlGaAs solar cell simulation code is included.

  4. Integrated solar collector

    DOEpatents

    Tchernev, Dimiter I.

    1985-01-01

    A solar collector having a copper panel in a contiguous space relationship with a condenser-evaporator heat exchanger located under the panel, the panel having a honeycomb-like structure on its interior defining individual cells which are filled with zeolite loaded, in its adsorbed condition, with 18 to 20% by weight of water. The interior of the panel and heat exchanger are maintained at subatmospheric pressure of about 0.1 to 1 psia. The panel and heat exchanger are insulated on their lateral sides and bottoms and on the top of the heat exchange. The panel has a black coating on its top which is exposed to and absorbs solar energy. Surrounding the insulation (which supports the panel) is an extruded aluminum framework which supports a pair of spaced-apart glass panels above the solar panel. Water in conduits from a system for heating or cooling or both is connected to flow into an inlet and discharge from outlet of a finned coil received within the heat exchanger. The collector panel provides heat during the day through desorption and condensing of water vapor from the heated solar panel in the heat exchanger and cools at night by the re-adsorption of the water vapor from the heat exchanger which lowers the absolute pressure within the system and cools the heat exchange coils by evaporation.

  5. Possible impacts of a future grand solar minimum on climate: Stratospheric and global circulation changes.

    PubMed

    Maycock, A C; Ineson, S; Gray, L J; Scaife, A A; Anstey, J A; Lockwood, M; Butchart, N; Hardiman, S C; Mitchell, D M; Osprey, S M

    2015-09-27

    A future decline in solar activity would not offset projected global warmingA future decline in solar activity could have larger regional effects in winterTop-down mechanism contributes to Northern Hemisphere regional response.

  6. Training Top 10 Hall of Fame

    ERIC Educational Resources Information Center

    Training, 2012

    2012-01-01

    Microsoft Corporation and SCC Soft Computer are the newest inductees into the Training Top 10 Hall of Fame, joining the ranks of the 11 companies named to the hall since its inception in 2008 (Wyeth Pharmaceuticals subsequently was acquired by Pfizer Inc. in 2009). These 11 companies held Top 10 spots in the Training Top 50, Top 100, and now Top…

  7. Top Mass Measurements at the Tevatron

    SciTech Connect

    Wang, M.H.L.S.; /Fermilab

    2009-04-01

    We present the latest measurements of the top quark mass from the Tevatron. The different top decay channels and measurement techniques used for these results are also described. The world average of the top quark mass based on some of these new results combined with previous results is m{sub top} = 172.6 {+-} 1.4 GeV.

  8. Kowalevski top in quantum mechanics

    SciTech Connect

    Matsuyama, A.

    2013-09-15

    The quantum mechanical Kowalevski top is studied by the direct diagonalization of the Hamiltonian. The spectra show different behaviors depending on the region divided by the bifurcation sets of the classical invariant tori. Some of these spectra are nearly degenerate due to the multiplicity of the invariant tori. The Kowalevski top has several symmetries and symmetry quantum numbers can be assigned to the eigenstates. We have also carried out the semiclassical quantization of the Kowalevski top by the EBK formulation. It is found that the semiclassical spectra are close to the exact values, thus the eigenstates can be also labeled by the integer quantum numbers. The symmetries of the system are shown to have close relations with the semiclassical quantum numbers and the near-degeneracy of the spectra. -- Highlights: •Quantum spectra of the Kowalevski top are calculated. •Semiclassical quantization is carried out by the EBK formulation. •Quantum states are labeled by the semiclassical integer quantum numbers. •Multiplicity of the classical torus makes the spectra nearly degenerate. •Symmetries, quantum numbers and near-degenerate spectra are closely related.

  9. The Top Theological Degree Producers

    ERIC Educational Resources Information Center

    Diverse: Issues in Higher Education, 2012

    2012-01-01

    Each year, "Diverse: Issues in Higher Education" publishes a list of the Top 100 producers of associate, bachelor's and graduate degrees awarded to minority students based on research conducted by Dr. Victor M. H. Borden, professor of educational leadership and policy studies at Indiana University Bloomington. This year, for the first…

  10. "Top School Problems" Are Myths.

    ERIC Educational Resources Information Center

    Males, Mike

    1992-01-01

    A well-known "study" comparing the top school problems of 1940 (talking and gum chewing) with those of 1987 (drug abuse, pregnancy, and violence) is nonexistent. In 1940, 49 percent of all youth did not finish high school, 37,000 teenagers died from violence or disease, and 335,000 teens gave birth. Educators should discount pastoral…

  11. China offshore has top priority

    SciTech Connect

    Cornitius, T.A.

    1983-11-01

    Joint venture development of offshore petroleum reserves has top priority in the mammoth effort to modernize the People's Republic of China. While the country works to overcome a critical shortage of skilled personnel, export of oil, coal, consumer goods, and metals will finance technological imports.

  12. Observation of the Top Quark

    DOE R&D Accomplishments Database

    Kim, S. B.

    1995-08-01

    Top quark production is observed in{bar p}p collisions at{radical}s= 1.8 TeV at the Fermilab Tevatron. The Collider Detector at Fermilab (CDF) and D{O} observe signals consistent with t{bar t} to WWb{bar b}, but inconsistent with the background prediction by 4.8{sigma} (CDF), 4.6a (D{O}). Additional evidence for the top quark Is provided by a peak in the reconstructed mass distribution. The kinematic properties of the excess events are consistent with the top quark decay. They measure the top quark mass to be 176{plus_minus}8(stat.){plus_minus}10(sys.) GeV/c{sup 2} (CDF), 199{sub -21}{sup+19}(stat.){plus_minus}22(sys.) GeV/c{sup 2} (D{O}), and the t{bar t} production cross section to be 6.8{sub -2.4}{sup+3.6}pb (CDF), 6.4{plus_minus}2.2 pb (D{O}).

  13. Kinematic top analyses at CDF

    SciTech Connect

    Cobal-Grassman, M.; CDF Collaboration

    1996-01-01

    We present an update of the top quark analysis using kinematic techniques in {rho}{ovr string {rho}} collisions at {radical}s = 1.8 TeV with the Collider Detector at Fermilab (CDF). We reported before on a study which used 19.3 pb{sup -1} of data from the 1992-93 collider run, but now we use a larger data sample of 67 pb{sup -1}. First, we analyze the total transverse energy of the hard collision in W+{ge}3 jet events, showing the likely presence of a t{ovr string t} component in the event sample. Next, we compare in more detail the kinematic structure of W+{ge}3 jet events with expectations for top pair production and with background processes, predominantly direct W+ jet production. We again find W+{ge}3 jet events which cannot be explained in terms of background, but show kinematic features as expected from top. These events also show evidence for beauty quarks. The findings confirm the observation of top events made earlier in the data of the 1992-93 collider run.

  14. The Top STEM Degree Producers

    ERIC Educational Resources Information Center

    Diverse: Issues in Higher Education, 2012

    2012-01-01

    This article presents a list of the top Science, Technology, Engineering, and Mathematics (STEM) degree producers in the U.S. This list is broken down into seven categories: (1) Total Minority Research/Scholarship and Other Doctoral: Mathematics and Statistics; (2) Total Minority Bachelors: Biological and Biomedical Sciences; (3) Total Minority…

  15. Top Jets at the LHC

    SciTech Connect

    Almeida, L.G.; Lee, S.J.; Perez, G.; Sung, I.; Virzi, J.

    2008-10-06

    We investigatethe reconstruction of high pT hadronically-decaying top quarksat the Large Hadron Collider. One of the main challenges in identifying energetictop quarks is that the decay products become increasingly collimated. This reducesthe efficacy of conventional reconstruction methods that exploit the topology of thetop quark decay chain. We focus on the cases where the decay products of the topquark are reconstructed as a single jet, a"top-jet." The most basic"top-tag" methodbased on jet mass measurement is considered in detail. To analyze the feasibility ofthe top-tagging method, both theoretical and experimental aspects of the large QCDjet background contribution are examined. Based on a factorization approach, wederive a simple analytic approximation for the shape of the QCD jet mass spectrum.We observe very good agreement with the Monte Carlo simulation. We consider high pT tt bar production in the Standard Model as an example, and show that our theoretical QCD jet mass distributions can efficiently characterize the background via sideband analyses. We show that with 25 fb-1 of data, our approach allows us to resolve top-jets with pT _> 1 TeV, from the QCD background, and about 1.5 TeV top-jets with 100 fb-1, without relying on b-tagging. To further improve the significancewe consider jet shapes (recently analyzed in 0807.0234 [hep-ph]), which resolve thesubstructure of energy flow inside cone jets. A method of measuring the top quarkpolarization by using the transverse momentum of the bottom quark is also presented.The main advantages of our approach are: (i) the mass distributions are driven byfirst principle calculations, instead of relying solely on Monte Carlo simulation; (ii) for high pT jets (pT _> 1 TeV), IR-safe jet shape variables are robust against detectorresolution effects. Our analysis can be applied to other boosted massive particlessuch as the electroweak gauge bosons and the Higgs.

  16. Long-Term Cryogenic Propellant Storage for the TOPS Mission

    NASA Technical Reports Server (NTRS)

    Mustafi, Shuvo; Francis, John; Li, Xiaoyi; Purves, Lloyd; DeLee, Hudson; Riall, Sara; McGuinness, Dan; Willis, Dewey; Nixon, Conor; Devine Matt; Hedayat, Ali

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LOX) can dramatically enhance NASAs ability to explore the solar system because of their superior specific impulse (Isp) capability. Although these cryogenic propellants can be challenging to manage and store, they allow significant mass advantages over traditional hypergolic propulsion systems and are therefore technically enabling for many planetary science missions. New cryogenic storage techniques such as subcooling and the use of advanced insulation and low thermal conductivity support structures will allow for the long term storage and use of cryogenic propellants for solar system exploration and hence allow NASA to deliver more payloads to targets of interest, launch on smaller and less expensive launch vehicles, or both. Employing cryogenic propellants will allow NASA to perform missions to planetary destinations that would not be possible with the use of traditional hypergolic propellants. These new cryogenic storage technologies were implemented in a design study for the Titan Orbiter Polar Surveyor (TOPS) mission, with LH2 and LOX as propellants, and the resulting spacecraft design was able to achieve a 43 launch mass reduction over a TOPS mission, that utilized a conventional hypergolic propulsion system with mono-methyl hydrazine (MMH) and nitrogen tetroxide (NTO) propellants. This paper describes the cryogenic propellant storage design for the TOPS mission and demonstrates how these cryogenic propellants are stored passively for a decade-long Titan mission.

  17. Cryogenic propulsion for the Titan Orbiter Polar Surveyor (TOPS) mission

    NASA Astrophysics Data System (ADS)

    Mustafi, S.; DeLee, C.; Francis, J.; Li, X.; McGuinness, D.; Nixon, C. A.; Purves, L.; Willis, W.; Riall, S.; Devine, M.; Hedayat, A.

    2016-03-01

    Liquid hydrogen (LH2) and liquid oxygen (LO2) cryogenic propellants can dramatically enhance NASA's ability to explore the solar system due to their superior specific impulse (Isp) capability. Although these cryogenic propellants can be challenging to manage and store, they allow significant mass advantages over traditional hypergolic propulsion systems and are therefore enabling for many planetary science missions. New cryogenic storage techniques such as subcooling and the use of advanced insulation and low thermal conductivity support structures will allow for the long term storage and use of cryogenic propellants for solar system exploration and hence allow NASA to deliver more payloads to targets of interest, launch on smaller and less expensive launch vehicles, or both. These new cryogenic storage technologies were implemented in a design study for the Titan Orbiter Polar Surveyor (TOPS) mission, with LH2 and LO2 as propellants, and the resulting spacecraft design was able to achieve a 43% launch mass reduction over a TOPS mission, that utilized a traditional hypergolic propulsion system with mono-methyl hydrazine (MMH) and nitrogen tetroxide (NTO) propellants. This paper describes the cryogenic propellant storage design for the TOPS mission and demonstrates how these cryogenic propellants are stored passively for a decade-long Titan mission that requires the cryogenics propellants to be stored for 8.5 years.

  18. Properties of the Top Quark

    SciTech Connect

    Wicke, Daniel; /Wuppertal U., Dept. Math.

    2009-08-01

    The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the

  19. Attitude propulsion technology for TOPS

    NASA Technical Reports Server (NTRS)

    Moynihan, P. I.

    1972-01-01

    The thermoelectric outer planet spacecraft (TOPS) attitude propulsion subsystem (APS) effort is discussed. It includes the tradeoff rationale that went into the selection of an anhydrous hydrazine baseline system, followed by a discussion of the 0.22 N thruster and its integration into a portable, self-contained propulsion module that was designed, developed, and man rated to support the TOPS single-axis attitude control tests. The results of a cold-start feasibility demonstration with a modified thruster are presented. A description of three types of 0.44 thrusters that were procured for in-house evaluation is included along with the results of the test program. This is followed by a description of the APS feed system components, their evaluations, and a discussion of an evaluation of elastomeric material for valve seat seals. A list of new technology items which will be of value for application to future systems of this type is included.

  20. Top decays in extended models

    SciTech Connect

    Gaitan, R.; Miranda, O. G.; Cabral-Rosetti, L. G.

    2009-04-20

    Top quark decays are interesting as a mean to test the Standard Model (SM) predictions. The Cabbibo-Kobayashi-Maskawa (CKM)-suppressed process t{yields}cWW, and the rare decays t{yields}cZ, t{yields}H{sup 0}+c, and t{yields}c{gamma} an excellent window to probe the predictions of theories beyond the SM. We evaluate the flavor changing neutral currents (FCNC) decay t{yields}H{sup 0}+c in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions; the FCNC decays may place at tree level and are only supressed by the mixing between ordinary top and charm quarks. We also comment on the decay process t{yields}c+{gamma}, which involves radiative corrections.

  1. Thermoelectric Outer Planets Spacecraft (TOPS)

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The research and advanced development work is reported on a ballistic-mode, outer planet spacecraft using radioisotope thermoelectric generator (RTG) power. The Thermoelectric Outer Planet Spacecraft (TOPS) project was established to provide the advanced systems technology that would allow the realistic estimates of performance, cost, reliability, and scheduling that are required for an actual flight mission. A system design of the complete RTG-powered outer planet spacecraft was made; major technical innovations of certain hardware elements were designed, developed, and tested; and reliability and quality assurance concepts were developed for long-life requirements. At the conclusion of its active phase, the TOPS Project reached its principal objectives: a development and experience base was established for project definition, and for estimating cost, performance, and reliability; an understanding of system and subsystem capabilities for successful outer planets missions was achieved. The system design answered long-life requirements with massive redundancy, controlled by on-board analysis of spacecraft performance data.

  2. All-optical amplitude-phase transmultiplexing of RZ-OOK and RZ-BPSK to RZ-QPSK by polarization-insensitive XPM using a nonlinear birefringent AlGaAs waveguide.

    PubMed

    Cannon, B M; Mahmood, T; Astar, W; Apiratikul, P; Porkolab, G; Boudra, P; Mohsenin, T; Richardson, C J K; Carter, G M

    2013-08-26

    Polarization-insensitive (PI) phase-transmultiplexing (PTM) of a 10-Gb/s return-to-zero ON-OFF keying (RZ-OOK) pump and a 10-Gb/s RZbinary phase-shift keying (RZ-BPSK) probe to 20-Gb/s RZ-quadrature-PSK (RZ-QPSK) has been successfully demonstrated for the first time in a passive, birefringent AlGaAs waveguide, utilizing PI cross-phase modulation (PI-XPM). For differential QPSK (DQPSK)-detection, a 10 − 9-BER pre-amplified receiver sensitivity penalty of ≈ 2.5 dB for the in-phase component and ≈ 4.9 dB for the quadrature component were found. The penalties were relative to the FPGA-precoded RZ-DQPSK baseline for a pump-probe detuning of ≈ 12 nm, when the probe state of polarization was scrambled and the pump was launched off-axis into the waveguide.

  3. Top quark results at CDF

    SciTech Connect

    Leone, S.; CDF Collaboration

    1996-08-01

    We present the latest results on the top quark obtained by the CDF experiment using a data sample of about 110 {ital pb}{sup -1} collected at the Fermilab Tevatron collider. We briefly describe the candidate events selection and then discuss the production cross section determination and the mass measurement. The study of two new decay channels (all hadronic and ``tau dilepton``) is also reported.

  4. Observation of the Top Quark

    SciTech Connect

    Abachi, S.; Abbott, B.; Abolins, M.; Acharya, B.S.; Adam, I.; Adams, D.L.; Adams, M.; Ahn, S.; Aihara, H.; Aihara, H.; Alitti, J.; Alvarez, G.; Alves, G.A.; Amidi, E.; Amos, N.; Anderson, E.W.; Aronson, S.H.; Astur, R.; Avery, R.E.; Balamurali, V.; Balderston, J.; Baldin, B.; Bantly, J.; Bartlett, J.F.; Bazizi, K.; Bendich, J.; Beri, S.B.; Bertram, I.; Bezzubov, V.A.; Bhat, P.C.; Bhatnagar, V.; Bhattacharjee, M.; Bischoff, A.; Biswas, N.; Blazey, G.; Blessing, S.; Boehnlein, A.; Bojko, N.I.; Borcherding, F.; Borders, J.; Boswell, C.; Brandt, A.; Brock, R.; Bross, A.; Buchholz, D.; Burtovoi, V.S.; Butler, J.M.; Casey, D.; Castilla-Valdez, H.; Chakraborty, D.; Chang, S.; Chekulaev, S.V.; Chen, L.; Chen, W.; Chevalier, L.; Chopra, S.; Choudhary, B.C.; Christenson, J.H.; Chung, M.; Claes, D.; Clark, A.R.; Cobau, W.G.; Cochran, J.; Cooper, W.E.; Cretsinger, C.; Cullen-Vidal, D.; Cummings, M.; Cutts, D.; Dahl, O.I.; De, K.; Demarteau, M.; Demina, R.; Denisenko, K.; Denisenko, N.; Denisov, D.; Denisov, S.P.; Dharmaratna, W.; Diehl, H.T.; Diesburg, M.; Di Loreto, G.; Dixon, R.; Draper, P.; Drinkard, J.; Ducros, Y.; Dugad, S.R.; Durston-Johnson, S.; Edmunds, D.; Efimov, A.O.; Ellison, J.; Elvira, V.D.; Engelmann, R.; Eno, S.; Eppley, G.; Ermolov, P.; Eroshin, O.V.; Evdokimov, V.N.; Fahey, S.; Fahland, T.; Fatyga, M.; Fatyga, M.K.; Featherly, J.; Feher, S.; Fein, D.; Ferbel, T.; Finocchiaro, G.; Fisk, H.E.; Fisyak, Y.; Flattum, E.; Forden, G.E.; Fortner, M.; Frame, K.C.; Franzini, P.; Fredriksen, S.; Fuess, S.; Galjaev, A.N.; Gallas, E.; Gao, C.S.; Gao, S.; Geld, T.L.; Genik, R.J. II; Genser, K.; Gerber, C.E.; Gibbard, B.; Glaubman, M.; Glebov, V.; Glenn, S.; Glicenstein, J.F.; Gobbi, B.; Goforth, M.; Goldschmidt, A.; Gomez, B.; Goncharov, P.I.; Gordon, H.; Goss, L.T.; Graf, N.; Grannis, P.D.; Green, D.R.; Green, J.; Greenlee, H.; Griffin, G.; Grossman, N.; Grudberg, P.; Gruenendahl, S.; Guida, J.A.; Guida, J.M.; Guryn, W.; Gurzhiev, S.N.; Gutnikov, Y.E.

    1995-04-03

    The D0 Collaboration reports on a search for the standard model top quark in {ital p{bar p}} collisions at {radical}{ital s}=1.8TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50pb{sup {minus}1}. We have searched for {ital t{bar t}} production in the dilepton and single-lepton decay channels with and without tagging of {ital b}-quark jets. We observed 17 events with an expected background of 3.8{plus_minus}0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2{times}10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measured its mass to be 199{sub {minus}21}{sup +19} (stat) {plus_minus}22 (syst) GeV/{ital c}{sup 2} and its production cross section to be 6.4{plus_minus}2.2pb.

  5. Top quark studies at hadron colliders

    SciTech Connect

    Sinervo, P.K.

    1997-01-01

    The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.

  6. Recent Top Properties Measurements at CDF

    SciTech Connect

    Chiarelli, Giorgio

    2014-11-26

    We present the most recent CDF results on the measurements of the decay and production vertex of the top-quark. New results on forward-backward asymmetry in top-antitop events are presented. Also, recent measurements of the branching fractions of top-quark are discussed. Finally, measurements in single top events, where top-quark is produced through electroweak processes, are presented. Despite the much larger number of top events collected at the LHC, due to the symmetric initial state and the better signal-to-background ratio in specific channels, some results will be lasting heritage of the Tevatron.

  7. Solar Energy.

    ERIC Educational Resources Information Center

    Eaton, William W.

    Presented is the utilization of solar radiation as an energy resource principally for the production of electricity. Included are discussions of solar thermal conversion, photovoltic conversion, wind energy, and energy from ocean temperature differences. Future solar energy plans, the role of solar energy in plant and fossil fuel production, and…

  8. Solar energy

    NASA Technical Reports Server (NTRS)

    Rapp, D.

    1981-01-01

    The book opens with a review of the patterns of energy use and resources in the United States, and an exploration of the potential of solar energy to supply some of this energy in the future. This is followed by background material on solar geometry, solar intensities, flat plate collectors, and economics. Detailed attention is then given to a variety of solar units and systems, including domestic hot water systems, space heating systems, solar-assisted heat pumps, intermediate temperature collectors, space heating/cooling systems, concentrating collectors for high temperatures, storage systems, and solar total energy systems. Finally, rights to solar access are discussed.

  9. Solar Systems

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The solar collectors shown are elements of domestic solar hot water systems produced by Solar One Ltd., Virginia Beach, Virginia. Design of these systems benefited from technical expertise provided Solar One by NASA's Langley Research Center. The company obtained a NASA technical support package describing the d e sign and operation of solar heating equipment in NASA's Tech House, a demonstration project in which aerospace and commercial building technology are combined in an energy- efficient home. Solar One received further assistance through personal contact with Langley solar experts. The company reports that the technical information provided by NASA influenced Solar One's panel design, its selection of a long-life panel coating which increases solar collection efficiency, and the method adopted for protecting solar collectors from freezing conditions.

  10. Trial Production and Evaluation of Solar Cells Optimized for Solar Spectrum in Mars Atmosphere

    NASA Astrophysics Data System (ADS)

    Toyota, Hiroyuki; Shimada, Takanobu; Takahashi, Yu; Oyama, Akira; Washio, Hidetoshi

    2014-08-01

    We describe the production and evaluation of a prototype of an inverted metamorphic triple-junction (IMM3J) solar cell optimized for the solar spectrum on the surface of Mars. High-efficiency, flexible, lightweight solar panels containing IMM3J solar cells are promising power sources for Mars surface explorers such as rovers, landers, and airplanes. The intensity of sunlight at the Martian surface substantially decreases at wavelengths shorter than 700 nm because of absorption and scattering by the atmosphere. This decreases the output current of the InGaP top cells in state-of-the-art IMM3J solar cells, and thus decreases the overall output current. Therefore, solar cells for Mars surface explorers need to be optimized for the solar spectrum at the Martian surface. We modified IMM3J solar cells in two ways to increase the output power. We increased the thickness of the InGaP top cell to increase the light absorption, which increased the output current of the entire cell. We also increased the band gap energy of the InGaAs bottom cell by trimming the surplus current, in order to increase the output voltage. In the simulated Martian solar spectrum, the performance of the prototype solar cells was higher than that of IMM3J solar cells designed for the AM0 spectrum.

  11. Heavy flavour physics from top to bottom

    SciTech Connect

    Paulini, M.; CDF and D0 Collaboration

    1998-02-01

    We review the status of heavy flavour physics at the Fermilab Tevatron collider by summarizing recent top quark and B physics results from CDF and D0. In particular we discuss the measurement of the top quark mass and top production cross section as well as B meson lifetimes and time dependent B{anti B} mixing results. An outlook of perspectives for top and B physics in Run II starting in 1999 is also given.

  12. Cloud-top parameters - A hail indicator

    NASA Technical Reports Server (NTRS)

    Pearl, E. W.; Shenk, W. E.; Skillman, W.

    1975-01-01

    Airborne photographic observations of four hail-producing storms are discussed. With the exception of one storm producing a tornadic event, the overshooting tops were nearly steady-state. The tops were consistently high and wide, reaching maximum heights within about 5 minutes of the initiation of hail. Measured updraft velocities in the turrets composing the overshooting top were 25 m/sec. The dimensions of the overshooting tops were sufficiently large to permit satellite observation.

  13. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-07-01

    This eighteenth quarterly technical progress report of the MHD Integrated Topping cycle Project presents the accomplishments during the period November 1, 1991 to January 31, 1992. The precombustor is fully assembled. Manufacturing of all slagging stage components has been completed. All cooling panels were welded in place and the panel/shell gap was filled with RTV. Final combustor assembly is in progress. The low pressure cooling subsystem (LPCS) was delivered to the CDIF. Second stage brazing issues were resolved. The construction of the two anode power cabinets was completed.

  14. Table-top job analysis

    SciTech Connect

    Not Available

    1994-12-01

    The purpose of this Handbook is to establish general training program guidelines for training personnel in developing training for operation, maintenance, and technical support personnel at Department of Energy (DOE) nuclear facilities. TTJA is not the only method of job analysis; however, when conducted properly TTJA can be cost effective, efficient, and self-validating, and represents an effective method of defining job requirements. The table-top job analysis is suggested in the DOE Training Accreditation Program manuals as an acceptable alternative to traditional methods of analyzing job requirements. DOE 5480-20A strongly endorses and recommends it as the preferred method for analyzing jobs for positions addressed by the Order.

  15. HUBBLE'S TOP TEN GRAVITATIONAL LENSES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368

  16. Top quark physics expectations at the LHC

    SciTech Connect

    ATLAS Collaboration; CMS Collaboration; Gaponenko, Andrei

    2008-09-30

    The top quark will be produced copiously at the LHC. This will make possible detailed physics studies, and also the use of top quark decays for detector calibration. This talk reviews plans and prospects for top physics activities in ATLAS and CMS experiments.

  17. Schottky barrier solar cell

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M. (Inventor)

    1981-01-01

    A method of fabricating a Schottky barrier solar cell is described. The cell consists of a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive. A thin layer of heavily doped n-type polycrystalling germanium is deposited on the substrate after a passivation layer is deposited to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes to serve as a base layer on which a thin layer of gallium arsenide is vapor-epitaxilly grown followed by a thermally-grown oxide layer. A metal layer is deposited on the oxide layer and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer.

  18. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-01-01

    The overall objective of the project is to design and construct prototypical hardware for an integrated MHD topping cycle, and conduct long duration proof-of-concept tests of integrated system at the US DOE Component Development and Integration Facility in Butte, Montana. The results of the long duration tests will augment the existing engineering design data base on MHD power train reliability, availability, maintainability, and performance, and will serve as a basis for scaling up the topping cycle design to the next level of development, an early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include: A slagging coal combustor with a rated capacity of 50 MW thermal input, capable of operation with an Eastern (Illinois {number sign}6) or Western (Montana Rosebud) coal, a segmented supersonic nozzle, a supersonic MHD channel capable of generating at least 1.5 MW of electrical power, a segmented supersonic diffuser section to interface the channel with existing facility quench and exhaust systems, a complete set of current control circuits for local diagonal current control along the channel, and a set of current consolidation circuits to interface the channel with the existing facility inverter.

  19. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-03-01

    The Magnetohydrodynamics (MHD) Integrated Topping Cycle (ITC) Project represents the culmination of the proof-of-concept (POC) development stage in the US Department of Energy (DOE) program to advance MHD technology to early commercial development stage utility power applications. The project is a joint effort, combining the skills of three topping cycle component developers: TRW, Avco/TDS, and Westinghouse. TRW, the prime contractor and system integrator, is responsible for the 50 thermal megawatt (50 MW{sub t}) slagging coal combustion subsystem. Avco/TDS is responsible for the MHD channel subsystem (nozzle, channel, diffuser, and power conditioning circuits), and Westinghouse is responsible for the current consolidation subsystem. The ITC Project will advance the state-of-the-art in MHD power systems with the design, construction, and integrated testing of 50 MW{sub t} power train components which are prototypical of the equipment that will be used in an early commercial scale MHD utility retrofit. Long duration testing of the integrated power train at the Component Development and Integration Facility (CDIF) in Butte, Montana will be performed, so that by the early 1990's, an engineering data base on the reliability, availability, maintainability and performance of the system will be available to allow scaleup of the prototypical designs to the next development level. This Sixteenth Quarterly Technical Progress Report covers the period May 1, 1991 to July 31, 1991.

  20. Top quark physics at CDF

    SciTech Connect

    Caner, A.; CDF Collaboration

    1996-08-01

    We present preliminary results on top quark physics recently obtained by the CDF collaboration. The data sample consists of 110 {ital pb}{sup -1} of {ital p{anti p}} collisions at {radical}{ital s} = 1.8 TeV, collected with the Collider Detector at Fermilab during the period 1992 - 1995. We report on the {ital t{anti t}} production cross section and on the top quark mass. The measurements are made in three topologies, corresponding to the decay modes of the {ital Wb} pairs in the final state: lepton + multi-jets, dilepton and all hadronic final state. The analysis performed on the single lepton sample yields the most accurate measurements, due to the good acceptance and the favorable signal to noise ratio obtained after applying some b-tagging techniques. In this channel we measure: {sigma}{sub {ital t{anti t}}} = 6.8{sup +2.3}{sub -1.8} pb M{sub {ital t}} = 175.6 {+-} 5.7 ({ital stat}) {+-} 7.1 ({ital syst.}) {ital GeV/c{sup 2}} Combining the cross sections measured with the lepton + multi-jet and dilepton data we obtain: {sigma}{sub {ital t{anti t}}} = 7.5{sup +1.9}{sub -1.6} {ital pb} A preliminary investigation of the production mechanism of the {ital t{anti t}} system is shown and compared to Standard Model expectations.

  1. Solar Collectors

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Solar Energy's solar panels are collectors for a solar energy system which provides heating for a drive-in bank in Akron, OH. Collectors were designed and manufactured by Solar Energy Products, a firm established by three former NASA employees. Company President, Frank Rom, an example of a personnel-type technology transfer, was a Research Director at Lewis Research Center, which conducts extensive solar heating and cooling research, including development and testing of high-efficiency flat-plate collectors. Rom acquired solar energy expertise which helped the company develop two types of collectors, one for use in domestic/commercial heating systems and the other for drying grain.

  2. InGaP Heterojunction Barrier Solar Cells

    NASA Technical Reports Server (NTRS)

    Welser, Roger E.

    2010-01-01

    A new solar-cell structure utilizes a single, ultra-wide well of either gallium arsenide (GaAs) or indium-gallium-phosphide (InGaP) in the depletion region of a wide bandgap matrix, instead of the usual multiple quantum well layers. These InGaP barrier layers are effective at reducing diode dark current, and photogenerated carrier escape is maximized by the proper design of the electric field and barrier profile. With the new material, open-circuit voltage enhancements of 40 and 100 mV (versus PIN control systems) are possible without any degradation in short-circuit current. Basic tenets of quantum-well and quantum- dot solar cells are utilized, but instead of using multiple thin layers, a single wide well works better. InGaP is used as a barrier material, which increases open current, while simultaneously lowering dark current, reducing both hole diffusion from the base, and space charge recombination within the depletion region. Both the built-in field and the barrier profile are tailored to enhance thermionic emissions, which maximizes the photocurrent at forward bias, with a demonstrated voltage increase. An InGaP heterojunction barrier solar cell consists of a single, ultra-wide GaAs, aluminum-gallium-arsenide (AlGaAs), or lower-energy-gap InGaP absorber well placed within the depletion region of an otherwise wide bandgap PIN diode. Photogenerated electron collection is unencumbered in this structure. InGaAs wells can be added to the thick GaAs absorber layer to capture lower-energy photons.

  3. CP Violation in Single Top Quark Production

    SciTech Connect

    Geng, Weigang

    2012-01-01

    We present a search for CP violation in single top quark production with the DØ experiment at the Tevatron proton-antiproton collider. CP violation in the top electroweak interaction results in different single top quark production cross sections for top and antitop quarks. We perform the search in the single top quark final state using 5.4 fb-1 of data, in the s-channel, t-channel, and for both combined. At this time, we do not see an observable CP asymmetry.

  4. Top Quark Studies at D0

    SciTech Connect

    Peters, Reinhild Yvonne

    2014-11-26

    Years after its discovery in 1995 by CDF and D0, the top quark still undergoes intense investigations at the Tevatron. Using up to the full Run II data sample, new measurements of top quark production and properties by the D0 Collaboration are presented. In particular, the first observation of single top quark s-channel production, the measurement of differential tbar t distributions, forward-backward tbar t asymmetry, a new measurement of the top quark mass, and a measurement of the top quark charge are discussed.

  5. Measurements of top quark properties at CDF

    SciTech Connect

    Kraan, Aafke C.; /Pennsylvania U.

    2006-11-01

    The top quark with its mass of about 172 GeV/c{sup 2} is the most massive fundamental particle observed by experiment. In this talk they highlight the most recent measurements of several top quark properties performed with the CDF detector based on data samples corresponding to integrated luminosities up to 1 fb{sup -1}. These results include a search for top quark pair production via new massive resonances, measurements of the helicity of the W boson from top-quark decay, and a direct limit on the lifetime of the top quark.

  6. Mechanically-stacked tandem solar cells with GaAsP on GaP and silicon

    NASA Technical Reports Server (NTRS)

    Negley, Gerald H.; Mcneely, James B.; Lasswell, Patrick G.; Gartley, Edgar A.; Barnett, Allen M.

    1987-01-01

    Preliminary results are encouraging for the achievement of high conversion efficiencies using a GaAsP top solar cell mechanically stacked on a conventional silicon solar cell. A realistic maximum of 29.4 percent is suggested when both the top and bottom solar cells are state of the art. Practical system efficiencies greater than 25 percent are attainable in the near future with the use of a state of the art bottom solar cell.

  7. Central solar energy receiver

    DOEpatents

    Drost, M. Kevin

    1983-01-01

    An improved tower-mounted central solar energy receiver for heating air drawn through the receiver by an induced draft fan. A number of vertically oriented, energy absorbing, fin-shaped slats are radially arranged in a number of concentric cylindrical arrays on top of the tower coaxially surrounding a pipe having air holes through which the fan draws air which is heated by the slats which receive the solar radiation from a heliostat field. A number of vertically oriented and wedge-shaped columns are radially arranged in a number of concentric cylindrical clusters surrounding the slat arrays. The columns have two mirror-reflecting sides to reflect radiation into the slat arrays and one energy absorbing side to reduce reradiation and reflection from the slat arrays.

  8. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-07-01

    This seventeenth quarterly technical progress report of the MHD Integrated Topping Cycle Project presents the accomplishments during the period August 1, 1991 to October 31, 1991. Manufacturing of the prototypical combustor pressure shell has been completed including leak, proof, and assembly fit checking. Manufacturing of forty-five cooling panels was also completed including leak, proof, and flow testing. All precombustor internal components (combustion can baffle and swirl box) were received and checked, and integration of the components was initiated. A decision was made regarding the primary and backup designs for the 1A4 channel. The assembly of the channel related prototypical hardware continued. The cathode wall electrical wiring is now complete. The mechanical design of the diffuser has been completed.

  9. Solar solids reactor

    DOEpatents

    Yudow, Bernard D.

    1987-01-01

    A solar powered kiln is provided, that is of relatively simple design and which efficiently uses solar energy. The kiln or solids reactor includes a stationary chamber with a rearward end which receives solid material to be reacted and a forward end through which reacted material is disposed of, and a screw conveyor extending along the bottom of the chamber for slowly advancing the material between the chamber ends. Concentrated solar energy is directed to an aperture at the forward end of the chamber to heat the solid material moving along the bottom of the chamber. The solar energy can be reflected from a mirror facing at an upward incline, through the aperture and against a heat-absorbing material near the top of the chamber, which moves towards the rear of the chamber to distribute heat throughout the chamber. Pumps at the forward and rearward ends of the chamber pump heated sweep gas through the length of the chamber, while minimizing the flow of gas through an open aperture through which concentrated sunlight is received.

  10. Solar solids reactor

    DOEpatents

    Yudow, B.D.

    1986-02-24

    A solar powered kiln is provided, that is of relatively simple design and which efficiently uses solar energy. The kiln or solids reactor includes a stationary chamber with a rearward end which receives solid material to be reacted and a forward end through which reacted material is disposed of, and a screw conveyor extending along the bottom of the chamber for slowly advancing the material between the chamber ends. Concentrated solar energy is directed to an aperture at the forward end of the chamber to heat the solid material moving along the bottom of the chamber. The solar energy can be reflected from a mirror facing at an upward incline, through the aperture and against a heat-absorbing material near the top of the chamber, which moves towards the rear of the chamber to distribute heat throughout the chamber. Pumps at the forward and rearward ends of the chamber pump heated sweep gas through the length of the chamber, while minimizing the flow of gas through an open aperture through which concentrated sunlight is received.

  11. Solar collectors

    SciTech Connect

    Cassidy, V.M.

    1981-11-01

    Practical applications of solar energy in commercial, industrial and institutional buildings are considered. Two main types of solar collectors are described: flat plate collectors and concentrating collectors. Efficiency of air and hydronic collectors among the flat plate types are compared. Also several concentrators are described, including their sun tracking mechanisms. Descriptions of some recent solar installations are presented and a list representing the cross section of solar collector manufacturers is furnished.

  12. Monolithic cascade-type solar cells

    NASA Technical Reports Server (NTRS)

    Yamamoto, S.; Shibukawa, A.; Yamaguchi, M.

    1985-01-01

    Solar cells consist of a semiconductor base, a bottom cell with a band-gap energy of E1, and a top cell with a band-gap energy of E2, and 0.96 E1 1.36 eV and (0.80 E + 0.77) eV E2 (0.80 E1 + 0.92) eV. A monolithic cascade-type solar cell was prepared with an n(+)-type GaAs base, a GaInAs bottom solar cell, and a GaAiInAs top solar cell. The surface of the cell is coated with a SiO antireflection film. The efficiency of the cell is 32%.

  13. Physical processes within the nocturnal stratus-topped boundary layer

    SciTech Connect

    Moeng, C.H.; Shen, S. ); Randall, D.A. )

    1992-12-15

    Within the stratus-topped boundary layer many physical processes are involved: longwave radiation cooling, entrainment, latent heating, surface heating, solar heating, drizzling, etc. How all processes combine to maintain the turbulence within the stratus-topped boundary layer remains an unsolved problem. The large-eddy simulation technique is used to examine the first four physical processes mentioned. First, the contribution of each physical process to the thermodynamic differences between the updraft and downdraft branches of turbulent circulations is examined through a conditional sampling. Second, these mean thermodynamic differences are shown to express well the vertical distributions of heat and moisture fluxes within stratus-topped boundary layers. These provide a method to validate the process-partitioning technique. (This technique assumes that the net flux profile can be partitioned into different component-flux profiles according to physical processes and that each partitioned component flux is linear in height.) In this paper, the heat and moisture fluxes are process partitioned, and each component flux is found to contribute to the net flux in a way that is consistent with its corresponding process contribution to the mean thermodynamic differences between updrafts and downdrafts. Also, the net flux obtained by summing all component fluxes agrees well with that obtained directly from the large-eddy simulations.

  14. Solar Equipment

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A medical refrigeration and a water pump both powered by solar cells that convert sunlight directly into electricity are among the line of solar powered equipment manufactured by IUS (Independent Utility Systems) for use in areas where conventional power is not available. IUS benefited from NASA technology incorporated in the solar panel design and from assistance provided by Kerr Industrial Applications Center.

  15. Solar reflector

    SciTech Connect

    Stone, D. C.

    1981-02-17

    A solar reflector having a flexible triangular reflective sheet or membrane for receiving and reflecting solar energy therefrom. The reflector is characterized by the triangular reflective sheet which is placed under tension thereby defining a smooth planar surface eliminating surface deflection which heretofore has reduced the efficiency of reflectors or heliostats used in combination for receiving and transmitting solar energy to an absorber tower.

  16. Buying Solar.

    ERIC Educational Resources Information Center

    Dawson, Joe

    Presented are guidelines for buying solar systems for the individual consumer. This is intended to help the consumer reduce many of the risks associated with the purchase of solar systems, particularly the risks of fraud and deception. Engineering terms associated with solar technology are presented and described to enable the consumer to discuss…

  17. A solar array module fabrication process for HALE solar electric UAVs

    NASA Astrophysics Data System (ADS)

    Carey, P. G.; Aceves, R. C.; Colella, N. J.; Thompson, J. B.; Williams, K. A.

    1993-12-01

    We describe a fabrication process to manufacture high power to weight ratio flexible solar array modules for use on high altitude long endurance (HALE) solar electric unmanned air vehicles (UAV's). A span-loaded flying wing vehicle, known as the RAPTOR Pathfinder, is being employed as a flying test bed to expand the envelope of solar powered flight to high altitudes. It requires multiple light weight, flexible solar array modules able to endure adverse environmental conditions. At high altitudes the solar UV flux is significantly enhanced relative to sea level and extreme thermal variations occur. Our process involves first electrically interconnecting solar cells into an array followed by laminating them between top and bottom laminated layers into a solar array module. After careful evaluation of candidate polymers, fluoropolymer materials have been selected as the array laminate layers because of their inherent abilities to withstand the hostile conditions imposed by the environment.

  18. The rise and fall of spinning tops

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2013-04-01

    The motion of four different spinning tops was filmed with a high-speed video camera. Unlike pointed tops, tops with a rounded peg precess initially about a vertical axis that lies well outside the top, and then spiral inward until the precession axis passes through a point close to the center-of-mass. The center-of-mass of a top with a rounded peg can rise as a result of rolling rather than sliding friction, contrary to the explanation normally given for the rise of spinning tops. A tippe top was also filmed and was observed to jump vertically off a horizontal surface several times while the center-of-mass was rising, contrary to the usual assumption that the normal reaction force on a tippe top remains approximately equal to its weight. It was found that the center-of-mass of a tippe top rises as a result of rolling friction at low spin frequencies and as a result of sliding friction at high spin frequencies. It was also found that, at low spin frequencies, a tippe top can precess at two different frequencies simultaneously.

  19. Advanced Rainbow Solar Photovoltaic Arrays

    NASA Technical Reports Server (NTRS)

    Mardesich, Nick; Shields, Virgil

    2003-01-01

    array with panels of photovoltaic cells on two sides (see figure). The surface supporting the solar cells can be adjusted in length or angle to accommodate the incident spectral pattern. An unoptimized prototype assembly containing ten adjacent prisms and three photovoltaic cells with different bandgaps (InGaP2, GaAs, and InGaAs) was constructed to demonstrate feasibility. The actual array will consist of a lightweight thin-film silicon layer of prisms curved into a parabolic shape. In an initial test under illumination of 1 sun at zero airmass, the energy-conversion efficiency of the assembly was found to be 20 percent. Further analysis of the data from this test led to a projected energy conversion efficiency as high as 41 percent for an array of 6 cells or strings (GaP, AlGaAs, InGaP2, GaAs, and two different InGaAs cells or strings).

  20. Transport Imaging of Multi-Junction and CIGS Solar Cell Materials

    DTIC Science & Technology

    2011-12-01

    solar energy. Indium Gallium Phosphide (InGaP) is commonly used as the top cell in multi-junction cells grown on... solar energy. Indium Gallium Phosphide (InGaP) is commonly used as the top cell in multi-junction cells grown on Germanium (Ge) or Gallium Arsenide...mobility of several Indium Gallium Phosphide (InGaP) materials for use in multi-junction solar cells . This will be done through transport imaging,

  1. Solar flair.

    PubMed Central

    Manuel, John S

    2003-01-01

    Design innovations and government-sponsored financial incentives are making solar energy increasingly attractive to homeowners and institutional customers such as school districts. In particular, the passive solar design concept of daylighting is gaining favor among educators due to evidence of improved performance by students working in daylit classrooms. Electricity-generating photovoltaic systems are also becoming more popular, especially in states such as California that have high electric rates and frequent power shortages. To help spread the word about solar power, the U.S. Department of Energy staged its first-ever Solar Decathlon in October 2002. This event featured solar-savvy homes designed by 14 college teams. PMID:12573926

  2. Solar Meter

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The instrument pictured is an inexpensive solar meter which is finding wide acceptance among architects, engineers and others engaged in construction of solar energy facilities. It detects the amount of solar energy available at a building site, information necessary to design the most efficient type of solar system for a particular location. Incorporating technology developed by NASA's Lewis Research Center, the device is based upon the solar cell, which provides power for spacecraft by converting the sun's energy to electricity. The meter is produced by Dodge Products, Inc., Houston, Texas, a company formed to bring the technology to the commercial marketplace.

  3. Solar flair.

    PubMed

    Manuel, John S

    2003-02-01

    Design innovations and government-sponsored financial incentives are making solar energy increasingly attractive to homeowners and institutional customers such as school districts. In particular, the passive solar design concept of daylighting is gaining favor among educators due to evidence of improved performance by students working in daylit classrooms. Electricity-generating photovoltaic systems are also becoming more popular, especially in states such as California that have high electric rates and frequent power shortages. To help spread the word about solar power, the U.S. Department of Energy staged its first-ever Solar Decathlon in October 2002. This event featured solar-savvy homes designed by 14 college teams.

  4. Solar Energy: Solar System Economics.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on solar system economics is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies.…

  5. Solar Sailing

    NASA Technical Reports Server (NTRS)

    Johnson, Les

    2009-01-01

    Solar sailing is a topic of growing technical and popular interest. Solar sail propulsion will make space exploration more affordable and offer access to destinations within (and beyond) the solar system that are currently beyond our technical reach. The lecture will describe solar sails, how they work, and what they will be used for in the exploration of space. It will include a discussion of current plans for solar sails and how advanced technology, such as nanotechnology, might enhance their performance. Much has been accomplished recently to make solar sail technology very close to becoming an engineering reality and it will soon be used by the world s space agencies in the exploration of the solar system and beyond. The first part of the lecture will summarize state-of-the-art space propulsion systems and technologies. Though these other technologies are the key to any deep space exploration by humans, robots, or both, solar-sail propulsion will make space exploration more affordable and offer access to distant and difficult destinations. The second part of the lecture will describe the fundamentals of space solar sail propulsion and will describe the near-, mid- and far-term missions that might use solar sails as a propulsion system. The third part of the lecture will describe solar sail technology and the construction of current and future sailcraft, including the work of both government and private space organizations.

  6. Top quark mass: past, present and future

    SciTech Connect

    Gutierrez, Gaston; /Fermilab

    2007-07-01

    The top quark is the most massive elementary particle discovered thus far. Its large mass may help explain the mechanism by which fundamental particles gain mass - the Standard Model's greatest standing mystery. Today the top quark mass, together with the W boson mass, plays an important role in constraining the Higgs boson mass. The current status of the top quark mass measurement and a brief outline of the expectation at the Large Hadron Collider and the International Linear Collider will be covered.

  7. TOP500 Supercomputers for June 2005

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2005-06-22

    25th Edition of TOP500 List of World's Fastest Supercomputers Released: DOE/L LNL BlueGene/L and IBM gain Top Positions MANNHEIM, Germany; KNOXVILLE, Tenn.; BERKELEY, Calif. In what has become a closely watched event in the world of high-performance computing, the 25th edition of the TOP500 list of the world's fastest supercomputers was released today (June 22, 2005) at the 20th International Supercomputing Conference (ISC2005) in Heidelberg Germany.

  8. TOP500 Supercomputers for November 2004

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2004-11-08

    24th Edition of TOP500 List of World's Fastest Supercomputers Released: DOE/IBM BlueGene/L and NASA/SGI's Columbia gain Top Positions MANNHEIM, Germany; KNOXVILLE, Tenn.; BERKELEY, Calif. In what has become a closely watched event in the world of high-performance computing, the 24th edition of the TOP500 list of the worlds fastest supercomputers was released today (November 8, 2004) at the SC2004 Conference in Pittsburgh, Pa.

  9. Top quark mass measurements at CDF

    SciTech Connect

    Maki, Tuula; /Helsinki U. /Helsinki Inst. of Phys.

    2007-10-01

    The top quark mass is interesting both as a fundamental parameter of the standard model as well as an important input to precision electroweak tests. The CDF Collaboration has measured the top quark mass with high precision in all decay channels with complementary methods. A combination of the results from CDF gives a top quark mass of 170.5{+-}1.3(stat.){+-}1.8(syst.) GeV/c{sup 2}.

  10. TOP500 Supercomputers for June 2004

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2004-06-23

    23rd Edition of TOP500 List of World's Fastest Supercomputers Released: Japan's Earth Simulator Enters Third Year in Top Position MANNHEIM, Germany; KNOXVILLE, Tenn.;&BERKELEY, Calif. In what has become a closely watched event in the world of high-performance computing, the 23rd edition of the TOP500 list of the world's fastest supercomputers was released today (June 23, 2004) at the International Supercomputer Conference in Heidelberg, Germany.

  11. Top quark physics at the Tevatron

    SciTech Connect

    D. Gerdes

    2004-01-28

    Precision studies of the top quark are a prime goal of the Run II physics program at the Fermilab Tevatron. Since the start of Run II in early 2002, the CDF and D0 experiments have analyzed approximately 100 pb{sup -1} of data and have re-established the top quark signal. In this article the author summarizes recent measurements of the top production cross section and mass.

  12. Boat Deck, Cabin Deck, Bridge Deck, Flat House Top, Stage ...

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

    Boat Deck, Cabin Deck, Bridge Deck, Flat House Top, Stage Top, Mast House Top, Upper Deck, Flat House Tops, Forecastle Deck, Main Deck - American Racer, Suisun Bay Reserve Fleet, Benicia, Solano County, CA

  13. Top Quark Mass Measurements at the Tevatron

    SciTech Connect

    Peters, Reinhild Yvonne

    2014-01-01

    Since the discovery of the top quark in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron proton antiproton collider, precise measurements of its mass are ongoing. Using data recorded by the D0 and CDF experiment, corresponding to up to the full Tevatron data sample, top quark mass measurements performed in different final states using various extraction techniques are presented in this article. The recent Tevatron top quark mass combination yields m_t=173.20 +-0.87 GeV. Furthermore, measurements of the top antitop quark mass difference from the Tevatron are discussed.

  14. Top Quark Production Asymmetries AFBt and AFBl

    DOE PAGES

    Berger, Edmond L.; Cao, Qing-Hong; Chen, Chuan-Ren; ...

    2012-02-14

    A large forward-backward asymmetry is seen in both the top quark rapidity distribution AFBt and in the rapidity distribution of charged leptons AFBl from top quarks produced at the Tevatron. We study the kinematic and dynamic aspects of the relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We emphasize the value of both measurements, and we conclude that a new physics model which produces more right-handed than left-handed top quarks is favored by the present data.

  15. MHD Integrated Topping Cycle Project

    SciTech Connect

    Not Available

    1992-02-01

    This fourteenth quarterly technical progress report of the MHD Integrated Topping Cycle Project presents the accomplishments during the period November 1, 1990 to January 31, 1991. Testing of the High Pressure Cooling Subsystem electrical isolator was completed. The PEEK material successfully passed the high temperature, high pressure duration tests (50 hours). The Combustion Subsystem drawings were CADAM released. The procurement process is in progress. An equipment specification and RFP were prepared for the new Low Pressure Cooling System (LPCS) and released for quotation. Work has been conducted on confirmation tests leading to final gas-side designs and studies to assist in channel fabrication.The final cathode gas-side design and the proposed gas-side designs of the anode and sidewall are presented. Anode confirmation tests and related analyses of anode wear mechanisms used in the selection of the proposed anode design are presented. Sidewall confirmation tests, which were used to select the proposed gas-side design, were conducted. The design for the full scale CDIF system was completed. A test program was initiated to investigate the practicality of using Avco current controls for current consolidation in the power takeoff (PTO) regions and to determine the cause of past current consolidation failures. Another important activity was the installation of 1A4-style coupons in the 1A1 channel. A description of the coupons and their location with 1A1 channel is presented herein.

  16. Top-of-Rail lubricant

    SciTech Connect

    Alzoubi, M. F.; Fenske, G. R.; Erck, R. A.; Boparai, A. S.

    2000-07-14

    Analysis of the volatile and semivolatile fractions collected after use of the TOR lubricant indicated that other than contaminants in the collection laboratory, no compounds on the EPA's Target Compound Lists (Tables 2 and 5) were detected in these fractions. The data of these qualitative analyses, given in the various tables in the text, indicate only the relative amounts of the tentatively identified compounds. The authors recommend that quantitative analysis be performed on the volatile and semivolatile fractions to allow confirmation of the tentatively identified compounds and to obtain absolute amounts of the detected compounds. Additionally, the semivolatile fraction should be analyzed by liquid chromatography/mass spectrometry to identify compounds that are not chromatographable under the temperature program used for determination of semivolatile compounds. Introducing the top-of-rail (TOR) lubricant into the wheel/rail interface results in a reduction of almost 60% of lateral friction force over the forces encountered under dry conditions. This reveals good potential for energy savings, as well as wear reduction, for railroad companies. In TOR lubrication, an increase in the angle of attack and axle load results in increased lateral friction and rate of lubricant consumption. The most efficient TOR lubricant quantity to be used in the wheel/rail interface must be calculated precisely according to the number of cars, axle loads, train speed, and angle of attack.

  17. Influence of Diffused Solar Radiation on the Solar Concentrating System of a Plant Shoot Configuration

    NASA Astrophysics Data System (ADS)

    Obara, Shin'ya

    Investigation of a plant shoot configuration is used to obtain valuable information concerning the received light system. Additionally, analysis results concerning a plant shoot configuration interaction with direct solar radiation were taken from a past study. However, in order to consider a plant shoot as a received sunlight system, it is necessary to understand the received light characteristics of both direct solar radiation and diffused solar radiation. Under a clear sky, the ratio of direct solar radiation to diffused solar radiation is large. However, under a clouded sky, the amount of diffused solar radiation becomes larger. Therefore, in this paper, we investigate the received light characteristics of a plant shoot configuration under the influence of diffused solar radiation. As a result, we clarify the relationship between the amount of diffused solar radiation and the amount of received light as a function of the characteristics of the plant shoot configuration. In order to obtain diffused solar radiation, it is necessary to correspond to the radiation of the multi-directions. In the analysis, the characteristic of the difference in arrangement of the top leaf and the other leaf was obtained. Therefore, in analysis, leaves other than the top were distributed in the wide range.

  18. Light-trapping and recycling for extraordinary power conversion in ultra-thin gallium-arsenide solar cells

    DOE PAGES

    Eyderman, Sergey; John, Sajeev

    2016-06-23

    Here, we demonstrate nearly 30% power conversion efficiency in ultra-thin (~200 nm) gallium arsenide photonic crystal solar cells by numerical solution of the coupled electromagnetic Maxwell and semiconductor drift-diffusion equations. Our architecture enables wave-interference-induced solar light trapping in the wavelength range from 300-865 nm, leading to absorption of almost 90% of incoming sunlight. Our optimized design for 200 nm equivalent bulk thickness of GaAs, is a square-lattice, slanted conical-pore photonic crystal (lattice constant 550 nm, pore diameter 600 nm, and pore depth 290 nm), passivated with AlGaAs, deposited on a silver back-reflector, with ITO upper contact and encapsulated with SiO2.more » Our model includes both radiative and non-radiative recombination of photo-generated charge carriers. When all light from radiative recombination is assumed to escape the structure, a maximum achievable photocurrent density (MAPD) of 27.6 mA/cm2 is obtained from normally incident AM 1.5 sunlight. For a surface non-radiative recombination velocity of 103 cm/s, this corresponds to a solar power conversion efficiency of 28.3%. When all light from radiative recombination is trapped and reabsorbed (complete photon recycling) the power conversion efficiency increases to 29%. If the surface recombination velocity is reduced to 10 cm/sec, photon recycling is much more effective and the power conversion efficiency reaches 30.6%.« less

  19. Design optimization for two-step photon absorption in quantum dot solar cells by using infrared photocurrent spectroscopy

    NASA Astrophysics Data System (ADS)

    Tamaki, R.; Shoji, Y.; Okada, Y.

    2016-03-01

    Multi-stacked quantum dot solar cell (QDSC) is a promising candidate for intermediate band solar cell, which can exceed thermodynamic efficiency limit of single-junction solar cells. In recent years, lots of effort has been made to evaluate and understand the photo-carrier response of two-step photon absorption in QDSCs. One crucial issue is to suppress thermal excitation of photo-carriers out of QDs, which obscures the QD filling under quasi-equilibrium at operation conditions. We have investigated infrared photocurrent spectra of the QD states to conduction band (CB) transition by using Fourier transform infrared (FTIR) spectroscopy. Multi-stacked In(Ga)As QDSCs with different barrier materials, such as GaAs, GaNAs, GaAsSb, and AlGaAs, were investigated. The IR absorption edge of the QD to CB transition was evaluated at low temperature by analyzing the low energy tail of the FTIR spectra. The threshold temperature of the two-step photon absorption in In(Ga)As QDSCs was determined by observing temperature dependence of the IR photo-response. A universal linear relationship between the threshold temperature and the IR absorption edge was obtained in In(Ga)As QDSCs with varied barrier materials. The threshold temperature of 295 K was predicted for the absorption edge at 0.459 eV by extrapolating the linear relationship. It reveals strategy for cell optimization to achieve efficient two-step photon absorption at ambient conditions.

  20. Light-trapping and recycling for extraordinary power conversion in ultra-thin gallium-arsenide solar cells

    SciTech Connect

    Eyderman, Sergey; John, Sajeev

    2016-06-23

    Here, we demonstrate nearly 30% power conversion efficiency in ultra-thin (~200 nm) gallium arsenide photonic crystal solar cells by numerical solution of the coupled electromagnetic Maxwell and semiconductor drift-diffusion equations. Our architecture enables wave-interference-induced solar light trapping in the wavelength range from 300-865 nm, leading to absorption of almost 90% of incoming sunlight. Our optimized design for 200 nm equivalent bulk thickness of GaAs, is a square-lattice, slanted conical-pore photonic crystal (lattice constant 550 nm, pore diameter 600 nm, and pore depth 290 nm), passivated with AlGaAs, deposited on a silver back-reflector, with ITO upper contact and encapsulated with SiO2. Our model includes both radiative and non-radiative recombination of photo-generated charge carriers. When all light from radiative recombination is assumed to escape the structure, a maximum achievable photocurrent density (MAPD) of 27.6 mA/cm2 is obtained from normally incident AM 1.5 sunlight. For a surface non-radiative recombination velocity of 103 cm/s, this corresponds to a solar power conversion efficiency of 28.3%. When all light from radiative recombination is trapped and reabsorbed (complete photon recycling) the power conversion efficiency increases to 29%. If the surface recombination velocity is reduced to 10 cm/sec, photon recycling is much more effective and the power conversion efficiency reaches 30.6%.

  1. Measuring top-quark polarization in top-pair + missing-energy events.

    PubMed

    Berger, Edmond L; Cao, Qing-Hong; Yu, Jiang-Hao; Zhang, Hao

    2012-10-12

    The polarization of a top quark can be sensitive to new physics beyond the standard model. Since the charged lepton from top-quark decay is maximally correlated with the top-quark spin, it is common to measure the polarization from the distribution in the angle between the charged lepton and the top-quark directions. We propose a novel method based on the charged lepton energy fraction and illustrate the method with a detailed simulation of top-quark pairs produced in supersymmetric top squark pair production. We show that the lepton energy ratio distribution that we define is very sensitive to the top-quark polarization but insensitive to the precise measurement of the top-quark energy.

  2. DSCOVR High Time Resolution Solar Wind Measurements

    NASA Technical Reports Server (NTRS)

    Szabo, Adam

    2012-01-01

    The Deep Space Climate Observatory (DSCOVR), previously known as Triana, spacecraft is expected to be launched in late 2014. It will carry a fluxgate magnetometer, Faraday Cup solar wind detector and a top-hat electron electrostatic analyzer. The Faraday Cup will provide an unprecedented 10 vectors/sec time resolution measurement of the solar wind proton and alpha reduced distribution functions. Coupled with the 40 vector/sec vector magnetometer measurements, the identification of specific wave modes in the solar wind will be possible for the first time. The science objectives and data products of the mission will be discussed.

  3. Solar energy control system. [temperature measurement

    NASA Technical Reports Server (NTRS)

    Currie, J. R. (Inventor)

    1981-01-01

    A solar energy control system for a hot air type solar energy heating system wherein thermocouples are arranged to sense the temperature of a solar collector, a space to be heated, and a top and bottom of a heat storage unit is disclosed. Pertinent thermocouples are differentially connected together, and these are employed to effect the operation of dampers, a fan, and an auxiliary heat source. In accomplishing this, the differential outputs from the thermocouples are amplified by a single amplifier by multiplexing techniques. Additionally, the amplifier is corrected as to offset by including as one multiplex channel a common reference signal.

  4. Review of Top Quark Physics Results

    SciTech Connect

    Kehoe, R.; Narain, M.; Kumar, A.

    2007-12-01

    As the heaviest known fundamental particle, the top quark has taken a central role in the study of fundamental interactions. Production of top quarks in pairs provides an important probe of strong interactions. The top quark mass is a key fundamental parameter which places a valuable constraint on the Higgs boson mass and electroweak symmetry breaking. Observations of the relative rates and kinematics of top quark final states constrain potential new physics. In many cases, the tests available with study of the top quark are both critical and unique. Large increases in data samples from the Fermilab Tevatron have been coupled with major improvements in experimental techniques to produce many new precision measurements of the top quark. The first direct evidence for electroweak production of top quarks has been obtained, with a resulting direct determination of V{sub tb}. Several of the properties of the top quark have been measured. Progress has also been made in obtaining improved limits on potential anomalous production and decay mechanisms. This review presents an overview of recent theoretical and experimental developments in this field. We also provide a brief discussion of the implications for further efforts.

  5. The Sakai Spinner: A Paperclip Top

    ERIC Educational Resources Information Center

    Corrao, Christian T.

    2014-01-01

    A challenge: Can you create a stable top from a single paper clip? Several interesting solutions to this problem were provided by Takao Sakai from Japan, the requirement of each being that the center of gravity be located on the vertical y-axis at the center of the top. In the simplest configuration, we see that there exists a single angle ?…

  6. Top-Ten IT Issues, 2008

    ERIC Educational Resources Information Center

    Allison, Debra H.; DeBlois, Peter B.

    2008-01-01

    EDUCAUSE presents the top-ten IT-related issues in terms of strategic importance to the higher education institution, as revealed by the ninth annual EDUCAUSE Current Issues Survey. This year, "Security" moves back to the top of the list. (Contains 20 notes.)

  7. 49 CFR 236.779 - Plate, top.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Plate, top. 236.779 Section 236.779 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.779 Plate, top....

  8. 49 CFR 236.779 - Plate, top.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Plate, top. 236.779 Section 236.779 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.779 Plate, top....

  9. Race to Top Draws out New Suitors

    ERIC Educational Resources Information Center

    McNeil, Michele

    2012-01-01

    The list of 61 finalists for the latest Race to the Top competition shows that the U.S. Department of Education was successful in enticing high-scoring applications from districts in rural America and in states that had not shared in the Race to the Top bounty before. But whether the ultimate winners, which will be announced this month, will be…

  10. Top 12 Web Resources for 2012

    ERIC Educational Resources Information Center

    Gonzales, Lisa; Vodicka, Devin

    2012-01-01

    In this article, the authors describe some of the top websites recommended by colleagues for the Association of California School Administrators. The Top 12 for 2012 are: (1) Facebook (facebook.com); (2) Twitter (twitter.com); (3) Tungle (tungle.me); (4) FCMAT (fcmat.org); (5) YouSendIt (yousendit.com); (6) Slideshare (slideshare.net); (7) QR…

  11. Controlling Severe Curly Top in Sugarbeets

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Controlling curly top in sugarbeet has been industry priority in the western United States since the 1920s. Curly top is a virus disease that is vectored by the beet leafhopper. If the beet leafhopper moves into commercial fields early in the season, virus is more likely to be transmitted to sugar...

  12. Pinch Experiments in a Table Top Generator

    SciTech Connect

    Pavez, Cristian; Moreno, Jose; Soto, Leopoldo; Tarifeno, Ariel

    2009-01-21

    The design and construction of a table top multipurpose capacitor bank of hundred of Joules and hundred of kiloAmperes conceived to be used in small scale Z-pinch experiments is reported. A recent result on a Z-pinch gas embedded discharge using hollow conical electrodes done in a similar table top generator is also presented.

  13. Search for top quark at Fermilab Collider

    SciTech Connect

    Sliwa, K.; The CDF Collaboration

    1991-10-01

    The status of a search for the top quark with Collider Detector at Fermilab (CDF), based on a data sample recorded during the 1988--1989 run is presented. The plans for the next Fermilab Collider run in 1992--1993 and the prospects of discovering the top quark are discussed. 19 refs., 4 figs., 2 tabs.

  14. World average top-quark mass

    SciTech Connect

    Glenzinski, D.; /Fermilab

    2008-01-01

    This paper summarizes a talk given at the Top2008 Workshop at La Biodola, Isola d Elba, Italy. The status of the world average top-quark mass is discussed. Some comments about the challanges facing the experiments in order to further improve the precision are offered.

  15. Physics of the top quark at CDF

    SciTech Connect

    Vejcik, S.; CDF Collaboration

    1997-07-01

    Measurements of Top quark properties with the CDF detector are reported. The production cross section and mass provide a consistent picture of the Top quark as described by the Standard Model. Initial studies of other properties such as estimates of branching ratios are also reported.

  16. Tools for top physics at D0

    SciTech Connect

    Harel, Amnon

    2008-07-01

    Top quark measurements rely on the jet energy calibration and often on b-quark identification. We discuss these and other tools and how they apply to top quark analyses at D0. In particular some of the nuances that result from D0's data driven approach to these issues are presented.

  17. Top Quark Pair Production at the Tevatron

    SciTech Connect

    Nielsen, Jason

    2005-05-17

    The measurement of the top quark pair production crosssection inproton-antiproton collisions at 1.96 TeV is a test ofquantumchromodynamics and could potentially be sensitive to newphysics beyondthe standard model. I report on the latest t-tbarcross section resultsfrom the CDF and DZero experiments in various finalstate topologies whicharise from decays of top quark pairs.

  18. Hiding Solar-Array Bus Bars

    NASA Technical Reports Server (NTRS)

    Hufnagel, W. F.

    1983-01-01

    End terminals mounted under cells, maximizing usable illuminated area. Reconfigured solar panel bus bars placed under cells, reducing portion of module area not occupied by active silicon. Underside of last cell in string of cells serves as contact for positive bus. Negative tab of last cell in string is wrapped around from top of cell. Tabs are connected to output boards mounted under cells.

  19. Food dehydration by solar energy.

    PubMed

    Bolin, H R; Salunkhe, D K

    1982-01-01

    Solar driers that are currently being investigated for drying of agricultural products can be divided into two major divisions, depending upon how they transfer the incident solar energy to the product to be dried. These two divisions are direct and indirect drying, with some work also being done on combination drying procedures. In direct solar driers, the product to be dried is usually either inside a tent, greenhouse, or a glass-topped box, where the product to be dried is heated by the direct rays from the sun and the moist air is removed by ambient wind movement. These dryers do accelerate moisture loss rate and the product is usually safe from inclement weather. These dryers usually do not require fans for forced air circulation. With indirect drying, the opposite is true, where most require powered fans for forced air circulation. With this type of dryer, both flatplate and inflated tube solar heat absorbers are used, with each offering certain advantages. Also, combination dryers have been built that utilize both direct and indirect principles. Product evaluation of solar dried foods indicate that in most cases the physical properties, flavor, and vitamin A and C retention were as good as, or better than, conventional dried foods. The economics of the solar systems indicate that most drying procedures are economically feasible for use in small-scale operations only, with the exception of grain drying.

  20. Solar Simulator

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Oriel Corporation's simulators have a high pressure xenon lamp whose reflected light is processed by an optical system to produce a uniform solar beam. Because of many different types of applications, the simulators must be adjustable to replicate many different areas of the solar radiation spectrum. Simulators are laboratory tools for such purposes as testing and calibrating solar cells, or other solar energy systems, testing dyes, paints and pigments, pharmaceuticals and cosmetic preparations, plant and animal studies, food and agriculture studies and oceanographic research.

  1. Solar Physics

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    2000-01-01

    The areas of emphasis are: (1) develop theoretical models of the transient release of magnetic energy in the solar atmosphere, e.g., in solar flares, eruptive prominences, coronal mass ejections, etc.; (2) investigate the role of the Sun's magnetic field in the structuring of solar corona by the development of three-dimensional numerical models that describe the field configuration at various heights in the solar atmosphere by extrapolating the field at the photospheric level; (3) develop numerical models to investigate the physical parameters obtained by the ULYSSES mission; (4) develop numerical and theoretical models to investigate solar activity effects on the solar wind characteristics for the establishment of the solar-interplanetary transmission line; and (5) develop new instruments to measure solar magnetic fields and other features in the photosphere, chromosphere transition region and corona. We focused our investigation on the fundamental physical processes in solar atmosphere which directly effect our Planet Earth. The overall goal is to establish the physical process for the Sun-Earth connections.

  2. TOP500 Supercomputers for June 2002

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2002-06-20

    19th Edition of TOP500 List of World's Fastest Supercomputers Released MANNHEIM, Germany; KNOXVILLE, Tenn.;&BERKELEY, Calif. In what has become a much-anticipated event in the world of high-performance computing, the 19th edition of the TOP500 list of the worlds fastest supercomputers was released today (June 20, 2002). The recently installed Earth Simulator supercomputer at the Earth Simulator Center in Yokohama, Japan, is as expected the clear new number 1. Its performance of 35.86 Tflop/s (trillions of calculations per second) running the Linpack benchmark is almost five times higher than the performance of the now No.2 IBM ASCI White system at Lawrence Livermore National Laboratory (7.2 Tflop/s). This powerful leap frogging to the top by a system so much faster than the previous top system is unparalleled in the history of the TOP500.

  3. Thermionic topping of electric power plants

    NASA Technical Reports Server (NTRS)

    Britt, E. J.; Fitzpatrick, G. O.; Rasor, N. S.

    1975-01-01

    The most likely use of thermionic conversion is in the form of a topping cycle combined with a steam-turbogenerator plant. A specific reference system is chosen in which the thermionic topping cycle occurs in thermionic heat exchangers referred to as large, modular thermionic units to which heat is transferred from a separate heat source and which reject their heat to a conventional steam turboelectric system. Results of analysis show that the performance and cost criteria for practical thermionic topping of large electric power plants are well within the reach of demonstrated and foreseeable converter capabilities. Thermionic topping has many significant advantages over unconventional cycles proposed for topping applications, including level of demonstrated and projected performance and lifetime, development time, and design simplicity.

  4. Protein Identification Using Top-Down

    SciTech Connect

    Liu, Xiaowen; Sirotkin, Yakov; Shen, Yufeng; Anderson, Gordon A.; Tsai, Yi-Hsuan S.; Ting, Ying S.; Goodlett, David R.; Smith, Richard D.; Bafna, Vineet; Pevzner, Pavel A.

    2012-06-01

    In the last two years, due to advances in protein separation and mass spectrometry, top-down mass spectrometry moved from analyzing single proteins to analyzing complex samples and identifying hundreds and even thousands of proteins. However, computational tools for database search of top-down spectra against protein databases are still in infancy. We describe MS-Align+, a fast algorithm for top-down protein identification based on spectral alignment that enables searches for unexpected post-translational modifications (PTMs). We also propose a method for evaluating statistical significance of top-down protein identifications and further benchmark MS-Align+ along with PIITA, ProSightPTM and SEQUEST, which were previously used for top-down MS/MS database searches. We demonstrate that MS-Align+ and PIITA significantly increase the number of identified proteins as compared to ProSightPTM and SEQUEST.

  5. Measurement of solar radiation at the Earth's surface

    NASA Technical Reports Server (NTRS)

    Bartman, F. L.

    1982-01-01

    The characteristics of solar energy arriving at the surface of the Earth are defined and the history of solar measurements in the United States presented. Radiation and meteorological measurements being made at solar energy meteorological research and training sites and calibration procedures used there are outlined. Data illustrating the annual variation in daily solar radiation at Ann Arbor, Michigan and the diurnal variation in radiation at Albuquerque, New Mexico are presented. Direct normal solar radiation received at Albuquerque is contrasted with that received at Maynard, Massachusetts. Average measured global radiation for a period of one year for four locations under clear skies, 50% cloud cover, and 100% cloud cover is given and compared with the solar radiation at the top of the atmosphere. The May distribution of mean daily direct solar radiation and mean daily global solar radiation over the United States is presented. The effects of turbidity on the direct and circumsolar radiation are shown.

  6. Measurements and searches with top quarks

    SciTech Connect

    Peters, Reinhild Yvonne

    2008-08-01

    In 1995 the last missing member of the known families of quarks, the top quark, was discovered by the CDF and D0 experiments at the Tevatron, a proton-antiproton collider at Fermilab near Chicago. Until today, the Tevatron is the only place where top quarks can be produced. The determination of top quark production and properties is crucial to understand the Standard Model of particle physics and beyond. The most striking property of the top quark is its mass--of the order of the mass of a gold atom and close to the electroweak scale--making the top quark not only interesting in itself but also as a window to new physics. Due to the high mass, much higher than of any other known fermion, it is expected that the top quark plays an important role in electroweak symmetry breaking, which is the most prominent candidate to explain the mass of particles. In the Standard Model, electroweak symmetry breaking is induced by one Higgs field, producing one additional physical particle, the Higgs boson. Although various searches have been performed, for example at the Large Electron Positron Collider (LEP), no evidence for the Higgs boson could yet be found in any experiment. At the Tevatron, multiple searches for the last missing particle of the Standard Model are ongoing with ever higher statistics and improved analysis techniques. The exclusion or verification of the Higgs boson can only be achieved by combining many techniques and many final states and production mechanisms. As part of this thesis, the search for Higgs bosons produced in association with a top quark pair (t$\\bar{t}$H) has been performed. This channel is especially interesting for the understanding of the coupling between Higgs and the top quark. Even though the Standard Model Higgs boson is an attractive candidate, there is no reason to believe that the electroweak symmetry breaking is induced by only one Higgs field. In many models more than one Higgs boson are expected to exist, opening even more

  7. Predicting top-of-atmosphere radiance for arbitrary viewing geometries from the visible to thermal infrared

    NASA Astrophysics Data System (ADS)

    Cota, Steve A.; Kalman, Linda S.

    2010-08-01

    In an earlier paper [Cota et al., Proc. SPIE 7087, 1-31 (2008)] we described how The Aerospace Corporation's Parameterized Image Chain Analysis & Simulation SOftware (PICASSO) may be used with a reflectance calibrated input scene, in conjunction with a limited number of runs of AFRL's MODTRAN4 radiative transfer code, to quickly predict the top-of-atmosphere (TOA) radiance received by an earth viewing sensor, for any arbitrary combination of solar and sensor elevation angles. In the present paper, we extend the method to the short and midwave IR, where reflected solar and emitted thermal radiation both contribute to the TOA radiance received by a downlooking sensor.

  8. Discovery of single top quark production

    SciTech Connect

    Gillberg, Dag

    2009-04-01

    The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking - the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of single top quark production. An analysis is performed using 2.3 fb-1 of data recorded by the D0 detector at the Fermilab Tevatron Collider at centre-of-mass energy √s = 1.96 TeV. Boosted decision trees are used to isolate the single top signal from background, and the single top cross section is measured to be σ(p$\\bar{p}$ → tb + X, tqb + X) = 3.74-0.74+0.95 pb. Using the same analysis, a measurement of the amplitude of the CKM matrix element Vtb, governing how top and b quarks mix, is also performed. The measurement yields: |V{sub tb}|f1L| = 1.05 -0.12+0.13, where f1L is the left-handed Wtb coupling. The separation of signal from background is improved by combining the boosted decision trees with two other multivariate techniques. A new cross section measurement is performed, and the significance for the excess over the predicted background exceeds 5

  9. Measurement of the top quark mass

    SciTech Connect

    Blusk, Steven R.

    1998-05-01

    The first evidence and subsequent discovery of the top quark was reported nearly 4 years ago. Since then, CDF and D0 have analyzed their full Run 1 data samples, and analysis techniques have been refined to make optimal use of the information. In this paper, we report on the most recent measurements of the top quark mass, performed by the CDF and D0 collaborations at the Fermilab Tevatron. The CDF collaboration has performed measurements of the top quark mass in three decay channels from which the top quark mass is measured to be 175.5 {+-} 6.9 GeV=c{sup 2}. The D0 collaboration combines measurements from two decay channels to obtain a top quark mass of 172.1 {+-} 7.1 GeV/c{sup 2}. Combining the measurements from the two experiments, assuming a 2 GeV GeV/c{sup 2} correlated systematic uncertainty, the measurement of the top quark mass at the Tevatron is 173.9 {+-} 5.2 GeV/c{sup 2}. This report presents the measurements of the top quark mass from each of the decay channels which contribute to this measurement.

  10. The Top Quark, QCD, And New Physics.

    DOE R&D Accomplishments Database

    Dawson, S.

    2002-06-01

    The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup+}e{sup -}+ t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup+}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.

  11. Solar Eclipse

    Atmospheric Science Data Center

    2013-04-16

    ... a solar eclipse where an observer on Earth can watch the Moon's shadow obscure more than 90% the Sun's disk, the Multiangle Imaging ... total solar eclipse of November 23, 2003. The path of the Moon's umbral shadow began in the Indian Ocean in the far Southern Hemisphere, ...

  12. Solar Eclipse

    Atmospheric Science Data Center

    2013-04-19

    ...   View Larger Image On June 10, 2002 the Moon obscured the central portion of the solar disk in a phenomenon known as an ... in which 99.6 percent of the solar disk was shadowed by the Moon, was situated in the central Pacific Ocean. Since there are no populated ...

  13. Solar Sprint

    ERIC Educational Resources Information Center

    Tabor, Richard; Anderson, Stephen

    2007-01-01

    In the "Solar Sprint" activity, students design, test, and race a solar-powered car built with Legos. The use of ratios is incorporated to simulate the actual work of scientists and engineers. This method encourages fourth-grade students to think about multiple variables and stimulates their curiosity when an activity doesn't come out as…

  14. Solar Technologies

    ERIC Educational Resources Information Center

    von Hippel, Frank; Williams, Robert H.

    1975-01-01

    As fossil fuels decrease in availability and environmental concerns increase, soalr energy is becoming a potential major energy source. Already solar energy is used for space heating in homes. Proposals for solar-electric generating systems include land-based or ocean-based collectors and harnessing wind and wave power. Photosynthesis can also…

  15. Tevatron Top-Quark Combinations and World Top-Quark Mass Combination

    SciTech Connect

    Peters, Reinhild Yvonne

    2014-11-04

    Almost 20 years after its discovery, the top quark is still an interesting particle, undergoing precise investigation of its properties. For many years, the Tevatron proton antiproton collider at Fermilab was the only place to study top quarks in detail, while with the recent start of the LHC proton proton collider a top quark factory has opened. An important ingredient for the full understanding of the top quark is the combination of measurements from the individual experiments. In particular, the Tevaton combinations of single top-quark cross sections, the ttbar production cross section, the W helicity in top-quark decays as well as the Tevatron and the world combination of the top-quark mass are discussed.

  16. Precision Determination of the Top Quark Mass

    SciTech Connect

    Movilla Fernandez, Pedro A.; /LBL, Berkeley

    2007-05-01

    The CDF and D0 collaborations have updated their measurements of the mass of the top quark using proton-antiproton collisions at {radical}s = 1.96 TeV produced at the Tevatron. The uncertainties in each of the top-antitop decay channels have been reduced. The new Tevatron average for the mass of the top quark based on about 1 fb{sup -1} of data per experiment is 170.9 {+-} 1.8 GeV/c{sup 2}.

  17. Single Top Quark Measurements at the Tevatron

    SciTech Connect

    Ronzani, Manfredi

    2014-12-01

    This paper reports the most recent measurements of single top quark production performed by CDF and D0 collaborations in proton-antiproton collisions at Tevatron. Events are selected in the lepton+jets final state by CDF and D0 and in the missing transverse energy plus jets final state by CDF. The small single top signal in s-channel, t-channel and inclusive s+t channel is separated from the large background by using different multivariate techniques. We also present the most recent results on extraction of the CKM matrix element $|V_{tb}|$ from the single top quark cross section.

  18. Top quark mass measurement at the Tevatron

    SciTech Connect

    Guimaraes da Costa, Joao; /Harvard U.

    2004-12-01

    The authors report on the latest experimental measurements of the top quark mass by the CDF and D0 Collaborations at the Fermilab Tevatron. They present a new top mass measurement using the t{bar t} events collected by the D0 Collaboration in Run I between 1994 and 1996. This result is combined with previous measurements to yield a new world top mass average. They also describe several preliminary results using up to 193 pb{sup -1} of t{bar t} events produced in {bar p}p collisions at {radical}s = 1.96 TeV during the Run II of the Tevatron.

  19. Top quark properties from the Tevatron

    SciTech Connect

    Klute, Markus; /MIT, LNS

    2006-05-01

    This report describes latest measurements and studies of top quark properties from the Tevatron in Run II with an integrated luminosity of up to 750 pb{sup -1}. Due to its large mass of about 172 GeV/c{sup 2}, the top quark provides a unique environment for tests of the Standard Model and is believed to yield sensitivity to new physics beyond the Standard Model. With data samples of close to 1 fb{sup -1} the CDF and D0 collaborations at the Tevatron enter a new area of precision top quark measurements.

  20. Radiation effects on solar cells: experiments, models, and simulations: DLTS vs. SRIM for trap data

    NASA Astrophysics Data System (ADS)

    Fedoseyev, Alex; Turowski, Marek; Bald, Timothy; Raman, Ashok; Warner, Jeffrey H.

    2013-09-01

    A predictive computational approach that limits use of DLTS experiments is presented, developed using the experimental data and proposed physics based models. Three-dimensional NanoTCAD simulations are used for physicsbased prediction of space radiation effects in III-V solar cells, and validated with experimentally measured characteristics of a p+n GaAs solar cell with AlGaAs window. The computed dark and illuminated I-V curves as well as corresponding performance parameters matched very well experimental data for 2 MeV proton irradiation at various fluences. We analyze the role of majority vs. minority and deep vs. shallow carrier traps in the solar cell performance degradation. The traps/defects parameters used in the simulations were derived from Deep Level Transient Spectroscopy (DLTS) data obtained at NRL. It was noticed that the degradation caused by deep traps observed in single-trap numerical tests exhibit a very similar trend to the degradation caused by a full spectrum of defect traps, but to a lesser degree. This led to the development of a method to accurately simulate the degradation of a solar cell by using only a single deep level defect whose density is calculated by the Stopping and Range of Ions in Matter (SRIM) code. Using SRIM, we calculated the number of vacancies produced by 2 MeV proton irradiation for fluences ranging from 6x1010 cm-2 to 5x1012 cm-2. Based on the SRIM results, we applied trap models in NanoTCAD and performed full I-V simulations from which the amount of degradation of performance parameters (Isc, Voc, Pmax) was calculated. The physics-based models using SRIM allowed obtaining good match with experimental data.

  1. Purification of metalorganic compounds for solar cells. Final report, October 1, 1980-March 21, 1982

    SciTech Connect

    Manasevit, H.M.; Yang, J.J.; Simpson, W.I.; Wang, W.I.; Zehr, S.W.

    1982-08-01

    During this program, several sources of trimethylgallium (TMG) and AsH/sub 3/-in-H/sub 2/ were evaluated for use as source materials for epitaxial growth of GaAs solar cells using the metalorganic chemical vapor deposition(MO-CVD) process. Screening of the various source combinations was done primarily on the basis of room and liquid nitrogen temperature Hall measurements of background doping levels and carrier mobilities in unintentionally doped MO-CVD-grown films. Initial studies evaluated the quality of AsH/sub 3/-in-H/sup 2/ tanks. Solar cell structures were grown in a second deposition system used in the past for growth of solar cells, but only after undoped GaAs films were produced in that system at various temperatures to determine its background level. These undoped films were grown using TMG and AsH/sub 3/-in-H/sub 2/. The background doping was found to be higher in the solar cell system than in the high purity system. Later in the program, work was initiated to explore effects of impurities associated with trimethylaluminum (TMA) source mateial. A major finding of this work was an apparent trend toward increasing AlGaAs material quality with increasing MO-CVD growth temperature up to at least 825/sup 0/C. For these films, the measure of quality was the relative photoluminescence intensity of the material, which increased with increasing growth temperature in the range 750 to 825/sup 0/C. Accompanying the improved photoluminescence efficiency was a marked increase in background doping level and virtually unchanging mobility with increasing growth temperature.

  2. Venus wind map at cloud top level with the MTR/THEMIS visible spectrometer, I: Instrumental performance and first results

    NASA Astrophysics Data System (ADS)

    Gaulme, Patrick; Schmider, François-Xavier; Grec, Catherine; López Ariste, Arturo; Widemann, Thomas; Gelly, Bernard

    2008-08-01

    Solar light gets scattered at cloud top level in Venus' atmosphere, in the visible range, which corresponds to the altitude of 67 km. We present Doppler velocity measurements performed with the high resolution spectrometer MTR of the Solar telescope THEMIS (Teide Observatory, Canary Island) on the sodium D2 solar line (5890A˚). Observations lasted only 49 min because of cloudy weather. However, we could assess the instrumental velocity sensitivity, 31ms-1 per pixel of 1 arcsec, and give a value of the amplitude of zonal wind at equator at 151±16ms-1.

  3. Top Five Lifestyle Changes to Reduce Cholesterol

    MedlinePlus

    Top 5 lifestyle changes to improve your cholesterol Lifestyle changes can help reduce cholesterol, keep you off cholesterol-lowering medications or enhance the effect of your medications. Here are five lifestyle ...

  4. Higgs Effects in Top Quark Pair Production

    SciTech Connect

    Kuhn, J.H.

    2003-06-13

    Top quark production in p{bar p} and e{sup +}e{sup -} collisions is enhanced by the exchange of a Higgs boson. The enhancement factors are calculated in the threshold region using the Greens function method.

  5. Top Quark Physics at the Tevatron

    SciTech Connect

    Jung, Andreas W.

    2015-05-21

    An overview of recent top quark measurements using the full Run II data set of CDF or D0 at the Tevatron is presented. Results are complementary to the ones at the LHC. Recent measurements of the production cross section of top quarks in strong and electroweak production and of top quark production asymmetries are presented. The latter includes the measurement of the tt-bar production asymmetry by D0 in the dilepton decay channel. Within their uncertainties the results from all these measurements agree with their respective Standard Model expectation. Finally latest updates on measurements of the top quark mass are discussed, which at the time of the conference are the most precise determinations.

  6. Wind Energy Program: Top 10 Program Accomplishments

    SciTech Connect

    2009-01-18

    Brochure on the top accomplishments of the Wind Energy Program, including the development of large wind machines, small machines for the residential market, wind tunnel testing, computer codes for modeling wind systems, high definition wind maps, and successful collaborations.

  7. Dark decay of the top quark

    SciTech Connect

    Kong, Kyoungchul; Lee, Hye -Sung; Park, Myeonghun

    2014-04-01

    We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 σ deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t → b W + Z's. This is the same as the dominant top quark decay (t → b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. In addition, we discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.

  8. Top partner probes of extended Higgs sectors

    NASA Astrophysics Data System (ADS)

    Kearney, John; Pierce, Aaron; Thaler, Jesse

    2013-08-01

    Natural theories of the weak scale often include fermionic partners of the top quark. If the electroweak symmetry breaking sector contains scalars beyond a single Higgs doublet, then top partners can have sizable branching ratios to these extended Higgs sector states. In fact, top partner decays may provide the most promising discovery mode for such scalars, especially given the large backgrounds to direct and associated production. In this paper, we present a search strategy for top partner decays to a charged Higgs boson and a bottom quark, focusing on the case where the charged Higgs dominantly decays to third-generation quarks to yield a multi- b final state. We also discuss ways to extend this search to exotic neutral scalars decaying to bottom quark pairs.

  9. Top decays and mass with CDF

    SciTech Connect

    Barbaro-Galtieri, A.; CDF Collaboration

    1996-06-01

    The authors report preliminary results on top quark decays and measurements of the top mass recently obtained by the CDF collaboration, using a data sample of about 110 pb{sup {minus}1} collected at the Tevatron collider. Upper limits for non Standard model top decays into W + q (non b quark), Z + q and {gamma} + q are given. Top mass measurements are obtained in three topologies for t{anti t} production and decay into W b: lepton + {ge} 4 jets, di-lepton and all hadronic final states. The most precise measurement is obtained in the lepton + {ge} 4 jets topology using 34 events which have at least one jet tagged by the SVX or SLT b-tagging algorithms and a good constrained kinematics fit.

  10. Giving top quark effective operators a boost

    NASA Astrophysics Data System (ADS)

    Englert, Christoph; Moore, Liam; Nordström, Karl; Russell, Michael

    2016-12-01

    We investigate the prospects to systematically improve generic effective field theory-based searches for new physics in the top sector during LHC run 2 as well as the high luminosity phase. In particular, we assess the benefits of high momentum transfer final states on top EFT-fit as a function of systematic uncertainties in comparison with sensitivity expected from fully-resolved analyses focusing on t t bar production. We find that constraints are typically driven by fully-resolved selections, while boosted top quarks can serve to break degeneracies in the global fit. This demystifies and clarifies the importance of high momentum transfer final states for global fits to new interactions in the top sector from direct measurements.

  11. Best of "Earth As Art" -- Top Five

    NASA Video Gallery

    Counting down the Top Five Earth As Art images, as voted on by the public. Landsat has been collecting data of the Earth's surface since 1972. Some of the images are visually striking, and they hav...

  12. Green Power Partnership Top Partner Rankings

    EPA Pesticide Factsheets

    EPA's Green Power Partnership is a voluntary program designed to reduce the environmental impact of electricity generation by promoting renewable energy. Top Partner Rankings highlight the annual green power use of leading Green Power Partners.

  13. Green Power Partnership National Top 100

    EPA Pesticide Factsheets

    The U.S. EPA's Green Power Partnership is a voluntary program designed to reduce the environmental impact of electricity generation by promoting renewable energy. The National Top 100 lists the largest green power users within the Green Power Partnership.

  14. Top and higgs physics at the Tevatron

    SciTech Connect

    Pierre Savard

    2002-12-23

    We present a summary of our experimental understanding of the top quark and discuss the significant improvements expected in Run II at the Fermilab Tevatron Collider. We also discuss prospects for a Higgs boson discovery at the Tevatron.

  15. Review of recent top quark measurements

    SciTech Connect

    Heinson, A.P.; /UC, Riverside

    2004-11-01

    At the Tevatron Collider at Fermilab, a large number of top quarks have been produced in the ongoing run. The CDF and D0 collaborations have made first measurements of the t{bar t} cross section in several decay channels, and have measured the top quark mass. In addition, they have set new limits on the cross sections for single top quark production, and have started to measure some of the properties of the top quark via studies of its decays. This paper summarizes the status of these measurements and discusses where they are heading in the next few years. The paper is based on a talk I gave at the Rencontres du Vietnam in Hanoi, August 2004; the results have been updated to show the latest values and new measurements.

  16. Solar ponds

    SciTech Connect

    Jayadev, T.S.; Edesess, M.

    1980-04-01

    This report first describes the different types of solar ponds including the nonconvecting salt gradient pond and various saltless pond designs. It then discusses the availability and cost of salts for salt gradient ponds, and compares the economics of salty and saltless ponds as a function of salt cost. A simple computational model is developed to approximate solar pond performance. This model is later used to size solar ponds for district heating and industrial process heat applications. For district heating, ponds are sized to provide space conditioning for a group of homes, in different regions of the United States. Size requirements is on the order of one acre for a group of 25 to 50 homes. An economic analysis is performed of solar ponds used in two industrial process heat applications. The analysis finds that solar ponds are competitive when conventional heat sources are priced at $5 per million Btu and expected to rise in price at a rate of 10% per year. The application of solar ponds to the generation of electricity is also discussed. Total solar pond potential for displacing conventional energy sources is estimated in the range of from one to six quadrillion Btu per year in the near and intermediate future.

  17. Tools for top physics at CDF

    SciTech Connect

    Palencia, E.; /Fermilab

    2008-07-01

    The authors describe here the different tools used for top physics analysis in the CDF Collaboration. In particular, they discuss how the jet energy scale, lepton identification, b tagging algorithms and the neural networks help to improve the signal to background ratio of the top sample in some cases and to reduce the dominant uncertainties in other. Results using each one of these tools are also presented.

  18. The Discovery of the Top Quark

    DOE R&D Accomplishments Database

    Sinervo, P.K.

    1995-12-01

    The top quark and the Higgs boson are the heaviest elementary particles predicted by the standard model. The four lightest quark flavours, the up, down, strange and charm quarks, were well-established by the mid-1970's. The discovery in 1977 of the {Tau} resonances, a new family of massive hadrons, required the introduction of the fifth quark flavour. Experimental and theoretical studies have indicated that this quark also has a heavier partner, the top quark.

  19. Solar pruritus.

    PubMed

    Bech-Thomsen, N; Thomsen, K

    1995-11-01

    A case of solar pruritus is reported. Severe pruritus of the back, shoulders and upper lateral aspects of the arms, without any eruption, developed in a 28-year-old outdoor worker during 4 to 6 weeks of intensive solar exposure. The pruritus was intense and described as a burning sensation deep in the skin. Only a few excoriations and slight xerosis were found. Solar pruritus or brachioradial pruritus is a condition primarily seen in Caucasian people living in the tropics or subtropics. Previously the disease has only been reported once outside these areas.

  20. Solar Two

    SciTech Connect

    Not Available

    1998-04-01

    Solar Two is a concentrating solar power plant that can supply electric power on demand to the local utility, Southern California Edison Company. It can do so because it operates not only during sunny parts of the day, but it can store enough thermal energy from the sun to operate during cloudy periods and after dark, for up to three hours, at its rated output of 10 megawatts (MW). For the first time ever, a utility scale solar power plant can supply electricity when the utility needs it most, to satisfy the energy requirements of its customers.

  1. Solar energy: principles and possibilities.

    PubMed

    Rhodes, Christopher J

    2010-01-01

    As the world faces an impending dearth of fossil fuels, most immediately oil, alternative sources of energy must be found. 174 PW worth of energy falls onto the top of the Earth's atmosphere in the form of sunlight which is almost 10,000 times the total amount of energy used by humans on Earth, as taken from all sources, oil, coal, natural gas, nuclear and hydroelectric power combined. If even a fraction of this could be harvested efficiently, the energy crunch could in principle be averted. Various means for garnering energy from the Sun are presented, including photovoltaics (PV), thin film solar cells, quantum dot cells, concentrating PV and thermal solar power stations, which are more efficient in practical terms. Finally the prospects of space based (satellite) solar power are considered. The caveat is that even if the entire world electricity budget could be met using solar energy, the remaining 80% of energy which is not used as electricity but thermal power (heat) still needs to be found in the absence of fossil fuels. Most pressingly, the decline of cheap plentiful crude oil (peak oil) will not find a substitution via solar unless a mainly electrified transportation system is devised and it is debatable that there is sufficient time and conventional energy remaining to accomplish this. The inevitable contraction of transportation will default a deconstruction of the globalised world economy into that of a system of localised communities.

  2. Solar radiation assembly

    SciTech Connect

    Boozer, S.D.

    1987-04-21

    A Solar transmission system is described comprising at least one radiation permeable assembly. A light aperture is adapted to be mounted in the envelope of a building. The light aperture has at least one layer of first glazing forming part of the building envelope. A generally rectangular frame is supported on the building and around an outer side of the aperture. A layer of second glazing comprises an outer facing of the frame. Ventilation means at the top and bottom of the frame, includes means for enabling air flow through the frame, and includes means for inhibiting rain from entering the frame. Support means connectible between the frame and the building, enable the frame to be moved away from the building, whereby the glazing of the light aperture may be made accessible.

  3. Measurement of top quark polarisation in t-channel single top quark production

    DOE PAGES

    Khachatryan, Vardan

    2016-04-13

    Our first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1. A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. Furthermore, a differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is usedmore » to extract a top quark spin asymmetry of 0.26 ± 0.03 (stat) ± 0.10 (syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44.« less

  4. Measurement of top quark polarisation in t-channel single top quark production

    SciTech Connect

    Khachatryan, Vardan

    2016-04-13

    Our first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1. A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. Furthermore, a differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of 0.26 ± 0.03 (stat) ± 0.10 (syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44.

  5. Measurement of top quark polarisation in t-channel single top quark production

    NASA Astrophysics Data System (ADS)

    Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Flechl, M.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Knünz, V.; König, A.; Krammer, M.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Cornelis, T.; de Wolf, E. A.; Janssen, X.; Knutsson, A.; Lauwers, J.; Luyckx, S.; van de Klundert, M.; van Haevermaet, H.; van Mechelen, P.; van Remortel, N.; van Spilbeeck, A.; Abu Zeid, S.; Blekman, F.; D'Hondt, J.; Daci, N.; de Bruyn, I.; Deroover, K.; Heracleous, N.; Keaveney, J.; Lowette, S.; Moreels, L.; Olbrechts, A.; Python, Q.; Strom, D.; Tavernier, S.; van Doninck, W.; van Mulders, P.; van Onsem, G. P.; van Parijs, I.; Barria, P.; Brun, H.; Caillol, C.; Clerbaux, B.; de Lentdecker, G.; Fasanella, G.; Favart, L.; Grebenyuk, A.; Karapostoli, G.; Lenzi, T.; Léonard, A.; Maerschalk, T.; Marinov, A.; Perniè, L.; Randle-Conde, A.; Seva, T.; Vander Velde, C.; Vanlaer, P.; Yonamine, R.; Zenoni, F.; Zhang, F.; Beernaert, K.; Benucci, L.; Cimmino, A.; Crucy, S.; Dobur, D.; Fagot, A.; Garcia, G.; Gul, M.; McCartin, J.; Ocampo Rios, A. A.; Poyraz, D.; Ryckbosch, D.; Salva, S.; Sigamani, M.; Tytgat, M.; van Driessche, W.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Beluffi, C.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; Ceard, L.; da Silveira, G. G.; Delaere, C.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Jafari, A.; Jez, P.; Komm, M.; Lemaitre, V.; Mertens, A.; Musich, M.; Nuttens, C.; Perrini, L.; Pin, A.; Piotrzkowski, K.; Popov, A.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Beliy, N.; Hammad, G. H.; Aldá Júnior, W. L.; Alves, F. L.; Alves, G. A.; Brito, L.; Correa Martins Junior, M.; Hamer, M.; Hensel, C.; Mora Herrera, C.; Moraes, A.; Pol, M. E.; Rebello Teles, P.; Belchior Batista Das Chagas, E.; Carvalho, W.; Chinellato, J.; Custódio, A.; da Costa, E. M.; de Jesus Damiao, D.; de Oliveira Martins, C.; Fonseca de Souza, S.; Huertas Guativa, L. M.; Malbouisson, H.; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Prado da Silva, W. L.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Ahuja, S.; Bernardes, C. A.; de Souza Santos, A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Moon, C. S.; Novaes, S. F.; Padula, Sandra S.; Romero Abad, D.; Ruiz Vargas, J. C.; Aleksandrov, A.; Hadjiiska, R.; Iaydjiev, P.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Litov, L.; Pavlov, B.; Petkov, P.; Ahmad, M.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Cheng, T.; Du, R.; Jiang, C. H.; Plestina, R.; Romeo, F.; Shaheen, S. M.; Spiezia, A.; Tao, J.; Wang, C.; Wang, Z.; Zhang, H.; Asawatangtrakuldee, C.; Ban, Y.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Xu, Z.; Avila, C.; Cabrera, A.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; Gomez Moreno, B.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Puljak, I.; Ribeiro Cipriano, P. M.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Micanovic, S.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Bodlak, M.; Finger, M.; Finger, M.; Abdelalim, A. A.; Awad, A.; El Sawy, M.; Mahrous, A.; Radi, A.; Calpas, B.; Kadastik, M.; Murumaa, M.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Machet, M.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Zghiche, A.; Antropov, I.; Baffioni, S.; Beaudette, F.; Busson, P.; Cadamuro, L.; Chapon, E.; Charlot, C.; Dahms, T.; Davignon, O.; Filipovic, N.; Florent, A.; Granier de Cassagnac, R.; Jo, M.; Lisniak, S.; Mastrolorenzo, L.; Miné, P.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Ortona, G.; Paganini, P.; Pigard, P.; Regnard, S.; Salerno, R.; Sauvan, J. B.; Sirois, Y.; Strebler, T.; Yilmaz, Y.; Zabi, A.; Agram, J.-L.; Andrea, J.; Aubin, A.; Bloch, D.; Brom, J.-M.; Buttignol, M.; Chabert, E. C.; Chanon, N.; Collard, C.; Conte, E.; Coubez, X.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Goetzmann, C.; Le Bihan, A.-C.; Merlin, J. A.; Skovpen, K.

    2016-04-01

    A first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1. A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. A differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of 0.26 ± 0.03(stat) ± 0.10(syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44. [Figure not available: see fulltext.

  6. Top Quark Properties in Little Higgs Models

    SciTech Connect

    Berger, C.F.; Perelstein, M.; Petriello, F.; /Wisconsin U., Madison

    2005-12-08

    Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetry-breaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 5-10%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including the SM-like top and its heavy counterpart, a TeV-scale ''heavy top'' T. Probing this structure experimentally is quite difficult. While the LHC should be able to discover the T quark, its potential for studying its couplings is limited [3,4]. Direct production of the T will likely be beyond the kinematic reach of the ILC. However, we will show below that the corrections to the gauge couplings of the SM top, induced by its mixing with the T, will be observable at the ILC throughout the parameter range consistent with naturalness. Measuring these corrections will provide a unique window on the top sector of the Little Higgs. Many Little Higgs models have been proposed in the literature. We will consider two examples in this study, the ''Littlest Higgs'' model [5], and its

  7. Simulation of the Mars Surface Solar Spectra for Optimized Performance of Triple-Junction Solar Cells

    NASA Technical Reports Server (NTRS)

    Edmondson, Kenneth M.; Joslin, David E.; Fetzer, Chris M.; King, RIchard R.; Karam, Nasser H.; Mardesich, Nick; Stella, Paul M.; Rapp, Donald; Mueller, Robert

    2007-01-01

    The unparalleled success of the Mars Exploration Rovers (MER) powered by GaInP/GaAs/Ge triple-junction solar cells has demonstrated a lifetime for the rovers that exceeded the baseline mission duration by more than a factor of five. This provides confidence in future longer-term solar powered missions on the surface of Mars. However, the solar cells used on the rovers are not optimized for the Mars surface solar spectrum, which is attenuated at shorter wavelengths due to scattering by the dusty atmosphere. The difference between the Mars surface spectrum and the AM0 spectrum increases with solar zenith angle and optical depth. The recent results of a program between JPL and Spectrolab to optimize GaInP/GaAs/Ge solar cells for Mars are presented. Initial characterization focuses on the solar spectrum at 60-degrees zenith angle at an optical depth of 0.5. The 60-degree spectrum is reduced to 1/6 of the AM0 intensity and is further reduced in the blue portion of the spectrum. JPL has modeled the Mars surface solar spectra, modified an X-25 solar simulator, and completed testing of Mars-optimized solar cells previously developed by Spectrolab with the modified X-25 solar simulator. Spectrolab has focused on the optimization of the higher efficiency Ultra Triple-Junction (UTJ) solar cell for Mars. The attenuated blue portion of the spectrum requires the modification of the top sub-cell in the GaInP/GaAs/Ge solar cell for improved current balancing in the triple-junction cell. Initial characterization confirms the predicted increase in power and current matched operation for the Mars surface 60-degree zenith angle solar spectrum.

  8. Solar fuels

    NASA Astrophysics Data System (ADS)

    Viitanen, M.

    1990-12-01

    The aim of this paper is to give a review concerning the storage of solar energy by converting it to chemical energy. This is based on several articles published during the last fifteen years. The methods to convert solar energy to chemical energy, e.g., to produce hydrogen, can be divided into three different methods. The most common one is probably the usage of solar cells; thus the solar energy is first converted into electrical energy and further the water is split electrochemically to produce hydrogen. It could be also done in a photoelectrochemical cell, or simply photochemically. A photobiological system can also be considered as a photochemical system, although it is discussed separately from the photochemical systems. These three last mentioned methods will be discussed in this paper.

  9. Solar Nexus.

    ERIC Educational Resources Information Center

    Murphy, Jim

    1980-01-01

    The design team for the Solar Energy Research Institute (SERI) has pushed the state of the energy art to its current limits for the initial phase, with provisions for foreseeable and even speculative future applications. (Author/MLF)

  10. Solar chulha

    NASA Astrophysics Data System (ADS)

    Jadhao, P. H.; Patrikar, S. R.

    2016-05-01

    The main goal of the proposed system is to transfer energy from sun to the cooking load that is located in the kitchen. The energy is first collected by the solar collector lens system and two curve bars of same radius of curvature are mounted parallel and adjacent to each other at different height the solar collector is clamed on this two bars such that solar collector is exactly perpendicular to sunlight. The topology includes an additional feature which is window in the wall through which the beam is collimated is directed in the of kitchen. The solar energy that is collected is directed by the mirror system into the kitchen, where it is redirected to cooking platform located in the kitchen. The special feature in this system full Indian meal can be made since cooking platform is indoors.

  11. AlGaAs heterojunction lasers

    NASA Astrophysics Data System (ADS)

    Goldstein, B.; Pultz, G. N.; Carlin, D. B.; Slavin, S. E.; Ettenberg, M.

    1988-02-01

    The characterization of 8300 A lasers was broadened, especially in the area of beam quality. Modulation rates up to 2 Gbit/sec at output powers of 20 mW were observed, waveform fidelity was fully adequate for low BER data transmission, and wavefront measurements showed that phase aberrations were less than lamda/50. Also, individually addressable arrays of up to ten contiguous diode lasers were fabricated and tested. Each laser operates at powers up to 30 mW CW in single spatial mode. Shifting the operating wavelength of the basic CSP laser from 8300 A to 8650 A was accomplished by the addition of Si to the active region. Output power has reached 100 mW single mode, with excellent far field wave front properties. Operating life is currently approx. 1000 hrs at 35 mW CW. In addition, laser reliability, for operation at both 8300 A and 8650 A, has profited significantly from several developments in the processing procedures.

  12. AlGaAs heterojunction lasers

    NASA Technical Reports Server (NTRS)

    Goldstein, B.; Pultz, G. N.; Carlin, D. B.; Slavin, S. E.; Ettenberg, M.

    1988-01-01

    The characterization of 8300 A lasers was broadened, especially in the area of beam quality. Modulation rates up to 2 Gbit/sec at output powers of 20 mW were observed, waveform fidelity was fully adequate for low BER data transmission, and wavefront measurements showed that phase aberrations were less than lamda/50. Also, individually addressable arrays of up to ten contiguous diode lasers were fabricated and tested. Each laser operates at powers up to 30 mW CW in single spatial mode. Shifting the operating wavelength of the basic CSP laser from 8300 A to 8650 A was accomplished by the addition of Si to the active region. Output power has reached 100 mW single mode, with excellent far field wave front properties. Operating life is currently approx. 1000 hrs at 35 mW CW. In addition, laser reliability, for operation at both 8300 A and 8650 A, has profited significantly from several developments in the processing procedures.

  13. Solar Pump

    NASA Technical Reports Server (NTRS)

    Pique, Charles

    1987-01-01

    Proposed pump moves liquid by action of bubbles formed by heat of sun. Tube of liquid having boiling point of 100 to 200 degrees F placed at focal axis of cylindrical reflector. Concentrated sunlight boils liquid at focus, and bubbles of vapor rise in tube, carrying liquid along with them. Pressure difference in hot tube sufficient to produce flow in large loop. Used with conventional flat solar heating panel in completely solar-powered heat-storage system.

  14. Solar Cells

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Heat Exchanger Method (HEM) produces high efficiency crystal ingots in an automated well-insulated furnace offering low equipment, labor and energy costs. The "grown" silicon crystals are used to make solar cells, or photovoltaic cells which convert sunlight directly into electricity. The HEM method is used by Crystal Systems, Inc. and was developed under a NASA/Jet Propulsion Laboratory contract. The square wafers which are the result of the process are sold to companies manufacturing solar panels.

  15. Solar energy conversion apparatus

    SciTech Connect

    Nash, S.G.

    1983-10-18

    Solar energy conversion apparatus is disclosed including a housing portion, an energy absorbing portion, a fluid directing portion and a cover portion; the housing portion including a molded plastic pan member including a base section with upwardly extending spaced spacer sections, the pan member including outwardly inclined sidewall sections having spaced inner and outer wall sections with a top section including an outwardly extending flange section and an inwardly extending slotted frame section; the energy absorbing portion including a conductive metal liner member positioned within the housing portion and resting on the upper surfaces of the spacer sections, a conductive metal separator section extending between the liner sidewall sections adjacent the upper ends thereof and enclosing the liner member; the fluid directing portion including a plurality of parallel spaced longitudinal baffle members arranged in a staggered relationship to provide a tortuous fluid path through the apparatus, an inlet opening and an outlet opening to the tortuous path, the baffle members extending upwardly from the liner bottom to the separator section; the cover portion including transparent impact resistant flat and dome members, the edges of the flat member being secured to the top section, the dome member being disposed over the flat member with its edges engaged with the flange section slots, the dome member including flat sections extending upwardly at an angle of 20/sup 0/ to 30/sup 0/ and a convex central section joining the flat sections.

  16. Production and decay of heavy top quarks

    SciTech Connect

    Kauffman, R.P.

    1989-08-01

    Experimental evidence indicates that the top quark exists and has a mass between 50 and 200 GeV/c{sup 2}. The decays of a top quark with a mass in this range are studied with emphasis placed on the mass region near the threshold for production of real W bosons. Topics discussed are: (1) possible enhancement of strange quark production when M{sub W} + m{sub s} < m{sub t} < M{sub W} + m{sub b}; (2) exclusive decays of T mesons to B and B{asterisk} mesons using the non-relativistic quark model; (3) polarization of intermediate W's in top quark decay as a source of information on the top quark mass. The production of heavy top quarks in an e{sup +}e{sup {minus}} collider with a center-of-mass energy of 2 TeV is studied. The effective-boson approximation for photons, Z{sup 0}'s and W's is reviewed and an analogous approximation for interfaces between photons and Z{sup 0}'s is developed. The cross sections for top quark pair production from photon-photon, photon-Z{sup 0}, Z{sup 0}Z{sup 0}, and W{sup +}W{sup {minus}} fusion are calculated using the effective-boson approximation. Production of top quarks along with anti-bottom quarks via {gamma}W{sup +} and Z{sup 0}W{sup +} fusion is studied. An exact calculation of {gamma}e{sup +} {yields} {bar {nu}}t{bar b} is made and compared with the effective-W approximation. 31 refs., 46 figs.

  17. Solar Schematic

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The home shown at right is specially designed to accommodate solar heating units; it has roof planes in four directions, allowing placement of solar collectors for best exposure to the sun. Plans (bottom) and complete working blueprints for the solar-heated house are being marketed by Home Building Plan Service, Portland, Oregon. The company also offers an inexpensive schematic (center) showing how a homeowner only moderately skilled in the use of tools can build his own solar energy system, applicable to new or existing structures. The schematic is based upon the design of a low-cost solar home heating system built and tested by NASA's Langley Research Center; used to supplement a warm-air heating system, it can save the homeowner about 40 percent of his annual heating bill for a modest investment in materials and components. Home Building Plan Service saved considerable research time by obtaining a NASA technical report which details the Langley work. The resulting schematic includes construction plans and simplified explanations of solar heat collection, collectors and other components, passive heat factors, domestic hot water supply and how to work with local heating engineers.

  18. Top Stars: An Opportunity for Educators

    NASA Astrophysics Data System (ADS)

    Kinnison, S. M. P.

    2010-08-01

    Think you're a Top Star? Want to find out what it takes? Learn about NASA's Top Stars contest and how you can participate. Throughout its lifetime, the Hubble Space Telescope has inspired and promoted education. The final Hubble servicing mission in May of this year and the celebration of Hubble's 20th anniversary in 2010 are key mission milestones, and both enrich activities for the 2009 International Year of Astronomy. U.S. formal (K-12 and college) and informal educators are invited to submit their best examples of using NASA's Hubble Space Telescope for science, technology, engineering or mathematics education. Those selected as Top Stars will receive national recognition and awards. Participants will learn about the contest, the recognition and awards, and how to register and save their entries on the Top Stars Web site. Educators are allowed and encouraged to revise, improve and re-submit their entries up to the final deadline of January 2, 2010. The contest is open to individuals and teams of up to four people who are U.S. citizens and are at least 21 years old. NASA and Institute for Global Environmental Strategies (IGES) employees or their contractors are not eligible. IGES is conducting Top Stars with NASA funding and in cooperation with the Space Telescope Science Institute.

  19. Towards the Top with D0

    SciTech Connect

    Deliot, Frederic

    2012-01-01

    The plan of this manuscript follows my research path over the past 10 years: the muon identification and common analysis tools at DØ, the measurement of the inclusive production of W boson decaying into muon and top quark studies. In the first section, I describe my work about muon identification, certification of the standard muon identification criteria, measurement of the muon selection efficiency and about the development of common analysis format and tools. In the second section, I explain how these efficiency measurements can be used to measure the inclusive W boson production cross section in the muon channel. The W ! μν cross section measurement can be seen as a standard candle to establish several analysis pieces that have to be put in place to perform more complex measurements like top quark analyses. In the last section I introduce more extensively the top quark physics at the Tevatron and describe in more details the main analyses in the dilepton channel I was involved in: the measurement of the tt inclusive cross section in the dilepton channel as well as the ratio of cross sections, the measurement of the top quark mass in the dilepton channel, the extraction of the mass from the tt cross section and the Tevatron top quark mass combination. Before concluding, I finish the section with the description of the latest results on the tt charge asymmetry both at the Tevatron and at the LHC.

  20. Port of Galveston Solar Energy Project

    SciTech Connect

    Falcioni, Diane; Cuclis, Alex; Freundlich, Alex

    2014-03-31

    This study on the performance characteristics of existing solar technologies in a maritime environment was funded by an award given to The Port of Galveston (POG) from the U.S. Department of Energy (DOE). The study includes research performed by The Center for Advanced Materials at the University of Houston (UH). The UH researchers examined how solar cell efficiencies and life spans can be improved by examining the performance of a variety of antireflective (AR) coatings mounted on the top of one of the POG’s Cruise Terminals. Supplemental supporting research was performed at the UH laboratories. An educational Kiosk was constructed with a 55” display screen providing information about solar energy, the research work UH performed at POG and real time data from the solar panels located on the roof of the Cruise Terminal. The Houston Advanced Research Center (HARC) managed the project.

  1. Planar multijunction high voltage solar cells

    NASA Astrophysics Data System (ADS)

    Evans, J. C., Jr.; Chai, A. T.; Goradia, C.

    1980-01-01

    Technical considerations, preliminary results, and fabrication details are discussed for a family of high-voltage planar multi-junction (PMJ) solar cells which combine the attractive features of planar cells with conventional or interdigitated back contacts and the vertical multijunction (VMJ) solar cell. The PMJ solar cell is internally divided into many voltage-generating regions, called unit cells, which are internally connected in series. The key to obtaining reasonable performance from this device was the separation of top surface field regions over each active unit cell. Using existing solar cell fabricating methods, output voltages in excess of 20 volts per linear centimeter are possible. Analysis of the new device is complex, and numerous geometries are being studied which should provide substantial benefits in both normal sunlight usage as well as with concentrators.

  2. Top B physics at the LHC.

    PubMed

    Gedalia, Oram; Isidori, Gino; Maltoni, Fabio; Perez, Gilad; Selvaggi, Michele; Soreq, Yotam

    2013-06-07

    In top-pair events where at least one of the tops decays semileptonically, the identification of the lepton charge allows us to tag not only the top quark charge but also that of the subsequent b quark. In cases where the b also decays semileptonically, the charge of the two leptons can be used to probe CP violation in heavy flavor mixing and decays. This strategy to measure CP violation is independent of those adopted so far in experiments, and can already constrain non standard model sources of CP violation with current and near future LHC data. To demonstrate the potential of this method we construct two CP asymmetries based on same-sign and opposite-sign leptons and estimate their sensitivities. This proposal opens a new window for doing precision measurements of CP violation in b and c quark physics via high p(T) processes at ATLAS and CMS.

  3. CDF top quark production and mass

    SciTech Connect

    Incandela, J.; CDF Collaboration

    1995-07-18

    The top search in the dilepton and lepton plus jets channels with the Collider Detector at Fermilab is presented. The analysis uses a 67 pb{sup {minus}1} sample of p{bar p} collisions at 1.8 TeV. A 4.8{sigma} excess of candidate events establishes the existence of the top quark. The t{bar t} production cross section is measured to be {sigma}{sub t{bar t}} = 7.6{sub {minus}2.0}{sup +2.4} pb with branching Br(t {yields} Wb) = 0.87{sub {minus}0.30}{sup +0.13}(stat) {sub {minus}0.11}{sup +0.13}(syst). The measured mass is M{sub top} = 176{plus_minus}8{plus_minus}10 GeV.

  4. The Multiple Mirror Telescope (MMT) top box

    NASA Astrophysics Data System (ADS)

    Blanco, Daniel R.; Janes, Clinton C.; Montgomery, John W.; Ouellette, David B.; Sharp, Frank H.

    1986-01-01

    So named because it resides on top of the focal plane instrument, the MMT top box is a two-level optical bench with many remotely controlled features which can be configured for experimental use of the MMT. It houses the relay optics and television cameras for focusing, coaligning and guiding the six telescopes of the MMT, as well as the integrating sphere, filter wheel, Hartmann mask wheel, and relay optics of the comparison source for instrumental calibration. It also provides a rigid mounting platform for research instruments as well as special fixtures for telescope tests and collimation. In accommodating these tasks the top box incorporates several novel features which may interest designers of other large telescopes.

  5. Point contact silicon solar cells

    NASA Technical Reports Server (NTRS)

    Swanson, R. M.

    1986-01-01

    The construction of a 22.2% efficient single-crystal silicon solar cell fabricated at Stanford University is described. The cell dimensions were 3 x 5 mm and 100 microns thick with a base lifetime of 500 microseconds. The cell featured light trapping between a texturized top surface and a reflective bottom surface, small point contact diffusions, alternating between n-type and p-type in a polka-dot pattern on the bottom surface, and a surface passivation on all surfaces between contact regions.

  6. Wraparound-contact solar cells

    NASA Technical Reports Server (NTRS)

    Baraona, C. R.; Klucher, T. M.; Thornhill, J. W.; Scott-Monck, J.

    1979-01-01

    Positive and negative electrical contacts are on back surface of wraparound-contact solar cell. With both terminals on nonilluminated side, cells can be connected back-to-back, and interconnection of many cells can be automated by using printed-circuit techniques. Cells are made by screen-printing layer of dielectric around edge of cell and extending top contact over dielectric to back surface. Wraparound also facilitates application of transparent covers and encapsulants. Efficiencies of cells are in excess of seventeen percent.

  7. Top2 and Sgs1-Top3 Act Redundantly to Ensure rDNA Replication Termination

    PubMed Central

    Fredsøe, Jacob; Nielsen, Ida; Pedersen, Jakob Madsen; Bentsen, Iben Bach; Lisby, Michael; Bjergbaek, Lotte; Andersen, Anni H

    2015-01-01

    Faithful DNA replication with correct termination is essential for genome stability and transmission of genetic information. Here we have investigated the potential roles of Topoisomerase II (Top2) and the RecQ helicase Sgs1 during late stages of replication. We find that cells lacking Top2 and Sgs1 (or Top3) display two different characteristics during late S/G2 phase, checkpoint activation and accumulation of asymmetric X-structures, which are both independent of homologous recombination. Our data demonstrate that checkpoint activation is caused by a DNA structure formed at the strongest rDNA replication fork barrier (RFB) during replication termination, and consistently, checkpoint activation is dependent on the RFB binding protein, Fob1. In contrast, asymmetric X-structures are formed independent of Fob1 at less strong rDNA replication fork barriers. However, both checkpoint activation and formation of asymmetric X-structures are sensitive to conditions, which facilitate fork merging and progression of replication forks through replication fork barriers. Our data are consistent with a redundant role of Top2 and Sgs1 together with Top3 (Sgs1-Top3) in replication fork merging at rDNA barriers. At RFB either Top2 or Sgs1-Top3 is essential to prevent formation of a checkpoint activating DNA structure during termination, but at less strong rDNA barriers absence of the enzymes merely delays replication fork merging, causing an accumulation of asymmetric termination structures, which are solved over time. PMID:26630413

  8. Top-down vortices developed in a cylindrical annulus cooled on the top.

    PubMed

    Navarro, M C; Herrero, H

    2013-07-01

    In this paper we study the generation of top-down vortices by thermoconvective mechanisms in a cylindrical annulus nonhomogeneously cooled on the top. Assuming axisymmetry we study the structure of the vortices, characterized by a spiral downward motion, similar to that observed in tornadoes generated in supercell storms.

  9. An Efficiency Comparison of MBA Programs: Top 10 versus Non-Top 10

    ERIC Educational Resources Information Center

    Hsu, Maxwell K.; James, Marcia L.; Chao, Gary H.

    2009-01-01

    The authors compared the cohort group of the top-10 MBA programs in the United States with their lower-ranking counterparts on their value-added efficiency. The findings reveal that the top-10 MBA programs in the United States are associated with statistically higher average "technical and scale efficiency" and "scale efficiency", but not with a…

  10. A measurement of the top quark's charge

    SciTech Connect

    Unalan, Zeynep Gunay

    2007-01-01

    The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using ~ 1 fb-1 of data. The data were collected by the CDF detector from proton anti-proton (p$\\bar{p}$) collisions at √s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t → W+b and an exotic event as t → W-b. We find the p-value under the Standard Model hypothesis to be 0.35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2 x Ln(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.

  11. Investigation of ZnSe-coated silicon substrates for GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Huber, Daniel A.; Olsen, Larry C.; Dunham, Glen; Addis, F. William

    1993-01-01

    Studies are being carried out to determine the feasibility of using ZnSe as a buffer layer for GaAs solar cells grown on silicon. This study was motivated by reports in the literature indicating ZnSe films had been grown by metallorganic chemical vapor deposition (MOCVD) onto silicon with EPD values of 2 x 10(exp 5) cm(sup -2), even though the lattice mismatch between silicon and ZnSe is 4.16 percent. These results combined with the fact that ZnSe and GaAs are lattice matched to within 0.24 percent suggest that the prospects for growing high efficiency GaAs solar cells onto ZnSe-coated silicon are very good. Work to date has emphasized development of procedures for MOCVD growth of (100) ZnSe onto (100) silicon wafers, and subsequent growth of GaAs films on ZnSe/Si substrates. In order to grow high quality single crystal GaAs with a (100) orientation, which is desirable for solar cells, one must grow single crystal (100) ZnSe onto silicon substrates. A process for growth of (100) ZnSe was developed involving a two-step growth procedure at 450 C. Single crystal, (100) GaAs films were grown onto the (100) ZnSe/Si substrates at 610 C that are adherent and specular. Minority carrier diffusion lengths for the GaAs films grown on ZnSe/Si substrates were determined from photoresponse properties of Al/GaAs Schottky barriers. Diffusion lengths for n-type GaAs films are currently on the order of 0.3 microns compared to 2.0 microns for films grown simultaneously by homoepitaxy.

  12. Simulation of radiation effects in solar cells: DLTS vs. SRIM for trap data

    NASA Astrophysics Data System (ADS)

    Turowski, Marek; Bald, Timothy; Raman, Ashok; Fedoseyev, Alex; Warner, Jeffrey H.

    2013-03-01

    We present a predictive computational approach that may reduce the need for extensive inputs from Deep Level Transient Spectroscopy (DLTS) experiments. Three-dimensional NanoTCAD simulations are used for physics-based prediction of space radiation effects in a p+n GaAs solar cell with AlGaAs window, and validated with experimental data. The computed dark and illuminated I-V curves, as well as corresponding performance parameters, matched experimental data very well for 2 MeV proton irradiation at various fluence levels. We analyze the role of majority vs. minority and deep vs. shallow carrier traps in the solar cell performance degradation. The defects level parameters used in the simulations were taken from DLTS data obtained at NRL. It was determined from numerical simulations that the degradation of the photovoltaic parameters could be modeled and showed similar trends when a only a single deep level defect was considered compared to a spectrum of defect levels. This led to the development of an alternate method to simulate the degradation of a solar cell by using only a single deep level defect whose density is calculated by the Stopping and Range of Ions in Matter (SRIM) code. Using SRIM, we calculated the number of vacancies produced by 2 MeV proton irradiation for fluence levels ranging from 6x1010 cm-2 to 5x1012 cm-2. Based on the SRIM results, we applied trap models in NanoTCAD and performed I-V simulations from which the degradation of the photovoltaic parameters (Isc, Voc, FF, Pmax) was calculated. The simulations using SRIM-derived defect concentrations showed reasonable agreement with simulations using parameters determined from DLTS.

  13. Internal absorber solar collector

    DOEpatents

    Sletten, Carlyle J.; Herskovitz, Sheldon B.; Holt, F. S.; Sletten, E. J.

    1981-01-01

    Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.

  14. Solar ponds

    NASA Astrophysics Data System (ADS)

    Tabor, H.

    1981-01-01

    The history and current status of salt-gradient non-convecting solar ponds are presented. These ponds are large-area collectors, capable of providing low-cost thermal, mechanical, or electrical energy using low-temperature turbo-generators. The basic theory of salt-gradient solar ponds is sketched; the effects of wind, leakage, and fouling and their constraints on location selection for solar ponds are discussed. The methods of building and filling the ponds, as well as extracting heat from them are explained in detail. Practical operating temperatures of 90 C can be obtained with collection efficiencies between 15% and 25%, demonstrating the practical use of the ponds for heating and cooling purposes, power production, and desalination. A condensed account of solar pond experience in several countries is given. This includes the 150 kW solar pond power station (SPPS) operating in Israel since December, 1979 and a 5000 kW unit currently under development. A study of the economics involved in using the ponds is presented: despite a low conversion efficiency, the SPPS is shown to have applications in many countries.

  15. Top Quark Spin Correlations at the Tevatron

    SciTech Connect

    Head, Tim; /Manchester U.

    2010-07-01

    Recent measurements of the correlation between the spin of the top and the spin of the anti-top quark produced in proton anti-proton scattering at a center of mass energy of {radical}s = 1.96 Tev by the CDF and D0 collaborations are discussed. using up to 4.3 fb{sup -1} of data taken with the CDF and D0 detectors the spin correlation parameter C, the degree to which the spins are correlated, is measured in dileptonic and semileptonic final states. The measurements are found to be in agreement with Standard Model predictions.

  16. Top and Electroweak Measurements at the Tevatron

    SciTech Connect

    Bartos, P.

    2016-01-01

    In this report, we summarize the latest results of the top-quark mass and electroweak measurements from the Tevatron. Since the world combination of top-quark mass measurements was done, CDF and D0 experiments improved the precision of several results. Some of them reach the relative precition below 1% for a single measurement. From the electroweak results, we report on the WW and WZ production cross section, measurements of the weak mixing angle and indirect measurements of W boson mass. The Tevatron results of the weak mixing angle are still the most precise ones of hadron colliders.

  17. Evidence for production of single top quarks

    SciTech Connect

    Abazov, V.M.; Abbott, B.; Abolins, M.; Acharya, B.S.; Adams, M.; Adams, T.; Aguilo, E.; Ahn, S.H.; Ahsan, M.; Alexeev, G.D.; Alkhazov, G.; /St. Petersburg, INP /Michigan U.

    2008-03-01

    We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p{bar p} collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top quark partner that is always produced from strong coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top quark production has been searched for in ever larger datasets. In this analysis, we select events from a 0.9 fb{sup -1} dataset that have an electron or muon and missing transverse energy from the decay of a W boson from the top quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and t{bar t} events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top quark production of {sigma}(p{bar p} {yields} tb + X, tqb + X) = 4.7 {+-} 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}| = 1.31{sub -0.21}{sup +0.25}, where f{sub 1}{sup L} is a generic vector coupling. This model-independent measurement translates into 0.68 < |V{sub tb}| {le} 1 at the 95% C.L. in the standard model.

  18. Evidence for production of single top quarks

    SciTech Connect

    Abazov, V. M.; Alexeev, G. D.; Kalinin, A. M.; Kharzheev, Y. M.; Malyshev, V. L.; Tokmenin, V. V.; Vertogradov, L. S.; Yatsunenko, Y. A.; Abbott, B.; Gutierrez, P.; Hossain, S.; Jain, S.; Rominsky, M.; Severini, H.; Skubic, P.; Strauss, M.; Abolins, M.; Benitez, J. A.; Brock, R.; Dyer, J.

    2008-07-01

    We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron pp collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb{sup -1} data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and tt events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark production of {sigma}(pp{yields}tb+X,tqb+X)=4.7{+-}1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}|=1.31{sub -0.21}{sup +0.25}, where f{sub 1}{sup L} is a generic vector coupling. This model-independent measurement translates into 0.68<|V{sub tb}|{<=}1 at the 95% C.L. in the standard model.

  19. TopN-Pareto Front Search

    SciTech Connect

    Anderson-Cook, Christine M.; Lu, Lu; Burke, Sarah E.

    2016-12-21

    The JMP Add-In TopN-PFS provides an automated tool for finding layered Pareto front to identify the top N solutions from an enumerated list of candidates subject to optimizing multiple criteria. The approach constructs the N layers of Pareto fronts, and then provides a suite of graphical tools to explore the alternatives based on different prioritizations of the criteria. The tool is designed to provide a set of alternatives from which the decision-maker can select the best option for their study goals.

  20. Thermionic Energy Conversion (TEC) topping thermoelectrics

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1981-01-01

    Performance expectations for thermionic and thermoelectric energy conversion systems are reviewed. It is noted that internal radiation effects diminish thermoelectric figures of merit significantly at 1000 K and substantially at 2000 K; the effective thermal conductivity contribution of intrathermoelectric radiative dissipation increases with the third power of temperature. It is argued that a consideration of thermoelectric power generation with high temperature heat sources should include utilization of thermionic energy conversion (TEC) topping thermoelectrics. However TEC alone or TEC topping more efficient conversion systems like steam or gas turbines, combined cycles, or Stirling engines would be more desirable generally.

  1. Measurement of the Top Quark Mass

    SciTech Connect

    Blair, R.E.; Byrum, K.L.; Kovacs, E.; Kuhlmann, S.E.; LeCompte, T.; Nodulman, L.; Breccia, L.; Brunetti, R.; Deninno, M.; Fiori, I.; Mazzanti, P.; Behrends, S.; Bensinger, J.; Blocker, C.; Kirsch, L.; Lamoureux, J.I.; Bonushkin, Y.; Hauser, J.; Lindgren, M.; Amadon, A.; Berryhill, J.; Contreras, M.; Culbertson, R.; Frisch, H.; Grosso-Pilcher, C.; Hohlmann, M.; Cronin-Hennessy, D.; Dittmann, J.R.; Goshaw, A.T.; Khazins, D.; Kowald, W.; Oh, S.H.; Albrow, M.G.; Atac, M.; Beretvas, A.; Berge, J.P.; Biery, K.; Binkley, M.; Buckley-Geer, E.; Byon-Wagner, A.; Chlebana, F.; Cihangir, S.; Cooper, J.; DeJongh, F.; Demina, R.; Derwent, P.F.; Elias, J.E.; Erdmann, W.; Flaugher, B.; Foster, G.W.; Freeman, J.; Geer, S.; Hahn, S.R.; Harris, R.M.; Incandela, J.; Jensen, H.; Joshi, U.; Kennedy, R.D.; Kephart, R.; Lammel, S.; Lewis, J.D.; Limon, P.; Lukens, P.; Maeshima, K.; Marriner, J.P.; Miao, T.; Mukherjee, A.; Nelson, C.; Newman-Holmes, C.; Patrick, J.; Klimenko, S.; Konigsberg, J.; Korytov, A.; Nomerotski, A.; Barone, M.; Bertolucci, S.; Cordelli, M.; DellAgnello, S.; Giromini, P.; Happacher, F.; Miscetti, S.; Parri, A.; Clark, A.G.; Couyoumtzelis, C.; Kambara, H.; Baumann, T.; Franklin, M.; Gordon, A.; Hamilton, R.; Huth, J.; and others

    1998-03-01

    We present a measurement of the top quark mass using a sample of t{bar t} decays into an electron or a muon, a neutrino, and four jets. The data were collected in p{bar p} collisions at {radical}(s)=1.8 TeV with the Collider Detector at Fermilab and correspond to an integrated luminosity of 109 pb{sup {minus}1} . We measure the top quark mass to be 175.9{plus_minus}4.8(stat){plus_minus}4.9( syst) GeV /c{sup 2} . {copyright} {ital 1998} {ital The American Physical Society}

  2. Total on-line purchasing system (TOPS)

    SciTech Connect

    Collins, N.

    1995-11-01

    The Information Management Division (IMD) at LLNL is developing a new purchasing system for the Procurement Department. The first major development of this new system is called, {open_quotes}Total On-Line Purchasing System{close_quotes} (TOPS). TOPS will help speed up the requisitioning process by having requisitions electronically entered by requesters and electronically sent to buyers to be put on Purchase Orders. The new purchasing system will use Electronic Commerce (EC)/Electronic Data Interchange (EDI), to help increase transaction flows for shipping notices, RFQs, Quotes, Purchase Orders, and Invoices. ANSI X.12 is the EDI standard that this new EC will use.

  3. Observation of Single Top Quark Production

    SciTech Connect

    Heinson, Ann; Junk, Tom R.; /Fermilab

    2011-01-01

    The field of experimental particle physics has become more sophisticated over time, as fewer, larger experimental collaborations search for small signals in samples with large components of background. The search for and the observation of electroweak single top quark production by the CDF and D0 collaborations at Fermilab's Tevatron collider are an example of an elaborate effort to measure the rate of a very rare process in the presence of large backgrounds and to learn about the properties of the top quark's weak interaction. We present here the techniques used to make this groundbreaking measurement and the interpretation of the results in the context of the Standard Model.

  4. Top quark mass measurements at the Tevatron

    SciTech Connect

    Youn, S. W.

    2014-03-01

    We present recent measurements of the mass of the top quark performed at the Tevatron $p\\bar{p}$ collider at a center-of-mass energy of 1.96 TeV. These measurements use the full Run II data samples corresponding to an integrated luminosity of up to 9.3 fb$^{-1}$. We also report the first world combination of the measurements from the Large Hadron Collider and Tevatron experiments resulting in a top mass of 173.34 {\\pm} 0.76 GeV with a relative precision of 0.44\\%.

  5. TOP500 Supercomputers for November 2003

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2003-11-16

    22nd Edition of TOP500 List of World s Fastest Supercomputers Released MANNHEIM, Germany; KNOXVILLE, Tenn.; BERKELEY, Calif. In what has become a much-anticipated event in the world of high-performance computing, the 22nd edition of the TOP500 list of the worlds fastest supercomputers was released today (November 16, 2003). The Earth Simulator supercomputer retains the number one position with its Linpack benchmark performance of 35.86 Tflop/s (''teraflops'' or trillions of calculations per second). It was built by NEC and installed last year at the Earth Simulator Center in Yokohama, Japan.

  6. Solar potential inventory and modeling

    NASA Technical Reports Server (NTRS)

    Angelici, G. L.; Bryant, N. A.

    1979-01-01

    Image processing procedures for calculating the energy that roof-mounted solar collectors can potentially supply in a metropolitan area are presented. Satellite multispectral imagery from which land cover types can be determined digitally was sampled in order to estimate the percentage of land area occupied by flat or south-facing roof tops in residential and commercial/industrial areas. Procedures were applied to the various power subdistricts of the western San Fernando valley of California, and it was found that on the average 120% of the existing power demand could be met if only half the useable rooftop area were utilized, amounting to 385 MW of peak power and indicating the applicability of solar cells to power generation in urban areas.

  7. Central solar-energy receiver

    DOEpatents

    Not Available

    1981-10-27

    An improved tower-mounted central solar energy receiver for heating air drawn through the receiver by an induced draft fan is described. A number of vertically oriented, energy absorbing, fin-shaped slats are radially arranged in a number of concentric cylindrical arrays on top of the tower coaxially surrounding a pipe having air holes through which the fan draws air which is heated by the slats which receive the solar radiation from a heliostat field. A number of vertically oriented and wedge-shaped columns are radially arranged in a number of concentric cylindrical clusters surrounding the slat arrays. The columns have two mirror-reflecting sides to reflect radiation into the slat arrays and one energy absorbing side to reduce reradiation and reflection from the slat arrays.

  8. Studies of top quark properties and search for electroweak single top quark production at the Tevatron

    SciTech Connect

    Datta, Mousumi; /Fermilab

    2007-10-01

    The top quark was discovered in 1995 by the CDF and D0 experiments at the Fermilab Tevatron during the Run I operation. Since the start of the Tevatron Run II in 2001, both experiments have collected {approx}2 fb{sup -1} data samples, which are over twenty times larger than that used in the Run 1 discovery. This larger data sample allows more precise studies of top-quark properties; differences between observed top-quark properties and the Standard Model (SM) prediction may give hints to possible physics beyond the SM. Here we present the latest results on the measurements of top-quark properties and the search for electroweak (EW) single top quark production from the CDF and D0 collaborations. The integrated luminosity used for the measurements corresponds to about 1 fb{sup -1}.

  9. Determination of the top-quark mass from hadro-production of single top-quarks

    NASA Astrophysics Data System (ADS)

    Alekhin, S.; Moch, S.; Thier, S.

    2016-12-01

    We present a new determination of the top-quark mass mt based on the experimental data from the Tevatron and the LHC for single-top hadro-production. We use the inclusive cross sections of s- and t-channel top-quark production to extract mt and to minimize the dependence on the strong coupling constant and the gluon distribution in the proton compared to the hadro-production of top-quark pairs. As part of our analysis we compute the next-to-next-to-leading order approximation for the s-channel cross section in perturbative QCD based on the known soft-gluon corrections and implement it in the program HATHOR for the numerical evaluation of the hadronic cross section. Results for the top-quark mass are reported in the MS ‾ and in the on-shell renormalization scheme.

  10. Infrared Aerosol Radiative Forcing at the Surface and the Top of the Atmosphere

    NASA Technical Reports Server (NTRS)

    Markowicz, Krzysztof M.; Flatau, Piotr J.; Vogelmann, Andrew M.; Quinn, Patricia K.; Welton, Ellsworth J.

    2003-01-01

    We study the clear-sky aerosol radiative forcing at infrared wavelengths using data from the Aerosol Characterization Experiment (ACE-Asia) cruise of the NOAA R/V Ronald H. Brown. Limited number of data points is analyzed mostly from ship and collocated satellite values. An optical model is derived from chemical measurements, lidar profiles, and visible extinction measurements which is used to and estimate the infrared aerosol optical thickness and the single scattering albedo. The IR model results are compared to detailed Fourier Transform Interferometer based infrared aerosol forcing estimates, pyrgeometer based infrared downward fluxes, and against the direct solar forcing observations. This combined approach attests for the self-consistency of the optical model and allows to derive quantities such as the infrared forcing at the top of the atmosphere or the infrared optical thickness. The mean infrared aerosol optical thickness at 10 microns is 0.08 and the single scattering albedo is 0.55. The modeled infrared aerosol forcing reaches 10 W/sq m during the cruise, which is a significant contribution to the total direct aerosol forcing. The surface infrared aerosol radiative forcing is between 10 to 25% of the shortwave aerosol forcing. The infrared aerosol forcing at the top of the atmosphere can go up to 19% of the solar aerosol forcing. We show good agreement between satellite (CERES instrument) retrievals and model results at the top of the atmosphere. Over the Sea of Japan, the average infrared radiative forcing is 4.6 W/sq m in the window region at the surface and it is 1.5 W/sq m at top of the atmosphere. The top of the atmosphere IR forcing efficiency is a strong function of aerosol temperature while the surface IR forcing efficiency varies between 37 and 55 W/sq m (per infrared optical depth unit). and changes between 10 to 18 W/sq m (per infrared optical depth unit).

  11. Solar ADEPT: Efficient Solar Energy Systems

    SciTech Connect

    2011-01-01

    Solar ADEPT Project: The 7 projects that make up ARPA-E's Solar ADEPT program, short for 'Solar Agile Delivery of Electrical Power Technology,' aim to improve the performance of photovoltaic (PV) solar energy systems, which convert the sun's rays into electricity. Solar ADEPT projects are integrating advanced electrical components into PV systems to make the process of converting solar energy to electricity more efficient.

  12. Solar Minimum

    NASA Astrophysics Data System (ADS)

    Lopresto, James C.; Mathews, John; Manross, Kevin

    1995-12-01

    Calcium K plage, H alpha plage and sunspot area have been monitored daily on the INTERNET since November of 1992. The plage and sunspot area have been measured by image processing. The purpose of the project is to investigate the degree of correlation between plage area and solar irradiance. The plage variation shows the expected variation produced by solar rotation and the longer secular changes produced by the solar cycle. The H alpha and sunspot plage area reached a minimum in about late 1994 or early 1995. This is in agreement with the K2 spectral index obtained daily from Sacramento Peak Observatory. The Calcium K plage area minimum seems delayed with respect to the others mentioned above. The minimum of the K line plage area is projected to come within the last few months of 1995.

  13. Solar Neutrinos

    DOE R&D Accomplishments Database

    Davis, R. Jr.; Harmer, D. S.

    1964-12-01

    The prospect of studying the solar energy generation process directly by observing the solar neutrino radiation has been discussed for many years. The main difficulty with this approach is that the sun emits predominantly low energy neutrinos, and detectors for observing low fluxes of low energy neutrinos have not been developed. However, experimental techniques have been developed for observing neutrinos, and one can foresee that in the near future these techniques will be improved sufficiently in sensitivity to observe solar neutrinos. At the present several experiments are being designed and hopefully will be operating in the next year or so. We will discuss an experiment based upon a neutrino capture reaction that is the inverse of the electron-capture radioactive decay of argon-37. The method depends upon exposing a large volume of a chlorine compound, removing the radioactive argon-37 and observing the characteristic decay in a small low-level counter.

  14. Solar flare particle radiation

    NASA Technical Reports Server (NTRS)

    Lanzerotti, L. J.

    1972-01-01

    The characteristics of the solar particles accelerated by solar flares and subsequently observed near the orbit of the earth are studied. Considered are solar particle intensity-time profiles, the composition and spectra of solar flare events, and the propagation of solar particles in interplanetary space. The effects of solar particles at the earth, riometer observations of polar cap cosmic noise absorption events, and the production of solar cell damage at synchronous altitudes by solar protons are also discussed.

  15. Current- and lattice-matched tandem solar cell

    DOEpatents

    Olson, J.M.

    1985-10-21

    A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga/sub x/In/sub 1-x/P (0.505 equal to or less than x equal to or less than 0.515) top cell semiconductor lattice-matched to a GaAs bottom cell semiconductor at a low resistance heterojunction, preferably a p/sup +//n/sup +/ heterojunction between the cells. The top and bottom cells are both lattice-matched and current-matched for high efficiency solar radiation conversion to electrical energy.

  16. Solar panel

    SciTech Connect

    Bayles, B.R.

    1981-09-29

    A solar panel includes a base within which are mounted transversely extending conduits. A heat collector plate in the base is in heat conductive relationship with the conduits for the heating of a fluid medium. The base additionally supports a transparent cover outwardly spaced from the heat collector plate to provide a protective insulative air space over the plate. A manifold communicates one series of panels with those of an adjacent series. A modified base dispenses with a collector plate and is formed so as to define integral lengthwise extending passageways for the solar heated medium. Inserted nipples interconnect the passageways of adjacent panels.

  17. Solar trap

    SciTech Connect

    Lew, H.S.

    1988-02-09

    A solar trap for collecting solar energy at a concentrated level is described comprising: (a) a compound light funnel including a pair of light reflecting substantially planar members arranged into a trough having a substantially V-shaped cross section; (b) a two dimensional Fresnel lens cover covering the opening of the compound light funnel, the opening being the open diverging end of the substantially V-shaped cross section of the compound light funnel; (c) at least one conduit for carrying a heat transfer fluid disposed substantially adjacent and substantially parallel to the apex line of the compound light funnel.

  18. Featured Image: Solar Prominence Eruptions

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-02-01

    In these images from the Solar Dynamics Observatorys AIA instrument (click for the full resolution!), two solar prominence eruptions (one from June 2011 and one from August 2012) are shown in pre- and post-eruption states. The images at the top are taken in the Fe XII 193 bandpass and the images at the bottom are taken in the He II 304 bandpass. When a team of scientists searched through seven years of solar images taken by the STEREO (Solar Terrestrial Relations Observatory) spacecraft, these two eruptions were found to extend all the way out to a distance of 1 AU. They were the only two examples of clear, bright, and compact prominence eruptions found to do so. The scientists, led by Brian Wood (Naval Research Laboratory), used these observations to reconstruct the motion of the eruption and model how prominences expand as they travel away from the Sun. Theimage to the rightshowsa STEREO observation compared to the teams 3D model of theprominences shape and expansion. To learn more about theresults from this study, check out the paper below.CitationBrian E. Wood et al 2016 ApJ 816 67. doi:10.3847/0004-637X/816/2/67

  19. Solar Energy and You.

    ERIC Educational Resources Information Center

    Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

    This booklet provides an introduction to solar energy by discussing: (1) how a home is heated; (2) how solar energy can help in the heating process; (3) the characteristics of passive solar houses; (4) the characteristics of active solar houses; (5) how solar heat is stored; and (6) other uses of solar energy. Also provided are 10 questions to…

  20. SEMMS - Understanding the solar electric multimission concept.

    NASA Technical Reports Server (NTRS)

    Irace, W. R.; Atkins, K. L.

    1972-01-01

    The feasibility of developing a solar electric multimission spacecraft (SEMMS) is examined with emphasis on understanding the effect of solar electric propulsion elements on a spacecraft system design. The applicability of Mariner, Viking, and thermoelectric outer planet spacecraft (TOPS) technologies to postulated mission/science objectives is investigated. A Mariner/Viking-based, modular spacecraft evolves which, with minimum modifications, is capable of performing a variety of interplanetary missions, including comet and asteroid rendezvous and orbit of Mercury, Jupiter, and Saturn. An early technology-evaluation flight is recommended to minimize the risk in subsequent missions.

  1. Solar maximum: Solar array degradation

    NASA Technical Reports Server (NTRS)

    Miller, T.

    1985-01-01

    The 5-year in-orbit power degradation of the silicon solar array aboard the Solar Maximum Satellite was evaluated. This was the first spacecraft to use Teflon R FEP as a coverglass adhesive, thus avoiding the necessity of an ultraviolet filter. The peak power tracking mode of the power regulator unit was employed to ensure consistent maximum power comparisons. Telemetry was normalized to account for the effects of illumination intensity, charged particle irradiation dosage, and solar array temperature. Reference conditions of 1.0 solar constant at air mass zero and 301 K (28 C) were used as a basis for normalization. Beginning-of-life array power was 2230 watts. Currently, the array output is 1830 watts. This corresponds to a 16 percent loss in array performance over 5 years. Comparison of Solar Maximum Telemetry and predicted power levels indicate that array output is 2 percent less than predictions based on an annual 1.0 MeV equivalent election fluence of 2.34 x ten to the 13th power square centimeters space environment.

  2. 5 CFR 1312.27 - Top secret control.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Top secret control. 1312.27 Section 1312... Classified Information § 1312.27 Top secret control. The EOP Security Officer serves as the Top Secret... Top Secret material. The ATSCOs will be responsible for the accountability and custodianship of...

  3. 49 CFR 178.812 - Top lift test.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    .... (b) Special preparation for the top lift test. (1) Metal, rigid plastic, and composite IBC design... 49 Transportation 2 2010-10-01 2010-10-01 false Top lift test. 178.812 Section 178.812... Testing of IBCs § 178.812 Top lift test. (a) General. The top lift test must be conducted for...

  4. 49 CFR 178.975 - Top lift test.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Large Packagings, from the side. (b) Special preparation for the top lift test. (1) Metal and rigid... 49 Transportation 2 2010-10-01 2010-10-01 false Top lift test. 178.975 Section 178.975... Testing of Large Packagings § 178.975 Top lift test. (a) General. The top lift test must be conducted...

  5. 5 CFR 1312.27 - Top secret control.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 3 2011-01-01 2011-01-01 false Top secret control. 1312.27 Section 1312... Classified Information § 1312.27 Top secret control. The EOP Security Officer serves as the Top Secret... Top Secret material. The ATSCOs will be responsible for the accountability and custodianship of...

  6. 49 CFR 178.812 - Top lift test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Top lift test. 178.812 Section 178.812... Top lift test. (a) General. The top lift test must be conducted for the qualification of all IBC design types designed to be lifted from the top or, for flexible IBCs, from the side. (b)...

  7. 49 CFR 178.975 - Top lift test.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Top lift test. 178.975 Section 178.975... Packagings § 178.975 Top lift test. (a) General. The top lift test must be conducted for the qualification of all of Large Packagings design types to be lifted from the top or, for flexible Large Packagings,...

  8. 5 CFR 1312.27 - Top secret control.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 3 2013-01-01 2013-01-01 false Top secret control. 1312.27 Section 1312... Classified Information § 1312.27 Top secret control. The EOP Security Officer serves as the Top Secret... Top Secret material. The ATSCOs will be responsible for the accountability and custodianship of...

  9. 5 CFR 1312.27 - Top secret control.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Top secret control. 1312.27 Section 1312... Classified Information § 1312.27 Top secret control. The EOP Security Officer serves as the Top Secret... Top Secret material. The ATSCOs will be responsible for the accountability and custodianship of...

  10. 5 CFR 1312.27 - Top secret control.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 3 2014-01-01 2014-01-01 false Top secret control. 1312.27 Section 1312... Classified Information § 1312.27 Top secret control. The EOP Security Officer serves as the Top Secret... Top Secret material. The ATSCOs will be responsible for the accountability and custodianship of...

  11. 14. TIP TOP MINE. TAILINGS LOCATED DIRECTLY WEST FROM TIP ...

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

    14. TIP TOP MINE. TAILINGS LOCATED DIRECTLY WEST FROM TIP TOP HOUSE. ID-31-C-12 WOODEN STRUCTURE IS VISIBLE IN TOP LEFT. CABLES VISIBLE LEFT AND CENTER OF TAILINGS. HOUSE IS JUST OVER APEX OF TAILINGS. CAMERA POINTED EAST. - Florida Mountain Mining Sites, Tip Top Mine, West face Florida Mountain, approximately 150 feet below summit, Silver City, Owyhee County, ID

  12. 49 CFR 178.812 - Top lift test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... preparation for the top lift test. (1) Metal, rigid plastic, and composite IBC design types must be loaded to... 49 Transportation 3 2013-10-01 2013-10-01 false Top lift test. 178.812 Section 178.812... Top lift test. (a) General. The top lift test must be conducted for the qualification of all...

  13. Top-Ten IT Issues, 2010

    ERIC Educational Resources Information Center

    Ingerman, Bret L.; Yang, Catherine

    2010-01-01

    The eleventh annual EDUCAUSE Current Issues Survey shows some very familiar themes among the top-ten IT issues of strategic importance to technology leaders in higher education. Indeed, all ten of the issues from the 2009 survey are back, albeit in a slightly different order. In addition, Strategic Planning returns as an issue of renewed…

  14. A Top Physicist Turns to Teaching

    ERIC Educational Resources Information Center

    Bollag, Burton

    2007-01-01

    This article describes how a top physicist took charge of reforming undergraduate science education at the University of British Columbia. Carl E. Wieman, the 2001 Nobel Prize winner in Physics, gave up his research career to devote himself to improving the way college science is taught. Wieman is heading up a $10.2 million science education…

  15. Top-Ten IT Issues, 2012

    ERIC Educational Resources Information Center

    Grajek, Susan

    2012-01-01

    In 2011, "EDUCAUSE" appointed a research panel of IT leaders from nineteen representative member institutions to both identify and prioritize the top IT issues facing their institutions. In two focus group sessions in September and October 2011, the panel members were asked the question: "What is the single-biggest IT-related issue currently…

  16. Green Power Partnership Top 30 College & University

    EPA Pesticide Factsheets

    The U.S. EPA's Green Power Partnership is a voluntary program designed to reduce the environmental impact of electricity generation by promoting renewable energy. The Top 30 College & University list details the largest higher ed green power users in GPP.

  17. FY 2003 Top 200 Users Survey Report

    DTIC Science & Technology

    2003-08-01

    rating of 90 percent. This may be because we have been unable to print brochures and announcements. Comparative Analysis on Effectiveness of Corporate ... Communication FY 2001 Top 200 Users Survey Strongly Agree or Agree Strongly Disagree or Disagree No Opinion New Product/ Service 92 2 6 Product

  18. What Top Management Expects from the Communicator.

    ERIC Educational Resources Information Center

    Fegley, Robert L.

    Top corporate management requires communications departments that maintain credibility with the public by developing the following qualities: integrity established through consistent and honest messages; accuracy based on solid research; authority derived from an understanding of the subject and from drawing on appropriate expertise; a…

  19. Top-Ten IT Issues: 2009

    ERIC Educational Resources Information Center

    Agee, Anne Scrivener; Yang, Catherine

    2009-01-01

    This article presents the top-ten IT-related issues in terms of strategic importance to the institution, as revealed by the tenth annual EDUCAUSE Current Issues Survey. These IT-related issues include: (1) Funding IT; (2) Administrative/ERP Information Systems; (3) Security; (4) Infrastructure/Cyberinfrastructure; (5) Teaching and Learning with…

  20. America's Star Libraries: Top-Rated Libraries

    ERIC Educational Resources Information Center

    Lance, Keith Curry; Lyons, Ray

    2009-01-01

    "Library Journal"'s national rating of public libraries, the "LJ" Index of Public Library Service 2009, Round 2, identifies 258 "star" libraries. Created by Keith Curry Lance and Ray Lyons and based on 2007 data from the IMLS, it rates 7,268 public libraries. The top libraries in each group get five, four, or three stars. All included libraries,…

  1. Race to Top Round Two Heating Up

    ERIC Educational Resources Information Center

    McNeil, Michele

    2010-01-01

    With the second-round deadline for federal Race to the Top Fund grants less than six weeks away, states are rushing to raise the stakes on their education reform plans as they fight over the remaining $3.4 billion in prize money. But in doing so, states from Massachusetts to Colorado are tangling with their teachers' unions as they test how far…

  2. W-Z-top-quark bags

    SciTech Connect

    Crichigno, Marcos P.; Shuryak, Edward; Flambaum, Victor V.; Kuchiev, Michael Yu.

    2010-10-01

    We discuss a new family of multiquanta-bound states in the standard model which exist due to the mutual Higgs-based attraction of the heaviest members of the standard model, namely, gauge quanta W, Z, and (anti)top quarks, t, t. We use a self-consistent mean-field approximation, up to a rather large particle number N. In this paper we do not focus on weakly bound, nonrelativistic bound states, but rather on 'bags' in which the Higgs vacuum expectation value is significantly modified or depleted. The minimal number N above which such states appear strongly depends on the ratio of the Higgs mass to the masses of W, Z, t, t: For a light Higgs mass, m{sub H{approx}}50 GeV, bound states start from N{approx}O(10), but for a ''realistic'' Higgs mass, m{sub H{approx}}100 GeV, one finds metastable/bound W, Z bags only for N{approx}O(1000). We also found that in the latter case pure top bags disappear for all N, although top quarks can still be well bound to the W bags. Anticipating the cosmological applications (discussed in the following Article [Phys. Rev. D 82, 073019]) of these bags as 'doorway states' for baryosynthesis, we also consider here the existence of such metastable bags at finite temperatures, when standard-model parameters such as Higgs, gauge, and top masses are significantly modified.

  3. Topping pressure for gas-storage cylinders

    NASA Technical Reports Server (NTRS)

    Haben, R. L.

    1979-01-01

    With charts derived from gas-storage system model, required topping pressure can be determined from initial cylinder pressure and temperature of gas entering cylinder. Charts are available for hydrogen and oxygen and can be developed for other important industrial gases as well.

  4. States Press Race to Top Blueprints

    ERIC Educational Resources Information Center

    Cavanagh, Sean

    2010-01-01

    States are pushing ahead with efforts to make sweeping changes to education policy through the Race to the Top program, despite some of them having seen individual schools and districts back out of the process because of concerns over the time and money required to make those plans a reality. The Obama administration has envisioned Race to the…

  5. The Top 10 Issues Impacting College Administrators.

    ERIC Educational Resources Information Center

    Kennedy, Mike

    2001-01-01

    Discusses the top challenges commonly confronted nationwide by college and universities, and similar facilities and businesses. Challenges include construction and repair, funding, housing, auxiliary services, maintenance and operations, marketing and recruiting, security and safety, staff training and retention, and technology. (GR)

  6. Race to Top Districts "Personalize" Plans

    ERIC Educational Resources Information Center

    McNeil, Michele

    2013-01-01

    The 16 Race to the Top district winners, pushed by $400 million in federal grants that put a premium on personalized learning, are embarking on vastly different makeovers of the classroom experience--from districtwide approaches to a narrower blueprint focused on middle school math. Despite the divergent approaches, a review of the winning…

  7. Top Four Trends in Student Information Systems

    ERIC Educational Resources Information Center

    Weathers, Robert

    2013-01-01

    The modern student information systems (SIS) is a powerful administrative tool with robust functionality. As such, it is essential that school and district administrators consider the top trends in modern student information systems before going forward with system upgrades or new purchases. These trends, described herein, are: (1) Support for…

  8. Electroweak symmetry breaking: Top quard condensates

    SciTech Connect

    Bardeen, W.A.

    1990-12-01

    The fundamental mechanisms for the dynamical breaking of the electroweak gauge symmetries remain a mystery. This paper examines the possible role of heavy fermions, particularly the top quark, in generating the observed electroweak symmetry breaking, the masses of the W and Z bosons and the masses of all observed quarks and leptons. 27 refs., 10 figs., 4 tabs.

  9. Hurdles Ahead in "Race to Top"

    ERIC Educational Resources Information Center

    McNeil, Michele

    2009-01-01

    As states scramble to spend and report on millions of dollars of education stimulus funds already flowing their way, they face another daunting task if they want a shot at even more money: navigating the complex application process for $4 billion from the Race to the Top Fund. Merely filling out the award application will take each state 642…

  10. More Top Students Answer the Ministry's Call

    ERIC Educational Resources Information Center

    Supiano, Beckie

    2008-01-01

    In an effort to help reverse a decades-long decline in the number of top students entering seminaries, the Lilly Endowment invited colleges to compete for grants to be used for three related purposes: (1) to help students explore the relationship between faith and work; (2) to encourage talented students to consider entering Christian ministry;…

  11. Race to Top Enters Home Stretch

    ERIC Educational Resources Information Center

    McNeil, Michele; Maxwell, Lesli A.

    2010-01-01

    When 16 finalists come to Washington next week to make their final pitches in the $4 billion Race to the Top competition, most can expect to go home empty-handed. U.S. Secretary of Education Arne Duncan, in announcing the finalists last week, said that no more than $2 billion will be divided among "very few winners" when the awards are…

  12. Tall tower or mountain top measurements?

    NASA Astrophysics Data System (ADS)

    Bamberger, Ines; Eugster, Werner; Oney, Brian; Brunner, Dominik; Leuenberger, Markus; Schanda, Rüdiger; Henne, Stephan; Buchmann, Nina

    2014-05-01

    Resolving the regional transport and distribution of greenhouse gases in the troposphere is a key topic that challenges both modelers and experimentalists. A dense network of measurement stations would be required, in particular including measurements at high elevation to better represent the entire lower troposphere, and not only small-scale local conditions in the near-surface atmosphere. While this can be achieved by tall towers, also mountain top stations (e.g. Schauinsland, Brocken) and other stations at high elevation (e.g., Mouna Loa, Jungfraujoch) are often appropriate, due to their extended concentration footprint. However, especially over complex, mountainous terrain, the transport of atmospheric gases and their spatio-temporal distribution is difficult to predict due to the development of thermally induced local wind patterns and boundary layer processes. Therefore, the main goal of our study is to test to what extend boundary layer processes at the surface and local wind patterns close to the ground at a mountain top site influence the ambient greenhouse gas patterns compared to measurements taken at a similar altitude but at a tall tower site. To this end we use measurements from the Zugerberg mountain top station, located at a pre-Alpine mountain ridge (987 m a.s.l., 4 m above ground) exposed to the prevailing synoptic winds in Switzerland, and compare these measurements with a neighboring tall tower site (Beromünster radio broadcast tower with its top at 1014 m a.s.l., 217 m above local ground level, and ≡500 m above the Swiss Plateau). The Beromünster tall tower is located at a distance of only 30 km from the mountain top station as the bird flies, and hence a direct comparison minimizes confounding factors that are not related to the tall tower vs. mountain top position of the measurements. Both stations are part of the CarboCount CH greenhouse gas observation network (http://www.carbocount.ch) initiated for long-term monitoring and modeling of

  13. Search for top quark at CDF

    SciTech Connect

    Not Available

    1994-11-01

    There is a vast theoretical and experimental support for idea that op quark as a weak isospin partner to b-quark should exist. Production cross section is steeply falling function of top quark mass. Therefore realistically at present only Tevatron p[anti p] collider at FNAL, with total energy 1.8 TeV in CMS system, still has a chance of top quark discovery. Dominant production mechanism for top quarks at Tevatron is pair production of t[anti t]. With almost 100% probability t ([anti t]) decays in mode t [yields] W[sup +]b. Distinct features of this decay provide very good signatures of top quark production which helps to reduce otherwise very high level of background. Based on simple combinatorial arguments one can show that W should decay in 1/9 cases into W [yields] l + [nu] where l stands for lepton (e,[mu],[tau]). Very clean signature represents case when both W's from t and [anti t] decay into e ([mu]) + [nu]. In this case experimental observation will be two isolated leptons characterized by large transverse momentum, large missing transverse energy E[sub T] and 2 b quark jets. Jets originated from b quarks can be quite frequently recognized by presence of secondary vertices associated with jets. Another feature of b-jets which can be used for their identification is frequent association of so called soft leptons with jets. Two experimental setups CDF and D0 are able to take advantage of Tevatron for top quark discovery. Recently CDF collaboration presented evidence for direct observation of t[anti t] production in 19.3 pb[sup [minus]1] of p[anti p] collisions at [radical](s) = 1.8TeV. Very brief account of these results is presented here.

  14. Improved High-Energy Response of AlGaAs/GaAs Solar Cells Using a Low-Cost Technology

    NASA Astrophysics Data System (ADS)

    Noorzad, Camron D.; Zhao, Xin; Harotoonian, Vache; Woodall, Jerry M.

    2016-12-01

    We report on an AlGaAs/GaAs solar cell with a significantly increased high-energy response that was produced via a modified liquid phase epitaxy (LPE) technique. This technique uses a one-step process in which the solid-liquid equilibrium Al-Ga-As:Zn melt in contact with an n-type vendor GaAs substrate simultaneously getters impurities in the substrate that shorten minority carrier lifetimes, diffuses Zn into the substrate to create a p- n junction, and forms a thin p-AlGaAs window layer that enables more high-energy light to be efficiently absorbed. Unlike conventional LPE, this process is performed isothermally. In our "double Al" method, the ratio of Al in the melt ("Al melt ratio") that was used in our process was two times more than what was previously reported in the record 1977 International Business Machines (IBM) solar cell. Photoluminescence (PL) results showed our double Al sample yielded a response to 405 nm light ("blue light"), which was more than twice as intense as the response from our replicated IBM cell. The original 1977 cell had a low-intensity spectral response to photon wavelengths under 443 nm (Woodall and Hovel in Sol Energy Mater Sol Cells 29:176, 1990). Secondary ion mass spectrometry results confirmed the increased blue light response was due to a large reduction in AlGaAs window layer thickness. These results proved increasing the Al melt ratio broadens the spectrum of light that can be transmitted through the window layer into the active GaAs region for absorption, increasing the overall solar cell efficiency. Our enhanced double Al method can pave the way for large-scale manufacturing of low-cost, high-efficiency solar cells.

  15. Long-Term Cryogenic Propellant Storage for the Titan Orbiter Polar Surveyor (TOPS) Mission

    NASA Technical Reports Server (NTRS)

    Mustafi, Shuvo; Francis, John; Li, Xiaoyi; DeLee, Hudson; Purves, Lloyd; Willis, Dewey; Nixon, Conor; Mcguinness, Dan; Riall, Sara; Devine, Matt; Hedayat, Ali

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LOX) can dramatically enhance NASAs ability to explore the solar system because of their superior specific impulse (Isp) capability. Although these cryogenic propellants can be challenging to manage and store, they allow significant mass advantages over traditional hypergolic propulsion systems and are therefore technically enabling for many planetary science missions. New cryogenic storage techniques such as subcooling and the use of advanced insulation and low thermal conductivity support structures will allow for the long term storage and use of cryogenic propellants for solar system exploration and hence allow NASA to deliver more payloads to targets of interest, launch on smaller and less expensive launch vehicles, or both. Employing cryogenic propellants will allow NASA to perform missions to planetary destinations that would not be possible with the use of traditional hypergolic propellants. These new cryogenic storage technologies were implemented in a design study for the Titan Orbiter Polar Surveyor (TOPS) mission, with LH2 and LOX as propellants, and the resulting spacecraft design was able to achieve a 43 launch mass reduction over a TOPS mission, that utilized a conventional hypergolic propulsion system with mono-methyl hydrazine (MMH) and nitrogen tetroxide (NTO) propellants. This paper describes the cryogenic propellant storage design for the TOPS mission and demonstrates how these cryogenic propellants are stored passively for a decade-long Titan mission.

  16. Mechanically stacked concentrator tandem solar cells

    NASA Technical Reports Server (NTRS)

    Andreev, V. M.; Rumyantsev, V. D.; Karlina, L. B.; Kazantsev, A. B.; Khvostikov, V. P.; Shvarts, M. Z.; Sorokina, S. V.

    1995-01-01

    Four-terminal mechanically stacked solar cells were developed for advanced space arrays with line-focus reflective concentrators. The top cells are based on AlGaAs/GaAs multilayer heterostructures prepared by low temperature liquid phase epitaxy. The bottom cells are based on heteroepitaxial InP/InGaAs liquid phase epitaxy or on homo-junction GaSb, Zn-diffused structures. The sum of the highest reached efficiencies of the top and bottom cells is 29.4 percent. The best four-terminal tandems have an efficiency of 27 to 28 percent. Solar cells were irradiated with 1 MeV electrons and their performances were determined as a function of fluence up to 10(exp 16) cm(exp-2). It was shown that the radiation resistance of developed tandem cells is similar to the most radiative stable AlGaAs/GaAs cells with a thin p-GaAs photoactive layer.

  17. Solar Power

    ERIC Educational Resources Information Center

    Ford, Norman C.; Kane, Joseph W.

    1971-01-01

    Proposes a method of collecting solar energy by using available plastics for Fresnel lenses to focus heat onto a converter where thermal dissociation of water would produce hydrogen. The hydrogen would be used as an efficient non-polluting fuel. Cost estimates are included. (AL)

  18. Solar Directory.

    ERIC Educational Resources Information Center

    Pesko, Carolyn, Ed.

    This directory is designed to help the researcher and developer, the manufacturer and distributor, and the general public communicate together on a mutually beneficial basis. Its content covers the wide scope of solar energy activity in the United States primarily, but also in other countries, at the academic, governmental, and industrial levels.…

  19. Solar cooker

    SciTech Connect

    Long, J. B.; Ware, R. R.

    1985-12-31

    A solar cooking device made of a flat array of concentric mirrors tilted to focus at a small area, the array being movable mounted on a stand to be movable around a ball joint and with a carrier for a cooking vessel held by a double crank to be at the focal area of the mirrors.

  20. Recent Results of Top Quark Physics from the Tevatron

    SciTech Connect

    Peters, R. Y.

    2015-07-09

    Twenty years after its discovery in 1995 by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at Fermilab, the top quark still undergoes intensive studies at the Tevatron and the LHC at CERN. In this article, recent top quark physics results from CDF and D0 are reported. In particular, measurements of single top quark and double top quark production, the $t\\bar{t}$ forward-backward asymmetry and the top quark mass are discussed.

  1. Top quark physics results from CDF and D-Zero

    SciTech Connect

    Gerdes, D.

    1996-10-01

    I summarize recent top quark physics results from the Fermilab Tevatron experiments. Since the observation of the top quark by CDF and D{null} in 1995, the experimental focus has shifted to a detailed study of the top quark`s properties. This article describes recent measurements of the top quark production cross section, mass, kinematic properties, branching ratios, V{sub {ital tb}}, and the {ital W} polarization in top decays.

  2. 5. VIEW OF TIP TOP WITH FAR RIGHT SADDLE PROVIDING ...

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

    5. VIEW OF TIP TOP WITH FAR RIGHT SADDLE PROVIDING ORIENTATION FOR THE GENERAL DIRECTION TO NOTTINGHAM. CAMERA POINTED SOUTH-SOUTHWEST. NORTH SIDE OF TIP TOP BUILDING IS VISIBLE. (RUN STRAIGHT EDGE FROM LOWER LEFT CORNER TO TOP CENTER OF PRINT; TIP TOP LOCATED LIGHT AREA) ONTARIO IS LOCATED BELOW AND RIGHT OF TIP TOP. - Florida Mountain Mining Sites, Silver City, Owyhee County, ID

  3. Tree Topping Ceremony at NASA's Propulsion Research Laboratory

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A new, world-class laboratory for research into future space transportation technologies is under construction at the Marshall Space Flight Center (MSFC) in Huntsville, AL. The state-of-the-art Propulsion Research Laboratory will serve as a leading national resource for advanced space propulsion research. Its purpose is to conduct research that will lead to the creation and development of irnovative propulsion technologies for space exploration. The facility will be the epicenter of the effort to move the U.S. space program beyond the confines of conventional chemical propulsion into an era of greatly improved access to space and rapid transit throughout the solar system. The Laboratory is designed to accommodate researchers from across the United States, including scientists and engineers from NASA, the Department of Defense, the Department of Energy, universities, and industry. The facility, with 66,000 square feet of useable laboratory space, will feature a high degree of experimental capability. Its flexibility will allow it to address a broad range of propulsion technologies and concepts, such as plasma, electromagnetic, thermodynamic, and propellantless propulsion. An important area of emphasis will be development and utilization of advanced energy sources, including highly energetic chemical reactions, solar energy, and processes based on fission, fusion, and antimatter. The Propulsion Research Laboratory is vital for developing the advanced propulsion technologies needed to open up the space frontier, and will set the stage of research that could revolutionize space transportation for a broad range of applications. This photo depicts construction workers taking part in a tree topping ceremony as the the final height of the laboratory is framed. The ceremony is an old German custom of paying homage to the trees that gave their lives in preparation of the building site.

  4. Solar electric systems

    SciTech Connect

    Warfield, G.

    1984-01-01

    Electricity from solar sources is the subject. The state-of-the-art of photovoltaics, wind energy and solar thermal electric systems is presented and also a broad range of solar energy activities throughout the Arab world is covered. Contents, abridged: Solar radiation fundamentals. Basic theory solar cells. Solar thermal power plants. Solar energy activities at the scientific research council in Iraq. Solar energy program at Kuwait Institute for Scientific Research. Prospects of solar energy for Egypt. Non-conventional energy in Syria. Wind and solar energies in Sudan. Index.

  5. Influence of the Entrainment Interface Layer on Cloud Microphysical Properties near Stratocumulus Top

    NASA Astrophysics Data System (ADS)

    Chuang, P. Y.; Carman, J. K.; Rossiter, D. L.

    2010-12-01

    Entrainment across the stratocumulus-topped boundary layer is a key process governing the cloud properties and evolution. This process is not well-represented even in high-resolution large-eddy simulations, in part due to the sharp gradients in temperature, buoyancy and (usually) humidity that occur at the top of the boundary layer. In summer 2008, the Physics of Stratocumulus Top (POST) field campaign conduct extensive measurements in the vicinity of cloud top, including the so-called entrainment interface layer or EIL that separates boundary layer and free tropospheric air. Roughly half of the fifteen flights occurred during the day (near solar noon) while the remaining flights occurred during late evening-to-night when solar input was minimal. A wide diversity of EIL properties has been revealed over the course of the campaign. EIL vertical thickness diagnosed using total water varies from fairly thin (~20 m) to very thick (>100 m). The thickness and intensity of the turbulent layer in this interfacial region also varies substantially, with the top of the significantly turbulent region ranging from 10 m to 50 m above cloud top. Shear in the vicinity of cloud top also varied strongly from day-to-day. While almost all cases exhibited strong jumps in potential temperature, there are a number of cases where the jump in total water was very small-to-none, and one case where total water was higher in the free troposphere by 1.4 g/kg. POST thus demonstrates that the cloud-top interfacial region exhibits a rich and diverse range of properties. This study focuses on how this EIL diversity affects the stratocumulus cloud itself. We build on our study of the EIL dynamic and thermodynamic properties to investigate the influence of the EIL on the microphysical properties of the stratocumulus in the vicinity of cloud top. Entrainment of the overlying warmer and (usually) drier air can strongly impact the amount of liquid water as well as the size and concentration of cloud

  6. Semi-transparent inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Schmidt, H.; Winkler, T.; Tilgner, M.; Flügge, H.; Schmale, S.; Bülow, T.; Meyer, J.; Johannes, H.-H.; Riedl, T.; Kowalsky, W.

    2009-08-01

    We will present efficient semi-transparent bulk-heterojunction [regioregular of poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester] solar cells with an inverted device architecture. Highly transparent ZnO and TiO2 films prepared by Atomic Layer Deposition are used as cathode interlayers on top of ITO. The topanode consists of a RF-sputtered ITO layer. To avoid damage due to the plasma deposition of this layer, a sputtering buffer layer of MoO3 is used as protection. This concept allows for devices with a transmissivity higher than 60 % for wavelengths 650 nm. The thickness of the MoO3 buffer has been varied in order to study its effect on the electrical properties of the solar cell and its ability to prevent possible damage to the organic active layers upon ITO deposition. Without this buffer or for thin buffers it has been found that device performance is very poor concerning the leakage current, the fill factor, the short circuit current and the power conversion efficiencies. As a reference inverted solar cells with a metal electrode (Al) instead of the ITO-top contact are used. The variation between the PCE of top versus conventional illumination of the semi-transparent cells was also examined and will be interpreted in view of the results of the optical simulation of the dielectric device stack with and without reflection top electrode. Power conversion efficiencies of 2-3 % for the opaque inverted solar cells and 1.5-2.5 % for the semi-transparent devices were obtained under an AM1.5G illumination.

  7. Collecting Solar Energy. Solar Energy Education Project.

    ERIC Educational Resources Information Center

    O'Brien, Alexander

    This solar energy learning module for use with junior high school students offers a list of activities, a pre-post test, job titles, basic solar energy vocabulary, and diagrams of solar energy collectors and installations. The purpose is to familiarize students with applications of solar energy and titles of jobs where this knowledge could be…

  8. Solar Impulse's Solar-Powered Plane

    ScienceCinema

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2016-07-12

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  9. Solar Impulse's Solar-Powered Plane

    SciTech Connect

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2013-07-08

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  10. Water vapor near Venus cloud tops from VIRTIS-H/Venus express observations 2006-2011

    NASA Astrophysics Data System (ADS)

    Cottini, V.; Ignatiev, N. I.; Piccioni, G.; Drossart, P.

    2015-08-01

    This work aims to give a summary of the water vapor at the cloud top of Venus atmosphere using the complete set of observations made using high spectral resolution channel (-H) of Visible and Infrared Thermal Imaging Spectrometer (VIRTIS), on board the ESA Venus Express orbiter, to measure the cloud top altitude and the water vapor abundance near this level. An initial analysis of these measurements by Cottini et al. (2012) was limited to data in 140 orbits in the period 2007-2008. These observations were limited to the Northern hemisphere due to observational geometry in this early part of the mission. In the present paper, the analysis is extended to a larger dataset covering the years 2006-2011, significantly improving the latitudinal coverage. Altitude of the cloud tops, corresponding to unit optical depth at a wavelength of 2.5 μm, is equal to 69±1 km at low latitudes, and decreases toward the pole to 62-64 km. The water vapor abundance is equal to 3±1 ppm in low latitudes and it increases reaching a maximum of 5±2 ppm at 70-80° of latitude in both hemispheres, with a sharp drop in the polar regions. This can be explained by the specific dynamics of the atmosphere of Venus affecting the distribution of water vapor such as the transfer of water vapor in the Hadley cell and the dynamic in the polar vortex. The average height of the cloud tops and the H2O near this level are symmetric with respect to the equator. As a function of local solar time, the water vapor shows no particular dependence, and the cloud tops exhibit just a weak maximum around noon. Over 5 years of observations the average values of the cloud top altitude and the water vapor were quite stable in low and middle latitudes, while in high latitudes both quantities in 2009-2011 years are systematically higher than in 2006-2008. Short period variations increasing with latitude are observed, from approximately less than ±1 km for cloud tops and ±1 ppm for water vapor in low latitudes to

  11. PREFACE: 5th International Workshop on Top Quark Physics (TOP2012)

    NASA Astrophysics Data System (ADS)

    Salamanna, G.; Boisvert, V.; Cerrito, L.; Khan, A.; Moretti, S.; Owen, M.; Schwanenberger, C.

    2013-07-01

    The 5th International Workshop on Top Quark Physics (TOP 2012) took place in Winchester, UK, from the 16-21 September. It gathered students as well as people active in the top quark sector and provided a framework to highlight the newest results and matters related to top quark physics. Discovered in 1995, the top quark is the sixth and heaviest of all quarks, and it is the only one with a lifetime short enough to be observed 'naked'. This makes it an important testing ground in the search for new physics. In fact, the fact of its mass being so much larger than the other quarks, hints at its special role in the Higgs mechanism. For the same reason, in many models of New Physics, new heavy resonances are expected to couple mostly with top quarks. Even if no new particles are observed, the direct correlation between its angular momentum and that of its detectable decay products allows us to probe indirectly New Physics in action when top quarks are created. In this edition of the TOP conference series, for the first time, the agenda was equally balanced between 'traditional' measurements and the now vast number of searches for physics BSM in the top quark sector, thanks mostly to the amount of data collected at the LHC in its Run I. New results were presented by both the Tevatron and the LHC collaborations: improved ttbar and single top cross-section measurements, refined techniques to measure the top quark mass and a large number of results on properties such as spin correlation and W boson polarization in top quark decays were shown. More technical discussions on the experimental issues, both from the detector and the simulation side also took place, drawing together experimentalists and theorists. Reviews of the latest results on ttbar asymmetry both from CDF and D0 and from ATLAS and CMS were shown, and theorists active in the field made some interesting points on this hot topic. Additionally, results on the search for fourth generation fermions and new

  12. Drying firewood in a temporary solar kiln: a case study. Forest Service research note

    SciTech Connect

    Sampson, G.R.; Gasbarro, A.F.

    1986-08-01

    A pilot study was undertaken to determine drying rates for small-diameter, unsplit paper birch firewood that was dried: (1) in a conventional top-covered pile; (2) in a simple, temporary solar kiln; and (3) in tree length. Drying rates were the same for firewood piles whether they were in the temporary kiln or only covered on top to keep rain or snow from entering the pile. Trees that were severed at the stump and left to dry in tree length form, complete with branches and leaves, however, dried slower than firewood cut to length, stacked and top-covered or placed in the temporary solar kiln.

  13. TOP500 Supercomputers for June 2003

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2003-06-23

    21st Edition of TOP500 List of World's Fastest Supercomputers Released MANNHEIM, Germany; KNOXVILLE, Tenn.;&BERKELEY, Calif. In what has become a much-anticipated event in the world of high-performance computing, the 21st edition of the TOP500 list of the world's fastest supercomputers was released today (June 23, 2003). The Earth Simulator supercomputer built by NEC and installed last year at the Earth Simulator Center in Yokohama, Japan, with its Linpack benchmark performance of 35.86 Tflop/s (teraflops or trillions of calculations per second), retains the number one position. The number 2 position is held by the re-measured ASCI Q system at Los Alamos National Laboratory. With 13.88 Tflop/s, it is the second system ever to exceed the 10 Tflop/smark. ASCIQ was built by Hewlett-Packard and is based on the AlphaServerSC computer system.

  14. The heavy top quark and supersymmetry

    SciTech Connect

    Hall, L.J. |

    1997-01-01

    Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the Standard Model which can provide an understanding for many of the outstanding problems of particle physics. A broken supersymmetric extension of spacetime allows electroweak symmetry breaking to follow from the dynamics of the heavy top quark; an extension of isospin provides a constrained framework for understanding the pattern of quark and lepton masses; and a grand unified extension of the Standard Model gauge group provides an elegant understanding of the gauge quantum numbers of the components of a generation. Experimental signatures for each of these additional symmetries are discussed.

  15. Top quark production measurements at ATLAS

    NASA Astrophysics Data System (ADS)

    Calkins, R.; Atlas Collaboration

    2012-09-01

    An overview of top quark production measurements using the ATLAS detector at the LHC is presented. Using 35 pb-1 of data, we measured the tt¯ cross-section in the lepton+jets channel to 13% precision and set limits on the cross-section for the all hadronic decay channel[1, 2]. The measurement in the dilepton channel was performed using 0.70 fb-1 of data and was combined with the lepton+jets channel result for our most precise tt¯ cross-section measurement of σpp→tt¯+X = 176±5 (stat)+13-10 (syst)±7 (lumi)[3,4]. Single top production was also measured in the t-channel using 0.70 fb-1 of data[5].

  16. The heavy top quark and supersymmetry

    SciTech Connect

    Hall, L.J. |

    1996-05-08

    Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the standard model which can provide an understanding for many of the outstanding problems of particle physics. A broken supersymmetric extension of spacetime allows electroweak symmetry breaking to follow from the dynamics of the heavy top quark; an extension of isospin provides a constrained framework for understanding the pattern of quark and lepton masses; and a grand unified extension of the standard model gauge group provides an elegant understanding of the gauge quantum numbers of the components of a generation. Experimental signatures for each of these additional symmetries are discussed.

  17. Entanglement entropy in top-down models

    NASA Astrophysics Data System (ADS)

    Jones, Peter A. R.; Taylor, Marika

    2016-08-01

    We explore holographic entanglement entropy in ten-dimensional supergravity solutions. It has been proposed that entanglement entropy can be computed in such top-down models using minimal surfaces which asymptotically wrap the compact part of the geometry. We show explicitly in a wide range of examples that the holographic entan-glement entropy thus computed agrees with the entanglement entropy computed using the Ryu-Takayanagi formula from the lower-dimensional Einstein metric obtained from reduc-tion over the compact space. Our examples include not only consistent truncations but also cases in which no consistent truncation exists and Kaluza-Klein holography is used to identify the lower-dimensional Einstein metric. We then give a general proof, based on the Lewkowycz-Maldacena approach, of the top-down entanglement entropy formula.

  18. Top-down visual search in Wimmelbild

    NASA Astrophysics Data System (ADS)

    Bergbauer, Julia; Tari, Sibel

    2013-03-01

    Wimmelbild which means "teeming figure picture" is a popular genre of visual puzzles. Abundant masses of small figures are brought together in complex arrangements to make one scene in a Wimmelbild. It is picture hunt game. We discuss what type of computations/processes could possibly underlie the solution of the discovery of figures that are hidden due to a distractive influence of the context. One thing for sure is that the processes are unlikely to be purely bottom-up. One possibility is to re-arrange parts and see what happens. As this idea is linked to creativity, there are abundant examples of unconventional part re-organization in modern art. A second possibility is to define what to look for. That is to formulate the search as a top-down process. We address top-down visual search in Wimmelbild with the help of diffuse distance and curvature coding fields.

  19. Top cross section measurement at CDF

    SciTech Connect

    Compostella, Gabriele; /INFN, CNAF /Padua U.

    2010-01-01

    This paper describes the latest measurements of the t{bar t} pair production cross section performed by the CDF Collaboration analyzing p{bar p} collisions at a center-of-mass energy of 1.96 TeV from Fermilab Tevatron, as presented at the XVIII International Workshop on Deep-Inelastic Scattering and Related Subjects. In order to test Standard Model predictions, several analysis methods are explored and all the top decay channels are considered, to better constrain the properties of the top quark and to search for possible sources of new physics affecting the pair production mechanism. Experimental results using an integrated luminosity up to 5.1 fb{sup -1} are presented.

  20. TOP500 Supercomputers for November 2002

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack; Simon, Horst D.

    2002-11-15

    20th Edition of TOP500 List of World's Fastest Supercomputers Released MANNHEIM, Germany; KNOXVILLE, Tenn.;&BERKELEY, Calif. In what has become a much-anticipated event in the world of high-performance computing, the 20th edition of the TOP500 list of the world's fastest supercomputers was released today (November 15, 2002). The Earth Simulator supercomputer installed earlier this year at the Earth Simulator Center in Yokohama, Japan, is with its Linpack benchmark performance of 35.86 Tflop/s (trillions of calculations per second) retains the number one position. The No.2 and No.3 positions are held by two new, identical ASCI Q systems at Los Alamos National Laboratory (7.73Tflop/s each). These systems are built by Hewlett-Packard and based on the Alpha Server SC computer system.

  1. Kodiak seamount not flat-topped.

    PubMed

    Hamilton, E L; von Huene, R E

    1966-12-09

    Earlier surveys in the Aleutian Trench southeast of Kodiak Island, Alaska, indicated that Kodiak Seamount had a flat top and was a tablemount or guyot. This seamount is of special significance because it has been supposed that its surface was eroded at the same time as those of a line of guyots to the southeast. If so, its present position in the axis of the Aleutian Trench indicates that the line of guyots was formed before the trench. A two-part survey in 1965 showed that Kodiak Seamount is not flat-topped, and should be eliminated from the category of guyots. Reflection profiling records indicate that the seamount was formed before the adjacent sediments were deposited, and that the small trough, or moat, on the south side is a depositional feature probably formed by a scouring effect or by the acceleration of turbidity currents around the base of the mount.

  2. Top quark kinematics and mass determination

    SciTech Connect

    Williams, H.H.

    1994-10-01

    An analysis is presented of 10 W + {ge} 3 jet events, each with evidence for the presence of a b quark, that were recently observed by the CDF collaboration. Seven of these events include a fourth jet and can be explicitly reconstructed as t{bar t} production. The best estimate of the top quark mass is M{sub t} = 174 {+-} 10{sub {minus}12}{sup +13} GeV/c{sup 2}. A study has also been performed to see if the kinematical properties of events with W + {ge} 3 jets gives evidence for top production. An excess of events with large jet energies, compared to that expected from direct production of W + {ge} 3 jets, is observed. A large fraction of these events also contain a b-quark and a fourth jet.

  3. Top quark and electroweak results from CDF

    SciTech Connect

    Sandra Leone

    2003-11-04

    In 2001 the Tevatron run II began, after a five year period of significant upgrade of the accelerator itself and of the experiments CDF and D0. After a detector commissioning run, the CDF experiment is now taking high quality data with all subsystems functional. We report in this talk the first preliminary CDF results on top quark and W/Z boson properties, based on run II data. The top quark, discovered in 1995 at the Tevatron, has proven to be a very interesting particle. Its properties allow to perform stringent tests of the Standard Model (SM) and to search for new physics through a deviation from SM predictions. We give here some expectations of what Tevatron run II will ultimately provide to our understanding of matter.

  4. Investigation of the basic physics of high efficiency semiconductor hot carrier solar cell

    NASA Technical Reports Server (NTRS)

    Alfano, R. R.; Wang, W. B.; Mohaidat, J. M.; Cavicchia, M. A.; Raisky, O. Y.

    1995-01-01

    The main purpose of this research program is to investigate potential semiconductor materials and their multi-band-gap MQW (multiple quantum wells) structures for high efficiency solar cells for aerospace and commercial applications. The absorption and PL (photoluminescence) spectra, the carrier dynamics, and band structures have been investigated for semiconductors of InP, GaP, GaInP, and InGaAsP/InP MQW structures, and for semiconductors of GaAs and AlGaAs by previous measurements. The barrier potential design criteria for achieving maximum energy conversion efficiency, and the resonant tunneling time as a function of barrier width in high efficiency MQW solar cell structures have also been investigated in the first two years. Based on previous carrier dynamics measurements and the time-dependent short circuit current density calculations, an InAs/InGaAs - InGaAs/GaAs - GaAs/AlGaAs MQW solar cell structure with 15 bandgaps has been designed. The absorption and PL spectra in InGaAsP/InP bulk and MQW structures were measured at room temperature and 77 K with different pump wavelength and intensity, to search for resonant states that may affect the solar cell activities. Time-resolved IR absorption for InGaAsP/InP bulk and MQW structures has been measured by femtosecond visible-pump and IR-probe absorption spectroscopy. This, with the absorption and PL measurements, will be helpful to understand the basic physics and device performance in multi-bandgap InAs/InGaAs - InGaAs/InP - InP/InGaP MQW solar cells. In particular, the lifetime of the photoexcited hot electrons is an important parameter for the device operation of InGaAsP/InP MQW solar cells working in the resonant tunneling conditions. Lastly, time evolution of the hot electron relaxation in GaAs has been measured in the temperature range of 4 K through 288 K using femtosecond pump-IR-probe absorption technique. The temperature dependence of the hot electron relaxation time in the X valley has been measured.

  5. Effect on Sb on the Properties of GaInP Top Cells: Preprint

    SciTech Connect

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

    2006-05-01

    It is well known that the efficiency of GaInP/GaAs tandem solar cells is limited by the band gap of the GaInP top cell, which, in turn, is determined by the degree of compositional ordering in GaInP base layer. Attempts to raise the band gap by the addition of Al to the top cell have met with limited success due to the strong affinity between Al and oxygen. Here we investigate a different approach. It has been shown that the presence of antimony on the surface of GaInP during its growth suppresses the ordering process and increases the band gap. In this paper, we study the effects of Sb on the properties of GaInP top cells. We show that, in addition to raising the band gap of GaInP, it also increases the incorporation of Zn and changes the relative incorporation of Ga and In. These effects depend strongly on the substrate orientation, growth temperature and rate, and the Sb/P ratio in the gas phase. We show that the band gap of the GaInP top cell (and the Voc) can be increased without reducing the minority carrier collection efficiency. The implications of these results are presented and discussed.

  6. Top physics at the Tevatron Collider

    SciTech Connect

    Margaroli, Fabrizio; /Purdue U.

    2007-10-01

    The top quark has been discovered in 1995 at the CDF and DO experiments located in the Tevatron ring at the Fermilab laboratory. After more than a decade the Tevatron collider, with its center-of-mass energy collisions of 1.96 TeV, is still the only machine capable of producing such exceptionally heavy particle. Here I present a selection of the most recent CDF and DO measurements performed analyzing {approx} 1 fb{sup -1} of integrated luminosity.

  7. Rare top quark decays in extended models

    SciTech Connect

    Gaitan, R.; Miranda, O. G.; Cabral-Rosetti, L. G.

    2006-09-25

    Flavor changing neutral currents (FCNC) decays t {yields} H0 + c, t {yields} Z + c, and H0 {yields} t + c-bar are discussed in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions where FCNC decays may take place at tree-level and are only suppressed by the mixing between ordinary top and charm quarks, which is poorly constraint by current experimental values. The non-manifest case is also briefly discussed.

  8. Braking, Wheeled Vehicles. Test Operations Procedure (TOP)

    DTIC Science & Technology

    2008-05-20

    are as follows: a. Micrometer calipers (inside, outside, and dial types). b. Surface finish gauges. c. Torque wrench. d. Brake shoe...is imminent. 11. Front Disc Brakes Procedure: Step 1: Visually inspect and measure rotors, calipers , and pads. Equipment needed...4. TITLE AND SUBTITLE Test Operations Procedure (TOP) 2-2-608 Braking , Wheeled Vehicles 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e

  9. Charm, beauty and top at HERA

    NASA Astrophysics Data System (ADS)

    Behnke, O.; Geiser, A.; Lisovyi, M.

    2015-09-01

    Results on open charm and beauty production and on the search for top production in high-energy electron-proton collisions at HERA are reviewed. This includes a discussion of relevant theoretical aspects, a summary of the available measurements and measurement techniques, and their impact on improved understanding of QCD and its parameters, such as parton density functions and charm- and beauty-quark masses. The impact of these results on measurements at the LHC and elsewhere is also addressed.

  10. Slow Pace for Race to Top Spending

    ERIC Educational Resources Information Center

    McNeil, Michele

    2012-01-01

    Almost two years into the federal Race to the Top program, states are spending their shares of the $4 billion prize at a snail's pace--a reflection of the challenges the 12 winners face as they try to get ambitious education improvement plans off the ground. Through the end of March, the 11 states and the District of Columbia had spent just 14…

  11. The myth of the top management team.

    PubMed

    Katzenbach, J R

    1997-01-01

    Companies all across the economic spectrum are making use of teams. They go by a variety of names and can be found at all levels. In fact, you are likely to find the group at the very top of an organization professing to be a team. But even in the best of companies, a so-called top team seldom functions as a real team. Real teams must follow a well-defined discipline to achieve their performance potential. And performance is the key issue--not the fostering of "team values" such as empowerment, sensitivity, or involvement. In recent years, the focus on performance was lost in many companies. Even today, CEOs and senior executives often see few gains in performance from their attempts to become more teamlike. Nevertheless, a team effort at the top can be essential to capturing the highest performance results possible--when the conditions are right. Good leadership requires differentiating between team and nonteam opportunities, and then acting accordingly. Three litmus tests must be passed for a team at the top to be effective. First, the team must shape collective work-products--these are tangible performance results that the group can achieve working together that surpass what the team members could have achieved working on their own. Second, the leadership role must shift, depending on the task at hand. And third, the team's members must be mutually accountable for the group's results. When these criteria can be met, senior executives should come together to achieve real team performance. When the criteria cannot be met, they should rely on the individual leadership skills that they have honed over the years.

  12. The Top 10 Lists of 2011

    ERIC Educational Resources Information Center

    American School & University, 2011

    2011-01-01

    This article presents lists of the top ten schools with most students, largest enrollment, and other categories for 2011 in the U.S. The school districts with most student for 2010-2011 are New York City with 1,043,886 followed by Los Angeles with 667,251, Chicago with 403,770 and down to the 10th spot Orange County (Fla.) with 175,986. The…

  13. Top-Coating Silicon Onto Ceramic

    NASA Technical Reports Server (NTRS)

    Heaps, J. D.; Nelson, L. D.; Zook, J. D.

    1985-01-01

    Polycrystalline silicon for solar cells produced at low cost. Molten silicon poured from quartz trough onto moving carbon-coated ceramic substrate. Doctor blade spreads liquid silicon evenly over substrate. Molten material solidifies to form sheet of polycrystalline silicon having photovoltaic conversion efficiency greater than 10 percent. Method produces 100-um-thick silicon coatings at speed 0.15 centimeter per second.

  14. Top-down facilitation of visual recognition

    PubMed Central

    Bar, M.; Kassam, K. S.; Ghuman, A. S.; Boshyan, J.; Schmid, A. M.; Dale, A. M.; Hämäläinen, M. S.; Marinkovic, K.; Schacter, D. L.; Rosen, B. R.; Halgren, E.

    2006-01-01

    Cortical analysis related to visual object recognition is traditionally thought to propagate serially along a bottom-up hierarchy of ventral areas. Recent proposals gradually promote the role of top-down processing in recognition, but how such facilitation is triggered remains a puzzle. We tested a specific model, proposing that low spatial frequencies facilitate visual object recognition by initiating top-down processes projected from orbitofrontal to visual cortex. The present study combined magnetoencephalography, which has superior temporal resolution, functional magnetic resonance imaging, and a behavioral task that yields successful recognition with stimulus repetitions. Object recognition elicited differential activity that developed in the left orbitofrontal cortex 50 ms earlier than it did in recognition-related areas in the temporal cortex. This early orbitofrontal activity was directly modulated by the presence of low spatial frequencies in the image. Taken together, the dynamics we revealed provide strong support for the proposal of how top-down facilitation of object recognition is initiated, and our observations are used to derive predictions for future research. PMID:16407167

  15. Dark decay of the top quark

    DOE PAGES

    Kong, Kyoungchul; Lee, Hye -Sung; Park, Myeonghun

    2014-04-01

    We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 σ deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t → b W + Z's. This is the same as the dominant topmore » quark decay (t → b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. In addition, we discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.« less

  16. TOP500 Sublist for November 2001

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack J.; Simon,Horst D.

    2001-11-09

    18th Edition of TOP500 List of World's Fastest Supercomputers Released MANNHEIM, GERMANY; KNOXVILLE, TENN.; BERKELEY, CALIF. In what has become a much-anticipated event in the world of high-performance computing, the 18th edition of the TOP500 list of the world's fastest supercomputers was released today (November 9, 2001). The latest edition of the twice-yearly ranking finds IBM as the leader in the field, with 32 percent in terms of installed systems and 37 percent in terms of total performance of all the installed systems. In a surprise move Hewlett-Packard captured the second place with 30 percent of the systems. Most of these systems are smaller in size and as a consequence HP's share of installed performance is smaller with 15 percent. This is still enough for second place in this category. SGI, Cray and Sun follow in the number of TOP500 systems with 41 (8 percent), 39 (8 percent), and 31 (6 percent) respectively. In the category of installed performance Cray Inc. keeps the third position with 11 percent ahead of SGI (8 percent) and Compaq (8 percent).

  17. Tracking down hyper-boosted top quarks

    NASA Astrophysics Data System (ADS)

    Larkoski, Andrew J.; Maltoni, Fabio; Selvaggi, Michele

    2015-06-01

    The identification of hadronically decaying heavy states, such as vector bosons, the Higgs, or the top quark, produced with large transverse boosts has been and will continue to be a central focus of the jet physics program at the Large Hadron Collider (LHC). At a future hadron collider working at an order-of-magnitude larger energy than the LHC, these heavy states would be easily produced with transverse boosts of several TeV. At these energies, their decay products will be separated by angular scales comparable to individual calorimeter cells, making the current jet substructure identification techniques for hadronic decay modes not directly employable. In addition, at the high energy and luminosity projected at a future hadron collider, there will be numerous sources for contamination including initial- and final-state radiation, underlying event, or pile-up which must be mitigated. We propose a simple strategy to tag such "hyper-boosted" objects that defines jets with radii that scale inversely proportional to their transverse boost and combines the standard calorimetric information with charged track-based observables. By means of a fast detector simulation, we apply it to top quark identification and demonstrate that our method efficiently discriminates hadronically decaying top quarks from light QCD jets up to transverse boosts of 20 TeV. Our results open the way to tagging heavy objects with energies in the multi-TeV range at present and future hadron colliders.

  18. Tracking down hyper-boosted top quarks

    SciTech Connect

    Larkoski, Andrew J.; Maltoni, Fabio; Selvaggi, Michele

    2015-06-05

    The identification of hadronically decaying heavy states, such as vector bosons, the Higgs, or the top quark, produced with large transverse boosts has been and will continue to be a central focus of the jet physics program at the Large Hadron Collider (LHC). At a future hadron collider working at an order-of-magnitude larger energy than the LHC, these heavy states would be easily produced with transverse boosts of several TeV. At these energies, their decay products will be separated by angular scales comparable to individual calorimeter cells, making the current jet substructure identification techniques for hadronic decay modes not directly employable. In addition, at the high energy and luminosity projected at a future hadron collider, there will be numerous sources for contamination including initial- and final-state radiation, underlying event, or pile-up which must be mitigated. We propose a simple strategy to tag such "hyper-boosted" objects that defines jets with radii that scale inversely proportional to their transverse boost and combines the standard calorimetric information with charged track-based observables. By means of a fast detector simulation, we apply it to top quark identification and demonstrate that our method efficiently discriminates hadronically decaying top quarks from light QCD jets up to transverse boosts of 20 TeV. Lastly, our results open the way to tagging heavy objects with energies in the multi-TeV range at present and future hadron colliders.

  19. Observation of Single Top Quark Production

    SciTech Connect

    Gerber, Cecilia E.; /Illinois U., Chicago

    2009-09-01

    The author reports on the observation of electroweak production of single top quarks in p{bar p} collisions at {radical}s = 1.96 Tev using 2.3 fb{sup -1} of data collected with the D0 detector at the fermilab Tevatron Collider. Using events containing an isolated electron or muon, missing transverse energy, two, three or four jets, with one or two of them identified as originating from the fragmentation of a b quark, the measured cross section for the process p{bar p} {yields} tb + X, tqb + X is 3.94 {+-} 0.88 pb (for a top quark mass of 170 GeV). the probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10{sup -7}, corresponding to a 5.0 standard deviation significance. Using the same dataset, the measured cross sections for the t- and the s-channel processes when determined simultaneously with no assumption on their relative production rate are 3.14{sub -0.80}{sup +0.94} pb and 1.05 {+-} 0.81 pb respectively, consistent with standard model expectations. The measured t-channel cross section has a significance of 4.8 standard deviations, representing the first evidence for the production of an individual single top process to be detected.

  20. Tracking down hyper-boosted top quarks

    DOE PAGES

    Larkoski, Andrew J.; Maltoni, Fabio; Selvaggi, Michele

    2015-06-05

    The identification of hadronically decaying heavy states, such as vector bosons, the Higgs, or the top quark, produced with large transverse boosts has been and will continue to be a central focus of the jet physics program at the Large Hadron Collider (LHC). At a future hadron collider working at an order-of-magnitude larger energy than the LHC, these heavy states would be easily produced with transverse boosts of several TeV. At these energies, their decay products will be separated by angular scales comparable to individual calorimeter cells, making the current jet substructure identification techniques for hadronic decay modes not directlymore » employable. In addition, at the high energy and luminosity projected at a future hadron collider, there will be numerous sources for contamination including initial- and final-state radiation, underlying event, or pile-up which must be mitigated. We propose a simple strategy to tag such "hyper-boosted" objects that defines jets with radii that scale inversely proportional to their transverse boost and combines the standard calorimetric information with charged track-based observables. By means of a fast detector simulation, we apply it to top quark identification and demonstrate that our method efficiently discriminates hadronically decaying top quarks from light QCD jets up to transverse boosts of 20 TeV. Lastly, our results open the way to tagging heavy objects with energies in the multi-TeV range at present and future hadron colliders.« less