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Sample records for area csi photocathodes

  1. Status of large area CsI photocathode developments

    CERN Document Server

    Schyns, E M

    2002-01-01

    The development of large area reflective CsI photocathodes for RICH detectors is reviewed in the context of their production process and their performance. The quantum efficiencies of six large photocathodes recently produced by ALICE are compared with results available from the large photocathodes at HADES and STAR and with earlier R&D results obtained on small area samples. The CsI coating parameters and new developments in the domain of the production and the preparation of substrates are discussed in relation with the photocathode performance. (24 refs).

  2. Development of Large Area CsI Photocathodes for the ALICE/HMPID RICH Detector

    CERN Document Server

    Hoedlmoser, H; Schyns, E

    2005-01-01

    The work carried out within the framework of this PhD deals with the measurement of the photoelectric properties of large area thin film Cesium Iodide (CsI) photocathodes (PCs) which are to be used as a photon converter in a proximity focusing RICH detector for High Momentum Particle Identification (HMPID) in the ALICE experiment at the LHC. The objective was to commission a VUV-scanner setup for in-situ measurements of the photoelectric response of the CsI PCs immediately after the thin film coating process and the use of this system to investigate the properties of these photon detectors. Prior to this work and prior to the finalization of the ALICE/HMPID detector design, R&D work investigating the properties of CsI PCs had been performed at CERN and at other laboratories in order to determine possible substrates and optimized thin film coating procedures. These R&D studies were usually carried out with small samples on different substrates and with various procedures with sometimes ambiguous result...

  3. Recent results on the properties of CsI photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Berger, H. [Ecole Polytechnique Federale, Lausanne (Switzerland); Besson, P. [DAPNIA/SED, CEA, Saclay (France); Bourgeois, P. [DAPNIA/SED, CEA, Saclay (France); Braem, A. [European Organization for Nuclear Research, Geneva (Switzerland); Breskin, A. [Weizmann Institute, Rehovot (Israel); Buzulutskov, A. [Weizmann Institute, Rehovot (Israel); Chechik, R. [Weizmann Institute, Rehovot (Israel); Chesi, E. [European Organization for Nuclear Research, Geneva (Switzerland); Coluzza, C. [Ecole Polytechnique Federale, Lausanne (Switzerland); Ferreira-Marques, R. [LIP, Coimbra (Portugal); Friese, J. [Technical University, Munich (Germany); Gillitzer, A. [Technical University, Munich (Germany); Gustafsson, H.A. [University Hospital, Lund (Sweden). Dept. of Radiology; Hejny, W. [Giessen University, Giessen (Germany); Homolka, J. [Technical University, Munich (Germany); Kuehn, W. [Giessen University, Giessen (Germany); Ljubicic, A. Jr.; Maier-Komor, P.; Malamud, G.; Margaritondo, G.; Martinelli, R.; Di Mauro, A.; Mine, P.; Nappi, E.; Novotny, R.; Oskarsson, A.; Paic, G.; Piuz, F.; Policarpo, A.; Posa, F.; Peruzzo, L.; Ribeiro, R.S.; Riess, S.; Santiard, J.C.; Sartori, P.; Sartori, G.; Schukraft, J.; Scognetti, T.; Sgobba, S.; Svensson, O.; Tustonic, T.; Valentini, A.; Vartsky, D.; Vasileiadis, G.; Di Venere, F.; Zeitelhack, K.; CERN RD26 collaboration

    1995-06-01

    We report here on the results obtained by the CERN RD26 collaboration on the production and characterization of large area photocathodes, susceptible to equip fast UV-photon imaging devices. Such detectors are planned for some Ring Imaging Cherenkov (RICH) detector projects, in particular HADES at SIS Darmstadt, BABAR at the SLAC asymmetric B-factory, and ALICE at the LHC (CERN). (orig.).

  4. Structural transformation of CsI thin film photocathodes under exposure to air and UV irradiation

    CERN Document Server

    Tremsin, A S; Siegmund, O H W

    2000-01-01

    Transmission electron microscopy has been employed to study the structure of polycrystalline CsI thin films and its transformation under exposure to humid air and UV irradiation. The catastrophic degradation of CsI thin film photocathode performance is shown to be associated with the film dissolving followed by its re-crystallization. This results in the formation of large lumps of CsI crystal on the substrate surface, so that the film becomes discontinuous and its performance as a photocathode is permanently degraded. No change in the surface morphology and the film crystalline structure was observed after the samples were UV irradiated.

  5. Heat enhancement of radiation resistivity of evaporated CsI, KI and KBr photocathodes

    CERN Document Server

    Tremsin, A S

    2000-01-01

    The photoemissive stability of as-deposited and heat-treated CsI, KI and KBr evaporated thin films under UV radiation is examined in this paper. After the deposition, some photocathodes were annealed for several hours at 90 deg. C in vacuum and their performance was then compared to the performance of non-heated samples. We observed that the post-evaporation thermal treatment not only increases the photoyield of CsI and KI photocathodes in the spectral range of 115-190 nm, but also reduces CsI, KI and KBr photocurrent degradation that occurs after UV irradiation. KBr evaporated layers appeared to be more radiation-resistant than CsI and KI layers. Post-deposition heat treatment did not result in any significant variation of KBr UV sensitivity.

  6. Influence of bias voltage on the stability of CsI photocathodes exposed to air

    CERN Document Server

    Nitti, M A; Nappi, E; Singh, B K; Valentini, A

    2002-01-01

    We describe a possible correlation between the bias voltage applied to the substrate during the growth of CsI photocathodes and the variation of quantum efficiency (QE) after one day exposure to humid air. It was found that fresh samples are much less sensitive to humid air when a high negative bias voltage was applied during film growth. A model based on surface film interaction with water molecules is presented for the observed effect. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements have been performed to examine, respectively, the bulk structure and the surface of fresh and exposed CsI samples. Also reported are transmittance measurements for fresh and aged CsI samples in the wavelength range 190-850 nm.

  7. Optical and structural properties of CsI thin film photocathode

    OpenAIRE

    2014-01-01

    In the present work performance of cesium iodide thin film photocathode is studied in detail. The optical absorbance of cesium iodide thin films have been analyzed in the spectral range of 190 nm to 900 nm. The optical band gap energy of 500 nm thick cesium iodide film is calculated using Tauc plot from absorbance data. Refractive index is estimated from envelope plot of transmittance data using Swanepoel's method. Absolute quantum efficiency measurement has been carried out in the wavelength...

  8. Recent Progress in Research on CsI Thin Film Photocathodes%碘化铯薄膜光阴极的研究进展

    Institute of Scientific and Technical Information of China (English)

    樊龙; 黎宇坤; 陈韬; 李晋; 杨志文; 袁铮; 邓博; 曹柱荣; 胡昕

    2015-01-01

    碘化铯(CsI)薄膜因对X射线及紫外光具有高的光电转换效率而倍受关注。在核物理、高能物理以及天体物理研究的推动下,研制高量子效率(QE)、性能稳定的CsI薄膜光阴极成为了近年来研究的热点。然而,目前人们对某些影响其性能的因素还不完全清楚或确定。本文综述了CsI薄膜光阴极的最新研究进展,总结了影响QE的因素和光阴极的老化机理,重点关注了一些存在争议的问题,并对其研究发展方向进行了探讨。%Caesium iodide (CsI) thin films have attracted much attention due to good electron transport and emission properties in the soft X-ray and extreme ultraviolet range. With the rapid development of nuclear physics, high energy physics and astrophysics, the requirements for CsI film photocathodes become increasingly severe, and it is therefore of considerable interest to develop CsI photocathodes with high quantum efficiency (QE) and stable performance. However, the internal mechanisms of QE variation and photocathode aging are not entirely clear or certain up to date. In this paper, the recent progress on CsI film photocathodes is reviewed and some controversial issues are introduced. Several perspectives are also proposed in the end.

  9. Optical and structural properties of CsI thin film photocathode

    Science.gov (United States)

    Triloki; Rai, R.; Singh, B. K.

    2015-06-01

    In the present work, the performance of a cesium iodide thin film photocathode is studied in detail. The optical absorbance of cesium iodide films has been analyzed in the spectral range from 190 nm to 900 nm. The optical band gap energy of 500 nm thick cesium iodide film is calculated from the absorbance data using a Tauc plot. The refractive index is estimated from the envelope plot of transmittance data using Swanepoel's method. The absolute quantum efficiency measurement has been carried out in the wavelength range from 150 nm to 200 nm. The crystallographic nature and surface morphology are investigated by X-ray diffraction and transmission electron microscopy techniques. In addition, the elemental composition result obtained by energy dispersive X-ray analysis is also reported in the present work.

  10. A large area CsI RICH Detector in ALICE at LHC

    CERN Document Server

    Di Bari, D; Davenport, Martyn; Di Mauro, A; Elia, D; Ghidini, B; Grimaldi, A; Martinengo, P; Monno, E; Morsch, Andreas; Nappi, E; Paic, G; Piuz, François; Posa, F; Santiard, Jean-Claude; Stucchi, S; Tomasicchio, G; Williams, T D

    1999-01-01

    A 1m2 CsI RICH prototype has been successfully tested in a hadron beam at CERN SPS. The prototype, fully equipped with 15k electronic channels, has been used to identify particles coming from pi-Be interactions. Track reconstruction has been performed by using a telescope consisting of four gas pad chambers. A detailed description of the detector will be presented and results from the test will be discussed.List of figuresFigure 1 Expected proton and antiproton yields including jet quenching mechanism in central Pb-Pb collisions at LHC.Figure 2 Schematic view of the HMPID CsI-RICHFigure 3 Experimental layout used at the SPS/H4 test beamFigure 4 Distributions of the mean number, per ring, of pad hits (Npad), electrons (Ntot) and Cherenkov photoelectrons (Nres) as a function of the single-electron mean pulse heightFigure 5 Mean single-electron pulse height as a function of high voltage measured at the centre of each of the four photocathodesFigure 6 Evaluation of the uniformity of the chamber gain for the photo...

  11. CSI Index Of Customer's Satisfaction Applied In The Area Of Public Transport

    Science.gov (United States)

    Poliaková, Adela

    2015-06-01

    In Western countries, the new visions are applied in quality control for an integrated public transport system. Public transport puts the customer at the centre of our decision making in achieving customer satisfaction with provided service. Sustainable surveys are kept among customers. A lot of companies are collecting huge databases containing over 30,000 voices of customers, which demonstrates the current satisfaction levels across the public transport service. Customer satisfaction with a provided service is a difficult task. In this service, the quality criteria are not clearly defined, and it is therefore difficult to define customer satisfaction. The paper introduces a possibility of CSI index application in conditions of the Slovak Republic transport area.

  12. Review of the development of cesium iodide photocathodes for application to large RICH detectors

    CERN Document Server

    Almeida, J; Besson, P; Bourgeois, P; Braem, André; Breskin, Amos; Buzulutskov, A F; Chechik, R; Coluzza, C; Di Mauro, A; Friese, J; Homolka, J; Ljubicic, A; Margaritondo, G; Miné, P; Nappi, E; Dell'Orto, T; Paic, G; Piuz, François; Posa, F; Santiard, Jean-Claude; Sgobba, Stefano; Vasileiadis, G; Williams, T D

    1995-01-01

    CsI photocathodes were studied in order to evaluate their potential use as large photo converters in RICH detectors for the PID system of ALICE at LHC in heavy-ion collider mode. It has been demonstrated that a quantum efficiency close to the reference value obtained on small samples can be obtained on CsI layers evaporated on large pad electrodes operated in a MWPC at atmospheric pressure. We present a survey of the results obtained in the laboratory on small samples irradiated with UV-monochromatic beams and with large area RICH detectors of proximity-focusing geometry in a 3 GeV/c pion beam.

  13. A large area CsI RICH detector in ALICE at LHC

    CERN Document Server

    Di Bari, D; Davenport, Martyn; Di Mauro, A; Elia, D; Ghidini, B; Grimaldi, A; Martinengo, P; Monno, E; Morsch, Andreas; Nappi, E; Paic, G; Piuz, François; Posa, F; Santiard, Jean-Claude; Stucchi, S; Tomasicchio, G; Williams, T D

    1999-01-01

    A 1 m/sup 2/ CsI RICH prototype has been successfully tested in a hadron beam at CERN SPS. The prototype, fully equipped with 15 k electronic channels. has been used to identify particles coming from pi -Be interactions. Track reconstruction has been performed by using a telescope consisting of four gas pad chambers. A detailed description of the detector will be presented and results from test will be discussed. (6 refs).

  14. SUPERCONDUCTING PHOTOCATHODES.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY, J.; RAO, T.; WARREN, J.; SEKUTOWICZ, LANGNER, J.; STRZYZEWSKI, P.; LEFFERS, R.; LIPSKI, A.

    2005-10-09

    We present the results of our investigation of lead and niobium as suitable photocathode materials for superconducting RF injectors. Quantum efficiencies (QE) have been measured for a range of incident photon energies and a variety of cathode preparation methods, including various lead plating techniques on a niobium substrate. The effects of operating at ambient and cryogenic temperatures and different vacuum levels on the cathode QE have also been studied.

  15. Gallium Arsenide Photocathode Development

    Science.gov (United States)

    1975-10-01

    r ~\\ 1 1 AD-A018 619 ■ i I 1 GALLIUM ARSENIDE PHOTOCATHODE DEVELOPMENT I Terry Roach, et al 1 1 ■f EPSCO ...aiwiiwnHWlffl’Wip m, «swwerf^MW^S’ GALLIUM ARSENIDE PHOTOCATHODE DEVELOPMENT T. J. Roach Bianca Contractor: EPSCO Laboratories Contract Number: F08606...PHOTOCATHODE DEVELOPMENT 7. AUTHORfaJ T. Roach J. Bianca t. PERFORMING ORGANIZATION NAME AND AOORESS EPSCO Laboratories 227 High Ridge Road Stauford CT

  16. Piezoelectrically Enhanced Photocathodes

    Science.gov (United States)

    Beach, Robert A.; Nikzad, Shouleh; Bell, Lloyd Douglas; Strittmatter, Robert

    2011-01-01

    Doping of photocathodes with materials that have large piezoelectric coefficients has been proposed as an alternative means of increasing the desired photoemission of electrons. Treating cathode materials to increase emission of electrons is called "activation" in the art. It has been common practice to activate photocathodes by depositing thin layers of suitable metals (usually, cesium). Because cesium is unstable in air, fabrication of cesiated photocathodes and devices that contain them must be performed in sealed tubes under vacuum. It is difficult and costly to perform fabrication processes in enclosed, evacuated spaces. The proposed piezoelectrically enhanced photocathodes would have electron-emission properties similar to those of cesiated photocathodes but would be stable in air, and therefore could be fabricated more easily and at lower cost. Candidate photocathodes include nitrides of elements in column III of the periodic table . especially compounds of the general formula Al(x)Ga(1.x)N (where 0< or = x < or =.1). These compounds have high piezoelectric coefficients and are suitable for obtaining response to ultraviolet light. Fabrication of a photocathode according to the proposal would include inducement of strain in cathode layers during growth of the layers on a substrate. The strain would be induced by exploiting structural mismatches among the various constituent materials of the cathode. Because of the piezoelectric effect in this material, the strain would give rise to strong electric fields that, in turn, would give rise to a high concentration of charge near the surface. Examples of devices in which piezoelectrically enhanced photocathodes could be used include microchannel plates, electron- bombarded charge-coupled devices, image tubes, and night-vision goggles. Piezoelectrically enhanced photocathode materials could also be used in making highly efficient monolithic photodetectors. Highly efficient and stable piezoelectrically enhanced

  17. High Performance Photocathodes based on Molecular Beam Epitaxy Deposition for Next Generation Photo Detectors and Light Sources

    CERN Document Server

    Xie, Junqi; Wagner, Robert

    2013-01-01

    The development of high-performance photocathodes is a key challenge for future accelerator and particle physics applications. In this paper photocathode growth through molecular beam epitaxy is introduced as a promising technique to obtain robust, highly efficient alkali-antimonide based photocathodes. Recent research shows that the quantum efficiency of photocathodes can be significantly enhanced through control of the photocathode crystallinity. Molecular beam epitaxy allows for cost-effective growth of large-area photocathodes with excellent control of the stoichiometry and crystallinity, making photocathodes with peak quantum efficiencies exceeding 35% routine.

  18. Photoemission and optical constant measurements of Cesium Iodide thin film photocathode

    CERN Document Server

    Triloki,; Gupta, Nikita; Jammal, Nabeel F A; Singh, B K

    2014-01-01

    Performance of cesium iodide (CsI) as a reflective photocathode is presented. Absolute quantum efficiency (QE) measurement of 500 nm thick CsI film has been carried out in the wavelength range of 150 nm to 200 nm. Optical absorbance of 500 nm thick CsI film in the spectral range of 190 nm to 900 nm is analyzed and optical energy band gap is calculated using Tauc plot. To see the dispersive behavior of CsI film, refractive index has been determined by envelop plot of transmittance data, using Swanepoel method. Additional information on morphological and elemental composition results of CsI film, gained by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively are also reported in present work.

  19. Fast RICH Detector with a Caesium Iodide Photocathode at Atmospheric Pressure

    CERN Document Server

    Di Mauro, A; CERN. Geneva; Ljubicic, A; Paic, G; Piuz, François; Posa, F; Ribeiro, R S; Scognetti, T; Williams, T D

    1994-01-01

    CsI photocathodes of 30 30 cm2 size have been operated in a fast RICH detector composed of a NaF radiator and a multiwire proportional chamber with a cathode-pad readout. Results are presented from tests with a 3 GeV / c proton beam. A Cherenkov angular resolution of 8 mrad is obtained by detecting a mean of 8 photoelectrons per ring. Methods are described for counting the Cherenkov photon and evaluating the differential quantum efficiency of the CsI photocathode. The results obtained with photons impinging at a large angle on the CsI layer are presented and discussed in comparison with higher quantum efficiencies observed under different experimental conditions.

  20. RF Gun Photocathode Research at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Jongewaard, E.; Akre, R.; Brachmann, A.; Corbett, J.; Gilevich, S.; Grouev, K.; Hering, P.; P.Krejcik,; Lewandowski, J.; Loos, H.; Montagne, T.; Sheppard, J.C.; Stefan, P.; Vlieks, A.; Weathersby, S.; Zhou, F.; /SLAC

    2012-05-16

    LCLS is presently operating with a third copper photocathode in the original rf gun, with a quantum efficiency (QE) of {approx}1 x 10{sup -4} and projected emittance {gamma}{var_epsilon}{sub x,y} = 0.45 {micro}m at 250 pC bunch charge. The spare LCLS gun is installed in the SLAC Accelerator Structure Test Area (ASTA), fully processed to high rf power. As part of a wider photocathode R and D program, a UV laser system and additional gun diagnostics are being installed at ASTA to measure QE, QE lifetime, and electron beam emittance under a variety of operating conditions. The near-term goals are to test and verify the spare photocathode production/installation sequence, including transfer from the final holding chamber to the rf gun. Mid- and longer-term goals include development of a rigorous understanding of plasma and laser-assisted surface conditioning and investigation of new, high-QE photocathode materials. In parallel, an x-ray photoemission spectroscopy station is nearing completion, to analyze Cu photocathode surface chemistry. In this paper we review the status and anticipated operating parameters of ASTA and the spectroscopy test chamber.

  1. Structured photocathodes for improved high-energy x-ray efficiency in streak cameras

    Science.gov (United States)

    Opachich, Y. P.; Bell, P. M.; Bradley, D. K.; Chen, N.; Feng, J.; Gopal, A.; Hatch, B.; Hilsabeck, T. J.; Huffman, E.; Koch, J. A.; Landen, O. L.; MacPhee, A. G.; Nagel, S. R.; Udin, S.

    2016-11-01

    We have designed and fabricated a structured streak camera photocathode to provide enhanced efficiency for high energy X-rays (1-12 keV). This gold coated photocathode was tested in a streak camera and compared side by side against a conventional flat thin film photocathode. Results show that the measured electron yield enhancement at energies ranging from 1 to 10 keV scales well with predictions, and that the total enhancement can be more than 3×. The spatial resolution of the streak camera does not show degradation in the structured region. We predict that the temporal resolution of the detector will also not be affected as it is currently dominated by the slit width. This demonstration with Au motivates exploration of comparable enhancements with CsI and may revolutionize X-ray streak camera photocathode design.

  2. The CSI Schools Project

    Science.gov (United States)

    Dorling, Mark; Johnstone, Emm

    2012-01-01

    The popularity of forensic science in schools continues to grow alongside the proportion of prime time scheduling devoted to CSI television shows. Yet the understanding of how forensic tests are used in narrowing down a field of possible suspects to the point where just one can be arrested or taken to trial is far less well understood. Students…

  3. Review of the Development of Caesium Iodide Photocathodes for Application to Large RICH Detectors

    CERN Document Server

    Amadon, A; CERN. Geneva; Bourgeois, P; Braem, André; Breskin, Amos; Buzulutskov, A F; Chechik, R; Coluzza, C; Di Mauro, A; Friese, J; Homolka, J; Ljubicic, A; Margaritondo, G; Miné, P; Nappi, E; Dell'Orto, T; Paic, G; Piuz, François; Posa, F; Santiard, Jean-Claude; Sgobba, Stefano; Vasileiadis, G; Williams, T D

    1995-01-01

    CsI photocathodes were studied in order to evaluate their potential use as large photo converters in RICH detectors for the PID system at ALICE (LHC in heavy-ion collider mode). It has been demonstrated that a quantum efficiency comparable to the reference value obtained on small samples can be obtiained on CsI layers evaporated on large pad electrodes operated in a MWPC at atmospheric pressure. We present a survey of the results obtained in the laboratory on small samples irradiatedwtih UV-monochromatic beams and with RICH detectors of proximity-focusing geometry at a 3 GeV/c pion beam.

  4. Evaluation of various planar gaseous detectors with Cs1 photocathodes for the detection of primary scintillation light from noble gases

    CERN Document Server

    Periale, L; Carlson, Per J; Iacobaeus, C; Francke, T; Pavlopoulos, N; Pietropaoplo, F; Sokolova, T; Picchi, P

    2003-01-01

    Noble gases and liquids are excellent scintillators and this opens a unique opportunity to directly detect the primary scintillation light produced in these media by photons or particles. This signal can be used for several purposes, for example as a start signal for TPCs or for particle's identification. Usually photomultipliers (PMs) are used for the detection of the scintillation light. In our previous work we have demonstrated that costly PMs could be replaced by gaseous detectors with CsI photocathodes. Such detectors have the same quantum efficiency as the best PMs but at the same time are cheap, simple and have high position and time resolutions. The aim of this work is to evaluate various planar type gaseous detectors with CsI photocathodes in order to choose the best one for the detection of the primary scintillation light from noble gases and liquids. (10 refs).

  5. Enhanced Quantum Efficiency From Hybrid Cesium Halide/Copper Photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingmei; Joly, Alan G.; Droubay, Timothy C.; Gong, Yu; Hess, Wayne P.

    2014-04-28

    The quantum efficiency of Cu is found to increase dramatically when coated by a CsI film and then irradiated by a UV laser. Over three orders of magnitude quantum efficiency enhancement at 266 nm is observed in CsI/Cu(100), indicating potential application in future photocathode devices. Upon laser irradiation, a large work function reduction to a value less than 2 eV is also observed, significantly greater than for similarly treated CsBr/Cu(100). The initial QE enhancement, prior to laser irradiation, is attributed to interface interaction, surface cleanliness and the intrinsic properties of the Cs halide film. Further QE enhancement following activation is attributed to formation of inter-band states and Cs metal accumulation at the interface induced by laser irradiation.

  6. New Photocathode materials for electron-ion-colliders

    Energy Technology Data Exchange (ETDEWEB)

    Lukaszew, Rosa A. [College of William and Mary, Williamsburg, VA (United States)

    2015-02-25

    Our aim has been to explore new photocathode materials and schemes to develop strategies and technologies for next generation nuclear physics accelerator capabilities, particularly for Electron Ion Colliders (EIC). Thus, we investigated thin film deposition and ensuing properties for several adequate magnetic materials applicable to spin-polarized photocathodes. We also implemented a full experimental setup for light incidence at an acute angle onto the photocathode surface in order to excite surface Plasmon resonance hence increasing light absorption by a metallic surface. We successfully tested the setup with a thermionic cathode as well as Plasmonic silver-MgO samples and obtained very encouraging results. Our first results are very encouraging since the photocurrent measured on this preliminary plasmonic Ag-MgO sample under low power (~ 1mW) cw red light from a HeNe laser was 256 pA, thus two orders magnitude larger than that reported by others following also plasmonic approaches. We extended our studies to shorter wavelengths and we also started preliminary work on chemically ordered MnAl thin films –a component of the tertiary Ag-Mn-Al (silmanal) alloy in order to develop spin-polarized photocathodes capable of sustaining surface Plasmon resonance. It is worthwhile mentioning that a graduate student has been directly involved during this project ensuring the training of next generation of scientists in this area of research.

  7. Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard

    CERN Document Server

    Rabus, H; Richter, M; Ulm, G; Friese, J; Gernhäuser, R; Kastenmüller, A; Maier-Komor, P; Zeitelhack, K

    1999-01-01

    Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

  8. Final Report, Photocathodes for High Repetition Rate Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Zvi, Ilan [Stony Brook University

    2014-04-20

    This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-antimonide cathodes b) Development and testing of a diamond amplifier for photocathodes c) Tests of both cathodes in superconducting RF photoguns and copper RF photoguns

  9. The Census of Social Institutions (CSI): A Public Health Direct Observation Measure of Local Land Use

    Science.gov (United States)

    Hughey, Joseph; Randles, Anthony; Wall, Dustin; Peterson, N. Andrew; Jitnarin, Nattinee; Berkel, LaVerne; Eaton, Peter; Bowles, Doug; Haddock, C. Keith; Poston, W. S. Carlos

    2010-01-01

    This manuscript describes the development of the Census of Social Institutions (CSI), a reliable direct observation parcel-level built environment measure. The CSI was used to measure all non-residential parcels (n = 10,842) in 21 one-mile-radius neighborhoods centered around census block groups of varying income and ethnicity in a large metropolitan area. One year test-retest and inter-rater intra-class correlations showed high reliability for major use type and detail code observations. The CSI accurately captured the presence of about 9,500 uses, including 828 multiple major use and 431 mixed major use parcels that would have been missed in standard commercial databases. CSI data can be utilized to determine the health impacts of environmental settings. PMID:20386993

  10. Absorption of optical power in an S-20 photocathode

    CERN Document Server

    Harmer, S W

    2003-01-01

    By considering a monochromatic plane wave obliquely incident upon a planar layer of S-20 photocathode material, deposited upon a non-absorbing glass substrate, the distribution of optical power absorbed within the layer can be resolved. This is important to the question of photocathode efficiency, as the absorbed light excites photoelectrons within the photocathode which then may pass from the photocathode into the vacuum of the photomultiplier tube and be collected and multiplied. The calculation uses the measured complex permittivity of an extended red S-20 photocathode in the wavelength range, 375-900 nm. The results show that thin film effects are important within the photocathode, as they give rise to interesting power absorption profiles. This information is invaluable in predicting optimum photocathode thickness for wavelength selective applications. Electromagnetic waves that are obliquely incident upon the photocathode are also considered in both transverse electric and transverse magnetic polarizati...

  11. Photocathode device that replenishes photoemissive coating

    Energy Technology Data Exchange (ETDEWEB)

    Moody, Nathan A.; Lizon, David C.

    2016-06-14

    A photocathode device may replenish its photoemissive coating to replace coating material that desorbs/evaporates during photoemission. A linear actuator system may regulate the release of a replenishment material vapor, such as an alkali metal, from a chamber inside the photocathode device to a porous cathode substrate. The replenishment material deposits on the inner surface of a porous membrane and effuses through the membrane to the outer surface, where it replenishes the photoemissive coating. The rate of replenishment of the photoemissive coating may be adjusted using the linear actuator system to regulate performance of the photocathode device during photoemission. Alternatively, the linear actuator system may adjust a plasma discharge gap between a cartridge containing replenishment material and a metal grid. A potential is applied between the cartridge and the grid, resulting in ejection of metal ions from the cartridge that similarly replenish the photoemissive coating.

  12. Graphene shield enhanced photocathodes and methods for making the same

    Science.gov (United States)

    Moody, Nathan Andrew

    2014-09-02

    Disclosed are graphene shield enhanced photocathodes, such as high QE photocathodes. In certain embodiments, a monolayer graphene shield membrane ruggedizes a high quantum efficiency photoemission electron source by protecting a photosensitive film of the photocathode, extending operational lifetime and simplifying its integration in practical electron sources. In certain embodiments of the disclosed graphene shield enhanced photocathodes, the graphene serves as a transparent shield that does not inhibit photon or electron transmission but isolates the photosensitive film of the photocathode from reactive gas species, preventing contamination and yielding longer lifetime.

  13. Langley's CSI evolutionary model: Phase O

    Science.gov (United States)

    Belvin, W. Keith; Elliott, Kenny B.; Horta, Lucas G.; Bailey, Jim P.; Bruner, Anne M.; Sulla, Jeffrey L.; Won, John; Ugoletti, Roberto M.

    1991-01-01

    A testbed for the development of Controls Structures Interaction (CSI) technology to improve space science platform pointing is described. The evolutionary nature of the testbed will permit the study of global line-of-sight pointing in phases 0 and 1, whereas, multipayload pointing systems will be studied beginning with phase 2. The design, capabilities, and typical dynamic behavior of the phase 0 version of the CSI evolutionary model (CEM) is documented for investigator both internal and external to NASA. The model description includes line-of-sight pointing measurement, testbed structure, actuators, sensors, and real time computers, as well as finite element and state space models of major components.

  14. Measurements of photoelectron extraction efficiency from CsI into mixtures of Ne with CH4, CF4, CO2 and N2

    CERN Document Server

    Escada, J; Dias, T H V T; Lopes, J A M; Santos, J M F dos; Breskin, A

    2009-01-01

    Experimental measurements of the extraction efficiency f of the UV-induced photoelectrons emitted from a CsI photocathode into gas mixtures of Ne with CH4, CF4, CO2 and N2 are presented; they are compared with model-simulation results. Backscattering of low- energy photoelectrons emitted into noble gas is significantly reduced by the admixture of molecular gases, with direct impact on the effective quantum efficiency. Data are provided on the dependence of f on the type and concentration of the molecular gas in the mixtures and on the electric field.

  15. On the theory of photocathode rf guns

    Institute of Scientific and Technical Information of China (English)

    GAO Jie

    2009-01-01

    In this paper we give a set of analytical formulae to describe the characteristics of photocathode rf guns at any rf frequencies, such as energy, energy spread, bunch length, out going current, and emittance etc.as functions of the laser injection phase, which are useful in the design and practical operation of rf guns.

  16. A Summary of the 2010 Photocathode Physics for Photoinjectors Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Bazarov, I [Cornell University; Dowell, D [SLAC National Accelerator Laboratory; Hannon, Fay [Thomas Jefferson National Accelerator Facility; Harkay, K [Argonne National Laboratory; Garcia, C H [Thomas Jefferson National Accelerator Facility; Padmore, H [Lawrence Berkeley National Laboratory; Rao, T [Brookhaven National Laboratory; Smedley, J [Brookhaven National Laboratory

    2010-10-01

    This contribution contains a summary and some highlights from the Photocathode Physics for Photoinjectors (P3) Workshop [1]. This workshop, held at Brookhaven National Laboratory in Ocotber of 2010, was aimed at bringing the photocathode community together to discuss and explore the current state of the art in accelerator photocathodes, from both a theoretical and a materials science perspective. All types of photocathode materials were discussed, including metals, NEA and PEA semiconductors, and "designer" photocathodes with bespoke properties. Topics of the workshop included: Current status of photocathodes for accelerator applications Current fabrication methods Applications of modern materials science to the growth and analysis of cathodes Photoemission spectroscopy as a diagnostic of cathode performance Utilization of modern user facilities Photoemission theory Novel ideas in cathode development Discussion forum on future collaboration for cathode growth, analysis and testing

  17. Interaction of femtosecond laser pulses with metal photocathode

    Institute of Scientific and Technical Information of China (English)

    Liu Yun-Quan; Zhang Jie; Liang Wen-Xi

    2005-01-01

    The features of interaction of femtosecond laser pulses with photocathode are studied theoretically in this paper.The surface temperature of the metal cathode film while femtosecond laser pulses irradiation is studied with twotemperature model. With a simple photoelectric model we obtain the optimum metal film thickness for the backilluminated photocathode. The generated ultrashort photocurrent pulses are strongly dependent on the temperature of the electron gas and the lattice during the femtosecond laser pulse irradiation on the photocathode.

  18. Review of the Production Process of TTF and PITZ Photocathodes

    CERN Document Server

    Sertore, Daniele; Hui Han, Jang; Michelato, Paolo; Monaco, Laura; Schreiber, Siegfried

    2005-01-01

    In the present article, the production process of the photocathodes for the TESLA Test Facility (TTF) at DESY Hamburg and the Photo Injector Test Facility at DESY-Zeuthen (PITZ) is reviewed in order to highlight key elements for the final photocathode performances. Since the first photocathode production in 1998, we have continuosly collected relevant paramenters of the cathode plugs and deposition process. These data are now critically analized in view of an optimization of the photocathode performances for the next generation of high brilliance sources.

  19. PROGRESS ON LEAD PHOTOCATHODES FOR SUPERCONDUCTING INJECTORS.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY, J.; RAO, T.; SEKUTOWICZ, J.; KNEISEL, P.; LANGNER, J.; STRZYZEWSKI, P.; LEFFERTS, R.; LIPSKI, A.

    2005-05-16

    We present the results of our investigation of bulk lead, along with various types of lead films, as suitable photocathode materials for superconducting RF injectors. The quantum efficiency of each sample is presented as a function of the photon energy of the incident light, from 3.9 eV to 6.5 eV. Quantum efficiencies of 0.5% have been obtained. Production of a niobium cavity with a lead-plated cathode is underway.

  20. Progress on lead photocathodes for superconducting injectors

    Energy Technology Data Exchange (ETDEWEB)

    Smedley, John; Rao, Triveni; Sekutowicz, Jacek; Kneisel, Peter; Langner, J; Strzyzewski, P; Lefferts, Richard; Lipski, Andrzej

    2005-05-16

    We present the results of our investigation of bulk lead, along with various types of lead films, as suitable photocathode materials for superconducting RF injectors. The quantum efficiency of each sample is presented as a function of the photon energy of the incident light, from 3.9 eV to 6.5 eV. Quantum efficiencies of 0.5% have been obtained. Production of a niobium cavity with a lead plated cathode is underway.

  1. Kinetics of alkali-based photocathode degradation

    Science.gov (United States)

    Pavlenko, Vitaly; Liu, Fangze; Hoffbauer, Mark A.; Moody, Nathan A.; Batista, Enrique R.

    2016-11-01

    We report on a kinetic model that describes the degradation of the quantum efficiency (QE) of Cs3Sb and negative electron affinity (NEA) GaAs photocathodes under UHV conditions. In addition to the generally accepted irreversible chemical change of a photocathode's surface due to reactions with residual gases, such as O2, CO2, and H2O, the model incorporates an intermediate reversible physisorption step, similar to Langmuir adsorption. This intermediate step is needed to satisfactorily describe the strongly non-exponential QE degradation curves for two distinctly different classes of photocathodes -surface-activated and "bulk," indicating that in both systems the QE degradation results from surface damage. The recovery of the QE upon improvement of vacuum conditions is also accurately predicted by this model with three parameters (rates of gas adsorption, desorption, and irreversible chemical reaction with the surface) comprising metrics to better characterize the lifetime of the cathodes, instead of time-pressure exposure expressed in Langmuir units.

  2. A new imaging device based on UV scintillators and a large area gas photomultiplier

    Energy Technology Data Exchange (ETDEWEB)

    Sekiya, H., E-mail: sekiya@icrr.u-tokyo.ac.jp [Kamioka Observatory, Institute for Cosmic Ray Research, Univeristy of Tokyo, 456, Higashi-Mozumi Hida, Gifu 506-1205 (Japan); Kamioka Satellite, Institute for the Physics and Mathematics of the Universe, 456, Higashi-Mozumi Hida, Gifu 506-1205 (Japan); Ida, C.; Kubo, H.; Kurosawa, S.; Miuchi, K.; Tanimori, T.; Taniue, K. [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502 (Japan); Yoshikawa, A.; Yanagida, T.; Yokota, Y. [Institute of Multidisciplinary, Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba, Sendai, Miyagi 980-8577 (Japan); Fukuda, K.; Ishizu, S.; Kawaguchi, N.; Suyama, T. [Tokuyama Corporation, 3-3-1, Shibuya, Shibuya, Tokyo 150-8383 (Japan)

    2011-05-15

    A new type high spatial resolution radiation detector based on a UV scintillator+a UV imaging gas photomultiplier is presented. The prototype UV detector consists of a 10 cmx10 cm {mu}PIC, 2 GEMs and a semitransparent CsI photocathode deposited on a MgF{sub 2} window. The effective photo-sensitive area is {phi}34 mm and the readouts are 400 {mu}m pitch strips. A newly developed 20 mm size LaF{sub 3}(Nd) crystal which emits 172 nm photons is coupled to the detector for the first step. The detector was tested in pulse mode operation with 5.5 MeV {alpha} particles from {sup 241}Am. The single photoelectrons were successfully detected and the images of the crystal shape were clearly obtained.

  3. Developments of a large area VUV sensitive gas PMT with GEM/muPIC

    Energy Technology Data Exchange (ETDEWEB)

    Sekiya, H [Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, 456 Higashi-Mozumi, Hida, Gifu, 506-1205 (Japan); Ida, C; Kubo, H; Kurosawa, S; Tanimori, T [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake, Sakyo, Kyoto, 606-8502 (Japan); Yoshikawa, A; Yanagida, T; Yokota, Y [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, Miyagi, 980-8577 (Japan); Fukuda, K; Ishizu, S; Kawaguchi, N; Suyama, T, E-mail: sekiya@icrr.u-tokyo.ac.j [Tokuyama Corporation, 3-3-1 Shibuya, Shibuya, Tokyo, 150-8383 (Japan)

    2009-11-15

    A new large area UV photon detector with micro pattern gaseous detectors is developed and evaluated. A semitransparent CsI photocathode deposited on a MgF{sub 2} window was combined with 10cm x 10cm GEM and muPIC. Using Ar+C{sub 2}H{sub 6} (10%) gas, we achieved the gas gain of more than 10{sup 5} which is enough to detect single photoelectron. We, then, irradiated vacuum UV photons (VUV, around 172nm) from the newly developed LaF{sub 3}(Nd) scintillator to the detector and the single photoelectrons were successfully detected. We also demonstrated the imaging capability of the detector with muPIC readout systems.

  4. Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

    CERN Document Server

    Wisniewski, Eric; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff; Harkay, Katherine

    2012-01-01

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (~50 nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  5. Improvement of S-1 photocathode shelf life stability. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Fitts, R.W.

    1977-03-01

    The purpose of this program was to stabilize sensitivity of S-1 photocathodes in C73435AG high speed image converters. Variations in bulb pre- and post-heating and in aging were investigated using partial tube assemblies consisting of the cathode bulb half of the standard tube. Successful processing of stable S-1 photocathodes in partial tubes led to adapting the schedules to complete tube assemblies. Five tubes processed on this contract yielded high but unstable photocathode sensitivity. Continued testing of tubes being made to fill customer orders shows that control of tube heating and cooling, together with careful control of evaporated cesium, can yield stable S-1 photocathodes. Additional experimentation is required to optimize a schedule yielding consistently stable photocathodes.

  6. In Situ Observation of Dark Current Emission in a High Gradient rf Photocathode Gun

    Science.gov (United States)

    Shao, Jiahang; Shi, Jiaru; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Wang, Faya; Wisniewski, Eric

    2016-08-01

    Undesirable electron field emission (also known as dark current) in high gradient rf photocathode guns deteriorates the quality of the photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (˜100 μ m ) dark current imaging experiment has been performed in an L -band photocathode gun operating at ˜100 MV /m of surface gradient. Scattered strong emission areas with high current have been observed on the cathode. The field enhancement factor β of selected regions on the cathode has been measured. The postexaminations with scanning electron microscopy and white light interferometry reveal the origins of ˜75 % strong emission areas overlap with the spots where rf breakdown has occurred.

  7. TRIZ theory in NEA photocathode preparation system

    Science.gov (United States)

    Qiao, Jianliang; Huang, Dayong; Li, Xiangjiang; Gao, Youtang

    2016-09-01

    The solutions to the engineering problems were provided according to the innovation principle based on the theory of TRIZ. The ultra high vacuum test and evaluation system for the preparation of negative electron affinity (NEA) photocathode has the characteristics of complex structure and powerful functions. Segmentation principle, advance function principle, curved surface principle, dynamic characteristics principle and nested principle adopted by the design of ultra high vacuum test and evaluation system for cathode preparation were analyzed. The applications of the physical contradiction and the substance-field analysis method of the theory of TRIZ in the cathode preparation ultra high vacuum test and evaluation system were discussed.

  8. Photocathode microtron for laser wakefield acceleration experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kando, Masaki; Kotaki, Hideyuki; Kondo, Shuji; Hosokai, Tomonao; Kanazawa, Shuhei; Yokoyama, Takashi; Matoba, Toru; Nakajima, Kazuhisa [Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan). Kansai Research Establishment

    2001-10-01

    We are constructing a high quality electron beam injector that consists of a photocathode rf gun and a racetrack microtron. This injector will be used for the second generation laser wakefield acceleration experiment at JAERI-Kansai. Beam commissioning of the system started this March. We succeeded in generating a 150 MeV electron single bunch with a charge of 91 pC, an emittance of 4-6 {pi}mm-mrad, and a pulse length of 10 ps (rms). A detailed description of the measurements is presented. (author)

  9. Cesium-Telluride Photocathode No. 166

    CERN Document Server

    Barbiero, A; Elsener, K; Losito, R; CERN. Geneva. AB Department

    2007-01-01

    In the CERN photoemission laboratory, a Cs2 Te photocathode has been produced in December 2006. The co-evaporation of Cs and Te onto a copper substrate is observed with two quartz oscillator thickness monitors. The calibration of these monitors and the resulting Cs and Te layer thicknesses are described, and the calculated stoichiometric ratio of the sample is given. The quantum efficiency of cathode No. 166, measured using the cathode in a DC gun, has been found to be 6.2%.

  10. STATUS OF DIAMOND SECONDARY EMISSION ENHANCED PHOTOCATHODE

    Energy Technology Data Exchange (ETDEWEB)

    RAO,T.; BEN-ZVI, I.; CHANG, X.; GRIMES, J.; GROVER, R.; ISAKOVIC, A.; SMEDLEY, J.; TODD, R.; WARREN, J.; WU, Q.

    2007-05-25

    The diamond secondary emission enhanced photocathode (SEEP) provides an attractive alternative for simple photo cathodes in high average current electron injectors. It reduces the laser power required to drive the cathode, simultaneously isolating the cathode and the FW cavity from each other, thereby protecting them from contamination and increasing their life time. In this paper, we present the latest results on the secondary electron yield using pulsed thermionic and photo cathodes as primary electron sources, shaping the diamond using laser ablation and reactive ion etching as well as the theoretical underpinning of secondary electron generation and preliminary results of modeling.

  11. Electron beam generation from semiconductor photocathodes

    Science.gov (United States)

    Arneodo, F.; Cavanna, F.; De Mitri, I.; Mazza, D.; Nassisi, V.

    2001-01-01

    Several measurements on a variety of semiconductor photocathodes were performed in order to determine their photoelectric quantum efficiency. Two different excimer lasers (XeCl and KrCl) and a pulsed Xe lamp were used as light sources for electron photoextraction from doped and undoped samples of cadmiun telluride, indium antimonide, and indium phosphide. Large current densities were obtained up to the limit of the Child-Langmuir law. This suggests the use of these materials for the production of intense electron sources, which could also be used for purity measurements of noble liquids.

  12. Silver nanorod arrays for photocathode applications

    Energy Technology Data Exchange (ETDEWEB)

    Vilayurganapathy, Subramanian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Western Michigan Univ., Kalamazoo MI (United States); Nandasiri, Manjula I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Western Michigan Univ., Kalamazoo MI (United States); Joly, Alan G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); El-Khoury, Patrick Z. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Varga, Tamas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Coffey, Greg W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schwenzer, Birgit [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Pandey, Archana [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kayani, Asghar N. [Western Michigan Univ., Kalamazoo MI (United States); Hess, Wayne P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thevuthasan, Suntharampillai [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-10-16

    In this study, we explore the possibility of using plasmonic Ag nanorod arrays featuring enhanced photoemission as high-brightness photocathode material. Silver nanorod arrays are synthesized by the DC electrodeposition method and their dimensionality, uniformity, crystallinity and oxide/impurity content are characterized. These Ag nanorod arrays exhibit greatly enhanced two-photon photoemission under 400 nm femtosecond pulsed laser excitation. Plasmonic field enhancement in the array produces photoemission hot spots that are mapped using photoemission electron microscopy (PEEM). The relative photoemission enhancement of nanorod array hot spots relative to that of a flat Ag thin film is found to range between 102 and 3 x 103.

  13. Iterative Equalization and Interference Alignment for Multiuser MIMO HetNets with Imperfect CSI

    Directory of Open Access Journals (Sweden)

    Daniel Castanheira

    2015-01-01

    Full Text Available In this paper we consider a scenario, where several small-cells work under the same coverage area and spectrum of a macrocell. The signals stemming from the small-cell (macrocell users if not carefully dealt with will generate harmful interference into the macrocell (small-cell. To tackle this problem interference alignment and iterative equalization techniques are considered. By using IA all interference generated by the small-cell (macrocell users is aligned along a low dimensional subspace, at the macrocell (small-cells. This reduces considerably the amount of resources allocated, to enable the coexistence of the two systems. However, perfect IA requires the availability of error-free channel state information (CSI at the transmitters. Due to CSI errors one can have substantial performance degradation due to imperfect alignments. Since in this work the IA precoders are based on imperfect CSI, an efficient iterative space-frequency equalization is designed at the receiver side to cope with the residual aligned interference. The results demonstrate that iterative equalization is robust to imperfect CSI and removes efficiently the interference generated by the poorly aligned interference. Close to matched filter bound performance is achieved, with a very few number of iterations.

  14. Fast Padé Transform Accelerated CSI for Hyperpolarized MRS

    DEFF Research Database (Denmark)

    Hansen, Esben Szocska Søvsø; Kim, Sun; Miller, Jack J

    2016-01-01

    is to show the utility of FPT in reducing of the scan time required for hyperpolarized (13)C chemical shift imaging (CSI) without sacrificing the ability to resolve a full spectrum. Simulations, phantom, and in vivo hyperpolarized [1-(13)C] pyruvate CSI data were processed with FPT and compared...

  15. Kinetics of alkali-based photocathode degradation

    Directory of Open Access Journals (Sweden)

    Vitaly Pavlenko

    2016-11-01

    Full Text Available We report on a kinetic model that describes the degradation of the quantum efficiency (QE of Cs3Sb and negative electron affinity (NEA GaAs photocathodes under UHV conditions. In addition to the generally accepted irreversible chemical change of a photocathode’s surface due to reactions with residual gases, such as O2, CO2, and H2O, the model incorporates an intermediate reversible physisorption step, similar to Langmuir adsorption. This intermediate step is needed to satisfactorily describe the strongly non-exponential QE degradation curves for two distinctly different classes of photocathodes –surface-activated and “bulk,” indicating that in both systems the QE degradation results from surface damage. The recovery of the QE upon improvement of vacuum conditions is also accurately predicted by this model with three parameters (rates of gas adsorption, desorption, and irreversible chemical reaction with the surface comprising metrics to better characterize the lifetime of the cathodes, instead of time-pressure exposure expressed in Langmuir units.

  16. Sources of Emittance in RF Photocathode Injectors

    Energy Technology Data Exchange (ETDEWEB)

    Dowell, David H.; /SLAC

    2016-12-11

    Advances in electron beam technology have been central to creating the current generation of x-ray free electron lasers and ultra-fast electron microscopes. These once exotic devices have become essential tools for basic research and applied science. One important beam technology for both is the electron source which, for many of these instruments, is the photocathode RF gun. The invention of the photocathode gun and the concepts of emittance compensation and beam matching in the presence of space charge and RF forces have made these high-quality beams possible. Achieving even brighter beams requires a taking a finer resolution view of the electron dynamics near the cathode during photoemission and the initial acceleration of the beam. In addition, the high brightness beam is more sensitive to degradation by the optical aberrations of the gun’s RF and magnetic lenses. This paper discusses these topics including the beam properties due to fundamental photoemission physics, space charge effects close to the cathode, and optical distortions introduced by the RF and solenoid fields. Analytic relations for these phenomena are derived and compared with numerical simulations.

  17. Research on quantum efficiency of GaN wire photocathode

    Science.gov (United States)

    Xia, Sihao; Liu, Lei; Diao, Yu; Kong, Yike

    2017-02-01

    On the basis of three-dimensional continuity equation in semiconductors and finite difference method, the carrier concentration and the quantum efficiency of GaN wire photocathode as a function of incident photon energy are achieved. Results show that the quantum efficiency of the wire photocathode is largely enhanced compared with the conventional planar photocathode. The superiority of the wire photocathode is reflected in its structure with surrounding surfaces. The quantum efficiency of the wire photocathode largely depends on the wire width, surface reflectivity, surface escape probability and incident angle of light. The back interface recombination rate, however, has little influences on the quantum efficiency of the wire photocathode. The simulation results suggest that the optimal width for photoemission is 150-200 nm. Besides, the quantum efficiency increases and decreases linearly with increasing surface escape probability and surface reflectivity, respectively. With increasing ratio of wire spacing to wire height, the optimal incident angle of light is reduced. These simulations are expected to guide the preparation of a better performing GaN wire photocathode.

  18. The QE numerical simulation of PEA semiconductor photocathode

    CERN Document Server

    Li, Xudong; Zhang, Meng; Zhao, Minghua

    2011-01-01

    Several kinds of models have already been proposed for explaining the photoemission process. The exact photoemission theory of semiconductor photocathode was not well established after decades of research. In this paper an integral equation of quantum efficiency (QE) is constructed to describe the photoemission of positive electron affinity (PEA) semiconductor photocathode based on three-step photoemission model. The influences of forbidden gap, electron affinity, photon energy, incident angle, degree of polarization, refractive index, extinction coefficient, initial/final electron energy, relaxation time and external electric field on the QE of PEA semiconductor photocathode are taken into account. In addition, a computer code is also programmed to calculate the QE of K2CsSb photocathode theoretically at 532nm wavelength, the result is in line with the experimental value by and large. What are the reasons caused to the distinction between the experimental measuring and theoretical QE are discussed.

  19. A two-Frequency RF Photocathode Gun

    Energy Technology Data Exchange (ETDEWEB)

    Dowell, D.H. E-mail: dowell@slac.stanford.edu; Ferrario, M.; Kimura, T.; Lewellen, J.; Limborg, C.; Raimondi, P.; Schmerge, J.F.; Serafini, L.; Smith, T.; Young, L

    2004-08-01

    In this paper we resurrect an idea originally proposed by Serafini (Nucl. Instr. and Meth. A 318 (1992) 301) in 1992 for an RF photocathode gun capable of operating simultaneously at the fundamental frequency and a higher frequency harmonic. Driving the gun at two frequencies with the proper field ratio and relative phase produces a beam with essentially no RF emittance and a linear longitudinal phase space distribution. Such a gun allows a completely new range of operating parameters for controlling space charge emittance growth. In addition, the linear longitudinal phase space distribution aids in bunch compression. This paper will compare results of simulations for the two-frequency gun with the standard RF gun and the unique properties of the two-frequency gun will be discussed.

  20. Metal on metal oxide nanowire Co-catalyzed Si photocathode for solar water splitting.

    Science.gov (United States)

    Sun, Ke; Madsen, Kristian; Andersen, Pål; Bao, Weining; Sun, Zhelin; Wang, Deli

    2012-05-17

    We report a systematic study of Si|ZnO and Si|ZnO| metal photocathodes for effective photoelectrochemical cells and hydrogen generation. Both ZnO nanocrystalline thin films and vertical nanowire arrays were studied. Si|ZnO electrodes showed increased cathodic photocurrents due to improved charge separation by the formation of a p/n junction, and Si|ZnO:Al (n(+)-ZnO) and Si|ZnO(N(2)) (thin films prepared in N(2)/Ar gas) lead to a further increase in cathodic photocurrents. Si|ZnONW (nanowire array) photocathodes dramatically increased the photocurrents and thus photoelectrochemical conversion efficiency due to the enhanced light absorption and enlarged surface area. The ZnO film thickness and ZnO nanowire length were important to the enhancements. A thin metal coating on ZnO showed increased photocurrent due to a catalyzed hydrogen evolution reaction and Ni metal showed comparable catalytic activities to those of Pt and Pd. Moreover, photoelectrochemical instability of Si|ZnO electrodes was minimized by metal co-catalysts. Our results indicate that the metal and ZnO on p-type Si serve as co-catalysts for photoelectrochemical water splitting, which can provide a possible low-cost and scalable method to fabricate high efficiency photocathodes for practical applications in clean solar energy harvesting.

  1. Near atomically smooth alkali antimonide photocathode thin films

    CERN Document Server

    Feng, Jun; Nasiatka, James; Schubert, Susanne; Smedley, John; Padmore, Howard

    2016-01-01

    Nano-roughness limits the emittance of electron beams that can be generated by high efficiency photocathodes, such as the thermally reacted alkali antimonide thin films. However there is an urgent need for photocathodes that can produce an order of magnitude or more lower emittance than present day systems in order to increase the transverse coherence width of the electron beam. In this paper we demonstrate a method for producing alkali antimonide cathodes with near atomic smoothness with high reproducibility.

  2. High quantum efficiency S-20 photocathodes for photon counting applications

    CERN Document Server

    Orlov, Dmitry A; Pinto, Serge Duarte; Glazenborg, Rene; Kernen, Emilie

    2016-01-01

    Based on conventional S-20 processes, a new series of high quantum efficiency (QE) photocathodes has been developed that can be specifically tuned for use in the ultraviolet, blue or green regions of the spectrum. The QE values exceed 30% at maximum response, and the dark count rate is found to be as low as 30 Hz/cm2 at room temperature. This combination of properties along with a fast temporal response makes these photocathodes ideal for application in photon counting detectors.

  3. Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Wisniewski, Eric E., E-mail: ewisniew@anl.gov [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Velazquez, Daniel [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Yusof, Zikri, E-mail: zyusof@hawk.iit.edu [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Spentzouris, Linda; Terry, Jeff [Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Sarkar, Tapash J. [Rice University, 6100 Main, Houston, TX 77005 (United States); Harkay, Katherine [Accelerator Science Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States)

    2013-05-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light.

  4. MIMO channel capacity with full CSI at Low SNR

    KAUST Repository

    Tall, Abdoulaye

    2012-10-01

    In this paper, we characterize the ergodic capacity of Multiple Input Multiple Output (MIMO) Rayleigh fading channels with full channel state information (CSI) at both the transmitter (CSI-T) and the receiver (CSI-R) at asymptotically low signal-to-noise ratio (SNR). A simple analytical expression of the capacity is derived for any number of transmit and receive antennas. This characterization clearly shows the substantial gain in terms of capacity over the no CSI-T case and gives a good insight on the effect of the number of antennas used. In addition, an On-Off transmission scheme is proposed and is shown to be asymptotically capacity-achieving. © 2012 IEEE.

  5. Influence of varied doping structure on photoemissive property of photocathode

    Institute of Scientific and Technical Information of China (English)

    Niu Jun; Zhang Yi-Jun; Chang Ben-Kang; Xiong Ya-Juan

    2011-01-01

    The built-in electric fields within a varied doping GaAs photocathode may promote the transport of electrons from the bulk to the surface, thus the quantum efficiency of the cathode can be enhanced remarkably. But this enhancement,which might be due to the increase in either the number or the energy of electrons reaching the surface, is not clear at present. In this paper, the energy distributions of electrons in a varied doping photocathode and uniform doping photocathode before and after escaping from the cathode surface are analysed, and the number of electrons escaping from the surface in different cases is calculated for the two kinds of photocathodes. The results indicate that the varied doping structure can not only increase the number of electrons reaching the surface but also cause an offset of the electron energy distribution to high energy. That is the root reason for the enhancement of the quantum efficiency of a varied doping GaAs photocathode.

  6. Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T

    2011-08-04

    The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.

  7. The development of gaseous detectors with solid photocathodes for low temperature applications

    CERN Document Server

    Periale, L.; Iacobaeus, C.; Francke, T.; Lund-Jensen, B.; Pavlopoulos, N.; Picchi, P.; Pietropaolo, F.

    2004-01-01

    There are several applications and fundamental research areas which require the detection of VUV light at cryogenic temperatures. For these applications we have developed and successfully tested special designs of gaseous detectors with solid photocathodes able to operate at low temperatures: sealed gaseous detectors with MgF2 windows and windowless detectors. We have experimentally demonstrated, that both primary and secondary (due to the avalanche multiplication inside liquids) scintillation lights could be recorded by photosensitive gaseous detectors. The results of this work may allow one to significantly improve the operation of some noble liquid gas TPCs.

  8. Cold electron beams from cryo-cooled, alkali antimonide photocathodes

    CERN Document Server

    Cultrera, Luca; Lee, Hyeri; Liu, Xianghong; Bazarov, Ivan

    2015-01-01

    In this letter we report on the generation of cold electron beams using a Cs3Sb photocathode grown by co-deposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long standing speculation that the lattice temperature contribution limits the mean transverse energy or thermal emittance near the photoemission threshold, opening new frontiers in generating ultra-bright beams. At 90 K, we achieve a record low thermal emittance of 0.2 $\\mu$m (rms) per mm of laser spot diameter from an ultrafast (sub-picosecond) photocathode with quantum efficiency greater than $7\\times 10^{-5}$ using a visible laser wavelength of 690 nm.

  9. Polarized Photocathode R&D for Future Linear Collliders

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F; Brachmann, A.; Maruyama, T.; Sheppard, J.C.; /SLAC

    2009-01-23

    It is a challenge to generate full charge electrons from the electron sources without compromising polarization for the proposed ILC and CLIC. It is essential to advance polarized photocathodes to meet the requirements. SLAC has worldwide unique dedicated test facilities, Cathode Test System and dc-Gun Test Laboratory, to fully characterize polarized photocathodes. Recent systematic measurements on a strained-well InAlGaAs/AlGaAs cathode at the facilities show that 87% polarization and 0.3% QE are achieved. The QE can be increased to {approx}1.0% with atomic hydrogen cleaning. The surface charge limit at a very low current intensity and the clear dependence of the polarization on the surface charge limit are observed for the first time. On-going programs to develop photocathodes for the ILC and CLIC are briefly introduced.

  10. Photoemission of graded-doping GaN photocathode

    Institute of Scientific and Technical Information of China (English)

    Fu Xiao-Qian; Chang Ben-Kang; Wang Xiao-Hui; Li Biao; Du Yu-Jie; Zhang Jun-Ju

    2011-01-01

    We study the photoemission process of graded-doping GaN photocathode and find that the built-in electric fields can increase the escape probability and the effective diffusion length of photo-generated electrons, which results in the enhancement of quantum efficiency. The intervalley scattering mechanism and the lattice scattering mechanism in high electric fields are also investigated. To prevent negative differential mobility from appearing, the surface doping concentration needs to be optimized, and it is calculated to be 3.19×1017 cm-3. The graded-doping GaN photocathode with higher performance can be realized by further optimizing the doping profile.

  11. High quantum efficiency S-20 photocathodes in photon counting detectors

    Science.gov (United States)

    Orlov, D. A.; DeFazio, J.; Duarte Pinto, S.; Glazenborg, R.; Kernen, E.

    2016-04-01

    Based on conventional S-20 processes, a new series of high quantum efficiency (QE) photocathodes has been developed that can be specifically tuned for use in the ultraviolet, blue or green regions of the spectrum. The QE values exceed 30% at maximum response, and the dark count rate is found to be as low as 30 Hz/cm2 at room temperature. This combination of properties along with a fast temporal response makes these photocathodes ideal for application in photon counting detectors, which is demonstrated with an MCP photomultiplier tube for single and multi-photoelectron detection.

  12. A Monte Carlo study of backscattering effects in the photoelectron emission from CsI into CH$_{4}$ and Ar-CH$_{4}$ mixtures

    CERN Document Server

    Escada, J; Rachinhas, P J B M; Lopes, J A M; Santos, F P; Távora, L M N; Conde, C A N; Stauffer, A D

    2007-01-01

    Monte Carlo simulation is used to investigate photoelectron backscattering effects in the emission from a CsI photocathode into CH4 and Ar-CH4 mixtures for incident monochromatic photons with energies Eph in the range 6.8 eV to 9.8 eV (182 nm to 127 nm), and photons from a continuous VUV Hg(Ar) lamp with a spectral distribution peaked at Eph = 6.7 eV (185 nm), considering reduced applied electric fields E/N in the 0.1 Td to 40 Td range. The addition of CH4 to a noble gas efficiently increases electron transmission and drift velocity, due to vibrational excitation of the molecules at low electron energies. Results are presented for the photoelectron transmission efficiencies f, where f is the fraction of the number of photoelectrons emitted from CsI which are transmitted through the gas as compared to vacuum. The dependence of f on Eph, E/N, and mixture composition is analyzed and explained in terms of electron scattering in the different gas media, and results are compared with available measurements. Electro...

  13. Spatial Intercell Interference Cancellation with CSI Training and Feedback

    CERN Document Server

    Zhang, Jun; Letaief, Khaled B

    2011-01-01

    We investigate intercell interference cancellation (ICIC) with a practical downlink training and uplink channel state information (CSI) feedback model. The average downlink throughput for such a 2-cell network is derived. The user location has a strong effect on the signal-to-interference ratio (SIR) and the channel estimation error. This motivates adaptively switching between traditional (single-cell) beamforming and ICIC at low signal-to-noise ratio (SNR) where ICIC is preferred only with low SIR and accurate channel estimation, and the use of ICIC with optimized training and feedback at high SNR. For a given channel coherence time and fixed training and feedback overheads, we develop optimal data vs. pilot power allocation for CSI training as well as optimal feedback resource allocation to feed back CSI of different channels. Both analog and finite-rate digital feedback are considered. With analog feedback, the training power optimization provides a more significant performance gain than feedback optimizat...

  14. SUBSTRATE MATERIALS FOR POLY-CSiTF SOLAR CELLS:OPTIMIZATION OF SILICON SHEET FROM POWDER

    Institute of Scientific and Technical Information of China (English)

    Q. Ban; H. Shen; X.J. Wang; X.W. Zou; Z.C. Liang

    2005-01-01

    The optimization of silicon sheet from powder (SSP) technology as polycrystalline silicon thin film (poly-CSiTF) solar cells' substrate materials is studied by orthogonal design experimental method. Based on technological optimization of SSP prepared from electronic grade silicon powder, SSP solar cell devices with simple structure are prepared and the effect of SSP substrate is discussed. Up to now, the conversion efficiency of the prepared solar cells on low purity SSP substrate with fundamental structure has reached 8.25% (with area of 1 cm×1 cm).

  15. Experimental demonstration of a classical approach for flexible space structure control: NASA CSI testbeds

    Science.gov (United States)

    Bond, Wie

    1991-01-01

    The results of active control experiments performed for the Mini-Mast truss structure are presented. The primary research objectives were: (1) to develop active structural control concepts and/or techniques; (2) to verify the concept of robust non-minimum-phase compensation for a certain class of non-colocated structural control problems through ground experiments; (3) to verify a 'dipole' concept for persistent disturbance rejection control of flexible structures; and (4) to identify CSI (Control Structure Interaction) issues and areas of emphasis for the next generation of large flexible spacecraft. The classical SISO (Single Input and Single Output) control design approach was employed.

  16. Detection of Potential Induced Degradation in c-Si PV Panels Using Electrical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso

    2016-01-01

    Impedance spectroscopy (IS) is an established characterization method in different electrical and chemical research areas, but not yet adopted as a commercial diagnostic tool for PV panels. This work, for the first time, proposes an IS based method for detecting potential-induced degradation (PID......) in c-Si PV panels. The method has been experimentally tested using an automated PID test bed, and the IS results were confirmed using traditional current-voltage characterization methods, as well as electroluminescence imaging. The corroborated results confirm the effectiveness of the new approach...... to identify PID in PV panels....

  17. Photocathode-Uniformity Tests of the Hamamatsu R5912 Photomultiplier Tubes Used in the Milagro Experiment

    CERN Document Server

    Vasileiou, V; Smith, A J

    2007-01-01

    The Milagro experiment observes the extensive air showers produced by very high energy gamma-rays impacting the Earth's atmosphere. Milagro uses 898 Hamamatsu R5912 Photomultiplier Tubes. To complete our Monte Carlo simulations, we tested the photocathode uniformity of our PMTs. The main finding was that the PMT gain and detection efficiency are a function of the distance from the center of the photocathode. Both quantities become considerably smaller as the illumination position nears the edge of the photocathode.

  18. Quantum Efficiency Measurements of Femtosecond Vectorial Photoemission on Cu Photocathodes

    CERN Document Server

    Banfi, F; Galimberti, P G; Giannetti, C; Pagliara, S; Parmigiani, F; Pedersoli, E

    2005-01-01

    Quantum Efficiency (QE) measurements of single photon photoemission from a Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150~fs-6.28~eV laser pulses, are reported over a broad range of incidence angle in both s and p polarizations. The maximum value of QE for the Cu polycrystal sample is Y~4*10(-4), obtained with p polarization at an angle of incidence theta=65°. Our data confirm the vectorial photoemission model. Issues concerning surface roughness and symmetry considerations are addressed. An explanation in terms of non local conductivity tensor is proposed. Advantages of a 6.28~eV photon as compared to the standard 4.71~eV photon in use with Cu photocathodes are discussed.

  19. Femtosecond response time measurements of a Cs2Te photocathode

    CERN Document Server

    Aryshev, A; Honda, Y; Terunuma, N; Urakawa, J

    2015-01-01

    We present the response time measurements of a Cs2Te photocathode illuminated with two 100 fs duration, variable time separation laser pulses at 266 nm wavelength. The response time was confirmed in dispersive region downstream of a 12-cell standing wave S-band acceleration structure using a well-known RF zero-crossing technique. At the same time it was also measured by changing mechanical path-length difference between two micro-bunches. Both methods agree that Cs2Te photocathode time response is of the order of 250 fs and thereby it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result further opens a possibility to construct wide-range tunable THz FEL.

  20. Preparation of graphene/polymer composite photocathode for QDSSC

    Science.gov (United States)

    Wang, Qiandi; Shen, Yue; Tan, Jie; Xu, Kai; Shen, Tan; Cao, Meng; Gu, Feng; Wang, Linjun

    2013-12-01

    Graphene (rGO) was fabricated by modified Hummers method and a reducing process. Conductive polymer/graphene films were obtained by scalpel technology and used as photocathode in CdS quantum dot-sensitized solar cell (QDSSC). Polymers used in this paper were ethyl cellulose (EC), polyphenyl vinyl (PPV) and polyvinyl butyral (PVB), respectively. The obtained composite films were investigated by X-ray diffraction, Raman spectroscopy technology and scanning electron microscope (SEM). The photoelectric properties of QDSSCs were tested under AM 1.5 irradiation. Test results show that the film performance of the EC/rGO and PPV/rGO photocathode have been improved effectively. Power conversion efficiency (PCE) of the relative QDSSCs under AM 1.5 irradiation were 0.81% and 0.86%, respectively.

  1. Development of Advanced Models for 3D Photocathode PIC Simulations

    CERN Document Server

    Dimitrov, Dimitre; Cary, John R; Feldman, Donald; Jensen, Kevin; Messmer, Peter; Stoltz, Peter

    2005-01-01

    Codes for simulating photocathode electron guns invariably assume the emission of an idealized electron distribution from the cathode, regardless of the particular particle emission model that is implemented. The output of such simulations, a relatively clean and smooth distribution with very little variation as a function of the azimuthal angle, is inconsistent with the highly irregular and asymmetric electron bunches seen in experimental diagnostics. To address this problem, we have implemented a recently proposed theoretical model* that takes into account detailed solid-state physics of photocathode materials in the VORPAL particle-in-cell code.** Initial results from 3D simulations with this model and future research directions will be presented and discussed.

  2. Calculation of Electron Beam Potential Energy from RF Photocathode Gun

    CERN Document Server

    Liu Wan Ming; Power, John G; Wang, Haitao

    2005-01-01

    In this paper, we consider the contribution of potential energy to beam dynamics as simulated by PARMELA at low energies (10 - 30MeV). We have developed a routine to calculate the potential energy of the relativistic electron beam using the static coulomb potential in the rest frame (first order approximation as in PARMELA). We found that the potential energy contribution to the beam dynamics could be very significant, particularly with high charge beams generated by an RF photocathode gun. Our results show that when the potential energy is counted correctly and added to the kinetic energy from PARMELA, the total energy is conserved. Simulation results of potential and kinetic energies for short beams (~1 mm) at various charges (1 - 100 nC) generated by a high current RF photocathode gun are presented.

  3. Correlation of CsK2Sb photocathode lifetime with antimony thickness

    Directory of Open Access Journals (Sweden)

    M. A. Mamun

    2015-06-01

    Full Text Available CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

  4. Correlation of CsK{sub 2}Sb photocathode lifetime with antimony thickness

    Energy Technology Data Exchange (ETDEWEB)

    Mamun, M. A., E-mail: mmamu001@odu.edu; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States); The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, C.; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

    2015-06-01

    CsK{sub 2}Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

  5. Correlation of CsK2Sb photocathode lifetime with antimony thickness

    Energy Technology Data Exchange (ETDEWEB)

    Mamun, M. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Hernandez-Garcia, C. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

    2015-06-01

    CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

  6. Report of high quantum efficiency photocathode at Milano

    Energy Technology Data Exchange (ETDEWEB)

    Michelato, P. (INFN and University of Milano, Lab. LASA, Via F.lli Cervi 201, 2009, Segrate (Georgia))

    1992-07-01

    R D activity on high quantum efficiency alkali antimonide photocathode is in progress at Milano, in the context of the ARES program. Inside a preliminary preparation chamber, Cs[sub 3]Sb layers with qunatum efficiency up to 9% (at [lambda]=543.5 nm) and lifetime of some days has been recently produced on copper, stainless steel and niobium, using a reproducible deposition procedure adapted to the material of the different substrata.

  7. Thermal emittance measurements of a cesium potassium antimonide photocathode

    Science.gov (United States)

    Bazarov, Ivan; Cultrera, Luca; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Li, Yulin; Liu, Xianghong; Maxson, Jared; Roussel, William

    2011-05-01

    Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56±0.03 mm mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.

  8. Thermal emittance measurements of a cesium potassium antimonide photocathode

    CERN Document Server

    Bazarov, Ivan; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Li, Yulin; Liu, Xianghong; Maxson, Jared; Roussel, William

    2011-01-01

    Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56+/-0.03 mm-mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.

  9. Photoemission spectroscopy study of a multi-alkali photocathode

    CERN Document Server

    Ettema, A R H

    2000-01-01

    In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

  10. Electron optical mask projector with a photocathode for miniaturization

    Science.gov (United States)

    Moellenstedt, G.; Speidel, R.; Dostmann, M.; Martin, F.; Mayr, M.

    1981-06-01

    The projector was developed with an image converter consisting of a masked photocathode and a plane anode grid. The mask structure to be demagnified is on a quartz glass plate in a thin layer of Ti02 strongly absorbing ultraviolet light. A photoemissive layer is deposited by evaporation on the whole front side of the plate. For the demagnification of the electron image of the mask, a system is used consisting of two geometrically similar magnetic lenses in a telescopic arrangement.

  11. CSI Flight Computer System and experimental test results

    Science.gov (United States)

    Sparks, Dean W., Jr.; Peri, F., Jr.; Schuler, P.

    1993-01-01

    This paper describes the CSI Computer System (CCS) and the experimental tests performed to validate its functionality. This system is comprised of two major components: the space flight qualified Excitation and Damping Subsystem (EDS) which performs controls calculations; and the Remote Interface Unit (RIU) which is used for data acquisition, transmission, and filtering. The flight-like RIU is the interface between the EDS and the sensors and actuators positioned on the particular structure under control. The EDS and RIU communicate over the MIL-STD-1553B, a space flight qualified bus. To test the CCS under realistic conditions, it was connected to the Phase-0 CSI Evolutionary Model (CEM) at NASA Langley Research Center. The following schematic shows how the CCS is connected to the CEM. Various tests were performed which validated the ability of the system to perform control/structures experiments.

  12. Calibration of the BABAR CsI (Tl) calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Joerg, E-mail: marks@physi.uni-heidelberg.d [Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany)

    2009-04-01

    After nine years of operation, the BABAR experiment at the e{sup +}e{sup -} B factory PEP-II (Standford Linear Accelerator Center) stopped data taking in April 2008. An important part of the experiment is the electromagnetic calorimeter which consists of 6580 CsI crystals doped with thallium and read out by Si-PIN photodiodes. The light yield of the CsI crystals is changing in time due to radiation exposure. In addition to the changing light yield, passive material in front of and between the crystals as well as signal thresholds during the reconstruction influence the reconstructed energies. This requires a time-dependent calibration of the calorimeter. The calibration issues are reviewed and the calibration results obtained from various data samples are presented.

  13. Calibration of the BABAR CsI (Tl) calorimeter

    Science.gov (United States)

    Marks, Jörg; Calorimeter Group of BARBAR Collaboration

    2009-04-01

    After nine years of operation, the BABAR experiment at the e+e- B factory PEP-II (Standford Linear Accelerator Center) stopped data taking in April 2008. An important part of the experiment is the electromagnetic calorimeter which consists of 6580 CsI crystals doped with thallium and read out by Si-PIN photodiodes. The light yield of the CsI crystals is changing in time due to radiation exposure. In addition to the changing light yield, passive material in front of and between the crystals as well as signal thresholds during the reconstruction influence the reconstructed energies. This requires a time-dependent calibration of the calorimeter. The calibration issues are reviewed and the calibration results obtained from various data samples are presented.

  14. High-power CSI-fed induction motor drive with optimal power distribution based control

    Science.gov (United States)

    Kwak, S.-S.

    2011-11-01

    In this article, a current source inverter (CSI) fed induction motor drive with an optimal power distribution control is proposed for high-power applications. The CSI-fed drive is configured with a six-step CSI along with a pulsewidth modulated voltage source inverter (PWM-VSI) and capacitors. Due to the PWM-VSI and the capacitor, sinusoidal motor currents and voltages with high quality as well as natural commutation of the six-step CSI can be obtained. Since this CSI-fed drive can deliver required output power through both the six-step CSI and PWM-VSI, this article shows that the kVA ratings of both the inverters can be reduced by proper real power distribution. The optimal power distribution under load requirements, based on power flow modelling of the CSI-fed drive, is proposed to not only minimise the PWM-VSI rating but also reduce the six-step CSI rating. The dc-link current control of the six-step CSI is developed to realise the optimal power distribution. Furthermore, a vector controlled drive for high-power induction motors is proposed based on the optimal power distribution. Experimental results verify the high-power CSI-fed drive with the optimal power distribution control.

  15. Ultrafast laser direct hard-mask writing for high efficiency c-Si texture designs

    Directory of Open Access Journals (Sweden)

    Nogami Jun

    2013-03-01

    Full Text Available This study reports a high-resolution hard-mask laser writing technique to facilitate the selective etching of crystalline silicon (c-Si into an inverted-pyramidal texture with feature size and periodicity on the order of the wavelength which, thus, provides for both anti-reflection and effective light-trapping of infrared and visible light. The process also enables engineered positional placement of the inverted-pyramid thereby providing another parameter for optimal design of an optically efficient pattern. The proposed technique, a non-cleanroom process, is scalable for large area micro-fabrication of high-efficiency thin c-Si photovoltaics. Optical wave simulations suggest the fabricated textured surface with 1.3 μm inverted-pyramids and a single anti-reflective coating increases the relative energy conversion efficiency by 11% compared to the PERL-cell texture with 9 μm inverted pyramids on a 400 μm thick wafer. This efficiency gain is anticipated to improve further for thinner wafers due to enhanced diffractive light trapping effects.

  16. Novel Control Strategy for VSI and CSI Active Filters and Comparing These Two Types of Filters

    Directory of Open Access Journals (Sweden)

    Gholam Reza Arab

    2014-10-01

    Full Text Available Recently to eliminate the harmonics and improve the power factor of the power networks, much attention has been attracted to active filters. The advantages of these filters are lower volume and their better compensating characteristics than the passive filters. In conventional sliding mode controllers, the source current waveform is fluctuated in near to zero values. In this paper, using a new sliding technique, lower Total Harmonic Distortion (THD in source current is obtained and the current waveform is improved. As well as, two novel control strategies for two types of active filters, VSI and CSI is proposed and then these two types of filters are compared to reduce THD value of source current.The proposed controlled strategies are simulated by MATLAB/Simulink. The Simulation results confirm that the proposed strategies reduce the THD of source current more than other strategies, and active filter based on CSI has a better performance than active filter based on VSI with a dead time area (for avoiding short circuit of the source in high powers.

  17. Ultrafast laser direct hard-mask writing for high efficiency c-Si texture designs

    Science.gov (United States)

    Kumar, Kitty; Lee, Kenneth K. C.; Nogami, Jun; Herman, Peter R.; Kherani, Nazir P.

    2013-03-01

    This study reports a high-resolution hard-mask laser writing technique to facilitate the selective etching of crystalline silicon (c-Si) into an inverted-pyramidal texture with feature size and periodicity on the order of the wavelength which, thus, provides for both anti-reflection and effective light-trapping of infrared and visible light. The process also enables engineered positional placement of the inverted-pyramid thereby providing another parameter for optimal design of an optically efficient pattern. The proposed technique, a non-cleanroom process, is scalable for large area micro-fabrication of high-efficiency thin c-Si photovoltaics. Optical wave simulations suggest the fabricated textured surface with 1.3 μm inverted-pyramids and a single anti-reflective coating increases the relative energy conversion efficiency by 11% compared to the PERL-cell texture with 9 μm inverted pyramids on a 400 μm thick wafer. This efficiency gain is anticipated to improve further for thinner wafers due to enhanced diffractive light trapping effects.

  18. Extreme Makeover CSI edition: identity crimes, plastic bodies and genre hybridity in popular television

    OpenAIRE

    Bull, Sofia

    2015-01-01

    This article examines discourses on identity and bodily plasticity in the forensic crime drama CSI: Crime Scene Investigation (2000–). It argues that CSI engages with the same cultural debates as makeover reality TV, but in ways that articulate a number of oppositional perspectives on self-transformation practices governed by the programme's investment in an essentialist and determinist understanding of genetics. The article traces CSI's reconfiguration of the motif of disguise and inverted u...

  19. Kelvin probe studies of cesium telluride photocathode for the AWA photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, D.; Wisniewski, E. E.; Yusof, Z.; Harkay, K.; Spentzouris, L.; Terry, J. [Physics Department at Illinois Institute of Technology, Chicago, IL 60616 and High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Accelerator Science Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Physics Department at Illinois Institute of Technology, Chicago, IL 60616 (United States)

    2012-12-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (> 1%), is robust in a photoinjector, and long lifetime. This photocathode is fabricated in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch ({approx}50 nC) in a long bunch train. We present some results from a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV light exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  20. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  1. Thermal emittance and response time of a cesium antimonide photocathode

    Science.gov (United States)

    Cultrera, Luca; Bazarov, Ivan; Bartnik, Adam; Dunham, Bruce; Karkare, Siddharth; Merluzzi, Richard; Nichols, Matthew

    2011-10-01

    Measurements of the intrinsic emittance and response time of a Cs3Sb photocathode are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. Photoemission response time is evaluated using a RF deflecting cavity synchronized to a picosecond laser pulse train. We find that Cs3Sb has both small mean transverse energy, 160 ± 10 meV at 532 nm laser wavelength, and a prompt response time (below the resolution of our measurement) making it a suitable material for high brightness electron photoinjectors.

  2. Ultra-low emittance X-band photocathode RF gun

    Institute of Scientific and Technical Information of China (English)

    TANG Chuan-Xiang; LIU Xiao-Han

    2009-01-01

    In this paper,we present the simulation results of a 1.6 cell X-band photocathode RF gun for ultra-low emittance electron beams.It will work at 9.3 GHz.The emittance,bunch length,electron energy and energy spread at the gun exit are optimized at bunch charge of 1pC using PARMELA.Electron bunches type coupler is adopted in this gun and an initial simulation by MAFIA is also given in this paper.

  3. Compact THz radiation source based on photocathode RF gun

    Institute of Scientific and Technical Information of China (English)

    URAKAWA; JunJi

    2011-01-01

    Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. As a result of the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate an electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop.

  4. High voltage switch triggered by a laser-photocathode subsystem

    Science.gov (United States)

    Chen, Ping; Lundquist, Martin L.; Yu, David U. L.

    2013-01-08

    A spark gap switch for controlling the output of a high voltage pulse from a high voltage source, for example, a capacitor bank or a pulse forming network, to an external load such as a high gradient electron gun, laser, pulsed power accelerator or wide band radar. The combination of a UV laser and a high vacuum quartz cell, in which a photocathode and an anode are installed, is utilized as triggering devices to switch the spark gap from a non-conducting state to a conducting state with low delay and low jitter.

  5. Dye sensitised solar cells with nickel oxide photocathodes prepared via scalable microwave sintering.

    Science.gov (United States)

    Gibson, Elizabeth A; Awais, Muhammad; Dini, Danilo; Dowling, Denis P; Pryce, Mary T; Vos, Johannes G; Boschloo, Gerrit; Hagfeldt, Anders

    2013-02-21

    Photoactive NiO electrodes for cathodic dye-sensitised solar cells (p-DSCs) have been prepared with thicknesses ranging between 0.4 and 3.0 μm by spray-depositing pre-formed NiO nanoparticles on fluorine-doped tin oxide (FTO) coated glass substrates. The larger thicknesses were obtained in sequential sintering steps using a conventional furnace (CS) and a newly developed rapid discharge sintering (RDS) method. The latter procedure is employed for the first time for the preparation of p-DSCs. In particular, RDS represents a scalable procedure that is based on microwave-assisted plasma formation that allows the production in series of mesoporous NiO electrodes with large surface areas for p-type cell photocathodes. RDS possesses the unique feature of transmitting heat from the bulk of the system towards its outer interfaces with controlled confinement of the heating zone. The use of RDS results in a drastic reduction of processing times with respect to other deposition methods that involve heating/calcination steps with associated reduced costs in terms of energy. P1-dye sensitized NiO electrodes obtained via the RDS procedure have been tested in DSC devices and their performances have been analysed and compared with those of cathodic DSCs derived from CS-deposited samples. The largest conversion efficiencies (0.12%) and incident photon-to-current conversion efficiencies, IPCEs (50%), were obtained with sintered NiO electrodes having thicknesses of ~1.5-2.0 μm. In all the devices, the photogenerated holes in NiO live significantly longer (τ(h) ~ 1 s) than have previously been reported for P1-sensitized NiO photocathodes. In addition, P1-sensitised sintered electrodes give rise to relatively high photovoltages (up to 135 mV) when the triiodide-iodide redox couple is used.

  6. On X-Channels with Feedback and Delayed CSI

    CERN Document Server

    Tandon, Ravi; Poor, H Vincent; Shamai, Shlomo

    2012-01-01

    The sum degrees of freedom (DoF) of the two-user MIMO X-channel is characterized in the presence of output feedback and delayed channel state information (CSI). The number of antennas at each transmitters is assumed to be M and the number of antennas at each of the receivers is assumed to be N. It is shown that the sum DoF of the two-user MIMO X-channel is the same as the sum DoF of a two-user MIMO broadcast channel with 2M transmit antennas, and N antennas at each receiver. Hence, for this symmetric antenna configuration, there is no performance loss in the sum degrees of freedom due to the distributed nature of the transmitters. This result highlights the usefulness of feedback and delayed CSI for the MIMO X-channel. The K-user X-channel with single antenna at each transmitter and each receiver is also studied. In this network, each transmitter has a message intended for each receiver. For this network, it is shown that the sum DoF with partial output feedback alone is at least 2K/(K+1). This lower bound is...

  7. Perception-Induced Effects of Corporate Social Irresponsibility (CSiR) for Stereotypical and Admired Firms

    Science.gov (United States)

    Voliotis, Seraphim; Vlachos, Pavlos A.; Epitropaki, Olga

    2016-01-01

    How do stakeholders react to Corporate Social Irresponsibility (CSiR)? What are the emotional mechanisms and behavioral outcomes following CSiR perception? The psychology of CSR literature has yet to address these important questions and has largely considered CSR and CSiR as the opposite poles of the same continuum. In contrast, we view CSR and CSiR as distinct constructs and theorize about the cognitive (perceptual), emotional, and behavioral effects of CSiR activity on observers (i.e., primary and secondary stakeholders) building on theories of intergroup perception. Specifically, building on the Stereotype Content Model (SCM; Fiske et al., 2002) and the BIAS map (i.e., Behaviors from Intergroup Affect and Stereotypes; Cuddy et al., 2007)—which extends the SCM by predicting behavioral responses—we make predictions on potential stakeholder reactions to CSiR focusing on two practice-relevant cases: (a) a typical for-profit firm that engages in a CSiR activity, (b) an atypical admired firm that engages in CSiR activity. PMID:27445931

  8. Perception-Induced Effects of Corporate Social Irresponsibility (CSiR) for Stereotypical and Admired Firms.

    Science.gov (United States)

    Voliotis, Seraphim; Vlachos, Pavlos A; Epitropaki, Olga

    2016-01-01

    How do stakeholders react to Corporate Social Irresponsibility (CSiR)? What are the emotional mechanisms and behavioral outcomes following CSiR perception? The psychology of CSR literature has yet to address these important questions and has largely considered CSR and CSiR as the opposite poles of the same continuum. In contrast, we view CSR and CSiR as distinct constructs and theorize about the cognitive (perceptual), emotional, and behavioral effects of CSiR activity on observers (i.e., primary and secondary stakeholders) building on theories of intergroup perception. Specifically, building on the Stereotype Content Model (SCM; Fiske et al., 2002) and the BIAS map (i.e., Behaviors from Intergroup Affect and Stereotypes; Cuddy et al., 2007)-which extends the SCM by predicting behavioral responses-we make predictions on potential stakeholder reactions to CSiR focusing on two practice-relevant cases: (a) a typical for-profit firm that engages in a CSiR activity, (b) an atypical admired firm that engages in CSiR activity.

  9. Surface Science Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Shutthanandan, V.; Zhu, Zihua; Stutzman, Marcy L.; Hannon, Fay; Hernandez-Garcia, Carlos; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Thevuthasan, Suntharampillai; Hess, Wayne P.

    2012-06-12

    Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Several photocathode degradation processes are suspected, including defect formation by ion back bombardment, photochemistry of surface adsorbed species and irradiation-induced surface defect formation. To better understand the mechanisms of photocathode degradation, we have conducted surface and bulk analysis studies of two GaAs photocathodes removed from the FEL photoinjector after delivering electron beam for a few years. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, strained super-lattice GaAs photocathode samples, removed from the CEBAF photoinjector were analyzed using Transmission Electron Microscopy (TEM) and SIMS. This analysis of photocathode degradation during nominal photoinjector operating conditions represents first steps towards developing robust new photocathode designs necessary for generating sub-micron emittance electron beams required for both fourth generation light sources and intense polarized CW electron beams for nuclear and high energy physics facilities.

  10. Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Bragg Reflector

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shukui [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Stutzman, Marcy L. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Chen, Yiqiao [SVT Associates, Inc., Eden Prairie, MN (United States); Moy, Aaron [SVT Associates, Inc., Eden Prairie, MN (United States)

    2015-09-01

    Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.

  11. Cs2Te normal conducting photocathodes in the superconducting rf gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2010-01-01

    The superconducting radio frequency photoinjector (SRF gun) is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs2Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs2Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

  12. Laser ablation of CsI analyzed by delayed extraction

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Lima, F.; Collado, V.M.; Ponciano, C.R.; Farenzena, L.S.; Pedrero, E.; Silveira, E.F. da

    2003-07-15

    Secondary ion emission from polycrystalline CsI irradiated by pulsed-UV laser (337 nm) is analyzed by time-of-flight (TOF) mass spectrometry. Measurements were performed for different laser intensities and for several delayed extraction times (0-200 ns). The TOF peak shape is characterized by a Gaussian-like structure (fast component), followed by a tail (slow component) that is more pronounced when the extraction field is delayed. A thermal-sputtering uni-dimensional model is employed to describe the solid surface and plasma temperatures as a function of time. Heat diffusion, vapor photo-ionization, radiative emission and plume expansion are considered. Within the approximations used, the model predicts reasonable drift velocities of the plume ({approx}1.4 km s{sup -1}) but very high plasma temperatures ({approx}10{sup 5} K). The width of the TOF peak fast component allows determination of the plume temperature during its expansion.

  13. Measurement of Low Workfunction Cesiated Metals for Use in Dispenser Photocathodes

    CERN Document Server

    Moody, N A; O'Shea, P G

    2005-01-01

    Photoinjector performance is a limiting factor in the continued development of high powered FELs. Presently available photocathodes have limited efficiency and short lifetime in an RF-gun environment, due to contamination or evaporation of a photosensitive surface layer. An ideal photocathode should have high efficiency at visible wavelengths, long lifetime in practical vacuum environments, and prompt emission. High efficiency cathodes typically have limited lifetime, and the needs of the photocathode are generally at odds with those of the drive laser. A potential solution is the low work function dispenser cathode, where short lifetimes are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to methods used in the power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understanding and improving quantum efficiency and lifetime, analyzing issues of emi...

  14. Photogeneration of hydrogen from water by a robust dye-sensitized photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Shan, B.; Das, A. K.; Marquard, S.; Farnum, B. H.; Wang, D.; Bullock, R. M.; Meyer, T. J.

    2016-11-15

    We report here on a novel photocathode with a “donor-dye-catalyst” assembly structure for water reduction. The photoelectrocatalytic performance of the photocathode under mild conditions, with a photocurrent of -56 μA/cm2 and a Faradaic yield of 53%, is superior relative to other reported photocathodes with surface attached molecular catalysts. Detailed electron transfer analyses, based on transient absorption measurements, show that the successful application of this photocathode originates mainly from the slow back electron transfer following light excitation. The results also demonstrate that addition of the long-chain assembly to the macro-mesoporous electrode surface plays a fundamental role in providing sufficient catalyst for water reduction.

  15. Improvement of photoemission performance of a gradient-doping transmission-mode GaAs photocathode

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Jun; Niu Jun; Zhao Jing; Xiong Ya-Juan; Ren Ling; Chang Ben-Kang; Qian Yun-Sheng

    2011-01-01

    Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response,one has a gradient-doping structure and the other has a uniform-doping structure.The experimental results show that the gradient-doping photocathode can obtain a higher photoemission capability than the uniform-doping one. As a result of the downward graded band-bending structure,the cathode performance parameters,such as the electron average diffusion length and the surface electron escape probability obtained by fitting quantum yield curves,are greater for the gradient-doping photocathode.The electron diffusion length is within a range of from 2.0 to 5.4 μm for doping concentration varying from 1019 to 1018 cm-3 and the electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm.

  16. High-Efficiency GaN-Based UV Imaging Photocathodes for Application in Harsh Environments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is directed toward the development of innovative high-efficiency UV photocathodes based on the wide bandgap III-nitride semiconductors for reliable...

  17. Ultrafast laser pulse heating of metallic photocathodes and its contribution to intrinsic emittance

    CERN Document Server

    Maxson, J; Cultrera, L; Karkare, S; Padmore, H

    2016-01-01

    The heating of the electronic distribution of a copper photocathode is calculated under the two-temperature model for ultrafast laser illumination with fluences typical for use in RF photoinjectors. Using the finite temperature-extended relations for the photocathode intrinsic emittance and quantum efficiency, the time-dependent emittance growth due to this laser heating is calculated. This laser heating is seen to limit the intrinsic emittance achievable for photoinjectors using short laser pulses and low quantum efficiency metal photocathodes. A pump-probe photocathode experiment in a standard 1.6 cell S-band gun is proposed, in which simulations show the time dependent thermal emittance modulation from the laser heating can persist for meters downstream and, in principle, be measured using a slice emittance diagnostic.

  18. Nanomechanical and electrical properties of Nb thin films deposited on Pb substrates by pulsed laser deposition as a new concept photocathode for superconductor cavities

    Energy Technology Data Exchange (ETDEWEB)

    Gontad, F. [University of Salento, Department of Mathematics and Physics “E. De Giorgi”, 73100 Lecce (Italy); National Institute of Nuclear Physics, 73100 Lecce (Italy); Lorusso, A., E-mail: antonella.lorusso@le.infn.it [University of Salento, Department of Mathematics and Physics “E. De Giorgi”, 73100 Lecce (Italy); National Institute of Nuclear Physics, 73100 Lecce (Italy); Panareo, M.; Monteduro, A.G.; Maruccio, G. [University of Salento, Department of Mathematics and Physics “E. De Giorgi”, 73100 Lecce (Italy); National Institute of Nuclear Physics, 73100 Lecce (Italy); Broitman, E. [Thin Film Physics Division, IFM, Linköping University, 581-83 Linköping (Sweden); Perrone, A. [University of Salento, Department of Mathematics and Physics “E. De Giorgi”, 73100 Lecce (Italy); National Institute of Nuclear Physics, 73100 Lecce (Italy)

    2015-12-21

    We report a design of photocathode, which combines the good photoemissive properties of lead (Pb) and the advantages of superconducting performance of niobium (Nb) when installed into a superconducting radio-frequency gun. The new configuration is obtained by a coating of Nb thin film grown on a disk of Pb via pulsed laser deposition. The central emitting area of Pb is masked by a shield to avoid the Nb deposition. The nanomechanical properties of the Nb film, obtained through nanoindentation measurements, reveal a hardness of 2.8±0.3 GPa, while the study of the electrical resistivity of the film shows the appearance of the superconducting transitions at 9.3 K and 7.3 K for Nb and Pb, respectively, very close to the bulk material values. Additionally, morphological, structural and contamination studies of Nb thin film expose a very low droplet density on the substrate surface, a small polycrystalline orientation of the films and a low contamination level. These results, together with the acceptable Pb quantum efficiency of 2×10{sup −5} found at 266 nm, demonstrate the potentiality of the new concept photocathode. - Highlights: • Fabrication of hybrid Nb/Pb photocathodes for superconductive photoinjectors. • Nb thin films deposition by pulsed laser ablation on Pb substrates. • Characterization of nanomechanical properties of Nb thin films. • Characterization of electrical properties of Nb thin films.

  19. Relay Precoder Optimization in MIMO-Relay Networks With Imperfect CSI

    KAUST Repository

    Ubaidulla, P.

    2011-11-01

    In this paper, we consider robust joint designs of relay precoder and destination receive filters in a nonregenerative multiple-input multiple-output (MIMO) relay network. The network consists of multiple source-destination node pairs assisted by a MIMO-relay node. The channel state information (CSI) available at the relay node is assumed to be imperfect. We consider robust designs for two models of CSI error. The first model is a stochastic error (SE) model, where the probability distribution of the CSI error is Gaussian. This model is applicable when the imperfect CSI is mainly due to errors in channel estimation. For this model, we propose robust minimum sum mean square error (SMSE), MSE-balancing, and relay transmit power minimizing precoder designs. The next model for the CSI error is a norm-bounded error (NBE) model, where the CSI error can be specified by an uncertainty set. This model is applicable when the CSI error is dominated by quantization errors. In this case, we adopt a worst-case design approach. For this model, we propose a robust precoder design that minimizes total relay transmit power under constraints on MSEs at the destination nodes. We show that the proposed robust design problems can be reformulated as convex optimization problems that can be solved efficiently using interior-point methods. We demonstrate the robust performance of the proposed design through simulations. © 2011 IEEE.

  20. Downramp-assisted underdense photocathode electron bunch generation in plasma wakefield accelerators

    CERN Document Server

    Knetsch, Alexander; Wittig, Georg; Groth, Henning; Xi, Yunfeng; Deng, Aihua; Rosenzweig, James Benjamin; Bruhwiler, David Leslie; Smith, Johnathan; Jaroszynski, Dino Anthony; Sheng, Zheng-Ming; Manahan, Grace Gloria; Xia, Guoxing; Jamison, Steven; Hidding, Bernhard

    2014-01-01

    It is shown that the requirements for high quality electron bunch generation and trapping from an underdense photocathode in plasma wakefield accelerators can be substantially relaxed through localizing it on a plasma density downramp. This depresses the phase velocity of the accelerating electric field until the generated electrons are in phase, allowing for trapping in shallow trapping potentials. As a consequence the underdense photocathode technique is applicable by a much larger number of accelerator facilities. Furthermore, dark current generation is effectively suppressed.

  1. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    Energy Technology Data Exchange (ETDEWEB)

    Mulhollan, Gregory; /SLAC /Saxed Surface Science, Austin, TX

    2010-08-25

    We have developed an activation procedure by which the reactivity to CO{sub 2}, a principal cause of yield decay for GaAs photocathodes, is greatly reduced. The use of a second alkali in the activation process is responsible for the increased immunity of the activated surface. The best immunity was obtained by using a combination of Cs and Li without any loss in near bandgap yield. Optimally activated photocathodes have nearly equal quantities of both alkalis.

  2. Characterization of a superconducting Pb photocathode in a superconducting rf photoinjector cavity

    CERN Document Server

    Barday, R; Jankowiak, A; Kamps, T; Knobloch, J; Kugeler, O; Matveenko, A; Neumann, A; Schmeißer, M; Volker, J; Kneisel, P; Nietubyc, R; Schubert S; Smedley J; Sekutowicz, J; Will, I

    2014-01-01

    Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity to measure the quantum efficiency, its spatial distribution, and the work function. We will also discuss how the cathode surface contaminants modify the performance of the photocathode as well as the gun cavity and we discuss the possibilities to remove these contaminants.

  3. D10.7.2: Results for GaAs photocathodes

    CERN Document Server

    Xiang, R

    2013-01-01

    HZDR plans to apply bulk GaAs photocathode in SRF gun for high current electron source. Supported by this project, a preparation system for GaAs photocathode has been developed. The cathode plugs special for GaAs wafer have been modified and proofed in SRF gun real running conditions. Virgin GaAs wafer was tested in the SRF gun cavity, and the first GaAs activation was performed.

  4. CSI-FID: high throughput label-free detection of DNA binding molecules.

    Science.gov (United States)

    Hauschild, Karl E; Stover, James S; Boger, Dale L; Ansari, Aseem Z

    2009-07-15

    Determining the sequence specifity of DNA binding molecules is a non-trivial task. Here we describe the development of a platform for assaying the sequence specificity of DNA ligands using label free detection on high density DNA microarrays. This is achieved by combining Cognate Site Identification (CSI) with Fluorescence Intercalation Displacement (FID) to create CSI-FID. We use the well-studied small molecule DNA ligand netropsin to develop this high throughput platform. Analysis of the DNA binding properties of protein- and small molecule-based libraries with CSI-FID will advance the development of genome-anchored molecules for therapeutic purposes.

  5. Adsorption and revaporisation studies of thin iodine oxide and CsI aerosol deposits from containment surface materials in LWRs

    Energy Technology Data Exchange (ETDEWEB)

    Tietze, S.; Foreman, M.; Ekberg, C. [Chalmers Univ. of Technology, Goeteborg (Sweden); Kaerkelae, T.; Auvinen, A.; Tapper, U.; Jokiniemi, J. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-07-15

    speciation of the particles. The formation of HIO{sub 3} was verified with Raman analysis regardless of the reaction temperature. Furthermore, elemental iodine was also observed in the measured Raman spectra. Probably, iodine oxide particles had reacted with air humidity forming iodic acid and elemental iodine. IOx and CsI particles that were deposited on various sample surfaces were synthesized at 120 deg. C. According to XPS analysis, it seemed that IOx particles were mainly in form of HIO{sub 3} on the metal and on the painted surfaces. The XPS spectrum of CsI was observed on all metal and painted samples on which CsI particles were deposited. However, the CsI particles seemed to have dissolved at least partially by air humidity. Iodine was observed at areas outside the caesium iodide deposits on metal and on painted surfaces. According to the XPS analyses, iodine was in oxidised form. The measurements indicated that iodine may have reacted with the oxidized metal surfaces to form metal iodates. Only trace amounts of oxidized iodine were detected on the painted surfaces. An interesting result in the XPS analysis was that a part of the acquired signal from CsI on the painted surfaces seemed to originate deeper from the structure of the paint when it was pre-treated either with heat or gamma irradiation. SEM analysis revealed that heat and gamma irradiation treatment increased the porosity of the paint. Therefore, dissolved CsI may have been transported into the matrix of the paint. Besides copper the studied metal surfaces underwent slow reactions with the iodine of the aerosol deposits which showed in the high revaporisation rates at room temperature and elevated temperatures. On the copper and paint samples it could be shown that these surfaces react more easily with the iodine from cesium iodide deposits. From the chemically converted metal iodides only copper iodide remained on the surfaces after exposure to hot humid air and as well after immersion in boiling water

  6. Adsorption and revaporisation studies of thin iodine oxide and CsI aerosol deposits from containment surface materials in LWRs

    Energy Technology Data Exchange (ETDEWEB)

    Tietze, S.; Foreman, M.; Ekberg, C. [Chalmers Univ. of Technology, Goeteborg (Sweden); Kaerkelae, T.; Auvinen, A.; Tapper, U.; Jokiniemi, J. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-07-15

    speciation of the particles. The formation of HIO{sub 3} was verified with Raman analysis regardless of the reaction temperature. Furthermore, elemental iodine was also observed in the measured Raman spectra. Probably, iodine oxide particles had reacted with air humidity forming iodic acid and elemental iodine. IOx and CsI particles that were deposited on various sample surfaces were synthesized at 120 deg. C. According to XPS analysis, it seemed that IOx particles were mainly in form of HIO{sub 3} on the metal and on the painted surfaces. The XPS spectrum of CsI was observed on all metal and painted samples on which CsI particles were deposited. However, the CsI particles seemed to have dissolved at least partially by air humidity. Iodine was observed at areas outside the caesium iodide deposits on metal and on painted surfaces. According to the XPS analyses, iodine was in oxidised form. The measurements indicated that iodine may have reacted with the oxidized metal surfaces to form metal iodates. Only trace amounts of oxidized iodine were detected on the painted surfaces. An interesting result in the XPS analysis was that a part of the acquired signal from CsI on the painted surfaces seemed to originate deeper from the structure of the paint when it was pre-treated either with heat or gamma irradiation. SEM analysis revealed that heat and gamma irradiation treatment increased the porosity of the paint. Therefore, dissolved CsI may have been transported into the matrix of the paint. Besides copper the studied metal surfaces underwent slow reactions with the iodine of the aerosol deposits which showed in the high revaporisation rates at room temperature and elevated temperatures. On the copper and paint samples it could be shown that these surfaces react more easily with the iodine from cesium iodide deposits. From the chemically converted metal iodides only copper iodide remained on the surfaces after exposure to hot humid air and as well after immersion in boiling water

  7. Gábor Munkácsi tekstiilid Tallinnas / Kadi Raudalainen

    Index Scriptorium Estoniae

    Raudalainen, Kadi

    1999-01-01

    22. okt.-st Lühikese jala galeriis ungari tekstiilikunstniku Gábor Munkácsi tööde näitus. Enamik tekstiilidest on valmistatud igivanas ikat-tehnikas. Eksponeeritud kardinad, seinatekstiilid, laudlinad

  8. Enhanced quantum efficiency for CsI grown on a graphite-based substrate coating

    CERN Document Server

    Friese, J; Homolka, J; Kastenmüller, A; Maier-Komor, P; Peter, M; Zeitelhack, K; Kienle, P; Körner, H J

    1999-01-01

    Quantum efficiencies (QE) in the vacuum ultraviolet (VUV) wavelength region have been measured for solid CsI layers on various substrates. The CsI films were deposited applying electron beam evaporation. The QE measurements were performed utilizing synchrotron radiation as well as light from a deuterium lamp. A GaAsP diode with a sensitivity calibration traceable to a primary radiation standard was used for normalization. For CsI layers grown on resin-stabilized graphite films a significant enhancement of QE was observed. Substrates suitable for gas detector applications and aging properties were investigated. The procedures to prepare and reproduce high quantum efficient CsI layers are described.

  9. Tracing bloodlines: kinship and reproduction under investigation in CSI: Crime Scene Investigation

    OpenAIRE

    Bull, Sofia

    2014-01-01

    This article examines discourses on kinship and reproduction in the forensic crime drama CSI: Crime Scene Investigation (2000–). I argue that the programme stages a visual materialization of genetic kinship in order to assert its importance as a crucial type of forensic evidence, which evokes the traditional Darwinian framework of genealogy for understanding biological kinship as a substantial and enduring trace between generations. However, I show that CSI also participates in contemporary b...

  10. Surface science analysis of GaAs photocathodes following sustained electron beam delivery

    Energy Technology Data Exchange (ETDEWEB)

    Carlos Hernandez-Garcia, Fay Hannon, Marcy Stutzman, V. Shutthanandan, Z. Zhu, M. Nandasri, S. V. Kuchibhatla, S. Thevuthasan, W. P. Hess

    2012-06-01

    Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Photocathode quantum efficiency (QE) degradation is due to residual gasses in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector and one unused, were also analyzed using Transmission Electron Microscopy (TEM) and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but shows evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

  11. Comparative research on the transmission-mode GaAs photocathodes of exponential-doping structures

    Institute of Scientific and Technical Information of China (English)

    Chen Liang; Qian Yun-Sheng; Zhang Yi-Jun; Chang Ben-Kang

    2012-01-01

    Early research has shown that the varied doping structures of the active layer of GaAs photocathodes have beenproven to have a higher quantum efficiency than uniform doping structures.On the basis of our early research on the surface photovoltage of GaAs photocathodes,and comparative research before and after activation of reflection-mode GaAs photocathodes,we further the comparative research on transmission-mode GaAs photocathodes.An exponential doping structure is the typical varied doping structure that can form a uniform electric field in the active layer.By solving the one-dimensional diffusion equation for no equilibrium minority carriers of transmission-mode GaAs photocathodes of the exponential doping structure,we can obtain the equations for the surface photovoltage (SPV) curve before activation and the spectral response curve (SRC) after activation.Through experiments and fitting calculations for the designed material,the body-material parameters can be well fitted by the SPV before activation,and proven by the fitting calculation for SRC after activation.Through the comparative research before and after activation,the average surface escape probability (SEP) can also be well fitted. This comparative research method can measure the body parameters and the value of SEP for the transmission-mode GaAs photocathode more exactly than the early method,which only measures the body parameters by SRC after activation.It can also help us to deeply study and exactly measure the parameters of the varied doping structures for transmission-mode GaAs photocathodes,and optimize the Cs-O activation technique in the future.

  12. Energy-Efficient Relaying over Multiple Slots with Causal CSI

    CERN Document Server

    Ho, Chin Keong; Sun, Sumei

    2012-01-01

    In many communication scenarios, such as in cellular systems, the energy cost is substantial and should be conserved, yet there is a growing need to support many real-time applications that require timely data delivery. To model such a scenario, in this paper we consider the problem of minimizing the expected sum energy of delivering a message of a given size from a source to a destination subject to a deadline constraint. A relay is present and can assist after it has decoded the message. Causal channel state information (CSI), in the form of present and past SNRs of all links, is available for determining the optimal power allocation for the source and relay. We obtain the optimal power allocation policy by dynamic programming and explore its structure. We also obtain conditions for which the minimum expected sum energy is bounded given a general channel distribution. In particular, we show that for Rayleigh and Rician fading channels, relaying is necessary for the minimum expected sum energy to be bounded....

  13. Joint Langley Research Center/Jet Propulsion Laboratory CSI experiment

    Science.gov (United States)

    Neat, Gregory W.; O'Brien, John F.; Lurie, Boris J.; Garnica, Angel; Belvin, W. K.; Sulla, Jeff; Won, John

    1992-01-01

    This paper describes a joint Control Structure Interaction (CSI) experiment in which Jet Propulsion Laboratory (JPL) damping devices were incorporated into the Langley Research Center (LaRC) Phase 0 Testbed. The goals of the effort were twofold: (1) test the effectiveness of the JPL structural damping methods in a new structure and (2) assess the feasibility of combining JPL local control methods with the LaRC multiple input multiple output global control methods. Six dampers (2 piezoelectric active members, 4 viscous dampers), placed in three different regions of the structure, produced up to 26 dB attenuation in target modes. The combined control strategy in which the JPL damping methods contributed local control action and the LaRC control scheme provided global control action, produced and overall control scheme with increased stability margins and improved performance. This paper presents an overview of the technologies contributed from the two centers, the strategies used to combine them, and results demonstrating the success of the damping and cooperative control efforts.

  14. Radiation hardness test of un-doped CsI crystals and Silicon Photomultipliers for the Mu2e calorimeter

    CERN Document Server

    Baccaro, Stefania; Cordelli, Marco; Diociaiuti, Eleonora; Donghia, Raffaella; Giovannella, Simona; Loreti, Stefano; Miscetti, Stefano; Pillon, Mario; Sarra, Ivano

    2016-01-01

    The Mu2e calorimeter is composed by 1400 un-doped CsI crystals coupled to large area UV extended Silicon Photomultipliers arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position. It should also be fast enough to handle the high rate background and it must operate and survive in a high radiation environment. Simulation studies estimated that, in the hottest regions, each crystal will absorb a dose of 300 Gy and will be exposed to a neutron fluency of 6 x 10^{11} n/cm^2 in 3 years of running. Test of un-doped CsI crystals irradiated up to 900 Gy and to a neutron fluency up to 9 x 10^{11} n/cm^2 have been performed at CALLIOPE and FNG ENEA facilities in Italy. We present our study on the variation of light yield (LY) and longitudinal response uniformity (LRU) of these crystals after irradiation. The ionization dose does not modify LRU while a 20% reduction in LY is observed at 900 Gy. Similarly, the neutron flux causes an acceptable LY deterioration (<...

  15. Non-conventional photocathodes based on Cu thin films deposited on Y substrate by sputtering

    Science.gov (United States)

    Perrone, A.; D'Elia, M.; Gontad, F.; Di Giulio, M.; Maruccio, G.; Cola, A.; Stankova, N. E.; Kovacheva, D. G.; Broitman, E.

    2014-07-01

    Copper (Cu) thin films were deposited on yttrium (Y) substrate by sputtering. During the deposition, a small central area of the Y substrate was shielded to avoid the film deposition and was successively used to study its photoemissive properties. This configuration has two advantages: the cathode presents (i) the quantum efficiency and the work function of Y and (ii) high electrical compatibility when inserted into the conventional radio-frequency gun built with Cu bulk. The photocathode was investigated by scanning electron microscopy to determine surface morphology. X-ray diffraction and atomic force microscopy studies were performed to compare the structure and surface properties of the deposited film. The measured electrical resistivity value of the Cu film was similar to that of high purity Cu bulk. Film to substrate adhesion was also evaluated using the Daimler-Benz Rockwell-C adhesion test method. Finally, the photoelectron performance in terms of quantum efficiency was obtained in a high vacuum photodiode cell before and after laser cleaning procedures. A comparison with the results obtained with a twin sample prepared by pulsed laser deposition is presented and discussed.

  16. Non-conventional photocathodes based on Cu thin films deposited on Y substrate by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Perrone, A. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); D’Elia, M. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); National Institute of Nuclear Physics and University of Salento, 73100 Lecce (Italy); Di Giulio, M.; Maruccio, G. [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, 73100 Lecce (Italy); Cola, A. [National Council Research, Institute for Microelectronics and Microsystems, 73100 Lecce (Italy); Stankova, N.E. [Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Kovacheva, D.G. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)

    2014-07-01

    Copper (Cu) thin films were deposited on yttrium (Y) substrate by sputtering. During the deposition, a small central area of the Y substrate was shielded to avoid the film deposition and was successively used to study its photoemissive properties. This configuration has two advantages: the cathode presents (i) the quantum efficiency and the work function of Y and (ii) high electrical compatibility when inserted into the conventional radio-frequency gun built with Cu bulk. The photocathode was investigated by scanning electron microscopy to determine surface morphology. X-ray diffraction and atomic force microscopy studies were performed to compare the structure and surface properties of the deposited film. The measured electrical resistivity value of the Cu film was similar to that of high purity Cu bulk. Film to substrate adhesion was also evaluated using the Daimler–Benz Rockwell-C adhesion test method. Finally, the photoelectron performance in terms of quantum efficiency was obtained in a high vacuum photodiode cell before and after laser cleaning procedures. A comparison with the results obtained with a twin sample prepared by pulsed laser deposition is presented and discussed.

  17. Study of silicon tip photocathodes in DC and RF photo-injectors; Etude de photocathodes a pointe de silicium dans des canons continus et hyperfrequence

    Energy Technology Data Exchange (ETDEWEB)

    Jaber, Zakaria [Lab. de Physique Corpusculaire, Clermont-Ferrand-2 Univ., 63 - Aubiere (France)

    1999-02-02

    Nowadays the electron beams with a high intensity are particularly interesting in research and the applied physics. Producing such beams for which high intensity and low emittance are synonyms with efficiency, means developing new high luminosity electron sources, i.e. the photocathodes. This thesis, essentially experimental, is oriented in this way. After an introduction of Clermont-Ferrand and the LAL of Orsay experimental apparatus where the experiments took place, the chapter one presents the field emission and the photo-field emission. Then, we prove that the quantum efficiency of the photocathodes with silicon tips is higher for wavelengths near 800 nm. This fact is essential because it allows the use of lasers in the fundamental wavelength - Titan-Saphir for instance. In the chapter 2, we remind how the silicon tips are realized and how to improve surface conditions. Procedures and the surface analysis with the SEM and XPS are described. With a Nd-Yag laser, pumped with laser diode setting up with the participation of IRCOM Opticians of Limoges, the photocathode supplied 1 Ampere per pulse at a quantum efficiency of 0.25%. The description of this experiment and the results are the object of the chapter 3. The space charge outside the photocathode space prevents the electrons to go through. The Child-Langmuir formula limits the current with the DC gun at about 30 Ampere. To improve this result we have to use a photo-injector. In chapter 4 we prove that the silicon tip photocathode are compatible with RF gun requirements by PRIAM modeling and low level measure in a cold model of CANDELA RF gun. Technical department of CERN helped us to prepare this very sensitive experiment. (author)

  18. Advanced metal alloy systems for massive high-current photocathodes

    Science.gov (United States)

    Tkachenko, V. G.; Kondrashev, A. I.; Maksimchuk, I. N.

    2010-03-01

    The physical principles of precise alloying are formulated with the aim of increasing the low quantum efficiency (QE) of suitable simple metals (Mg, Al, Cu) as well as of decreasing their electron work function ( e φ) in the UV spectral range. The new approach provides valuable information for elucidating the origin of photoemission enhancement in bulk metal-based alloy systems. Bulk in-situ nanoclustering promises to be the most effective way of producing a much higher QE and a lower e φ in simple metals. In this article we show that the quantum efficiency of the metal-based alloys Mg-Ba, Al-Li, and Cu-BaO is considerably higher than the simple metals Mg, Al, and Cu, respectively. The spectral characteristics of the Mg-Ba, Al-Li and Cu-BaO systems obey the well-known Fowler square law for a near-free-electron model. The advanced metal alloys systems are promising photocathode materials usable for generation of high brightness electron beams.

  19. In-situ multi-information measurement system for preparing gallium nitride photocathode

    Institute of Scientific and Technical Information of China (English)

    Fu Xiao-Qian; Chang Ben-Kang; Qian Yun-Sheng; Zhang Jun-Ju

    2012-01-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode.This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status.Information including the heat cleaning temperature,vacuum degree,photocurrent,electric current of cesium source,oxygen source,and the most important information about the spectral response,or equivalently,the quantum efficiency (QE) can be obtained during preparation.The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 ℃.We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy.The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025.The spectral response of the GaN photocathode is fiat in a wavelength range from 240 nm to 365 nm,and an abrupt decline is observed at 365 nm,which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared.

  20. Experiments for improving fabrication, recovery and surface-protection of Cs3Sb photocathode

    Science.gov (United States)

    Kimoto, Takayoshi; Arai, Yoshihiro; Nagayama, Kuniak

    2017-01-01

    We examined 1) the photocurrent from Cs3Sb photocathode as a function of anode voltage below 200 V, 2) the relationship between the quantum efficiency of photoemission and the conditions for fabrication by the sandwich method, 3) recovery of the photoemission by additional Cs deposition, and 4) the effects of surface protection of Cs3Sb photocathodes by WO3 and Cr2O3 films in the passive state. The photocurrent had a maximum at approximately 68 V except when we increased the anode voltage extraordinarily slowly. Cs3Sb photocathodes were fabricated by increasing the temperature of sandwiched layers of Sb, Cs and Sb deposited on the fine tips of eight cathodes at less than -12 °C. Cs3Sb photocathodes having higher quantum efficiency were fabricated by smoothly increasing the temperature of the layers quickly after we deposited the second Sb layer. The photocurrent from the Cs3Sb photocathodes was significantly higher when Cs was deposited at temperatures of 50-70 °C. Deposition of a one- to three- atomic-layer W or Cr film extended the photoemission lifetime after the layers were oxidized to WO3 or Cr2O3 in the passive state due to oxidation. The WO3 or Cr2O3 in the passive state provided more surface protection as their thickness increased.

  1. In-situ multi-information measurement system for preparing gallium nitride photocathode

    Science.gov (United States)

    Fu, Xiao-Qian; Chang, Ben-Kang; Qian, Yun-Sheng; Zhang, Jun-Ju

    2012-03-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode. This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status. Information including the heat cleaning temperature, vacuum degree, photocurrent, electric current of cesium source, oxygen source, and the most important information about the spectral response, or equivalently, the quantum efficiency (QE) can be obtained during preparation. The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 °C. We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy. The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025. The spectral response of the GaN photocathode is flat in a wavelength range from 240 nm to 365 nm, and an abrupt decline is observed at 365 nm, which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared.

  2. The Present Development of CsI Rich Detectors for the ALICE Experiment at CERN

    CERN Document Server

    Nappi, E; Colonna, N; Di Mauro, A; Elia, D; Galantucci, L; Ghidini, B; Grimaldi, A; Goret, B; Monno, E; Paic, G; Piuz, François; Posa, F; Raynaud, J; Santiard, Jean-Claude; Tomasicchio, G; Williams, T D; Ljubicic, A; Tustonic, T; Stucchi, S

    1999-01-01

    The ALICE Collaboration plans to implement a 12m^2 array consisting of 7 proximity focussed C6F^14 liquid radiator RICH modules devoted to the particle identification in the momentum range: 1 GeV/c - 3.5 GeV/c for pions and kaons. A large area CSI-RICH prototype has been designed and built with the aim to validate the detector parameter assumptions made to predict the performance of the High Momentum Particle Identification System (HMPID) of the ALICE Experiment. The main elements of the prototype will be described with emphasis on the engineering solutions adopted. First results from the analysis of multitrack events recorded with this prototype exposed to hadron beams at the CERN SPS will be discussedList of FiguresFigure 1 General view of the ALICE lay-outFigure 2 Schematic layout of the fast CsI-RICHFigure 3 Perspective view of the HMPID layout with the seven RICH modules tilted according to their position with respect to the interaction vertex. The frame that supports the detectors is also shownFigure 4 ...

  3. First Eigenmode Transmission by High Efficient CSI Estimation for Multiuser Massive MIMO Using Millimeter Wave Bands

    Directory of Open Access Journals (Sweden)

    Kazuki Maruta

    2016-07-01

    Full Text Available Drastic improvements in transmission rate and system capacity are required towards 5th generation mobile communications (5G. One promising approach, utilizing the millimeter wave band for its rich spectrum resources, suffers area coverage shortfalls due to its large propagation loss. Fortunately, massive multiple-input multiple-output (MIMO can offset this shortfall as well as offer high order spatial multiplexing gain. Multiuser MIMO is also effective in further enhancing system capacity by multiplexing spatially de-correlated users. However, the transmission performance of multiuser MIMO is strongly degraded by channel time variation, which causes inter-user interference since null steering must be performed at the transmitter. This paper first addresses the effectiveness of multiuser massive MIMO transmission that exploits the first eigenmode for each user. In Line-of-Sight (LoS dominant channel environments, the first eigenmode is chiefly formed by the LoS component, which is highly correlated with user movement. Therefore, the first eigenmode provided by a large antenna array can improve the robustness against the channel time variation. In addition, we propose a simplified beamforming scheme based on high efficient channel state information (CSI estimation that extracts the LoS component. We also show that this approximate beamforming can achieve throughput performance comparable to that of the rigorous first eigenmode transmission. Our proposed multiuser massive MIMO scheme can open the door for practical millimeter wave communication with enhanced system capacity.

  4. First Eigenmode Transmission by High Efficient CSI Estimation for Multiuser Massive MIMO Using Millimeter Wave Bands.

    Science.gov (United States)

    Maruta, Kazuki; Iwakuni, Tatsuhiko; Ohta, Atsushi; Arai, Takuto; Shirato, Yushi; Kurosaki, Satoshi; Iizuka, Masataka

    2016-07-08

    Drastic improvements in transmission rate and system capacity are required towards 5th generation mobile communications (5G). One promising approach, utilizing the millimeter wave band for its rich spectrum resources, suffers area coverage shortfalls due to its large propagation loss. Fortunately, massive multiple-input multiple-output (MIMO) can offset this shortfall as well as offer high order spatial multiplexing gain. Multiuser MIMO is also effective in further enhancing system capacity by multiplexing spatially de-correlated users. However, the transmission performance of multiuser MIMO is strongly degraded by channel time variation, which causes inter-user interference since null steering must be performed at the transmitter. This paper first addresses the effectiveness of multiuser massive MIMO transmission that exploits the first eigenmode for each user. In Line-of-Sight (LoS) dominant channel environments, the first eigenmode is chiefly formed by the LoS component, which is highly correlated with user movement. Therefore, the first eigenmode provided by a large antenna array can improve the robustness against the channel time variation. In addition, we propose a simplified beamforming scheme based on high efficient channel state information (CSI) estimation that extracts the LoS component. We also show that this approximate beamforming can achieve throughput performance comparable to that of the rigorous first eigenmode transmission. Our proposed multiuser massive MIMO scheme can open the door for practical millimeter wave communication with enhanced system capacity.

  5. {Ni4O4} Cluster Complex to Enhance the Reductive Photocurrent Response on Silicon Nanowire Photocathodes

    Directory of Open Access Journals (Sweden)

    Yatin J. Mange

    2017-02-01

    Full Text Available Metal organic {Ni4O4} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW photocathodes. {Ni4O4} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni4O4} clusters with SiNWs gave a current density of −16 mA/cm2, which corresponds to an increase in current density of 60% when compared to bare SiNWs. The composite electrode was fully characterised and shown to be an efficient and stable photocathode for water splitting.

  6. First Beam Measurements of the S-Band photocathode Radio-Frequency Gun at Tsinghua University

    Institute of Scientific and Technical Information of China (English)

    DU Ying-Chao; YAN Li-Xin; DU Qiang; HE Xiao-Zhong; XIANG Dao; TANG Chuan-Xiang; HUANG Wen-Hui; LIN Yu-Zheng

    2007-01-01

    During the last decades, photocathode rfgun has been proven to be successful in generating the high brightness electron beam (~1nC,~1πmmmrad,~1 ps) which is required by the ILC, XFEL, Thomson scattering x-ray source,etc. A photocathode rf gun system is built to develop electron source for the Thomson scattering x-ray source at Accelerator Laboratory of Tsinghua University. The system consists of a BNL/ATF-type 1.6 cell S-band rf cavity, a solenoid for emittance compensation, a laser system and some simple equipments for beam diagnosis.The first beam measurements of the photocathode rf gun, including the dark current, transverse beam profile,charge and quantum efficiency, are reported.

  7. Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Bohler, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ding, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gilevich, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ratner, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Vetter, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-12-07

    Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Light Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.

  8. Effect of Sb thickness on the performance of bialkali-antimonide photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Mamun, Md Abdullah A., E-mail: mmamu001@odu.edu; Elmustafa, Abdelmageed A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 and The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, Carlos; Mammei, Russell; Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

    2016-03-15

    The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ∼7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layers exhibited the highest QE and the best 1/e lifetime. The authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.

  9. Tuning the colors of c-Si solar cells by exploiting plasmonic effects

    Science.gov (United States)

    Peharz, G.; Grosschädl, B.; Prietl, C.; Waldhauser, W.; Wenzl, F. P.

    2016-09-01

    The color of a crystalline silicon (c-Si) solar cell is mainly determined by its anti-reflective coating. This is a lambda/4 coating made from a transparent dielectric material. The thickness of the anti-reflective coating is optimized for maximal photocurrent generation, resulting in the typical blue or black colors of c-Si solar cells. However, for building-integrated photovoltaic (BiPV) applications the color of the solar cells is demanded to be tunable - ideally by a cheap and flexible coating process on standard (low cost) c-Si solar cells. Such a coating can be realized by applying plasmonic coloring which is a rapidly growing technology for high-quality color filtering and rendering for different fields of application (displays, imaging,…). In this contribution, we present results of an approach for tuning the color of standard industrial c-Si solar cells that is based on coating them with metallic nano-particles. In particular, thin films (green and brownish/red. The position of the resonance peak in the reflection spectrum was found to be almost independent from the angle of incidence. This low angular sensitivity is a clear advantage compared to alternative color tuning methods, for which additional dielectric thin films are deposited on c-Si solar cells.

  10. CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

    OpenAIRE

    Chuan Zhao; Xiaoping Zou; Sheng He

    2014-01-01

    Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR) method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE) value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It s...

  11. Thermal Emittance Measurement of the Cs2Te Photocathode in FZD Superconducting RF

    CERN Document Server

    Xiang, R; Michel, P; Murcek, P; Teichert, J

    2010-01-01

    The thermal emittance of the photocathode is an interesting physical property for the photoinjector, because it decides the minimum emittance the photoinjector can finally achieve. In this paper we will report the latest results of the thermal emittance of the Cs2Te photocathode in FZD Superconducting RF gun. The measurement is performed with solenoid scan method with very low bunch charge and relative large laser spot on cathode, in order to reduce the space charge effect as much as possible, and meanwhile to eliminate the wake fields and the effect from beam halos.

  12. Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

    Institute of Scientific and Technical Information of China (English)

    NIU Jun; YANG Zhi; CHANG Ben-Kang

    2009-01-01

    The mathematical expression of the electron diffusion and drift length LDE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reflection-mode uniform doping cathode, substituting L_(DE) for L_D, the equivalent quantum efficiency equation of the reflection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in fine.The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode.

  13. Photon counting performance measurements of transfer electron InGaAsP photocathode hybrid photomultiplier tubes at 1064 nm wavelength

    Science.gov (United States)

    Sun, Xiaoli; Krainak, Michael A.; Hasselbrack, William B.; La Rue, Ross A.

    2007-05-01

    We report the test results of a hybrid photomultiplier tube (HPMT) with a transfer electron (TE) InGaAsP photocathode and GaAs Schottky avalanche photodiode (APD) anode. Unlike Geiger mode InGaAsP APDs, these HPMTs (also known as intensified photodiode (IPD), vacuum APD, or hybrid photodetector) operate in linear mode without the need for quenching and gating. Their greatest advantages are wide dynamic range, high speed, large photosensitive area, and potential for photon counting and analog detection dual mode operation. The photon detection efficiency we measured was 25% at 1064 nm wavelength with a dark count rate of 60,000/s at -22 degrees Celsius. The output pulse width in response to a single photon detection is about 0.9 ns. The maximum count rate was 90 Mcts/s and was limited solely by the speed of the discriminator used in the measurement (10 ns dead time). The spectral response of these devices extended from 900 to 1300 nm. We also measured the HPMT response to 60 ps laser pulses. The average output pulse amplitude increased monotonically with the input pulse energy, which suggested that we can resolve photon number in an incident pulse. The jitter of the HPMT output was found to be about 0.5 ns standard deviation and depended on bias voltage applied to the TE photocathode. To our knowledge, these HPMTs are the most sensitive non gating photon detectors at 1064 nm wavelength, and they will have many applications in laser altimeters, atmospheric lidars, and free space laser communication systems.

  14. Perovskite BiFeO3 thin film photocathode performance with visible light activity

    Science.gov (United States)

    Yilmaz, P.; Yeo, D.; Chang, H.; Loh, L.; Dunn, S.

    2016-08-01

    Perovskite materials are now an important class of materials in the application areas of photovoltaics and photocatalysis. Inorganic perovskites such as BiFeO3 (BFO) are promising photocatalyst materials with visible light activity and inherent stability. Here we report the large area sol-gel synthesis of BFO films for solar stimulated water photo oxidation. By modifying the sol-gel synthesis process we have produced a perovskite material that has p-type behaviour and a flat band potential of ˜1.15 V (versus NHE). The photocathode produces a density of -0.004 mA cm-2 at 0 V versus NHE under AM1.5 G illumination. We further show that 0.6 μmol h-1 of O2 was produced at an external bias of -0.5 V versus Ag/AgCl. The addition of a non-percolating conducting network of Ag increases the photocurrent to -0.07 mA cm-2 at 0 V versus NHE (at 2% Ag loading) with an increase to 2.7 μmol h-1 for O2 production. We attribute the enhancement in photoelectrochemical performance to increased light absorption due light scattering by the incorporated Ag particles, improved charge transfer kinetics at the Ag/BFO interface and reduced over potential losses. We support these claims by an observed shift in flat band and onset potentials after Ag modification through UV-vis spectroscopy, Mott-Schottky plots and j-v curve analysis.

  15. Light absorption mechanism in single c-Si (core)/a-Si (shell) coaxial nanowires.

    Science.gov (United States)

    Liu, W F; Oh, J I; Shen, W Z

    2011-03-25

    We have carried out detailed investigations on the light absorption mechanism in single crystalline silicon (c-Si) (core)/amorphous Si (a-Si) (shell) coaxial nanowires (NWs). Based on the Lorenz-Mie light scattering theory, we have found that the light absorption in the coaxial NWs relies on the leaky mode resonances and that the light absorption can be optimized towards photovoltaic applications when the a-Si shell thickness is about twice the c-Si core radius. The photocurrent has been found to be enhanced up to ∼ 560% compared to c-Si NWs, and to be further enhanced up to ∼ 60% by coating the nonabsorbing dielectric shells.

  16. Organic-Inorganic Hybrid Solution-Processed H-2-Evolving Photocathodes

    NARCIS (Netherlands)

    Lai, Lai-Hung; Gomulya, Widianta; Berghuis, Matthijs; Protesescu, Loredana; Detz, Remko J.; Reek, Joost N. H.; Kovalenko, Maksym V.; Loi, Maria A.

    2015-01-01

    Here we report for the first time an H-2-evolving photocathode fabricated by a solution-processed organic inorganic hybrid composed of CdSe and P3HT. The CdSe:P3HT (10:1 (w/w)) hybrid bulk heterojunction treated with 1,2-ethanedithiol (EDT) showed efficient water reduction and hydrogen generation. A

  17. Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

    Energy Technology Data Exchange (ETDEWEB)

    Lorusso, A., E-mail: antonella.lorusso@le.infn.it [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy); Gontad, F. [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-581 83 (Sweden); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, Frascati 00044 (Italy); Perrone, A. [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy)

    2015-03-31

    Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher temperatures has been observed. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio frequency guns. - Highlights: • Pb thin films obtained by the nanosecond pulsed laser deposition technique at different substrate temperature. • The substrate temperature modifies the morphology and structure of Pb films. • Pb thin film was deposited at room temperature for photocathode application. • The Pb thin film photocathode was tested and the quantum efficiency of the device improved after laser cleaning treatment of the film surface.

  18. Engineering MoSx/Ti/InP Hybrid Photocathode for Improved Solar Hydrogen Production

    Science.gov (United States)

    Li, Qiang; Zheng, Maojun; Zhong, Miao; Ma, Liguo; Wang, Faze; Ma, Li; Shen, Wenzhong

    2016-07-01

    Due to its direct band gap of ~1.35 eV, appropriate energy band-edge positions, and low surface-recombination velocity, p-type InP has attracted considerable attention as a promising photocathode material for solar hydrogen generation. However, challenges remain with p-type InP for achieving high and stable photoelectrochemical (PEC) performances. Here, we demonstrate that surface modifications of InP photocathodes with Ti thin layers and amorphous MoSx nanoparticles can remarkably improve their PEC performances. A high photocurrent density with an improved PEC onset potential is obtained. Electrochemical impedance analyses reveal that the largely improved PEC performance of MoSx/Ti/InP is attributed to the reduced charge-transfer resistance and the increased band bending at the MoSx/Ti/InP/electrolyte interface. In addition, the MoSx/Ti/InP photocathodes function stably for PEC water reduction under continuous light illumination over 2 h. Our study demonstrates an effective approach to develop high-PEC-performance InP photocathodes towards stable solar hydrogen production.

  19. Heat load of a GaAs photocathode in an SRF electron gun

    Institute of Scientific and Technical Information of China (English)

    王尔东; 赵夔; JSrg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; 吴琼; Animesh Jain; Ramesh Gupta; Doug Holmes

    2011-01-01

    A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. Howe

  20. Pressure dependence of structural phase transition and superconducting transition in CsI

    CERN Document Server

    Nirmala-Louis, C

    2003-01-01

    The self-consistent band structure calculation for CsI performed both in CsCl and HCP structures using the TB-LMTO method is reported. The equilibrium lattice constant, bulk modulus and the phase-transition pressure at which the compound undergoes structural phase transition from CsCl to HCP are predicted from the total-energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (T sub c) of CsI are obtained as a function of pressure for both the CsCl and HCP structures. It is found that the charge transfer from s and p states to d state causes metallization and superconductivity in CsI. The highest T sub c estimated is 2.11 K and the corresponding pressure is 1.8 Mbar. This value is in agreement with the recent experimental observation. The experimental trend - ''metallization and superconductivity is rather insensitive to the crystal structure of CsI'' - is also confirmed in our work. (Abstract Copyright [2003], ...

  1. CSI Web Adventures: A Forensics Virtual Apprenticeship for Teaching Science and Inspiring STEM Careers

    Science.gov (United States)

    Miller, Leslie; Chang, Ching-I; Hoyt, Daniel

    2010-01-01

    CSI: The Experience, a traveling museum exhibit and a companion web adventure, was created through a grant from the National Science Foundation as a potential model for informal learning. The website was designed to enrich and complement the exhibit by modeling the forensic process. Substantive science, real-world lab techniques, and higher-level…

  2. CSI-EPT in Presence of RF-Shield for MR-Coils.

    Science.gov (United States)

    Arduino, Alessandro; Zilberti, Luca; Chiampi, Mario; Bottauscio, Oriano

    2017-02-08

    CSI-EPT is a recently developed technique for the electric properties tomography, that recovers the electric properties distribution starting from measurements performed by magnetic resonance imaging scanners. This method is an optimal control approach based on the contrast source inversion technique, which distinguishes itself from other electric properties tomography techniques for its capability to recover also the local specific absorption rate distribution, essential for online dosimetry. Up to now, CSI-EPT has only been described in terms of integral equations, limiting its applicability to homogeneous unbounded background. In order to extend the method to the presence of a shield in the domain-as in the recurring case of shielded radiofrequency coils-a more general formulation of CSI-EPT, based on a functional viewpoint, is introduced here. Two different implementations of CSI-EPT are proposed for a two-dimensional transverse magnetic model problem, one dealing with an unbounded domain and one taking into account the presence of a perfectly conductive shield. The two implementations are applied on the same virtual measurements obtained by numerically simulating a shielded radiofrequency coil. The results are compared in terms of both electric properties recovery and local specific absorption rate estimate, in order to investigate the requirement of an accurate modelling of the underlying physical problem.

  3. Distributed cognitive two-way relay beamformer designs under perfect and imperfect CSI

    KAUST Repository

    Pandarakkottilil, Ubaidulla

    2011-09-01

    In this paper, we present distributed two-way relay beamformer designs for a cognitive radio network (CRN) in which a pair of cognitive (or secondary) transceiver nodes communicate with each other assisted by a set of cognitive two-way relay nodes. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. First, we consider relay beamformer designs assuming the availability of perfect channel state information (CSI). For this case, a mean-square error (MSE)-constrained beamformer that minimizes the total relay transmit power, and an MSE-balancing beamformer with a constraint on the total relay transmit power are proposed. Next, we consider relay beamformer designs assuming that the available CSI is imperfect. For this case too, we consider the same problems as those in the case of perfect CSI, and propose beamformer designs that are robust to the errors in the CSI. We show that the proposed designs can be reformulated as convex optimization problems that can be solved efficiently. Through numerical simulations, we illustrate the performance of the proposed designs. © 2011 IEEE.

  4. Achievable Rates of Cognitive Radio Networks Using Multi-Layer Coding with Limited CSI

    KAUST Repository

    Sboui, Lokman

    2016-03-01

    In a Cognitive Radio (CR) framework, the channel state information (CSI) feedback to the secondary transmitter (SU Tx) can be limited or unavailable. Thus, the statistical model is adopted in order to determine the system performance using the outage concept. In this paper, we adopt a new approach using multi-layer-coding (MLC) strategy, i.e., broadcast approach, to enhance spectrum sharing over fading channels. First, we consider a scenario where the secondary transmitter has no CSI of both the link between SU Tx and the primary receiver (cross-link) and its own link. We show that using MLC improves the cognitive rate compared to the rate provided by a singlelayer- coding (SLC). In addition, we observe numerically that 2-Layer coding achieves most of the gain for Rayleigh fading. Second, we analyze a scenario where SU Tx is provided by partial CSI about its link through quantized CSI. We compute its achievable rate adopting the MLC and highlight the improvement over SLC. Finally, we study the case in which the cross-link is perfect, i.e., a cooperative primary user setting, and compare the performance with the previous cases. We present asymptotic analysis at high power regime and show that the cooperation enhances considerably the cognitive rate at high values of the secondary power budget.

  5. QE and Suns-Voc study on the epitaxial CSiTF solar cells

    Institute of Scientific and Technical Information of China (English)

    AI Bin; SHEN Hui; BAN Qun; LIANG Zongcun; CHEN Rulong; SHI Zhengrong; LIAO Xianbo

    2005-01-01

    In order to clarify the major factors having confined the efficiencies of as-prepared crystalline silicon thin film (CSiTF) solar cells on the SSP (silicon sheets from powder) ribbons, QE (quantum efficiency) and Suns-Voc study were performed on the epitaxial CSiTF solar cells fabricated on the SSP ribbons, the SSP ribbons after surface being zone melting recrystallized (ZMR) and single crystalline silicon (sc-Si) substrates.The results show that the epi-layers deposited on the SSP ribbons have rough surfaces,which not only increases the diffusion reflectance on the surfaces but also makes the anti-reflection coatings become structure-loosened, both of which would deteriorate the light trapping effect; in addition, the epi-layers deposited on the SSP ribbons possess poor crystallographic quality, so the heavy grain boundary (GB) recombination limits the diffusion length of the minority carriers in the epi-layers, which makes the as-prepared CSiTF solar cells suffer the worse spectra response at long-wavelength range. Nearly all the dark characteristic parameters of the CSiTF solar cells are far away from the ideal values. The performances of the CSiTF solar cells are especially affected by too high I02 (the dark saturation current of space charge region) values and too low Rsh (parallel resistance) values. The higher I02 values are mainly caused by the heavy GB recombination resulting from the poor crystallographic qualities of the silicon active layers in the space charge regions, while the lower Rsh values are attributed to the electrical leakage at the un-passivated PN junction or solar cell edges after the solar cells are cut by the laser scriber.

  6. Nanomechanical and electrical properties of Nb thin films deposited on Pb substrates by pulsed laser deposition as a new concept photocathode for superconductor cavities

    Science.gov (United States)

    Gontad, F.; Lorusso, A.; Panareo, M.; Monteduro, A. G.; Maruccio, G.; Broitman, E.; Perrone, A.

    2015-12-01

    We report a design of photocathode, which combines the good photoemissive properties of lead (Pb) and the advantages of superconducting performance of niobium (Nb) when installed into a superconducting radio-frequency gun. The new configuration is obtained by a coating of Nb thin film grown on a disk of Pb via pulsed laser deposition. The central emitting area of Pb is masked by a shield to avoid the Nb deposition. The nanomechanical properties of the Nb film, obtained through nanoindentation measurements, reveal a hardness of 2.8±0.3 GPa, while the study of the electrical resistivity of the film shows the appearance of the superconducting transitions at 9.3 K and 7.3 K for Nb and Pb, respectively, very close to the bulk material values. Additionally, morphological, structural and contamination studies of Nb thin film expose a very low droplet density on the substrate surface, a small polycrystalline orientation of the films and a low contamination level. These results, together with the acceptable Pb quantum efficiency of 2×10-5 found at 266 nm, demonstrate the potentiality of the new concept photocathode.

  7. Cloning and Expression Analysis of Tea Hydroperoxide Lyase Gene CsiHPL1%茶树脂氢过氧化物裂解酶基因CsiHPL1的克隆及表达

    Institute of Scientific and Technical Information of China (English)

    辛肇军; 孙晓玲; 张正群; 陈宗懋

    2013-01-01

    根据茶树基因CsiHPL1的cDNA序列设计引物,采用RT-PCR方法从茶树品种龙井43,中克隆了CsiHPL1 序列,并分析了CsiHPL1在生物和非生物胁迫下的诱导表达情况及亚细胞定位.结果表明,CsiHPL1包含一个1476 bp的最大开放阅读框,编码491个氨基酸,预测为13-HPL基因.Real-Time PCR分析结果表明,CsiHPL1的表达受到茶尺蠖取食、机械损伤和茉莉酸的诱导;构建了CsiHPL1与绿色荧光蛋白(GFP)基因的重组表达载体,经农杆菌瞬时转化烟草叶片,利用激光共聚焦显微镜在叶绿体中观察到GFP荧光,表明CsiHPL1编码的蛋白质为叶绿体蛋白质.%Primers were designed according to the cDNA sequence of tea CsiHPLl. RT-PCR method was used to clone CsiHPLl from Longjing 43'. The expression of CsiHPLl under biotic and abiotic stress and subcellular localization were analyzed. The results showed CsiHPLl contains an open reading frame of 1 476 bp which encodes a protein of 491 amino acids. This gene was predicted as a 13-HPL gene. Tea geometrid feeding, wounding and JA treatment up-regulated the expression levels of CsiHPLl. The total sequence of this gene was fused with GFP to construct a binary vector for tobacco transient transformation. Under confocal laser-scanning microscopy, green fluorescent signals were localized in chloroplasts in transgenic tobacco plants, suggesting that the gene encodes a protein targeting to chloroplast.

  8. Metastability of a-SiOx:H thin films for c-Si surface passivation

    Science.gov (United States)

    Serenelli, L.; Martini, L.; Imbimbo, L.; Asquini, R.; Menchini, F.; Izzi, M.; Tucci, M.

    2017-01-01

    The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Sisbnd H and Sisbnd O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300 °C for 30 min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution

  9. CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

    Directory of Open Access Journals (Sweden)

    Chuan Zhao

    2014-01-01

    Full Text Available Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

  10. Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique

    Science.gov (United States)

    Lorusso, A.; Gontad, F.; Solombrino, L.; Chiadroni, E.; Broitman, E.; Perrone, A.

    2016-11-01

    In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y.

  11. High-voltage testing of a 500-kV dc photocathode electron gun

    Science.gov (United States)

    Nagai, Ryoji; Hajima, Ryoichi; Nishimori, Nobuyuki; Muto, Toshiya; Yamamoto, Masahiro; Honda, Yosuke; Miyajima, Tsukasa; Iijima, Hokuto; Kuriki, Masao; Kuwahara, Makoto; Okumi, Shoji; Nakanishi, Tsutomu

    2010-03-01

    A high-voltage dc photocathode electron gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 h was demonstrated at an acceleration voltage of 500 kV. The dc photocathode electron gun is designed for future light sources based on energy-recovery linac and consists of a Cockcroft-Walton generator, a segmented cylindrical ceramic insulator, guard-ring electrodes, a support-rod electrode, a vacuum chamber, and a pressurized insulating gas tank. The segmented cylindrical ceramic insulator and the guard-ring electrodes were utilized to prevent any damage to the insulator from electrons emitted by the support-rod electrode.

  12. JAERI 200 kV Electron Gun with an NEA-GaAs Photocathode

    CERN Document Server

    Nishitani, Tomohiro; Kikuzawa, Nobuhiro; John Minehara, Eisuke; Nagai, Ryoji; Nishimori, Nobuyuki; Sawamura, Masaru; Yamauchi, T

    2004-01-01

    The GaAs photocathode with negative electron affinity surface (NEA-GaAs) has been expected to be low emittance (<0.5 πmm・mrad) electron beam source. In order to generate low emittance electron beam required from ERL-FEL, we have started the developmental program of a 200keV electron gun with the NEA-GaAs photocathode for the first time in JAERI. An NEA surface has the problem that lifetime is limited by gun vacuum condition and by ion back bombardment between anode- and cathode-electrode. In order to long an NEA surface lifetime, the JAERI 200keV electron gun system consists of a 200kV DC-gun chamber on extreme high vacuum condition and an NEA activation chamber with load-lock system.

  13. Structural and morphological properties of metallic thin films grown by pulsed laser deposition for photocathode application

    Science.gov (United States)

    Lorusso, A.; Gontad, F.; Caricato, A. P.; Chiadroni, E.; Broitman, E.; Perrone, A.

    2016-03-01

    In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density, while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed.

  14. In situ Observation of Dark Current Emission in a High Gradient RF Photocathode Gun

    CERN Document Server

    Shao, Jiahang; Baryshev, Sergey V; Chen, Huaibi; Conde, Manoel; Gai, Wei; Ha, Gwanghui; Jing, Chunguang; Shi, Jiaru; Wang, Faya; Wisniewski, Eric

    2016-01-01

    Undesirable electron field emission (a.k.a. dark current) in high gradient RF photocathode guns deteriorates the quality of photoemission current and limits the operational gradient. To improve the understanding of dark current emission, a high-resolution (~100 um) dark current imaging experiment has been performed in an L-band photocathode gun operating at ~100 MV/m of surface gradient. Dark current from the cathode has been observed to be dominated by several separated strong emitters. The field enhancement factor, beta, of selected regions on the cathode has been measured. The post scanning electron microscopy (SEM) and white light interferometer (WLI) surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred.

  15. Planar field emitters and high efficiency photocathodes based on ultrananocrystalline diamond

    Energy Technology Data Exchange (ETDEWEB)

    Sumant, Anirudha V.; Baryshev, Sergey V.; Antipov, Sergey P.

    2016-08-16

    A method of forming a field emitter comprises disposing a first layer on a substrate. The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10.sup.12 to about 10.sup.14 emitting sites per cm.sup.2. A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

  16. Effect of humid air exposure on photoemissive and structural properties of KBr thin film photocathode

    CERN Document Server

    Rai, R; Ghosh, N; Singh, B K

    2014-01-01

    We have investigated the influence of water molecule absorption on photoemissive and structural properties of potassium bromide (KBr) thin film photocathode under humid air exposure at relative humidity (RH) 65%. It is evident from photoemission measurement that the photoelectron yield of KBr photocathode is degraded exponentially with humid air exposed time. Structural studies of the "as-deposited" and "humid air aged" films reveal that there is no effect of RH on film's crystalline face centered cubic (fcc) structure. However, the average crystallite size of "humid air exposed film" KBr film has been increased as compared to "as-deposited". In addition, topographical properties of KBr film are also examined by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) and it is observed that granular characteristic of film has been altered, even for short exposure to humid air.

  17. Activation processes on GaAs photocathode by different currents of oxygen source

    Science.gov (United States)

    Miao, Zhuang; Shi, Feng; Cheng, Hongchang; Wang, Shufei; Zhang, Xiaohui; Yuan, Yuan; Chen, Chang

    2015-04-01

    In order to know the influence of activation processes on GaAs photocathodes, three GaAs samples were activated by a fixed current of cesium source and different currents of oxygen source. The current of caesium source is same during activation to ensure initial adsorption of caesium quantum is similar, which is the base to show the difference during alternation activation of caesium and oxygen. Analysed with the activation data, it is indicated that Cs-to-O current ratio of 1.07 is the optimum ratio to obtain higher sensitivity and better stability. According to double dipole model, stable and uniform double dipole layers of GaAs-O-Cs:Cs-O-Cs are formed and negative electron affinity is achieved on GaAs surface by activation with cesium and oxygen. The analytical result is just coincident with the model. Thus there is an efficient technological method to improve sensitivity and stability of GaAs photocathode.

  18. Characterization and control of the electronic properties of a NiO based dye sensitized photocathode.

    Science.gov (United States)

    Hod, Idan; Tachan, Zion; Shalom, Menny; Zaban, Arie

    2013-05-07

    One compartment tandem DSSCs are based on two photoactive electrodes which are mediated by a redox electrolyte. Electron accumulation in the photoanode (n-type DSSC) alongside hole accumulation in the photocathode (p-type DSSC) should generate high photovoltage using different parts of the solar spectrum. While impressive efficiencies are reported for n-type DSSCs, the performance of the p-type analogue is very low due to insufficient understanding and a lack of materials. Electrochemical impedance spectroscopy of the p-type DSSC reveals that hole transport within the NiO mesoporous photocathode is the performance limiting factor. Modification of the NiO electrode with molecular dipoles significantly increases the cell photovoltage but has no significant effect on the photocurrent of the p-DSSC. Consequently, the development of better hole conducting materials in conjunction with surface dipole modification can lead to high photovoltage, high photocurrent p-DSSCs and thus to efficient tandem DSSCs.

  19. Planar Field Emitters and High Efficiency Photocathodes Based on Ultrananocrystalline Diamond

    Science.gov (United States)

    Sumant, Anirudha V. (Inventor); Baryshev, Sergey V. (Inventor); Antipov, Sergey P. (Inventor)

    2016-01-01

    A method of forming a field emitter comprises disposing a first layer on a substrate. The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10.sup.12 to about 10.sup.14 emitting sites per cm.sup.2. A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

  20. Mo3S4 Clusters as an Effective H2 Evolution Catalyst on Protected Si Photocathodes

    DEFF Research Database (Denmark)

    Seger, Brian; Herbst, Konrad; Pedersen, Thomas

    2014-01-01

    This work shows how a molecular Mo3S4 cluster bonded to a photoelectrode surface via a phosphonate ligand can be a highly effective co-catalyst in photocathodic hydrogen evolution systems. Using a TiO2 protected n+p Si photocathode, H2 evolution occurs with an onset of +0.33 V vs. RHE in an acid...... solution with this precious metal-free system. Using just the red part of the AM1.5 solar spectrum (λ > 635 nm), a saturation current of 20 mA/cm2 is achieved from an electrode containing Mo3S4 dropcasted onto a 100 nm TiO2/7 nm Ti/n+p Si electrode....

  1. Multislit-Based Emittance Measurement of Electron Beam from a Photocathode Radio-Frequency Gun

    Institute of Scientific and Technical Information of China (English)

    YAN Li-Xin; DU Ying-Chao; XIANG Dao; LI Ren-Kai; QIAN Hou-Jun; HUANG Wen-Hui; TANG Chuan-Xiang; LIN Yu-Zheng; CHENG Jian-Ping

    2008-01-01

    Measurement of emittance for a space-charge dominated electron beam from a photocathode rf gun is performed by employing the multislit-based method at Accelerator Laboratory of Tsinghua University.We present the design considerations on the multislit system and the experimental results,with special attention to the study of space charge induced emittance growth.The experimental results are in reasonable agreement with the PARMELA simulations.

  2. Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

    OpenAIRE

    Lorusso, Antonella; Gontad, F.; Broitman, Esteban; Chiadroni, E.; Perrone, Walter

    2015-01-01

    Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher ...

  3. Generation and measurement of sub-picosecond electron bunch in photocathode rf gun

    OpenAIRE

    Li, Weiwei; He, Zhiagng; Jia, Qika

    2013-01-01

    We consider a scheme to generate sub-picosecond electron bunch in the photocathode rf gun by improving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunc...

  4. State-of-the-art Pb photocathodes deposited by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gontad, F., E-mail: Francisco.gontad@le.infn.it; Perrone, A.

    2014-05-21

    In this article we present and discuss the current status of thin film Pb photocathodes deposited by pulsed laser deposition (PLD) with different laser parameters, such as laser fluence, wavelength or pulse duration. The PLD technique appears very efficient for the fabrication of pure Pb photocathodes, providing good adherence and respectable quantum efficiency. The films deposited on the picosecond and subpicosecond regimes are practically free of big droplets and fragments, whereas in the nanosecond regime their presence cannot be neglected. All the films present a granular structure and polycrystalline character with preferential orientation along the (111) crystalline planes, irrespective of the laser pulse duration or wavelength. The main results obtained from the photoemission performance of Pb thin films deposited by PLD demonstrate their chemical stability under vacuum conditions and respectable quantum efficiency with a maximum of 7.3×10{sup −5} for films deposited on the subpicosecond regime. The photoemission properties confirm that Pb thin films deposited by PLD are a notable alternative for the fabrication of photocathodes for superconductive radio-frequency electron guns. - Highlights: • Lead samples were grown by Pulsed Laser Deposition at different laser parameters • All films present a granular morphology • Lead films grow preferentially along the 111 crystalline planes of the cubic net • A maximum quantum efficiency of 7.3 × 10-5 has been found.

  5. Heat load of a GaAs photocathode in an SRF electron gun

    Institute of Scientific and Technical Information of China (English)

    WANG Er-Dong; ZHAO Kui; J(o)rg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; WU Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

    2011-01-01

    A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs.

  6. Bi-alkali antimonide photocathode growth: An X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Susanne; Wong, Jared; Feng, Jun; Karkare, Siddharth; Padmore, Howard; Ruiz-Osés, Miguel; Smedley, John; Muller, Erik; Ding, Zihao; Gaowei, Mengjia; Attenkofer, Klaus; Liang, Xue; Xie, Junqi; Kühn, Julius

    2016-07-21

    Bi-alkali antimonide photocathodes are one of the best known sources of electrons for high current and/or high bunch charge applications like Energy Recovery Linacs or Free Electron Lasers. Despite their high quantum efficiency in visible light and low intrinsic emittance, the surface roughness of these photocathodes prohibits their use as low emittance cathodes in high accelerating gradient superconducting and normal conducting radio frequency photoguns and limits the minimum possible intrinsic emittance near the threshold. Also, the growth process for these materials is largely based on recipes obtained by trial and error and is very unreliable. In this paper, using X-ray diffraction, we investigate the different structural and chemical changes that take place during the growth process of the bi-alkali antimonide material K2CsSb. Our measurements give us a deeper understanding of the growth process of alkali-antimonide photocathodes allowing us to optimize it with the goal of minimizing the surface roughness to preserve the intrinsic emittance at high electric fields and increasing its reproducibility.

  7. Bi-alkali antimonide photocathode growth: An X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Susanne; Wong, Jared; Feng, Jun; Karkare, Siddharth; Padmore, Howard; Ruiz-Osés, Miguel; Smedley, John; Muller, Erik; Ding, Zihao; Gaowei, Mengjia; Attenkofer, Klaus; Liang, Xue; Xie, Junqi; Kühn, Julius

    2016-07-21

    Bi-alkali antimonide photocathodes are one of the best known sources of electrons for high current and/or high bunch charge applications like Energy Recovery Linacs or Free Electron Lasers. Despite their high quantum efficiency in visible light and low intrinsic emittance, the surface roughness of these photocathodes prohibits their use as low emittance cathodes in high accelerating gradient superconducting and normal conducting radio frequency photoguns and limits the minimum possible intrinsic emittance near the threshold. Also, the growth process for these materials is largely based on recipes obtained by trial and error and is very unreliable. In this paper, using X-ray diffraction, we investigate the different structural and chemical changes that take place during the growth process of the bi-alkali antimonide material K2CsSb. Our measurements give us a deeper understanding of the growth process of alkali-antimonide photocathodes allowing us to optimize it with the goal of minimizing the surface roughness to preserve the intrinsic emittance at high electric fields and increasing its reproducibility.

  8. Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, Claude

    2009-10-28

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

  9. Light yield of an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin

    CERN Document Server

    Liu, Jing; Soma, Arun Kumar

    2016-01-01

    A light yield of 20.4 $\\pm$ 0.8 photoelectrons/keV was achieved with an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin. This is by far the largest yield in the world achieved with CsI crystals. An energy threshold that is several times lower than the current dark matter experiments utilizing CsI(Tl) crystals may be achievable using this technique. Together with novel CsI crystal purification methods, the technique may be used to improve the sensitivities of dark matter and coherent elastic neutrino-nucleus scattering experiments. Also measured were the scintillation light decay constants of the undoped CsI crystal at both room temperature and 77 Kelvin. The results are consistent with those in the literature.

  10. Outage Performance of Decode-and-Forward in Two-Way Relaying with Outdated CSI

    KAUST Repository

    Hyadi, Amal

    2015-01-07

    In this paper, we analyze the outage behavior of decode-and-forward relaying in the context of selective two-way cooperative systems. First, a new relay selection metric is proposed to take into consideration both transmission rates and instantaneous link conditions between cooperating nodes. Afterwards, the outage probability of the proposed system is derived for Nakagami-m fading channels in the case when perfect channel state information is available and then extended to the more realistic scenario where the available channel state information (CSI) is outdated due to fast fading. New expressions for the outage probability are obtained, and the impact of imperfect CSI on the performance is evaluated. Illustrative numerical results, Monte Carlo simulations, and comparisons with similar approaches are presented to assess the accuracy of our analytical derivations and confirm the performance gain of the proposed scheme.

  11. Coverage probability of cellular networks using interference alignment under imperfect CSI

    Directory of Open Access Journals (Sweden)

    Raoul F. Guiazon

    2016-11-01

    Full Text Available Interference alignment (IA is well understood to approach the capacity of interference channels, and believed to be crucial in cellular networks in which the ability to control and exploit interference is key. However, the achievable performance of IA in cellular networks depends on the quality of channel state information (CSI and how effective IA is in practical settings is not known. This paper studies the use of IA to mitigate inter-cell interference of cellular networks under imperfect CSI conditions. Our analysis is based on stochastic geometry where the structure of the base station (BS locations is considered by a Poisson point process (PPP. Our main contribution is the coverage probability of the network and simulation results confirm the accuracy.

  12. Modified Grid-Connected CSI for Hybrid PV/Wind Power Generation System

    Directory of Open Access Journals (Sweden)

    D. Amorndechaphon

    2012-01-01

    Full Text Available The principle of a power conditioning unit for hybrid PV/wind power generation system is proposed. The proposed power conditioner is based on the current source inverter (CSI topology. All energy sources are connected in parallel with a DC-bus through the modified wave-shaping circuits. To achieve the unity power factor at the utility grid, the DC-link current can be controlled via the wave-shaping circuits with the sinusoidal PWM scheme. In this work, the carrier-based PWM scheme is also proposed to minimize the utility current THD. The power rating of the proposed system can be increased by connecting more PV/wind modules through their wave-shaping circuits in parallel with the other modules. The details of the operating principles, the system configurations, and the design considerations are described. The effectiveness of the proposed CSI is demonstrated by simulation results.

  13. Behind the Nature of Titanium Oxide Excellent Surface Passivation and Carrier Selectivity of c-Si

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Crovetto, Andrea; Hansen, Ole

    We present an expanded study of the passivation properties of titanium dioxide (TiO2) on p-type crystalline silicon (c-Si). We report a low surface recombination velocity (16 cm/s) for TiO2 passivation layers with a thin tunnelling oxide interlayer (SiO2 or Al2O3) on p-type crystalline silicon (c......-Si). The TiO2 films were deposited by thermal atomic layer deposition (ALD) at temperatures in the range of 80-300  ̊C using titanium tetrachloride (TiCl4) as Ti precursor and water as the oxidant. The influence of TiO2 thickness (5, 10, 20 nm), presence of additional tunneling interlayer (SiO2 or Al2O3...

  14. Televisual forensics on the edge of chaos: post-genomic complexity in CSI: Crime Scene Investigation

    OpenAIRE

    Bull, Sofia

    2015-01-01

    This essay examines the discourse on scientific knowledge in the forensic crime drama CSI: Crime Scene Investigation (CBS, 2000–), in ways that complicate the common assumption that its science only offers conservatively straightforward answers and simple solutions. Through close textual readings, and comparative historic genre analysis of The Expert (BBC, 1968–76), Quincy M.E. (NBC, 1976–83) and Silent Witness (BBC, 1996), the essay maps the residual, dominant and emergent scientific discour...

  15. FaCSI: A block parallel preconditioner for fluid-structure interaction in hemodynamics

    Science.gov (United States)

    Deparis, Simone; Forti, Davide; Grandperrin, Gwenol; Quarteroni, Alfio

    2016-12-01

    Modeling Fluid-Structure Interaction (FSI) in the vascular system is mandatory to reliably compute mechanical indicators in vessels undergoing large deformations. In order to cope with the computational complexity of the coupled 3D FSI problem after discretizations in space and time, a parallel solution is often mandatory. In this paper we propose a new block parallel preconditioner for the coupled linearized FSI system obtained after space and time discretization. We name it FaCSI to indicate that it exploits the Factorized form of the linearized FSI matrix, the use of static Condensation to formally eliminate the interface degrees of freedom of the fluid equations, and the use of a SIMPLE preconditioner for saddle-point problems. FaCSI is built upon a block Gauss-Seidel factorization of the FSI Jacobian matrix and it uses ad-hoc preconditioners for each physical component of the coupled problem, namely the fluid, the structure and the geometry. In the fluid subproblem, after operating static condensation of the interface fluid variables, we use a SIMPLE preconditioner on the reduced fluid matrix. Moreover, to efficiently deal with a large number of processes, FaCSI exploits efficient single field preconditioners, e.g., based on domain decomposition or the multigrid method. We measure the parallel performances of FaCSI on a benchmark cylindrical geometry and on a problem of physiological interest, namely the blood flow through a patient-specific femoropopliteal bypass. We analyze the dependence of the number of linear solver iterations on the cores count (scalability of the preconditioner) and on the mesh size (optimality).

  16. 49th Annual Convention of the Computer Society of India CSI

    CERN Document Server

    Govardhan, A; Raju, K; Mandal, J

    2015-01-01

    Volume 1 contains 73 papers presented at CSI 2014: Emerging ICT for Bridging the Future: Proceedings of the 49th Annual Convention of Computer Society of India. The convention was held during 12-14, December, 2014 at Hyderabad, Telangana, India. This volume contains papers mainly focused on Fuzzy Systems, Image Processing, Software Engineering, Cyber Security and Digital Forensic, E-Commerce, Big Data, Cloud Computing and ICT applications.

  17. Detection of Potential Induced Degradation in c-Si PV Panels Using Electrical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso

    This work, for the first time, investigates an Impedance Spectroscopy (IS) based method for detecting potential-induced degradation (PID) in crystalline silicon photovoltaic (c-Si PV) panels. The method has been experimentally tested on a set of panels that were confirmed to be affected by PID...... by using traditional current-voltage (I-V) characterization methods, as well as electroluminescence (EL) imaging. The results confirm the effectiveness of the new approach to detect PID in PV panels....

  18. Benefit of Delay on the Diversity-Multiplexing Tradeoffs of MIMO Channels with Partial CSI

    CERN Document Server

    Sharif, Masoud

    2007-01-01

    This paper re-examines the well-known fundamental tradeoffs between rate and reliability for the multi-antenna, block Rayleigh fading channel in the high signal to noise ratio (SNR) regime when (i) the transmitter has access to (noiseless) one bit per coherence-interval of causal channel state information (CSI) and (ii) soft decoding delays together with worst-case delay guarantees are acceptable. A key finding of this work is that substantial improvements in reliability can be realized with a very short expected delay and a slightly longer (but bounded) worst-case decoding delay guarantee in communication systems where the transmitter has access to even one bit per coherence interval of causal CSI. While similar in spirit to the recent work on communication systems based on automatic repeat requests (ARQ) where decoding failure is known at the transmitter and leads to re-transmission, here transmit side-information is purely based on CSI. The findings reported here also lend further support to an emerging un...

  19. Excellent c-Si surface passivation by low-temperature atomic layer deposited titanium oxide

    Science.gov (United States)

    Liao, Baochen; Hoex, Bram; Aberle, Armin G.; Chi, Dongzhi; Bhatia, Charanjit S.

    2014-06-01

    In this work, we demonstrate that thermal atomic layer deposited (ALD) titanium oxide (TiOx) films are able to provide a—up to now unprecedented—level of surface passivation on undiffused low-resistivity crystalline silicon (c-Si). The surface passivation provided by the ALD TiOx films is activated by a post-deposition anneal and subsequent light soaking treatment. Ultralow effective surface recombination velocities down to 2.8 cm/s and 8.3 cm/s, respectively, are achieved on n-type and p-type float-zone c-Si wafers. Detailed analysis confirms that the TiOx films are nearly stoichiometric, have no significant level of contaminants, and are of amorphous nature. The passivation is found to be stable after storage in the dark for eight months. These results demonstrate that TiOx films are also capable of providing excellent passivation of undiffused c-Si surfaces on a comparable level to thermal silicon oxide, silicon nitride, and aluminum oxide. In addition, it is well known that TiOx has an optimal refractive index of 2.4 in the visible range for glass encapsulated solar cells, as well as a low extinction coefficient. Thus, the results presented in this work could facilitate the re-emergence of TiOx in the field of high-efficiency silicon wafer solar cells.

  20. Minimax robust power split in AF relays based on uncertain long-term CSI

    KAUST Repository

    Nisar, Muhammad Danish

    2011-09-01

    An optimal power control among source and relay nodes in presence of channel state information (CSI) is vital for an efficient amplify and forward (AF) based cooperative communication system. In this work, we study the optimal power split (power control) between the source and relay node in presence of an uncertainty in the CSI. The prime contribution is to solve the problem based on an uncertain long-term knowledge of both the first and second hop CSI (requiring less frequent updates), and under an aggregate network-level power constraint. We employ the minimax optimization methodology to arrive at the minimax robust optimal power split, that offers the best possible guarantee on the end-to-end signal to noise ratio (SNR). The derived closed form analytical expressions admit simple intuitive interpretations and are easy to implement in real-world AF relaying systems. Numerical results confirm the advantages of incorporating the presence of uncertainty into the optimization problem, and demonstrate the usefulness of the proposed minimax robust optimal power split. © 2011 IEEE.

  1. Towards efficient solar-to-hydrogen conversion: Fundamentals and recent progress in copper-based chalcogenide photocathodes

    Science.gov (United States)

    Chen, Yubin; Feng, Xiaoyang; Liu, Maochang; Su, Jinzhan; Shen, Shaohua

    2016-09-01

    Photoelectrochemical (PEC) water splitting for hydrogen generation has been considered as a promising route to convert and store solar energy into chemical fuels. In terms of its large-scale application, seeking semiconductor photoelectrodes with high efficiency and good stability should be essential. Although an enormous number of materials have been explored for solar water splitting in the last several decades, challenges still remain for the practical application. P-type copper-based chalcogenides, such as Cu(In, Ga)Se2 and Cu2ZnSnS4, have shown impressive performance in photovoltaics due to narrow bandgaps, high absorption coefficients, and good carrier transport properties. The obtained high efficiencies in photovoltaics have promoted the utilization of these materials into the field of PEC water splitting. A comprehensive review on copper-based chalcogenides for solar-to-hydrogen conversion would help advance the research in this expanding area. This review will cover the physicochemical properties of copper-based chalco-genides, developments of various photocathodes, strategies to enhance the PEC activity and stability, introductions of tandem PEC cells, and finally, prospects on their potential for the practical solar-to-hydrogen conversion. We believe this review article can provide some insights of fundamentals and applications of copper-based chalco-genide thin films for PEC water splitting.

  2. Towards efficient solar-to-hydrogen conversion: Fundamentals and recent progress in copper-based chalcogenide photocathodes

    Directory of Open Access Journals (Sweden)

    Chen Yubin

    2016-09-01

    Full Text Available Photoelectrochemical (PEC water splitting for hydrogen generation has been considered as a promising route to convert and store solar energy into chemical fuels. In terms of its large-scale application, seeking semiconductor photoelectrodes with high efficiency and good stability should be essential. Although an enormous number of materials have been explored for solar water splitting in the last several decades, challenges still remain for the practical application. P-type copper-based chalcogenides, such as Cu(In, GaSe2 and Cu2ZnSnS4, have shown impressive performance in photovoltaics due to narrow bandgaps, high absorption coefficients, and good carrier transport properties. The obtained high efficiencies in photovoltaics have promoted the utilization of these materials into the field of PEC water splitting. A comprehensive review on copper-based chalcogenides for solar-to-hydrogen conversion would help advance the research in this expanding area. This review will cover the physicochemical properties of copper-based chalco-genides, developments of various photocathodes, strategies to enhance the PEC activity and stability, introductions of tandem PEC cells, and finally, prospects on their potential for the practical solar-to-hydrogen conversion. We believe this review article can provide some insights of fundamentals and applications of copper-based chalco-genide thin films for PEC water splitting.

  3. Solar Hydrogen Production by Amorphous Silicon Photocathodes Coated with a Magnetron Sputter Deposited Mo2C Catalyst.

    Science.gov (United States)

    Morales-Guio, Carlos G; Thorwarth, Kerstin; Niesen, Bjoern; Liardet, Laurent; Patscheider, Jörg; Ballif, Christophe; Hu, Xile

    2015-06-10

    Coupling of Earth-abundant hydrogen evolution catalysts to photoabsorbers is crucial for the production of hydrogen fuel using sunlight. In this work, we demonstrate the use of magnetron sputtering to deposit Mo2C as an efficient hydrogen evolution reaction catalyst onto surface-protected amorphous silicon (a-Si) photoabsorbers. The a-Si/Mo2C photocathode evolves hydrogen under simulated solar illumination in strongly acidic and alkaline electrolytes. Onsets of photocurrents are observed at potentials as positive as 0.85 V vs RHE. Under AM 1.5G (1 sun) illumination, the photocathodes reach current densities of -11.2 mA cm(-2) at the reversible hydrogen potential in 0.1 M H2SO4 and 1.0 M KOH. The high photovoltage and low-cost of the Mo2C/a-Si assembly make it a promising photocathode for solar hydrogen production.

  4. Direct observation of bi-alkali antimonide photocathodes growth via in operando x-ray diffraction studies

    Directory of Open Access Journals (Sweden)

    M. Ruiz-Osés

    2014-12-01

    Full Text Available Alkali antimonides have a long history as visible-light-sensitive photocathodes. This work focuses on the process of fabrication of the bi-alkali photocathodes, K2CsSb. In-situ synchrotron x-ray diffraction and photoresponse measurements were used to monitor phase evolution during sequential photocathode growth mode on Si(100 substrates. The amorphous-to-crystalline transition for the initial antimony layer was observed at a film thickness of 40 Å . The antimony crystalline structure dissolved upon potassium deposition, eventually recrystallizing upon further deposition into K-Sb crystalline modifications. This transition, as well as the conversion of potassium antimonide to K2CsSb upon cesium deposition, is correlated with changes in the quantum efficiency.

  5. A polarized photoluminescence study of strained layer GaAs photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Mair, R.A.

    1996-07-01

    Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to {approximately}0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, {approx}78 K and {approx}12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16{+-}.21 eV, b = -2.00{+-}.05 eV and d = -4.87{+-}.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data.

  6. Analysis of emittance compensation and simulation results to photo-cathode RF gun

    CERN Document Server

    LiuShengGuang

    2002-01-01

    The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 pi mm centre dot mrad, electron energy E = 5.71 MeV

  7. Slice emittance measurement for photocathode RF gun with solenoid scanning and RF deflecting cavity

    Science.gov (United States)

    Li, Chen; Huang, WenHui; Du, YingChao; Yan, LiXin; Tang, ChuanXiang

    2011-12-01

    The radiation of high-gain short-wavelength free-electron laser depends on the slice transverse emittance of the electron bunch. This essay introduces the method of slice emittance measurement, and shows the brief setup of this experiment using the solenoid scanning and RF deflecting cavity at Tsinghua University. The preliminary experimental results show that the slice rms emittance of the electron bunch generated by photocathode RF gun has considerable variations along the bunch and is typically less than 0.55 mm mrad for the laser rms radius of 0.4 mm.

  8. Slice emittance measurement for photocathode RF gun with solenoid scanning and RF deflecting cavity

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The radiation of high-gain short-wavelength free-electron laser depends on the slice transverse emittance of the electron bunch. This essay introduces the method of slice emittance measurement, and shows the brief setup of this experiment using the solenoid scanning and RF deflecting cavity at Tsinghua University. The preliminary experimental results show that the slice rms emittance of the electron bunch generated by photocathode RF gun has considerable variations along the bunch and is typically less than 0.55 mm mrad for the laser rms radius of 0.4 mm.

  9. Generation and measurement of sub-picosecond electron bunch in photocathode rf gun

    CERN Document Server

    Li, Weiwei; Jia, Qika

    2013-01-01

    We consider a scheme to generate sub-picosecond electron bunch in the photocathode rf gun by improving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric.

  10. Commissioning of photocathode RF gun based microtron at JAERI-Kansai

    Energy Technology Data Exchange (ETDEWEB)

    Kando, M.; Kotaki, H.; Kondo, S. [Japan Atomic Energy Research Inst., Kyoto (Japan). Kansai Research Establishment] [and others

    2000-07-01

    We started to construct a high quality electron beam injector that consists of a photocathode rf gun and a racetrack microtron last summer. This injector will be used the second generation laser wakefield acceleration experiment at JAERI-Kansai. Beam commissioning of the system is started from this March and we succeeded in generating a 150 MeV electron single bunch with a charge of 91 pC at 10 Hz. Overview of the system and the present status of beam commissioning are described. (author)

  11. Influence of surface properties on the quantum photoyield of diamond photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Foord, J.S.; Wang, J.; Lau, C.H.; Hiramatsu, M.; Vickers, J. [Oxford Univ. (United Kingdom). Physical and Theoretical Chemistry Lab.; Jackman, R.B. [University Coll., London (United Kingdom). Dept. of Electrical and Electronic Engineering

    2001-07-23

    The quantum efficiency and chemical stability of CVD diamond photocathodes has been examined. As-grown or microwave plasma hydrogenated boron-doped diamond films display a quantum photoyield of approximately 0.05% at 190 nm, which degrades gradually as the material is left in ambient atmosphere, due to slow oxidation. Rapid degradation in performance occurs when exposed to atomic or electronically excited oxygen. X-ray photoelectron spectroscopy shows that the yield drops close to zero at around monolayer oxygen coverage, and that the main oxygen species on the surface is hydroxyl or isolated ether linkages. (orig.)

  12. Influence of cesium on the stability of a GaAs photocathode

    Institute of Scientific and Technical Information of China (English)

    Zhang Jun-Ju; Chang Ben-Kang; Fu Xiao-Qian; Du Yu-Jie; Li Biao; Zou Ji-Jun

    2011-01-01

    The stability of a reflection-mode GaAs photocathode has been investigated by monitoring the photocurrent and the spectral response at room temperature.We observe the photocurrent of the cathode decaying with time in the vacuum system under the action of Cs current,and find that the Cs atoms residing in the vacuum system are helpful in prolonging the life of the cathode.We examine the evolution and analyse the influence of the barrier on the spectral response of the cathode.Our results support the double dipolar model for the explanation of the negative electron affinity effect.

  13. Noble metal-free hydrogen-evolving photocathodes based on small molecule organic semiconductors

    Science.gov (United States)

    Morozan, A.; Bourgeteau, T.; Tondelier, D.; Geffroy, B.; Jousselme, B.; Artero, V.

    2016-09-01

    Organic semiconductors have great potential for producing hydrogen in a sustainable and economically-viable manner because they rely on readily available materials with highly tunable properties. We demonstrate here the relevance of heterojunctions to the construction of H2-evolving photocathodes, exclusively based on earth-abundant elements. Boron subnaphthalocyanine chloride proved a very promising acceptor in that perspective. It absorbs a part of the solar spectrum complementary to α-sexithiophene as a donor, thus generating large photocurrents and providing a record onset potential for light-driven H2 evolution under acidic aqueous conditions using a nanoparticulate amorphous molybdenum sulfide catalyst.

  14. A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane.

    Science.gov (United States)

    Wang, Yichen; Fan, Shizhao; AlOtaibi, Bandar; Wang, Yongjie; Li, Lu; Mi, Zetian

    2016-06-20

    A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2 ) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e(-) photoreduction to CH4 at -1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e(-) reduced CO (ca. 0.6 %).

  15. Passivation of c-Si surfaces by sub-nm amorphous silicon capped with silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Yimao, E-mail: yimao.wan@anu.edu.au; Yan, Di; Bullock, James; Zhang, Xinyu; Cuevas, Andres [Research School of Engineering, The Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2015-12-07

    A sub-nm hydrogenated amorphous silicon (a-Si:H) film capped with silicon nitride (SiN{sub x}) is shown to provide a high level passivation to crystalline silicon (c-Si) surfaces. When passivated by a 0.8 nm a-Si:H/75 nm SiN{sub x} stack, recombination current density J{sub 0} values of 9, 11, 47, and 87 fA/cm{sup 2} are obtained on 10 Ω·cm n-type, 0.8 Ω·cm p-type, 160 Ω/sq phosphorus-diffused, and 120 Ω/sq boron-diffused silicon surfaces, respectively. The J{sub 0} on n-type 10 Ω·cm wafers is further reduced to 2.5 ± 0.5 fA/cm{sup 2} when the a-Si:H film thickness exceeds 2.5 nm. The passivation by the sub-nm a-Si:H/SiN{sub x} stack is thermally stable at 400 °C in N{sub 2} for 60 min on all four c-Si surfaces. Capacitance–voltage measurements reveal a reduction in interface defect density and film charge density with an increase in a-Si:H thickness. The nearly transparent sub-nm a-Si:H/SiN{sub x} stack is thus demonstrated to be a promising surface passivation and antireflection coating suitable for all types of surfaces encountered in high efficiency c-Si solar cells.

  16. Radio Supernovae: Circum-Stellar Investigation (C.S.I.) of Supernova Progenitor Stars

    Science.gov (United States)

    2009-02-24

    ar X iv :0 90 2. 40 59 v1 [ as tr o- ph .H E ] 2 4 Fe b 20 09 Radio Supernovae : Circum-Stellar Investigation (C.S.I.) of Supernova Progenitor...FEB 2009 2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Radio Supernovae : Circum-Stellar Investigation (C.S.I...of Supernova Progenitor Stars 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f

  17. Sequential C-Si Bond Formations from Diphenylsilane: Application to Silanediol Peptide Isostere Precursors

    DEFF Research Database (Denmark)

    Nielsen, Lone; Skrydstrup, Troels

    2008-01-01

    and the first new carbon-silicon bond. The next step is the reduction of this hydridosilane with lithium metal providing a silyl lithium reagent, which undergoes a highly diastereoselective addition to an optically active tert-butanesulfinimine, thus generating the second C-Si bond. This method allows......-step assembly of the carbon-silicon backbone of a silane-containing dipeptide fragment. The synthetic scheme is comprised of an alkene hydrosilylation step with the simple precursor, diphenylsilane, using either a radical initiator or RhCl(PPh3)3, Wilkinson's catalyst, for the creation of a hydridosilane...

  18. On the low SNR capacity of log-normal turbulence channels with full CSI

    KAUST Repository

    Benkhelifa, Fatma

    2014-09-01

    In this paper, we characterize the low signal-To-noise ratio (SNR) capacity of wireless links undergoing the log-normal turbulence when the channel state information (CSI) is perfectly known at both the transmitter and the receiver. We derive a closed form asymptotic expression of the capacity and we show that it scales essentially as λ SNR where λ is the water-filling level satisfying the power constraint. An asymptotically closed-form expression of λ is also provided. Using this framework, we also propose an on-off power control scheme which is capacity-achieving in the low SNR regime.

  19. Streak tube photocathode development program. Phase 2, Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    1993-11-20

    This report details the progress made toward developing a streak tube with greater than 1% quantum efficiency at a wavelength of 1300 nm. The achieved performance is the result of approximately three years of effort. The goal of Phase 2 of this contract was to seal a working 1.3 {mu}m streak tube. This effort was focused in two areas. First there was a continuing effort to further develop and demonstrate the cathodes ability to meet the stated requirements. The second effort was aimed at solving the mechanical and process related problems related to sealing this cathode onto a EG&G streak tube.

  20. Poly 3-Hexylthiophene as a photocathode for solar water splitting

    OpenAIRE

    Suppes, Graeme McCallum

    2015-01-01

    The focus of this research is to determine the extent to which poly 3-hexylthiophene (P3HT) can be used as a photoelectrode for solar water splitting. Research in the area of solar water splitting mostly focuses on inorganic materials but conjugated polymers, such as P3HT, offer several advantages. Most metal oxides used as photoelectrodes are only able to carry out water oxidation, require thick films to absorb significant amounts of light, and absorb light mainly in the ultraviolet part of ...

  1. New EBCCD with transferred electron photocathode for range-gated active imaging system

    Science.gov (United States)

    Xu, Xiaowen; Guo, Jin

    2002-09-01

    A detailed comparison between conventional image intensifiers and electron bombarded CCD (EBCCD) is conducted. These sensors' advantages and drawbacks are analyzed. EBCCD with transferred electron (TE) photocathode and its application in Laser Illuminated Viewing and Ranging (LIVAR) system are shown in details. The TE Photocathode (TEP) developed by Intevac in 1996 has a demonstrated quantum efficiency of 20% or higher over the spectral range between 0.95 and 1.7 μm. The TEP is coupled directly with a CCD chip in an electron bombarded CCD (EBCCD) configuration. The overall noise figure of the EBCCD camera is close to one, approximately half that of a standard Generation-III image intensifier. The EBCCD eliminates the micro-channel plate (MCP), phosphor screen, and fiber optics, and as a result both improved image quality and increased sensitivity can be obtained in a smaller sized camera. Because of the reduction in the number of image conversions and the significantly greater signal-to-noise performance, an EBCCD has higher contrast and resolution than an ICCD. These characteristics make the EBCCD a good candidate for military, helmet-mounted night-vision systems as well as for covert surveillance applications.

  2. Improved Ion Resistance for III-V Photocathodes in High Current Guns

    Energy Technology Data Exchange (ETDEWEB)

    Mulhollan, Gregory, A.

    2012-11-16

    The two photocathode test systems were modified, baked and recommissioned. The first system was dedicated to ion studies and the second to electron stimulated recovery (ESR) work. The demonstration system for the electron beam rejuvenation was set up, tested and demonstrated to one of the SSRL team (Dr. Kirby) during a site visit. The requisite subsystems were transferred to SSRL, installed and photoemission studies conducted on activated surfaces following electron beam exposure. Little surface chemistry change was detected in the photoemission spectra following the ESR process. The yield mapping system for the ion (and later, the electron beam rejuvenation) studies was implemented and use made routine. Ion species and flux measurements were performed for H, He, Ne, Ar, Kr and Xe ions at energies of 0.5, 1.0 and 2.0 kV. Gas induced photoyield measurements followed each ion exposure measurement. These data permit the extraction of photoyield induced change per ion (by species) at the measured energies. Electron beam induced rejuvenation was first demonstrated in the second chamber with primary electron beam energy and dependency investigations following. A Hiden quadrupole mass spectrometer for the electron stimulated desorption (ESD) measurements was procured. The UHV test systems needed for subsequent measurements were configured, baked, commissioned and utilized for their intended purposes. Measurements characterizing the desorption products from the ESD process and secondary electron (SE) yield at the surfaces of negative electron affinity GaAs photocathodes have been performed. One US Utility Patent was granted covering the ESR process.

  3. The optimal thickness of a transmission-mode GaN photocathode

    Institute of Scientific and Technical Information of China (English)

    Wang Xiao-Hui; Shi Feng; Guo Hui; Hu Cang-Lu; Cheng Hong-Chang; Chang Ben-Kang; Ren Ling; Du Yu-Jie; Zhang Jun-Ju

    2012-01-01

    A 150-nm-thick GaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber,and a quantum efficiency (QE) curve of the negative electron affinity transmission-mode (t-mode) of the GaN photocathode is obtained.The maximum QE reaches 13.0% at 290 nm.According to the t-mode QE equation solved from the diffusion equation,the QE curve is fitted.From the fitting results,the electron escape probability is 0.32,the back-interface recombination velocity is 5 × 104 cm·s-1,and the electron diffusion length is 116 nm.Based on these parameters,the influence of GaN thickness on t-mode QE is simulated.The simulation shows that the optimal thickness of GaN is 90 nm,which is better than the 150-nm GaN.

  4. Enhanced Photocatalytic Hydrogen Production By Surface Modification of p-Gap Photocathodes

    DEFF Research Database (Denmark)

    Malizia, Mauro; Seger, Brian; Chorkendorff, Ib;

    2014-01-01

    maximum photocurrent density of about 12.5 mA/cm2. The best solar cells made of GaP show an open-circuit voltage of approximately 1.5 V and a maximum photocurrent density close to 2 mA/cm2. p-GaP utilized as a photocathode for hydrogen evolution shows significantly lower open-circuit voltage (+0.35 V RHE...... into hydrogen and oxygen (1.23 V) without external applied bias. It is therefore desirable that the photon absorbers utilized in such device provide the highest photovoltage possible together with a significant current density. GaP is a semiconductor material having 2.25 eV indirect bandgap and a theoretical...... electrons towards the surface of the photoelectrode with the hydrogen evolution reaction occurring at more positive potential compared to the bare p-GaP under the same operating conditions. The observed open-circuit voltage for the modified photocathodes is +0.70 V RHE, representing an increase of more than...

  5. Use of non evaporable getter pumps to ensure long term performances of high quantum efficiency photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Sertore, Daniele, E-mail: daniele.sertore@mi.infn.it; Michelato, Paolo; Monaco, Laura [Istituto Nazionale di Fisica Nucleare Sez. Milano – LASA, Via Fratelli Cervi 201, I-20090 Segrate (Italy); Manini, Paolo; Siviero, Fabrizio [SAES Getters S.p.A., Viale Italia 77, 20020 Lainate (Italy)

    2014-05-15

    High quantum efficiency photocathodes are routinely used as laser triggered emitters in the advanced high brightness electron sources based on radio frequency guns. The sensitivity of “semiconductor” type photocathodes to vacuum levels and gas composition requires special care during preparation and handling. This paper will discuss the results obtained using a novel pumping approach based on coupling a 20 l s{sup −1} sputter ion getter pump with a CapaciTorr® D100 non evaporable getter (NEG) pump. A pressure of 8⋅10{sup −8} Pa was achieved using only a sputter ion pump after a 6 day bake-out. With the addition of a NEG pump, a pressure of 2⋅10{sup −9} Pa was achieved after a 2 day bake-out. These pressure values were maintained without power due to the ability of the NEG to pump gases by chemical reaction. Long term monitoring of cathodes quantum efficiencies was also carried out at different photon wavelengths for more than two years, showing no degradation of the photoemissive film properties.

  6. Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

    Science.gov (United States)

    Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

    2016-09-01

    For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

  7. Using TiO2 as a Conductive Protective Layer for Photocathodic H2 Evolution

    DEFF Research Database (Denmark)

    Seger, Brian; Pedersen, Thomas; Laursen, Anders Bo

    2013-01-01

    Surface passivation is a general issue for Si-based photoelectrodes because it progressively hinders electron conduction at the semiconductor/electrolyte interface. In this work, we show that a sputtered 100 nm TiO2 layer on top of a thin Ti metal layer may be used to protect an n+p Si photocathode...... during photocatalytic H2 evolution. Although TiO2 is a semiconductor, we show that it behaves like a metallic conductor would under photocathodic H2 evolution conditions. This behavior is due to the fortunate alignment of the TiO2 conduction band with respect to the hydrogen evolution potential, which...... allows it to conduct electrons from the Si while simultaneously protecting the Si from surface passivation. By using a Pt catalyst the electrode achieves an H2 evolution onset of 520 mV vs NHE and a Tafel slope of 30 mV when illuminated by the red part (λ > 635 nm) of the AM 1.5 spectrum. The saturation...

  8. Opportunistic Energy-Aware Amplify-and-Forward Cooperative Systems with Imperfect CSI

    KAUST Repository

    Amin, Osama

    2015-07-29

    Recently, much attention has been paid to the green design of wireless communication systems using energy efficiency (EE) metrics that should capture all energy consumption sources to deliver the required data. In this paper, we design an energyefficient relay assisted communication system based on estimated channel state information (CSI). It employs amplify-andforward relaying and switches between different communication schemes, which are known as direct-transmission, two-hop and cooperative-transmission schemes, using the estimated CSI in order to maximize the EE. Two estimation strategies are assumed, namely disintegrated channel estimation and cascaded channel estimation. To formulate an accurate EE metric for the proposed opportunistic amplify-and-forward system, the channel estimation cost is reflected on the EE metric by including its impact in the signal-to-noise ratio term and in the energy consumption during the channels estimation phase. Based on the formulated EE metric, we propose an adaptive power allocation algorithm to maximize the EE of the proposed opportunistic amplify-andforward system with channel estimation. Furthermore, we study the impact of the estimation parameters on the proposed system via simulation examples.

  9. Al2O3 Passivation on c-si Surfaces for Low Temperature Solar Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Saynova, D.S.; Janssen, G.J.M.; Burgers, A.R.; Mewe, A.A. [ECN Solar Energy, Westerduinweg 3, NL-1755 LE Petten (Netherlands); Cianci, E.; Seguini, G.; Perego, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2,I-20864 Agrate Brianza MB (Italy)

    2013-07-01

    Functional passivation of high resistivity p-type c-Si wafer surfaces was achieved using 10 nm Al2O3 layers and low temperatures for both the thermal ALD process and post-deposition anneal. Effective lifetime values higher than 1 ms were measured at excess carrier density {delta}n=1015 cm{sup -3}. This result was reached in combination with temperatures of 100C and 200C for the Al2O3 layer deposition and anneal, respectively. The Al2O3/c-Si interface was characterized using conductance-voltage and capacitance-voltage measurements. In particular, significantly reduced interface density of the electrically active defects Dit {approx} 2x1010 eV{sup -1}cm{sup -2} was detected, which enabled excellent chemical passivation. The measured density of fixed charges at the interface, Qf, after anneal were in the range +1x10{sup 12} to -1x10{sup 12} cm{sup -2} indicating that both inversion and accumulation conditions result in relevant field-effect passivation using Al2O3 layers and low temperature processes. Numerical simulations on representative test structures show that the uniform Qf effect can be understood in terms of a surface damage region (SDR) present near the interface in combination with asymmetry in the lifetime of holes and electrons in the SDR. The combination of low processing temperatures, thin layers and good passivation properties facilitate a technology for future low temperature solar cell applications.

  10. Optical properties of CsI single crystals irradiated with neutrons at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Okada, M. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Nakagawa, M. [Faculty of Education, Kagawa Univ., Takamatsu, Kagawa (Japan); Atobe, K. [Faculty of Science, Naruto Univ. of Education, Naruto, Tokushima (Japan); Itatani, N.; Ozawa, K. [Horiba Ltd., Minamiku, Kyoto (Japan)

    1998-05-01

    Optical properties of the irradiation-induced-defects in neutron-irradiated CsI single crystals have been investigated. The nominally pure CsI crystals are irradiated by reactor fast neutrons (E>0.1 MeV) with a fluence of 1.4 x 10{sup 15} n/cm{sup 2} at 20 K and by {gamma}-rays from {sup 60}Co source to a dose of 1.5 x 10{sup 4} Gy at liquid nitrogen temperature (LNT). After the irradiations, isochronal annealings are performed to investigate the thermal behavior of the defects. The glow peaks of the thermoluminescence (TL) in each sample irradiated with neutrons at 20 K and with {gamma}-rays at LNT are observed at about 100, 160 and 220 K. In the neutron-irradiated samples at 20 K, the emission band at 338 nm is observed at LNT. It is supposed that this emission band occurs by an excitation of {gamma}-rays from {sup 134}Cs, which is radioactivated by thermal neutrons among the reactor radiations. It is confirmed that the temperature dependence of the 338 nm band is similar with that of the emission band due to the self-trapped exciton which is introduced into the non-irradiated samples illuminated by higher energy photons. (orig.) 13 refs.

  11. Nanoscale triboactivity of functionalized c-Si surfaces by Fe+ ion implantation

    Science.gov (United States)

    Nunes, B.; Alves, E.; Colaço, R.

    2016-04-01

    In the present work, we present a study of the effect of Fe+ ion implantation on the tribological response at nanoscale contact lengths of crystalline silicon (c-Si) surfaces. (1 0 0) silicon wafers were implanted with Fe+ at a fluence of 2  ×  1017 cm-2, followed by annealing treatments at temperatures of 800 °C and 1000 °C. After microstructural characterization, nanoabrasive wear tests were performed with an atomic force microscope (AFM) using an AFM diamond tip with a stiff steel cantilever that enables the application of loads between 1 μN and 8 μN. After the nanowear tests, the same AFM was used to visualize and measure the worn craters. It was observed that the as-implanted samples present the poorest nanowear response, i.e. the highest wear rate, even higher than that of the unimplanted Si wafers used as a reference. Nevertheless, annealing treatments result in a measurable increase in the nanowear resistance. In this way we show that Fe+ ion implantation of c-Si, followed by the proper post-heat treatment, results in the formation of FeSi2 nanoprecipitates finely dispersed in a recrystallized matrix. This can be a valuable way of optimizing the nanotribological behavior of silicon.

  12. Longitudinal uniformity, time performance and irradiation test of pure CsI crystals

    CERN Document Server

    Angelucci, M; Baccaro, S; Cemmi, A; Cordelli, M; Donghia, R; Giovannella, S; Happacher, F; Miscetti, S; Sarra, I; Soleti, S R

    2016-01-01

    To study an alternative to BaF2, as the crystal choice for the Mu2e calorimeter, thirteen pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~ 100 p.e./MeV (~ 150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average around -0.6 %/cm. The timing performances of the Opto Materials crystal, read with a UV extended MPPC, have been evaluated with minimum ionizing particles. A timing resolution of ~ 330 ps (~ 440 ps) is achieved when connecting the photosensor to the MPPC with (without) optical grease. The crystal radiation hardness to a ionization dose has also been studied for one pure CsI crystal from SICCAS. After exposing it to a dose of 900 Gy, a decrease of 33% in the LY is observed while the LRU remains unchanged.

  13. Csy4 is responsible for CRISPR RNA processing in Pectobacterium atrosepticum.

    Science.gov (United States)

    Przybilski, Rita; Richter, Corinna; Gristwood, Tamzin; Clulow, James S; Vercoe, Reuben B; Fineran, Peter C

    2011-01-01

    CRISPR/Cas systems provide bacteria and archaea with small RNA-based adaptive immunity against foreign elements such as phages and plasmids. An important step in the resistance mechanism involves the generation of small guide RNAs (crRNAs) that, in combination with Cas proteins, recognize and inhibit foreign nucleic acids in a sequence specific manner. The generation of crRNAs requires processing of the primary CRISPR RNA by an endoribonuclease. In this study we have characterized the Ypest subtype CRISPR/Cas system in the plant pathogen Pectobacterium atrosepticum. We analyse the transcription of the cas genes and the 3 CRISPR arrays. The cas genes are expressed as an operon and all three CRISPR arrays are transcribed and processed into small RNAs. The Csy4 protein was identified as responsible for processing of CRISPR RNA in vivo and in vitro into crRNAs and appears to interact with itself in the absence of other Cas proteins. This study furthers our understanding of the CRISPR/Cas mechanism by providing the first in vivo evidence that the CRISPR endoribonuclease Csy4 generates crRNAs in its native host and characterizes the operonic transcription of the cas cluster.

  14. Performance study of single undoped CsI crystals for the Mu2e experiment

    CERN Document Server

    Donghia, Raffaella

    2016-01-01

    The Mu2e experiment at Fermilab aims to measure the charged lepton flavor violating neutrinoless muon to electron conversion. The goal of the experiment is to reach a single event sensitivity of 2.5 x 10^{-17}, to set an upper limit on the muon conversion rate at 6.7 x 10^{-17} in a three years run. For this purpose, the Mu2e detector is designed to identify electrons from muon conversion and reduce the background to a negligible level. It consists of a low mass straw tracker and a pure CsI crystal calorimeter. In this paper, the performance of undoped CsI single crystal is reported. Crystals from many vendors have been characterized by determining their Light Yield (LY) and Longitudinal Response Uniformity (LRU), when read with a UV extended PMT, and their time resolution when coupled to a Silicon Photomultiplier. The crystals show a LY of ~ 100 photoelectrons per MeV when wrapped with Tyvek and coupled to the PMT without optical grease. The LRU is well represented by a linear slope that is on average 0.6%/c...

  15. MIMO Precoding in Underlay Cognitive Radio Systems with Completely Unknown Primary CSI

    CERN Document Server

    Mukherjee, Amitav; Swindlehurst, A Lee

    2012-01-01

    This paper studies a novel underlay MIMO cognitive radio (CR) system, where the instantaneous or statistical channel state information (CSI) of the interfering channels to the primary receivers (PRs) is completely unknown to the CR. For the single underlay receiver scenario, we assume a minimum information rate must be guaranteed on the CR main channel whose CSI is known at the CR transmitter. We first show that low-rank CR interference is preferable for improving the throughput of the PRs compared with spreading less power over more transmit dimensions. Based on this observation, we then propose a rank minimization CR transmission strategy assuming a minimum information rate must be guaranteed on the CR main channel. We propose a simple solution referred to as frugal waterfilling (FWF) that uses the least amount of power required to achieve the rate constraint with a minimum-rank transmit covariance matrix. We also present two heuristic approaches that have been used in prior work to transform rank minimizat...

  16. Communicating Is Crowdsourcing:Wi-Fi Indoor Localization with CSI-Based Speed Estimation

    Institute of Scientific and Technical Information of China (English)

    韩劲松; 赵鲲; 王志; 肖波; 蒋志平; 惠维; 李向阳; 赵季中; 唐少杰

    2014-01-01

    Numerous indoor localization techniques have been proposed recently to meet the intensive demand for location-based service (LBS). Among them, the most popular solutions are the Wi-Fi fingerprint-based approaches. The core challenge is to lower the cost of fingerprint site-survey. One of the trends is to collect the piecewise data from clients and establish the radio map in crowdsourcing manner. However the low participation rate blocks the practical use. In this work, we propose a passive crowdsourcing channel state information (CSI) based indoor localization scheme, C2IL. Despite a crowdsourcing based approach, our scheme is totally transparent to the client and the only requirement is to connect to our 802.11n access points (APs). C2IL is built upon an innovative method to accurately estimate the moving speed solely based on 802.11n CSI. Knowing the walking speed of a client and its surrounding APs, a graph matching algorithm is employed to extract the received signal strength (RSS) fingerprints and establish the fingerprint map. For localization phase, we design a trajectory clustering based localization algorithm to provide precise real-time indoor localization and tracking. We develop and deploy a practical working system of C2IL in a large office environment. Extensive evaluations indicate that the error of speed estimation is within 3%, and the localization error is within 2 m at 80%time in a very complex indoor environment.

  17. Longitudinal uniformity, time performances and irradiation test of pure CsI crystals

    Energy Technology Data Exchange (ETDEWEB)

    Angelucci, M. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Atanova, O. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Baccaro, S.; Cemmi, A. [ENEA UTTMAT-IRR, Casaccia R.C., Roma (Italy); Cordelli, M. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Donghia, R., E-mail: raffaella.donghia@lnf.infn.it [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dipartimento di Fisica, Universitá Roma Tre, Roma (Italy); Giovannella, S.; Happacher, F.; Miscetti, S.; Sarra, I.; Soleti, S.R. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy)

    2016-07-11

    To study an alternative to BaF{sub 2}, as the crystal choice for the Mu2e calorimeter, 13 pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~100 p.e./MeV (~150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average δ~ −0.6%/cm. The timing performances of the Opto Materials crystal, read with a UV extended MPPC, have been evaluated with minimum ionizing particles. A timing resolution of ~330 ps (~ 440 ps) is achieved when connecting the photosensor to the MPPC with (without) optical grease. The crystal radiation hardness to a ionization dose has also been studied for one pure CsI crystal from SICCAS. After exposing it to a dose of 900 Gy, a decrease of 33% in the LY is observed while the LRU remains unchanged.

  18. Local traps as nanoscale reaction-diffusion probes: B clustering in c-Si

    Energy Technology Data Exchange (ETDEWEB)

    Pawlak, B. J., E-mail: bartekpawlak72@gmail.com [Globalfoundries, Kapeldreef 75, B-3001 Leuven (Belgium); Cowern, N. E. B.; Ahn, C. [School of Electrical and Electronic Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU (United Kingdom); Vandervorst, W. [IMEC, Kapeldreef 75, B-3001 Leuven, Belgium and IKS, Department of Physics, KU Leuven, Leuven (Belgium); Gwilliam, R. [Surrey Ion Beam Centre, Nodus Laboratory, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Berkum, J. G. M. van [Philips CFT, Prof. Holstlaan 4, 5656 AA Eindhoven (Netherlands)

    2014-12-01

    A series of B implantation experiments into initially amorphized and not fully recrystallized Si, i.e., into an existing a/c-Si bi-layer material, have been conducted. We varied B dose, energy, and temperature during implantation process itself. Significant B migration has been observed within c-Si part near the a/c-interface and near the end-of-range region before any activation annealing. We propose a general concept of local trapping sites as experimental probes of nanoscale reaction-diffusion processes. Here, the a/c-Si interface acts as a trap, and the process itself is explored as the migration and clustering of mobile BI point defects in nearby c-Si during implantation at temperatures from 77 to 573 K. We find that at room temperature—even at B concentrations as high as 1.6 atomic %, the key B-B pairing step requires diffusion lengths of several nm owing to a small, ∼0.1 eV, pairing energy barrier. Thus, in nanostructures doped by ion implantation, the implant distribution can be strongly influenced by thermal migration to nearby impurities, defects, and interfaces.

  19. UV laser induced desorption of CsI and RbI ion clusters

    Science.gov (United States)

    Fernández-Lima, F. A.; Ponciano, C. R.; Filho, H. D. Fonseca; Pedrero, E.; Chaer Nascimento, M. A.; da Silveira, E. F.

    2006-09-01

    Experimental results of laser sputtering of cesium and rubidium iodide secondary ions are presented. A TOF mass spectrometer, operating in linear mode, continuous extraction for positive or negative ions, was used for the analysis of (CsI) nCs +, (CsI) nI -, (RbI) nRb + and (RbI) nI - ion emission as a function of the laser irradiance. Experimental data show that the cluster ion emission yields decrease exponentially with n, for all the laser irradiances applied. Theoretical analysis of the clusters structure was performed using density functional theory at the B3LYP/LACV3P level, for the positive and negative cluster series. A quasi-equilibrium evolution of the clusters is proposed to extract a parameter characteristic of the cluster recombination process: the effective temperature. The hypothesis of the atomic species' recombination (during the expansion of a high density highly ionized cloud) leading to cluster formation is confirmed to some extent in a second set of experiments: the UV laser ablation of a mixed and non-mixed cesium iodide and potassium bromide targets. These experiments show that the emission yields contain contributions from both the recombination process and from the sample stoichiometry, even for high laser irradiances.

  20. Environmental Disclosure of Electric Power Companies Listed in the Corporate Sustainability Index (CSI

    Directory of Open Access Journals (Sweden)

    Clésia Ana Gubiani

    2012-12-01

    Full Text Available The study aimed to verify the level of disclosure of environmental information in the administration reports of the energy companies listed in the Corporate Sustainability Index (CSI. A descriptive and quantitative research was done, using the content analysis technique on the administration reports from 2006 to 2008. The sample consisted of 11 electric power companies listed in the CSI. For quantitative analysis of the disclosure index, the data collection instrument was based on the study of Rover, Murcia and Borba (2008, which proposes eight environmental categories and 36 subcategories. For the whole analysis of the data were elaborated networks of the items disclosed in each company, using the software UNICET ®. The survey results showed that there is satisfactory disclosure in the categories of environmental policies and education, training and research environment. However, it was found that there is need for greater disclosure of categories of products impacts and processes in the environment, power polices and financial environmental information. It was concluded that the information disclosed in the administration reports of the companies surveyed about the environmental information do not respect the principle of full disclosure.

  1. Variation of carrier concentration and interface trap density in 8MeV electron irradiated c-Si solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, Sathyanarayana, E-mail: asharao76@gmail.com; Rao, Asha, E-mail: asharao76@gmail.com [Department of Physics, Mangalore Institute of Technology and Engineering, Moodabidri, Mangalore-574225 (India); Krishnan, Sheeja [Department of Physics, Sri Devi Institute of Technology, Kenjar, Mangalore-574142 (India); Sanjeev, Ganesh [Microtron Centre, Department of Physics, Mangalore University, Mangalagangothri-574199 (India); Suresh, E. P. [Solar Panel Division, ISRO Satellite Centre, Bangalore-560017 (India)

    2014-04-24

    The capacitance and conductance measurements were carried out for c-Si solar cells, irradiated with 8 MeV electrons with doses ranging from 5kGy – 100kGy in order to investigate the anomalous degradation of the cells in the radiation harsh environments. Capacitance – Voltage measurements indicate that there is a slight reduction in the carrier concentration upon electron irradiation due to the creation of radiation induced defects. The conductance measurement results reveal that the interface state densities and the trap time constant increases with electron dose due to displacement damages in c-Si solar cells.

  2. Effect of underlying silicon layer on microstructure and photoluminescence of rapid-thermal-annealed carbon and C/Si nanofilms

    Energy Technology Data Exchange (ETDEWEB)

    Chung, C.K., E-mail: ckchung@mail.ncku.edu.tw [Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan, ROC (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, Taiwan, ROC (China); Lai, C.W. [Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan, ROC (China); Wu, B.H. [Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, Taiwan, ROC (China)

    2013-09-15

    Highlights: •Photoluminescence (PL) of carbon films originated from recombination of confined electron–hole pairs. •Broad PL was an interesting topic using varied methods for Si and C reaction. •Asymmetrical broad PL of two-layer Si/C and three-layer Si/C/Si was demonstrated previously. •Here, another C/Si (underlying Si layer) films have further investigated for enhancement of symmetry-like PL. •The effect and mechanism of underlying Si layer thickness on microstructure and PL evolution of two-layer C/Si was studied. -- Abstract: A composite material for broad photoluminescence (PL) from asymmetry to more symmetry-like was proposed by the formation of Si nanocrystals (nc-Si), SiC nanoparticles (np-SiC) and sp{sup 2} carbon cluster which were made from the two-layer C/Si on Si(1 0 0) using rapid-thermal-annealing at 750 °C for 1 min. The effect of underlying Si layer thickness on the microstructure and broad PL of the annealed carbon and two-layer C/Si films has been investigated. Fourier-transform-infrared-absorption spectra indicated that very weak Si–C bonding peak was observed for the annealed single-C film and the enhanced intensity occurred at two-layer C/Si films with underlying thickness of 10–25 nm. Compared to the single-C film, the two-layer C/Si film was beneficial for formation of SiC which increased with Si thickness. A more symmetry-like broad PL band around 400–700 nm was observed at the annealed C/Si films with higher Si thickness of 25 nm while the annealed C film has weak and narrow band. Also, the enhanced symmetry-like PL band was attributed to more amount of np-SiC formation at the bottom of C/Si film together with reduced C thickness which can be potentially applied into white light emission material. The detailed mechanism of broad PL was proposed in terms of microstructure evolution.

  3. Study of a pure CsI crystal readout by APD for Belle II end cap ECL upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y., E-mail: jin@hep.phys.s.u-tokyo.ac.jp [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Aihara, H. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Borshchev, O.V. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation); Epifanov, D.A. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Ponomarenko, S.A.; Surin, N.M. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation)

    2016-07-11

    A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes (Hamamatsu APD S8664-55 and S8664-1010) has been studied for the upgrade of the end cap electromagnetic calorimeter of Belle II detector. An essential increase of the light output was achieved with wavelength shifters based on nanostructured organosilicon luminophores. - Highlights: • A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes has been studied. • The equivalent noise charge and equivalent noise energy of the counter have been measured. • An essential increase of the light output was achieved with wavelength shifters.

  4. Optimal Power Allocation for CC-HARQ-based Cognitive Radio with Statistical CSI in Nakagami Slow Fading Channels

    Science.gov (United States)

    Xu, Ding; Li, Qun

    2017-01-01

    This paper addresses the power allocation problem for cognitive radio (CR) based on hybrid-automatic-repeat-request (HARQ) with chase combining (CC) in Nakagamimslow fading channels. We assume that, instead of the perfect instantaneous channel state information (CSI), only the statistical CSI is available at the secondary user (SU) transmitter. The aim is to minimize the SU outage probability under the primary user (PU) interference outage constraint. Using the Lagrange multiplier method, an iterative and recursive algorithm is derived to obtain the optimal power allocation for each transmission round. Extensive numerical results are presented to illustrate the performance of the proposed algorithm.

  5. Silicon nanowire arrays coupled with cobalt phosphide spheres as low-cost photocathodes for efficient solar hydrogen evolution.

    Science.gov (United States)

    Bao, Xiao-Qing; Fatima Cerqueira, M; Alpuim, Pedro; Liu, Lifeng

    2015-07-01

    We demonstrate the first example of silicon nanowire array photocathodes coupled with hollow spheres of the emerging earth-abundant cobalt phosphide catalysts. Compared to bare silicon nanowire arrays, the hybrid electrodes exhibit significantly improved photoelectrochemical performance toward the solar-driven H2 evolution reaction.

  6. Modulation transfer function characteristic of uniform-doping transmission-mode GaAs/GaAlAs photocathode

    Institute of Scientific and Technical Information of China (English)

    Ren Ling; Chang Ben-Kang

    2011-01-01

    The resolution characteristic can be obtained by the modulation transfer function(MTF)of a GaAs/GaAlAs photocathode.After establishing the theoretical model of GaAs(100)-oriented atomic configuration and the formula for the ionized impurity scattering of the non-equilibrium carriers,this paper calculates the trajectories of photoelectrons in a photocathode.Thus the distribution of photoelectron spots on the emit-face is obtained,which is namely the point spread function.The MTF is obtained by Fourier transfer of the line spread function obtained from the point spread function.The MTF obtained from these calculations is shown to depend heavily on the electron diffusion length,and enhanced considerably by decreasing the electron diffusion length and increasing the doping concentration.Furthermore,the resolution is enhanced considerably by increasing the active-layer thickness,especially at high spatial frequencies.The best spatial resolution is 860 lp/mm,for the GaAs photocathode of doping concentration 1×1019cm-3,electron diffusion length 3.6 μm and the active-layer thickness 2 μm,under the 633-nm light irradiated. This research will contribute to the future improvement of the cathode's resolution for preparing a high performance GaAs photocathode,and improve the resolution of a low light level image intensifier.

  7. Characterization and Performance of a High-Power Solid-State Laser for a High-Current Photocathode Injector

    CERN Document Server

    Zhang, S; Neil, G; Shinn, M D

    2005-01-01

    We report the characterization and performance of a diode-pumped, high-power, picosecond laser system designed for high-current photo-cathode accelerator injector at repetition rates of both 75MHz and 750MHz. Our characterization includes measurement of the system's amplitude stability, beam quality, pulsewidth, and phase noise for both frequencies.

  8. Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

    Directory of Open Access Journals (Sweden)

    F. Urbain

    2014-01-01

    Full Text Available Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination. Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

  9. Silicon nanowire arrays coupled with cobalt phosphide spheres as low-cost photocathodes for efficient solar hydrogen evolution

    OpenAIRE

    Bao, Xiao-Qing; Cerqueira, M.F.; Alpuim, P.; Liu, Lifeng

    2015-01-01

    We demonstrate the first example of silicon nanowire array photocathodes coupled with hollow spheres of the emerging earth-abundant cobalt phosphide catalysts. Compared to bare silicon nanowire arrays, the hybrid electrodes exhibit significantly improved photoelectrochemical performance toward the solar-driven H2 evolution reaction. L. F. Liu acknowledges the financial support by the FCT Investigator grant (IF/01595/2014).

  10. Nickel-Based Dye-Sensitized Photocathode: Towards Proton Reduction Using a Molecular Nickel Catalyst and an Organic Dye

    NARCIS (Netherlands)

    van den Bosch, B.; Rombouts, J.A.; Orru, R.V.A.; Reek, J.N.H.; Detz, R.J.

    2016-01-01

    To construct an efficient dye-sensitized photo-electrochemical tandem cell for hydrogen production, it is crucial to understand the working principles of both the photoanode and the photocathode. Herein, the anchoring of a proton-reduction catalyst and an organic dye molecule on metal oxides is stud

  11. Transmission-mode GaN photocathode based on graded AlxGa1-xN buffer layer

    Institute of Scientific and Technical Information of China (English)

    Xiaoqing Du; Benkang Chang; Yunsheng Qian; Pin Gao

    2011-01-01

    @@ We create a GaN photocathode based on graded AlxGa1-xN buffer layers to overcome the influence of buffer-emission layer interface on the photoemission of transmission-mode GaN photocathodes. A gateshaped spectral response with a 260-nm starting wavelength and a 375-nm cut-off wavelength is obtained.Average quantum efficiency is 15% and short wavelength responses are almost equivalent to long wavelength ones. The fitted interface recombination velocity is 5×104 cm/s, with negligible magnitude, proving that the design of the graded buffer layers is efficient in obtaining good interface quality between the buffer and the emission layer.%We create a GaN photocathode based on graded AlxGa1-xN buffer layers to overcome the influence of buffer-emission layer interface on the photoemission of transmission-mode GaN photocathodes. A gateshaped spectral response with a 260-nm starting wavelength and a 375-nm cut-off wavelength is obtained. Average quantum efficiency is 15% and short wavelength responses are almost equivalent to long wavelength ones. The fitted interface recombination velocity is 5× 104 cm/s, with negligible magnitude, proving that the design of the graded buffer layers is efficient in obtaining good interface quality between the buffer and the emission layer.

  12. Hydrogen Production Using a Molybdenum Sulfide Catalyst on a Titanium-Protected n+p-Silicon Photocathode

    DEFF Research Database (Denmark)

    Seger, Brian; Laursen, Anders Bo; Vesborg, Peter Christian Kjærgaard

    2012-01-01

    A low-cost substitute: A titanium protection layer on silicon made it possible to use silicon under highly oxidizing conditions without oxidation of the silicon. Molybdenum sulfide was electrodeposited on the Ti-protected n+p-silicon electrode. This electrode was applied as a photocathode for water...

  13. Silicon/Carbon Nanotube Photocathode for Splitting Water

    Science.gov (United States)

    Amashukeli, Xenia; Manohara, Harish; Greer, Harold F.; Hall, Lee J.; Gray, Harry B.; Subbert, Bryan

    2013-01-01

    A proof-of-concept device is being developed for hydrogen gas production based on water-splitting redox reactions facilitated by cobalt tetra-aryl porphyrins (Co[TArP]) catalysts stacked on carbon nanotubes (CNTs) that are grown on n-doped silicon substrates. The operational principle of the proposed device is based on conversion of photoelectron energy from sunlight into chemical energy, which at a later point, can be turned into electrical and mechanical power. The proposed device will consist of a degenerately n-doped silicon substrate with Si posts covering the surface of a 4-in. (approximately equal to 10cm) wafer. The substrate will absorb radiation, and electrons will move radially out of Si to CNT. Si posts are designed such that the diameters are small enough to allow considerable numbers of electrons to transport across to the CNT layer. CNTs will be grown on top of Si using conformal catalyst (Fe/Ni) deposition over a thin alumina barrier layer. Both metallic and semiconducting CNT will be used in this investigation, thus allowing for additional charge generation from CNT in the IR region. Si post top surfaces will be masked from catalyst deposition so as to prevent CNT growth on the top surface. A typical unit cell will then consist of a Si post covered with CNT, providing enhanced surface area for the catalyst. The device will then be dipped into a solution of Co[TArP] to enable coating of CNT with Co(P). The Si/CNT/Co [TArP] assembly then will provide electrons for water splitting and hydrogen gas production. A potential of 1.23 V is needed to split water, and near ideal band gap is approximately 1.4 eV. The combination of doped Si/CNT/Co [TArP] will enable this redox reaction to be more efficient.

  14. CSI 3.0: a web server for identifying secondary and super-secondary structure in proteins using NMR chemical shifts.

    Science.gov (United States)

    Hafsa, Noor E; Arndt, David; Wishart, David S

    2015-07-01

    The Chemical Shift Index or CSI 3.0 (http://csi3.wishartlab.com) is a web server designed to accurately identify the location of secondary and super-secondary structures in protein chains using only nuclear magnetic resonance (NMR) backbone chemical shifts and their corresponding protein sequence data. Unlike earlier versions of CSI, which only identified three types of secondary structure (helix, β-strand and coil), CSI 3.0 now identifies total of 11 types of secondary and super-secondary structures, including helices, β-strands, coil regions, five common β-turns (type I, II, I', II' and VIII), β hairpins as well as interior and edge β-strands. CSI 3.0 accepts experimental NMR chemical shift data in multiple formats (NMR Star 2.1, NMR Star 3.1 and SHIFTY) and generates colorful CSI plots (bar graphs) and secondary/super-secondary structure assignments. The output can be readily used as constraints for structure determination and refinement or the images may be used for presentations and publications. CSI 3.0 uses a pipeline of several well-tested, previously published programs to identify the secondary and super-secondary structures in protein chains. Comparisons with secondary and super-secondary structure assignments made via standard coordinate analysis programs such as DSSP, STRIDE and VADAR on high-resolution protein structures solved by X-ray and NMR show >90% agreement between those made with CSI 3.0.

  15. Development of a low-cost-high-sensitivity Compton camera using CsI (Tl) scintillators (γI)

    Energy Technology Data Exchange (ETDEWEB)

    Kagaya, M., E-mail: 13nd401n@vc.ibaraki.ac.jp [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Katagiri, H. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Enomoto, R. [Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Open-It consortium (Japan); Hanafusa, R.; Hosokawa, M.; Itoh, Y. [Fuji Electric, 1 Fujimachi, Hino City, Tokyo 191-8502 (Japan); Muraishi, H. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Open-It consortium (Japan); Nakayama, K. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan); Satoh, K. [Shinsei Corporation, 4-9-1 Nihonbashi-honcho, Chuo-ku, Tokyo 103-0023 (Japan); Takeda, T. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Tanaka, M.M.; Uchida, T. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba City, Ibaraki 305-0801 (Japan); Open-It consortium (Japan); Watanabe, T. [School of Allied Health Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara City, Kanagawa 252-0373 (Japan); Open-It consortium (Japan); Yanagita, S.; Yoshida, T.; Umehara, K. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito City, Ibaraki 310-8512 (Japan); Open-It consortium (Japan)

    2015-12-21

    We have developed a novel low-cost gamma-ray imaging Compton camera γI that has a high detection efficiency. Our motivation for the development of this detector was to measure the arrival directions of gamma rays produced by radioactive nuclides that were released by the Fukushima Daiichi nuclear power plant accident in 2011. The detector comprises two arrays of inorganic scintillation detectors, which act as a scatterer and an absorber. Each array has eight scintillation detectors, each comprising a large CsI (Tl) scintillator cube of side 3.5 cm, which is inexpensive and has a good energy resolution. Energies deposited by the Compton scattered electrons and subsequent photoelectric absorption, measured by each scintillation counter, are used for image reconstruction. The angular resolution was found to be 3.5° after using an image-sharpening technique. With this angular resolution, we can resolve a 1 m{sup 2} radiation hot spot that is located at a distance of 10 m from the detector with a wide field of view of 1 sr. Moreover, the detection efficiency 0.68 cps/MBq at 1 m for 662 keV (7.6 cps/μSv/h) is sufficient for measuring low-level contamination (i.e., less than 1 μSv/h) corresponding to typical values in large areas of eastern Japan. In addition to the laboratory tests, the imaging capability of our detector was verified in various regions with dose rates less than 1 μSv/h (e.g., Fukushima city).

  16. Development of a low-cost-high-sensitivity Compton camera using CsI (Tl) scintillators (γI)

    Science.gov (United States)

    Kagaya, M.; Katagiri, H.; Enomoto, R.; Hanafusa, R.; Hosokawa, M.; Itoh, Y.; Muraishi, H.; Nakayama, K.; Satoh, K.; Takeda, T.; Tanaka, M. M.; Uchida, T.; Watanabe, T.; Yanagita, S.; Yoshida, T.; Umehara, K.

    2015-12-01

    We have developed a novel low-cost gamma-ray imaging Compton camera γI that has a high detection efficiency. Our motivation for the development of this detector was to measure the arrival directions of gamma rays produced by radioactive nuclides that were released by the Fukushima Daiichi nuclear power plant accident in 2011. The detector comprises two arrays of inorganic scintillation detectors, which act as a scatterer and an absorber. Each array has eight scintillation detectors, each comprising a large CsI (Tl) scintillator cube of side 3.5 cm, which is inexpensive and has a good energy resolution. Energies deposited by the Compton scattered electrons and subsequent photoelectric absorption, measured by each scintillation counter, are used for image reconstruction. The angular resolution was found to be 3.5° after using an image-sharpening technique. With this angular resolution, we can resolve a 1 m2 radiation hot spot that is located at a distance of 10 m from the detector with a wide field of view of 1 sr. Moreover, the detection efficiency 0.68 cps/MBq at 1 m for 662 keV (7.6 cps/μSv/h) is sufficient for measuring low-level contamination (i.e., less than 1 μSv/h) corresponding to typical values in large areas of eastern Japan. In addition to the laboratory tests, the imaging capability of our detector was verified in various regions with dose rates less than 1 μSv/h (e.g., Fukushima city).

  17. On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

    Science.gov (United States)

    Hoex, B.; Gielis, J. J. H.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2008-12-01

    Al2O3 is a versatile high-κ dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high-efficiency solar cells. We demonstrate both experimentally and by simulations that the surface passivation can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density Qf of up to 1013 cm-2 present in the Al2O3 film at the interface with the underlying Si substrate. The negative polarity of Qf in Al2O3 is especially beneficial for the passivation of p-type c-Si as the bulk minority carriers are shielded from the c-Si surface. As the level of field-effect passivation is shown to scale with Qf2, the high Qf in Al2O3 tolerates a higher interface defect density on c-Si compared to alternative surface passivation schemes.

  18. Effective Passivation of C-Si by Intrinsic A-Si:h Layer for hit Solar Cells

    Directory of Open Access Journals (Sweden)

    Shahaji More

    2011-01-01

    Full Text Available The influence of HF solution etching on surface roughness of c-Si wafer was investigated using AFM. Ultra thin(2-3 nm intrinsic a-Si:H is necessary to achieve high VOC and Fill factor, as it effectively passivates the defects on the surface of c-Si and increase tunneling probability of minority charge carriers. However, to achieve control over ultra-thin intrinsic a-Si:H layer thickness and passivation properties, the films were deposited by Hot-wire CVD. We used tantalum filament and silane (SiH4 as a precursor gas, where as the deposition parameter such as filament temperature temperature was varied. The deposition rate, Dark and Photoconductivity were measured for all the films. The optimized intrinsic a-Si:H layer was inserted between p typed doped layers and n type c-Si wafers to fabricate HIT solar cells. The Current-Voltage characteristics were studied to understand the passivation effect of intrinsic layer on c-Si surface. The high saturation current density (Jsat > 10–7 A/cm2 and Ideality factor (n > 2 were observed. We achieved the efficiency of 3.28 % with the optimized intrinsic and doped a-Si:H layers using HWCVD technique.

  19. Novel Robust Optimization and Power Allocation of Time Reversal-MIMO-UWB Systems in an Imperfect CSI

    Directory of Open Access Journals (Sweden)

    Sajjad Alizadeh

    2013-03-01

    Full Text Available Time Reversal (TR technique is an attractive solution for a scenario where the transmission system employs low complexity receivers with multiple antennas at both transmitter and receiver sides. The TR technique can be combined with a high data rate MIMO-UWB system as TR-MIMO-UWB system. In spite of TR's good performance in MIMO-UWB systems, it suffers from performance degradation in an imperfect Channel State Information (CSI case. In this paper, at first a robust TR pre-filter is designed together with a MMSE equalizer in TR-MIMO-UWB system where is robust against channel imperfection conditions. We show that the robust pre-filter optimization technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI, where temporal focusing of the TR technique is kept, especially for high SNR values. Then, in order to improve the system performance more than ever, a power loading scheme is developed by minimizing the average symbol error rate in an imperfect CSI. Numerical and simulation results are presented to confirm the performance advantage attained by the proposed robust optimization and power loading in an imperfect CSI scenario.

  20. Immobilized nickel hexacyanoferrate on activated carbons for efficient attenuation of radio toxic Cs(I) from aqueous solutions

    Science.gov (United States)

    Lalhmunsiama; Lalhriatpuia, C.; Tiwari, Diwakar; Lee, Seung-Mok

    2014-12-01

    The aim of this study is to immobilize nickel hexacyanoferrate onto the large surface of activated carbons (ACs) precursor to rice hulls and areca nut waste materials. These nickel hexacyanoferrate immobilized materials are then assessed in the effective attenuation of radio logically important cesium ions from aqueous solutions. The solid samples are characterized by the XRD analytical method and surface morphology is obtained from the SEM images. The batch reactor experiments show that an increase in sorptive pH (2.0-10.0) apparently not affecting the high percent uptake of Cs(I). Equilibrium modeling studies suggest that the data are reasonably and relatively fitted well to the Langmuir adsorption isotherm. Kinetic studies show that sorption process is fairly rapid and the kinetic data are fitted well to the pseudo-second order rate model. Increasing the background electrolyte concentration from 0.001 to 0.1 mol/L NaCl causes insignificant decrease in Cs(I) removal which infers the higher selectivity of these materials for Cs(I) from aqueous solutions. Further, the column reactor operations enable to obtain the breakthrough data which are then fitted to the Thomas non-linear equation as to obtain the loading capacity of column for Cs(I). The results show that the modified materials show potential applicability in the attenuation of radio toxic cesium from aqueous solution.

  1. 78 FR 41911 - Foreign-Trade Zone 39-Dallas-Fort Worth, Texas; CSI Calendering, Inc. (Rubber Coated Textile...

    Science.gov (United States)

    2013-07-12

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Foreign-Trade Zone 39--Dallas-Fort Worth, Texas; CSI Calendering, Inc. (Rubber Coated Textile Fabric); Arlington, Texas On March 4, 2013, the Dallas/Fort Worth International...

  2. Monitoring the Recovery of c-Si Modules from Potential-Induced Degradation Using Suns-Voc Curves

    Energy Technology Data Exchange (ETDEWEB)

    Wilterdink, Harrison; Sinton, Ronald; Hacke, Peter; Terwilliger, Kent; Meydbray, Jenya

    2016-11-21

    Potential-induced degradation (PID) has recently been shown as an important failure mode in c-Si modules. We demonstrate the utility of Suns-Voc analysis for measuring shunt effects caused by PID at the module level. Our results show module shunt resistance increasing in step with module power during recovery from the degraded state.

  3. SVD-Aided Beamforming and Power Allocation Algorithm for Multiuser Turbo-BLAST System Uplink with Imperfect CSI

    Directory of Open Access Journals (Sweden)

    Xiaomin Chen

    2012-01-01

    Full Text Available The SVD-aided joint transmitter and receiver design for the uplink of CDMA-based synchronous multiuser Turbo-BLAST systems is proposed in the presence of channel state information (CSI imperfection. At the transmitter, the beamforming and power allocation schemes are developed to maximize the capacity of the desired user. At the receiver, a suboptimal decorrelating scheme is first proposed to mitigate the multiuser interference (MUI and decouple the detection of different users with imperfect CSI, and then the iterative detecting algorithm that takes the channel estimation error into account is designed to cancel the coantenna interference (CAI and enhance the bit error rate (BER results further. Simulation results show that the proposed uplink CDMA-based multiuser Turbo-BLAST model is effective, the detection from every user is completely independent to each other after decorrelating, and the system performance can be enhanced by the proposed beamforming and power allocation schemes. Furthermore, BER performance can be enhanced by the modified iterative detection. The effect of CSI imperfection is evaluated, which is proved to be a useful tool to assess the system performance with imperfect CSI.

  4. Psychometric Evaluation of a Coping Strategies Inventory Short-Form (CSI-SF in the Jackson Heart Study Cohort

    Directory of Open Access Journals (Sweden)

    Herman Taylor

    2007-12-01

    Full Text Available This study sought to establish the psychometric properties of a Coping Strategies Inventory Short Form (CSISF by examining coping skills in the Jackson Heart Study cohort. We used exploratory and confirmatory factor analysis, Pearson’s correlation, and Cronbach Alpha to examine reliability and validity in the CSI-SF that solicited responses from 5302 African American men and women between the ages of 35 and 84. One item was dropped from the 16-item CSI-SF, making it a 15-item survey. No significant effects were found for age and gender, strengthening the generalizability of the CSI-SF. The internal consistency reliability analysis revealed reliability between alpha = 0.58-0.72 for all of the scales, and all of the fit indices used to examine the CSI-SF provided support for its use as an adequate measure of coping. This study provides empirical support for utilizing this instrument in future efforts to understand the role of coping in moderating health outcomes.

  5. Design and fabrication of prototype 6×6 cm{sup 2} microchannel plate photodetector with bialkali photocathode for fast timing applications

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Junqi, E-mail: jxie@anl.gov; Byrum, Karen; Demarteau, Marcel; Gregar, Joseph; May, Edward; Virgo, Mathew; Wagner, Robert; Walters, Dean; Wang, Jingbo; Xia, Lei; Zhao, Huyue

    2015-06-01

    Planar microchannel plate-based photodetectors with a bialkali photocathode are able to achieve photon detection with very good time and position resolution. A 6×6 cm{sup 2} photodetector production facility was designed and built at Argonne National Laboratory. Small form-factor MCP-based photodetectors completely constructed out of glass were designed and prototypes were successfully fabricated. Knudsen effusion cells were incorporated in the photocathode growth chamber to achieve uniform and high quantum efficiency photocathodes. The thin film uniformity was simulated and measured for an antimony film deposition, showing uniformity of better than 10%. Several prototype devices with bialkali photocathodes have been fabricated with the described system and their characteristics were evaluated in the large signal (multi-PE) limit. A typical prototype device exhibits time-of-flight resolution of ~27 psec and differential time resolution of ~9 psec, corresponding to spatial resolution of ~0.65 mm.

  6. A comprehensive comparison of dye-sensitized NiO photocathodes for solar energy conversion.

    Science.gov (United States)

    Wood, Christopher J; Summers, Gareth H; Clark, Charlotte A; Kaeffer, Nicolas; Braeutigam, Maximilian; Carbone, Lea Roberta; D'Amario, Luca; Fan, Ke; Farré, Yoann; Narbey, Stéphanie; Oswald, Frédéric; Stevens, Lee A; Parmenter, Christopher D J; Fay, Michael W; La Torre, Alessandro; Snape, Colin E; Dietzek, Benjamin; Dini, Danilo; Hammarström, Leif; Pellegrin, Yann; Odobel, Fabrice; Sun, Licheng; Artero, Vincent; Gibson, Elizabeth A

    2016-04-28

    We investigated a range of different mesoporous NiO electrodes prepared by different research groups and private firms in Europe to determine the parameters which influence good quality photoelectrochemical devices. This benchmarking study aims to solve some of the discrepancies in the literature regarding the performance of p-DSCs due to differences in the quality of the device fabrication. The information obtained will lay the foundation for future photocatalytic systems based on sensitized NiO so that new dyes and catalysts can be tested with a standardized material. The textural and electrochemical properties of the semiconducting material are key to the performance of photocathodes. We found that both commercial and non-commercial NiO gave promising solar cell and water-splitting devices. The NiO samples which had the two highest solar cell efficiency (0.145% and 0.089%) also gave the best overall theoretical H2 conversion.

  7. Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes.

    Science.gov (United States)

    Britto, Reuben J; Benck, Jesse D; Young, James L; Hahn, Christopher; Deutsch, Todd G; Jaramillo, Thomas F

    2016-06-02

    Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis because MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, and light-limited current density) after 60 h of operation. This represents a 500-fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.

  8. Femtosecond precision measurement of laser-rf phase jitter in a photocathode rf gun

    Science.gov (United States)

    Shi, Libing; Zhao, Lingrong; Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhu, Pengfei; Xiang, Dao

    2017-03-01

    We report on the measurement of the laser-rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser-rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser-rf phase jitter in the gun through measurement of the beam-rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

  9. Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Britto, Reuben J.; Benck, Jesse D.; Young, James L.; Hahn, Christopher; Deutsch, Todd G.; Jaramillo, Thomas F.

    2016-06-02

    Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis since MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, and light limited current density) after 60 hours of operation. This represents a five-hundred fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.

  10. 3D Imaging of Dielectric Objects Buried under a Rough Surface by Using CSI

    Directory of Open Access Journals (Sweden)

    Evrim Tetik

    2015-01-01

    Full Text Available A 3D scalar electromagnetic imaging of dielectric objects buried under a rough surface is presented. The problem has been treated as a 3D scalar problem for computational simplicity as a first step to the 3D vector problem. The complexity of the background in which the object is buried is simplified by obtaining Green’s function of its background, which consists of two homogeneous half-spaces, and a rough interface between them, by using Buried Object Approach (BOA. Green’s function of the two-part space with planar interface is obtained to be used in the process. Reconstruction of the location, shape, and constitutive parameters of the objects is achieved by Contrast Source Inversion (CSI method with conjugate gradient. The scattered field data that is used in the inverse problem is obtained via both Method of Moments (MoM and Comsol Multiphysics pressure acoustics model.

  11. Active strut placement using integer programming for the CSI Revolutionary Model

    Science.gov (United States)

    Padula, Sharon L.; Sandridge, Chris A.

    1992-09-01

    A method for determining the most effective locations for active struts on large space structures is developed and tested on the NASA CSI Evolutionary Model. Depending on the choice of weighting factors, the method can be used to maximize the maximum modal damping ratio or decay rate, or to maximize a mission-oriented measure of performance. Placement of 8, 16, and 32 active struts out of 1507 candidate truss elements is demonstrated. Preliminary estimates of damping enhancement are reported pending refined structural models and dynamic test results. The method can handle complicated FEM models wih a large number of truss elements and many target modes. It can treat each mode equally or it can emphasize the importance of selected modes. The method can eliminate some combinations of actuator locations based on topological constraints.

  12. A CsI low temperature detector for dark matter search

    CERN Document Server

    Angloher, G; Gektin, A; Gironi, L; Gotti, C; Gütlein, A; Hauff, D; Maino, M; Nagorny, S S; Nisi, S; Pagnanini, L; Pattavina, L; Pessina, G; Petricca, F; Pirro, S; Pröbst, F; Reindl, F; Schäffner, K; Schieck, J; Seidel, W; Vasyukov, S

    2016-01-01

    Cryogenic detectors have a long history of success in the field of rare event searches. In particular scintillating calorimeters are very suitable detectors for this task since they provide particle discrimination: the simultaneous detection of the thermal and the light signal produced by a particle interaction in scintillating crystals allows to identify the nature of particle, as the light yield depends thereon. We investigate the performance of two large CsI (undoped) crystals ($\\sim$122 g each) operated as scintillating calorimeters at milli-Kelvin temperatures in terms of calorimetric properties and background rejection capabilities. Furthermore, we discuss the feasibility of this detection approach towards a background-free future dark matter experiment based on alkali halides crystals, with active particle discrimination via the two-channel detection.

  13. A CsI low-temperature detector for dark matter search

    Science.gov (United States)

    Angloher, G.; Dafinei, I.; Gektin, A.; Gironi, L.; Gotti, C.; Gütlein, A.; Hauff, D.; Maino, M.; Nagorny, S. S.; Nisi, S.; Pagnanini, L.; Pattavina, L.; Pessina, G.; Petricca, F.; Pirro, S.; Pröbst, F.; Reindl, F.; Schäffner, K.; Schieck, J.; Seidel, W.; Vasyukov, S.

    2016-11-01

    Cryogenic detectors have a long history of success in the field of rare event searches. In particular scintillating calorimeters are very suitable detectors for this task since two signals are induced by a particle interaction in a scintillating crystal. The thermal signal provides a precise measurement of the deposited energy while the simultaneously measured scintillation light signal yields particle discrimination as the amount of produced scintillation light depends on the nature of the interacting particle. We investigate the calorimetric properties and background rejection capabilities of two large CsI (undoped) crystals (∼122 g each) operated as scintillating calorimeters at milli-Kelvin temperatures. Furthermore, we discuss the feasibility of this detection approach towards a future background-free dark matter experiment based on alkali halide crystals, with active particle discrimination via the two-channel detection.

  14. Evaporated erbium oxide as an antireflective layer for C-Si solar cells

    Science.gov (United States)

    Alizadeh, Hossein; Bahardoust, Barzin; Gougam, Adel; Kherani, Nazir P.; Zukotynski, Stefan

    2009-08-01

    We report on the optical properties of erbium oxide thin films prepared by physical vapor deposition. The films were subjected to various rapid thermal annealing (RTA) treatments. The best result was obtained for samples annealed at 500 °C, where the ramp rate was 200 °C/s, zero soak time, and a cooling rate of 25 °C/s. The average reflection from this erbium oxide coated c-Si substrate, measured over a wavelength range of 300nm to 1100nm, is around 18% and 8% before and after annealing, respectively. The average transmission of erbium oxide on glass is 50 % and 90 % before and after annealing, respectively. Using this antireflection coating the short circuit current of a silicon base photovoltaic device increases by more than 40 %.

  15. Digital transceiver design for two-way AF-MIMO relay systems with imperfect CSI

    Science.gov (United States)

    Hu, Chia-Chang; Chou, Yu-Fei; Chen, Kui-He

    2013-09-01

    In the paper, combined optimization of the terminal precoders/equalizers and single-relay precoder is proposed for an amplify-and-forward (AF) multiple-input multiple-output (MIMO) two-way single-relay system with correlated channel uncertainties. Both terminal transceivers and relay precoding matrix are designed based on the minimum mean square error (MMSE) criterion when terminals are unable to erase completely self-interference due to imperfect correlated channel state information (CSI). This robust joint optimization problem of beamforming and precoding matrices under power constraints belongs to neither concave nor convex so that a nonlinear matrix-form conjugate gradient (MCG) algorithm is applied to explore local optimal solutions. Simulation results show that the robust transceiver design is able to overcome effectively the loss of bit-error-rate (BER) due to inclusion of correlated channel uncertainties and residual self-interference.

  16. On the secrecy capacity of the broadcast wiretap channel with limited CSI feedback

    KAUST Repository

    Hyadi, Amal

    2016-10-27

    In this paper, we investigate the problem of secure broadcasting over block-fading channels with limited channel knowledge at the transmitter. More particularly, we analyze the effect of having imperfect channel state information (CSI) via a finite rate feedback on the throughput of a broadcast channel where the transmission is intended for multiple legitimate receivers in the presence of an eavesdropper. First, we partially characterize the ergodic secrecy capacity of the system when the source broadcasts the same information to all the receivers, i.e., common message transmission. Then, we look at the independent messages case, where the transmitter broadcasts multiple independent messages to the legitimate receivers. For this case, we present lower and upper bounds on the ergodic secrecy sum-capacity. In both scenarios, we show that the proposed lower and upper bounds coincide asymptotically as the capacity of the feedback links becomes large, hence, fully characterizing the secrecy capacity in this case.

  17. CSI: Dognapping workshop : an outreach experiment designed to produce students that are hooked on science.

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, Timothy J.; Gorman, Anna K.; Pratt, Harry D., III; Hernandez-Sanchez, Bernadette A.; Lambert, Timothy N.; Ottley, Leigh Anna M.; Baros, Christina Marie

    2008-04-01

    The CSI: Dognapping Workshop is a culmination of the more than 65 Sandian staff and intern volunteers dedication to exciting and encouraging the next generation of scientific leaders. This 2 hour workshop used a 'theatrical play' and 'hands on' activities that was fun, exciting and challenging for 3rd-5th graders while meeting science curriculum standards. In addition, new pedagogical methods were developed in order to introduce nanotechnology to the public. Survey analysis indicated that the workshop had an overall improvement and positive impact on helping the students to understand concepts from materials science and chemistry as well as increased our interaction with the K-5 community. Anecdotal analyses showed that this simple exercise will have far reaching impact with the results necessary to maintain the United States as the scientific leader in the world. This experience led to the initiation of over 100 Official Junior Scientists.

  18. Two-way CSI-assisted AF relaying with HPA nonlinearity

    KAUST Repository

    Qi, Jian

    2015-09-11

    In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-andforward (AF) relaying in the presence of high-power amplifier (HPA) nonlinearity at relays. The expression for the end-toend signal-to-noise ratio (SNR) is derived as per the modified system model by taking into account the interference caused by relaying scheme and HPA nonlinearity. The system performance of the considered relaying network is evaluated in terms of average symbol error probability (SEP) in Nakagami-m fading channels, by making use of the moment-generating function (MGF) approach. Numerical results are provided and show the effects of several parameters, such as quadrature amplitude modulation (QAM) order, number of relays, HPA parameters, and Nakagami parameter, on performance. © 2015 IEEE.

  19. Inorganic scintillators of Li{sup +} doped CsI for neutron detection

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Maria da Conceicao Costa; Madi Filho, Tufic, E-mail: macoper@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    The scintillation method is still one of the main methods used for the detection of ionizing radiations. The universality of this method is considered to be its major advantage. It may be used for registration of almost all types of radiation in a wide range of energy (1 eV - 10 GeV). In recent years has been an increasing demand for new types of neutron detectors to be used in applications such as spectrometers, photodetectors, materials characterization, and so on. For these applications, inorganic scintillators play an important role in the detection and spectroscopy of neutrons. Scintillation crystals based on cesium iodide (CsI) have relatively low hygroscope, easy handling and low cost, features that favor their use as radiation detectors. In this work, lithium doped CsI crystals were grown using the vertical Bridgman technique. In this technique, the charge is maintained at high temperature for 10 h for the material melting and complete reaction. The temperature gradient 21 deg C/cm and 1 mm/h descending velocity are chosen as technique parameters. The concentration of the lithium doping element (Li) studied was 10{sup -3} M. The optical transmittance measurements were made in the CsI:Li crystal at room temperature, using a spectrophotometer with a wavelength in the range 200 nm to 900 nm. Analyses were carried out to evaluate the scintillators developed, concerning neutron radiation from AmBe source, with the energy range of 1 MeV to 12 MeV. In this paper was investigated, the feasibility of the CsI:Li crystal as a neutron detector to be used for monitoring, due to the fact that in our work environment there are two nuclear research reactors and calibration systems. (author)

  20. FY16 ASC ATDM L2 Milestone: PARTISN Research and FleCSI Updates

    Energy Technology Data Exchange (ETDEWEB)

    Womeldorff, Geoffrey Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Payne, Joshua Estes [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bergen, Benjamin Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-01

    These are slides for a presentation on PARTISN Research and FleCSI Updates. The following topics are covered: SNAP vs PARTISN, Background Research, Production Code (structural design and changes, kernel design and implementation, lessons learned), NuT IMC Proxy, FleCSI Update (design and lessons learned). It can all be summarized in the following manner: Kokkos was shown to be effective in FY15 in implementing a C++ version of SNAP's kernel. This same methodology was applied to a production IC code, PARTISN. This was a much more complex endeavour than in FY15 for many reasons; a C++ kernel embedded in Fortran, overloading Fortran memory allocations, general language interoperability, and a fully fleshed out production code versus a simplified proxy code. Lessons learned are Legion. In no particular order: Interoperability between Fortran and C++ was really not that hard, and a useful engineering effort. Tracking down all necessary memory allocations for a kernel in a production code is pretty hard. Modifying a production code to work for more than a handful of use cases is also pretty hard. Figuring out the toolchain that will allow a successful implementation of design decisions is quite hard, if making use of "bleeding edge" design choices. In terms of performance, production code concurrency architecture can be a virtual showstopper; being too complex to easily rewrite and test in a short period of time, or depending on tool features which do not exist yet. Ultimately, while the tools used in this work were not successful in speeding up the production code, they helped to identify how work would be done, and provide requirements to tools.

  1. Highly Polarized Electrons from GaAs-GaAsP and InGaAs-AlGaAs Strained Layer Superlattice Photocathodes

    CERN Document Server

    Nakanishi, T; Kuwahara, M; Naniwa, K; Nishitani, T; Okumi, S; Yamamoto, N; Yasui, K

    2004-01-01

    GaAs-GaAsP strained layer superlattice photocathode has been developed for highly polarized electron beams. This cathode achieved a maximum polarization of 92% with a quantum efficiency of 0.5%. Criteria for achieving the highest polarization together with high quantum efficiency using superlattice photocathodes are discussed based on experimental spin-resolved quantum efficiency spectra of GaAs-AlGaAs, InGaAs-AlGaAs and GaAs-GaAsP superlattice structures.

  2. Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

    2017-01-01

    We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

  3. Simultaneous enhancement of photovoltage and charge transfer in Cu2O-based photocathode using buffer and protective layers

    Science.gov (United States)

    Li, Changli; Hisatomi, Takashi; Watanabe, Osamu; Nakabayashi, Mamiko; Shibata, Naoya; Domen, Kazunari; Delaunay, Jean-Jacques

    2016-07-01

    Coating n-type buffer and protective layers on Cu2O may be an effective means to improve the photoelectrochemical (PEC) water-splitting performance of Cu2O-based photocathodes. In this letter, the functions of the buffer layer and protective layer on Cu2O are examined. It is found that a Ga2O3 buffer layer can form a buried junction with Cu2O, which inhibits Cu2O self-reduction as well as increases the photovoltage through a small conduction band offset between the two semiconductors. The introduction of a TiO2 thin protective layer not only improves the stability of the photocathode but also enhances the electron transfer from the photocathode surface into the electrolyte, thus resulting in an increase in photocurrent at positive potentials. These results show that the selection of overlayers with appropriate conduction band positions provides an effective strategy for obtaining a high photovoltage and high photocurrent in PEC systems.

  4. 10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources

    Science.gov (United States)

    Yang, Heewon; Han, Byungheon; Shin, Junho; Hou, Dong; Chung, Hayun; Baek, In Hyung; Jeong, Young Uk; Kim, Jungwon

    2017-01-01

    Ultrafast electron-based coherent radiation sources, such as free-electron lasers (FELs), ultrafast electron diffraction (UED) and Thomson-scattering sources, are becoming more important sources in today’s ultrafast science. Photocathode laser is an indispensable common subsystem in these sources that generates ultrafast electron pulses. To fully exploit the potentials of these sources, especially for pump-probe experiments, it is important to achieve high-precision synchronization between the photocathode laser and radio-frequency (RF) sources that manipulate electron pulses. So far, most of precision laser-RF synchronization has been achieved by using specially designed low-noise Er-fibre lasers at telecommunication wavelength. Here we show a modular method that achieves long-term (>1 day) stable 10-fs-level synchronization between a commercial 79.33-MHz Ti:sapphire laser oscillator and an S-band (2.856-GHz) RF oscillator. This is an important first step toward a photocathode laser-based femtosecond RF timing and synchronization system that is suitable for various small- to mid-scale ultrafast X-ray and electron sources.

  5. Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light.

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

    2017-12-01

    We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

  6. Enhancement of photocathodic stability of p-type copper(I) oxide electrodes by surface etching treatment

    Energy Technology Data Exchange (ETDEWEB)

    Amano, Fumiaki, E-mail: amano@kitakyu-u.ac.jp [Catalysis Research Center, Hokkaido University, Sapporo 001-0021 (Japan); Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemical and Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0135 (Japan); Ebina, Toshihiro [Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan); Ohtani, Bunsho [Catalysis Research Center, Hokkaido University, Sapporo 001-0021 (Japan); Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2014-01-01

    The photoelectrochemical properties of electrodeposited p-type copper(I) oxide (Cu{sub 2}O) films were investigated using methyl viologen (MV{sup 2+}) as an electron acceptor. The pristine Cu{sub 2}O films were deactivated during the photocathodic reaction as a result of self-reduction, whereas the (111)-oriented Cu{sub 2}O films treated in an aqueous solution containing hexamethylenetetramine at pH 5 and 90 °C exhibited stable photocurrent for MV{sup 2+} reduction into the cation radical. Scanning electron microscope images showed that the treated films contained smaller crystal grains than untreated ones. X-ray photoelectron spectroscopy revealed that the treatment etched the thin layer of copper(II) oxide from the Cu{sub 2}O polycrystalline surface. Etching of the film surface enhanced the stability and steady-state photocurrent for photocathodic reduction of MV{sup 2+}, suggesting that the crystalline composition and structures exposed on the outermost surface of Cu{sub 2}O polycrystalline films have a considerable influence on the selectivity for the photocathodic reaction over self-reduction. - Highlights: • Photoelectrochemical reduction of methyl viologen by (111)-oriented Cu{sub 2}O thin films • Cu{sub 2}O films are etched using an aqueous solution containing hexamethylenetetramine. • Etching decreases crystal grain size and removes the thin layer of CuO. • Etching enhances the stability of Cu{sub 2}O photoelectrodes.

  7. Measurements of the radiolytic oxidation of aqueous CsI using a sparging apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Ashmore, C.B.; Brown, D.; Sims, H.E. [AEA Technology, Harwell (United Kingdom); Gwyther, J.R. [NE plc Berkeley Technology Centre, Berkeley (United Kingdom)

    1996-12-01

    Radiolytic oxidation is considered to be the main mechanism for the formation of I{sub 2} from aqueous CsI in containment of a water cooled reactor after a LOCA. Despite the amount of study over the last 60 years on the radiation chemistry of iodine there has been no consistent set of experiments spanning a wide enough range of conditions to verify models with confidence. This paper describes results from a set of experiments carried out in order to remedy this deficiency. In this work the rate of evolution of I{sub 2} from sparged irradiated CsI solution labeled with {sup 131}I was measured on-line over a range of conditions. This work involved the measurement of the effects of pH, temperature, O{sub 2} concentration, I{sup -} concentration, phosphate concentration, dose-rate and impurities on the rate of evolution of I{sub 2}. The range of conditions was chosen in order to span as closely as possible conditions expected in a LOCA but also to help to elucidate some of the mechanisms especially at high pH. pH was found to be a very important factor influencing iodine volatility, over the temperature range studied the extent of oxidation reduced with temperature but this was compensated for by the decrease in partition coefficient. Oxygen concentration was more important in solutions not containing phosphate. The fractional oxidation was not particularly dependent on iodide concentration but G{sub I2} was very dependent on [I{sup -}]. There was no effect of added impurities, Fe, Mn, Mo or organics although in separate work silver was found to have a very important effect. During attempts to interpret the data it was found that it was necessary to include the iodine atom as a volatile species with a partition coefficient of 1.9 taken from thermodynamic data. The modelling work is described in a separate paper. (author) 15 figs., 1 tab., 19 refs.

  8. Investigation of spectral distribution and variation of irradiance with the passage time of CSI lamps which constitute a solar simulator; Solar simulator ni shiyosuru CSI lamp no supekutoru bunpu, hosha shodo no keiji henka ni kansuru chosa

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, T.; Yamada, T.; Noguchi, T. [Japan Quality Assurance Organization, Tokyo (Japan)

    1997-11-25

    Study was made on time-variation of the performance of CSI lamps for solar simulators. In order to accurately evaluate the standard heat collection performance of solar systems in a room, MITI installed an artificial solar light source in the Solar Techno-Center of Japan Quality Assurance Organization for trial use and evaluation. CSI lamp is superior in durability, and can simulate the solar light in the daytime. The light source is composed of 72 metal halide lamps of 1kW arranged in a plane of 3.5times3.5m. The study result on time-variation of a spectral distribution and irradiance by intermittent switching of lamps showed a sufficient durability of 2000h. To ensure the accuracy of a solar heat collector measurement system enough, periodic calibration is being carried out using reference goods. To ensure the reliability and stability for a switching system, periodic maintenance of a power source, stabilizer and electric system is also being carried out in addition to CSI lamps. The stable irradiance and accuracy are being kept by such maintenance and periodic exchange of lamps. 6 figs., 4 tabs.

  9. Measurement of Trace $^{129}I$ Concentrations in CsI Powder and Organic Liquid Scintillator with Accelerator Mass Spectrometry

    CERN Document Server

    Dong, K J

    2007-01-01

    Levels of trace radiopurity in active detector materials is a subject of major concern in low-background experiments. Procedures were devised to measure trace concentrations of I-129 in the inorganic salt CsI as well as in organic liquid scintillator with Accelerator Mass Spectrometry (AMS) which leads to improvement in sensitivities by several orders of magnitude over other methods. No evidence of their existence in these materials were observed. Limits of < 6 X 10^{-13} g/g and < 2.6 X 10^{-17} g/g on the contaminations of I-129 in CsI and liquid scintillator, respectively, were derived.These are the first results in a research program whose goals are to develop techniques to measure trace radioactivity in detector materials by AMS.

  10. Impact of I/Q imbalance on the performance of two-way CSI-assisted AF relaying

    KAUST Repository

    Qi, Jian

    2013-04-01

    In this paper, we investigate half-duplex two-way dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying in the presence of in-phase and quadrature-phase (I/Q) imbalance. A compensation approach for the I/Q imbalance is proposed, which employs the received signals together with their conjugations to detect the desired signal. We also derive the average symbol error probability of the considered half-duplex two-way dual-hop CSI-assisted AF relaying networks with and without compensation for I/Q imbalance in Rayleigh fading channels. Numerical results are provided and show that the proposed compensation method mitigates the impact of I/Q imbalance to a certain extent. © 2013 IEEE.

  11. Adaptación del Inventario de Estrategias de Afrontamiento (CSI a la población penitenciaria de Mexico

    Directory of Open Access Journals (Sweden)

    Francisco Javier Rodríguez-Díaz

    2014-01-01

    Full Text Available El objetivo del estudio es adaptar el CSI - Inventario de Estrategias de Afrontamiento - al contexto penitenciario. La muestra - 261 penados, 97% varones (n=253 - del Sistema Postpenitenciario y Atención a Liberados (DSPAL del Estado Jalisco, México. Los instrumentos utilizados: Ficha Penitenciaria de Historia de Vida y el Inventario CSI. Los resultados refieren una estructura de primer orden casi idéntica a la obtenida para la población general, con niveles de consistencia interna satisfactorios, al mismo tiempo que la interpretación de segundo orden no confirma la estructura de segundo y tercer orden. Se discuten las implicaciones de los resultados para intervención penitenciaria.

  12. Microstructure and Thermal Properties of the GeS2-In2S3-CsI Glasses

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The homogeneous G eS2-In2 S3-Csl glassy samples were prepared by conventional melt-quenching method.When the molar ratio of In2 S3 to CsI remains 1, the non-crystalline region can extend to the composition 0.4 GeS2 - 0.3 In2 S3 - 0.3 CsI.And with the addition of CsI, the glass-forming ability of this serial glass reaches its maximum at the composition 0.8 GeS2 - 0.1 In2 S3 - 0.1 CsI.According to the Raman spectra, the microstructure of these glasses is mainly constituted by [ GeS4 ] and [ InS4-xIx]tetrahedra, which are interconnected by the bridging sulfur atoms; meanwhile, the ethane- liked structural units [ S3 Ge- GeS3 ] can be formed because of the lacking of sulfur; Cs+ ion, which is ndded from CsI, exists as the nearest neighbor of I-ion in the glassy network.

  13. PILA: Sub-Meter Localization Using CSI from Commodity Wi-Fi Devices

    Directory of Open Access Journals (Sweden)

    Zengshan Tian

    2016-10-01

    Full Text Available The aim of this paper is to present a new indoor localization approach by employing the Angle-of-arrival (AOA and Received Signal Strength (RSS measurements in Wi-Fi network. To achieve this goal, we first collect the Channel State Information (CSI by using the commodity Wi-Fi devices with our designed three antennas to estimate the AOA of Wi-Fi signal. Second, we propose a direct path identification algorithm to obtain the direct signal path for the sake of reducing the interference of multipath effect on the AOA estimation. Third, we construct a new objective function to solve the localization problem by integrating the AOA and RSS information. Although the localization problem is non-convex, we use the Second-order Cone Programming (SOCP relaxation approach to transform it into a convex problem. Finally, the effectiveness of our approach is verified based on the prototype implementation by using the commodity Wi-Fi devices. The experimental results show that our approach can achieve the median error 0.7 m in the actual indoor environment.

  14. Minimax robust relay selection based on uncertain long-term CSI

    KAUST Repository

    Nisar, Muhammad Danish

    2014-02-01

    Cooperative communications via multiple relay nodes is known to provide the benefits of increase diversity and coverage. Simultaneous transmission via multiple relays, however, requires strong coordination between nodes either in terms of slot-based transmission or distributed space-time (ST) code implementation. Dynamically selecting a single best relay out of multiple relays and then using it alone for cooperative transmission alleviates the need for this strong coordination while still reaping the benefits of increased diversity and coverage. In this paper, we consider the design of relay selection (RS) under an imperfect knowledge of long-term channel state information (CSI) at the relay nodes, and we pursue minimax optimization to arrive at a robust RS approach that promises the best guarantee on the worst-case end-to-end signal-to-noise ratio (SNR). We provide some intuitive examples and extensive simulation results, not only in terms of worst-case SNR performance but also in terms of average bit-error-rate (BER) performance, to demonstrate the benefits of the proposed minimax robust RS scheme. © 2013 IEEE.

  15. Delay analysis of a point-to-multipoint spectrum sharing network with CSI based power allocation

    KAUST Repository

    Khan, Fahd Ahmed

    2012-10-01

    In this paper, we analyse the delay performance of a point-to-multipoint cognitive radio network which is sharing the spectrum with a point-to-multipoint primary network. The channel is assumed to be independent but not identically distributed and has Nakagami-m fading. A constraint on the peak transmit power of the secondary user transmitter (SU-Tx) is also considered in addition to the peak interference power constraint. Based on the constraints, a power allocation scheme which requires knowledge of the instantaneous channel state information (CSI) of the interference links is derived. The SU-Tx is assumed to be equipped with a buffer and is modelled using the M/G/1 queueing model. Closed form expressions for the probability distribution function (PDF) and cumulative distribution function (CDF) of the packet transmission time is derived. Using the PDF, the expressions for the moments of transmission time are obtained. In addition, using the moments, the expressions for the performance measures such as the total average waiting time of packets and the average number of packets waiting in the buffer of the SU-Tx are also obtained. Numerical simulations corroborate the theoretical results. © 2012 IEEE.

  16. Understanding Light-Induced Degradation of c-Si Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sopori, B.; Basnyat, P.; Devayajanam, S.; Shet, S.; Mehta, V.; Binns, J.; Appel, J.

    2012-06-01

    We discuss results of our investigations toward understanding bulk and surface components of light-induced degradation (LID) in low-Fe c-Si solar cells. The bulk effects, arising from boron-oxygen defects, are determined by comparing degradation of cell parameters and their thermal recovery, with that of the minority-carrier lifetime (964;) in sister wafers. We found that the recovery of 964; in wafers takes a much longer annealing time compared to that of the cell. We also show that cells having SiN:H coating experience a surface degradation (ascribed to surface recombination). The surface LID is seen as an increase in the q/2kT component of the dark saturation current (J02). The surface LID does not recover fully upon annealing and is attributed to degradation of the SiN:H-Si interface. This behavior is also exhibited by mc-Si cells that have very low oxygen content and do not show any bulk degradation.

  17. A graded catalytic-protective layer for an efficient and stable water-splitting photocathode

    Science.gov (United States)

    Gu, Jing; Aguiar, Jeffery A.; Ferrere, Suzanne; Steirer, K. Xerxes; Yan, Yong; Xiao, Chuanxiao; Young, James L.; Al-Jassim, Mowafak; Neale, Nathan R.; Turner, John A.

    2017-01-01

    Achieving solar-to-hydrogen efficiencies above 15% is key for the commercial success of photoelectrochemical water-splitting devices. While tandem cells can reach those efficiencies, increasing the catalytic activity and long-term stability remains a significant challenge. Here we show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity (current density of 11 mA cm‑2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination) and stability (retention of 80% of initial photocurrent density over a 20 h durability test) for the hydrogen evolution reaction. Microscopy and spectroscopy reveal that annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2. Our findings demonstrate the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production.

  18. Next Generation High Brightness Electron Beams From Ultra-High Field Cryogenic Radiofrequency Photocathode Sources

    CERN Document Server

    Rosenzweig, J B; Dolgashev, V; Emma, C; Fukusawa, A; Li, R; Limborg, C; Maxson, J; Musumeci, P; Nause, A; Pakter, R; Pompili, R; Roussel, R; Spataro, B; Tantawi, S

    2016-01-01

    Recent studies of the performance of radio-frequency (RF) copper structures operated at cryogenic temperatures have shown a dramatic increase in the maximum surface electric field that may be reached. We propose to utilize this development to enable a new generation of photoinjectors operated at cryogenic temperatures that may attain, through enhancement of the launch field at the photocathode by a factor of four, well over an order of magnitude increase in peak electron beam brightness. We present detailed studies of the beam dynamics associated with such a system, concentrating on an emittance-compensated S-band photoinjector that may directly substitute that of the LCLS X-ray free-electron laser. We show in this case that the increase in brightness leads directly to a factor of two reduction in gain length, with attendant increase in X-ray radiative efficiency. Extreme low emittance scenarios obtained at low operating charge, appropriate for dramatically pushing performance limits of ultrafast electron dif...

  19. Design of a high repetition rate S-band photocathode gun

    Science.gov (United States)

    Han, Jang-Hui; Cox, Matthew; Huang, Houcheng; Pande, Shivaji

    2011-08-01

    Photocathode RF guns have been developed in many laboratories for generating high quality electron beams for free-electron lasers based on linear accelerators. Such guns can generate electron beams with an exceptionally high peak current as well as a small transverse emittance. Their applications have been recently expanded for ultrafast electron diffraction, coherent terahertz radiation, and X-ray or γ-ray radiation by Compton scattering. In this paper, we design an S-band normal-conducting gun with capabilities of high quality beam generation and high repetition rate operation. The RF design and thermal analysis of the gun cavity and coupler are introduced. Optimal position of the gun focusing solenoid for low emittance beam generation is found by performing particle tracking simulations. Then, the gun system is designed to be able to afford the optimal solenoid position. The cooling-water channel surrounding the gun cavity and coupler is designed and analyzed numerically. The pressure in the gun is simulated with a vacuum model containing the detailed inner structure of the gun. An injector for a free-electron laser application is designed by using this gun and the beam dynamics simulation is shown. A cold test with a prototype gun for confirmation of the RF design is reported.

  20. Experimental studies of emittance growth and energy spread in a photocathode RF gun

    CERN Document Server

    Yang, J; Okada, Y; Yorozu, M; Yanagida, T; Endo, A

    2002-01-01

    In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91+-0.28 pi mm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac.

  1. Deposition of Y thin films by nanosecond UV pulsed laser ablation for photocathode application

    Energy Technology Data Exchange (ETDEWEB)

    Lorusso, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Anni, M. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Caricato, A.P. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Perulli, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Taurino, A. [National Research Council, Institute for Microelectronics & Microsystems, 73100 Lecce (Italy); Perrone, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Istituto Nazionale di Fisica Nucleare-Lecce, 73100 Lecce (Italy); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy)

    2016-03-31

    In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed laser deposition technique. Ex-situ morphological, structural and optical characterisations of such films have been performed by scanning electron microscopy, X-ray diffractometry, atomic force microscopy and ellipsometry. Polycrystalline films with a thickness of 1.2 μm, homogenous with a root mean square roughness of about 2 nm, were obtained by optimised laser irradiation conditions. Despite the relatively high thickness, the films resulted very adherent to the substrates. The high quality of such thin films is important to the synthesis of metallic photocathodes based on Y thin film, which could be used as electron sources of high photoemission performance in radio-frequency guns. - Highlights: • Pulsed laser deposition of Yttrium thin films is investigated. • 1.2 μm thick films were deposited with very low RMS roughness. • The Y thin films were very adherent to the Si substrate • Optical characterisation showed a very high absorption coefficient for the films.

  2. Software Tools for the Analysis of the Photocathode Response of Photomultiplier Vacuum Tubes

    CERN Document Server

    Fabbri, R

    2013-01-01

    The central institute of electronics (ZEA-2) in the Forschungszentrum Juelich (FZJ) has developed a system to scan the response of the photocathode of photomultiplier tubes (PMT). The PMT sits tight on a supporting structure, while a blue light emitting diode is moved along its surface by two stepper motors, spanning both the x and y coordinates. All the system is located in a light-tight box made by wood. A graphical software was developed in-situ to perform the scan operations under different configurations (e.g., the step size of the scan and the number of measurements per point). During each point measurement the current output generated in the vacuum photomultiplier is processed in sequence by a pre-amplifier (mainly to convert the current signal into a voltage signal), an amplifier, and by an ADC module (typically a CAEN N957). The information of the measurement is saved in files at the end of the scan. Recently, software based on the CERN ROOT and on the Qt libraries was developed to help the user anal...

  3. Development of S-band photocathode RF guns at Tsinghua University

    Science.gov (United States)

    Zheng, Lianmin; Du, Yingchao; Zhang, Zhe; Qian, Houjun; Yan, Lixin; Shi, Jiaru; Zhang, Zhen; Zhou, Zheng; Wu, Xiaowei; Su, Xiaolu; Wang, Dong; Tian, Qili; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

    2016-10-01

    This study aims to explain the development of S-band photocathode RF guns at Tsinghua University, with especial attention on the progress of guns developed after 2011. Two types of RF guns were developed based on the BNL/SLAC/UCLA gun prior 2011. These guns have been operated as electron sources for Tsinghua Thomson scattering X-ray source (TTX), MeV ultrafast electron diffraction, and Shanghai deep ultraviolet FEL test facility. Based on our operation experiences and other gun modifications worldwide, numerous improvements have been proposed, and seven third-type guns have been designed and fabricated since 2011. Cold tests of all third-type guns have been completed, confirming a significantly improved quality factor and mode separation. The first third-type gun has been installed on TTX and operated for four years, demonstrating high gradient, low dark current, stable quantum efficiency, and small emittances. The optimal transverse emittance was εx = 0.56 mm mrad , εy = 0.66 mm mrad for 200 pC with a peak current of 25 A, and εx = 0.78 mm mrad , εy = 0.92 mm mrad for 500 pC with a peak current of 62.5 A under a 110 MV/m gun gradient.

  4. First demonstration of a free-electron laser driven by electrons from a laser irradiated photocathode

    Science.gov (United States)

    Curtin, Mark; Bennett, Glenn; Burke, Robert; Benson, Stephen; Madey, J. M. J.

    Results are reported from the first observation of a free-electron laser (FEL) driven by an electron beam from a laser-irradiated photocathode. The Rocketdyne/Stanford FEL achieved sustained oscillations lasting over three hours and driven by photoelectrons accelerated by the Stanford Mark III radio-frequency linac. A LaB6 cathode, irradiated by a tripled Nd:YAG mode-locked drive laser, is the source of the photoelectrons. The drive laser, operating at 95.2 MHz, is phase-locked to the 30th subharmonic of the S-band linac. Peak currents in excess of 125 amps are observed and delivered to the Rocketdyne two-meter undulator, which is operated as a stand-alone oscillator. The electron beam has an energy spread of 0.8 percent (FWHM) at 38.5 MeV and an emittance, at the undulator, comparable to that observed for thermionic operation of the electron source. Small signal gain in excess of 150 percent is observed. Preliminary estimates of the electron beam brightness deliverable to the undulator range from 3.5 to 5.0 x 10 to the 11 amps/sq m.

  5. Status of SPring-8 Photocathode Rf Gun for Future Light Sources

    CERN Document Server

    Tomizawa, H; Dewa, H; Hanaki, H; Kobayashi, T; Mizuno, A; Suzuki, S; Taniuchi, T; Yanagida, K

    2005-01-01

    We have been studying photocathode single-cell pillbox rf gun for future light sources since 1996. We achieved a rmaximum field gradient of 187 MV/m with chemical-etching processed cavity. We have been developed stable and highly qualified UV-laser source for the rf gun intensively last 3 years. The UV-laser pulse (10 Hz) energy is up to 850 uJ/pulse. The energy stability (rms) of laser has been improved down to 0.2~0.3 % at the fundamental and 0.7~1.3% at the third harmonic generation. This stability is held for two months continuously. In this improvement, we just passively stabilized the system in a humidity-controlled clean room. On the other hand, the ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from the rf gun. We prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. With a deformable mirror, we obtained an emittance of1.6

  6. Revealing the semiconductor–catalyst interface in buried platinum black silicon photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Anderson, Nicholas C.; Neale, Nathan R.

    2016-01-01

    Nanoporous 'black' silicon semiconductors interfaced with buried platinum nanoparticle catalysts have exhibited stable activity for photoelectrochemical hydrogen evolution even after months of exposure to ambient conditions. The mechanism behind this stability has not been explained in detail, but is thought to involve a Pt/Si interface free from SiOx layer that would adversely affect interfacial charge transfer kinetics. In this paper, we resolve the chemical composition and structure of buried Pt/Si interfaces in black silicon photocathodes from a micron to sub-nanometer level using aberration corrected analytical scanning transmission electron microscopy. Through a controlled electrodeposition of copper on samples aged for one month in ambient conditions, we demonstrate that the main active catalytic sites are the buried Pt nanoparticles located below the 400-800 nm thick nanoporous SiOx layer. Though hydrogen production performance degrades over 100 h under photoelectrochemical operating conditions, this burying strategy preserves an atomically clean catalyst/Si interface free of oxide or other phases under air exposure and provides an example of a potential method for stabilizing silicon photoelectrodes from oxidative degradation in photoelectrochemical applications.

  7. A graded catalytic–protective layer for an efficient and stable water-splitting photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Jing; Aguiar, Jeffery A.; Ferrere, Suzanne; Steirer, K. Xerxes; Yan, Yong; Xiao, Chuanxiao; Young, James L.; Al-Jassim, Mowafak; Neale, Nathan R.; Turner, John A.

    2017-01-09

    Achieving solar-to-hydrogen efficiencies above 15% is key for the commercial success of photoelectrochemical water splitting devices. While tandem cells can reach those efficiencies, increasing the catalytic activity and long-term stability remains a significant challenge. Here we show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity (current density of 11 mA/cm2 at 0 V vs. the reversible hydrogen electrode under 1 sun illumination) and stability (retention of 80% of initial photocurrent density over a 20 h durability test) for the hydrogen evolution reaction. Microscopy and spectroscopy reveal that annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2. Our findings demonstrate the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production.

  8. Plasmon-enhanced photocathode for high brightness and high repetition rate x-ray sources

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, Aleksandr; Senft, Christoph; Thompson, K. F.; Feng, J.; Cabrini, S.; Schuck, P. J.; Padmore, Howard; Peppernick, Samuel J.; Hess, Wayne P.

    2013-02-11

    High brightness electron sources are at the heart of anew generation of x-ray sources based on the Free ElectronLaser (FEL) as well as in Energy Recovery Linac (ERL) and Inverse Compton Scattering (ICS) sources.The source of electrons consists of a photoinjector, comprised of a laser-driven photocathode in a high gradient electric field produced by an rf cavity. The function of the rf cavity is to provide a field sufficient for acceleration of electrons to relativistic velocity over a small distance, thus minimizing effects of the space-charge. Even so, the dense electron beam required for high brightness suffers from a space charge field that chirps and reshapes the electron pulse increasing beam emittance and thus reducing the overall brightness. This emittance growth can be avoided if the initial distribution of electrons is pancake shaped, with a semicircular transverse intensity profile. In this case, the electron distribution develops under its space charge field from a pancake into a uniformly filled ellipsoidal beam. This condition, referred to as the blowout regime, requires ultrashort pulses less than 100 fs long and has been successfully demonstrated recently in a high gradient photoinjector.

  9. Protected, back-illuminated silicon photocathodes or photoanodes for water splitting tandem stacks (Conference Presentation)

    Science.gov (United States)

    Vesborg, Peter C.; Bae, Dowon; Seger, Brian J.; Chorkendorff, Ib; Hansen, Ole; Pedersen, Thomas; Mei, Bastian; Frydendal, Rasmus

    2016-10-01

    Silicon is a promising contender in the race for low-bandgap absorbers for use in a solar driven monolithic water splitting cell (PEC). However, given its role as the low-bandgap material the silicon must sit behind the corresponding high-bandgap material and as such, it will be exposed to (red) light from the dry back-side - not from the wet front side, where the electrochemistry takes place.[1,2] Depending on the configuration of the selective contacts (junctions) this may lead to compromises between high absorption and low recombination.[2,3] We discuss the tradeoffs and compare modeling results to measurements. Regardless of configuration, the wet surface of the silicon is prone to passivation or corrosion and must therefore be carefully protected in service in order to remain active. We demonstrate the use of TiO2 as an effective protection layer for both photoanodes and photocathodes in acid electrolyte [4] and NiCoOx for photoanodes in alkaline electrolyte. [3] References: [1]: B. Seger et alia, Energ. Environ. Sci., 7 (8), 2397-2413 (2014), DOI:10.1039/c4ee01335b [2]: D. Bae et alia, Energ. Environ. Sci., 8 (2), 650-660 (2015), DOI: 10.1039/c4ee03723e [3]: D. Bae et alia, submitted, (2016) [4]: B. Mei et alia, J. Phys. Chem. C., 119 (27), 15019-15027 (2015), DOI: 10.1021/acs.jpcc.5b04407

  10. 新一代先进光源和新型光阴级材料的特性及应用研究%Characteristics and Applications of Advanced Light Source and Novel Photocathode

    Institute of Scientific and Technical Information of China (English)

    冯军

    2011-01-01

    2010 is the 50th anniversary of the invention of laser. I will describe the evolution of laser, synchrotron radiation light and new generation light source-free electron laser (also called x-ray laser). Novel photocathode is identified as a key area of research needed to meet the challenge of next generation light sources, where in particular, it operates at very high repetition rate and low emittance. One front field of scientific research in the world is to study the ultra-fast and ultra-small world. The combination of high brightness and ultra-fast pulse of x-ray laser with ultra-fast detector will make important contributions to the ultrafast dynamic study of the ultra-small world. The work function, vectorial photoelectric effect and angle resolved photoemission of single-crystal surface of typically used metallic photocathode and multi-alkali photocathode will be reported. The ultra-fast dynamics of magnetism material Fe/Gd and the warm-dense-matter generated by focusing a fs laser on Cu will also be reported.%介绍了从激光光源到同步辐射光源及自由电子激光光源的发展及特性,及所需新型光阴级材料的特性。当代科学研究的前沿之一是研究微观世界的动态特征,这就需要同时具有纳米的空间分辨和飞秒的时间分辨。X射线激光的超快特性和高亮度,结合超快探测器条纹相机的高时间分辨和空间分辨,将十分有助于微观世界的动态特挫研究。报告了对单晶体Cu(100)和Cu(lll)金属光阴级材料和半导体复合光阴级材料研究所取得的成果,以及对磁性材料Fe/Gd和用飞秒激光在Cu中产生的高热高密度物质的动力学研究。

  11. Emitter formation using laser doping technique on n- and p-type c-Si substrates

    Science.gov (United States)

    López, G.; Ortega, P.; Colina, M.; Voz, C.; Martín, I.; Morales-Vilches, A.; Orpella, A.; Alcubilla, R.

    2015-05-01

    In this work laser doping technique is used to create highly-doped regions defined in a point-like structure to form n+/p and p+/n junctions applying a pulsed Nd-YAG 1064 nm laser in the nanosecond regime. In particular, phosphorous-doped silicon carbide stacks (a-SiCx/a-Si:H (n-type)) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and aluminum oxide (Al2O3) layers deposited by atomic layer deposition (ALD) on 2 ± 0.5 Ω cm p- and n-type FZ c-Si substrates respectively are used as dopant sources. Laser power and number of pulses per spot are explored to obtain the optimal electrical behavior of the formed junctions. To assess the quality of the p+ and n+ regions, the junctions are electrically contacted and characterized by means of dark J-V measurements. Additionally, a diluted HF treatment previous to front metallization has been explored in order to know its impact on the junction quality. The results show that fine tuning of the energy pulse is critical while the number of pulses has minor effect. In general the different HF treatments have no impact in the diode electrical behavior except for an increase of the leakage current in n+/p junctions. The high electrical quality of the junctions makes laser doping, using dielectric layers as dopant source, suitable for solar cell applications. Particularly, a potential open circuit voltage of 0.64 V (1 sun) is expected for a finished solar cell.

  12. Low temperature characteristic of ITO/SiO x /c-Si heterojunction solar cell

    Science.gov (United States)

    Du, H. W.; Yang, J.; Li, Y.; Gao, M.; Chen, S. M.; Yu, Z. S.; Xu, F.; Ma, Z. Q.

    2015-09-01

    Based on the temperature-dependent measurements and the numerical calculation, the temperature response of the photovoltaic parameters for a ITO/SiO x /c-Si heterojunction solar cell have been investigated in the ascending sorting of 10-300 K. Under unique energy concentrated photon irradiation with the wavelength of 405 nm and power density of 667 mW cm-2, it was found that the short-circuit current (I SC) was nonlinearly increased and the open-circuit voltage (V OC) decreased with temperature. The good passivation of the ITO/c-Si interface by a concomitant SiO x buffer layer leads to the rare recombination of carriers in the intermediate region. The inversion layer model indicated that the band gap of c-silicon was narrowed and the Fermi level of n-type silicon (E\\text{F}n ) tended to that of the intrinsic Fermi level (E\\text{F}i ) (in the middle of band gap) with the increase of the temperature, which lessened the built-in voltage (V D) and thus the V OC. However, the reduction by 90% of V OC is attributed to the shift of E\\text{F}n in c-silicon rather than the energy band narrowing. Through the analysis of the current-voltage relationship and the data fitting, we infer that the series resistance (R s) is not responsible for the increase of I SC, but the absorption coefficient and the depletion-width of c-silicon are the causes of the enhancing I SC. Mostly, the interaction of the photon-generated excess ‘cold hole’ and the acoustic phonon in n-Si would influence the variation of I ph or I SC with temperature.

  13. Modulating the field-effect passivation at the SiO2/c-Si interface: Analysis and verification of the photoluminescence imaging under applied bias method

    Science.gov (United States)

    Haug, Halvard; Olibet, Sara; Nordseth, Ørnulf; Stensrud Marstein, Erik

    2013-11-01

    In this paper, we study the surface passivation properties of thermally oxidized silicon wafers with controlled surface band bending, using a recently developed characterization technique combining calibrated photoluminescence imaging with the application of an external voltage over the rear side passivation layer. Various aspects of the technique and possible errors in the determination of the effective surface recombination velocity are discussed, including lateral carrier diffusion, leakage currents, and optical effects related to the presence of metal electrodes on the investigated samples. In order to quantitatively describe the recombination activity at the SiO2/c-Si interface and the effect of fixed charges in the oxide layer, the measured effective carrier lifetime vs. voltage curves have been analyzed in the framework of an extended Shockley-Read Hall recombination model. Furthermore, the results have been compared with corresponding results from microwave detected photoconductance decay measurements after depositing corona charges. We find an excellent agreement between the two techniques and between complementary measurements of the oxide charge density. Photoluminescence imaging under applied bias gives fast and repeatable measurements and allows for simultaneous data collection from multiple areas on the sample, and has thus been proven to be powerful tool for quantitative characterization of surface passivation layers.

  14. Experimental measurements and theoretical model of the cryogenic performance of bialkali photocathode and characterization with Monte Carlo simulation

    Science.gov (United States)

    Xie, Huamu; Ben-Zvi, Ilan; Rao, Triveni; Xin, Tianmu; Wang, Erdong

    2016-10-01

    High-average-current, high-brightness electron sources have important applications, such as in high-repetition-rate free-electron lasers, or in the electron cooling of hadrons. Bialkali photocathodes are promising high-quantum-efficiency (QE) cathode materials, while superconducting rf (SRF) electron guns offer continuous-mode operation at high acceleration, as is needed for high-brightness electron sources. Thus, we must have a comprehensive understanding of the performance of bialkali photocathode at cryogenic temperatures when they are to be used in SRF guns. To remove the heat produced by the radio-frequency field in these guns, the cathode should be cooled to cryogenic temperatures. We recorded an 80% reduction of the QE upon cooling the K2CsSb cathode from room temperature down to the temperature of liquid nitrogen in Brookhaven National Laboratory (BNL)'s 704 MHz SRF gun. We conducted several experiments to identify the underlying mechanism in this reduction. The change in the spectral response of the bialkali photocathode, when cooled from room temperature (300 K) to 166 K, suggests that a change in the ionization energy (defined as the energy gap from the top of the valence band to vacuum level) is the main reason for this reduction. We developed an analytical model of the process, based on Spicer's three-step model. The change in ionization energy, with falling temperature, gives a simplified description of the QE's temperature dependence. We also developed a 2D Monte Carlo code to simulate photoemission that accounts for the wavelength-dependent photon absorption in the first step, the scattering and diffusion in the second step, and the momentum conservation in the emission step. From this simulation, we established a correlation between ionization energy and reduction in the QE. The simulation yielded results comparable to those from the analytical model. The simulation offers us additional capabilities such as calculation of the intrinsic emittance

  15. Highly stable copper oxide composite as an effective photocathode for water splitting via a facile electrochemical synthesis strategy

    KAUST Repository

    Zhang, Zhonghai

    2012-01-01

    Hydrogen generation through photoelectrochemical (PEC) water splitting using solar light as an energy resource is believed to be a clean and efficient way to overcome the global energy and environmental problems. Extensive research effort has been focused on n-type metal oxide semiconductors as photoanodes, whereas studies of p-type metal oxide semiconductors as photocathodes where hydrogen is generated are scarce. In this paper, highly efficient and stable copper oxide composite photocathode materials were successfully fabricated by a facile two-step electrochemical strategy, which consists of electrodeposition of a Cu film on an ITO glass substrate followed by anodization of the Cu film under a suitable current density and then calcination to form a Cu 2O/CuO composite. The synthesized Cu 2O/CuO composite was composed of a thin layer of Cu 2O with a thin film of CuO on its top as a protecting coating. The rational control of chemical composition and crystalline orientation of the composite materials was easily achieved by varying the electrochemical parameters, including electrodeposition potential and anodization current density, to achieve an enhanced PEC performance. The best photocathode material among all materials prepared was the Cu 2O/CuO composite with Cu 2O in (220) orientation, which showed a highly stable photocurrent of -1.54 mA cm -2 at a potential of 0 V vs reversible hydrogen electrode at a mild pH under illumination of AM 1.5G. This photocurrent density was more than 2 times that generated by the bare Cu 2O electrode (-0.65 mAcm -2) and the stability was considerably enhanced to 74.4% from 30.1% on the bare Cu 2O electrode. The results of this study showed that the top layer of CuO in the Cu 2O/CuO composite not only minimized the Cu 2O photocorrosion but also served as a recombination inhibitor for the photogenerated electrons and holes from Cu 2O, which collectively explained much enhanced stability and PEC activity of the Cu 2O/CuO composite

  16. Si microstructures laminated with a nanolayer of TiO2 as long-term stable and effective photocathodes in PEC devices.

    Science.gov (United States)

    Das, Chittaranjan; Tallarida, Massimo; Schmeisser, Dieter

    2015-05-07

    Photoelectrochemical (PEC) water splitting is one of the most emerging fields for green energy generation and storage. Here we show a study of microstructured Si covered by a TiO2 nano-layer. The microstructures are prepared by galvanostatic selective etching of Si. The TiO2 nano-layer was deposited by atomic layer deposition (ALD) to protect the microstructured photocathode against corrosion. The obtained microstructured photocathode showed a shift in the onset potential of 400 mV towards the anodic direction compared to bare Si. The Si microstructures laminated with a nano-layer of TiO2 show stability over 60 hours of measurement.

  17. Observation and Measurement of Temperature Rise and Distribution on GaAs Photo-cathode Wafer with a 532nm Drive Laser and a Thermal Imaging Camera

    Energy Technology Data Exchange (ETDEWEB)

    Shukui Zhang, Stephen Benson, Carlos Hernandez-Garcia

    2011-03-01

    Significant temperature rise and gradient are observed from a GaAs photo-cathode wafer irradiated at various power levels with over 20W laser power at 532nm wavelength. The laser power absorption and dissipated thermal distribution are measured. The result shows a clear indication that proper removal of laser induced heat from the cathode needs to be considered seriously when designing a high average current or low quantum efficiency photo-cathode electron gun. The measurement method presented here provides a useful way to obtain information about both temperature and thermal profiles, it also applies to cathode heating study with other heating devices such as electrical heaters.

  18. Si microstructures laminated with a nanolayer of TiO2 as long-term stable and effective photocathodes in PEC devices

    Science.gov (United States)

    Das, Chittaranjan; Tallarida, Massimo; Schmeisser, Dieter

    2015-04-01

    Photoelectrochemical (PEC) water splitting is one of the most emerging fields for green energy generation and storage. Here we show a study of microstructured Si covered by a TiO2 nano-layer. The microstructures are prepared by galvanostatic selective etching of Si. The TiO2 nano-layer was deposited by atomic layer deposition (ALD) to protect the microstructured photocathode against corrosion. The obtained microstructured photocathode showed a shift in the onset potential of 400 mV towards the anodic direction compared to bare Si. The Si microstructures laminated with a nano-layer of TiO2 show stability over 60 hours of measurement.

  19. Investigating Water Splitting with CaFe2O4 Photocathodes by Electrochemical Impedance Spectroscopy.

    Science.gov (United States)

    Díez-García, María Isabel; Gómez, Roberto

    2016-08-24

    Artificial photosynthesis constitutes one of the most promising alternatives for harvesting solar energy in the form of fuels, such as hydrogen. Among the different devices that could be developed to achieve efficient water photosplitting, tandem photoelectrochemical cells show more flexibility and offer high theoretical conversion efficiency. The development of these cells depends on finding efficient and stable photoanodes and, particularly, photocathodes, which requires having reliable information on the mechanism of charge transfer at the semiconductor/solution interface. In this context, this work deals with the preparation of thin film calcium ferrite electrodes and their photoelectrochemical characterization for hydrogen generation by means of electrochemical impedance spectroscopy (EIS). A fully theoretical model that includes elementary steps for electron transfer to the electrolyte and surface recombination with photogenerated holes is presented. The model also takes into account the complexity of the semiconductor/solution interface by including the capacitances of the space charge region, the surface states and the Helmholtz layer (as a constant phase element). After illustrating the predicted Nyquist plots in a general manner, the experimental results for calcium ferrite electrodes at different applied potentials and under different illumination intensities are fitted to the model. The excellent agreement between the model and the experimental results is illustrated by the simultaneous fit of both Nyquist and Bode plots. The concordance between both theory and experiments allows us to conclude that a direct transfer of electrons from the conduction band to water prevails for hydrogen photogeneration on calcium ferrite electrodes and that most of the carrier recombination occurs in the material bulk. In more general vein, this study illustrates how the use of EIS may provide important clues about the behavior of photoelectrodes and the main strategies

  20. SU-E-I-11: Cascaded Linear System Model for Columnar CsI Flat Panel Imagers with Depth Dependent Gain and Blur

    Energy Technology Data Exchange (ETDEWEB)

    Peng, B; Lubinsky, A; Zheng, H; Zhao, W [Stony Brook University, Stony Brook, NY (United States); Teymurazyan, A [Lakehead University, Thunder Bay, Ontario (Canada)

    2014-06-01

    Purpose: To implement a depth dependent gain and blur cascaded linear system model (CLSM) for optimizing columnar structured CsI indirect conversion flat panel imager (FPI) for advanced imaging applications. Methods: For experimental validation, depth dependent escape efficiency, e(z), was extracted from PHS measurement of different CsI scintillators (thickness, substrate and light output). The inherent MTF and DQE of CsI was measured using high resolution CMOS sensor. For CLSM, e(z) and the depth dependent MTF(f,z), were estimated using Monte Carlo simulation (Geant4) of optical photon transport through columnar CsI. Previous work showed that Monte Carlo simulation for CsI was hindered by the non-ideality of its columnar structure. In the present work we allowed variation in columnar width with depth, and assumed diffusive reflective backing and columns. Monte Carlo simulation was performed using an optical point source placed at different depth of the CsI layer, from which MTF(z,f) and e(z) were computed. The resulting e(z) with excellent matching with experimental measurements were then applied to the CLSM, Monte Carlo simulation was repeated until the modeled MTF, DQE(f) also match experimental measurement. Results: For a 150 micron FOS HL type CsI, e(z) varies between 0.56 to 0.45, and the MTF at 14 cycles/mm varies between 62.1% to 3.9%, from the front to the back of the scintillator. The overall MTF and DQE(f) at all frequencies are in excellent agreement with experimental measurements at all frequencies. Conclusion: We have developed a CLSM for columnar CsI scintillators with depth dependent gain and MTF, which were estimated from Monte Carlo simulation with novel optical simulation settings. Preliminary results showed excellent agreement between simulation results and experimental measurements. Future work is aimed at extending this approach to optimize CsI screen optic design and sensor structure for achieving higher DQE(f) in cone-beam CT, which uses

  1. Study of pure and Pb{sup 2+} ions doped CsI crystals under alpha particles excitations

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Maria da Conceicao Costa; Madi Filho, Tufic; Hamada, Margarida Mizue, E-mail: macoper@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Scintillation crystals have been used in various fields, such as high energy physics, nuclear instrumentation, radiation measurements, medical imaging, nuclear tomography, astrophysics and other fields of science and engineering. For these applications, the development of good performance scintillation crystals is required. Scintillation crystals based on cesium iodide (CsI) matrix are matters with relatively low hygroscope, easy handling and low cost, characteristics that favor their use as radiation detectors. In this work, pure CsI crystal and lead doped CsI crystals were grown using the Bridgman vertical technique. The concentration of the lead doping element (Pb) was studied in the range of 10{sup -2} M to 5x10{sup -4} M. The distribution of the doping element in the crystalline volume was determined by flame atomic absorption. The CsI:Pb crystal with nominal concentration of 10{sup -3} M was cut into 14 slices of 6 mm. The results show a higher concentration at the top of the crystal with a decrease in the initial phase of growth. The dopant concentration of Pb showed good uniformity from the slice 2 to the slice 12: the region is, therefore, suitable for use as radiation detector. The luminescence emission of these crystals were measured. A predominant luminescence band near 450 nm and a single broad band around 320 nm were found with the addition of the Pb{sup 2+} ions. Analyses were carried out to evaluate the developed scintillators, concerning alpha particles. The resolution of 5.6% was obtained for the CsI:Pb 5x10{sup -4} M crystal, when excited with alpha particles from a {sup 241}Am source, with energy of 5.54 MeV. (author)

  2. Scintillation light simulation in big-sized BaF$_{2}$ and pure CsI crystals

    CERN Document Server

    Usubov, Zafar

    2016-01-01

    We have investigated scintillation light distribution in BaF$_{2}$ and pure CsI crystals with dimensions 3x3x20 cm$^{3}$ using the Geant4 toolkit. The diffuse wrapping material is selected as coating for the crystals. The simulated cosmic muons and 105 MeV electrons are used as beam particles. The optical attenuation along the crystals is explored with the simulation data. We have demonstrated the impact of the crystal surface finish on the light distribution at the crystal end, optical photon arrival time, incidence angle distributions, and optical attenuation for the studied crystals.

  3. Efficient and Stable MoS2 /CdSe/NiO Photocathode for Photoelectrochemical Hydrogen Generation from Water.

    Science.gov (United States)

    Dong, Yuming; Chen, Yanmei; Jiang, Pingping; Wang, Guangli; Wu, Xiuming; Wu, Ruixian; Zhang, Chi

    2015-08-01

    A novel CdSe/NiO heteroarchitecture was designed, prepared, and used as a photocathode for hydrogen generation from water. The composite films were structurally, optically, and photoelectrochemically characterized. The deposition of CdSe on the NiO film enhanced light harvesting in the visible-light region and photoelectrochemical properties. Moreover, the CdSe/NiO photoelectrode showed superior stability both in nitrogen-saturated and air-saturated neutral environments. The CdSe/NiO photoelectrode after MoS2 modification retained the stability of the CdSe/NiO electrode and exhibited higher photocatalytic and photoelectrochemical performances than the unmodified CdSe/NiO electrode. In pH 6 buffer solution, an average hydrogen-evolution rate of 0.52 μmol h(-1)  cm(-2) at -0.131 V (versus reversible hydrogen electrode, RHE) was achieved on a MoS2 /CdSe/NiO photocathode, with almost 100 % faradaic efficiency.

  4. Surface passivation and protection of Pt loaded multicrystalline pn+ silicon photocathodes by atmospheric plasma oxidation for improved solar water splitting

    Science.gov (United States)

    Fan, Ronglei; Tang, Chengshuang; Xin, Yu; Su, Xiaodong; Wang, Xiaodong; Shen, Mingrong

    2016-12-01

    In the traditional methods such as atomic layer deposition and sputtering, a thin metal oxide layer was usually deposited before the loading of catalysts to protect Si photoelectrodes from oxidation during solar water splitting, and this often results in the transfer of photogenerated carriers from Si to electrolyte more or less inhibited. We here use an atmospheric plasma oxidation method to improve this. A SiO2 protective layer, also an effective passivation layer of Si to increase the life time of carriers, is fabricated on Pt loaded multicrystalline pn+-Si photocathodes. Compared with the un-protected one, the energy conversion efficiency of the plasma-treated Pt/pn+-Si photocathode increases from 6.2% to 8.9% under 100 mW/cm2 Xe lamp, and its stability improves from less than 1-22 h under continuous H2 production. This research provides a conceptual strategy to ensure the direct contact among the Si/Pt/electrolyte and protect and passivate the other part of Si simultaneously.

  5. Engineering of Sub-Nanometer SiOx Thickness in Si Photocathodes for Optimized Open Circuit Potential.

    Science.gov (United States)

    Das, Chittaranjan; Kot, Malgorzata; Henkel, Karsten; Schmeisser, Dieter

    2016-09-01

    Silicon is one of the most promising materials to be used for tandem-cell water-splitting devices. However, the electrochemical instability of bare Si makes it difficult to be used for stable devices. Besides that, the photovoltage loss in Si, caused by several factors (e.g., metal oxide protection layer and/or SiO2 /Si or catalyst/Si interface), limits its use in these devices. In this work, we present that an optimized open circuit potential (OCP) of Si can be obtained by controlling the SiOx thickness in sub-nanometer range. It can be done by means of a simple and cost-effective way using the combination of a wet chemical etching and the low temperature atomic layer deposition (ALD) of TiO2 . We have found that a certain thickness of the native SiOx is necessary to prevent further oxidation of the Si photocathode during the ALD growth of TiO2 . Moreover, covering the Si photocathode with an ALD TiO2 layer enhances its stability.

  6. Distribution of carriers in gradient-doping transmission-mode GaAs photocathodes grown by molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Jun; Chang Ben-Kang; Yang Zhi; Niu Jun; Zou Ji-Jun

    2009-01-01

    The gradient-doping structure is first applied to prepare the transmission-mode OaAs photocathode and the integral sensitivity of the sealed image tube achieves 1420μA/lm. This paper studies the inner carrier concentration distribution of the gradient-doping transmission-mode GaAs photocathode after molecular beam epitaxy (MBE) growth using the electrochemical capacitance-voltage profiling. The results show that an ideal gradient-doping structure can be obtained by using MBE growth. The total band-bending energy in the gradient-doping GaAs active-layer with doping concentration ranging from 1×10~(19) cm~(-3) to 1×10~(18) cm~(-3) is calculated to be 46.3 meV, which helps to improve the photoexcited electrons movement toward surface for the thin epilayer. In addition, by analysis of the band offsets, it is found that the worse carrier concentration discrepancy between GaAs and GaAlAs causes a lower back interface electron potential barrier which decreases the amount of high-energy photoelectrons and affects the short-wave response.

  7. DISCOVERY OF SiCSi IN IRC+10216: A MISSING LINK BETWEEN GAS AND DUST CARRIERS OF Si–C BONDS

    Energy Technology Data Exchange (ETDEWEB)

    Cernicharo, J.; Agúndez, M.; Prieto, L. Velilla; Quintana-Lacaci, G. [Group of Molecular Astrophysics, ICMM, CSIC, C/Sor Juana Inés de La Cruz N3, E-28049, Madrid (Spain); McCarthy, M. C.; Gottlieb, C. A.; Drumel, M. A. Martin-; Patel, N. A.; Reilly, N. J.; Young, K. H. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Baraban, J. H. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 (United States); Changala, P. B. [JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Guélin, M. [Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406 St-Martin d’Hères (France); Kahane, C. [Universit Grenoble Alpes, IPAG, F-38000 Grenoble (France); CNRS, IPAG, F-38000 Grenoble (France); Stanton, J. F. [Institute for Theoretical Chemistry, Department of Chemistry, The University of Texas at Austin, Austin, TX 78712 (United States); Thorwirth, S. [I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany)

    2015-06-10

    We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30 m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emission arises from a region of 6″ in radius. The derived abundance is comparable to that of SiC{sub 2}. As expected from chemical equilibrium calculations, SiCSi and SiC{sub 2} are the most abundant species harboring a Si−C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.

  8. Discovery of SiCSi in IRC +10216: A missing link between gas and dust carriers of Si–C bonds

    Science.gov (United States)

    Cernicharo, J.; McCarthy, M. C.; Gottlieb, C. A.; Agúndez, M.; Velilla Prieto, L.; Baraban, J. H.; Changala, P. B.; Guélin, M.; Kahane, C.; Martin-Drumel, M. A.; Patel, N. A.; Reilly, N. J.; Stanton, J. F.; Quintana-Lacaci, G.; Thorwirth, S.; Young, K. H.

    2015-01-01

    We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM10 30m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array11, the bulk of the SiCSi emission arises from a region of 6″ in radius. The derived abundance is comparable to that of SiC2. As expected from chemical equilibrium calculations, SiCSi and SiC2 are the most abundant species harboring a Si–C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains. PMID:26722621

  9. Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of SiC bonds

    CERN Document Server

    Cernicharo, J; Gottlieb, C A; Agundez, M; Prieto, L Velilla; Baraban, J H; Changala, P B; Guelin, M; Kahane, C; Martin-Drumel, M A; Patel, N A; Reilly, N J; Stanton, J F; Quintana-Lacaci, G; Thorwirth, S; Young, K H

    2015-01-01

    We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CWLeo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emis- sion arises from a region of 6 arcseconds in radius. The derived abundance is comparable to that of SiC2. As expected from chemical equilibrium calculations, SiCSi and SiC2 are the most abundant species harboring a SiC bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.

  10. Characterization of capsaicin synthase and identification of its gene (csy1) for pungency factor capsaicin in pepper (Capsicum sp.).

    Science.gov (United States)

    Prasad, B C Narasimha; Kumar, Vinod; Gururaj, H B; Parimalan, R; Giridhar, P; Ravishankar, G A

    2006-09-05

    Capsaicin is a unique alkaloid of the plant kingdom restricted to the genus Capsicum. Capsaicin is the pungency factor, a bioactive molecule of food and of medicinal importance. Capsaicin is useful as a counterirritant, antiarthritic, analgesic, antioxidant, and anticancer agent. Capsaicin biosynthesis involves condensation of vanillylamine and 8-methyl nonenoic acid, brought about by capsaicin synthase (CS). We found that CS activity correlated with genotype-specific capsaicin levels. We purified and characterized CS ( approximately 35 kDa). Immunolocalization studies confirmed that CS is specifically localized to the placental tissues of Capsicum fruits. Western blot analysis revealed concomitant enhancement of CS levels and capsaicin accumulation during fruit development. We determined the N-terminal amino acid sequence of purified CS, cloned the CS gene (csy1) and sequenced full-length cDNA (981 bp). The deduced amino acid sequence of CS from full-length cDNA was 38 kDa. Functionality of csy1 through heterologous expression in recombinant Escherichia coli was also demonstrated. Here we report the gene responsible for capsaicin biosynthesis, which is unique to Capsicum spp. With this information on the CS gene, speculation on the gene for pungency is unequivocally resolved. Our findings have implications in the regulation of capsaicin levels in Capsicum genotypes.

  11. Visible-light responsive photocatalytic fuel cell based on WO(3)/W photoanode and Cu(2)O/Cu photocathode for simultaneous wastewater treatment and electricity generation.

    Science.gov (United States)

    Chen, Quanpeng; Li, Jinhua; Li, Xuejin; Huang, Ke; Zhou, Baoxue; Cai, Weimin; Shangguan, Wenfeng

    2012-10-16

    A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO(3)/W photoanode and Cu(2)O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO(3)/W photoanode is higher than that of Cu(2)O/Cu photocathode. An interior bias can be produced based on which the electrons of WO(3)/W photoanode can transfer from the external circuit to combine with the holes of Cu(2)O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO(3)/W photoanode and electrons of Cu(2)O/Cu photocathode. Organic compounds can be decomposed by the holes of WO(3)/W photoanode due to its high oxidation power (+3.1-3.2 V(NHE)). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.

  12. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    Energy Technology Data Exchange (ETDEWEB)

    Gregory A. Mulhollan

    2010-11-16

    Specific activation recipes for bulk, 100 nm thick MBE grown and high polarization III-V photocathode material have been developed which mitigate the effects of exposure to background gasses. Lifetime data using four representative gasses were acquired for bulk GaAs, 100 nm unstrained GaAs and strained superlattice GaAs/GaAsP, all activated both with Cs and then Cs and Li (bi-alkali). Each photoemitter showed marked resilience improvement when activated using the bi-alkali recipe compared to the standard single alkali recipe. A dual alkali activation system at SLAC was constructed, baked and commissioned with the purpose of performing spin-polarization measurements on electrons emitted from the bi-alkali activated surfaces. An end station at SSRL was configured with the required sources for energy resolved photoemission measurements on the bi-alkali activated and CO2 dosed surfaces. The bi-alkali recipes were successfully implemented at SLAC/SSRL. Measurements at SLAC of the photoelectron spin-polarization from the modified activation surface showed no sign of a change in value compared to the standard activated material, i.e., no ill effects. Analysis of photoemission data indicates that the addition of Li to the activation layer results in a multi-layer structure. The presence of Li in the activation layer also acts as an inhibitor to CO2 absorption, hence better lifetimes in worse vacuum were achieved. The bi-alkali activation has been tested on O2 activated GaAs for comparison with NF3 activated surfaces. Comparable resilience to CO2 exposure was achieved for the O2 activated surface. An RF PECVD amorphous silicon growth system was modified to allow high temperature heat cleaning of GaAs substrates prior to film deposition. Growth versus thickness data were collected. Very thin amorphous silicon germanium layers were optimized to exhibit good behavior as an electron emitter. Growth of the amorphous silicon germanium films on the above substrates was fine tuned

  13. Spectroscopic imaging of the human liver using 3D CSI. Optimization and application in patients with metastatic uvea melanoma; Spektroskopische Bildgebung der menschlichen Leber mittels 3D-CSI. Etablierung und Anwendung bei Patienten mit metastasiertem Aderhautmelanom

    Energy Technology Data Exchange (ETDEWEB)

    Beer, M.; Winkelmann, V.; Stenzel, M.; Hahn, D.; Koestler, H. [Universitaetsklinikum Wuerzburg (Germany). Inst. fuer Roentgendiagnostik; Becker, J.C.; Broecker, E.B. [Universitaetsklinikum Wuerzburg (Germany). Klinik fuer Dermatologie, Venerologie und Allergologie; Terheyden, P. [Universitaetsklinikum Wuerzburg (Germany). Klinik fuer Dermatologie, Venerologie und Allergologie; Universitaetsklinikum Schleswig-Holstein, Kiel (Germany). Klinik fuer Dermatologie, Allergologie und Venerologie

    2009-01-15

    Purpose: {sup 31}P MR spectroscopy (MRS) allows the noninvasive assessment of metabolic alterations in tumors. Due to physical as well as technical limitations, mostly large and single voxels are used. We used a spatially resolved 31P MRS technique to characterize metabolic abnormalities inside and adjacent to liver metastases of patients with uvea melanoma. Materials and Methods: Optimization of 3D chemical shift imaging (3D CSI) was performed in healthy volunteers (n = 19; voxel size 25 ml). Patients (n = 8) with liver metastases were then examined. Cross sectional imaging was available for all patients. Results: Compared to healthy volunteers, the PME/PDE ratios of patients with liver metastasis were significantly higher (0.56 {+-} 0.30 vs. 0.39 {+-} 0.21; p < 0.05). A trend towards increased PME/beta ATP ratios (2.07 {+-} 1.83 vs. 1.02 {+-} 0.45; p = 0.12) and decreased Pi/PME ratios (0.57 {+-} 0.29 vs. 1.06 {+-} 0.58; p = 0.06) was also observed. Patients with metastases {>=} 5 cm showed significantly higher PME/PDE ratios (0.68 {+-} 0.17 vs. 0.45 {+-} 0.03; p < 0.05). Liver parenchyma adjacent to metastases did not show any significant changes compared to non-diseased tissue. Conclusion: 3D CSI allows the simultaneous analysis of metabolic alterations in diseased as well as in healthy human liver. Metastases show significant metabolic alterations. Thus, {sup 31}P MRS opens new possibilities for therapeutic monitoring. (orig.)

  14. The Chemistry Scoring Index (CSI: A Hazard-Based Scoring and Ranking Tool for Chemicals and Products Used in the Oil and Gas Industry

    Directory of Open Access Journals (Sweden)

    Tim Verslycke

    2014-06-01

    Full Text Available A large portfolio of chemicals and products is needed to meet the wide range of performance requirements of the oil and gas industry. The oil and gas industry is under increased scrutiny from regulators, environmental groups, the public, and other stakeholders for use of their chemicals. In response, industry is increasingly incorporating “greener” products and practices but is struggling to define and quantify what exactly constitutes “green” in the absence of a universally accepted definition. We recently developed the Chemistry Scoring Index (CSI which is ultimately intended to be a globally implementable tool that comprehensively scores and ranks hazards to human health, safety, and the environment for products used in oil and gas operations. CSI scores are assigned to products designed for the same use (e.g., surfactants, catalysts on the basis of product composition as well as intrinsic hazard properties and data availability for each product component. As such, products with a lower CSI score within a product use group are considered to have a lower intrinsic hazard compared to other products within the same use group. The CSI provides a powerful tool to evaluate relative product hazards; to review and assess product portfolios; and to aid in the formulation of products.

  15. The subtype I-F CRISPR-Cas system influences pathogenicity island retention in Pectobacterium atrosepticum via crRNA generation and Csy complex formation.

    Science.gov (United States)

    Richter, Corinna; Fineran, Peter C

    2013-12-01

    CRISPR (clustered regularly interspaced short palindromic repeats) arrays and Cas (CRISPR-associated) proteins confer acquired resistance against mobile genetic elements in a wide range of bacteria and archaea. The phytopathogen Pectobacterium atrosepticum SCRI1043 encodes a single subtype I-F CRISPR system, which is composed of three CRISPR arrays and the cas operon encoding Cas1, Cas3 (a Cas2-Cas3 fusion), Csy1, Csy2, Csy3 and Cas6f (Csy4). The CRISPR arrays are transcribed into pre-crRNA (CRISPR RNA) and then processed by Cas6f to generate crRNAs. Furthermore, the formation of Cas protein complexes has been implicated in both the interference and acquisition stages of defence. In the present paper, we discuss the development of tightly controlled 'programmable' CRISPR arrays as tools to investigate CRISPR-Cas function and the effects of chromosomal targeting. Finally, we address how chromosomal targeting by CRISPR-Cas can cause large-scale genome deletions, which can ultimately influence bacterial evolution and pathogenicity.

  16. Radicals and ions controlling by adjusting the antenna-substrate distance in a-Si:H deposition using a planar ICP for c-Si surface passivation

    Science.gov (United States)

    Zhou, H. P.; Xu, S.; Xu, M.; Xu, L. X.; Wei, D. Y.; Xiang, Y.; Xiao, S. Q.

    2017-02-01

    Being a key issue in the research and fabrication of silicon heterojunction (SHJ) solar cells, crystalline silicon (c-Si) surface passivation is theoretically and technologically intricate due to its complicate dependence on plasma characteristics, material properties, and plasma-material interactions. Here amorphous silicon (a-Si:H) grown by a planar inductively coupled plasma (ICP) reactor working under different antenna-substrate distances of d was used for the surface passivation of low-resistivity p-type c-Si. It is found that the microstructures (i.e., the crystallinity, Si-H bonding configuration etc.) and passivation function on c-Si of the deposited a-Si:H were profoundly influenced by the parameter of d, which primarily determines the types of growing precursors of SiHn/H contributing to the film growth and the interaction between the plasma and growing surface. c-Si surface passivation is analyzed in terms of the d-dependent a-Si:H properties and plasma characteristics. The controlling of radical types and ion bombardment on the growing surface through adjusting parameter d is emphasized.

  17. High-gradient High-charge CW Superconducting RF gun with CsK2Sb photocathode

    CERN Document Server

    Pinayev, Igor; Tuozzolo, Joseph; Brutus, Jean Clifford; Belomestnykh, Sergey; Boulware, Chase; Folz, Charles; Gassner, David; Grimm, Terry; Hao, Yue; Jamilkowski, James; Jing, Yichao; Kayran, Dmitry; Mahler, George; Mapes, Michael; Miller, Toby; Narayan, Geetha; Sheehy, Brian; Rao, Triveni; Skaritka, John; Smith, Kevin; Snydstrup, Louis; Than, Yatming; Wang, Erdong; Wang, Gang; Xiao, Binping; Xin, Tianmu; Zaltsman, Alexander; Altinbas, Z; Ben-Zvi, Ilan; Curcio, Anthony; Di Lieto, Anthony; Meng, Wuzheng; Minty, Michiko; Orfin, Paul; Reich, Jonathan; Roser, Thomas; Smart, Loralie A; Soria, Victor; Theisen, Charles; Xu, Wencan; Wu, Yuan H; Zhao, Zhi

    2015-01-01

    High-gradient CW photo-injectors operating at high accelerating gradients promise to revolutionize many sciences and applications. They can establish the basis for super-bright monochromatic X-ray free-electron lasers, super-bright hadron beams, nuclear- waste transmutation or a new generation of microchip production. In this letter we report on our operation of a superconducting RF electron gun with a record-high accelerating gradient at the CsK2Sb photocathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (i.e., 3 nC). We briefly describe the system and then detail our experimental results. This achievement opens new era in generating high-power electron beams with a very high brightness.

  18. Recent Progress at SLAC Extracting High Charge from Highly-Polarized Photocathodes for Future-Collider Applications

    CERN Document Server

    Clendenin, J E; Garwin, E L; Harvey, S; Jiang, J; Kirby, R E; Luh, D A; Maruyama, T; Prepost, R; Prescott, C Y; Turner, J L

    2004-01-01

    Future colliders such as NLC and JLC will require a highly-polarized macropulse with charge that is more than an order of magnitude beyond that which could be produced for the SLC. The maximum charge from the SLC uniformly-doped GaAs photocathode was limited by the surface charge limit (SCL). The SCL effect can be overcome by using an extremely high (>1019 cm-3) surface dopant concentration. When combined with a medium dopant concentration in the majority of the active layer (to avoid depolarization), the surface concentration has been found to degrade during normal heat cleaning (1 hour at 600 C). The Be dopant as typically used in an MBE-grown superlattice cathode is especially susceptible to this effect compared to Zn or C dopant. Some relief can be found by lowering the cleaning temperature, but the long-term general solution appears to be atomic hydrogen cleaning.

  19. Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

    Science.gov (United States)

    Pompili, R.; Anania, M. P.; Bellaveglia, M.; Biagioni, A.; Castorina, G.; Chiadroni, E.; Cianchi, A.; Croia, M.; Di Giovenale, D.; Ferrario, M.; Filippi, F.; Gallo, A.; Gatti, G.; Giorgianni, F.; Giribono, A.; Li, W.; Lupi, S.; Mostacci, A.; Petrarca, M.; Piersanti, L.; Di Pirro, G.; Romeo, S.; Scifo, J.; Shpakov, V.; Vaccarezza, C.; Villa, F.

    2016-08-01

    The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

  20. Measurements and Studies of Secondary Electron Emission of Diamond Amplified Photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Wu,Q.

    2008-10-01

    The Diamond Amplified Photocathode (DAP) is a novel approach to generating electrons. By following the primary electron beam, which is generated by traditional electron sources, with an amplifier, the electron beam available to the eventual application is increased by 1 to 2 orders of magnitude in current. Diamond has a very wide band gap of 5.47eV which allows for a good negative electron affinity with simple hydrogenation, diamond can hold more than 2000MV/m field before breakdown. Diamond also provides the best rigidity among all materials. These two characters offer the capability of applying high voltage across very thin diamond film to achieve high SEY and desired emission phase. The diamond amplifier also is capable of handling a large heat load by conduction and sub-nanosecond pulse input. The preparation of the diamond amplifier includes thinning and polishing, cleaning with acid etching, metallization, and hydrogenation. The best mechanical polishing available can provide high purity single crystal diamond films with no less than 100 {micro}m thickness and <15 nm Ra surface roughness. The ideal thickness for 700MHz beam is {approx}30 {micro}m, which requires further thinning with RIE or laser ablation. RIE can achieve atomic layer removal precision and roughness eventually, but the time consumption for this procedure is very significant. Laser ablation proved that with <266nm ps laser beam, the ablation process on the diamond can easily achieve removing a few microns per hour from the surface and <100nm roughness. For amplifier application, laser ablation is an adequate and efficient process to make ultra thin diamond wafers following mechanical polishing. Hydrogenation will terminate the diamond surface with monolayer of hydrogen, and form NEA so that secondary electrons in the conduction band can escape into the vacuum. The method is using hydrogen cracker to strike hydrogen atoms onto the bare diamond surface to form H-C bonds. Two independent

  1. Tuning the Photoelectrocatalytic Hydrogen Evolution of Pt-Decorated Silicon Photocathodes by the Temperature and Time of Electroless Pt Deposition.

    Science.gov (United States)

    Fabre, Bruno; Li, Gaozeng; Gouttefangeas, Francis; Joanny, Loic; Loget, Gabriel

    2016-11-15

    The electroless deposition of Pt nanoparticles (NPs) on hydrogen-terminated silicon (H-Si) surfaces is studied as a function of the temperature and the immersion time. It is demonstrated that isolated Pt structures can be produced at all investigated temperatures (between 22 and 75 °C) for short deposition times, typically within 1-10 min if the temperature is 45 °C or less than 5 min at 75 °C. For longer times, dendritic metal structures start to grow, ultimately leading to highly rough interconnected Pt networks. Upon increasing the temperature from 22 to 75 °C and for an immersion time of 5 min, the average size of the observed Pt NPs monotonously increases from 120 to 250 nm, and their number density calculated using scanning electron microscopy decreases from (4.5 ± 1.0) × 10(8) to (2.0 ± 0.5) × 10(8) Pt NPs cm(-2). The impact of both the morphology and the distribution of the Pt NPs on the photoelectrocatalytic activity of the resulting metallized photocathodes is then analyzed. Pt deposited at 45 °C for 5 min yields photocathodes with the best electrocatalytic activity for the hydrogen evolution reaction. Under illumination at 33 mW cm(-2), this optimized photoelectrode shows a fill factor of 45%, an efficiency (η) of 9.7%, and a short-circuit current density (|Jsc|) at 0 V versus a reversible hydrogen electrode of 15.5 mA cm(-2).

  2. Manufacturing metrology for c-Si photovoltaic module reliability and durability, Part I: Feedstock, crystallization and wafering

    Energy Technology Data Exchange (ETDEWEB)

    Seigneur, Hubert; Mohajeri, Nahid; Brooker, R. Paul; Davis, Kristopher O.; Schneller, Eric J.; Dhere, Neelkanth G.; Rodgers, Marianne P.; Wohlgemuth, John; Shiradkar, Narendra S.; Scardera, Giuseppe; Rudack, Andrew C.; Schoenfeld, Winston V.

    2016-06-01

    This article is the first in a three-part series of manufacturing metrology for c-Si photovoltaic (PV) module reliability and durability. Here in Part 1 we focus on the three primary process steps for making silicon substrates for PV cells: (1) feedstock production; (2) ingot and brick production; and (3) wafer production. Each of these steps can affect the final reliability/durability of PV modules in the field with manufacturing metrology potentially playing a significant role. This article provides a comprehensive overview of historical and current processes in each of these three steps, followed by a discussion of associated reliability challenges and metrology strategies that can be employed for increased reliability and durability in resultant modules. Gaps in the current state of understanding in connective metrology data during processing to reliability/durability in the field are then identified along with suggested improvements that should be considered by the PV community.

  3. From 1 Sun to 10 Suns c-Si Cells by Optimizing Metal Grid, Metal Resistance, and Junction Depth

    Directory of Open Access Journals (Sweden)

    Vikrant A. Chaudhari

    2009-01-01

    Full Text Available Use of a solar cell in concentrator PV technology requires reduction in its series resistance in order to minimize the resistive power losses. The present paper discusses a methodology of reducing the series resistance of a commercial c-Si solar cell for concentrator applications, in the range of 2 to 10 suns. Step by step optimization of commercial cell in terms of grid geometry, junction depth, and electroplating of the front metal contacts is proposed. A model of resistance network of solar cell is developed and used for the optimization. Efficiency of unoptimized commercial cell at 10 suns drops by 30% of its 1 sun value corresponding to resistive power loss of about 42%. The optimized cell with grid optimization, junction optimization, electroplating, and junction optimized with electroplated contacts cell gives resistive power loss of 20%, 16%, 11%, and 8%, respectively. An efficiency gain of 3% at 10 suns for fully optimized cell is estimated.

  4. Front-end electronics for CsI based charged particle array for the study of reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Jhingan, Akhil, E-mail: akhil@iuac.res.in [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Sugathan, P. [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Kaur, Gurpreet; Kapoor, K. [Department of Physics, Panjab University, Chandigarh 160014 (India); Saneesh, N.; Banerjee, T. [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Singh, Hardev [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Kumar, A.; Behera, B.R. [Department of Physics, Panjab University, Chandigarh 160014 (India); Nayak, B.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2015-06-21

    The characteristics and performance of a new detector system based on CsI(TI) scintillators, and its front-end electronics are presented. The detector system has been developed for the detection of light charged particles to investigate fusion–fission dynamics, and will also serve as ancillary detector for an array of neutron detectors. CsI scintillators are read by photo-diodes. The main feature of the array is its compact and simple high density front-end electronics which includes custom developed low noise charge sensitive preamplifiers (with very low power consumption for operation inside vacuum), NIM differential drivers, and commercially available Mesytec amplifiers with two different time constants for particle identification using a ballistic deficit technique.

  5. Development Status and Performance Comparisons of Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Harder, Bryan

    2016-01-01

    Environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft turbine engine systems, because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. This paper presents current NASA EBC-CMC development emphases including: the coating composition and processing improvements, laser high heat flux-thermal gradient thermo-mechanical fatigue - environmental testing methodology development, and property evaluations for next generation EBC-CMC systems. EBCs processed with various deposition techniques including Plasma Spray, Electron Beam - Physical Vapor Deposition, and Plasma Spray Physical Vapor Deposition (PS-PVD) will be particularly discussed. The testing results and demonstrations of advanced EBCs-CMCs in complex simulated engine thermal gradient cyclic fatigue, oxidizing-steam and CMAS environments will help provide insights into the coating development strategies to meet long-term engine component durability goals.

  6. Research on the Hedging of CSI300 Stock Index Future Based on VaR and CVaR Model

    Directory of Open Access Journals (Sweden)

    Xu Zijian

    2015-01-01

    Full Text Available Hedging function is one of the most significant functions of stock index futures, and it received extensive public attention. This article set VaR and CVaR as hedging objective function of the hedging model in China and proposed the hedging effect measurement method based on VaR and CVaR. It also used the actual data of CSI300 stock index future to calculate its hedging effect. It is found from the result that the hedging model of stock index future based on VaR and CVaR can effectively reduce the risk of portfolio, and a relatively good accumulated income rate will be obtained. By comparison, the hedging model of stock index future based on CVaR will do better in controlling the risk of portfolio, while the hedging model of stock index future based on VaR will obtain a better accumulated income rate.

  7. Exact Outage Probability of Dual-Hop CSI-Assisted AF Relaying Over Nakagami-m Fading Channels

    KAUST Repository

    Xia, Minghua

    2012-10-01

    In this correspondence, considering dual-hop channel state information (CSI)-assisted amplify-and-forward (AF) relaying over Nakagami- m fading channels, the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) is derived. In particular, when the fading shape factors m1 and m2 at consecutive hops take non-integer values, the bivariate H-function and G -function are exploited to obtain an exact analytical expression for the CDF. The obtained CDF is then applied to evaluate the outage performance of the system under study. The analytical results of outage probability coincide exactly with Monte-Carlo simulation results and outperform the previously reported upper bounds in the low and medium SNR regions.

  8. Reality and fiction in US TV series: Lost, CSI and The West Wing. Narrative strategies and verosimilitude

    Directory of Open Access Journals (Sweden)

    Anna Tous Rovirosa

    2010-12-01

    Full Text Available The purpose of this paper is to present a methodology of analysis of TV series, taking into account the use of reality and fiction in the narrative construction of these series, as well as the use of verosimilitude in „real-world‟ series. With the methodology chosen, the purpose is to distinguish between the usage of reality and fiction, on one hand, and the usage of thematic recurrence, myth and metaTV references, on the other. The methodology consists of the edition of televisual text. For, inasmuch as we consider that drama series are a text, they can be edited. The empirical analysis deals with three US TV series: Lost, ABC: 2004-, CSI: Crime Scene Investigation, CBS: 2000- and The West Wing, NBC: 1999-2006. They all belong to the drama‟s era, but each of them represents a specific subgenre: adventures and science-fiction, crime and forensic, and workplace and politics.

  9. Imaging responses of on-site CsI and Gd2O2S flat-panel detectors: Dependence on the tube voltage

    Science.gov (United States)

    Jeon, Hosang; Chung, Myung Jin; Youn, Seungman; Nam, Jiho; Lee, Jayoung; Park, Dahl; Kim, Wontaek; Ki, Yongkan; Kim, Ho Kyung

    2015-07-01

    One of the emerging issues in radiography is low-dose imaging to minimize patient's exposure. The scintillating materials employed in most indirect flat-panel detectors show a drastic change of X-ray photon absorption efficiency around their K-edge energies that consequently affects image quality. Using various tube voltages, we investigated the imaging performance of most popular scintillators: cesium iodide (CsI) and gadolinium oxysulfide (Gd2O2S). The integrated detective quantum efficiencies (iDQE) of four detectors installed in the same hospital were evaluated according to the standardized procedure IEC 62220-1 at tube voltages of 40 - 120 kVp. The iDQE values of the Gd2O2S detectors were normalized by those of CsI detectors to exclude the effects of image postprocessing. The contrast-to-noise ratios (CNR) were also evaluated by using an anthropomorphic chest phantom. The iDQE of the CsI detector outperformed that of the Gd2O2S detector over all tube voltages. Moreover, we noted that the iDQE of the Gd2O2S detectors quickly rolled off with decreasing tube voltage under 70 kVp. The CNRs of the two scintillators were similar at 120 kVp. At 60 kVp, however, the CNR of Gd2O2S was about half that of CsI. Compared to the Gd2O2S detectors, variations in the DQE performance of the CsI detectors were relatively immune to variations in the applied tube voltages. Therefore, we claim that Gd2O2S detectors are inappropriate for use in low-tube-voltage imaging (e.g., extremities and pediatrics) with low patient exposure.

  10. A gas scintillation counter with imaging optics and large area UV-detector

    Energy Technology Data Exchange (ETDEWEB)

    Nickles, J. E-mail: nickles@hsb.uni-frankfurt.de; Braeuning, H.; Braeuning-Demian, A.; Dangendorf, V.; Breskin, A.; Chechik, R.; Rauschnabel, K.; Schmidt-Boecking, H

    2002-01-21

    We report on the improvements in the position sensitive readout of a xenon-filled gas scintillation proportional counter. Using an imaging optic for UV-light in the region of 170 nm, the position resolution could be improved by more than 30%. In addition, we have obtained first encouraging results for the use of the recently developed gas electron multiplier together with a CsI-photocathode as a large area UV-detector system.

  11. A gas scintillation counter with imaging optics and large area UV-detector

    CERN Document Server

    Nickles, J; Bräuning-Demian, A; Breskin, Amos; Chechik, R; Dangendorf, V; Rauschnabel, K; Schmidt-Böcking, H

    2002-01-01

    We report on the improvements in the position sensitive readout of a xenon-filled gas scintillation proportional counter. Using an imaging optic for UV-light in the region of 170 nm, the position resolution could be improved by more than 30%. In addition, we have obtained first encouraging results for the use of the recently developed gas electron multiplier together with a CsI-photocathode as a large area UV-detector system.

  12. Designing Efficient Solar-Driven Hydrogen Evolution Photocathodes Using Semitransparent MoQxCly(Q = S, Se) Catalysts on Si Micropyramids

    KAUST Repository

    Ding, Qi

    2015-09-21

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Silicon micropyramids with n+pp+ junctions are demonstrated to be efficient absorbers for integrated solar-driven hydrogen production systems enabling significant improvements in both photocurrent and onset potential. When conformally coated with MoSxCly, a catalyst that has excellent catalytic activity and high optical transparency, the highest photocurrent density for Si-based photocathodes with earth-abundant catalysts is achieved.

  13. A Measurement Method of Time Jitter of a Laser Pulse with Respect to the Radio-Frequency Wave Phase in a Photocathode Radio-Frequency Gun

    Institute of Scientific and Technical Information of China (English)

    刘圣广; 李永贵; 王鸣凯

    2002-01-01

    In a photo-cathode radio-frequency (rf) gun, the micro-bunched charge output from the gun is dependent linearly on the laser injection phase, due to the Scottay effect in the process of photoemission and the procedure of the electron longitudinal acceleration. Based on this principle, a new method is proposed, which should be utilized to measure the time jitter between the driving laser pulse and the rf phase with a very high resolution of a few tens of femtoseconds.

  14. 沪深300 ETF套期保值效果的比较研究%The Comparative Study of CSI 300 ETF Hedging Effects

    Institute of Scientific and Technical Information of China (English)

    丁于兰

    2014-01-01

    This article uses models of OLS、ECM、CCC-BGARCH and DCC-BGARCH,calculates the opti-mal hedge ratio of the two CSI 300 ETF,and compares the hedging effects of the two CSI 300 ETF. The research in-dicates that the effect of dynamic multivariate GARCH model is significantly detter than the effect of OLS and ECM model. Whichever model,the hedging effect of Huatai-PineBridge CSI 300 ETF is detter than the effect of Harvest CSI 300 ETF. Due to its high liquidity and relatively well -developed arditrage mechanism,Huatai -PineBridge CSI 300 ETF is more suitadle for DCC-BGARCH model which has larger variance changes. Meanwhile,Harvest CSI 300 ETF is more suitadle for CCC-BGARCH model decause the relevance fluctuations detween the two ETF in futures is small and the correlation coefficient is closer to constant.%文章采用OLS、ECM、CCC-BGARCH以及DCC-BGARCH模型分别计算了两支300 ETF的最优套期保值比率,并分别比较了两支300 ETF的套期保值效果,结果发现:动态多元GARCH类模型的效果明显好于OLS和ECM模型;无论采用哪种模型,华泰柏瑞沪深300 ETF的套期保值效果都要好于嘉实沪深300 ETF;由于华泰柏瑞沪深300 ETF的高流动性和相对完善的套利机制,使得其适合较大方差变化的DCC-BGARCH模型;而嘉实沪深300 ETF采用CCC-BGARCH模型的套期保值效果更好,这可能是因为嘉实沪深300 ETF和沪深300股指期货间的关联性波动较小,相关系数更接近于常数的缘故。

  15. Transmission photocathodes based on stainless steel mesh and quartz glass coated with N-doped DLC thin films prepared by reactive magnetron sputtering

    Science.gov (United States)

    Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Arbet, J.

    2016-03-01

    The influence was investigated of N-doped diamond-like carbon (DLC) films properties on the quantum efficiency of a prepared transmission photocathode. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with 5 nm thick Cr adhesion film) by reactive magnetron sputtering using a carbon target and gas mixture Ar, 90%N2+10%H2. The elements' concentration in the films was determined by RBS and ERD. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. For the study of the vectorial photoelectric effect, the quartz type photocathode was irradiated by intensive laser pulses to form pin-holes in the DLC film. The quantum efficiency (QE), calculated at a laser energy of 0.4 mJ, rose as the nitrogen concentration in the DLC films was increased and rose dramatically after the micron-size perforation in the quartz type photocathodes.

  16. Unbiased Sunlight-Driven Artificial Photosynthesis of Carbon Monoxide from CO2 Using a ZnTe-Based Photocathode and a Perovskite Solar Cell in Tandem.

    Science.gov (United States)

    Jang, Youn Jeong; Jeong, Inyoung; Lee, Jaehyuk; Lee, Jinwoo; Ko, Min Jae; Lee, Jae Sung

    2016-07-26

    Solar fuel production, mimicking natural photosynthesis of converting CO2 into useful fuels and storing solar energy as chemical energy, has received great attention in recent years. Practical large-scale fuel production needs a unique device capable of CO2 reduction using only solar energy and water as an electron source. Here we report such a system composed of a gold-decorated triple-layered ZnO@ZnTe@CdTe core-shell nanorod array photocathode and a CH3NH3PbI3 perovskite solar cell in tandem. The assembly allows effective light harvesting of higher energy photons (>2.14 eV) from the front-side photocathode and lower energy photons (>1.5 eV) from the back-side-positioned perovskite solar cell in a single-photon excitation. This system represents an example of a photocathode-photovoltaic tandem device operating under sunlight without external bias for selective CO2 conversion. It exhibited a steady solar-to-CO conversion efficiency over 0.35% and a solar-to-fuel conversion efficiency exceeding 0.43% including H2 as a minor product.

  17. Band gap design of graphene photocathode%石墨烯光阴极带隙设计

    Institute of Scientific and Technical Information of China (English)

    李世龙; 石峰; 张太民; 刘照路; 张番; 李丹; 任兆玉

    2015-01-01

    In order to achieve graphene photocathode photoelectric conversion function, hexagonal boron nitride was doped in graphene in the form of hybrid superlattices nanoribbons. As can be seen from the band structure which was obtained by applying first-principles methods, the band gap of the superlattices was effectively regulated in a wide range (0-2.5 eV) by this means. The mechanism of band gap regulation was analyzed by the energy band structure and the charge density distribution. Furthermore, the present results were coincidence with the conclusion of Kronig-Penney model. With the increase of the h-BN proportion, the band gap engineering of graphene materials in this way, the band gap increases both zigzag edges superlattices nanoribbons and armchair edges superlattices nanoribbons. Besides, the band gap is almost independent of the width of nanoribbons, thus the size of the material can be more miniaturized. Moreover, the graphene photocathode with the gradient band gap characteristic can be made based on this approach, it can respond to different spectral ranges.%为了使石墨烯光阴极实现光电转化功能,以超晶格形式掺杂六角氮化硼到石墨烯中,形成杂化纳米带.通过基于第一性原理的计算,从能带结构可以看出,这种方法可以在一个很大的范围内(0~2.5 eV)调控带隙大小.结合能带结构和电荷密度分布分析了带隙调控的机理,此外,运用K-P模型理论分析也得到了一致的结果.以这种方式调控石墨烯材料的带隙,锯齿型边缘和扶手椅型边缘的六角氮化硼/石墨烯(h-BN/graphene)超晶格纳米带,其带隙大小均随着其中h-BN所占比例的增加而变大,而且其带隙大小几乎不受纳米带宽度的影响,这样一来材料的尺寸可以做到更加微型化.再者,基于此方法可以制成渐变带隙结构,进而实现同一光阴极对不同范围光谱的响应.

  18. Atomic layer deposited borosilicate glass microchannel plates for large area event counting detectors

    Science.gov (United States)

    Siegmund, O. H. W.; McPhate, J. B.; Tremsin, A. S.; Jelinsky, S. R.; Hemphill, R.; Frisch, H. J.; Elam, J.; Mane, A.; Lappd Collaboration

    2012-12-01

    Borosilicate glass micro-capillary array substrates with 20 μm and 40 μm pores have been deposited with resistive, and secondary electron emissive, layers by atomic layer deposition to produce functional microchannel plates. Device formats of 32.7 mm and 20 cm square have been fabricated and tested in analog and photon counting modes. The tests show amplification, imaging, background rate, pulse shape and lifetime characteristics that are comparable to standard glass microchannel plates. Large area microchannel plates of this type facilitate the construction of 20 cm format sealed tube sensors with strip-line readouts that are being developed for Cherenkov light detection. Complementary work has resulted in Na2KSb bialkali photocathodes with peak quantum efficiency of 25% being made on borosilicate glass. Additionally GaN (Mg) opaque photocathodes have been successfully made on borosilicate microchannel plates.

  19. Microwave measurements and beam dynamics simulations of the BNL/SLAC/UCLA emittance-compensated 1.6-cell photocathode rf gun

    Science.gov (United States)

    Palmer, Dennis T.; Miller, Roger H.; Winick, Herman; Wang, Xi J.; Batchelor, Kenneth; Woodle, Martin H.; Ben-Zvi, Ilan

    1995-09-01

    A dedicated low energy (2 to 10 MeV) experimental beam line is now under construction at Brookhaven National Laboratory/Accelerator Test Facility (BNL/ATF) for photocathode RF gun testing and photoemission experiments. Microwave measurements of the 1.6 cell photocathode RF gun have been conducted along with beam dynamics simulations of the emittance compensated low energy beam. These simulations indicate that the 1.6 cell photocathode RF gun in combination with solenoidal emittance compensation will be capable of producing a high brightness beam with a normalization rms emittance of (epsilon) n,rms approximately equals 1 (pi) mm mrad. The longitudinal accelerating field Ez has been measured as a function of azimuthal angle in the full cell of the cold test model for the 1.6 cell BNL/SLAC/UCLA #3 S-band RF Gun using a needle rotation/frequency perturbation technique. These measurements were conducted before and after symmetrizing the full cell with a vacuum pump out port and an adjustable short. Two different waveguide to full cell coupling schemes were studied. Experimental and theoretical studies of the field balance versus mode separation were conducted. The dipole mode of the full cell using the (theta) - coupling scheme is an order of magnitude less severe before symmetrization than the Z- coupling scheme. The multi-pole contribution to the longitudinal field asymmetry are calculated using standard Fourier series techniques for both coupling schemes. The Panofsky- Wenzel theorem is used in estimating the transverse emittance due to the multipole components of Ez. Detailed beam dynamics simulations were performed for the 1.6 cell photocathode RF gun injector using a solenoidal emittance compensation technique. The design of the experimental line along with a proposed experimental program using the 1.6 cell photocathode RF gun developed by the BNL/SLAC/UCLA RF gun collaboration is presented. This experimental program includes measurements of beam loading caused

  20. Role of field-effect on c-Si surface passivation by ultrathin (2-20 nm) atomic layer deposited Al2O3

    Science.gov (United States)

    Terlinden, N. M.; Dingemans, G.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2010-03-01

    Al2O3 synthesized by plasma-assisted atomic layer deposition yields excellent surface passivation of crystalline silicon (c-Si) for films down to ˜5 nm in thickness. Optical second-harmonic generation was employed to distinguish between the influence of field-effect passivation and chemical passivation through the measurement of the electric field in the c-Si space-charge region. It is demonstrated that this electric field—and hence the negative fixed charge density—is virtually unaffected by the Al2O3 thickness between 2 and 20 nm indicating that a decrease in chemical passivation causes the reduced passivation performance for <5 nm thick Al2O3 films.

  1. An application of CCD read-out technique to neutron distribution measurement using the self-activation method with a CsI scintillator plate

    Science.gov (United States)

    Nohtomi, Akihiro; Kurihara, Ryosuke; Kinoshita, Hiroyuki; Honda, Soichiro; Tokunaga, Masaaki; Uno, Heita; Shinsho, Kiyomitsu; Wakabayashi, Genichiro; Koba, Yusuke; Fukunaga, Junichi; Umezu, Yoshiyuki; Nakamura, Yasuhiko; Ohga, Saiji

    2016-10-01

    In our previous paper, the self-activation of an NaI scintillator had been successfully utilized for detecting photo-neutrons around a high-energy X-ray radiotherapy machine; individual optical pulses from the self-activated scintillator are read-out by photo sensors such as a photomultiplier tube (PMT). In the present work, preliminary observations have been performed in order to apply a direct CCD read-out technique to the self-activation method with a CsI scintillator plate using a Pu-Be source and a 10-MV linac. In conclusion, it has been revealed that the CCD read-out technique is applicable to neutron measurement around a high-energy X-ray radiotherapy machine with the self-activation of a CsI plate. Such application may provide a possibility of novel method for simple neutron dose-distribution measurement.

  2. Detection of Potential Induced Degradation in c-Si PV Panels Using Electrical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso;

    2016-01-01

    Impedance spectroscopy (IS) is an established characterization method in different electrical and chemical research areas, but not yet adopted as a commercial diagnostic tool for PV panels. This work, for the first time, proposes an IS based method for detecting potential-induced degradation (PID...

  3. The formation of the positive, fixed charge at c-Si(111)/a-Si$_3$N$_{3.5}$:H interfaces

    CERN Document Server

    Hintzsche, L E; Marsman, M; Lamers, M W P E; Weeber, A W; Kresse, G

    2015-01-01

    Modern electronic devices are unthinkable without the well-controlled formation of interfaces at heterostructures. These often involve at least one amorphous material. Modeling such interfaces poses a significant challenge, since a meaningful result can only be expected by using huge models or by drawing from many statistically independent samples. Here we report on the results of high throughput calculations for interfaces between crystalline silicon (c-Si) and amorphous silicon nitride (a-Si$_3$N$_{3.5}$:H), which are omnipresent in commercially available solar cells. The findings reconcile only partly understood key features. At the interface, threefold coordinated Si atoms are present. These are caused by the structural mismatch between the amorphous and crystalline part. The local Fermi level of undoped c-Si lies well below that of a-SiN:H. To align the Fermi levels in the device, charge is transferred from the a-SiN:H part to the c-Si part resulting in an abundance of positively charged, threefold coord...

  4. Chitin-Prussian blue sponges for Cs(I) recovery: From synthesis to application in the treatment of accidental dumping of metal-bearing solutions

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, C. [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France); Commissariat à l' Energie Atomique, CEA Marcoule, DEN/DTCD/SPDE/LPSD,BP 17171, F-30207 Bagnols sur Cèze (France); Barré, Y. [Commissariat à l' Energie Atomique, CEA Marcoule, DEN/DTCD/SPDE/LPSD,BP 17171, F-30207 Bagnols sur Cèze (France); Vincent, T. [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France); Taulemesse, J.-M. [Ecole des mines d' Alès, Center des Matériaux des Mines d' Alès, 6 avenue de Clavières, F-30319 Alès Cedex (France); Robitzer, M. [Institut Charles Gerhardt – UMR5253, CNRS-UM2-ENSCM-UM1, ICGM-MACS-R2M2, 8 rue de l' Ecole Normale, F-34296 Montpellier Cedex 05 (France); Guibal, E., E-mail: Eric.Guibal@mines-ales.fr [Ecole des mines d' Alès, Centre des Matériaux des Mines d' Alès, C2MA/MPA/BCI, 6 avenue de Clavières, F-30319 Alès Cedex (France)

    2015-04-28

    Highlights: • Prussian blue microparticles incorporated in chitin sponges. • Efficient Cs(I) sorption after water absorption by dry hybrid sponge. • Water draining after sorption for metal confinement and water decontamination. • High decontamination factors and distribution coefficients for Cs(I) and {sup 137}Cs(I). • Effect of freezing conditions on porous structure and textural characterization. - Abstract: Prussian blue (i.e., iron[III] hexacyanoferrate[II], PB) has been synthesized by reaction of iron(III) chloride with potassium hexacyanoferrate and further immobilized in chitosan sponge (cellulose fibers were added in some samples to evaluate their impact on mechanical resistance). The composite was finally re-acetylated to produce a chitin-PB sponge. Experimental conditions such as the freezing temperature, the content of PB, the concentration of the biopolymer and the presence of cellulose fibers have been varied in order to evaluate their effect on the porous structure of the sponge, its water absorption properties and finally its use for cesium(I) recovery. The concept developed with this system consists in the absorption of contaminated water by the composite sponge, the in situ binding of target metal on Prussian blue load and the centrifugation of the material to remove treated water from soaked sponge. This material is supposed to be useful for the fast treatment of accidental dumping of Cs-contaminated water.

  5. H2-Ar dilution for improved c-Si quantum dots in P-doped SiNx:H thin film matrix

    Science.gov (United States)

    Liu, Jia; Zhang, Weijia; Liu, Shengzhong (Frank)

    2017-02-01

    Phosphorus-doped hydrogenated silicon nitride (SiNx:H) thin films containing crystalline silicon quantum dot (c-Si QD) was prepared by plasma enhanced chemical vapor deposition (PECVD) using hydrogen-argon mixed dilution. The effects of H2/Ar flow ratio on the structural, electrical and optical characteristics of as-grown P-doped SiNx:H thin films were systematically investigated. Experimental results show that crystallization is promoted by increasing the H2/Ar flow ratio in dilution, while the N/Si atomic ratio is higher for thin film deposited with argon-rich dilution. As the H2/Ar flow ratio varies from 100/100 to 200/0, the samples exhibit excellent conductivity owing to the large volume fraction of c-Si QDs and effective P-doping. By adjusting the H2/Ar ratio to 100/100, P-doped SiNx:H thin film containing tiny and densely distributed c-Si QDs can be obtained. It simultaneously possesses wide optical band gap and high dark conductivity. Finally, detailed discussion has been made to analyze the influence of H2-Ar mixed dilution on the properties of P-doped SiNx:H thin films.

  6. Concentration-dependent study of electronic and optical properties of c-Si and c-Si:H

    Energy Technology Data Exchange (ETDEWEB)

    Nunez-Gonzalez, R. [Departamento de Matematicas, Universidad de Sonora, C.P. 83000, Hermosillo, Sonora (Mexico); Posada-Amarillas, A. [Departamento de Investigacion en Fisica, Universidad de Sonora, Apdo. Postal 5-088 C.P. 83190, Hermosillo, Sonora (Mexico); Galvan, D.H.; Reyes-Serrato, A. [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Ensenada, B. C. (Mexico)

    2011-07-15

    Electronic and optical properties of crystalline silicon (c-Si) and hydrogen-doped crystalline silicon (c-Si:H) were calculated using the full-potential linearized augmented plane waves (FLAPWs) method, within the density functional theory (DFT), and the supercell method to model different hydrogen concentrations. Hydrogen was introduced in both bond-centered (BC) and tetrahedral (Td) interstitial sites to find out the most favorable configuration by searching for the lowest energy structure. The Td interstitial site yields the most stable and lowest energy structure. For several hydrogen concentrations we found that the effect of interstitial hydrogen is to introduce electronic states at the silicon band gap, turning it into a metallic system. Analysis of the calculated energy-loss function of doped silicon shows the existence of a plasmon peak at low energy of the loss spectrum, and the position of this plasmon peak is highly dependent on hydrogen concentration into silicon. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. The Development of Environmental Barrier Coatings for SiCSiC Ceramic Matrix Composites: Challenges and Opportunities

    Science.gov (United States)

    Zhu, Dongming

    2014-01-01

    Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is a key to enable the applications of the envisioned CMC components to help achieve next generation engine performance and durability goals. This paper will primarily address the performance requirements and design considerations of environmental barrier coatings for turbine engine applications. The emphasis is placed on current candidate environmental barrier coating systems for SiCSiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing advanced environmental barrier coating systems, the coating integrations with next generation CMC turbine components having improved environmental stability, cyclic durability and system performance will be described. The development trends for turbine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be discussed.

  8. Influence of wavelength on laser doping and laser-fired contact processes for c-Si solar cells

    Science.gov (United States)

    Molpeceres, Carlos; Sánchez-Aniorte, María. Isabel; Morales, Miguel; Muñoz, David; Martín, Isidro; Ortega, Pablo; Colina, Mónica; Voz, Cristóbal; Alcubilla, Ramón

    2012-10-01

    This work investigates the influence of the laser wavelength on laser doping (LD) and laser-fired contact (LFC) formation in solar cell structures. We compare the results obtained using the three first harmonics (corresponding to wavelengths of 1064 nm, 532 nm and 355 nm) of fully commercial solid state laser sources with pulse width in the ns range. The discussion is based on the impact on the morphology and electrical characteristics of test structures. In the case of LFC the study includes the influence of different passivation layers and the assessment of the process quality through electrical resistance measurements of an aluminium single LFC point for the different wavelengths. Values for the normalized LFC resistance far below 1.0 mΩcm2 have been obtained, with better results at shorter wavelengths. To assess the influence of the laser wavelength on LD we have created n+ regions into p-type c-Si wafers, using a dry LD approach to define punctual emitters. J-V characteristics show exponential trends at mid-injection for a broad parametric window in all wavelengths, with local ideality factors well below 1.5. In both processes the best results have been obtained using green (532 nm) and, specially, UV (355 nm). This indicates that to minimize the thermal damage in the material is a clear requisite to obtain the best electrical performance, thus indicating that UV laser shows better potential to be used in high efficiency solar cells.

  9. Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

    Directory of Open Access Journals (Sweden)

    Gema López

    2013-11-01

    Full Text Available The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx stacks on both p-type and n-type crystalline silicon (c-Si substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD to form anti-reflection coating (ARC stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (Seff,max was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

  10. Optical telescopes for COMPASS RICH1 up-grade

    CERN Document Server

    Sulc, M; Alekseev, M; Angerer, H; Appolonio, M; Birsa, R; Bordalo, P; Bradamante, F; Bressan, A; Busso, L; Chiosso, V M; Ciliberti, P; Colantoni, M L; Costa, S; Dibiase, N; Dafni, T; Dalla Torre, S; Diaz, V; Duic, V; Delagnes, E; Deschamps, H; Eyrich, W; Faso, D; Ferrero, A; Finger, M; Finger, M Jr; Fischer, H; Gerassimov, S; Giorgi, M; Gobbo, B; Hagemann, R; von Harrach, D; Heinsius, F H; Joosten, R; Ketzer, B; Königsmann, K; Kolosov, V N; Konorov, I; Kramer, D; Kunne, F; Levorato, S; Maggiora, A; Magnon, A; Mann, A; Martin, A; Menon, G; Mutter, A; Nähle, O; Neyret, D; Nerling, F; Pagano, P; Paul, S; Panebianco, S; Panzieri, D; Pesaro, G; Pizzolotto, C; Polak, J; Rebourgeard, P; Rocco, E; Robinet, F; Schiavon, P; Schill, C; Schoenmeier, P; Silva, L; Slunecka, M; Steiger, L; Sozzi, F; Svec, M; Tessarotto, F; Teufel, A; Wollny, H

    2006-01-01

    The central photon detection area of the Ring Imaging Cherenkov detector at COMPASS, a particle physics experiment at CERN SPS dedicated to hadron physics, has been upgraded from the previous system formed by wire chambers with CsI layers to a very fast UV extended multi anode photo multiplier tube array (MAPMT), including 576 tubes. The active area covered by the MAPMTs is 7.3 times smaller than the one previously equipped with CsI photocathodes, so 576 optical concentrators transforming the image from the old system focal plane to the new photocathode plane were needed. The telescope system formed by two fused silica lenses was designed, produced and assembled. The first prismatic plano-convex field lens is placed in the focal plane of the RICH mirrors. The second condenser lens is off centered and tilted and has one aspherical surface. All lenses have antireflection coating.

  11. Effects of Laser Pulse Heating of Copper Photocathodes on High-brightness Electron Beam Production at Blowout Regime

    CERN Document Server

    Zheng, Lianmin; Tang, Chuanxiang; Gai, Wei

    2016-01-01

    Producing high-brightness and high-charge (>100 pC) electron bunches at blowout regime requires ultrashort laser pulse with high fluence. The effects of laser pulse heating of the copper photocathode are analyzed in this paper. The electron and lattice temperature is calculated using an improved two-temperature model, and an extended Dowell-Schmerge model is employed to calculate the thermal emittance and quantum efficiency. A time-dependent growth of the thermal emittance and the quantum efficiency is observed. For a fixed amount of charge, the projected thermal emittance increases with the decreasing laser radius, and this effect should be taken into account in the laser optimization at blowout regime. Moreover, laser damage threshold fluence is simulated, showing that the maximum local fluence should be less than 40 mJ/cm^2 to prevent damage to the cathode. The cryogenic effect on the laser pulse heating is studied, showing that the hazards caused by the laser pulse heating will be significantly mitigated ...

  12. Growth of poly-crystalline Cu films on Y substrates by picosecond pulsed laser deposition for photocathode applications

    Energy Technology Data Exchange (ETDEWEB)

    Gontad, F. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Lorusso, A., E-mail: antonella.lorusso@le.infn.it [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Klini, A.; Manousaki, A. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), 100 N. Plastira St., GR 70013 Heraklion, Crete (Greece); Perrone, A. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Fotakis, C. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), 100 N. Plastira St., GR 70013 Heraklion, Crete (Greece)

    2015-11-01

    In this work, the deposition of Cu thin films on Y substrates for photocathode applications by pulsed laser deposition employing picosecond laser pulses is reported and compared with the use of nanosecond pulses. The influence of power density (6–50 GW/cm{sup 2}) on the ablation of the target material, as well as on the properties of the resulting film, is discussed. The material transfer from the target to the substrate surface was found to be rather efficient, in comparison to nanosecond ablation, leading to the growth of films with high thickness. Scanning electron microscope analysis indicated a quasi-continuous film morphology, at low power density values, becoming granular with increasing power density. The structural investigation, through X-ray diffraction, revealed the poly-crystalline nature of the films, with a preferential growth along the (111) crystallographic orientation of Cu cubic network. Finally, energy-dispersive X-ray spectroscopy showed a low contamination level of the grown films, demonstrating the potential of a PLD technique for the fabrication of Cu/Y patterned structures, with applications in radiofrequency electron gun technology. - Highlights: • Cu thin films were successfully deposited on Y substrates through ultrafast PLD. • The film presents a quasi-continuous morphology. • The use of picosecond pulses increases the film thickness. • The Cu thin films are very adherent to the Y substrate.

  13. Growth of poly-crystalline Cu films on Y substrates by picosecond pulsed laser deposition for photocathode applications

    Science.gov (United States)

    Gontad, F.; Lorusso, A.; Klini, A.; Manousaki, A.; Perrone, A.; Fotakis, C.

    2015-11-01

    In this work, the deposition of Cu thin films on Y substrates for photocathode applications by pulsed laser deposition employing picosecond laser pulses is reported and compared with the use of nanosecond pulses. The influence of power density (6-50 GW/cm2) on the ablation of the target material, as well as on the properties of the resulting film, is discussed. The material transfer from the target to the substrate surface was found to be rather efficient, in comparison to nanosecond ablation, leading to the growth of films with high thickness. Scanning electron microscope analysis indicated a quasi-continuous film morphology, at low power density values, becoming granular with increasing power density. The structural investigation, through X-ray diffraction, revealed the poly-crystalline nature of the films, with a preferential growth along the (111) crystallographic orientation of Cu cubic network. Finally, energy-dispersive X-ray spectroscopy showed a low contamination level of the grown films, demonstrating the potential of a PLD technique for the fabrication of Cu/Y patterned structures, with applications in radiofrequency electron gun technology.

  14. Ultra-fast pulse radiolysis system combined with a laser photocathode RF gun and a femtosecond laser

    CERN Document Server

    Muroya, Y; Watanabe, T; Wu, G; Kobayashi, T; Yoshii, K; Ueda, T; Uesaka, M; Katsumura, Y

    2002-01-01

    In order to study the early events in radiation physics and chemistry, two kinds of new pulse radiolysis systems with higher time resolution based on pump-and-probe method have been developed at the Nuclear Engineering Research Laboratory, the University of Tokyo. The first one, a few picosecond (2 ps at FWHM) electron beam (pump) from an 18 MeV S-band Linac using a laser photocathode RF gun (BNL/KEK/SHI type: GUN IV) was operated with a femtosecond laser pulse (100 fs at FWHM), which also acted as the analyzing light (probe). The synchronization precision between the pump and the probe was 1.7 ps (rms). In a 1.0 cm sample cell, a time resolution of 12 ps was achieved. The second one, a picosecond (4 ps at FWHM) electron pulse from a 35 MeV S-band Linac employing a conventional thermionic gun with a sub-harmonic buncher, was synchronized with the femtosecond laser pulse, with a synchronization jitter of 2.8 ps (rms). A time resolution of 22 ps was obtained with 2 cm cell. This makes it possible to do the puls...

  15. Comparison treatment planning with the measured change the dose of each junction section according to the error of setup CSI treatment with conventional, IMRT, VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Jin; Jeon, Chang Woo; Ahn, Bum Suk; Yu, Sool Hyeon; Park, So Yeon [Dept. of Radiation Oncology, Seoul University hospital, Seoul (Korea, Republic of)

    2014-12-15

    Conventional, IMRT, at CSI treatment with VMAT, this study compare the treatment plan with dose changes measured at Junction field according to the error of Setup. This study established Conventional, the IMRT, VMAT treatment planning for CSI therapy using the Eclipse 10.0 (Eclipse10.0, Varian, USA) and chose person in Seoul National University Hospital. Verification plan was also created to apply IMRT QA phantom for each treatment plan to the film measurements. At this time, the error of Setup was applied to the 2, 4, 6mm respectively with the head and foot direction. ('+' direction of the head, '-' means that the foot direction.) Using IMRT QA Phantom and EBT2 film, was investigated by placing the error of Setup for each Junction. We check the consistency of the measured Film and plan dose distribution by gamma index (Gamma index, gamma). In addition, we compared the error of Setup by the dose distribution, and analyzing the uniformity of the dose distribution within the target by calculating the Homogeneity Index (HI). It was figured out that 90.49%-gamma index we obtained with film is agreement with film scan score and dose distribution of treatment plan. Also, depend on the dose distribution on distance, if we make the error of Setup 2, 4, 6mm in the head direction, it showed that 3.1, 4.5, 8.1 at *Diff(%) of Conventional, 1.1, 3.5, 6.3 at IMRT, and 1.6, 2.5, 5.7 at VMAT. In the same way, if we make the error of Setup 2, 4, 6mm in the foot direction, it showed that -1.6, -2.8, -4.4 at *Diff(%) of Conventional, -0.9, -1.6, -2.9 at IMRT, and -0.5, -2.2, -2.5 at VMAT. Homogeneity Index(HI)s are 1.216 at Conventional, 1.095 at IMRT and 1.069 at VMAT. The dose-change depend on the error of Setup at the CSI RT(radiation therapy) using IMRT and VMAT which have advantages, Dose homogeneity and the gradual dose gradients on the Junction part is lower than that of Conventional CSI RT. This a little change of dose means that there is less danger on

  16. Precoding Design of MIMO Amplify-and-Forward Communication System With an Energy Harvesting Relay and Possibly Imperfect CSI

    KAUST Repository

    Benkhelifa, Fatma

    2017-03-02

    In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) in a Multiple-Input Multiple-Output (MIMO) Amplify-and-Forward (AF) relay communication system where the relay is an energy harvesting (EH) node and harvests the energy the signals transmitted from the source. The harvested energy is partially used to forward signals from the source to the destination, and the remaining energy is stored for other usages. The SWIPT in relay-assisted communication is interesting as long as the relay stores energy from the source and the destination receives successfully the data from the source. In this context, we propose to investigate the source and relay precoders that characterize the relationship between the achievable stored energy at the relay and the achievable sourceto- destination rate, namely the rate-stored energy (R-E) tradeo region. First, we consider the ideal scheme where there is the simultaneous operation of the EH and ID receivers at the relay. Then, we consider practical schemes such as the power splitting (PS) and the time switching (TS) that separate the operation of EH and information decoding (ID) receivers over power domain or time domain, respectively. Moreover, we study the case of imperfect channel state information (CSI) at the relay and the destination and characterize its impact on the achievable R-E region. Through the simulation results, we show the eect of the position of the relay and the channel uncertainty on the achievable R-E regions of all the schemes when the used energy at the relay is constant or variable. We also show that, although it provides an outer bound on the achievable rate-energy region in one-hop MIMO systems, the ideal scheme provides only an upper bound on the maximum achievable end-to-end rate and not an outer bound on the R-E region.

  17. Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions.

    Science.gov (United States)

    Cheng, Chih-Hsien; Tzou, An-Jye; Chang, Jung-Hung; Chi, Yu-Chieh; Lin, Yung-Hsiang; Shih, Min-Hsiung; Lee, Chao-Kuei; Wu, Chih-I; Kuo, Hao-Chung; Chang, Chun-Yen; Lin, Gong-Ru

    2016-01-22

    The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC(1-x)) buffer is demonstrated. The a-SixC(1-x) buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC(1-x) buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC(1-x) buffer. The C-rich SixC(1-x) favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC(1-x) buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC(1-x) buffer, the device deposited on C-rich SixC(1-x) buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively.

  18. Moments Based Framework for Performance Analysis of One-Way/Two-Way CSI-Assisted AF Relaying

    KAUST Repository

    Xia, Minghua

    2012-09-01

    When analyzing system performance of conventional one-way relaying or advanced two-way relaying, these two techniques are always dealt with separately and, thus, their performance cannot be compared efficiently. Moreover, for ease of mathematical tractability, channels considered in such studies are generally assumed to be subject to Rayleigh fading or to be Nakagami-$m$ channels with integer fading parameters, which is impractical in typical urban environments. In this paper, we propose a unified moments-based framework for general performance analysis of channel-state-information (CSI) assisted amplify-and-forward (AF) relaying systems. The framework is applicable to both one-way and two-way relaying over arbitrary Nakagami-$m$ fading channels, and it includes previously reported results as special cases. Specifically, the mathematical framework is firstly developed under the umbrella of the weighted harmonic mean of two Gamma-distributed variables in conjunction with the theory of Pad\\\\\\'e approximants. Then, general expressions for the received signal-to-noise ratios of the users in one-way/two-way relaying systems and the corresponding moments, moment generation function, and cumulative density function are established. Subsequently, the mathematical framework is applied to analyze, compare, and gain insights into system performance of one-way and two-way relaying techniques, in terms of outage probability, average symbol error probability, and achievable data rate. All analytical results are corroborated by simulation results as well as previously reported results whenever available, and they are shown to be efficient tools to evaluate and compare system performance of one-way and two-way relaying.

  19. Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst

    Science.gov (United States)

    Qi, Huan; Wolfe, Jonathan; Fichou, Denis; Chen, Zhong

    2016-08-01

    Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light. A wide spectrum of LDHs can be easily prepared on demand by tuning their chemical composition and structural morphology. We describe here the electrochemical growth of NiFe-LDH overlayers on Cu2O electrodes and study their PEC behavior. By using the modified Cu2O/NiFe-LDH electrodes we observe a remarkable seven-fold increase of the photocurrent intensity under an applied voltage as low as -0.2 V vs Ag/AgCl. The origin of such a pronounced effect is the improved electron transfer towards the electrolyte brought by the NiFe-LDH overlayer due to an appropriate energy level alignment. Long-term photostability tests reveal that Cu2O/NiFe-LDH photocathodes show no photocurrent loss after 40 hours of operation under light at -0.2 V vs Ag/AgCl low bias condition. These improved performances make Cu2O/NiFe-LDH a suitable photocathode material for low voltage H2 production. Indeed, after 8 hours of H2 production under -0.2 V vs Ag/AgCl the PEC cell delivers a 78% faradaic efficiency. This unprecedented use of Cu2O/NiFe-LDH as an efficient photocathode opens new perspectives in view of low biasd or self-biased PEC water splitting under sunlight illumination.

  20. Double junction photoelectrochemical solar cells based on Cu2ZnSnS4/Cu2ZnSnSe4 thin film as composite photocathode

    Science.gov (United States)

    Zhu, L.; Qiang, Y. H.; Zhao, Y. L.; Gu, X. Q.

    2014-02-01

    A solvothermal method was used to synthesize Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles. CZTS/CZTSe bilayer films have been fabricated via a layer-by-layer blade coating process on the fluorine dope tin oxide (FTO) substrates. We converted conventional dye-sensitized solar cells (DSSCs) into double junction photoelectrochemical solar cells with the replacement of the Pt-coated counter electrode with the as-prepared films as composite photocathodes. Compared with conventional DSSCs, the cells show an increased short circuit current and power conversion efficiency.

  1. Detection of single photons with THickGEM-based counters

    Energy Technology Data Exchange (ETDEWEB)

    Alexeev, M. [INFN, Sezione di Torino and University of East Piemonte, Alessandria (Italy); Barbosa, F. [I3N - Physics Department, University of Aveiro (Portugal); Birsa, R. [INFN, Sezione di Trieste, Trieste (Italy); Bradamante, F.; Bressan, A. [INFN, Sezione di Trieste and University of Trieste, Trieste (Italy); Chiosso, M. [INFN, Sezione di Torino and University of Torino, Torino (Italy); Ciliberti, P. [INFN, Sezione di Trieste and University of Trieste, Trieste (Italy); Dalla Torre, S. [INFN, Sezione di Trieste, Trieste (Italy); Denisov, O. [INFN, Sezione di Torino, Torino (Italy); Duic, V. [INFN, Sezione di Trieste and University of Trieste, Trieste (Italy); Ferrero, A. [INFN, Sezione di Torino and University of Torino, Torino (Italy); Finger, M.; Finger, M. [Charles University, Praga (Czech Republic); JINR, Dubna (Russian Federation); Fischer, H. [Universitaet Freiburg, Physikalisches Institut, Freiburg (Germany); Giorgi, M. [INFN, Sezione di Trieste and University of Trieste, Trieste (Italy); Gobbo, B.; Gregori, M. [INFN, Sezione di Trieste, Trieste (Italy); Heinsius, F.H.; Herrmann, F.; Koenigsmann, K. [Universitaet Freiburg, Physikalisches Institut, Freiburg (Germany); and others

    2012-12-11

    Cherenkov imaging counters requiring large photosensitive areas, the capability to stand high rates and to operate in magnetic field environments could benefit from the use of photon detectors based on THick Gaseous Electron Multiplier (THGEM) coupled to a solid state CsI photo-cathode. A systematic study of the THGEM detector response as a function of its geometrical parameters and electrodes' applied voltage has been performed. Dedicated electrostatic calculations to optimize the detector design have been accomplished. Data obtained from small photon detector prototypes operating in single photon detection mode are presented and discussed. In particular the key aspect of photo-electron extraction from the photo-cathode surface is investigated via the timing spectrum response of the detector for different electric field conditions at the photo-cathode: a comparison of the measured time distributions and the simulation results is illustrated.

  2. An Efficient CuxO Photocathode for Hydrogen Production at Neutral pH: New Insights from Combined Spectroscopy and Electrochemistry.

    Science.gov (United States)

    Baran, Tomasz; Wojtyła, Szymon; Lenardi, Cristina; Vertova, Alberto; Ghigna, Paolo; Achilli, Elisabetta; Fracchia, Martina; Rondinini, Sandra; Minguzzi, Alessandro

    2016-08-24

    Light-driven water splitting is one of the most promising approaches for using solar energy in light of more sustainable development. In this paper, a highly efficient p-type copper(II) oxide photocathode is studied. The material, prepared by thermal treatment of CuI nanoparticles, is initially partially reduced upon working conditions and soon reaches a stable form. Upon visible-light illumination, the material yields a photocurrent of 1.3 mA cm(-2) at a potential of 0.2 V vs a reversible hydrogen electrode at mild pH under illumination by AM 1.5 G and retains 30% of its photoactivity after 6 h. This represents an unprecedented result for a nonprotected Cu oxide photocathode at neutral pH. The photocurrent efficiency as a function of the applied potential was determined using scanning electrochemical microscopy. The material was characterized in terms of photoelectrochemical features; X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, fixed-energy X-ray absorption voltammetry, and extended X-ray absorption fine structure analyses were carried out on pristine and used samples, which were used to explain the photoelectrochemical behavior. The optical features of the oxide are evidenced by direct reflectance spectroscopy and fluorescence spectroscopy, and Mott-Schottky analysis at different pH values explains the exceptional activity at neutral pH.

  3. Interfacial band-edge engineered TiO2 protection layer on Cu2O photocathodes for efficient water reduction reaction

    Science.gov (United States)

    Choi, Jaesuk; Song, Jun Tae; Jang, Ho Seong; Choi, Min-Jae; Sim, Dong Min; Yim, Soonmin; Lim, Hunhee; Jung, Yeon Sik; Oh, Jihun

    2017-01-01

    Photoelectrochemical (PEC) water splitting has emerged as a potential pathway to produce sustainable and renewable chemical fuels. Here, we present a highly active Cu2O/TiO2 photocathode for H2 production by enhancing the interfacial band-edge energetics of the TiO2 layer, which is realized by controlling the fixed charge density of the TiO2 protection layer. The band-edge engineered Cu2O/TiO2 (where TiO2 was grown at 80 °C via atomic layer deposition) enhances the photocurrent density up to -2.04 mA/cm2 at 0 V vs. RHE under 1 sun illumination, corresponding to about a 1,200% enhancement compared to the photocurrent density of the photocathode protected with TiO2 grown at 150 °C. Moreover, band-edge engineering of the TiO2 protection layer prevents electron accumulation at the TiO2 layer and enhances both the Faraday efficiency and the stability for hydrogen production during the PEC water reduction reaction. This facile control over the TiO2/electrolyte interface will also provide new insight for designing highly efficient and stable protection layers for various other photoelectrodes such as Si, InP, and GaAs. [Figure not available: see fulltext.

  4. Carbon-shell-decorated p-semiconductor PbMoO4 nanocrystals for efficient and stable photocathode of photoelectrochemical water reduction

    Science.gov (United States)

    Wang, Ligang; Tang, Hanqin; Tian, Yang

    2016-07-01

    Photoelectrochemical (PEC) water splitting using semiconductors is a promising method for the future scalable production of renewable hydrogen fuels. The critical issues in PEC water splitting include the development of the photoelectrode materials with high efficiency and long-term stability, especially for p-type semiconductor photocathodes. Herein, we report the use of citric acid (CA) pyrolysis to prepare carbon-shell-decorated PbMoO4 (C@PbMoO4) nanocrystals via a simple solvothermal method. Different carbon shell thicknesses below 10 nm were generated by varying the amount of CA in the precursor solution. In contrast, without using CA, bare PbMoO4 nanocrystals were obtained. The PEC experiments showed that 2-nm carbon shell could preferably improve the water splitting performance of PbMoO4: the photocurrent density of 2-nm C@PbMoO4 is nearly 2-fold high as that of bare PbMoO4 at 0 V versus reversible hydrogen electrode (RHE). The surface charge transfer efficiency of 2-nm C@PbMoO4 in the PEC process was tested to increase from 83% to 90.4%, the charge separation efficiency enhanced 56%, and the PEC stability also greatly increased compared to those of the bare PbMoO4 nanocrystals. This strategy could be applied to other p-type semiconducting photocathodes for low-cost solar-fuel-generation devices.

  5. CSI: Hard Drive

    Science.gov (United States)

    Sturgeon, Julie

    2008-01-01

    Acting on information from students who reported seeing a classmate looking at inappropriate material on a school computer, school officials used forensics software to plunge the depths of the PC's hard drive, searching for evidence of improper activity. Images were found in a deleted Internet Explorer cache as well as deleted file space.…

  6. CSI : Kuhn and Latour

    OpenAIRE

    Fuller, Steve

    2012-01-01

    I have been always most moved by those whose views I have ended up opposing. I say\\ud 'ended up' because the views are typically ones in which I originally invested considerable\\ud study and interest. But then a version of the 'familiarity breeds contempt' principle\\ud sets in, and my intellectual immune system generates antibodies that ward off later, more\\ud virulent strains of such thinkers' thoughts. So fortified, I welcome the opportunity to\\ud reflect on the significance of Kuhn (1962) ...

  7. Extraction and separation of Nd(III), Sm(III), Dy(III), Fe(III), Ni(II), and Cs(I) from concentrated chloride solutions with N,N,N',N'-tetra(2-ethylhexyl) diglycolamide as new extractant

    Institute of Scientific and Technical Information of China (English)

    E.A. Mowafy; D. Mohamed

    2015-01-01

    The feasibility of using N,N,N',N'-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in 75 vol.% n-dodecane-25 vol.% n-octanol as agents for the extraction and separation of Nd(III), Sm(III), Dy(III), Fe(III), Ni(II), and Cs(I) from concentrated chlo-ride solution was investigated. Different extraction behaviors were obtained towards rare earth elements (REE) studied and Fe(III), Ni(II) and Cs(I). Efficient separation of Nd(III), Sm(III) and Dy(III) from Fe(III), Ni(II), and Cs(I) was achieved by TEHDGA, depending on the HCl, HNO3 or H2SO4 concentration. A systematic investigation was carried out on the detailed extraction prop-erties of Nd(III), Sm(III), and Dy(III) with TEHDGA from chloride media. The IR spectra of the extracted species were investi-gated.

  8. To Think and Watch the Evil: The Turn of the Screw as Cultural Reference in Television from Dark Shadows to C.S.I.

    Directory of Open Access Journals (Sweden)

    Anna Viola Sborgi

    2012-07-01

    Full Text Available Since its first publication, Henry James’s The Turn of the Screw (1898 has always haunted the imagination of artists (Benjamin Britten, Jack Clayton, Amenábar and has been widely used as a source for television narratives (Dan Curtis, US TV version starring Colin Firth, Tim Fywell. In serial productions, James’s story has been the object of extensive quotation and allusion, from the 1960 gothic soap opera Dark Shadows to the C.S.I. episode Turn of the Screw (Season 4, Episode 21. A milestone in literary history, the story now embodies a set of cultural references conveying different, complex meanings, which can only be disclosed in the light of contemporary forms of representing reality. The novella appeals to two apparently opposite tendencies in contemporary television: the morbid display of the real (C.S.I. and the quest for the supernatural (Buffy The Vampire Slayer, among others. A line can be traced from Dark Shadows, the show that pioneered the genre, to contemporary horror soaps about vampires and supernatural phenomena. This paper shows the ways in which James’ sophisticated novella makes its way through popular culture, and how its constant ambiguous, dilemmatic interplay between reality and imagination can be related to the double-sided drive of the contemporary public towards hyper-reality and the supernatural.

  9. CSI Empirical Research on Hainan E -Learning%海南网络高等教育顾客满意度实证研究

    Institute of Scientific and Technical Information of China (English)

    吴晓匀

    2011-01-01

    The development of e - learning in China is fast, but the low quality of the service has hindered its sustainable development. Students are the customers of e - learning services and the subjects of our e - learning quality evaluation. CSI ( customer satisfaction degree) is a method that is generally used for evaluating customer's satisfaction degree for e -learning service quality. Using learners in the open education in Hainan as the target, the paper makes an empirical research about CSI of Hainan e - learning service quality.%我国网络高等教育发展迅速,但在此领域中出现的服务质量问题影响了网络高等教育的可持续发展。学生是网络高等教育服务的直接顾客,学习者角色性质导致其成为网络高等教育质量评价的主体。服务业普遍用CSI(顾客满意度)测评来考量顾客对于服务质量的评价,这里以开放教育学员为对象,采用CSI测评方法对海南网络教育用户满意度进行实证研究。

  10. Law & Order, CSI, and NCIS: The Association Between Exposure to Crime Drama Franchises, Rape Myth Acceptance, and Sexual Consent Negotiation Among College Students.

    Science.gov (United States)

    Hust, Stacey J T; Marett, Emily Garrigues; Lei, Ming; Ren, Chunbo; Ran, Weina

    2015-01-01

    Previous research has identified that exposure to the crime drama genre lowers rape myth acceptance and increases sexual assault prevention behaviors such as bystander intervention. However, recent content analyses have revealed marked differences in the portrayal of sexual violence within the top three crime drama franchises. Using a survey of 313 college freshmen, this study explores the influence of exposure to the three most popular crime drama franchises: Law & Order, CSI, and NCIS. Findings indicate that exposure to the Law & Order franchise is associated with decreased rape myth acceptance and increased intentions to adhere to expressions of sexual consent and refuse unwanted sexual activity; whereas exposure to the CSI franchise is associated with decreased intentions to seek consent and decreased intentions to adhere to expressions of sexual consent. Exposure to the NCIS franchise was associated with decreased intentions to refuse unwanted sexual activity. These results indicate that exposure to the specific content of each crime drama franchise may have differential results on sexual consent negotiation behaviors.

  11. Microhydration of caesium compounds: Cs, CsOH, CsI and Cs₂I₂ complexes with one to three H₂O molecules of nuclear safety interest.

    Science.gov (United States)

    Sudolská, Mária; Cantrel, Laurent; Cernušák, Ivan

    2014-04-01

    Structure and thermodynamic properties (standard enthalpies of formation and Gibbs free energies) of hydrated caesium species of nuclear safety interest, Cs, CsOH, CsI and its dimer Cs₂I₂, with one up to three water molecules, are calculated to assess their possible existence in severe accident occurring to a pressurized water reactor. The calculations were performed using the coupled cluster theory including single, double and non-iterative triple substitutions (CCSD(T)) in conjunction with the basis sets (ANO-RCC) developed for scalar relativistic calculations. The second-order spin-free Douglas-Kroll-Hess Hamiltonian was used to account for the scalar relativistic effects. Thermodynamic properties obtained by these correlated ab initio calculations (entropies and thermal capacities at constant pressure as a function of temperature) are used in nuclear accident simulations using ASTEC/SOPHAEROS software. Interaction energies, standard enthalpies and Gibbs free energies of successive water molecules addition determine the ordering of the complexes. CsOH forms the most hydrated stable complexes followed by CsI, Cs₂I₂, and Cs. CsOH still exists in steam atmosphere even at quite high temperature, up to around 1100 K.

  12. Photocarrier Radiometry for Noncontact Evaluation of Monocrystalline Silicon (c-Si) Solar Cell Irradiated by 1 MeV Electron Beams

    Science.gov (United States)

    Song, P.; Liu, J. Y.; Yuan, H. M.; Wang, F.; Wang, Y.

    2016-08-01

    In this paper, the monocrystalline silicon (c-Si) solar cell irradiated by 1 MeV electron beams was investigated using noncontact photocarrier radiometry (PCR). A theoretical 1D two-layer PCR model including the impedance effect of the p-n junction was used to characterize the transport properties (carrier lifetime, diffusion coefficient, and surface recombination velocities) of c-Si solar cells irradiated by 1 MeV electron beams with different fluences. The carrier transport parameters were derived by the best fit through PCR measurements. Furthermore, an Ev+0.56 eV trap was introduced into the band gap based on the minority carrier lifetime reduction. An I-V characteristic was obtained by both AFORS-HET simulation and experimental study, and the simulation results shows in good agreement with the experimental results. Moreover, the simulation and experiment results also indicate that the increase of fluences of electron beams results in the reduction of short-circuit current and open-circuit voltage.

  13. Sources of Emittance in RF Photocathode Injectors: Intrinsic emittance, space charge forces due to non-uniformities, RF and solenoid effects

    CERN Document Server

    Dowell, David H

    2016-01-01

    Advances in electron beam technology have made possible the current generation of x-ray free electron lasers and electron microscopes. These devices have become valuable tools for basic research and applied science. An important technology related to xfels is the photocathode RF gun and injector. The invention of the RF gun and the developments of emittance compensation and beam matching were driving forces behind these new technologies. Achieving even brighter beams requires taking a finer resolution view of the electron dynamics near the cathode during emission and initial acceleration. In addition the bright beam is sensitive to optical aberrations in the injector's RF and magnetic lenses. This paper discusses these topics including beam properties due to cathode material properties, space charge effects close to the cathode and optical distortions of the RF and solenoid fields. Analytic relations for these phenomena are derived and compared with numerical simulations.

  14. Near Infrared (NIR) Imaging Techniques Using Lasers and Nonlinear Crystal Optical Parametric Oscillator/Amplifier (OPO/OPA) Imaging and Transferred Electron (TE) Photocathode Image Intensifiers

    Energy Technology Data Exchange (ETDEWEB)

    YATES,GEORGE J.; MCDONALD,THOMAS E. JR.; BLISS,DAVID E.; CAMERON,STEWART M.; GREIVES,KENNETH H.; ZUTAVERN,FRED J.

    2000-12-20

    Laboratory experiments utilizing different near-infrared (NIR) sensitive imaging techniques for LADAR range gated imaging at eye-safe wavelengths are presented. An OPO/OPA configuration incorporating a nonlinear crystal for wavelength conversion of 1.56 micron probe or broadcast laser light to 807 nm light by utilizing a second pump laser at 532 nm for gating and gain, was evaluated for sensitivity, resolution, and general image quality. These data are presented with similar test results obtained from an image intensifier based upon a transferred electron (TE) photocathode with high quantum efficiency (QE) in the 1-2 micron range, with a P-20 phosphor output screen. Data presented include range-gated imaging performance in a cloud chamber with varying optical attenuation of laser reflectance images.

  15. Near IR Photocathode Development

    Science.gov (United States)

    2007-11-02

    Electron Photoemission from InP", Appl. Phys. Letters, Vol. 25, No. 11, pp. 645 - 646, (1974). 11 J.S. Escher , R.L. Bell, P.E. Gregory, S.B. Hyder, T.J...Photomultiplier with Fast Time Response”, SPIE Vol. 2022, pp. 64 - 73, (1993). 14 J.S. Escher and R. Sankaran, "Transferred-electron Photoemission to 1.4 µm

  16. CSI-Chocolate Science Investigation and the Case of the Recipe Rip-Off: Using an Extended Problem-Based Scenario to Enhance High School Students' Science Engagement

    Science.gov (United States)

    Marle, Peter D.; Decker, Lisa; Taylor, Victoria; Fitzpatrick, Kathleen; Khaliqi, David; Owens, Janel E.; Henry, Renee M.

    2014-01-01

    This paper discusses a K-12/university collaboration in which students participated in a four-day scenario-based summer STEM (science, technology, engineering, and mathematics) camp aimed at making difficult scientific concepts salient. This scenario, Jumpstart STEM-CSI: Chocolate Science Investigation (JSCSI), used open- and guided-inquiry…

  17. Empirical Research on Hedging Efficiency Measures of CSI 300 Index Futures Based on CSI 300ETF%沪深300股指期货套期保值效率度量研究--基于沪深300 ETF的实证分析

    Institute of Scientific and Technical Information of China (English)

    王继莹; 郑耀威

    2014-01-01

    基于沪深300股指期货真实交易数据,选取对指数拟合程度高且可交易的沪深300ETF为现货研究对象,运用静态套期保值比率估计模型(OLS、B-VAR、VECM)和动态套期保值比率估计模型(VECM-BGARCH、DBEKK-GARCH、DCC-GARCH、NormCopula-GARCH、tCopula-GARCH)对最优套期保值比率进行估计,并对规避风险效果进行比较。结果表明:无论在样本内期间和样本外期间中,各模型反映出的沪深300股指期货套期保值效率都较高,考虑期货与现货市场动态相关性的NormCopula-GARCH 模型套期保值效果最优。%This paper selected CSI 300ETF which can fit CSI 300 index better and tradable as a spot research object,used the static hedging ratio estimation model (OLS,B-VAR,VECM)and the dynamic hedging ratio estimation model (VECM-BGARCH,DBEKK-GARCH,DCC-GARCH,Norm Copula-GARCH,tCopula-GARCH)to estimate the optimal hedging ratio based on actual transaction data of CSI 300 stock index futures.Furthermore,the hedging effectiveness of different models was tested and compared.The results showed that:both in the sample and out-sample period,the hedging effect by using CSI 300 index futures was good for each model.NormCopula-GARCH model that considering the dynamic correlation of futures and spot market has advantage of existing hedging ratio estimation models,it provides reference in the risk aversion for investors.

  18. CuInGaS2 photocathodes treated with SbX3 (X  =  Cl, I): the effect of the halide on solar water splitting performance

    Science.gov (United States)

    Guijarro, Néstor; Prévot, Mathieu S.; Johnson, Melissa; Yu, Xiaoyun; Bourée, Wiktor S.; Jeanbourquin, Xavier A.; Bornoz, Pauline; Le Formal, Florian; Sivula, Kevin

    2017-02-01

    The realization of photoelectrochemical tandem cells for efficient solar-to-hydrogen energy conversion is currently impeded by the lack of inexpensive, stable, and efficient photocathodes. The family of sulfide chalcopyrites (CuIn x Ga1-x S2) has recently demonstrated a remarkable stability and performance even when prepared by solution-based routes that potentially lower the cost of fabrication. However, the photovoltage delivered by the photocathodes is still well-below the attainable values, a classical limitation linked to a large density of surface states in these materials. In the present work, we show that the identity of halide present during the growth of the solution-processed CuIn0.3Ga0.7S2 (CIGS) thin-films governs the overall performance by directing the crystal growth and the passivation of surface states. Replacing chlorine by iodine leads to CIGS photocathodes that deliver photocurrents of 5 mA cm-2 (at 0 V versus RHE) and a turn-on voltage of 0.5 V versus RHE without charge extracting overlayer nor any sign of deterioration during stability test.

  19. SU-E-T-369: Evaluating Intensity Modulated Proton Therapy Relative to Passive Scattering Proton Therapy for Increased Vertebral Column Sparing in CSI of Pediatric Patients

    Energy Technology Data Exchange (ETDEWEB)

    Seco, J; Giantsoudi, D; Eaton, BR; Adams, JA; Paganetti, H; MacDonald, S [Harvard Medical School and Massachusetts General Hospital, Boston, MA (United States)

    2015-06-15

    Purpose: To investigate the trade-off between vertebral column sparing and thecal-sac target coverage in craniospinal irradiation (CSI) of pediatric patients treated with passive-scattering (PS) and intensity modulated (IMPT) proton therapy. Methods: We selected 2 pediatric patients treated with PS CSI for medulloblastoma. Spinal irradiation was re-planned with IMPT. For all cases, we assumed prescription dose of 23.4 Gy(RBE), with the spinal canal receiving at least 95% of 23.4 Gy(RBE). PS planning was performed using the commercial system XiO. IMPT planning was done using the Astroid planning system. Beam arrangements consisted of (a) PS posterior-anterior (PA) field, PS-PA, (b) IMPT PA field, IMPT-PA, and (c) two posterior oblique IMPT fields, IMPT2 (-35°, 35°). Dose distributions were re-calculated using TOPAS Monte Carlo, along with LET distributions, to investigate LET variations within the target and vertebra anatomy. Variable RBE-weighed dose distributions were also calculated based on a dose and LET-dependent biophysical model. Dosimetric data were compared among the plans for the target volume, spinal cord and adjacent critical organs (thecal-sac and cauda equina). Results: IMPT2 resulted in better sparing of the posterior vertebral column (entrance region posterior to thecal-sac), where planned dose was approximately 6–8Gy(RBE). For IMPT-PA and PS-PA the MC-calculated dose to the posterior vertebral column was, on average, 20Gy and 18Gy respectively. For IMPT2 higher mean-LET (5keV/µm/(g/cm3)) values were observed in anterior vertebral column (beyond the thecal-sac) relative to IMPT-PA and PS-PA, where mean-LET was 3.5keV/µm/(g/cm3) and 2.5keV/µm/(g/cm3) respectively. The higher LET region observed for both IMPT plans was in the distal end of treatment fields, where dose delivered was less 5Gy(RBE). Conclusion: The two-oblique proton beams IMPT2 best spared the spinal column, while reducing the dose to the posterior spinal column from 18–20 to 6

  20. Analysis of the iodine gas phase produced by interaction of CsI and MoO{sub 3} vapours in flowing steam

    Energy Technology Data Exchange (ETDEWEB)

    Gouello, M. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES/SEREX/L2EC, PSN-RES/SAG/LETR, Cadarache, St. Paul-lez-Durance 13115 (France); Mutelle, H., E-mail: herve.mutelle@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES/SEREX/L2EC, PSN-RES/SAG/LETR, Cadarache, St. Paul-lez-Durance 13115 (France); Cousin, F. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES/SEREX/L2EC, PSN-RES/SAG/LETR, Cadarache, St. Paul-lez-Durance 13115 (France); Sobanska, S. [Laboratoire de Spectrochimie IR et Raman, UMR-CNRS 8516, CERLA FR-CNRS 2416 Université de Lille 1, 59655 Villeneuve d’Ascq (France); Blanquet, E. [Laboratoire de Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 1130 rue de la Piscine, 38402 St. Martin d’Heres (France)

    2013-10-15

    Highlights: • Reactions between MoO{sub 3} and CsI vapours in flowing steam produce gaseous iodine. • Fraction of gaseous iodine increases within a short range of the Mo/Cs molar ratio. • Caesium molybdates were identified under condensed form by Raman spectroscopy. • Iodine gas speciation is better accounted with a kinetically limited scheme. -- Abstract: In case of severe accident in a water-cooled nuclear reactor, the amount of gaseous iodine released from the primary circuit is of particular concern because it can have a direct impact on the short-term iodine source term to the environment. As revealed by the Phebus FPT tests, assessment of the iodine forms at the break is a complex issue that requires to take into account not only the thermal and flow conditions in the circuit but also the behaviour of several elements such as caesium and molybdenum involved in iodine chemistry at high temperature. Moreover, reactions between these elements and with the carrier gas could be kinetically-limited due to the low concentrations and the short residence time of the fission products in the primary circuit coupled to the strong thermal gradients encountered in this part of the reactor. In order to reduce the uncertainties in the fraction of gaseous iodine, experimental and modelling studies have been launched in the framework of the international CHIP program. The work presented in this paper is part of this program and aims to investigate the effect of molybdenum using an open flow reactor where MoO{sub 3} and CsI vapours are injected under steam/argon atmosphere. In these conditions, the experiments clearly demonstrate that molybdenum increases the fraction of gaseous iodine released at low temperature and show that this effect is highly sensitive to the Mo/Cs ratio. Caesium polymolybdates identified in the solid state by Raman microspectroscopy are consistent with the species of the Cs{sub 2}MoO{sub 4}–MoO{sub 3} diagram suggesting that some part of

  1. Enhanced Photocurrent Density by Spin-Coated NiO Photocathodes for N-Annulated Perylene-Based p-Type Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Li, Xing; Yu, Fengtao; Stappert, Sebastian; Li, Chen; Zhou, Ying; Yu, Ying; Li, Xin; Ågren, Hans; Hua, Jianli; Tian, He

    2016-08-03

    The low photocurrent density of p-type dye-sensitized solar cells (p-DSSCs) has limited the development of high-efficiency tandem cells due to the inadequate light-harvesting ability of sensitizers and the low hole mobility of semiconductors. Hereby, two new "push-pull" type organic dyes (PQ-1 and PQ-2) containing N-annulated perylene as electron donor have been synthesized, where the PQ-2-based p-DSSCs show higher photoelectric conversion efficiency (PCE) of 0.316% owing to the higher molar extinction compared to of that PQ-1. Additionally, the photocurrent densities were remarkably increased from 2.20 to 5.85 mA cm(-2) for PQ-1 and 2.45 to 6.69 mA cm(-2) for PQ-2 by spin-coated NiO photocathode based-p-DSSCs, respectively. This results are ascribed to the enhancement of hole transport rate, dye-loading amounts and transparency of NiO films in comparison to that prepared by screen-printing method. Electrochemical impedance spectroscopy and theoretical calculations studies indicate that the molecular dipole moment approaching closer to the NiO surface shifts the quasi-Fermi level to more positive levels, improving open-circuit voltage (Voc). Intensity-modulated photocurrent spectroscopy illustrates that the hole transit time in NiO films prepared in spin-coating is shorter than that prepared by screen-printing method.

  2. Experimental investigations on the influence of the photocathode laser pulse parameters on the electron bunch quality in an RF-photoelectron source

    Energy Technology Data Exchange (ETDEWEB)

    Haenel, Marc

    2010-07-15

    Free Electron Lasers based on the SASE principle like the European XFEL require electron bunches having peak currents of several kiloamperes as well as very low transverse emittance. While high peak currents can be generated using longitudinal bunch compression techniques, the transverse emittance must have values as low as 1mmmrad already at the source. The development of electron sources fulfilling these demanding specifications is the goal of the Photo Injector Test Facility (PITZ) in DESY, Zeuthen site. The key component of a photoinjector is the electron gun cavity where the electrons bunches are generated and immediately accelerated. The extraction of the electrons is based on the photoelectric effect of the cathode which requires a laser system having special capabilities. In the first part of the thesis, measurements are presented which were performed to investigate whether the laser and the laser transport system fulfill these requirements. The second part of the thesis is dedicated to simulations as well as experimental studies on the impact of the temporal and spatial parameters of the laser pulses on the electron bunch quality. This influence is possible because the response time of the Cs{sub 2}Te photocathode is short compared to the laser pulse duration. Based on these investigations, suggestions for improvements are given and tolerances for the laser pulse properties are defined. (orig.)

  3. Preparation of porous TiO{sub 2}/ZnO composite film and its photocathodic protection properties for 304 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongmei; Liu, Wei, E-mail: weiliu@ouc.edu.cn; Cao, Lixin; Su, Ge; Duan, Ruijing

    2014-05-01

    Highlights: • Porous TiO{sub 2}/ZnO composite films were prepared on the 304 stainless steel. • The preparation parameters of the composite films were optimized. • Porous TiO{sub 2}/ZnO composite films provide an effective photogenerated cathodic protection for 304 stainless steel. - Abstract: TiO{sub 2}/ZnO composite films with porous structure were prepared on the 304 stainless steel (304SS) by the sol-gel method and heating treatment. The crystalline phase and morphology of as-prepared TiO{sub 2}/ZnO composite films were characterized systematically by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet–visible (UV–vis) spectroscopy, respectively. The influences of Ti/Zn molar ratio and the annealing temperature on the photoelectric property of the samples have been investigated and their photocathodic protection performances for 304 stainless steel under dark and UV conditions have also been evaluated in 3.0% NaCl solution by the electrochemical measurements. The results indicate that porous TiO{sub 2}/ZnO composite film has a great enhancement of the light absorption and photoelectric property under UV illumination. This can be ascribed to the mutual effect of TiO{sub 2}/ZnO heterojunctions and the porous structures in the composite films, which provide a better photogenerated cathodic protection for 304SS.

  4. Preparation of porous TiO2/ZnO composite film and its photocathodic protection properties for 304 stainless steel

    Science.gov (United States)

    Xu, Hongmei; Liu, Wei; Cao, Lixin; Su, Ge; Duan, Ruijing

    2014-05-01

    TiO2/ZnO composite films with porous structure were prepared on the 304 stainless steel (304SS) by the sol-gel method and heating treatment. The crystalline phase and morphology of as-prepared TiO2/ZnO composite films were characterized systematically by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible (UV-vis) spectroscopy, respectively. The influences of Ti/Zn molar ratio and the annealing temperature on the photoelectric property of the samples have been investigated and their photocathodic protection performances for 304 stainless steel under dark and UV conditions have also been evaluated in 3.0% NaCl solution by the electrochemical measurements. The results indicate that porous TiO2/ZnO composite film has a great enhancement of the light absorption and photoelectric property under UV illumination. This can be ascribed to the mutual effect of TiO2/ZnO heterojunctions and the porous structures in the composite films, which provide a better photogenerated cathodic protection for 304SS.

  5. Studies on charge production from Cs2Te photocathodes in the PITZ L-band normal conducting radio frequency photo injector

    CERN Document Server

    Hernandez-Garcia, C; Asova, G; Bakr, M; Boonpornprasert, P; Good, J; Gross, M; Huck, H; Isaev, I; Kalantaryan, D; Khojoyan, M; Kourkafas, G; Lishilin, O; Malyutin, D; Melkumyan, D; Oppelt, A; Otevrel, M; Pathak, G; Renier, Y; Rublack, T; Stephan, F; Vashchenko, G; Zhao, Q

    2016-01-01

    This paper discusses the behavior of electron bunch charge produced in an L-band normal conducting radio frequency cavity (RF gun) from Cs2Te photocathodes illuminated with ps-long UV laser pulses when the laser transverse distribution consists of a flat-top core with Gaussian-like decaying halo. The produced charge shows a linear dependence at low laser pulse energies as expected in the quantum efficiency limited emission regime, while its dependence on laser pulse energy is observed to be much weaker for higher values, due to space charge limited emission. However, direct plug-in of experimental parameters into the space charge tracking code ASTRA yields lower output charge in the space charge limited regime compared to measured values. The rate of increase of the produced charge at high laser pulse energies close to the space charge limited emission regime seems to be proportional to the amount of halo present in the radial laser profile since the charge from the core has saturated already. By utilizing co...

  6. Mechanism Analysis of CsI Flicker Crystal on Photoelectric Detection Process%碘化铯闪烁晶体在光电检测过程中的机理分析

    Institute of Scientific and Technical Information of China (English)

    王菊霞

    2015-01-01

    简述了光电检测的基本原理,从电子辐射、能量分布、光电效应的角度分析了碘化铯在光电检测过程中的机理,研究表明:入射光强大约为0.1 MW/cm2时,碘化铯可形成双光子光电效应.碘化铯晶体是目前较为普遍使用的较好闪烁体,可将X射线直接转换为可见光,从而获得数字图像,实现光电检测的目的.%The fundamental principle of photoelectric detection is described. The mechanism of CsI crystal in the process of photoelectric detection is analyzed on the basis of represent electron emission, energy distribution and photoelectric effects. It is found that the two-photon photoelectric effect was obtained in CsI film for incident light intensity of about 0.1 MW/cm2 . The CsI is a fine flicker at large using which can be transform X-Ray to visible light in order to obtain figure image and realize photoelectric de⁃tection.

  7. The Stellar Mass - Halo Mass Relation for Low Mass X-ray Groups at 0.5CSI

    CERN Document Server

    Patel, Shannon G; Williams, Rik J; Mulchaey, John S; Dressler, Alan; McCarthy, Patrick J; Shectman, Stephen A

    2015-01-01

    Since z~1, the stellar mass density locked in low mass groups and clusters has grown by a factor of ~8. Here we make the first statistical measurements of the stellar mass content of low mass X-ray groups at 0.5CSI) spectroscopic redshift survey. Stars comprise ~3-4% of the total mass of group halos with masses 10^{12.8}

  8. GeS2-In2S3-CsI Chalcogenide Glasses Doped with Rare Earth Ions for Near- and Mid-IR Luminescence.

    Science.gov (United States)

    Li, Legang; Bian, Junyi; Jiao, Qing; Liu, Zijun; Dai, Shixun; Lin, Changgui

    2016-11-21

    Chalcogenide glass has been considered as a promising host for the potential laser gain and amplifier media operating in near- and mid-IR spectral region. In this work, the IR luminescence spectra of rare earth ions (Tm(3+), Er(3+), and Dy(3+)) doped 65GeS2-25In2S3-10CsI chalcogenide glasses were measured under the excitation of an 808 nm laser diode. To the best of our knowledge, it firstly provides the luminescence spectra of a full near- and mid-IR spectral range from 1 to 4 μm in rare earth ions doped chalcogenide glasses. The results of absorption spectra, luminescence spectra, and fluorescence decay curves were obtained in these samples with singly-, co- and triply-doping behaviors of Tm(3+), Er(3+), and Dy(3+) ions. In order to search possible efficient IR emissions, the luminescence behavior was investigated specifically with the variation of doping behaviors and dopant ions, especially in the samples co- and triply-doped active ions. The results suggest that favorable near- and mid-IR luminescence of rare earth ions can be further modified in chalcogenide glasses through an elaborated design of doping behavior and optically active ions.

  9. Mathematical Modeling of a Cs(I – Sr(II – Bentonite – Magnetite Sorption System, Simulating the Processes Taking Place in a Deep Geological Repository

    Directory of Open Access Journals (Sweden)

    H. Filipská

    2005-01-01

    Full Text Available The derivation of mathematical models of systems consisting of Cs(I or Sr(II and of bentonite (B, magnetite (M or their mixtures (B+M are described. The paper deals especially with modeling of the protonation and sorption processes occurring on the functional groups of the solid phase, namely on so called edge sites and layer sites. The two types of sites have different properties and, as a result, three types of Surface Complexation Models (SCM are used for edge sites, viz. two electrostatic SCMs: the Constant Capacitance Model (CCM and the Diffusion Double Layer Model (DLM, and one without electrostatic correction: the Chemical Model (CEM. The processes taking place on the layer sites are described by means of the Ion Exchange Model (IExM. In the course of modeling, the speciation of the given metal in the liquid (aqueous phase has to be taken into account. In principle, the model of protonation or sorption processes is based on the reactions occurring in the aqueous phase and on the surface of the solid phase, and comprises not only the equations of the equilibrium constants of the individual reactions, but also the mass and charge balance equations. The algorithm of the numerical solution is compatible with FAMULUS 3.5 (a Czech software product quite extensively used at Czech universities in the last decade, the bookcase codes of which are utilized. 

  10. Atomic Scale Understanding of Poly-Si/SiO2/c-Si Passivated Contacts: Passivation Degradation Due to Metallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Young, David; Lee, Benjamin; Nemeth, William; Harvey, Steve; Aoki, Toshihiro; Al-Jassim, Mowafak; Stradins, Paul

    2016-11-21

    The key attributes for achieving high efficiency crystalline silicon solar cells include class leading developments in the ability to approach the theoretical limits of silicon solar technology (29.4% efficiency). The push for high efficiency devices is further compounded with the clear need for passivation to reduce recombination at the metal contacts. At the same time there is stringent requirement to retain the same material device quality, surface passivation, and performance characteristics following subsequent processing. The development of passivated silicon cell structures that retain active front and rear surface passivation and overall material cell quality is therefore a relevant and active area of development. To address the potential outcomes of metallization on passivated silicon stack, we report on some common microstructural features of degradation due to metallization for a series of silicon device stacks. A fundamental materials understanding of the metallization process on retaining high-efficiency passivated Si devices is therefore gained over these series of results.

  11. MRI and 2D-CSI MR spectroscopy of the brain in the evaluation of patients with acute onset of neuropsychiatric systemic lupus erythematosus

    Energy Technology Data Exchange (ETDEWEB)

    Sundgren, P.C.; Jennings, J.; Gebarski, S.; Pang, Y.; Maly, P. [University of Michigan Health Systems, Department of Radiology, Ann Arbor, MI (United States); Attwood, J.T.; McCune, W.J. [University of Michigan Health Systems, Department of and Rheumatology, Ann Arbor, MI (United States); Nan, B. [University of Michigan Health Systems, School of Public Health, Ann Arbor, MI (United States)

    2005-08-01

    MRI and 2D-CSI spectroscopy were performed in eight patients with systemic lupus erythematosus who presented with acute onset of neuropsychiatric lupus (NP-SLE), and in seven normal controls to evaluate for differences in metabolic peaks and metabolic ratios between the two groups. Also, the interval change of the metabolic peaks and their ratios during treatment in the NP-SLE patient group was evaluated. Metabolic peaks for N-acetyl-aspartate (NAA), choline (Cho), creatine (Cr), and lactate/lipids (LL) and their ratios (NAA/Cr, NAA/Cho, Cho/Cr, LL/Cr) were determined at initial presentation and 3 and 6 months later. In the eight lupus patients compared to the seven normal controls, NAA/Cho ratios were lower at presentation (1.05 vs 1.25; p = 0.004) and decreased even further at the three month follow-up (0.92 vs 1.05; p = 0.008). In contrast, both Cho/Cr (1.42 vs 1.26; p = 0.026) and LL/Cr ratios (0.26 vs 0.19; p = 0.002) were higher in the lupus patients at presentation compared to the controls and did not significantly change at three and six months follow-up. The NAA/Cr ratios were lower in the lupus patients compared to the controls at presentation but the difference was not statistically significant. However, the mean NAA/Cr significantly decreased from the initial examination to the three month follow-up (1.42 vs 1.32; p = 0.049) but did not significantly change from the three to the six month follow-up examinations. The NAA/Cr, Cho/Cr, and NAA/Cho ratios varied significantly (p < 0.05, p < 0.05, p < 0.05, respectively) between the 17 different locations measured in the brain in all eight patients and seven controls. Both the NAA/Cr ratios and the Cho/Cr ratios were also significantly lower in the gray matter than in the white matter (p < 0.0001) in both patients and controls, whereas the LL/Cr and NAA/Cho ratios were not significantly different. In conclusion, 2D-CSI MR spectroscopy may be useful in the early detection of metabolic CNS changes in NP

  12. Detection of Degradation Effects in Field-Aged c-Si Solar Cells through IR Thermography and Digital Image Processing

    Directory of Open Access Journals (Sweden)

    E. Kaplani

    2012-01-01

    Full Text Available Due to the vast expansion of photovoltaic (PV module production nowadays, a great interest is shown in factors affecting PV performance and efficiency under real conditions. Particular attention is being given to degradation effects of PV cells and modules, which during the last decade are seen to be responsible for significant power losses observed in PV systems. This paper presents and analyses degradation effects observed in severely EVA discoloured PV cells from field-aged modules operating already for 18–22 years. Temperature degradation effects are identified through IR thermography in bus bars, contact solder bonds, blisters, hot spots, and hot areas. I-V curve analysis results showed an agreement between the source of electrical performance degradation and the degradation effects in the defected cell identified by the IR thermography. Finally, an algorithm was developed to automatically detect EVA discoloration in PV cells through processing of the digital image alone in a way closely imitating human perception of color. This nondestructive and noncostly solution could be applied in the detection of EVA discoloration in existing PV installations and the automatic monitoring and remote inspection of PV systems.

  13. Thickness effect on the formation of SiC nanoparticles in sandwiched Si/C/Si and C/Si multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Chung, C.K., E-mail: ckchung@mail.ncku.edu.t [Department of Mechanical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, 701, Taiwan (China); Wu, B.H.; Chen, T.S.; Peng, C.C.; Lai, C.W. [Department of Mechanical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, 701, Taiwan (China)

    2009-08-31

    The effect of carbon (C) and amorphous silicon (a-Si) thicknesses on the formation of SiC nanoparticles (np-SiC) in sandwiched Si/C/Si and C/Si multilayers on Si(100) substrates were investigated using ultra-high-vacuum ion beam sputtering system and vacuum thermal annealing at 500, 700, 900 {sup o}C for 1.0 h. Three-layer a-Si/C/a-Si structures with thicknesses of 50/200/50 nm and 75/150/75 nm and a two-layer C/a-Si structure of 200/50 nm were examined in this study. The size and density of np-SiC were strongly influenced by the annealing temperature, a-Si thickness and layer number. Many np-SiC appeared at 900 {sup o}C at a density order about 10{sup 8} cm{sup -2} in both three-layer structures while no particles formed in the two-layer structure. The thick a-Si structure (75/150/75 nm) produces a particle density approximately 1.8 times higher than thin structure (50/200/50 nm). This implies that thick a-Si structure had a lower activation energy of SiC formation compared to the thin a-Si structure. Few particles were found at 700 {sup o}C and no particles at 500 {sup o}C in both three-layer structures. The np-SiC formation is a thermally activated reaction. The higher temperature leads to higher particle density. A mechanism of np-SiC formation in thermodynamic and kinetic viewpoints is proposed.

  14. THE STELLAR MASS–HALO MASS RELATION FOR LOW-MASS X-RAY GROUPS AT 0.5< z< 1 IN THE CDFS WITH CSI

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.; Mulchaey, John S.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A., E-mail: patel@obs.carnegiescience.edu [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2015-01-30

    Since z∼1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ∼8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5CSI) spectroscopic redshift survey. Stars comprise ∼3%–4% of the total mass of group halos with masses 10{sup 12.8}

  15. Boosting the photocurrent density of p-type solar cells based on organometal halide perovskite-sensitized mesoporous NiO photocathodes.

    Science.gov (United States)

    Wang, Huan; Zeng, Xianwei; Huang, Zhanfeng; Zhang, Wenjun; Qiao, Xianfeng; Hu, Bin; Zou, Xiaoping; Wang, Mingkui; Cheng, Yi-Bing; Chen, Wei

    2014-08-13

    The p-n tandem design of a sensitized solar cell is a novel concept holding the potential to overcome the efficiency limitation of conventional single-junction sensitized solar cells. Significant improvement of the photocurrent density (Jsc) of the p-type half-cell is a prerequisite for the realization of a highly efficient p-n tandem cell in the future. This study has demonstrated effective photocathodes based on novel organometal halide perovskite-sensitized mesoporous NiO in liquid-electrolyte-based p-type solar cells. An acceptably high Jsc up to 9.47 mA cm(-2) and efficiency up to 0.71% have been achieved on the basis of the CH3NH3PbI3/NiO solar cell at 100 mW cm(-2) light intensity, which are significantly higher than those of any previously reported liquid-electrolyte-based p-type solar cells based on sensitizers of organic dyes or inorganic quantum dots. The dense blocking layer made by spray pyrolysis of nickel acetylacetonate holds the key to determining the current flow direction of the solar cells. High hole injection efficiency at the perovskite/NiO interface and high hole collection efficiency through the mesoporous NiO network have been proved by time-resolved photoluminescence and transient photocurrent/photovoltage decay measurements. The limitation of these p-type solar cells primarily rests with the adverse light absorption by the NiO mesoporous film; the secondary limitation arises from the highly viscous ethyl acetate-based electrolyte, which is helpful for the solar cell stability but hinders fluent diffusion into the pore channels, giving rise to a nonlinear dependence of Jsc on the light intensity.

  16. Trends in the development of large area photon detectors for Cherenkov light imaging applications

    CERN Document Server

    Nappi, E

    2003-01-01

    Since the successful operations of hi-tech devices at OMEGA, DELPHI and SLD, the technique of Cherenkov light imaging has gone through an impressive and fruitful evolution driven by the conception of novel large area photon detectors. The well-assessed potentialities of thin CsI films, employed as reflective photoconverters in gas counters operated at atmospheric pressure, will be compared with the promising features of hybrid and multianode vacuum photomultipliers. Recently proposed single-photon gaseous detectors based on GEMs will also be reviewed.

  17. Developments on RICH detectors; Les developpements sur les detecteurs RICH

    Energy Technology Data Exchange (ETDEWEB)

    Besson, P.; Bourgeois, P. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee

    1996-12-31

    The RICH (ring imaging Cherenkov) detector which is dedicated to Cherenkov radiation detection is described. An improvement made by replacing photo sensible vapor with solid photocathode is studied. A RICH detector prototype with a CsI photocathode has been built in Saclay and used with Saturne. The first results are presented. (A.C.) 13 refs.

  18. Large-Area, UV-Optimized, Back-Illuminated Silicon Photomultiplier Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Existing photocathode-based technologies for visible and UV instruments lack sensitivity, are bulky, and have limited reliability. Solid-state silicon...

  19. Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation.

    Science.gov (United States)

    Jiang, Feng; Gunawan; Harada, Takashi; Kuang, Yongbo; Minegishi, Tsutomu; Domen, Kazunari; Ikeda, Shigeru

    2015-10-28

    An electrodeposited Cu2ZnSnS4 (CZTS) compact thin film modified with an In2S3/CdS double layer and Pt deposits (Pt/In2S3/CdS/CZTS) was used as a photocathode for water splitting of hydrogen production under simulated sunlight (AM 1.5G) radiation. Compared to platinized electrodes based on a bare CZTS film (Pt/CZTS) and a CZTS film modified with a CdS single layer (Pt/CdS/CZTS), the Pt/In2S3/CdS/CZTS electrode exhibited a significantly high cathodic photocurrent. Moreover, the coverage of the In2S3 layer was found to be effective for stabilization against degradation induced by photocorrosion of the CdS layer. Bias-free water splitting with a power conversion efficiency of 0.28% was achieved by using a simple two-electrode cell consisting of the Pt/In2S3/CdS/CZTS photocathode and a BiVO4 photoanode.

  20. Influence of solar spectrum and climate on the performance of c-SI, a-Si and CdTe modules

    Science.gov (United States)

    Weihs, Philipp; Jochen, Wagner; Marcus, Rennhofer; Zamini, Shokufeh; Fallent, Gerhard; Brence, Florian

    2010-05-01

    Within the scope of the project PV-SPEC we investigate the performance of different types of photovoltaic (PV) modules as a function of the regional climate of Austria. Three types of modules were chosen for the present study: monocrystalline silicon cells (c-SI), amorphous silicon cells (a-Si) and cadmium telluride cells (CdTe). The criteria for the selection of the cells is on the one hand their different spectral sensitivity and on the other hand the need of research in the domain of thin film technology. The aim of the project is the exact estimation of the potential energy yield of these three module types in the different climatic regions of Austria. Thereby the effects of the very inhomogeneous and structured topography in Austria need to be fully taken into account. As a first step the characteristics of the PV modules as well as their spectral sensitivity were determined in the laboratory. In a second step routine measurements of the module performance were performed at Observatory Kanzelhoehe (1600 m altitude), and in Vienna (170 m altitude). In order to investigate the influence of temperature, wind, cloudiness and solar spectrum some additional measurements of these quantities were performed. In order to investigate the influence of the orientation of the modules, we performed for each module type the measurement of the performance of three modules with different orientations: one module oriented towards south, one towards east and one towards west. In a third step we then analyse the performance as a function of time of the day, as a function of the season, as a function of the meteorological parameters (temperature, wind and cloudiness) and as a function of the spectral distribution of the solar radiation. The meteorological influence on the PV module performance is quantified using one array type function for each module type. Using this function and a radiative transfer model we may in a last step calculate the energy yield potential of the three PV

  1. Al2O3/SiON stack layers for effective surface passivation and anti-reflection of high efficiency n-type c-Si solar cells

    Science.gov (United States)

    Thi Thanh Nguyen, Huong; Balaji, Nagarajan; Park, Cheolmin; Triet, Nguyen Minh; Le, Anh Huy Tuan; Lee, Seunghwan; Jeon, Minhan; Oh, Donhyun; Dao, Vinh Ai; Yi, Junsin

    2017-02-01

    Excellent surface passivation and anti-reflection properties of double-stack layers is a prerequisite for high efficiency of n-type c-Si solar cells. The high positive fixed charge (Q f) density of N-rich hydrogenated amorphous silicon nitride (a-SiNx:H) films plays a poor role in boron emitter passivation. The more the refractive index ( n ) of a-SiNx:H is decreased, the more the positive Q f of a-SiNx:H is increased. Hydrogenated amorphous silicon oxynitride (SiON) films possess the properties of amorphous silicon oxide (a-SiOx) and a-SiNx:H with variable n and less positive Q f compared with a-SiNx:H. In this study, we investigated the passivation and anti-reflection properties of Al2O3/SiON stacks. Initially, a SiON layer was deposited by plasma enhanced chemical vapor deposition with variable n and its chemical composition was analyzed by Fourier transform infrared spectroscopy. Then, the SiON layer was deposited as a capping layer on a 10 nm thick Al2O3 layer, and the electrical and optical properties were analyzed. The SiON capping layer with n = 1.47 and a thickness of 70 nm resulted in an interface trap density of 4.74 = 1010 cm-2 eV-1 and Q f of -2.59 = 1012 cm-2 with a substantial improvement in lifetime of 1.52 ms after industrial firing. The incorporation of an Al2O3/SiON stack on the front side of the n-type solar cells results in an energy conversion efficiency of 18.34% compared to the one with Al2O3/a-SiNx:H showing 17.55% efficiency. The short circuit current density and open circuit voltage increase by up to 0.83 mA cm-2 and 12 mV, respectively, compared to the Al2O3/a-SiNx:H stack on the front side of the n-type solar cells due to the good anti-reflection and front side surface passivation.

  2. 沪深300ETF期现套利机会差异性实证分析%An Empirical Analysis of CSI 300 ETF Cash -Futures Arbitrage Opportunity Differentials

    Institute of Scientific and Technical Information of China (English)

    丁挺立

    2012-01-01

    This article compares the differential of the cost - of - carried arbitrage methodology and cointegra- tion - based statistical arbitrage strategy, and makes an empirical analysis on both ETFs. This research findings indicate that cointegration - based statistical arbitrage strategy has greater scope of applicability and enjoys a bigger arbitrage opportunity. This comes exactly with the same conclusion based on simulation trading data and other ETF statsits. Meanwhile, on the base of cointegration - based statistical arbitrage strategy, Huatai - PineBridge CSI 300 thus has a smaller chance to fulfill arbitrage,while Harvest CSI 300 enjoys a much bigger opportunity.%文章分析了持有成本套利方法与协整套利方法的优劣性,并基于沪深300ETF对两期现套利方法做了实证分析,结果发现:协整套利方法比持有成本套利法的适用范围更广,更能发掘套利机会。这与现有的基于仿真数据和其它ETF数据所得的结论一致。同时,基于协整套利方法发现,华泰柏瑞沪深300ETF的套利机会较小,而嘉实沪深300ETF的套利机会较大。

  3. Analog floating-point BiCMOS sampling chip and architecture of the BaBar CsI calorimeter front-end electronics system at the SLAC B-Factory

    Energy Technology Data Exchange (ETDEWEB)

    Haller, G.M.; Freytag, D.R. [Stanford Univ., CA (United States). Stanford Linear Accelerator Center

    1996-06-01

    The design and implementation of an analog floating-point sampling integrated circuit for the BaBar detector at the SLAC B-Factory is described. The CARE (Custom Auto-Range Encoding) circuit is part of an 18-bit dynamic range sampling system with a 4-MHz waveform digitization rate for the CsI calorimeter. The architecture and methodology of the system are described. The CARE integrated circuit receives dual-range (gain of 1 and 32) 13-bit signals from the 18-bit range preamplifiers mounted directly on the CsI crystals and converts the input at a rate of 4 MHz to an auto-range floating-point format with a 10-bit analog mantissa and 2 digital range bits (for 4 ranges). Additional functions integrated on the chip are averaging and selection circuitry for signals originating from two independent diodes per crystal and range-selection overwrite circuitry. The circuit will be mounted within the detector structure and thus low power dissipation is essential. The circuit has been fabricated in a 1.2 {micro}m BiCMOS process with polysilicon-to-polysilicon capacitors and polysilicon resistors. Measurement results are presented. One complete CARE channel dissipates 25 mW.

  4. Research on Surface Photovoltage Spectroscopy for Exponential Doping Transmission-Mode GaAs Photocathodes%指数掺杂透射式GaAs光电阴极表面光电压谱研究

    Institute of Scientific and Technical Information of China (English)

    陈亮; 钱芸生; 常本康; 张益军

    2011-01-01

    By solving the one-dimensional diffusion equation for equilibrium minority carriers of transmission-mode GaAs phtotocathodes, the equations for surface photovoltage spectroscopy of exponential and uniform doping transmission-mode GaAs photocathodes are deduced. Through metal organic chemistry vaporation deposition (MOCVD) technique, two GaAs photocathodes of different doping structures with the same active layer depth are designed. By measuring and theoretically emulating the surface photovoltage spectroscopy curves for two materials, the exponential doping structure can well increase the electric diffusion length for transmission-mode GaAs photocathodes. The reason is that the internal electric field can drive the photo-excited electrons to move toward surface barriers through both diffusing and electric field drifting, thus can finally elevate the emission efficiency and the surface photovoltage spectroscopy. The difference of two surface photovoltage spectroscopy waves can be well explained by the internal energy band equations and electron scattering theory.%通过求解一维稳态少数载流子扩散方程,推导了指数掺杂和均匀掺杂的透射式GaAs光电阴极表面光电压谱理论方程.利用金属有机化学气相沉积(MOCVD)外延生长了发射层厚度相同、掺杂结构不同的两款透射式阴极材料.通过表面光电压谱实验测试和理论拟合发现指数掺杂结构在发射层厚度和后界面复合速率相同的情况下能够有效提高阴极电子扩散长度,这主要由于内建电场能够促使光生电子通过扩散和电场漂移两种方式向表面运动,从而最终提升阴极的发射效率和表面光电压谱.利用能带计算公式和电子散射理论对这两种不同结构材料的表面光电压谱进行了详细分析.

  5. Low cost back contact heterojunction solar cells on thin c-Si wafers. integrating laser and thin film processing for improved manufacturability

    Energy Technology Data Exchange (ETDEWEB)

    Hegedus, Steven S. [Univ. of Delaware, Newark, DE (United States)

    2015-09-08

    An interdigitated back contact (IBC) Si wafer solar cell with deposited a-Si heterojunction (HJ) emitter and contacts is considered the ultimate single junction Si solar cell design. This was confirmed in 2014 by both Panasonic and Sharp Solar producing IBC-HJ cells breaking the previous record Si solar cell efficiency of 25%. But manufacturability at low cost is a concern for the complex IBC-HJ device structure. In this research program, our goals were to addressed the broad industry need for a high-efficiency c-Si cell that overcomes the dominant module cost barriers by 1) developing thin Si wafers synthesized by innovative, kerfless techniques; 2) integrating laser-based processing into most aspects of solar cell fabrication, ensuring high speed and low thermal budgets ; 3) developing an all back contact cell structure compatible with thin wafers using a simplified, low-temperature fabrication process; and 4) designing the contact patterning to enable simplified module assembly. There were a number of significant achievements from this 3 year program. Regarding the front surface, we developed and applied new method to characterize critical interface recombination parameters including interface defect density Dit and hole and electron capture cross-section for use as input for 2D simulation of the IBC cell to guide design and loss analysis. We optimized the antireflection and passivation properties of the front surface texture and a-Si/a-SiN/a-SiC stack depositions to obtain a very low (< 6 mA/cm2) front surface optical losses (reflection and absorption) while maintaining excellent surface passivation (SRV<5 cm/s). We worked with kerfless wafer manufacturers to apply defect-engineering techniques to improve bulk minority-carrier lifetime of thin kerfless wafers by both reducing initial impurities during growth and developing post-growth gettering techniques. This led insights about the kinetics of nickel, chromium, and dislocations in PV-grade silicon and to

  6. Low cost back contact heterojunction solar cells on thin c-Si wafers. Integrating laser and thin film processing for improved manufacturability

    Energy Technology Data Exchange (ETDEWEB)

    Hegedus, Steven S. [Univ. of Delaware, Newark, DE (United States)

    2015-09-08

    An interdigitated back contact (IBC) Si wafer solar cell with deposited a-Si heterojunction (HJ) emitter and contacts is considered the ultimate single junction Si solar cell design. This was confirmed in 2014 by both Panasonic and Sharp Solar producing IBC-HJ cells breaking the previous record Si solar cell efficiency of 25%. But manufacturability at low cost is a concern for the complex IBC-HJ device structure. In this research program, our goals were to addressed the broad industry need for a high-efficiency c-Si cell that overcomes the dominant module cost barriers by 1) developing thin Si wafers synthesized by innovative, kerfless techniques; 2) integrating laser-based processing into most aspects of solar cell fabrication, ensuring high speed and low thermal budgets ; 3) developing an all back contact cell structure compatible with thin wafers using a simplified, low-temperature fabrication process; and 4) designing the contact patterning to enable simplified module assembly. There were a number of significant achievements from this 3 year program. Regarding the front surface, we developed and applied new method to characterize critical interface recombination parameters including interface defect density Dit and hole and electron capture cross-section for use as input for 2D simulation of the IBC cell to guide design and loss analysis. We optimized the antireflection and passivation properties of the front surface texture and a-Si/a-SiN/a-SiC stack depositions to obtain a very low (< 6 mA/cm2) front surface optical losses (reflection and absorption) while maintaining excellent surface passivation (SRV<5 cm/s). We worked with kerfless wafer manufacturers to apply defect-engineering techniques to improve bulk minority-carrier lifetime of thin kerfless wafers by both reducing initial impurities during growth and developing post-growth gettering techniques. This led insights about the kinetics of nickel, chromium, and dislocations in PV-grade silicon and to

  7. 45kW CO2激光器大面积CSiB+NiMoCo合金化研究%Investigation on Large Area Laser Alloying of CSiB+NiMoCo by 45kW CO2 Laser

    Institute of Scientific and Technical Information of China (English)

    钟敏霖; Gous.,JC

    2000-01-01

    用45kW CO2激光器在XC38碳钢上激光合金化获得了表面光洁、无氧化和无裂纹缺陷的大面积合金化层.合金化区的微观组织由马氏体、残留奥氏体和多元共晶所组成,其硬度为61~65HRC.保护气体对于激光合金化结果有明显的影响.与氩气和氮气保护比较,氦气保护能产生最好的表面光洁度、最细化的微观组织(二次臂间距SAD,Ar:N2:He=1:1:0.6)、最高的冷却速率(Ar:N2:He=1:1.1:4)、最高的表面硬度(HV0.2,Ar:N2:He=1:1.14:1.15)、最多的合金元素溶解率(Ar:N2:He=1:1.1:1.5).这些结果可以用3种气体的物理特性之间差别来很好解释.

  8. Considerations about Large Area___Low Cost Fast Imaging Photo-detectors

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, John; /Argonne; Attenkofer, Klaus; /Argonne; Delagnes, Eric; /DAPNIA, Saclay; Frisch, Henry; /Chicago U., EFI; Genat, Jean-Francois; /Paris U., VI-VII; Grabas, Herve; /Chicago U., EFI; Heintz, Mary K.; /Chicago U., EFI; May, Edward; /Argonne; Meehan, Samuel; /Argonne; Oberla, Eric; /Argonne; Ruckman, Larry L.; /Hawaii U.; Tang, Fukun; /Chicago U., EFI; Varner, Gary; /Hawaii U.; Vavra, Jaroslav; /SLAC; Wetstein, Matthew; /Argonne

    2012-05-07

    The Large Area Picosecond Photodetectors described in this contribution incorporate a photocathode and a borosilicate glass capillary Micro-Channel Plate (MCP) pair functionalised by atomic layer deposition (ALD) of separate resistive and secondary emission materials. Initial testing with matched pairs of small glass capillary test disks has demonstrated gains of the order of 10{sup 5}-10{sup 6}. Compared to other fast imaging devices, these photodetectors are expected to provide timing resolutions in the 10-100 ps range, and two-dimension position in the sub-millimeter range. If daisy chained, large detectors read at both ends with fast digitising integrated electronics providing zero-suppressed calibrated data should be produced at relatively low cost in large quantities.

  9. Cathode Position Response of Large-Area Photomultipliers Under a Magnetic Field

    CERN Document Server

    Koblesky, T; Polly, C; Peng, J C

    2011-01-01

    With the increasingly common use of large area PMTs (photomultiplier tubes) for nuclear and particle physics experiments, information on the position dependent magnetic field effects across the PMT's photocathode is important to effectively analyze and understand data collected from PMTs. Using an automated two-dimensional scanner, we have measured the PMT response to an external magnetic field as a function of the cathode position impinged by a collimated light source. This study shows a clear dependence on the cathode position in both collection efficiency and gain of the PMT in the presence of a magnetic field. In particular, a pronounced valley in the collection efficiency is observed for certain locations of the cathode when the magnetic field is transverse to the PMT axis. The pattern of the position dependence is presented for several different magnitudes and orientations of the magnetic field relative to the PMT.

  10. Photocathode electron linac for AFEL

    Science.gov (United States)

    Wood, R. L.; Young, L. M.; Aikin, D. J.; Clark, W. L.; DePaula, R. F.; Gladwell, C.; Ledford, J. E.; Martinez, F. A.; Stovall, J. E.

    1993-06-01

    A compact, high brightness accelerator was designed and fabricated by Los Alamos National Laboratory for use in the Advanced Free Electron Laser (AFEL) Facility. A brazed copper, 1300-MHz, 20-MeV structure is suspended within a thermally insulating vacuum vessel. Integral cooling passages allow introduction of cooling water for normal operation, or liquid nitrogen for cryogenic operation. Its exceptional beam quality is expected to enhance the performance of the FEL experiments planned for the AFEL Facility.

  11. Advanced Code for Photocathode Design

    Energy Technology Data Exchange (ETDEWEB)

    Ives, Robert Lawrence [Calabazas Creek Research, Inc., San Mateo, CA (United States); Jensen, Kevin [Naval Research Lab. (NRL), Washington, DC (United States); Montgomery, Eric [Univ. of Maryland, College Park, MD (United States); Bui, Thuc [Calabazas Creek Research, Inc., San Mateo, CA (United States)

    2015-12-15

    The Phase I activity demonstrated that PhotoQE could be upgraded and modified to allow input using a graphical user interface. Specific calls to platform-dependent (e.g. IMSL) function calls were removed, and Fortran77 components were rewritten for Fortran95 compliance. The subroutines, specifically the common block structures and shared data parameters, were reworked to allow the GUI to update material parameter data, and the system was targeted for desktop personal computer operation. The new structures overcomes the previous rigid and unmodifiable library structures by implementing new, materials library data sets and repositioning the library values to external files. Material data may originate from published literature or experimental measurements. Further optimization and restructuring would allow custom and specific emission models for beam codes that rely on parameterized photoemission algorithms. These would be based on simplified and parametric representations updated and extended from previous versions (e.g., Modified Fowler-Dubridge, Modified Three-Step, etc.).

  12. Anchorage Areas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — An anchorage area is a place where boats and ships can safely drop anchor. These areas are created in navigable waterways when ships and vessels require them for...

  13. An Empirical Analysis of the Relationship of the Stock Market and CSI-300 Stock Index Futures Market%沪深300股指期货价格发现功能的实证分析

    Institute of Scientific and Technical Information of China (English)

    贾尚晖; 慕静; 牛晓蕙

    2012-01-01

    价格发现功能是股指期货的一项重要的经济功能.以股指期货与现货市场的相互关系作为出发点,以沪深300指数以及沪深300股指期货连续合约日收盘价数据作为研究对象,采用定性分析与实证分析相结合的手段,深入研究股指期货和现货市场间价格发现关系.%Price discovery function is an important economic function of the stock index futures. The paper is based on the relationship of the stock market and CSI-300 stock index futures market, selecting closing price data as a research object to make theoretical analysis and empirical analysis.

  14. 50GeSe2-25In2Se3-25CsI glass doped with Tm3+, Tm3+/Ho3+ and Tm3+/Er3+ for amplifiers working at 1.22 μm

    Institute of Scientific and Technical Information of China (English)

    XIONG Huihua; TANG Gao; LUO Lan; CHEN Wei

    2011-01-01

    Se-based chalcohalide glass of 50GeSe2-25In2Se3-25CsI was prepared.The thermal and optical characterizations revealed that this host was thermally and optically superior for practical applications.Strong emission centered at 1.22 μm was observed in all Tm3+ single-doped,Tm3+/Ho3+ and Tm3+/Er3+ co-doped samples with an excitation of 808 nm wavelength.The emission was attributed to the Tm3+:3H5→3H6 transition.The co-doping of Ho3+ or Er3+ largely broadened the width and slightly strengthened the intensity of the 1.22 μm emission.The possible energy transfer processes and luminescence kinetics were figured.In addition,its potential application as the host material for novel optical amplifiers was discussed.

  15. Effect of hydrogen on passivation quality of SiN{sub x}/Si-rich SiN{sub x} stacked layers deposited by catalytic chemical vapor deposition on c-Si wafers

    Energy Technology Data Exchange (ETDEWEB)

    Thi, Trinh Cham, E-mail: s1240009@jaist.ac.jp; Koyama, Koichi; Ohdaira, Keisuke; Matsumura, Hideki

    2015-01-30

    We investigate the role of hydrogen content and fixed charges of catalytic chemical vapor deposited (Cat-CVD) SiN{sub x}/Si-rich SiN{sub x} stacked layers on the quality of crystalline silicon (c-Si) surface passivation. Calculated density of fixed charges is on the order of 10{sup 12} cm{sup −2}, which is high enough for effective field effect passivation. Hydrogen content in the films is also found to contribute significantly to improvement in passivation quality of the stacked layers. Furthermore, Si-rich SiN{sub x} films deposited with H{sub 2} dilution show better passivation quality of SiN{sub x}/Si-rich SiN{sub x} stacked layers than those prepared without H{sub 2} dilution. Effective minority carrier lifetime (τ{sub eff}) in c-Si passivated by SiN{sub x}/Si-rich SiN{sub x} stacked layers is as high as 5.1 ms when H{sub 2} is added during Si-rich SiN{sub x} deposition, which is much higher than the case of using Si-rich SiN{sub x} films prepared without H{sub 2} dilution showing τ{sub eff} of 3.3 ms. - Highlights: • Passivation mechanism of Si-rich SiN{sub x}/SiN{sub x} stacked layers is investigated. • H atoms play important role in passivation quality of the stacked layer. • Addition of H{sub 2} gas during Si-rich SiN{sub x} film deposition greatly enhances effective minority carrier lifetime (τ{sub eff}). • For a Si-rich SiN{sub x} film with refractive index of 2.92, τ{sub eff} improves from 3.3 to 5.1 ms by H{sub 2} addition.

  16. InP/InGaAs转移电子光阴极吸收层厚度设计与计算%Design and calculation of absorption layer thickness on InP/InGaAs transferred-electron photocathode

    Institute of Scientific and Technical Information of China (English)

    任彬; 石峰; 郭晖; 焦岗成; 胡仓陆; 成伟; 徐晓兵; 王书菲

    2015-01-01

    The electonic structure and optical properties of standard InGaAs material, which formed the absorption layer of transferred-electron InP/InGaAs photocathode, were studied based on the density functional theory, the exchange and correlation potential energy was described by Heyd-Scuseria-Ernzerh (HSE06). First, the energy band structure of zinc blende GaAs was verified with this hybrid density functional, then the standard InGaAs bulk model was established, and dynamically optimized by self-consistent method before complex dielectric function was obtained, then the optical absorption coefficient was derivated from Kramers-Kronig relation. Finally, under the estimation of P-type standard InGaAs unequilibrium minority carriers effusion length were 0.8, 1.0, 1.2, 1.4, 1.6 and 2.0 m separately, combined with quantum efficiency formula of transferred-electron photocathode, the optimized absorption layer thickness of InP/InGaAs photocathode was derivated according to the photon energy between 0.780 260 eV and 0.820 273 eV with spacing 0.002 eV.%采用基于密度泛函理论的第一性原理平面波赝势法计算了InP/InGaAs转移电子光阴极吸收层材料的电学结构和光学性质,交换关联能采用杂化泛函HSE06来描述.首先对闪锌矿结构GaAs材料能带图进行计算验证,接着建立标准InGaAs材料体结构模型,并对模型进行了动力学的自洽优化,在优化后的基础上进行了非自洽的计算,得到标准InGaAs材料的复介电函数,然后根据Kramers-Kronig关系推出标准InGaAs材料光吸收系数.最后,结合转移电子光阴极量子效率模型,在给定P型标准InGaAs材料非平衡少子扩散长度分别是0.8、1.0、1.2、1.4、1.6和2.0 mm的条件下,得到对能量在0.780 260~0.820 273 eV区间内、间距为0.002 eV的不同光子能量优化的InP/InGaAs转移电子光阴极吸收层厚度.

  17. Revitalization Areas

    Data.gov (United States)

    Department of Housing and Urban Development — Revitalization areas are HUD-designated neighborhoods in need of economic and community development and where there is already a strong commitment by the local...

  18. Wooded areas

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the management of wooded areas on Neal Smith National Wildlife Refuge (formerly Walnut Creek National Wildlife Refuge) between 1992 and 2009.

  19. 700 Area

    Data.gov (United States)

    Federal Laboratory Consortium — The 700 Area of the Hanford Site is located in downtown Richland.Called the Federal Office Building, the Richland Operations Site Manager and the Richland Operations...

  20. 负电子亲和势砷化镓光阴极热发射度测量%Thermal Emittance Measurement of Negative Electron Affinity Gallium Arsenide Photocathode

    Institute of Scientific and Technical Information of China (English)

    吴岱; 潘清; 肖德鑫; 李凯; 杨仁俊; 王建新; 张海旸

    2015-01-01

    作为未来高平均功率、高亮度电子源的重要材料之一,负电子亲和势砷化镓(NEA‐GaAs)光阴极发射的电子束亮度一直以来都是国际上的研究热点。热发射度是电子束能够实现的发射度下限,测量热发射度有利于确定注入器能否提供高亮度的电子束。本文理论计算了 NEA‐GaAs光阴极热发射度数值范围,并基于中国工程物理研究院自由电子激光相干强太赫兹源(FEL‐T Hz )装置,在28 fC的极低电荷量下,采用螺线管扫描法初步测量了NEA‐GaAs光阴极的热发射度。结果显示,NEA‐GaAs光阴极的热发射度为(0.603±0.002)μm/m m。%As one of the most important high average power electron source materials , the high brightness negative electron affinity (NEA ) gallium arsenide (GaAs) photo‐cathode becomes a researcher focus nowadays .The thermal emittance is the lower limit of emittance ,and its measurement is of great importance to determine the brightness that an injector can provide .In this paper ,based on the terahertz free electron laser (FEL‐T Hz) facility in China Academy of Engineering Physics ,some efforts were made to calculate and measure the thermal emittance of NEA‐GaAs photocathode . Under ultra‐low charge of 28 fC NEA‐GaAs photocathode ,the thermal emittance is (0.603 ± 0.002)μm/mm by the solenoid scan method .

  1. O índice de sustentabilidade empresarial (ISE e os impactos no endividamento e na percepção de risco The corporate sustainability index (CSI and the impacts on indebtedness and risk perception

    Directory of Open Access Journals (Sweden)

    Evimael Alves Teixeira

    2011-04-01

    Full Text Available Este estudo investigou se a forma de financiamento das empresas é afetada pela participação das firmas no Índice de Sustentabilidade Empresarial (ISE. Como objetivo complementar, foi analisada a relação entre o ISE e o risco. A fundamentação partiu da teoria da sinalização que apresenta possíveis soluções para mitigar problemas de adverse selection causados pela assimetria de informações e usada no caso de haver necessidade de tomada de decisões sobre investimentos em ambientes de incerteza. Foi utilizado um Experimento Natural, a partir de uma amostra de 378 empresas, divididas em dois grupos: um de tratamento e outro de controle, com dados em painel e duplo efeito fixo. Os resultados encontrados indicam, estatisticamente, que empresas que sinalizaram Responsabilidade Social Corporativa (RSC tiveram uma relação negativa com o endividamento e o risco, quando comparadas com aquelas que não sinalizam. Esses resultados ajudam a entender a relevância dos índices de sustentabilidade como um canal de informação crível do comprometimento da empresa com a RSC.This study investigated whether the way firms fund themselves is affected by their participation in the Corporate Sustainability Index (CSI. As a complementary objective, we analyzed the relationship between the CSI and risk, based on signaling theory, which presents possible solutions to mitigate adverse selection problems caused by asymmetric information, used when there is a need to make decisions about investments in uncertain settings. We used a natural experiment based on a sample of 378 firms, divided into a treatment and a control group, with panel data and double fixed effect. The results indicate that the signaling of corporate social responsibility (CSR was negatively related to indebtedness and risk when compared with firms that did not engage in such signaling. These results shed light on the relevance of sustainability indexes as a credible way for firms to

  2. Efficient p-type dye-sensitized solar cells with all-nano-electrodes: NiCo2S4 mesoporous nanosheet counter electrodes directly converted from NiCo2O4 photocathodes

    Science.gov (United States)

    Shi, Zhiwei; Lu, Hao; Liu, Qiong; Cao, Fengren; Guo, Jun; Deng, Kaimo; Li, Liang

    2014-11-01

    We report the successful growth of NiCo2S4 nanosheet films converted from NiCo2O4 nanosheet films on fluorine-doped tin oxide substrates by a low-temperature solution process. Low-cost NiCo2S4 and NiCo2O4 nanosheet films were directly used for replacing conventional Pt and NiO as counter electrodes and photocathodes, respectively, to construct all-nano p-type dye-sensitized solar cells (p-DSSCs) with high performance. Compared to Pt, NiCo2S4 showed higher catalytic activity towards the I-/I3 - redox in electrolyte, resulting in an improved photocurrent density up to 2.989 mA/cm2, which is the highest value in reported p-DSSCs. Present p-DSSCs demonstrated a cell efficiency of 0.248 % that is also comparable with typical NiO-based p-DSSCs.

  3. A novel photoelectrochemical sensor based on photocathode of PbS quantum dots utilizing catalase mimetics of bio-bar-coded platinum nanoparticles/G-quadruplex/hemin for signal amplification.

    Science.gov (United States)

    Wang, Guang-Li; Liu, Kang-Li; Shu, Jun-Xian; Gu, Tian-Tian; Wu, Xiu-Ming; Dong, Yu-Ming; Li, Zai-Jun

    2015-07-15

    Photocathode based on p-type PbS quantum dots (QDs) combing a novel signal amplification strategy utilizing catalase (CAT) mimetics was designed and utilized for sensitive photoelectrochemical (PEC) detection of DNA. The bio-bar-coded Pt nanoparticles (NPs)/G-quadruplex/hemin exhibited high CAT-like activity following the Michaelis-Menten model for decomposing H2O2 to water and oxygen, whose activity even slightly exceeded that of natural CAT. The bio-bar-code as a catalytic label was conjugated onto the surface of PbS QDs modified electrodes through the formed sandwich-type structure due to DNA hybridization. Oxygen in situ generated by the CAT mimetics of the bio-bar-code of Pt NPs/G-quadruplex/hemin acted as an efficient electron acceptor of illuminated PbS QDs, promoting charge separation and enhancing cathodic photocurrent. Under optimal conditions, the developed PEC biosensor for target DNA exhibited a dynamic range of 0.2pmol/L to 1.0nmol/L with a low detection limit of 0.08pmol/L. The high sensitivity of the method was resulted from the sensitive response of PbS QDs to oxygen and the highly efficient CAT-like catalytic activity of the bio-bar-coded Pt NPs/G-quadruplex/hemin.

  4. M-band flat-response design of X-ray transmission photocathode%透射式X射线光阴极的M带平响应设计

    Institute of Scientific and Technical Information of China (English)

    高扬; 曹柱荣; 李晋; 杨志文; 陈韬; 黎宇坤; 刘慎业

    2013-01-01

    The diagnosis of X-ray flux with high temporal and spatial resolutions is important in the researches of hohlraum physics, and spectral response coupling and design of spectrum rebuilding unit are key issues in the design of flat-response streak camera. Based on the study of the spectral response characteristics of streak camera and X-ray transmission photocathode, compound filter is adopted to realize the M-band band-pass flat-response of streak camera. The calculation shows that the flatness of spectral response is better than 2.7% with an acceptable band pass effect.%获取高时空分辨的M带X射线辐射能流信息是黑腔物理研究的重要内容之一,条纹相机平响应存在谱响应耦合、谱改造元件结构设计等问题.通过对条纹相机和透射式X射线光阴极谱响应特性的研究,提出组合滤片调制法以实现条纹相机M带带通平响应.计算表明,在M带能区内谱灵敏度不平整度仅为2.7%,带通效果良好.

  5. Nursing intervention of CSI for patients with brain trauma coma complicated with pulmonary infection%脑状态指数对脑外伤昏迷并发肺部感染患者的监测及护理干预

    Institute of Scientific and Technical Information of China (English)

    程锦珍; 吴惠平; 周仲辉; 朱彩云; 林育青

    2014-01-01

    Objective Discuss detecting meaning of cerebral state index (CSI) for patients with brain trauma coma complicated with pulmonary infection ,so as to make conclusion for related nursing intervention .Method Choose 65 cases of patients with brain trauma coma complicated with pulmonary infection in our hospital during July ,2011 to July .2013 ,and process CSI and clinical pulmonary infection (CPIS) to analyze the relationship of them and summa-rize the preventive nursing measures .Result The lower CPIS score ,the higher CSI score and the relationship between them is negative correlation .Conclusion CSI and CPIS score have a certain value for brain injury prognosis judgment , and implement preventive nursing can effectively reduce the incidence of pulmonary infection ,so as to help to im-prove the prognosis ,reduce mortality .%目的:探讨脑状态指数(CSI)对脑外伤昏迷并发肺部感染患者的监测意义,总结相应的护理干预。方法选择2011年7月~2013年7月在我院住院治疗的脑外伤昏迷并发肺部感染的65例患者为研究对象,分别行CSI评分和临床肺部感染评分(CPIS),分析两者之间相关性,总结预防性护理措施。结果CSI评分越高,CPIS评分越低,CSI与CPIS之间呈负相关。结论 CSI和CPIS评分对脑外伤预后判断有一定价值,实施预防性护理,可有效降低肺部感染的发生,有助于改善预后,降低病死率。

  6. Multi-user MIMO Transceiver Design in LOS Correlated Channels with Imperfect CSI%视距相关信道下考虑非理想CSI的多用户MIMO收发联合设计

    Institute of Scientific and Technical Information of China (English)

    陈磊; 祝锴; 王大鸣; 崔维嘉

    2011-01-01

    在FDD模式多用户MIMO(Multi-input Multi-output)系统下行链路中,由于信道估计、反馈信道等存在误差,使得发送端获取理想信道状态信息(CSI,channel state information)十分困难.针对获得非理想csI的多用户MIMO系统,考虑在基站和各用户的天线分别具有相关性并引入视距分量的信道条件下,提出了一种新的基于块对角化的MMSE准则收发联合设计算法.该算法首先通过块对角化消除用户间的共信道干扰,然后针对存在信道估计误差的用户信道依据MMSE准则分别迭代求解每个用户预编码和解码矩阵.论文设计出一种基于训练序列的信道估计误差算法,并获得等效信道模型,使得收发端获得的信道状态信息更有实际意义.本文假设反馈信道理想,发射端可以完整得到信道估计矩阵.在MMSE准则下,推导获得了Lagrange乘子的解析解,避免了求解非线性方程的复杂过程,显著降低了计算复杂度.和已有算法相比,该算法不仅可以获得良好的误码性能还可以对各用户进行独立优化,处理更加灵活.仿真分析了视距分量、信道相关性以及信道估计误差对算法性能的影响.仿真结果表明,该算法误码性能良好,算法收敛快,并且对信道估计误差带来的影响有较好的抑制作用.%Multi-user MIMO ( multi-input multi-output) system has been studied in number of papers in recent years. In this paper,a novel multi-user transceiver algorithm is proposed for the system. In the multi-user MIMO system under FDD mode for the downlink, because of the channel estimation error and feedback channel errer, it is difficult to obtain the perfect channel state information ( CSI) at transmitter. With the consideration of both the line-of-sight( LOS) component and the correlation at both the transmitter and users , a minimum sum MSE criterion MIMO transceiver design algorithm based on block diagonalization is proposed. It is supposed that

  7. 视距相关信道下考虑非理想CSI的MIMO收发联合设计%MIMO joint transceiver design in Rice correlated channels with imperfect CSI

    Institute of Scientific and Technical Information of China (English)

    祝锴; 胡捍英; 崔维嘉

    2010-01-01

    MIMO系统收发联合设计的性能依赖于信道状态信息(CSI)的质量.在较高通信频段(如6~8GHz)下,信道的视距分量相对于较低频段显著增加,采用传统的CSI模型无法反映实际的信道特点,从而影响联合设计算法的性能.本文在相关莱斯信道下,提出一种考虑高频段环境下非理想CSI的MIMO系统下行链路收发联合设计算法.论文推导出一种基于训练序列的信道估计误差模型代替传统误差模犁,并在此基础上以最小化MSE为目标迭代求解最优预编码/解码矩阵.仿真结果表明,该算法在不同的子流数、视距分量、信道相关性以及信道估计误差环境下,具有较好的误码率性能.

  8. 基于SVM-Sharpe方法的动量策略在沪深300市场中的应用%The Application of CSI 300 Based on SVM-Sharpe Momentum Strategies

    Institute of Scientific and Technical Information of China (English)

    马雪; 陈盛双; 余放

    2016-01-01

    为了提高动量策略的性能,在J/T方法的基础上,提出了新的动量策略并检验我国沪深300市场的有效性,即在C-SVM算法预测股市买点前提下,构造了基于夏普比率方法的动量策略。结果表明,我国股市在短期内存在明显的反转现象,在中长期存在明显的动量现象,这一现象对我国证券市场的发展和沪深300市场投资者具有参考价值。%In order to improve the performance of the momentum strategies and to develop a new criterion of classification based on the Sharpe ratio on the premise of using C-SVM algorithm predict stock market point of purchase.Experiments show that, CSI 300 market has an obvious reverse effect in short term and it exists momentum effect in medium and long term.And it gives some operational suggestions on the development of China ’ s stock market and investors ’ investments in Shanghai and Shenzhen 300 market.

  9. Pilot Production of Large Area Microchannel Plates and Picosecond Photodetectors

    Science.gov (United States)

    Minot, M.; Adams, B.; Abiles, M.; Bond, J.; Craven, C.; Cremer, T.; Foley, M.; Lyashenko, A.; Popecki, M.; Stochaj, M.; Worstell, W.; Elam, J.; Mane, A.; Siegmund, O.; Ertley, C.

    2016-09-01

    Pilot production performance is reported for large area atomic layer deposition (ALD) coated microchannel plates (ALD-GCA-MCPs) and for Large Area Picosecond Photodetectors (LAPPD™) which incorporate them. "Hollowcore" glass capillary array (GCA) substrates are coated with ALD resistive and emissive layers to form the ALDGCA- MCPs, an approach that facilitates independent selection of glass substrates that are mechanically stronger and that have lower levels of radioactive alkali elements compared to conventional MCP lead glass, reducing background noise[1,2,3,4]. ALD-GCA-MCPs have competitive gain ( 104 each or 107 for a chevron pair ), enhanced lifetime and gain stability (7 C cm-2 of charge extraction), reduced background levels (0.028 events cm-2 sec-1) and low gamma-ray detection efficiency. They can be fabricated in large area (20cm X 20 cm) planar and curved formats suitable for use in high radiation environment applications, including astronomy, space instrumentation, and remote night time sensing. The LAPPD™ photodetector incorporates these ALD-GCA-MCPs in an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na2KSb photocathode, amplified with a stacked chevron pair of ALD-GCA-MCPs. Signals are collected on RF strip-line anodes integrated into to the bottom plates which exit the detector via pin-free hermetic seals under the side walls [5]. Tests show that LAPPDTMs have electron gains greater than 107, submillimeter spatial resolution for large (multiphoton) pulses and several mm for single photons, time resolution less than 50 picoseconds for single photons, predicted resolution less than 5 picoseconds for large pulses, high stability versus charge extraction[6], and good uniformity for applications including astrophysics, neutron detection, high energy physics Cherenkov light detection, and quantum-optical photon-correlation experiments.

  10. A Brief Technical History of the Large-Area Picosecond Photodetector (LAPPD) Collaboration

    Energy Technology Data Exchange (ETDEWEB)

    Adams, B.W.; et al.

    2016-03-06

    The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater than $10^7$ and non-uniformity less than $15\\%$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmable Gate Arrays for local control, data-sparcification, and triggering. We discuss the formation, organization, and technical successes and short-comings of the Collaboration. The Collaboration ended in December 2012 with a transition from R\\&D to commercialization.

  11. A Brief Technical History of the Large-Area Picosecond Photodetector (LAPPD) Collaboration

    CERN Document Server

    Adams, Bernhard W; Bogdan, Mircea; Byrum, Karen; Elagin, Andrey; Elam, Jeffrey W; Frisch, Henry J; Genat, Jean-Francois; Grabas, Herve; Gregar, Joseph; Hahn, Elaine; Heintz, Mary; Insepov, Zinetula; Ivanov, Valentin; Jelinsky, Sharon; Jokely, Slade; Lee, Sun Wu; Mane, Anil U; McPhate, Jason; Minot, Michael J; Murat, Pavel; Nishimura, Kurtis; Northrop, Richard; Obaid, Razib; Oberla, Eric; Ramberg, Erik; Ronzhin, Anatoly; Siegmund, Oswald H; Sellberg, Gregory; Sullivan, Neal T; Tremsin, Anton; Varner, Gary; Veryovkin, Igor; Vostrikov, Alexei; Wagner, Robert G; Walters, Dean; Wang, Hsien-Hau; Wetstein, Matthew; Xi, Junqi; Yusov, Zikri; Zinovev, Alexander

    2016-01-01

    The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater than $10^7$ and non-uniformity less than $15\\%$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmab...

  12. Quiet areas

    DEFF Research Database (Denmark)

    Petersen, Rikke Munck

    2016-01-01

    This paper argues that drone filming can substantiate our understanding of multisensorial experiences of quiet areas and urban landscapes. Contrary to the distanced gaze often associated with the drone, this paper discusses drone filming as an intimate performativity apparatus that can affect...... perception as a result of its interrelationships between motion, gaze, and sound. This paper uses four films, one of which is a drone flyover, to launch a discussion concerning a smooth and alluring gaze, a sliding gaze that penetrates landscapes, and site appearance. Films hold the capacity to project both...... and transcendence can facilitate a deeper understanding of intimate sensations, substantiating their role in the future design and planning of urban landscapes. Hence, it addresses the ethics of an intimacy perspective (of drone filming) in the qualification of quiet areas....

  13. Artificial intelligence systems for rainy areas detection and convective cells' delineation for the south shore of Mediterranean Sea during day and nighttime using MSG satellite images

    Science.gov (United States)

    Tebbi, Mohsene Abdelfettah; Haddad, Boualem

    2016-09-01

    The aim of this study is to investigate the potential of cloud classification by means of support vector machines using high resolution images from northern Algeria. The images were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board of the Meteosat Second Generation (MSG) satellite. An automatic system was developed to operate during both day and nighttime by following two steps of data processing. The first aims to detect rainy areas in cloud systems, whereas the second delineates convective cells from stratiform ones. A set of 12 spectral parameters was selected to extract information about cloud properties, which are different from day to night. The training and validation steps of this study were performed by in-situ rainfall measurement data, collected during the rainy season of years 2011 and 2012 via automatic rain gauge stations distributed in northern Algeria. Artificial neural networks (ANNs) and support vector machine (SVM) were explored, by combining spectral parameters derived from MSG images. Better performances were obtained by the SVM classifier, in terms of Critical Success Index and Probability of Detection for rainy areas detection (CSI = 0.81, POD = 91%), and also for convective/stratiform delineation (CSI = 0.55, POD = 74%).

  14. 沪深300股指期货动态价量关系研究%Study on the Dynamic Relationship between Price and Volume of CSI 300 Stock Index Futures

    Institute of Scientific and Technical Information of China (English)

    曾廷敏; 林祥友; 王勇

    2013-01-01

    The dynamic relationships between price and volume of CSI 300 stock index futures are empirically examined based on 5 minutes high frequency transaction price and volume data of CSI 300 stock index futures contracts , and the results show that there is obviously positive direction relationship between price volatility and trading volume and between relative trading volume and relative position volume , but there is significantly negative direction relation with position volume , that there is obviously positive relationship between the volatility and expected trading volume or unexpected trading volume , furthermore , the positive influence of unexpected trading volume is bigger , that there is significantly negative relationship between the volatility and expected position volume or unexpected position volume , furthermore , the negative influence of unexpected position volume is bigger , that the influence of the change of trading volume and position volume on the volatility of stock index futures price is asymmetric , and that the influence of the shock of positive trading volume and position volume is bigger than that of negative trading volume and position volume , i.e.the influence on price volatility is bigger when unexpected trading volume and unexpected position volume are positive .The supervisors and investors in stock index futures market can analyze the changing trends of the implicit indicators such as price volatility and market risk and so on by monitoring explicit indicators such as trading volume , position volume , relatively trading volume , relative position volume and so on as well as their changes in order to implement proper supervising policies and trading policies .%利用沪深300股指期货合约的5分钟高频交易价量数据,分析股指期货合约的价量特征及其动态关系,结果表明:股指期货合约的价格波动率与成交量、相对成交量和相对持仓量之间均存在显著正向关系,而与持仓

  15. Precoding and feedback for massive MIMO via beamformed CSIRS%基于CSI-RS赋形的大规模天线阵列预编码与反馈方法

    Institute of Scientific and Technical Information of China (English)

    陈文洪; 高秋彬; 陈润华; 李辉; Tamrakar RAKESH; 孙韶辉

    2016-01-01

    大规模天线阵列的应用是5G技术中提高频谱效率的有效手段.在大规模天线阵列系统中,天线单元的数量显著增长.这些天线单元可以与不同数量的无线射频通道连接,从而映射到多个天线端口上.由于大量的天线单元可以组成不同形状的天线阵列,设计单一的反馈框架来支持不同形态的大规模天线阵列具有很大的挑战性.本文分析了在大规模天线阵列系统中实现多个维度预编码的方法,通过在水平维和垂直维分别进行预编码,充分利用了所有天线单元的天线增益和赋形增益,且所给方法只需要借助目前广泛应用于2D天线阵列的反馈机制.从我们的仿真中可以看出:基于CSI-RS赋形的CSI反馈和相应的预编码算法,相对于传统MIMO处理方式,能够获得显著的性能增益.而且,这种方法只需要一些基站侧的实现,对终端可以是完全透明的,因此对终端的影响很小.

  16. Nanowire mesh solar fuels generator

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  17. CSI Measurement Evaluation Database Function and Scientific Evaluation-Based on Northwest A & F University Domestic Paper Science Index Analysis%CSI计量评价数据库的功能与科学评价--以西北农林科技大学国内论文科学指标分析为例

    Institute of Scientific and Technical Information of China (English)

    梁花侠; 赵海星

    2013-01-01

    在介绍CSI数据库功能的基础上,利用CSI对西北农林科技大学近10年来的国内学术论文在全部学科中的发文量、文献被引量、研究成果主要学科分布、顶尖论文、高被引论文及高影响力的研究成员等各项科学指标进行了定量分析。提出重视利用CSI的评价分析功能不仅对政策制定者、科研管理人员、科研工作者、出版社或编辑部均有一定的帮助和参考价值,而且对高校图书馆在搞好文献信息资源建设与服务方面也具有重要的现实意义。%The paper introduces the function of the CSI.Based on the usage of CSI in the domestic academic papers in all the subjects of Northwest A&F University,the paper evaluates the indicators for the quantitative analysis,such as literature cited amount,the research subject distribution and top of the science paper.Besides,the analysis and evaluation of the CSI are important not only to policy makers,scientific research management personnel,scientific research workers,press or the editorial department,but also to university libraries in the literature information resource construction and improved services also have important practical significance.

  18. Measurement of CSI 300 stock index futures volatility under high-frequency environment-Methods based on realized volatility and its modification%高频环境下沪深300股指期货波动测度——基于已实现波动及其改进方法

    Institute of Scientific and Technical Information of China (English)

    龙瑞; 谢赤; 曾志坚; 罗长青

    2011-01-01

    作为中国唯一上市交易的金融期货产品,沪深300股指期货在资本市场价格发现和风险防范过程中扮演重要角色,科学准确地测度其收益波动对充分实现股指期货避险功能具有重要理论和现实价值,在日内高频信息环境下分别采用经典已实现波动率、已实现极差波动率和已实现双幂波动率等三类方法对沪深300股指期货的收益波动进行测度,通过样本内预测误差指标对上述方法的测度性能进行比较,实证结果表明:沪深300股指期货在上市交易后表现出由剧烈波动到渐趋平稳的波动特征,已实现波动的改进方法在沪深300股指期货收益波动的测度性能上具有较为明显的优越性.%As the only publicly launched financial futures contracts of China, CSI 300 stock index futures plays an important role in the process of price discovery and risk prevention of the capital market. The measurement of its return volatility is significantly important to achieve the risk aversion function of stock index futures. Under the intraday high-frequency data environment, the return volatility of Chinese CSI 300 stock index futures was measured by realized volatility methods including clasaical realized volatility,realized range-based volatility and realized bipower volatility. The in-sample prediction error indicators were introduced to di8tinguish the performance of the methods above. The empirical results indicate that the return volatility of CSI 300 stock index futures fluctuated fiercely at the beginning after listing while then changed to be stable, and modified methods of realized volatility show a better measurement performance of retIlrn volatility of CSI 300 stock index futures than classical realized volatility.

  19. 基于日内效应的沪深300股指期货套利的分析%Study on CSI300 index futures’arbitrage based on intraday effect

    Institute of Scientific and Technical Information of China (English)

    赵秀娟; 魏卓; 汪寿阳

    2015-01-01

    基于1 min的高频数据首次对沪深300股指期货日内特征进行分析,发现其日内绝对收益率的“LM”型特征,日内成交量的“WV”型特征,持仓量的“倒U”型特征,价差的“LM”型特征,以及错误定价率的“早上高、下午低”的日内均值回复特征,并通过向量自回归模型的方差分解和脉冲响应函数分析了五个指标的动态关联性。随后,根据沪深300股指期货错误定价率出现的“上午高、下午低”的日内特征,设计了相应的套利策略。样本内和样本外的套利收益数据表明,基于沪深300股指期货日内特征的套利策略是有效的。全文最后根据实证结果提出了相应的投资建议。%Based on 1 minute high-frequency data,this paper analyzed intraday effect of CSI300 index futures for the first time and found“LM”pattern of absolute yields,“WV”pattern of volume,“inverted U”pattern of position,“LM”pattern of basis between highest and lowest price within 1 minute,and“high in the morning, low in the afternoon”pattern of mispricing ratio. Then,dynamic correlation of these five indicators was ana-lyzed by vector auto regression model of variance decomposition and impulse response function. In addition, we designed arbitrage strategy based on mispricing ratio’s intraday effect,and intrasample and outsample re-sult shows the intraday arbitrage strategy is effective. Finally,we made investment recommendations based on result.

  20. Mini-mast CSI testbed user's guide

    Science.gov (United States)

    Tanner, Sharon E.; Pappa, Richard S.; Sulla, Jeffrey L.; Elliott, Kenny B.; Miserentino, Robert; Bailey, James P.; Cooper, Paul A.; Williams, Boyd L., Jr.; Bruner, Anne M.

    1992-01-01

    The Mini-Mast testbed is a 20 m generic truss highly representative of future deployable trusses for space applications. It is fully instrumented for system identification and active vibrations control experiments and is used as a ground testbed at NASA-Langley. The facility has actuators and feedback sensors linked via fiber optic cables to the Advanced Real Time Simulation (ARTS) system, where user defined control laws are incorporated into generic controls software. The object of the facility is to conduct comprehensive active vibration control experiments on a dynamically realistic large space structure. A primary goal is to understand the practical effects of simplifying theoretical assumptions. This User's Guide describes the hardware and its primary components, the dynamic characteristics of the test article, the control law implementation process, and the necessary safeguards employed to protect the test article. Suggestions for a strawman controls experiment are also included.

  1. FleCSI: Connection to Legion

    Energy Technology Data Exchange (ETDEWEB)

    Bergen, Benjamin Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-03

    These are slides which are part of the ASC L2 Milestone Review. The following topics are covered: Legion Backend, Distributed-Memory Partitioning, Sparse Data Representations, and MPI-Legion Interoperability.

  2. Development of large area, pico-second resolution photo-detectors and associated readout electronics

    Energy Technology Data Exchange (ETDEWEB)

    Grabas, H.; Oberla, E. [Enrico Fermi Inst., Univ. of Chicago, Chicago, IL 60637 (United States); Attenkoffer, K. [Argonne National Laboratory, Argonne, IL 60439 (United States); Bogdan, M.; Frisch, H. J. [Enrico Fermi Inst., Univ. of Chicago, Chicago, IL 60637 (United States); Genat, J. F. [LPNHE, CNRS/IN2P3/LPNHE, Paris 75252 (France); Northrop, R. [Enrico Fermi Inst., Univ. of Chicago, Chicago, IL 60637 (United States); May, E. N. [Argonne National Laboratory, Argonne, IL 60439 (United States); Varner, G. S. [Univ. of Hawaii, Honolulu, HI 96822 (United States); Wetstein, M. [Argonne National Laboratory, Argonne, IL 60439 (United States)

    2011-07-01

    The Large Area Pico-second Photo-detectors described in this contribution incorporate a photo-cathode and a borosilicate glass capillary Micro-Channel Plate (MCP) pair functionalized by atomic layer deposition (ALD) of separate resistive and electron secondary emitters materials. They may be used for biomedical imaging purposes, a remarkable opportunity to apply technologies developed in HEP having the potential to make major advances in the medical world, in particular for Positron Emission Tomography (PET). If daisy-chained and coupled to fast transmission lines read at both ends, they could be implemented in very large dimensions. Initial testing with matched pairs of small glass capillary test has demonstrated gains of the order of 105 to 106. Compared to other fast imaging devices, these photo-detectors are expected to provide timing resolutions in the 10-100 ps range, and two-dimension position in the sub-millimeter range. A 6-channel readout ASIC has been designed in 130 nm CMOS technology and tested. As a result, fast analog sampling up to 17 GS/s has been obtained, the intrinsic analog bandwidth being presently under evaluation. The digitization in parallel of several cells in two microseconds allows getting off-chip digital data read at a maximum rate of 40 MHz. Digital Signal Processing of the sampled waveforms is expected achieving the timing and space resolutions obtained with digital oscilloscopes. (authors)

  3. FHFA Underserved Areas

    Data.gov (United States)

    Department of Housing and Urban Development — Federal Housing Finance Agency's (FHFA) Underserved Areas establishes underserved area designations for census tracts in Metropolitan Areas (MSAs), nonmetropolitan...

  4. Class 1 Areas

    Data.gov (United States)

    U.S. Environmental Protection Agency — A "Class 1" area is a geographic area recognized by the EPA as being of the highest environmental quality and requiring maximum protection. Class I areas are areas...

  5. Recent Polarized Photocathode Rand D at SLAC

    CERN Document Server

    Luh, D A

    2002-01-01

    The SLAC high-gradient-doped MOCVD-grown GaAs cathode presently in use consists of a strained GaAs low-doped layer (with a small admixture of P) capped by a few nanometers of highly Zn-doped GaAs, which is heat-cleaned at relatively high temperature and then activated by Cs/NF sub 3 co-deposition. The high-gradient-doped structure solves the problem of the surface charge limit that the previously-used SLAC cathodes had, and this preparation procedure has produced satisfactory results. However, the preparation procedure has a few weaknesses that prevent cathodes from achieving the ultimate desired performance. The peak polarization is limited to 80% due to strain relaxation in the relatively thick strained layers. Also dopant loss causes the surface charge limit effect to reappear after multiple high-temperature heat-cleanings. In this paper, we will discuss recent progress made at SLAC that addresses these limitations, including using the MBE growth technique with Be doping and using the superlattice structur...

  6. Optimization of the electron collection efficiency of a large area MCP-PMT for the JUNO experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lin, E-mail: chenlin@opt.cn [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Xi’an Jiaotong University, Xi’an 710049 (China); Tian, Jinshou [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Liu, Chunliang [Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Yifang; Zhao, Tianchi [Institute of High Energy Physics (IHEP) of CAS, Beijing 100049 (China); Liu, Hulin; Wei, Yonglin; Sai, Xiaofeng [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Chen, Ping [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Wang, Xing; Lu, Yu [Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Hui, Dandan; Guo, Lehui [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119 (China); Graduate School of Chinese Academy of Sciences (CAS), Beijing 100049 (China); Liu, Shulin; Qian, Sen; Xia, Jingkai; Yan, Baojun; Zhu, Na [Institute of High Energy Physics (IHEP) of CAS, Beijing 100049 (China); Sun, Jianning; Si, Shuguang [North Night Vision Technology (NNVT) CO., LTD, Nanjing 210110 (China); and others

    2016-08-11

    A novel large-area (20-inch) photomultiplier tube based on microchannel plate (MCP-PMTs) is proposed for the Jiangmen Underground Neutrino Observatory (JUNO) experiment. Its photoelectron collection efficiency C{sub e} is limited by the MCP open area fraction (A{sub open}). This efficiency is studied as a function of the angular (θ), energy (E) distributions of electrons in the input charge cloud and the potential difference (U) between the PMT photocathode and the MCP input surface, considering secondary electron emission from the MCP input electrode. In CST Studio Suite, Finite Integral Technique and Monte Carlo method are combined to investigate the dependence of C{sub e} on θ, E and U. Results predict that C{sub e} can exceed A{sub open}, and are applied to optimize the structure and operational parameters of the 20-inch MCP-PMT prototype. C{sub e} of the optimized MCP-PMT is expected to reach 81.2%. Finally, the reduction of the penetration depth of the MCP input electrode layer and the deposition of a high secondary electron yield material on the MCP are proposed to further optimize C{sub e}.

  7. Margin on the Shanghai and Shenzhen 300 Index-Based on the CSI 300 Index 2015 Transactions%融资融券对沪深300指数的影响-基于2015年沪深300指数交易数据

    Institute of Scientific and Technical Information of China (English)

    罗晓霜

    2016-01-01

    The "Stock market crash"in 2015 has caused heavy losses for many investors, and the role of business in which the margin"cliff-style"crash can not be ignored.The paper used two measurement methods called co-integration test and Granger to study the relationship between them based on historical transactions in Shanghai and Shenzhen 300 Index and margin balances from January 5th, 2015 to the end of 2015.The results showed that:there's a long-term co-integration relationship between margin balance and CSI 300 index, the CSI 300 is the Granger cause of the margin balance, the financing balance is not the Granger cause of CSI 300 index. Put forward policy recommendations based on the above conclusions combined with market characteristics.%2015年的“股灾”让众多投资者遭受重创,而其中的融资融券业务在这次“断崖式”暴跌中的作用不可忽视。本文基于2015年1月5日至2015年底的沪深300指数以及融资融券余额的历史交易数据,利用协整检验和格兰杰因果检验的计量方法研究两者之间的关系。结果表明:融资融券余额与沪深300指数之间存在着长期的协整关系,沪深300是两融余额的格兰杰原因,融资余额不是沪深300指数的格兰杰原因。基于以上结论并结合市场特点,提出相关政策建议。

  8. Gamma ray Large Area Space Telescope (GLAST) Balloon Flight Engineering Model Overview

    CERN Document Server

    Thompson, D J; Williams, S; Grove, J E; Mizuno, T; Sadrozinski, H F W

    2002-01-01

    The Gamma Ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) is a pair-production high-energy (>20 MeV) gamma-ray telescope being built by an international partnership of astrophysicists and particle physicists for a satellite launch in 2006, designed to study a wide variety of high-energy astrophysical phenomena. As part of the development effort, the collaboration has built a Balloon Flight Engineering Model (BFEM) for flight on a high-altitude scientific balloon. The BFEM is approximately the size of one of the 16 GLAST-LAT towers and contains all the components of the full instrument: plastic scintillator anticoincidence system (ACD), high-Z foil/Si strip pair-conversion tracker (TKR), CsI hodoscopic calorimeter (CAL), triggering and data acquisition electronics (DAQ), commanding system, power distribution, telemetry, real-time data display, and ground data processing system. The principal goal of the balloon flight was to demonstrate the performance of this instrument configuration under c...

  9. Pilot production and advanced development of large-area picosecond photodetectors

    Science.gov (United States)

    Minot, Michael J.; Adams, Bernhard W.; Aviles, Melvin; Bond, Justin L.; Craven, Christopher A.; Cremer, Till; Foley, Michael R.; Lyashenko, Alexey; Popecki, Mark A.; Stochaj, Michael E.; Worstell, William A.; Mane, Anil U.; Elam, Jeffrey W.; Siegmund, Oswald H. W.; Ertley, Camden; Frisch, Henry; Elagin, Andrey

    2016-09-01

    We report pilot production and advanced development performance results achieved for Large Area Picosecond Photodetectors (LAPPD). The LAPPD is a microchannel plate (MCP) based photodetector, capable of imaging with single-photon sensitivity at high spatial and temporal resolutions in a hermetic package with an active area of 400 square centimeters. In December 2015, Incom Inc. completed installation of equipment and facilities for demonstration of early stage pilot production of LAPPD. Initial fabrication trials commenced in January 2016. The "baseline" LAPPD employs an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na2KSb photocathode and amplified with a stacked chevron pair of "next generation" MCPs produced by applying resistive and emissive atomic layer deposition coatings to borosilicate glass capillary array (GCA) substrates. Signals are collected on RF strip-line anodes applied to the bottom plates which exit the detector via pinfree hermetic seals under the side walls. Prior tests show that LAPPDs have electron gains greater than 107, submillimeter space resolution for large pulses and several mm for single photons, time resolutions of 50 picoseconds for single photons, predicted resolution of less than 5 picoseconds for large pulses, high stability versus charge extraction, and good uniformity. LAPPD performance results for product produced during the first half of 2016 will be reviewed. Recent advances in the development of LAPPD will also be reviewed, as the baseline design is adapted to meet the requirements for a wide range of emerging application. These include a novel ceramic package design, ALD coated MCPs optimized to have a low temperature coefficient of resistance (TCR) and further advances to adapt the LAPPD for cryogenic applications using Liquid Argon (LAr). These developments will meet the needs for DOE-supported RD for the Deep Underground Neutrino

  10. Areas of Triangles

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>We know that the area of any right triangle is half the area of the rectangle which has the same height and the same base with the triangle.The area of rectangle DFEG below is bh.So the area of triangle DFG is 1/2bh. Now we can give a proof of the conclusion that every triangle has half the area of a related rectangle.

  11. Wavelength-shifting fiber readout of LaCl3 and LaBr3 scintillators

    Science.gov (United States)

    Case, Gary L.; Cherry, Michael L.; Stacy, J. Gregory; Welch, Christopher E.

    2005-08-01

    Inorganic scintillators such as NaI(Tl) and CsI(Na) have been used extensively in hard x-ray and low-energy gamma-ray imaging systems. Recently, a new generation of scintillators has been developed with properties that could greatly enhance the performance of such imaging systems. In particular, the lanthanum halides show great promise with increased light yield and peak emission at shorter wavelengths compared to NaI or CsI. Since these scintillators emit at relatively short wavelengths, wavelength-shifting fibers can be used which re-emit at wavelengths around 420 nm, providing a good match to bialkali photocathode response. Multi-anode photomultiplier tubes can be used to read out individual fibers from orthogonal layers to provide x-y position information, while energy measurements can be made by large area photomultiplier tubes. Such an arrangement potentially provides improved overall position and energy resolution and lower thresholds compared to imaging systems configured as standard NaI or CsI gamma cameras. We present measurements of the energy resolution obtained from lanthanum chloride (LaCl3) and lanthanum bromide (LaBr3) scintillators viewed both perpendicular to the axis and down the length of square multi-clad wavelength-shifting fibers. These results are compared to a standard NaI detector with wavelength-shifting fibers. The implications of these results for gamma-ray imaging will then be discussed.

  12. HILT - A heavy ion large area proportional counter telescope for solar and anomalous cosmic rays

    Science.gov (United States)

    Klecker, Berndt; Hovestadt, Dietrich; Scholer, M.; Arbinger, H.; Ertl, M.; Kaestle, H.; Kuenneth, E.; Laeverenz, P.; Seidenschwang, E.; Blake, J. B.

    1993-01-01

    The HILT sensor has been designed to measure heavy ion elemental abundances, energy spectra, and direction of incidence in the mass range from He to Fe and in the energy range 4 to 250 MeV/nucleon. With its large geometric factor of 60 sq cm sr the sensor is optimized to provide compositional and spectral measurements for low intensity cosmic rays (i.e. for small solar energetic particle events and for the anomalous component of cosmic rays). The instrument combines a large area ion drift chamber-proportional counter system with two arrays of 16 Li-drift solid state detectors and 16 CsI crystals. The multi dE/dx-E technique provides a low background mass and energy determination. The sensor also measures particle direction. Combining these measurements with the information on the spacecraft position and attitude in the low-altitude polar orbit, it will be possible to infer the ionic charge of the ions from the local cutoff of the Earth's magnetic field. The ionic charge in this energy range is of particular interest because it provides unique clues to the origin of these particles and has not been investigated systematically so far. Together with the other instruments on board SAMPEX (LEICA, MAST, and PET), a comprehensive measurement of the entire solar and anomalous particle population will be achieved.

  13. LeaseAreas

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — Federal outer Continental Shelf (OCS) Sand and Gravel Borrow Areas (Lease Areas) are polygons which are maintained by the Bureau of Ocean Energy Management (BOEM),...

  14. BOEM Wind Planning Areas

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set represents the most recent changes for the Wind Development Planning Areas in the Atlantic. Wind Planning Areas in this dataset represent up to six...

  15. Sunk Lake Natural Area

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Sunk Lake Natural Area Management Plan guides the long-range development of the Natural Area by identifying and integrating appropriate habitats, management...

  16. Infrastructure Area Simplification Plan

    CERN Document Server

    Field, L.

    2011-01-01

    The infrastructure area simplification plan was presented at the 3rd EMI All Hands Meeting in Padova. This plan only affects the information and accounting systems as the other areas are new in EMI and hence do not require simplification.

  17. Vermont Designated Natural Areas

    Data.gov (United States)

    Vermont Center for Geographic Information — Under Natural Areas Law (10 Vermont Statutes Annotated, Chapter 83 § 2607) the FPR commissioner, with the approval of the governor, may designate and set aside areas...

  18. Selected areas in cryptography

    CERN Document Server

    Oorschot, Paul

    1997-01-01

    Selected Areas in Cryptography brings together in one place important contributions and up-to-date research results in this fast moving area. Selected Areas in Cryptography serves as an excellent reference, providing insight into some of the most challenging research issues in the field.

  19. The Ethiopean Language Area.

    Science.gov (United States)

    Ferguson, Charles A.

    This paper constitutes the fifth chapter of the forthcoming volume "Language in Ethiopia." In an effort to better define the particular linguistic area, the author analyzes phonological and grammatical features that languages in the area have in common. A number of features have been identified as characteristic of the area, and this…

  20. 股指期货套期保值效率比较研究--基于沪深300股指期货与新华富时A5指数期货%The Comparative Study of Stock Index Future Hedging Efficiency---Based on CSI 300 Stock Index Futures and FTES Xinhua A50 Index Futures

    Institute of Scientific and Technical Information of China (English)

    范泰奇; 韩复龄

    2014-01-01

    文章基于我国股票型基金十大重仓股构建投资组合,并利用沪深300股指期货与新华富时A50指数期货的日数据对这两种股指期货的套期保值效率进行比较研究,以探究两者在套期保值效率上的差异和造成差异产生的原因。在利用OLS、VECM和ECM-BGRACH等静态和动态套期保值模型和基于风险最小化的套期保值绩效指标对沪深300股指期货与新华富时A50指数期货的套期保值效率进行研究后发现,在静态最优套保比、时变最优套保比和套期保值绩效指标的比较中,新华富时A50指数期货都要优于沪深300股指期货。这种套期保值效率上的差异主要来自于两个金融工具间的合约与交易规则的差别。建议通过设立适当时间的晚间电子盘交易,并允许金融机构在规定的份额内进行期指套利交易,以提升沪深300股指期货在套期保值市场功能上的效率。%Through constructing portfolio with the ten great overweight held stocks by funds, the paper makes comparative research for the CSI 300 stock index futures and the FTES Xinhua A50 index futures by using daily data of them to find the hedging efficiency difference between them and the reasons that cause the difference. Based on OLS, VECM and ECM-GRACH static and dynamic hedging model and the minimum risk hedging performance indicators, the author finds that the FTES Xinhua A50 index futures are better than the CSI 300 index futures in the static optimal hedge ratio, time-varying optimal hedge ratio and hedging performance indicators. According to the results, it can be found that the difference results from the different contract and trading rules between the two financial instruments The author suggests that building up the evening electronic trading market in appropriate time and allow financial institutions to arbitrage by using stipulated quota for enhancing hedging efficiency of market function of CSI 300 stock

  1. Evidence of the Price Discovery and Volatility Spillover of the CSI 300 Stock Index Futures Based on the BEEK-GARCH Model%沪深300股指期货的价格发现能力及波动溢出效应研究--基于BEEK-GARCH 模型的证据

    Institute of Scientific and Technical Information of China (English)

    陶启智; 李亮; 郭姝辛

    2015-01-01

    以沪深300股指期货自推出至今的1分钟数据作为研究样本,使用BEEK‐GARCH模型量化沪深300股指期货和现货市场的价格发现能力及波动溢出效应。研究发现,我国期货市场成立初期并未发挥其价格发现功能,这一现象随着市场成熟度增加而逐渐改善,期货市场在价格发现过程中占主要地位。通过GARCH 模型对收益率调整过程进行估计,发现市场之间存在双向波动溢出效应:短期内表现出均值回归;长期来看,误差修正项系数显著异于0,符合调整的负反馈性质,价格偏差会被纠正从而达到长期均衡。%With the 1 minute interval data up to the present time of the CSI 300 stock index futures as the samples ,this paper quantitatively studies the price discovery and volatility spillover of the CSI 300 stock index futures and spot markets ,using the BEEK‐GARCH model .The impulse response function and vari‐ance decomposition are used to imply the price discovery ,w hich show s that the future market plays a more important role .A vector error correction model is built to describe the dynamic adjustment of the futures and spot price of stock indexes .The result shows that there exists a two‐way granger causal relationship between the futures and the spots ,as well as a volatility spillover effect .The regression will return to the mean in the short run and satisfies the negative feedback of the correction that the existence of arbitrage will adjust the bias to the equilibrium in the long run .

  2. Fishing Access Areas

    Data.gov (United States)

    Vermont Center for Geographic Information — The Vermont Fish & Wildlife Department maintains developed fishing access areas. These sites provide public access to waters in Vermont for shore fishing...

  3. CVP Service Area

    Data.gov (United States)

    California Department of Resources — Federal Water Contract Service Area boundaries are incorporated boundaries of districts having contracts with the U.S. Bureau of Reclamation (Reclamation), within...

  4. Aperture area measurement facility

    Data.gov (United States)

    Federal Laboratory Consortium — NIST has established an absolute aperture area measurement facility for circular and near-circular apertures use in radiometric instruments. The facility consists of...

  5. Northwest Area Science

    Science.gov (United States)

    Fuentes, Tracy L.; van Heeswijk, Marijke; Grossman, Eric E.

    2010-01-01

    Northwest Area Facts * Population about 12 million * 43 federally recognized Tribes * Hydropower provides about two-thirds of electricity supply * 78 federally listed threatened and endangered species * 12 active or potentially active volcanoes * Columbia River system drains more than 260,000 square miles, an area about the size of Texas * More than 175 square miles covered by glaciers * More than 900 miles of Pacific Ocean coastline * More than 2,300 miles of greater Puget Sound coastline * Some forests store more carbon per unit area than any other area in the world, including the tropics * 51 percent federal lands * Significant lead, zinc, silver, and phosphate deposits

  6. Available area isotherm

    NARCIS (Netherlands)

    Bosma, JC; Wesselingh, JA

    2004-01-01

    A new isotherm is presented for adsorption of proteins, the available area isotherm. This isotherm has a steric basis, unlike the (steric) mass action model. The shape of the available area isotherm is determined only by geometric exclusion. With the new isotherm, experimental results can be fitted

  7. PYRAMID ROADLESS AREA, CALIFORNIA.

    Science.gov (United States)

    Armstrong, Augustus K.; Scott, Douglas F.

    1984-01-01

    A geologic and mineral survey was conducted in the Pyramid Roadless Area, California. The area contains mineral showings, but no mineral-resource potential was identified during our studies. Three granodiorite samples on the west side of the roadless area contained weakly anomalous concentrations of uranium. Two samples of roof-pendant rocks, one metasedimentary rock and one metavolcanic rock, contain low concentrations of copper, and of copper and molybdenum, respectively. Although none was identified, the geologic terrane is permissive for mineral occurrences and large-scale, detailed geologic mapping of the areas of metasedimentary and metavolcanic roof pendants in the Pyramid Roadless Area could define a mineral-resource potential for tungsten and precious metals.

  8. Protected areas and poverty

    Science.gov (United States)

    Brockington, Daniel; Wilkie, David

    2015-01-01

    Protected areas are controversial because they are so important for conservation and because they distribute fortune and misfortune unevenly. The nature of that distribution, as well as the terrain of protected areas themselves, have been vigorously contested. In particular, the relationship between protected areas and poverty is a long-running debate in academic and policy circles. We review the origins of this debate and chart its key moments. We then outline the continuing flashpoints and ways in which further evaluation studies could improve the evidence base for policy-making and conservation practice. PMID:26460124

  9. Development of a Large Area Advanced Fast RICH Detector for Particle Identification at the Large Hadron Collider Operated with Heavy Ions

    CERN Multimedia

    Piuz, F; Braem, A; Van beelen, J B; Lion, G; Gandi, A

    2002-01-01

    %RD26 %title\\\\ \\\\During the past two years, RD26 groups have focused their activities on the production of CsI-RICH prototypes of large area, up to a square meter, to demonstrate their application in High Energy experiments. Many large CsI-photocathodes (up to 40) were produced following the processing techniques furthermore developped in the collaboration. Taking the Quantum Efficiency (QE) measured at 180 nm as a comparative figure of merit of a CsI-PC. Figure 1 shows the increase of the performance while improvements were successively implemented in the PC processing sequence. Most efficient were the use of substrates made of nickel, the heat treatment and handling of the PCs under inert gas. Actually, three large systems based on CsI-RICH have got approval in the following HEP experiments: HADES at GSI, COMPASS/NA58 at CERN and HMPID/ALICE at LHC implying up to 14 square metres of CsI-PC. In addition, several CsI-RICH detectors have been successfully operated in the Threshold Imaging Detector at NA44 and ...

  10. Ice Engineering Research Area

    Data.gov (United States)

    Federal Laboratory Consortium — Refrigerated Physical Modeling of Waterways in a Controlled EnvironmentThe Research Area in the Ice Engineering Facility at the Cold Regions Research and Engineering...

  11. Pilot Boarding Areas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Pilot boarding areas are locations at sea where pilots familiar with local waters board incoming vessels to navigate their passage to a destination port. Pilotage is...

  12. Decontamination & decommissioning focus area

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    In January 1994, the US Department of Energy Office of Environmental Management (DOE EM) formally introduced its new approach to managing DOE`s environmental research and technology development activities. The goal of the new approach is to conduct research and development in critical areas of interest to DOE, utilizing the best talent in the Department and in the national science community. To facilitate this solutions-oriented approach, the Office of Science and Technology (EM-50, formerly the Office of Technology Development) formed five Focus AReas to stimulate the required basic research, development, and demonstration efforts to seek new, innovative cleanup methods. In February 1995, EM-50 selected the DOE Morgantown Energy Technology Center (METC) to lead implementation of one of these Focus Areas: the Decontamination and Decommissioning (D & D) Focus Area.

  13. SO2 Nonattainment Areas

    Data.gov (United States)

    U.S. Environmental Protection Agency — This data layer identifies areas in the U.S. where air pollution levels have not met the National Ambient Air Quality Standards (NAAQS) for Sulfur dioxide and have...

  14. PM 10 Nonattainment Areas

    Data.gov (United States)

    U.S. Environmental Protection Agency — This data layer identifies areas in the U.S. where air pollution levels have not met the National Ambient Air Quality Standards (NAAQS) for PM 10 and have been...

  15. Driftless Area NWR ROCSTAR

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Resources of Concern Selection Tool for Americas Refuges (ROCSTAR) was developed to assist national wildlife refuges, waterfowl production areas, wetland...

  16. Carbon Monoxide Nonattainment Areas

    Data.gov (United States)

    U.S. Environmental Protection Agency — This data layer identifies areas in the U.S. where air pollution levels have not met the National Ambient Air Quality Standards (NAAQS) for Carbon Monoxide and have...

  17. 200 Area Interim Storage Area Technical Safety Requirements

    Energy Technology Data Exchange (ETDEWEB)

    CARRELL, R.D.

    2000-03-15

    The 200 Area Interim Storage Area Technical Safety Requirements define administrative controls and design features required to ensure safe operation during receipt and storage of canisters containing spent nuclear fuel. This document is based on the 200 Area Interim Storage Area, Annex D, Final Safety Analysis Report which contains information specific to the 200 Area Interim Storage Area.

  18. 5 CFR 591.207 - Which areas are COLA areas?

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Which areas are COLA areas? 591.207... ALLOWANCES AND DIFFERENTIALS Cost-of-Living Allowance and Post Differential-Nonforeign Areas Cost-Of-Living Allowances § 591.207 Which areas are COLA areas? OPM has established the following COLA areas: (a) City...

  19. 5 CFR 591.205 - Which areas are nonforeign areas?

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Which areas are nonforeign areas? 591.205... ALLOWANCES AND DIFFERENTIALS Cost-of-Living Allowance and Post Differential-Nonforeign Areas Cost-Of-Living Allowances and Post Differentials § 591.205 Which areas are nonforeign areas? (a) The nonforeign areas...

  20. Large area LED package

    Science.gov (United States)

    Goullon, L.; Jordan, R.; Braun, T.; Bauer, J.; Becker, F.; Hutter, M.; Schneider-Ramelow, M.; Lang, K.-D.

    2015-03-01

    Solid state lighting using LED-dies is a rapidly growing market. LED-dies with the needed increasing luminous flux per chip area produce a lot of heat. Therefore an appropriate thermal management is required for general lighting with LEDdies. One way to avoid overheating and shorter lifetime is the use of many small LED-dies on a large area heat sink (down to 70 μm edge length), so that heat can spread into a large area while at the same time light also appears on a larger area. The handling with such small LED-dies is very difficult because they are too small to be picked with common equipment. Therefore a new concept called collective transfer bonding using a temporary carrier chip was developed. A further benefit of this new technology is the high precision assembly as well as the plane parallel assembly of the LED-dies which is necessary for wire bonding. It has been shown that hundred functional LED-dies were transferred and soldered at the same time. After the assembly a cost effective established PCB-technology was applied to produce a large-area light source consisting of many small LED-dies and electrically connected on a PCB-substrate. The top contacts of the LED-dies were realized by laminating an adhesive copper sheet followed by LDI structuring as known from PCB-via-technology. This assembly can be completed by adding converting and light forming optical elements. In summary two technologies based on standard SMD and PCB technology have been developed for panel level LED packaging up to 610x 457 mm2 area size.