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Sample records for advanced superconducting electron

  1. Advances in superconducting quantum electronic microcircuit fabrication

    NASA Technical Reports Server (NTRS)

    Kirschman, R. K.; Notarys, H. A.; Mercereau, J. E.

    1975-01-01

    Standard microelectronic fabrication techniques have been utilized to produce batch quantities of superconducting quantum electronic devices and circuits. The overall goal is a fabrication technology yielding circuits that are rugged and stable and capable of being fabricated controllably and reproducibly in sizeable quantities. Our progress toward this goal is presented, with primary emphasis on the most recent work, which includes the use of electron-beam lithography and techniques of hybrid microelectronics. Several prototype microcircuits have been successfully fabricated. These microcircuits are formed in a thin-film parent material consisting of layers of superconducting and normal metals, and use proximity-effect structures as the active circuit elements.

  2. Investigation of relativistic runaway electrons in electron cyclotron resonance heating discharges on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Kang, C. S.; Lee, S. G.

    2014-07-15

    The behavior of relativistic runaway electrons during Electron Cyclotron Resonance Heating (ECRH) discharges is investigated in the Korea Superconducting Tokamak Advanced Research device. The effect of the ECRH on the runaway electron population is discussed. Observations on the generation of superthermal electrons during ECRH will be reported, which will be shown to be consistent with existing theory for the development of a superthermal electron avalanche during ECRH [A. Lazaros, Phys. Plasmas 8, 1263 (2001)].

  3. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Shi, Yuejiang; Fu, Jia; Li, Jiahong; Yang, Yu; Wang, Fudi; Li, Yingying; Zhang, Wei; Wan, Baonian; Chen, Zhongyong

    2010-03-01

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  4. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Shi Yuejiang; Fu Jia; Li Jiahong; Yang Yu; Wang Fudi; Li Yingying; Zhang Wei; Wan Baonian; Chen Zhongyong

    2010-03-15

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  5. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak.

    PubMed

    Shi, Yuejiang; Fu, Jia; Li, Jiahong; Yang, Yu; Wang, Fudi; Li, Yingying; Zhang, Wei; Wan, Baonian; Chen, Zhongyong

    2010-03-01

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  6. Analysis of line integrated electron density using plasma position data on Korea Superconducting Tokamak Advanced Researcha)

    NASA Astrophysics Data System (ADS)

    Nam, Y. U.; Chung, J.

    2010-10-01

    A 280 GHz single-channel horizontal millimeter-wave interferometer system has been installed for plasma electron density measurements on the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This system has a triangular beam path that does not pass through the plasma axis due to geometrical constraints in the superconducting tokamak. The term line density on KSTAR has a different meaning from the line density of other tokamaks. To estimate the peak density and the mean density from the measured line density, information on the position of the plasma is needed. The information has been calculated from tangentially viewed visible images using the toroidal symmetry of the plasma. Interface definition language routines have been developed for this purpose. The calculated plasma position data correspond well to calculation results from magnetic analysis. With the position data and an estimated plasma profile, the peak density and the mean density have been obtained from the line density. From these results, changes of plasma density themselves can be separated from effects of the plasma movements, so they can give valuable information on the plasma status.

  7. Advanced Beamline Design for Fermilab's Advanced Superconducting Test Accelerator

    SciTech Connect

    Prokop, Christopher

    2014-01-01

    The Advanced Superconducting Test Accelerator (ASTA) at Fermilab is a new electron accelerator currently in the commissioning stage. In addition to testing superconducting accelerating cavities for future accelerators, it is foreseen to support a variety of Advanced Accelerator R&D (AARD) experiments. Producing the required electron bunches with the expected flexibility is challenging. The goal of this dissertation is to explore via numerical simulations new accelerator beamlines that can enable the advanced manipulation of electron bunches. The work especially includes the design of a low-energy bunch compressor and a study of transverse-to-longitudinal phase space exchangers.

  8. Design and characterization of a 32-channel heterodyne radiometer for electron cyclotron emission measurements on experimental advanced superconducting tokamak

    SciTech Connect

    Han, X.; Liu, X.; Liu, Y. Li, E. Z.; Hu, L. Q.; Gao, X.; Domier, C. W.; Luhmann, N. C.

    2014-07-15

    A 32-channel heterodyne radiometer has been developed for the measurement of electron cyclotron emission (ECE) on the experimental advanced superconducting tokamak (EAST). This system collects X-mode ECE radiation spanning a frequency range of 104–168 GHz, where the frequency coverage corresponds to a full radial coverage for the case with a toroidal magnetic field of 2.3 T. The frequency range is equally spaced every 2 GHz from 105.1 to 167.1 GHz with an RF bandwidth of ∼500 MHz and the video bandwidth can be switched among 50, 100, 200, and 400 kHz. Design objectives and characterization of the system are presented in this paper. Preliminary results for plasma operation are also presented.

  9. Space applications of superconductivity - Digital electronics

    NASA Technical Reports Server (NTRS)

    Harris, R. E.

    1980-01-01

    Superconducting electronics offers a variety of remarkable properties including high speed and low dissipation. The paper discusses fundamental considerations which appear to suggest that superconducting (cryogenic) technology will offer significant advantages for future digital devices. It shows how the active element in superconducting electronics, the Josephson junction, works and discusses the technology for fabricating the devices. The characteristics of published circuits are briefly reviewed, and the capabilities of future superconducting computers and instruments are projected.

  10. Nuclear Electronics: Superconducting Detectors and Processing Techniques

    NASA Astrophysics Data System (ADS)

    Polushkin, Vladimir

    2004-06-01

    With the commercialisation of superconducting particles and radiation detectors set to occur in the very near future, nuclear analytical instrumentation is taking a big step forward. These new detectors have a high degree of accuracy, stability and speed and are suitable for high-density multiplex integration in nuclear research laboratories and astrophysics. Furthermore, superconducting detectors can also be successfully applied to food safety, airport security systems, medical examinations, doping tests & forensic investigations. This book is the first to address a new generation of analytical tools based on new superconductor detectors demonstrating outstanding performance unsurpassed by any other conventional devices. Presenting the latest research and development in nanometer technologies and biochemistry this book: * Discusses the development of nuclear sensing techniques. * Provides guidance on the design and use of the next generation of detectors. * Describes cryogenic detectors for nuclear measurements and spectrometry. * Covers primary detectors, front-end readout electronics and digital signal processing. * Presents applications in nanotechnology and modern biochemistry including DNA sequencing, proteinomics, microorganisms. * Features examples of two applications in X-ray electron probe nanoanalysis and time-of-flight mass spectrometry. This comprehensive treatment is the ideal reference for researchers, industrial engineers and graduate students involved in the development of high precision nuclear measurements, nuclear analytical instrumentation and advanced superconductor primary sensors. This book will also appeal to physicists, electrical and electronic engineers in the nuclear industry.

  11. Exotic Superconductivity in Correlated Electron Systems

    SciTech Connect

    Mu, Gang; Sandu, Viorel; Li, Wei; Shen, Bing

    2015-05-25

    Over the past decades, the search for high-Tc superconductivity (SC) and its novel superconducting mechanisms is one of the most challenging tasks of condensed matter physicists and material scientists, wherein the most striking achievement is the discovery of high-c and unconventional superconductivity in strongly correlated 3d-electron systems, such as cuprates and iron pnictides/chalcogenides. Those exotic superconductors display the behaviors beyond the scope of the BCS theory (in the SC states) and the Landau-Fermi liquid theory (in the normal states). In general, such exotic superconductivity can be seen as correlated electron systems, where there are strong interplays among charge, spin, orbital, and lattice degrees of freedom. Thus, we focus on the exotic superconductivity in materials with correlated electrons in the present special issue.

  12. Exotic Superconductivity in Correlated Electron Systems

    DOE PAGES

    Mu, Gang; Sandu, Viorel; Li, Wei; ...

    2015-05-25

    Over the past decades, the search for high-Tc superconductivity (SC) and its novel superconducting mechanisms is one of the most challenging tasks of condensed matter physicists and material scientists, wherein the most striking achievement is the discovery of high-c and unconventional superconductivity in strongly correlated 3d-electron systems, such as cuprates and iron pnictides/chalcogenides. Those exotic superconductors display the behaviors beyond the scope of the BCS theory (in the SC states) and the Landau-Fermi liquid theory (in the normal states). In general, such exotic superconductivity can be seen as correlated electron systems, where there are strong interplays among charge, spin, orbital,more » and lattice degrees of freedom. Thus, we focus on the exotic superconductivity in materials with correlated electrons in the present special issue.« less

  13. Recent advances in superconducting-mixer simulations

    NASA Technical Reports Server (NTRS)

    Withington, S.; Kennedy, P. R.

    1992-01-01

    Over the last few years, considerable progress have been made in the development of techniques for fabricating high-quality superconducting circuits, and this success, together with major advances in the theoretical understanding of quantum detection and mixing at millimeter and submillimeter wavelengths, has made the development of CAD techniques for superconducting nonlinear circuits an important new enterprise. For example, arrays of quasioptical mixers are now being manufactured, where the antennas, matching networks, filters and superconducting tunnel junctions are all fabricated by depositing niobium and a variety of oxides on a single quartz substrate. There are no adjustable tuning elements on these integrated circuits, and therefore, one must be able to predict their electrical behavior precisely. This requirement, together with a general interest in the generic behavior of devices such as direct detectors and harmonic mixers, has lead us to develop a range of CAD tools for simulating the large-signal, small-signal, and noise behavior of superconducting tunnel junction circuits.

  14. Superconducting analogue electronics for research and industry

    NASA Astrophysics Data System (ADS)

    Winkler, D.

    2003-12-01

    This paper gives a brief review of superconducting electronics in research and industry. Examples will show how science benefits from the development and how superconducting devices have found their way into industry and to some commercial products. Impact in terms of enabling new research in other fields (e.g. radio astronomy, medicine), in industry (certification, safety, metrology, etc) and in terms of market will be addressed. From the examples, two fields will be emphasized: superconducting detectors for astronomy and the superconducting quantum interference devices (SQUIDs) employed for different applications.

  15. Commercial Superconducting Electron Linac for Radioisotope Production

    SciTech Connect

    Grimm, Terry Lee; Boulware, Charles H.; Hollister, Jerry L.; Jecks, Randall W.; Mamtimin, Mayir; Starovoitova, Valeriia

    2015-08-13

    The majority of radioisotopes used in the United States today come from foreign suppliers or are generated parasitically in large government accelerators and nuclear reactors. Both of these restrictions limit the availability of radioisotopes and discourage the development and evaluation of new isotopes and for nuclear medicine, science, and industry. Numerous studies have been recommending development of dedicated accelerators for production of radioisotopes for over 20 years (Institute of Medicine, 1995; Reba, et al, 2000; National Research Council, 2007; NSAC 2009). The 2015 NSAC Long Range Plan for Isotopes again identified electron accelerators as an area for continued research and development. Recommendation 1(c) from the 2015 NSAC Isotope report specifically identifies electron accelerators for continued funding for the purpose of producing medical and industrial radioisotopes. Recognizing the pressing need for new production methods of radioisotopes, the United States Congress passed the American Medical Isotope Production Act of 2012 to develop a domestic production of 99Mo and to eliminate the use of highly enriched uranium (HEU) in the production of 99Mo. One of the advantages of high power electron linear accelerators (linacs) is they can create both proton- and neutron-rich isotopes by generating high energy x-rays that knock out protons or neutrons from stable atoms or by fission of uranium. This allows for production of isotopes not possible in nuclear reactors. Recent advances in superconducting electron linacs have decreased the size and complexity of these systems such that they are economically competitive with nuclear reactors and large, high energy accelerators. Niowave, Inc. has been developing a radioisotope production facility based on a superconducting electron linac with liquid metal converters.

  16. The Advanced Superconducting Test Accelerator at Fermilab: Science Program

    SciTech Connect

    Piot, Philippe; Harms, Elvin; Henderson, Stuart; Leibfritz, Jerry; Nagaitsev, Sergei; Shiltsev, Vladimir; Valishev, Alexander

    2014-07-01

    The Advanced Superconducting Test Accelerator (ASTA) currently in commissioning phase at Fermilab is foreseen to support a broad range of beam-based experiments to study fundamental limitations to beam intensity and to develop novel approaches to particle-beam generation, acceleration and manipulation. ASTA incorporates a superconducting radiofrequency (SCRF) linac coupled to a flexible high-brightness photoinjector. The facility also includes a small-circumference storage ring capable of storing electrons or protons. This report summarizes the facility capabilities, and provide an overview of the accelerator-science researches to be enabled.

  17. Electron Source based on Superconducting RF

    NASA Astrophysics Data System (ADS)

    Xin, Tianmu

    High-bunch-charge photoemission electron-sources operating in a Continuous Wave (CW) mode can provide high peak current as well as the high average current which are required for many advanced applications of accelerators facilities, for example, electron coolers for hadron beams, electron-ion colliders, and Free-Electron Lasers (FELs). Superconducting Radio Frequency (SRF) has many advantages over other electron-injector technologies, especially when it is working in CW mode as it offers higher repetition rate. An 112 MHz SRF electron photo-injector (gun) was developed at Brookhaven National Laboratory (BNL) to produce high-brightness and high-bunch-charge bunches for electron cooling experiments. The gun utilizes a Quarter-Wave Resonator (QWR) geometry for a compact structure and improved electron beam dynamics. The detailed RF design of the cavity, fundamental coupler and cathode stalk are presented in this work. A GPU accelerated code was written to improve the speed of simulation of multipacting, an important hurdle the SRF structure has to overcome in various locations. The injector utilizes high Quantum Efficiency (QE) multi-alkali photocathodes (K2CsSb) for generating electrons. The cathode fabrication system and procedure are also included in the thesis. Beam dynamic simulation of the injector was done with the code ASTRA. To find the optimized parameters of the cavities and beam optics, the author wrote a genetic algorithm Python script to search for the best solution in this high-dimensional parameter space. The gun was successfully commissioned and produced world record bunch charge and average current in an SRF photo-injector.

  18. Advanced Manufacturing of Superconducting Magnets

    NASA Technical Reports Server (NTRS)

    Senti, Mark W.

    1996-01-01

    The development of specialized materials, processes, and robotics technology allows for the rapid prototype and manufacture of superconducting and normal magnets which can be used for magnetic suspension applications. Presented are highlights of the Direct Conductor Placement System (DCPS) which enables automatic design and assembly of 3-dimensional coils and conductor patterns using LTS and HTS conductors. The system enables engineers to place conductors in complex patterns with greater efficiency and accuracy, and without the need for hard tooling. It may also allow researchers to create new types of coils and patterns which were never practical before the development of DCPS. The DCPS includes a custom designed eight-axis robot, patented end effector, CoilCAD(trademark) design software, RoboWire(trademark) control software, and automatic inspection.

  19. The integration of cryogenic cooling systems with superconducting electronic systems

    SciTech Connect

    Green, Michael A.

    2003-07-01

    The need for cryogenic cooling has been critical issue that has kept superconducting electronic devices from reaching the market place. Even though the performance of the superconducting circuit is superior to silicon electronics, the requirement for cryogenic cooling has put the superconducting devices at a disadvantage. This report will talk about the various methods for refrigerating superconducting devices. Cryocooler types will be compared for vibration, efficiency, and cost. Some solutions to specific problems of integrating cryocoolers to superconducting devices are presented.

  20. European roadmap on superconductive electronics - status and perspectives

    NASA Astrophysics Data System (ADS)

    Anders, S.; Blamire, M. G.; Buchholz, F.-Im.; Crété, D.-G.; Cristiano, R.; Febvre, P.; Fritzsch, L.; Herr, A.; Il'ichev, E.; Kohlmann, J.; Kunert, J.; Meyer, H.-G.; Niemeyer, J.; Ortlepp, T.; Rogalla, H.; Schurig, T.; Siegel, M.; Stolz, R.; Tarte, E.; ter Brake, H. J. M.; Toepfer, H.; Villegier, J.-C.; Zagoskin, A. M.; Zorin, A. B.

    2010-12-01

    . Quantum measurement instrumentation. Advanced analogue-to-digital converters. Superconductive electronics technology.

  1. Superconducting cuprate heterostructures for hot electron bolometers

    NASA Astrophysics Data System (ADS)

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-11-01

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La2-xSrxCuO4 layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV ˜γI3, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ /dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area ge -ph≈1 W/K cm2 at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

  2. Superconducting cuprate heterostructures for hot electron bolometers

    SciTech Connect

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-11-25

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La{sub 2−x}Sr{sub x}CuO{sub 4} layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV∼γI{sup 3}, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ/dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area g{sub e−ph}≈1 W/K cm{sup 2} at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

  3. Electron-phonon superconductivity in YIn3

    NASA Astrophysics Data System (ADS)

    Billington, D.; Llewellyn-Jones, T. M.; Maroso, G.; Dugdale, S. B.

    2013-08-01

    First-principles calculations of the electron-phonon coupling were performed on the cubic intermetallic compound YIn3. The electron-phonon coupling constant was found to be λep = 0.42. Using the Allen-Dynes formula with a Coulomb pseudopotential of μ* = 0.10, a Tc of approximately 0.77 K is obtained which is reasonably consistent with the experimentally observed temperature (between 0.8 and 1.1 K). The results indicate that conventional electron-phonon coupling is capable of producing the superconductivity in this compound.

  4. Superconducting 112 MHz QWR electron gun

    SciTech Connect

    Belomestnykh, S.; Ben-Zvi, I.; Boulware, C.H.; Chang, X.; Grimm, T.L.; Rao, T.; Siegel, B.; Skaritka, J.; Than, R.; Winowski, M.; Wu, Q.; Xin, T.; Xue, L.

    2011-07-25

    Brookhaven National Laboratory and Niowave, Inc. have designed and fabricated a superconducting 112 MHz quarter-wave resonator (QWR) electron gun. The first cold test of the QWR cryomodule has been completed at Niowave. The paper describes the cryomodule design, presents the cold test results, and outline plans to upgrade the cryomodule. Future experiments include studies of different photocathodes and use for the coherent electron cooling proof-of-principle experiment. Two cathode stalk options, one for multi-alkali photocathodes and the other one for a diamond-amplified photocathode, are discussed. A quarter-wave resonator concept of superconducting RF (SRF) electron gun was proposed at BNL for electron cooling hadron beams in RHIC. QWRs can be made sufficiently compact even at low RF frequencies (long wavelengths). The long wavelength allows to produce long electron bunches, thus minimizing space charge effects and enabling high bunch charge. Also, such guns should be suitable for experiments requiring high average current electron beams. A 112 MHz QWR gun was designed, fabricated, and cold-tested in collaboration between BNL and Niowave. This is the lowest frequency SRF gun ever tested successfully. In this paper we describe the gun design and fabrication, present the cold test results, and outline our plans. This gun will also serve as a prototype for a future SRF gun to be used for coherent electron cooling of hadrons in eRHIC.

  5. Superconducting Quantum Interference Single-Electron Transistor

    NASA Astrophysics Data System (ADS)

    Enrico, Emanuele; Giazotto, Francesco

    2016-06-01

    We propose the concept of a quantized single-electron source based on the interplay between Coulomb blockade and magnetic flux-controllable superconducting proximity effect. We show that flux dependence of the induced energy gap in the density of states of a nanosized metallic wire can be exploited as an efficient tunable energy barrier which enables charge-pumping configurations with enhanced functionalities. This control parameter strongly affects the charging landscape of a normal metal island with non-negligible Coulombic energy. Under a suitable evolution of a time-dependent magnetic flux the structure behaves like a turnstile for single electrons in a fully electrostatic regime.

  6. Magnetic imaging of moat-guarded superconducting electronic circuits

    NASA Astrophysics Data System (ADS)

    Jeffery, Mark; Van Duzer, T.; Kirtley, J. R.; Ketchen, M. B.

    1995-09-01

    Superconducting electronic circuits surrounded by various configurations of holes in the superconducting ground plane have been imaged using a high resolution scanning superconducting quantum interference device (SQUID) microscope. These data demonstrate that in the weak field limit continuous moats trap flux more effectively to protect the circuits than small holes in the same configuration.

  7. Advanced Electronic Technology.

    DTIC Science & Technology

    1978-11-15

    It AD AObS 062 MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB F/S 9/S ADVANCED ELECTRONIC TECHNOLOGY .(U) NOV 78 A J MCLAUGHLIN. A L MCWHORTER...T I T U T E OF T E C H N O L O G Y L I N C O L N L A B O R A T O R Y ADVANCED ELECTRONIC TECHNOLOGY QUARTERLY TECKNICAL SUMMAR Y REPORT TO THE AIR...Division 8 (Solid State) on the Advanced Electronic Technology Program. Hi

  8. Superconductivity: from Electron Interaction to Nuclear Superfluidity

    NASA Astrophysics Data System (ADS)

    Pines, David

    I present an expanded version of a talk given at the Urbana symposium that celebrated the fiftieth anniversary of the publication of the microscopic theory of superconductivity by Bardeen, Cooper, and Schrieffer — BCS. I recall at some length, the work with my Ph.D. mentor, David Bohm, and my postdoctoral mentor, John Bardeen, on electron interaction in metals during the period 1948-55 that helped pave the way for BCS, describe the immediate impact of BCS on a small segment of the Princeton physics community in the early spring of 1957, and discuss the extent to which the Bardeen-Pines-Frohlich effective electron-electron interaction provided a criterion for superconductivity in the periodic system. I describe my lectures on BCS at Niels Bohr's Institute of Theoretical Physics in June 1957 that led to the proposal of nuclear superfluidity, discuss nuclear and cosmic superfluids briefly, and close with a tribute to John Bardeen, whose birth centennial we celebrated in 2008, and who was my mentor, close colleague, and dear friend.

  9. New Advance in SuperConducting Materials

    SciTech Connect

    2009-03-02

    Superconducting materials will transform the world's electrical infrastructure, saving billions of dollars once the technical details and installation are in place. At Los Alamos National Laborator...  

  10. Electron-phonon superconductivity in BaSn5

    NASA Astrophysics Data System (ADS)

    Billington, David; Ernsting, David; Millichamp, Thomas E.; Dugdale, Stephen B.

    2015-05-01

    First-principles calculations of the electronic structure and phonon dispersion relation of the superconducting compound ? were performed. This has allowed the calculation of the electron-phonon matrix elements from which the electron-phonon coupling constant was found to be ?. Application of the Allen-Dynes formula with ? yielded a superconducting transition temperature of ? K. The calculated ? agrees well with the available experimental data and indicates that ? is an electron-phonon superconductor with intermediate strength electron-phonon coupling.

  11. New Advance in SuperConducting Materials

    ScienceCinema

    None

    2016-07-12

    Superconducting materials will transform the world's electrical infrastructure, saving billions of dollars once the technical details and installation are in place. At Los Alamos National Laborator...  

  12. New Advances in SuperConducting Materials

    ScienceCinema

    None

    2016-07-12

    Superconducting materials will transform the world's electrical infrastructure, saving billions of dollars once the technical details and installation are in place. At Los Alamos National Laboratory, new materials science concepts are bringing this essential technology closer to widespread industrial use.

  13. High-Density Superconducting Cables for Advanced ACTPol

    NASA Technical Reports Server (NTRS)

    Pappas, C. G.; Austermann, J.; Beall, J. A.; Duff, S. M.; Gallardo, P. A.; Grace, E.; Henderson, S. W.; Ho, S. P.; Koopman, B. J.; Li, D.; McMahon, J.; Nati, F.; Niemack, M. D.; Niraula, P.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Simon, S. M.; Staggs, S. T.; Vavagiakis, E. M.; Ward, J. T.; Wollack, E. J.

    2016-01-01

    Advanced ACTPol (AdvACT) is an upcoming Atacama Cosmology Telescope (ACT) receiver upgrade, scheduled to deploy in 2016, that will allow measure- ment of the cosmic microwave background polarization and temperature to the highest precision yet with ACT. The AdvACT increase in sensitivity is partly provided by an increase in the number of transition-edge sensors (TESes) per array by up to a factor of two over the current ACTPol receiver detector arrays. The high-density AdvACT TES arrays require 70 µ m pitch superconducting flexible cables (flex) to connect the detec- tor wafer to the first-stage readout electronics. Here, we present the flex fabrication process and test results. For the flex wiring layer, we use a 400-nm-thick sputtered alu- minum film. In the center of the cable, the wiring is supported by a polyimide substrate, which smoothly transitions to a bare (uncoated with polyimide) silicon substrate at the ends of the cable for a robust wedge wire-bonding interface. Tests on the first batch of flex made for the first AdvACT array show that the flex will meet the requirements for AdvACT, with a superconducting critical current above 1 mA at 500 mK, resilience to mechanical and cryogenic stress, and a room temperature yield of 97%.

  14. High-Density Superconducting Cables for Advanced ACTPol

    NASA Astrophysics Data System (ADS)

    Pappas, C. G.; Austermann, J.; Beall, J. A.; Duff, S. M.; Gallardo, P. A.; Grace, E.; Henderson, S. W.; Ho, S. P.; Koopman, B. J.; Li, D.; McMahon, J.; Nati, F.; Niemack, M. D.; Niraula, P.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Simon, S. M.; Staggs, S. T.; Stevens, J. R.; Vavagiakis, E. M.; Ward, J. T.; Wollack, E. J.

    2016-07-01

    Advanced ACTPol (AdvACT) is an upcoming Atacama Cosmology Telescope (ACT) receiver upgrade, scheduled to deploy in 2016, that will allow measurement of the cosmic microwave background polarization and temperature to the highest precision yet with ACT. The AdvACT increase in sensitivity is partly provided by an increase in the number of transition-edge sensors (TESes) per array by up to a factor of two over the current ACTPol receiver detector arrays. The high-density AdvACT TES arrays require 70 \\upmu m pitch superconducting flexible cables (flex) to connect the detector wafer to the first-stage readout electronics. Here, we present the flex fabrication process and test results. For the flex wiring layer, we use a 400-nm-thick sputtered aluminum film. In the center of the cable, the wiring is supported by a polyimide substrate, which smoothly transitions to a bare (uncoated with polyimide) silicon substrate at the ends of the cable for a robust wedge wire-bonding interface. Tests on the first batch of flex made for the first AdvACT array show that the flex will meet the requirements for AdvACT, with a superconducting critical current above 1 mA at 500 mK, resilience to mechanical and cryogenic stress, and a room temperature yield of 97 %.

  15. Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Nguyen, H. Q.; Peltonen, J. T.; Meschke, M.; Pekola, J. P.

    2016-11-01

    Microrefrigerators that operate in the subkelvin regime are key devices in quantum technology. A well-studied candidate, an electronic cooler using normal-metal-insulator-superconductor (N -I -S ) tunnel junctions, offers substantial performance and power. However, its superconducting electrodes are severely overheated due to exponential suppression of their thermal conductance towards low temperatures, and the cooler performs unsatisfactorily—especially in powerful devices needed for practical applications. We employ a second N -I -S cooling stage to thermalize the hot superconductor at the backside of the main N -I -S cooler. Not only providing a lower bath temperature, the second-stage cooler actively evacuates quasiparticles out of the hot superconductor, especially in the low-temperature limit. We demonstrate the apparent advantage of our approach. This cascade design can also be employed to manage excess heat in other cryoelectronic devices.

  16. Superconducting Microwave Electronics at Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Bhasin, Kul B.; Leonard, Regis F.

    1991-01-01

    Over the last three years, NASA Lewis Research Center has investigated the application of newly discovered high temperature superconductors to microwave electronics. Using thin films of YBa2Cu3O7-delta and Tl2Ca2Ba2Cu3Ox deposited on a variety of substrates, including strontium titanate, lanthanum gallate, lanthanum aluminate and magnesium oxide, a number of microwave circuits have been fabricated and evaluated. These include a cavity resonator at 60 GHz, microstrip resonators at 35 GHz, a superconducting antenna array at 35 GHz, a dielectric resonator at 9 GHz, and a microstrip filter at 5 GHz. Performance of some of these circuits as well as suggestions for other applications are reported.

  17. Electronic structure and superconductivity of FeSe-related superconductors.

    PubMed

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  18. PREFACE: ISEC 2005: The 10th International Superconductive Electronics Conference

    NASA Astrophysics Data System (ADS)

    Rogalla, Horst

    2006-05-01

    The 10th International Superconductive Electronics Conference took place in Noordwijkerhout in the Netherlands, 5-9 September 2005, not far from the birthplace of superconductivity in Leiden nearly 100 years ago. There have been many reasons to celebrate the 10th ISEC: not only was it the 20th anniversary, but also the achievements since the first conference in Tokyo in 1987 are tremendous. We have seen whole new groups of superconductive materials come into play, such as oxide superconductors with maximum Tc in excess of 100 K, carbon nanotubes, as well as the realization of new digital concepts from saturation logic to the ultra-fast RSFQ-logic. We have learned that superconductors not only show s-wave symmetries in the spatial arrangement of the order parameter, but also that d-wave dependence in oxide superconductors is now well accepted and can even be successfully applied to digital circuits. We are now used to operating SQUIDs in liquid nitrogen; fT sensitivity of SQUID magnetometers is not surprising anymore and can even be reached with oxide-superconductor based SQUIDs. Even frequency discriminating wide-band single photon detection with superconductive devices, and Josephson voltage standards with tens of thousands of junctions, nowadays belong to the daily life of advanced laboratories. ISEC has played a very important role in this development. The first conferences were held in 1987 and 1989 in Tokyo, and subsequently took place in Glasgow (UK), Boulder (USA), Nagoya (Japan), Berlin (Germany), Berkeley (USA), Osaka (Japan), Sydney (Australia), and in 2005 for the first time in the Netherlands. These conferences have provided platforms for the presentation of the research and development results of this community and for the vivid discussion of achievements and strategies for the further development of superconductive electronics. The 10th conference has played a very important role in this context. The results in laboratories show great potential and

  19. Superconductivity of the magnetized electron gas of a quantum cylinder

    SciTech Connect

    Eminov, P. A. Sezonov, Yu. I.

    2008-10-15

    A microscopic theory of superconductivity is developed for the magnetized electron gas on a cylindrical surface. The Gibbs free energy is calculated for the superconducting system. A gap equation is derived that determines the critical temperature as a function of the quantum-cylinder dimensions and the Aharonov-Bohm parameter. It is shown that the gap not only exhibits Aharonov-Bohm oscillations, but also oscillates with varying curvature of the cylindrical surface.

  20. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-15

    An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.

  1. Diamagnetic loop measurement in Korea Superconducting Tokamak Advanced Research machine.

    PubMed

    Bak, J G; Lee, S G; Kim, H S

    2011-06-01

    Diamagnetic loop (DL), which consists of two poloidal loops inside the vacuum vessel, is used to measure the diamagnetic flux during a plasma discharge in the Korea Superconducting Tokamak Advanced Research (KSTAR) machine. The vacuum fluxes in the DL signal can be compensated up to 0.1 mWb by using the coefficients, which are obtained from experimental investigations, in the vacuum flux measurements during vacuum shots under same operational conditions of magnetic coils for plasma experiment in the KSTAR machine. The maximum error in the diamagnetic flux measurement due to the errors of the coefficients was estimated as ∼0.22 mWb. From the diamagnetic flux measurements for the ohmically heated circular plasmas in the KSTAR machine, the stored energy agrees well with the estimated kinetic energy within the discrepancy of 25%. When the electron cyclotron heating, the neutral beam injection, and the ion cyclotron resonance heating are added to the ohmically heated limiter plasmas, the additional heating effects can be clearly observed from the increase of the stored energy evaluated in the DL measurement.

  2. Diamagnetic loop measurement in Korea Superconducting Tokamak Advanced Research machine

    SciTech Connect

    Bak, J. G.; Lee, S. G.; Kim, H. S.

    2011-06-15

    Diamagnetic loop (DL), which consists of two poloidal loops inside the vacuum vessel, is used to measure the diamagnetic flux during a plasma discharge in the Korea Superconducting Tokamak Advanced Research (KSTAR) machine. The vacuum fluxes in the DL signal can be compensated up to 0.1 mWb by using the coefficients, which are obtained from experimental investigations, in the vacuum flux measurements during vacuum shots under same operational conditions of magnetic coils for plasma experiment in the KSTAR machine. The maximum error in the diamagnetic flux measurement due to the errors of the coefficients was estimated as {approx}0.22 mWb. From the diamagnetic flux measurements for the ohmically heated circular plasmas in the KSTAR machine, the stored energy agrees well with the estimated kinetic energy within the discrepancy of 25%. When the electron cyclotron heating, the neutral beam injection, and the ion cyclotron resonance heating are added to the ohmically heated limiter plasmas, the additional heating effects can be clearly observed from the increase of the stored energy evaluated in the DL measurement.

  3. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak.

    PubMed

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  4. Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

    SciTech Connect

    Liu, X.; Zhao, H. L.; Liu, Y. Li, E. Z.; Han, X.; Ti, A.; Hu, L. Q.; Zhang, X. D.; Domier, C. W.; Luhmann, N. C.

    2014-09-15

    This paper presents the results of the in situ absolute intensity calibration for the 32-channel heterodyne radiometer on the experimental advanced superconducting tokamak. The hot/cold load method is adopted, and the coherent averaging technique is employed to improve the signal to noise ratio. Measured spectra and electron temperature profiles are compared with those from an independent calibrated Michelson interferometer, and there is a relatively good agreement between the results from the two different systems.

  5. Unconventional superconductivity in low density electron systems and conventional superconductivity in hydrogen metallic alloys

    NASA Astrophysics Data System (ADS)

    Kagan, M. Yu.

    2016-06-01

    In this short review, we first discuss the results, which are mainly devoted to the generalizations of the famous Kohn-Luttinger mechanism of superconductivity in purely repulsive fermion systems at low electron densities. In the context of repulsive- U Hubbard model and Shubin-Vonsovsky model we consider briefly the superconducting phase diagrams and the symmetries of the order parameter in novel strongly correlated electron systems including idealized monolayer and bilayer graphene. We stress that purely repulsive fermion systems are mainly the subject of unconventional low-temperature superconductivity. To get the high temperature superconductivity in cuprates (with T C of the order of 100 K) we should proceed to the t-J model with the van der Waals interaction potential and the competition between short-range repulsion and long-range attraction. Finally we note that to describe superconductivity in metallic hydrogen alloys under pressure (with T C of the order of 200 K) it is reasonable to reexamine more conventional mechanisms connected with electron-phonon interaction. These mechanisms arise in the attractive- U Hubbard model with static onsite or intersite attractive potential or in more realistic theories (which include retardation effects) such as Migdal-Eliashberg strong coupling theory or even Fermi-Bose mixture theory of Ranninger et al. and its generalizations.

  6. Flexible Microstrip Circuits for Superconducting Electronics

    NASA Technical Reports Server (NTRS)

    Chervenak, James; Mateo, Jennette

    2013-01-01

    Flexible circuits with superconducting wiring atop polyimide thin films are being studied to connect large numbers of wires between stages in cryogenic apparatus with low heat load. The feasibility of a full microstrip process, consisting of two layers of superconducting material separated by a thin dielectric layer on 5 mil (approximately 0.13 mm) Kapton sheets, where manageable residual stress remains in the polyimide film after processing, has been demonstrated. The goal is a 2-mil (approximately 0.051-mm) process using spin-on polyimide to take advantage of the smoother polyimide surface for achieving highquality metal films. Integration of microstrip wiring with this polyimide film may require high-temperature bakes to relax the stress in the polyimide film between metallization steps.

  7. Advanced Power Electronics Components

    NASA Technical Reports Server (NTRS)

    Schwarze, Gene E.

    2004-01-01

    This paper will give a description and status of the Advanced Power Electronics Materials and Components Technology program being conducted by the NASA Glenn Research Center for future aerospace power applications. The focus of this research program is on the following: 1) New and/or significantly improved dielectric materials for the development of power capacitors with increased volumetric efficiency, energy density, and operating temperature. Materials being investigated include nanocrystalline and composite ceramic dielectrics and diamond-like carbon films; 2) New and/or significantly improved high frequency, high temperature, low loss soft magnetic materials for the development of transformers/inductors with increased power/energy density, electrical efficiency, and operating temperature. Materials being investigated include nanocrystalline and nanocomposite soft magnetic materials; 3) Packaged high temperature, high power density, high voltage, and low loss SiC diodes and switches. Development of high quality 4H- and 6H- SiC atomically smooth substrates to significantly improve device performance is a major emphasis of the SiC materials program; 4) Demonstration of high temperature (> 200 C) circuits using the components developed above.

  8. Covalent Electron Transfer Theory of Superconductivity

    DTIC Science & Technology

    1992-06-19

    where n. and n, converge to establish the threshold density for the onset of superconductivity. 41 Comparison of ne(t) Inse (O) versus t for W = 0.5, 1...all temperatures according to ne(T) = n(7) - nt(T) , (58) where n() = n(Tc)[ I - nse(T) Inse (O)]. Thus, the fractional contribution of the threshold...approximately -1/2, thereby suggesting that Kerr- v,6t 2. For the transition metals with largely unpolarizable cores of closed p6 shells (i.e., noble gases

  9. Emergence of superconductivity in heavy-electron materials.

    PubMed

    Yang, Yi-feng; Pines, David

    2014-12-23

    Although the pairing glue for the attractive quasiparticle interaction responsible for unconventional superconductivity in heavy-electron materials has been identified as the spin fluctuations that arise from their proximity to a magnetic quantum critical point, there has been no model to describe their superconducting transition at temperature Tc that is comparable to that found by Bardeen, Cooper, and Schrieffer (BCS) for conventional superconductors, where phonons provide the pairing glue. Here we propose such a model: a phenomenological BCS-like expression for Tc in heavy-electron materials that is based on a simple model for the effective range and strength of the spin-fluctuation-induced quasiparticle interaction and reflects the unusual properties of the heavy-electron normal state from which superconductivity emerges. We show that it provides a quantitative understanding of the pressure-induced variation of Tc in the "hydrogen atoms" of unconventional superconductivity, CeCoIn5 and CeRhIn5, predicts scaling behavior and a dome-like structure for Tc in all heavy-electron quantum critical superconductors, provides unexpected connections between members of this family, and quantifies their variations in Tc with a single parameter.

  10. Emergence of superconductivity in heavy-electron materials

    PubMed Central

    Yang, Yi-feng; Pines, David

    2014-01-01

    Although the pairing glue for the attractive quasiparticle interaction responsible for unconventional superconductivity in heavy-electron materials has been identified as the spin fluctuations that arise from their proximity to a magnetic quantum critical point, there has been no model to describe their superconducting transition at temperature Tc that is comparable to that found by Bardeen, Cooper, and Schrieffer (BCS) for conventional superconductors, where phonons provide the pairing glue. Here we propose such a model: a phenomenological BCS-like expression for Tc in heavy-electron materials that is based on a simple model for the effective range and strength of the spin-fluctuation-induced quasiparticle interaction and reflects the unusual properties of the heavy-electron normal state from which superconductivity emerges. We show that it provides a quantitative understanding of the pressure-induced variation of Tc in the “hydrogen atoms” of unconventional superconductivity, CeCoIn5 and CeRhIn5, predicts scaling behavior and a dome-like structure for Tc in all heavy-electron quantum critical superconductors, provides unexpected connections between members of this family, and quantifies their variations in Tc with a single parameter. PMID:25489102

  11. ADVANCED ELECTRONIC PACKAGING TECHNIQUES

    DTIC Science & Technology

    MICROMINIATURIZATION (ELECTRONICS), *PACKAGED CIRCUITS, CIRCUITS, EXPERIMENTAL DATA, MANUFACTURING, NONDESTRUCTIVE TESTING, RESISTANCE (ELECTRICAL), SEMICONDUCTORS, TESTS, THIN FILMS (STORAGE DEVICES), WELDING.

  12. Advanced electron microscopy for advanced materials.

    PubMed

    Van Tendeloo, Gustaaf; Bals, Sara; Van Aert, Sandra; Verbeeck, Jo; Van Dyck, Dirk

    2012-11-08

    The idea of this Review is to introduce newly developed possibilities of advanced electron microscopy to the materials science community. Over the last decade, electron microscopy has evolved into a full analytical tool, able to provide atomic scale information on the position, nature, and even the valency atoms. This information is classically obtained in two dimensions (2D), but can now also be obtained in 3D. We show examples of applications in the field of nanoparticles and interfaces.

  13. Halo current diagnostic system of experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Chen, D. L.; Shen, B.; Granetz, R. S.; Sun, Y.; Qian, J. P.; Wang, Y.; Xiao, B. J.

    2015-10-01

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  14. Halo current diagnostic system of experimental advanced superconducting tokamak

    SciTech Connect

    Chen, D. L.; Shen, B.; Sun, Y.; Qian, J. P. Wang, Y.; Xiao, B. J.; Granetz, R. S.

    2015-10-15

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  15. Halo current diagnostic system of experimental advanced superconducting tokamak.

    PubMed

    Chen, D L; Shen, B; Granetz, R S; Sun, Y; Qian, J P; Wang, Y; Xiao, B J

    2015-10-01

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  16. Design of a high-bunch-charge 112-MHz superconducting RF photoemission electron source

    NASA Astrophysics Data System (ADS)

    Xin, T.; Brutus, J. C.; Belomestnykh, Sergey A.; Ben-Zvi, I.; Boulware, C. H.; Grimm, T. L.; Hayes, T.; Litvinenko, Vladimir N.; Mernick, K.; Narayan, G.; Orfin, P.; Pinayev, I.; Rao, T.; Severino, F.; Skaritka, J.; Smith, K.; Than, R.; Tuozzolo, J.; Wang, E.; Xiao, B.; Xie, H.; Zaltsman, A.

    2016-09-01

    High-bunch-charge photoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers. Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun utilizes a quarter-wave resonator geometry for assuring beam dynamics and uses high quantum efficiency multi-alkali photocathodes for generating electrons.

  17. Electronic thermal conductivity in a superconducting vortex state

    NASA Astrophysics Data System (ADS)

    Adachi, H.; Miranovic, P.; Ichioka, M.; Machida, K.

    2007-10-01

    The longitudinal component of the electronic thermal conductivity κxx in a superconducting vortex state is calculated as a function of magnetic field B. Calculations are performed by taking account of the spatial dependence of normal Green's function g, which was neglected in the previous studies using the Brandt-Pesch-Tewordt method. We discuss the possibility of using κxx(B) as a probe of the pair potential symmetry.

  18. Inward particle transport at high collisionality in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Wang, G. Q.; Ma, J.; Weiland, J.; Zang, Q.

    2013-10-15

    We have made the first drift wave study of particle transport in the Experimental Advanced Superconducting Tokamak (Wan et al., Nucl. Fusion 49, 104011 (2009)). The results reveal that collisions make the particle flux more inward in the high collisionality regime. This can be traced back to effects that are quadratic in the collision frequency. The particle pinch is due to electron trapping which is not very efficient in the high collisionality regime so the approach to equilibrium is slow. We have included also the electron temperature gradient (ETG) mode to give the right electron temperature gradient, since the Trapped Electron Mode (TE mode) is weak in this regime. However, at the ETG mode number ions are Boltzmann distributed so the ETG mode does not give particle transport.

  19. Application of visible bremsstrahlung to Z{sub eff} measurement on the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Chen, Yingjie; Wu, Zhenwei; Gao, Wei; Ti, Ang; Zhang, Ling; Jie, Yinxian; Zhang, Jizong; Huang, Juan; Xu, Zong; Zhao, Junyu

    2015-02-15

    The multi-channel visible bremsstrahlung measurement system has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to providing effective ion charge Z{sub eff} as a routine diagnostic, this diagnostic can also be used to estimate other parameters. With the assumption that Z{sub eff} can be seen as constant across the radius and does not change significantly during steady state discharges, central electron temperature, averaged electron density, electron density profile, and plasma current density profile have been obtained based on the scaling of Z{sub eff} with electron density and the relations between Z{sub eff} and these parameters. The estimated results are in good coincidence with measured values, providing an effective and convenient method to estimate other plasma parameters.

  20. Simulated Performance of the Wisconsin Superconducting Electron Gun

    SciTech Connect

    R.A. Bosch, K.J. Kleman, R.A. Legg

    2012-07-01

    The Wisconsin superconducting electron gun is modeled with multiparticle tracking simulations using the ASTRA and GPT codes. To specify the construction of the emittance-compensation solenoid, we studied the dependence of the output bunch's emittance upon the solenoid's strength and field errors. We also evaluated the dependence of the output bunch's emittance upon the bunch's initial emittance and the size of the laser spot on the photocathode. The results suggest that a 200-pC bunch with an emittance of about one mm-mrad can be produced for a free-electron laser.

  1. Electronic structure and relaxation dynamics in a superconducting topological material

    PubMed Central

    Neupane, Madhab; Ishida, Yukiaki; Sankar, Raman; Zhu, Jian-Xin; Sanchez, Daniel S.; Belopolski, Ilya; Xu, Su-Yang; Alidoust, Nasser; Hosen, M. Mofazzel; Shin, Shik; Chou, Fangcheng; Hasan, M. Zahid; Durakiewicz, Tomasz

    2016-01-01

    Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc ~ 3 K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc ~ 2.5 K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excited topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. Our results will be helpful in understanding low temperature superconducting states of these topological materials. PMID:26936229

  2. Electronic structure and relaxation dynamics in a superconducting topological material

    SciTech Connect

    Neupane, Madhab; Ishida, Yukiaki; Sankar, Raman; Zhu, Jian-Xin; Sanchez, Daniel S.; Belopolski, Ilya; Xu, Su-Yang; Alidoust, Nasser; Hosen, M. Mofazzel; Shin, Shik; Chou, Fangcheng; Hasan, M. Zahid; Durakiewicz, Tomasz

    2016-03-03

    Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc~3K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc~2.5K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excited topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. In conclusion, our results will be helpful in understanding low temperature superconducting states of these topological materials.

  3. Electronic structure and relaxation dynamics in a superconducting topological material

    DOE PAGES

    Neupane, Madhab; Ishida, Yukiaki; Sankar, Raman; ...

    2016-03-03

    Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc~3K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc~2.5K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excitedmore » topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. In conclusion, our results will be helpful in understanding low temperature superconducting states of these topological materials.« less

  4. High temperature superconducting films and multilayers for electronics

    NASA Astrophysics Data System (ADS)

    Gavaler, John R.; Talvacchio, John

    1994-04-01

    The overall objective of this program was to develop a materials and fundamental device base for high-transition-temperature superconducting (HTS) electronics capable of operating at greater than 50K. Progress is reported on four tasks which address problems fundamental to the understanding of the superconducting state in HTS films, the application of HTS films in passive microwave circuits, the realization of HTS digital electronics, and the development of new superconducting devices. Large-area epitaxial YBCO films with low RF losses developed under this program and techniques for depositing them on both sides of single-crystal substrates were used in other Westinghouse and government-funded programs to develop HTS channelized filterbanks, delay lines, UHF antenna matching networks, and low-phase-noise resonators. An understanding was achieved of the role of oxygenation during film growth and the effect of film microstructure on RF losses. For HTS digital circuit fabrication, both active devices step-edge and edge-type YBCO Josephson junctions and trilayer BKBO junctions and passive structures were developed, such as crossovers, vias, and contacts. These capabilities were transfered to other Westinghouse and government-funded programs which demonstrated the first HTS SFQ circuits and SQUID's with integrated ground planes.

  5. Design of vibration compensation interferometer for Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Li, G. S.; Liu, H. Q.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zhu, X.; Wang, Z. X.; Zeng, L.; Zou, Z. Y.; Wei, X. C.; Lan, T.

    2014-11-01

    A vibration compensation interferometer (wavelength at 0.532 μm) has been designed and tested for Experimental Advanced Superconducting Tokamak (EAST). It is designed as a sub-system for EAST far-infrared (wavelength at 432.5 μm) poloarimeter/interferometer system. Two Acoustic Optical Modulators have been applied to produce the 1 MHz intermediate frequency. The path length drift of the system is lower than 2 wavelengths within 10 min test, showing the system stability. The system sensitivity has been tested by applying a periodic vibration source on one mirror in the system. The vibration is measured and the result matches the source period. The system is expected to be installed on EAST by the end of 2014.

  6. Microwave Doppler reflectometer system in the Experimental Advanced Superconducting Tokamak.

    PubMed

    Zhou, C; Liu, A D; Zhang, X H; Hu, J Q; Wang, M Y; Li, H; Lan, T; Xie, J L; Sun, X; Ding, W X; Liu, W D; Yu, C X

    2013-10-01

    A Doppler reflectometer system has recently been installed in the Experimental Advanced Superconducting (EAST) Tokamak. It includes two separated systems, one for Q-band (33-50 GHz) and the other for V-band (50-75 GHz). The optical system consists of a flat mirror and a parabolic mirror which are optimized to improve the spectral resolution. A synthesizer is used as the source and a 20 MHz single band frequency modulator is used to get a differential frequency for heterodyne detection. Ray tracing simulations are used to calculate the scattering location and the perpendicular wave number. In EAST last experimental campaign, the Doppler shifted signals have been obtained and the radial profiles of the perpendicular propagation velocity during L-mode and H-mode are calculated.

  7. Status of neutron diagnostics on the experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhong, G. Q.; Hu, L. Q.; Pu, N.; Zhou, R. J.; Xiao, M.; Cao, H. R.; Zhu, Y. B.; Li, K.; Fan, T. S.; Peng, X. Y.; Du, T. F.; Ge, L. J.; Huang, J.; Xu, G. S.; Wan, B. N.

    2016-11-01

    Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using 252Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST's harsh γ-ray and electro-magnetic radiation environment.

  8. Filterscope diagnostic system on the Experimental Advanced Superconducting Tokamak (EAST).

    PubMed

    Xu, Z; Wu, Z W; Gao, W; Chen, Y J; Wu, C R; Zhang, L; Huang, J; Chang, J F; Yao, X J; Gao, W; Zhang, P F; Jin, Z; Hou, Y M; Guo, H Y

    2016-11-01

    A filterscope diagnostic system has been mounted to observe the line emission and visible bremsstrahlung emission from plasma on the experimental advanced superconducting tokamak during the 2014 campaign. By this diagnostic system, multiple wavelengths including Dα (656.1 nm), Dγ (433.9 nm), He ii (468.5 nm), Li i (670.8 nm), Li ii (548.3 nm), C iii (465.0 nm), O ii (441.5 nm), Mo i (386.4 nm), W i (400.9 nm), and visible bremsstrahlung radiation (538.0 nm) are monitored with corresponding wavelength filters. All these multi-channel signals are digitized at up to 200 kHz simultaneously. This diagnostic plays a crucial role in studying edge localized modes and H-mode plasmas, due to the high temporal resolution and spatial resolution that have been designed into it.

  9. Status of neutron diagnostics on the experimental advanced superconducting tokamak.

    PubMed

    Zhong, G Q; Hu, L Q; Pu, N; Zhou, R J; Xiao, M; Cao, H R; Zhu, Y B; Li, K; Fan, T S; Peng, X Y; Du, T F; Ge, L J; Huang, J; Xu, G S; Wan, B N

    2016-11-01

    Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using (252)Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST's harsh γ-ray and electro-magnetic radiation environment.

  10. Advanced Antenna-Coupled Superconducting Detector Arrays for CMB Polarimetry

    NASA Astrophysics Data System (ADS)

    Bock, James

    2014-01-01

    We are developing high-sensitivity millimeter-wave detector arrays for measuring the polarization of the cosmic microwave background (CMB). This development is directed to advance the technology readiness of the Inflation Probe mission in NASA's Physics of the Cosmos program. The Inflation Probe is a fourth-generation CMB satellite that will measure the polarization of the CMB to astrophysical limits, characterizing the inflationary polarization signal, mapping large-scale structure based on polarization induced by gravitational lensing, and mapping Galactic magnetic fields through measurements of polarized dust emission. The inflationary polarization signal is produced by a background of gravitational waves from the epoch of inflation, an exponential expansion of space-time in the early universe, with an amplitude that depends on the physical mechanism producing inflation. The inflationary polarization signal may be distinguished by its unique 'B-mode' vector properties from polarization from the density variations that predominantly source CMB temperature anisotropy. Mission concepts for the Inflation Probe are being developed in the US, Europe and Japan. The arrays are based on planar antennas that provide integral beam collimation, polarization analysis, and spectral band definition in a compact lithographed format that eliminates discrete fore-optics such as lenses and feedhorns. The antennas are coupled to transition-edge superconducting bolometers, read out with multiplexed SQUID current amplifiers. The superconducting sensors and readouts developed in this program share common technologies with NASA X-ray and FIR detector applications. Our program targets developments required for space observations, and we discuss our technical progress over the past two years and plans for future development. We are incorporating arrays into active sub-orbital and ground-based experiments, which advance technology readiness while producing state of the art CMB

  11. Superconducting properties and electronic structure of NaBi.

    PubMed

    Kushwaha, S K; Krizan, J W; Xiong, J; Klimczuk, T; Gibson, Q D; Liang, T; Ong, N P; Cava, R J

    2014-05-28

    Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. T(c), the electronic contribution to the specific heat γ, the ΔC(p)/γT(c) ratio, and the Debye temperature are found to be 2.15 K, 3.4 mJ mol(-1) K(-2), 0.78, and 140 K respectively. The calculated electron-phonon coupling constant (λ(ep) = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250 Oe and 115 nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the p(x) and p(y) orbitals of Bi dominate the electronic states at the Fermi Energy.

  12. An electron spectroscopic investigation of high-temperature superconducting oxides

    SciTech Connect

    Rogers, J.W. Jr.; Blair, D.S.

    1987-01-01

    High resolution X-ray Photoelectron and X-ray-excited Auger Electron Spectroscopy (XPS and XAES) have been used to study the electronic structure of La-Sr-Cu and Y-Ba-Cu superconducting oxide surfaces. The experiments were carried out on freshly cleaved (ex-situ) samples at room temperature and the results were compared with spectra obtained from Cu and CuO. The XPS Cu(2p) features show clearly that Cu/sup +2/ (3d/sup 9/) is present in the near surface region of both superconducting oxides and suggests that they are mixed valent containing both 3d/sup 9/ and 3d/sup 10/ contributions. No evidence for Cu/sup +3/ (3d/sup 8/) was found. XAES Cu(LMM) spectral features are consistent with the superposition of mixed valent Cu sites and the hole-hole interaction energies for the Cu(LMM) transitions, a direct experimental measurement of electron correlation in the Cu 3d levels, indicate strong electron correlation. 15 refs., 3 figs.

  13. Superconducting Hot-Electron Submillimeter-Wave Detector

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    A superconducting hot-electron bolometer has been built and tested as a prototype of high-sensitivity, rapid-response detectors of submillimeter-wavelength radiation. There are diverse potential applications for such detectors, a few examples being submillimeter spectroscopy for scientific research; detection of leaking gases; detection of explosive, chemical, and biological weapons; and medical imaging. This detector is a superconducting-transition- edge device. Like other such devices, it includes a superconducting bridge that has a low heat capacity and is maintained at a critical temperature (T(sub c)) at the lower end of its superconducting-transition temperature range. Incident photons cause transient increases in electron temperature through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. In this case, T(sub c) = 6 K, which is approximately the upper limit of the operating-temperature range of silicon-based bolometers heretofore used routinely in many laboratories. However, whereas the response speed of a typical silicon- based laboratory bolometer is characterized by a frequency of the order of a kilohertz, the response speed of the present device is much higher characterized by a frequency of the order of 100 MHz. For this or any bolometer, a useful figure of merit that one seeks to minimize is (NEP)(tau exp 1/2), where NEP denotes the noise-equivalent power (NEP) and the response time. This figure of merit depends primarily on the heat capacity and, for a given heat capacity, is approximately invariant. As a consequence of this approximate invariance, in designing a device having a given heat capacity to be more sensitive (to have lower NEP), one must accept longer response time (slower response) or, conversely, in designing it to respond faster, one must accept lower sensitivity. Hence, further, in order to increase both the speed of response and the sensitivity, one must make the device very small in

  14. Construction and Test of a Novel Superconducting RF Electron gun

    SciTech Connect

    Bisognano, Joseph J.

    2014-04-16

    The University of Wisconsin-Madison has completed installation of a superconducting electron gun. Its concept was optimized to be the source for a CW free electron laser facility with multiple megahertz repetition rate end stations. This VHF superconducting configuration holds the promise of the highest performance for CW injectors. Initial commissioning efforts show that the cavity can achieve gradients of 35 MV/m at the cathode position. With the cathode inserted CW operation has been achieved at 20 MV/m with good control of microphonics, negligible dark current, and Q0 > 3×109 at 4 K. Bunch charges of ~100 pC have been delivered, and first simple beam measurements made. These preliminary results are very encouraging for production of 100s pC bunches with millimeter-milliradian or smaller normalized emittances. Plans are in place to carry out more definitive studies to establish the full capabilities. However, since the grant was not renewed, the electron gun is currently mothballed, and without supplemental fund the opportunity for further work will be lost.

  15. Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

    NASA Astrophysics Data System (ADS)

    Wagner, A.; Anwand, W.; Attallah, A. G.; Dornberg, G.; Elsayed, M.; Enke, D.; Hussein, A. E. M.; Krause-Rehberg, R.; Liedke, M. O.; Potzger, K.; Trinh, T. T.

    2017-01-01

    The Helmholtz-Zentrum Dresden-Rossendorf operates a superconducting linear accelerator for electrons with energies up to 35 MeV and average beam currents up to 1.6 mA. The electron beam is employed for production of several secondary beams including X-rays from bremsstrahlung production, neutrons, and positrons. The secondary positron beam after moderation feeds the Monoenergetic Positron Source (MePS) where positron annihilation lifetime (PALS) and positron annihilation Doppler-broadening experiments in materials science are performed in parallel. The adjustable repetition rate of the continuous-wave electron beams allows matching of the pulse separation to the positron lifetime in the sample under study. The energy of the positron beam can be set between 0.5 keV and 20 keV to perform depth resolved defect spectroscopy and porosity studies especially for thin films.

  16. Conceptual design of industrial free electron laser using superconducting accelerator

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Ulyanov, Yu.N.

    1995-12-31

    Paper presents conceptual design of free electron laser (FEL) complex for industrial applications. The FEL complex consists of three. FEL oscillators with the optical output spanning the infrared (IR) and ultraviolet (UV) wave-lengths ({lambda} = 0.3...20 {mu}m) and with the average output power 10 - 20 kW. The driving beam for the FELs is produced by a superconducting accelerator. The electron beam is transported to the FELs via three beam lines (125 MeV and 2 x 250 MeV). Peculiar feature of the proposed complex is a high efficiency of the. FEL oscillators, up to 20 %. This becomes possible due to the use of quasi-continuous electron beam and the use of the time-dependent undulator tapering.

  17. Superconductivity in an electron band just above the Fermi level: possible route to BCS-BEC superconductivity.

    PubMed

    Okazaki, K; Ito, Y; Ota, Y; Kotani, Y; Shimojima, T; Kiss, T; Watanabe, S; Chen, C-T; Niitaka, S; Hanaguri, T; Takagi, H; Chainani, A; Shin, S

    2014-02-28

    Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals and ultra-cold gases, respectively, are connected by the BCS-BEC crossover. Here we investigate the band dispersions in FeTe(0.6)Se(0.4)(Tc = 14.5 K ~ 1.2 meV) in an accessible range below and above the Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission spectroscopy. We uncover an electron band lying just 0.7 meV (~8 K) above EF at the Γ-point, which shows a sharp superconducting coherence peak with gap formation below Tc. The estimated superconducting gap Δ and Fermi energy [Symbol: see text]F indicate composite superconductivity in an iron-based superconductor, consisting of strong-coupling BEC in the electron band and weak-coupling BCS-like superconductivity in the hole band. The study identifies the possible route to BCS-BEC superconductivity.

  18. Electronic heat current rectification in hybrid superconducting devices

    SciTech Connect

    Fornieri, Antonio Giazotto, Francesco; Martínez-Pérez, María José

    2015-05-15

    In this work, we review and expand recent theoretical proposals for the realization of electronic thermal diodes based on tunnel-junctions of normal metal and superconducting thin films. Starting from the basic rectifying properties of a single hybrid tunnel junction, we will show how the rectification efficiency can be largely increased by combining multiple junctions in an asymmetric chain of tunnel-coupled islands. We propose three different designs, analyzing their performance and their potential advantages. Besides being relevant from a fundamental physics point of view, this kind of devices might find important technological application as fundamental building blocks in solid-state thermal nanocircuits and in general-purpose cryogenic electronic applications requiring energy management.

  19. Superconductivity

    DTIC Science & Technology

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  20. Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP)

    SciTech Connect

    Sun, L. Feng, Y. C.; Zhang, W. H.; Zhang, X. Z.; Cao, Y.; Wu, W.; Yang, T. J.; Zhao, B.; Zhao, H. W.; Ma, L. Z.; Xia, J. W.; Lu, W.; Zhao, Y. Y.; Xie, D.

    2014-02-15

    Superconducting ECR ion sources can produce intense highly charged ion beams for the application in heavy ion accelerators. Superconducting Electron Resonance ion source with Advanced Design (SECRAL) is one of the few fully superconducting ECR ion sources that has been successfully built and put into routine operation for years. With enormous efforts and R and D work, promising results have been achieved with the ion source. Heated by the microwave power from a 7 kW/24 GHz gyrotron microwave generator, very intense highly charged gaseous ion beams have been produced, such as 455 eμA Xe{sup 27+}, 236 eμA Xe{sup 30+}, and 64 eμA Xe{sup 35+}. Since heavy metallic ion beams are being more and more attractive and important for many accelerator projects globally, intensive studies have been made to produce highly charged heavy metal ion beams, such as those from bismuth and uranium. Recently, 420 eμA Bi{sup 30+} and 202 eμA U{sup 33+} have been produced with SECRAL source. This paper will present the latest results with SECRAL, and the operation status will be discussed as well. An introduction of recently started SECRAL II project will also be given in the presentation.

  1. Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP)

    NASA Astrophysics Data System (ADS)

    Sun, L.; Lu, W.; Feng, Y. C.; Zhang, W. H.; Zhang, X. Z.; Cao, Y.; Zhao, Y. Y.; Wu, W.; Yang, T. J.; Zhao, B.; Zhao, H. W.; Ma, L. Z.; Xia, J. W.; Xie, D.

    2014-02-01

    Superconducting ECR ion sources can produce intense highly charged ion beams for the application in heavy ion accelerators. Superconducting Electron Resonance ion source with Advanced Design (SECRAL) is one of the few fully superconducting ECR ion sources that has been successfully built and put into routine operation for years. With enormous efforts and R&D work, promising results have been achieved with the ion source. Heated by the microwave power from a 7 kW/24 GHz gyrotron microwave generator, very intense highly charged gaseous ion beams have been produced, such as 455 eμA Xe27+, 236 eμA Xe30+, and 64 eμA Xe35+. Since heavy metallic ion beams are being more and more attractive and important for many accelerator projects globally, intensive studies have been made to produce highly charged heavy metal ion beams, such as those from bismuth and uranium. Recently, 420 eμA Bi30+ and 202 eμA U33+ have been produced with SECRAL source. This paper will present the latest results with SECRAL, and the operation status will be discussed as well. An introduction of recently started SECRAL II project will also be given in the presentation.

  2. Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP).

    PubMed

    Sun, L; Lu, W; Feng, Y C; Zhang, W H; Zhang, X Z; Cao, Y; Zhao, Y Y; Wu, W; Yang, T J; Zhao, B; Zhao, H W; Ma, L Z; Xia, J W; Xie, D

    2014-02-01

    Superconducting ECR ion sources can produce intense highly charged ion beams for the application in heavy ion accelerators. Superconducting Electron Resonance ion source with Advanced Design (SECRAL) is one of the few fully superconducting ECR ion sources that has been successfully built and put into routine operation for years. With enormous efforts and R&D work, promising results have been achieved with the ion source. Heated by the microwave power from a 7 kW/24 GHz gyrotron microwave generator, very intense highly charged gaseous ion beams have been produced, such as 455 eμA Xe(27+), 236 eμA Xe(30+), and 64 eμA Xe(35+). Since heavy metallic ion beams are being more and more attractive and important for many accelerator projects globally, intensive studies have been made to produce highly charged heavy metal ion beams, such as those from bismuth and uranium. Recently, 420 eμA Bi(30+) and 202 eμA U(33+) have been produced with SECRAL source. This paper will present the latest results with SECRAL, and the operation status will be discussed as well. An introduction of recently started SECRAL II project will also be given in the presentation.

  3. Cerenkov Radiator Driven by a Superconducting RF Electron Gun

    SciTech Connect

    Poole, B R; Harris, J R

    2011-03-07

    The Naval Postgraduate School (NPS), Niowave, Inc., and Boeing have recently demonstrated operation of the first superconducting RF electron gun based on a quarter wave resonator structure. In preliminary tests, this gun has produced 10 ps long bunches with charge in excess of 78 pC, and with beam energy up to 396 keV. Initial testing occurred at Niowave's Lansing, MI facility, but the gun and diagnostic beam line are planned for installation in California in the near future. The design of the diagnostic beam line is conducive to the addition of a Cerenkov radiator without interfering with other beam line operations. Design and simulations of a Cerenkov radiator, consisting of a dielectric lined waveguide will be presented. The dispersion relation for the structure is determined and the beam interaction is studied using numerical simulations. The characteristics of the microwave radiation produced in both the short and long bunch regimes will be presented.

  4. Development of an alternating integrator for magnetic measurements for experimental advanced superconducting tokamak

    SciTech Connect

    Liu, D. M. Zhao, W. Z.; He, Y. G.; Chen, B.; Wan, B. N.; Shen, B.; Huang, J.; Liu, H. Q.

    2014-11-15

    A high-performance integrator is one of the key electronic devices for reliably controlling plasma in the experimental advanced superconducting tokamak for long pulse operation. We once designed an integrator system of real-time drift compensation, which has a low integration drift. However, it is not feasible for really continuous operations due to capacitive leakage error and nonlinearity error. To solve the above-mentioned problems, this paper presents a new alternating integrator. In the new integrator, the integrator system of real-time drift compensation is adopted as one integral cell while two such integral cells work alternately. To achieve the alternate function, a Field Programmable Gate Array built in the digitizer is utilized. The performance test shows that the developed integrator with the integration time constant of 20 ms has a low integration drift (<15 mV) for 1000 s.

  5. Superconductivity

    NASA Astrophysics Data System (ADS)

    Yeo, Yung K.

    Many potential high-temperature superconductivity (HTS) military applications have been demonstrated by low-temperature superconductivity systems; they encompass high efficiency electric drives for naval vessels, airborne electric generators, energy storage systems for directed-energy weapons, electromechanical launchers, magnetic and electromagnetic shields, and cavity resonators for microwave and mm-wave generation. Further HST applications in militarily relevant fields include EM sensors, IR focal plane arrays, SQUIDs, magnetic gradiometers, high-power sonar sources, and superconducting antennas and inertial navigation systems. The development of SQUID sensors will furnish novel magnetic anomaly detection methods for ASW.

  6. First Beam and High-Gradient Cryomodule Commissioning Results of the Advanced Superconducting Test Accelerator at Fermilab

    SciTech Connect

    Crawford, Darren; et al.

    2015-06-01

    The advanced superconducting test accelerator at Fermilab has accelerated electrons to 20 MeV and, separately, the International Linear Collider (ILC) style 8-cavity cryomodule has achieved the ILC performance milestone of 31.5 MV/m per cavity. When fully completed, the accelerator will consist of a photoinjector, one ILC-type cryomodule, multiple accelerator R&D beamlines, and a downstream beamline to inject 300 MeV electrons into the Integrable Optics Test Accelerator (IOTA). We report on the results of first beam, the achievement of our cryomodule to ILC gradient specifications, and near-term future plans for the facility.

  7. Advanced uncooled infrared system electronics

    NASA Astrophysics Data System (ADS)

    Neal, Henry W.

    1998-07-01

    Over the past two decades, Raytheon Systems Company (RSC), formerly Texas Instruments Defense Systems & Electronics Group, developed a robust family of products based on a low- cost, hybrid ferroelectric (FE) uncooled focal-plane array (FPA) aimed at meeting the needs for thermal imaging products across both military and commercial markets. Over the years, RSC supplied uncooled infrared (IR) sensors for applications such as in combat vehicles, man-portable weaponry, personnel helmets, and installation security. Also, various commercial IR systems for use in automobiles, boats, law enforcement, hand-held applications, building/site security, and fire fighting have been developed. These products resulted in a high degree of success where cooled IR platforms are too bulky and costly, and other uncooled implementations are less reliable or lack significant cost advantage. Proof of this great success is found in the large price reductions, the unprecedented monthly production rates, and the wide diversity of products and customers realized in recent years. The ever- changing needs of these existing and potential customers continue to fuel the advancement of both the primary technologies and the production capabilities of uncooled IR systems at RSC. This paper will describe a development project intended to further advance the system electronics capabilities of future uncooled IR products.

  8. Superconducting Cavity Design for Short-Pulse X-Rays at the Advanced Photon Source

    SciTech Connect

    G.J. Waldschmidt, R. Nassiri, G. Cheng, R.A. Rimmer, H. Wang

    2011-03-01

    Superconducting cavities have been analyzed for the short-pulse x-ray (SPX) project at the Advanced Photon Source (APS). Due to the strong damping requirements in the APS storage ring, single-cell superconducting cavities have been designed. The geometry has been optimized for lower-order and higher-order mode damping, reduced peak surface magnetic fields, and compact size. The integration of the cavity assembly, with dampers and waveguide input coupler, into a cryomodule will be discussed.

  9. Advances in the development of piezoelectric quartz-crystal oscillators, hydrogen masers, and superconducting frequency standards

    NASA Technical Reports Server (NTRS)

    Suter, Joseph J.

    1988-01-01

    This paper describes recent research advances made in the development of radiation-hardened piezoelectric quartz oscillators, hydrogen masers, and superconducting oscillators, with emphasis placed on the principles involved in the operation of these oscillators and the factors affecting the operation. Particular attention is given to the radiation-susceptibility studies of quartz-crystal resonators, the hydrogen-maser relaxation process and noise sources, and low-phase-noise superconducting oscillators. Diagrams of these devices and performance graphs are included.

  10. Superconductivity on the border of itinerant-electron ferromagnetism in UGe2

    PubMed

    Saxena; Agarwal; Ahilan; Grosche; Haselwimmer; Steiner; Pugh; Walker; Julian; Monthoux; Lonzarich; Huxley; Sheikin; Braithwaite; Flouquet

    2000-08-10

    The absence of simple examples of superconductivity adjoining itinerant-electron ferromagnetism in the phase diagram has for many years cast doubt on the validity of conventional models of magnetically mediated superconductivity. On closer examination, however, very few systems have been studied in the extreme conditions of purity, proximity to the ferromagnetic state and very low temperatures required to test the theory definitively. Here we report the observation of superconductivity on the border of ferromagnetism in a pure system, UGe2, which is known to be qualitatively similar to the classic d-electron ferromagnets. The superconductivity that we observe below 1 K, in a limited pressure range on the border of ferromagnetism, seems to arise from the same electrons that produce band magnetism. In this case, superconductivity is most naturally understood in terms of magnetic as opposed to lattice interactions, and by a spin-triplet rather than the spin-singlet pairing normally associated with nearly antiferromagnetic metals.

  11. Ferromagnetic-Insulator-Based Superconducting Junctions as Sensitive Electron Thermometers

    NASA Astrophysics Data System (ADS)

    Giazotto, F.; Solinas, P.; Braggio, A.; Bergeret, F. S.

    2015-10-01

    We present an exhaustive theoretical analysis of charge and thermoelectric transport in a normal-metal-ferromagnetic-insulator-superconductor junction and explore the possibility of its use as a sensitive thermometer. We investigate the transfer functions and the intrinsic noise performance for different measurement configurations. A common feature of all configurations is that the best temperature-noise performance is obtained in the nonlinear temperature regime for a structure based on an Europium chalcogenide ferromagnetic insulator in contact with a superconducting Al film structure. For an open-circuit configuration, although the maximal intrinsic temperature sensitivity can achieve 10 nK Hz-1 /2 , a realistic amplifying chain will reduce the sensitivity up to 10 μ K Hz-1 /2 . To overcome this limitation, we propose a measurement scheme in a closed-circuit configuration based on state-of-the-art superconducting-quantum-interference-device detection technology in an inductive setup. In such a case, we show that temperature-noise can be as low as 35 nK Hz-1 /2 . We also discuss a temperature-to-frequency converter where the obtained thermovoltage developed over a Josephson junction operated in the dissipative regime is converted into a high-frequency signal. We predict that the structure can generate frequencies up to approximately 120 GHz and transfer functions up to 200 GHz /K at around 1 K. If operated as an electron thermometer, the device may provide temperature-noise lower than 35 nK Hz-1 /2 thereby being potentially attractive for radiation-sensing applications.

  12. Electronic phase separation transition as the origin of the superconductivity and pseudogap phase of cuprates

    NASA Astrophysics Data System (ADS)

    de Mello, E. V. L.; Kasal, R. B.; Passos, C. A. C.

    2009-06-01

    To deal with the physics of cuprate superconductivity we propose an electronic phase separation transition that segregates the holes into high and low density domains. The calculated grain boundary potential favors the development of intragrain superconducting amplitudes. The zero resistivity transition arises only when the intergrain Josephson coupling EJ is of the order of the thermal energy and phase locking takes place among the superconducting grains. We show that this approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy data.

  13. Electronic phase separation transition as the origin of the superconductivity and pseudogap phase of cuprates.

    PubMed

    de Mello, E V L; Kasal, R B; Passos, C A C

    2009-06-10

    To deal with the physics of cuprate superconductivity we propose an electronic phase separation transition that segregates the holes into high and low density domains. The calculated grain boundary potential favors the development of intragrain superconducting amplitudes. The zero resistivity transition arises only when the intergrain Josephson coupling E(J) is of the order of the thermal energy and phase locking takes place among the superconducting grains. We show that this approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy data.

  14. Electron-Phonon Coupling and its implication for the superconducting topological insulators

    PubMed Central

    Zhang, Xiao-Long; Liu, Wu-Ming

    2015-01-01

    The recent observation of superconductivity in doped topological insulators has sparked a flurry of interest due to the prospect of realizing the long-sought topological superconductors. Yet the understanding of underlying pairing mechanism in these systems is far from complete. Here we investigate this problem by providing robust first-principles calculations of the role of electron-phonon coupling for the superconducting pairing in the prime candidate CuxBi2Se3. Our results show that electron-phonon scattering process in this system is dominated by zone center and boundary optical modes, with coexistence of phonon stiffening and softening. While the calculated electron-phonon coupling constant λ suggests that Tc from electron-phonon coupling is 2 orders smaller than the ones reported on bulk inhomogeneous samples, suggesting that superconductivity may not come from pure electron-phonon coupling. We discuss the possible enhancement of superconducting transition temperature by local inhomogeneity introduced by doping. PMID:25753813

  15. Advances in nonlethal electronic weaponry

    NASA Astrophysics Data System (ADS)

    McNulty, James F.

    1998-12-01

    Non-lethal electronic weapons in the form of tasers (a stand-off incapacitation device with a range of about 15 feet) and stun guns (which are not a gun, but a close contact stun device) have been used by law enforcement for over 18 years. The taser has dominated this market, since it does not require the close physical contact (with the resultant injuries) that the stun gun requires. Tasers are effective against even determined assailants where OC or pepper sprays consistently fail. The taser also does not have the close range lethality of low impact munitions. These electronic non-lethal weapons have saved the lives of thousands of suspects and have prevented the injury of thousands of law enforcement officers. Recent advances in laser sight technology have permitted the development of a patented dual laser sight that not only increased accuracy, but have made these weapons even more intimidating, increasing surrender rates. Now increased ranges are feasible and r & d on non-lethal military weapons to replace the anti-personnel landmine has resulted in new, unmanned, non-lethal taser weapons for law enforcement corrections and border patrol perimeter control use.

  16. Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.

    PubMed

    Liu, Defa; Zhang, Wenhao; Mou, Daixiang; He, Junfeng; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Zhao, Lin; He, Shaolong; Peng, Yingying; Liu, Xu; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Hu, Jiangping; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2012-07-03

    The recent discovery of high-temperature superconductivity in iron-based compounds has attracted much attention. How to further increase the superconducting transition temperature (T(c)) and how to understand the superconductivity mechanism are two prominent issues facing the current study of iron-based superconductors. The latest report of high-T(c) superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-like pockets near the zone corner without indication of any Fermi surface around the zone centre. Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. The temperature dependence of the superconducting gap gives a transition temperature T(c)~ 55 K. These results have established a clear case that such a simple electronic structure is compatible with high-T(c) superconductivity in iron-based superconductors.

  17. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride.

    PubMed

    Pan, Xing-Chen; Chen, Xuliang; Liu, Huimei; Feng, Yanqing; Wei, Zhongxia; Zhou, Yonghui; Chi, Zhenhua; Pi, Li; Yen, Fei; Song, Fengqi; Wan, Xiangang; Yang, Zhaorong; Wang, Baigeng; Wang, Guanghou; Zhang, Yuheng

    2015-07-23

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 T. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides.

  18. A Novel superconducting toroidal field magnet concept using advanced materials

    NASA Astrophysics Data System (ADS)

    Schwartz, J.

    1992-03-01

    The plasma physics database indicates that two distinct approaches to tokamak design may lead to commercial fusion reactors: low Aspect ratio, high plasma current, relatively low magnetic field devices, and high Aspect ratio, high field devices. The former requires significant enhancements in plasma performance, while the latter depends primarily upon technology development. The key technology for the commercialization of the high-field approach is large, high magnetic field superconducting magnets. In this paper, the physics motivation for the high field approach and key superconducting magnet (SCM) development issues are reviewed. Improved SCM performance may be obtained from improved materials and/or improved engineering. Superconducting materials ranging from NbTi to high- T c oxides are reviewed, demonstrating the broad range of potential superconducting materials. Structural material options are discussed, including cryogenic steel alloys and fiber-reinforced composite materials. Again, the breadth of options is highlighted. The potential for improved magnet engineering is quantified in terms of the Virial Theorem Limit, and two examples of approaches to highly optimized magnet configurations are discussed. The force-reduced concept, which is a finite application of the force-free solutions to Ampere's Law, appear promising for large SCMs but may be limited by the electromagnetics of a fusion plasma. The Solid Superconducting Cylinder (SSC) concept is proposed. This concept combines the unique properties of high- T c superconductors within a low- T c SCM to obtain (1) significant reductions in the structural material volume, (2) a decoupling of the tri-axial (compressive and tensile) stress state, and (3) a demountable TF magnet system. The advantages of this approach are quantified in terms of a 24 T commercial reactor TF magnet system. Significant reductions in the mechanical stress and the TF radial build are demonstrated.

  19. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Li, Y. L.; Xu, G. S.; Wan, B. N.; Lan, H.; Liu, Y. L.; Wei, J.; Zhang, W.; Hu, G. H.; Wang, H. Q.; Duan, Y. M.; Zhao, J. L.; Wang, L.; Liu, S. C.; Ye, Y.; Li, J.; Lin, X.; Li, X. L.; Tritz, K.; Zhu, Y. B.

    2015-12-15

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  20. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Xu, G. S.; Tritz, K.; Zhu, Y. B.; Wan, B. N.; Lan, H.; Liu, Y. L.; Wei, J.; Zhang, W.; Hu, G. H.; Wang, H. Q.; Duan, Y. M.; Zhao, J. L.; Wang, L.; Liu, S. C.; Ye, Y.; Li, J.; Lin, X.; Li, X. L.

    2015-12-01

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  1. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak.

    PubMed

    Li, Y L; Xu, G S; Tritz, K; Zhu, Y B; Wan, B N; Lan, H; Liu, Y L; Wei, J; Zhang, W; Hu, G H; Wang, H Q; Duan, Y M; Zhao, J L; Wang, L; Liu, S C; Ye, Y; Li, J; Lin, X; Li, X L

    2015-12-01

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  2. Drift theory of strong diamagnetism and superconductivity of electron plasmas in conductors

    NASA Astrophysics Data System (ADS)

    Abramov, O. V.; Gradov, O. M.; Kyrie, A. Yu

    1993-11-01

    A degenerated electron plasma in the field of a superlattice is shown to possess strong diamagnetism due to the quantum gradient drift current, and superconductivity due to the quantum "centrifugal" drift current.

  3. Electron-phonon interaction and pairing mechanism in superconducting Ca-intercalated bilayer graphene

    PubMed Central

    Margine, E. R.; Lambert, Henry; Giustino, Feliciano

    2016-01-01

    Using the ab initio anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We find that C6CaC6 can support phonon-mediated superconductivity with a critical temperature Tc = 6.8–8.1 K, in good agreement with experimental data. Our calculations indicate that the low-energy Caxy vibrations are critical to the pairing, and that it should be possible to resolve two distinct superconducting gaps on the electron and hole Fermi surface pockets. PMID:26892805

  4. Superconductivity:

    NASA Astrophysics Data System (ADS)

    Sacchetti, N.

    In this paper a short historical account of the discovery of superconductivity and of its gradual development is given. The physical interpretation of its various aspects took about forty years (from 1911 to 1957) to reach a successful description of this phenomenon in terms of a microscopic theory At the very end it seemed that more or less everything could be reasonably interpreted even if modifications and refinements of the original theory were necessary. In 1986 the situation changed abruptly when a cautious but revolutionary paper appeared showing that superconductivity was found in certain ceramic oxides at temperatures above those up to then known. A rush of frantic experimental activity started world-wide and in less than one year it was shown that superconductivity is a much more widespread phenomenon than deemed before and can be found at temperatures well above the liquid air boiling point. The complexity and the number of the substances (mainly ceramic oxides) involved call for a sort of modern alchemy if compounds with the best superconducting properties are to be manufactured. We don't use the word alchemy in a deprecatory sense but just to emphasise that till now nobody can say why these compounds are what they are: superconductors.

  5. High-temperature superconductivity: Electron mirages in an iron salt

    NASA Astrophysics Data System (ADS)

    Zaanen, Jan

    2014-11-01

    The detection of unusual 'mirage' energy bands in photoemission spectra of single-atom layers of iron selenide reveals the probable cause of high-temperature superconductivity in these artificial structures. See Letter p.245

  6. Coherence and Chaos Phenomena in Josephson Oscillators for Superconducting Electronics.

    DTIC Science & Technology

    1989-01-25

    represents dissipation due j+(a+/b)+ b--i(a-) to the surface resistance of the superconducting films , y is the uniform bias current normalized to the...represents series loss due series of time-dependent Fourier spatial compo- to surface resistance of the superconducting films , nents. Tis approach provides...case is that in which there is no ing films , y is the spatially uniform bias current normal- external magnetic field applied to the junction. In this

  7. Electrostatic electron-doping yields superconductivity in LaOBiS2

    NASA Astrophysics Data System (ADS)

    Uesugi, Eri; Nishiyama, Saki; Goto, Hidenori; Ota, Hiromi; Kubozono, Yoshihiro

    2016-12-01

    Electrostatic carrier-doping is attracting serious attention as a meaningful technique for producing interesting electronic states in two-dimensional (2D) layered materials. Ionic-liquid gating can provide the critical carrier density required to induce the metal-insulator transition and superconductivity. However, the physical properties of only a few materials have been controlled by the electrostatic carrier-doping during the past decade. Here, we report an observation of superconductivity in a 2D layered material, LaOBiS2, achieved by the electrostatic electron-doping. The electron doping of LaOBiS2 induced metallic conductivity in the normally insulating LaOBiS2, ultimately led to superconductivity. The superconducting transition temperature, Tc, was 3.6 K, higher than the 2.7 K seen in LaO1-xFxBiS2 with an electron-doped BiS2 layer. A rapid drop in resistance (R) was observed at low temperature, which disappeared with the application of high magnetic fields, implying a superconducting state. This study reveals that electron-doping is an important technique for inducing superconductivity in 2D layered BiS2 materials.

  8. The circuit of polychromator for Experimental Advanced Superconducting Tokamak edge Thomson scattering diagnostic

    SciTech Connect

    Zang, Qing; Zhao, Junyu; Chen, Hui; Li, Fengjuan; Hsieh, C. L.

    2013-09-15

    The detector circuit is the core component of filter polychromator which is used for scattering light analysis in Thomson scattering diagnostic, and is responsible for the precision and stability of a system. High signal-to-noise and stability are primary requirements for the diagnostic. Recently, an upgraded detector circuit for weak light detecting in Experimental Advanced Superconducting Tokamak (EAST) edge Thomson scattering system has been designed, which can be used for the measurement of large electron temperature (T{sub e}) gradient and low electron density (n{sub e}). In this new circuit, a thermoelectric-cooled avalanche photodiode with the aid circuit is involved for increasing stability and enhancing signal-to-noise ratio (SNR), especially the circuit will never be influenced by ambient temperature. These features are expected to improve the accuracy of EAST Thomson diagnostic dramatically. Related mechanical construction of the circuit is redesigned as well for heat-sinking and installation. All parameters are optimized, and SNR is dramatically improved. The number of minimum detectable photons is only 10.

  9. Advancement of highly charged ion beam production by superconducting ECR ion source SECRAL (invited)

    SciTech Connect

    Sun, L. Lu, W.; Zhang, W. H.; Feng, Y. C.; Qian, C.; Ma, H. Y.; Zhang, X. Z.; Zhao, H. W.; Guo, J. W.; Yang, Y.; Fang, X.

    2016-02-15

    At Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS), the superconducting Electron Cyclotron Resonance (ECR) ion source SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) has been put into operation for about 10 years now. It has been the main working horse to deliver intense highly charged heavy ion beams for the accelerators. Since its first plasma at 18 GHz, R&D work towards more intense highly charged ion beam production as well as the beam quality investigation has never been stopped. When SECRAL was upgraded to its typical operation frequency 24 GHz, it had already showed its promising capacity of very intense highly charged ion beam production. And it has also provided the strong experimental support for the so called scaling laws of microwave frequency effect. However, compared to the microwave power heating efficiency at 18 GHz, 24 GHz microwave heating does not show the ω{sup 2} scale at the same power level, which indicates that microwave power coupling at gyrotron frequency needs better understanding. In this paper, after a review of the operation status of SECRAL with regard to the beam availability and stability, the recent study of the extracted ion beam transverse coupling issues will be discussed, and the test results of the both TE{sub 01} and HE{sub 11} modes will be presented. A general comparison of the performance working with the two injection modes will be given, and a preliminary analysis will be introduced. The latest results of the production of very intense highly charged ion beams, such as 1.42 emA Ar{sup 12+}, 0.92 emA Xe{sup 27+}, and so on, will be presented.

  10. Advancement of highly charged ion beam production by superconducting ECR ion source SECRAL (invited)

    NASA Astrophysics Data System (ADS)

    Sun, L.; Guo, J. W.; Lu, W.; Zhang, W. H.; Feng, Y. C.; Yang, Y.; Qian, C.; Fang, X.; Ma, H. Y.; Zhang, X. Z.; Zhao, H. W.

    2016-02-01

    At Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS), the superconducting Electron Cyclotron Resonance (ECR) ion source SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) has been put into operation for about 10 years now. It has been the main working horse to deliver intense highly charged heavy ion beams for the accelerators. Since its first plasma at 18 GHz, R&D work towards more intense highly charged ion beam production as well as the beam quality investigation has never been stopped. When SECRAL was upgraded to its typical operation frequency 24 GHz, it had already showed its promising capacity of very intense highly charged ion beam production. And it has also provided the strong experimental support for the so called scaling laws of microwave frequency effect. However, compared to the microwave power heating efficiency at 18 GHz, 24 GHz microwave heating does not show the ω2 scale at the same power level, which indicates that microwave power coupling at gyrotron frequency needs better understanding. In this paper, after a review of the operation status of SECRAL with regard to the beam availability and stability, the recent study of the extracted ion beam transverse coupling issues will be discussed, and the test results of the both TE01 and HE11 modes will be presented. A general comparison of the performance working with the two injection modes will be given, and a preliminary analysis will be introduced. The latest results of the production of very intense highly charged ion beams, such as 1.42 emA Ar12+, 0.92 emA Xe27+, and so on, will be presented.

  11. High-temperature superconducting thin-film-based electronic devices

    SciTech Connect

    Wu, X.D; Finokoglu, A.; Hawley, M.; Jia, Q.; Mitchell, T.; Mueller, F.; Reagor, D.; Tesmer, J.

    1996-09-01

    This the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project involved optimization of processing of Y123 and Tl-2212 thin films deposited on novel substrates for advanced electronic devices. The Y123 films are the basis for development of Josephson Junctions to be utilized in magnetic sensors. Microwave cavities based on the Tl-2212 films are the basis for subsequent applications as communication antennas and transmitters in satellites.

  12. Electron-phonon interaction and superconductivity in BaIr2P2

    NASA Astrophysics Data System (ADS)

    Billington, D.

    2016-10-01

    Detailed calculations of the electronic structure, phonons and electron-phonon coupling of the superconducting compound BaIr2P2 were performed from first-principles. The electronic structure showed excellent agreement with the available experimental data. The total electron-phonon coupling constant was {λ\\text{ep}}=0.52 and the logarithmically averaged phonon frequency was \\hbar {ω\\text{log}}/{{k}\\text{B}}=168 K. From the Allen-Dynes formula, with {μ\\ast}=0.11 , the superconducting critical temperature was estimated to be {{T}\\text{c}}=2.05 K, which is in excellent agreement with the experiment. These results indicate that the electron-phonon coupling is of moderate strength and is easily capable of supporting the observed superconductivity.

  13. Nb3Sn superconducting magnets for electron cyclotron resonance ion sources

    SciTech Connect

    Ferracin, P.; Caspi, S.; Felice, H.; Leitner, D.; Lyneis, C. M.; Prestemon, S.; Sabbi, G. L.; Todd, D. S.

    2009-05-04

    Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb{sub 3}Sn superconducting technology for several years. At the moment, Nb{sub 3}Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb{sub 3}Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb{sub 3}Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb{sub 3}Sn- , particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell

  14. Nb{sub 3}Sn superconducting magnets for electron cyclotron resonance ion sources

    SciTech Connect

    Ferracin, P.; Caspi, S.; Felice, H.; Leitner, D.; Lyneis, C. M.; Prestemon, S.; Sabbi, G. L.; Todd, D. S.

    2010-02-15

    Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb{sub 3}Sn superconducting technology for several years. At the moment, Nb{sub 3}Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb{sub 3}Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb{sub 3}Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb{sub 3}Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell

  15. Nb3Sn superconducting magnets for electron cyclotron resonance ion sources.

    PubMed

    Ferracin, P; Caspi, S; Felice, H; Leitner, D; Lyneis, C M; Prestemon, S; Sabbi, G L; Todd, D S

    2010-02-01

    Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb(3)Sn superconducting technology for several years. At the moment, Nb(3)Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb(3)Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb(3)Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb(3)Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell pretensioned with water

  16. General Conditions for Proximity-Induced Odd-Frequency Superconductivity in Two-Dimensional Electronic Systems.

    PubMed

    Triola, Christopher; Badiane, Driss M; Balatsky, Alexander V; Rossi, E

    2016-06-24

    We obtain the general conditions for the emergence of odd-frequency superconducting pairing in a two-dimensional (2D) electronic system proximity coupled to a superconductor, making minimal assumptions about both the 2D system and the superconductor. Using our general results we show that a simple heterostructure formed by a monolayer of a group VI transition metal dichalcogenide, such as molybdenum disulfide, and an s-wave superconductor with Rashba spin-orbit coupling exhibits odd-frequency superconducting pairing. Our results allow the identification of a new class of systems among van der Waals heterostructures in which odd-frequency superconductivity should be present.

  17. The integration of liquid cryogen cooling and cryocoolers with superconducting electronic systems

    NASA Astrophysics Data System (ADS)

    Green, Michael A.

    2003-12-01

    The need for cryogenic cooling has been a critical issue that has kept superconducting electronic devices from reaching the market place. Even though the performance of many of the superconducting circuits is superior to silicon electronics, the requirement for cryogenic cooling has put the superconducting devices at a serious disadvantage. This paper discusses the process of refrigerating superconducting devices with cryogenic liquids and small cryocoolers. Three types of cryocoolers are compared for vibration, efficiency and reliability. The connection of a cryocooler to the load is discussed. A comparison of using flexible copper straps to carry the heat load and using heat pipe is shown. The type of instrumentation needed for monitoring and controlling the cooling is discussed.

  18. Performance of current measurement system in poloidal field power supply for Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Liu, D. M.; Li, J.; Wan, B. N.; Lu, Z.; Wang, L. S.; Jiang, L.; Lu, C. H.; Huang, J.

    2016-11-01

    As one of the core subsystems of the Experimental Advanced Superconducting Tokamak (EAST), the poloidal field power system supplies energy to EAST's superconducting coils. To measure the converter current in the poloidal field power system, a current measurement system has been designed. The proposed measurement system is composed of a Rogowski coil and a newly designed integrator. The results of the resistor-inductor-capacitor discharge test and the converter equal current test show that the current measurement system provides good reliability and stability, and the maximum error of the proposed system is less than 1%.

  19. Development and operating experience of a short-period superconducting undulator at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Ivanyushenkov, Y.; Harkay, K.; Abliz, M.; Boon, L.; Borland, M.; Capatina, D.; Collins, J.; Decker, G.; Dejus, R.; Dooling, J.; Doose, C.; Emery, L.; Fuerst, J.; Gagliano, J.; Hasse, Q.; Jaski, M.; Kasa, M.; Kim, S. H.; Kustom, R.; Lang, J. C.; Liu, J.; Moog, E.; Robinson, D.; Sajaev, V.; Schroeder, K.; Sereno, N.; Shiroyanagi, Y.; Skiadopoulos, D.; Smith, M.; Sun, X.; Trakhtenberg, E.; Vasserman, I.; Vella, A.; Xiao, A.; Xu, J.; Zholents, A.; Gluskin, E.; Lev, V.; Mezentsev, N.; Syrovatin, V.; Tsukanov, V.; Makarov, A.; Pfotenhauer, J.; Potratz, D.

    2015-04-01

    A decade-long effort at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL) on development of superconducting undulators culminated in December 2012 with the installation of the first superconducting undulator "SCU0" into Sector 6 of the APS storage ring. The device was commissioned in January 2013 and has been in user operation since. This paper presents the magnetic and cryogenic design of the SCU0 together with the results of stand-alone cold tests. The initial commissioning and characterization of SCU0 as well as its operating experience in the APS storage ring are described.

  20. Fabrication and assembly of a superconducting undulator for the advanced photon source

    SciTech Connect

    Hasse, Quentin; Fuerst, J. D.; Ivanyushenkov, Y.; Doose, C.; Kasa, M.; Shiroyanagi, Y.; Trakhtenberg, E. M.; Skiadopoulos, D.

    2014-01-29

    A prototype superconducting undulator magnet (SCU0) has been built at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL) and has successfully completed both cryogenic performance and magnetic measurement test programs. The SCU0 closed loop, zero-boil-off cryogenic system incorporates high temperature superconducting (HTS) current leads, cryocoolers, a LHe reservoir supplying dual magnetic cores, and an integrated cooled beam chamber. This system presented numerous challenges in the design, fabrication, and assembly of the device. Aspects of this R and D relating to both the cryogenic and overall assembly of the device are presented here. The SCU0 magnet has been installed in the APS storage ring.

  1. Performance of current measurement system in poloidal field power supply for Experimental Advanced Superconducting Tokamak.

    PubMed

    Liu, D M; Li, J; Wan, B N; Lu, Z; Wang, L S; Jiang, L; Lu, C H; Huang, J

    2016-11-01

    As one of the core subsystems of the Experimental Advanced Superconducting Tokamak (EAST), the poloidal field power system supplies energy to EAST's superconducting coils. To measure the converter current in the poloidal field power system, a current measurement system has been designed. The proposed measurement system is composed of a Rogowski coil and a newly designed integrator. The results of the resistor-inductor-capacitor discharge test and the converter equal current test show that the current measurement system provides good reliability and stability, and the maximum error of the proposed system is less than 1%.

  2. Superconductivity, cohesive energy density, and electron-atom ratio in metals

    NASA Technical Reports Server (NTRS)

    England, C.; Lawson, D. D.; Hrubes, J. D.

    1981-01-01

    It is shown that superconductivity above 8 K occurs in alloys and metallic compounds within relatively narrow regions of cohesive energy density with a sharp peak which includes Nb3Ge, SiV3, Nb3Ga, and NbN. When cross-correlated with the electron-atom ratio, high-temperature superconductivity can be observed in only a few regions. This suggests a search for superconductors with high-transition temperatures and critical fields within these regions.

  3. Localized 5f electrons in superconducting PuCoIn₅: consequences for superconductivity in PuCoGa₅.

    PubMed

    Bauer, E D; Altarawneh, M M; Tobash, P H; Gofryk, K; Ayala-Valenzuela, O E; Mitchell, J N; McDonald, R D; Mielke, C H; Ronning, F; Griveau, J-C; Colineau, E; Eloirdi, R; Caciuffo, R; Scott, B L; Janka, O; Kauzlarich, S M; Thompson, J D

    2012-02-08

    The physical properties of the first In analog of the PuMGa(5) (M = Co, Rh) family of superconductors, PuCoIn(5), are reported. With its unit cell volume being 28% larger than that of PuCoGa(5), the characteristic spin-fluctuation energy scale of PuCoIn(5) is three to four times smaller than that of PuCoGa(5), which suggests that the Pu 5f electrons are in a more localized state relative to PuCoGa(5). This raises the possibility that the high superconducting transition temperature T(c) = 18.5 K of PuCoGa(5) stems from the proximity to a valence instability, while the superconductivity at T(c) = 2.5 K of PuCoIn(5) is mediated by antiferromagnetic spin fluctuations associated with a quantum critical point.

  4. A hidden pseudogap under the 'dome' of superconductivity in electron-doped high-temperature superconductors.

    PubMed

    Alff, L; Krockenberger, Y; Welter, B; Schonecke, M; Gross, R; Manske, D; Naito, M

    2003-04-17

    The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.

  5. Momentum of superconducting electrons and the explanation of the Meissner effect

    NASA Astrophysics Data System (ADS)

    Hirsch, J. E.

    2017-01-01

    Momentum and energy conservation are fundamental tenets of physics, which valid physical theories have to satisfy. In the reversible transformation between superconducting and normal phases in the presence of a magnetic field, the mechanical momentum of the supercurrent has to be transferred to the body as a whole and vice versa, the kinetic energy of the supercurrent stays in the electronic degrees of freedom, and no energy is dissipated nor entropy is generated in the process. We argue on general grounds that to explain these processes it is necessary that the electromagnetic field mediates the transfer of momentum between electrons and the body as a whole, and this requires that when the phase boundary between normal and superconducting phases is displaced, a flow and counterflow of charge occurs in a direction perpendicular to the phase boundary. This flow and counterflow does not occur according to the conventional BCS-London theory of superconductivity, therefore we argue that within BCS-London theory the Meissner transition is a "forbidden transition." Furthermore, to explain the phase transformation in a way that is consistent with the experimental observations, requires that (i) the wave function and charge distribution of superconducting electrons near the phase boundary extend into the normal phase, and (ii) that the charge carriers in the normal state have holelike character. The conventional theory of superconductivity does not have these physical elements, the theory of hole superconductivity does.

  6. Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities

    SciTech Connect

    Alicia Hofler; Jean Delayen

    2005-05-01

    Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations.

  7. Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

    SciTech Connect

    Feng, L. W.; Lin, L.; Huang, S. L.; Quan, S. W.; Hao, J. K.; Zhu, F.; Wang, F.; Liu, K. X.; Jiang, T.; Zhu, P. F.; Fu, F.; Wang, R.; Zhao, L.; Xiang, D.

    2015-11-30

    We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

  8. Advanced Concepts for Electron-Ion Collider

    SciTech Connect

    Yaroslav Derbenev

    2002-08-01

    A superconducting energy recovery linac (ERL) of 5 to 10 GeV was proposed earlier as an alternative to electron storage rings to deliver polarized electron beam for electron-ion collider (EIC). To enhance the utilization efficiency of electron beam from a polarized source, it is proposed to complement the ERL by circulator ring (CR) wherein the injected electrons undergo up to 100 revolutions colliding with the ion beam. In this way, electron injector and linac operate in pulsed current (beam energy recovery) regime of a relatively low average current, while the polarization is still easily delivered and preserved. To make it also easier delivering and manipulating the proton and light ion polarization, twisted (figure 8) synchrotrons are proposed for heavy particle booster and collider ring. Same type of beam orbit can be used then for electron circulator. Electron cooling (EC) of the ion beam is considered an inevitable component of high luminosity EIC (1033/s. cm2 or above). It is recognized that EC also gives a possibility to obtain very short ion bunches, that allows much stronger final focusing. At the same time, short bunches make feasible the crab crossing (and traveling focus for ion beam) at collision points, hence, allow maximizing the collision rate. As a result, one can anticipate the luminosity increase by one or two orders of magnitude.

  9. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak

    NASA Astrophysics Data System (ADS)

    Seo, Seong-Heon; Park, Jinhyung; Wi, H. M.; Lee, W. R.; Kim, H. S.; Lee, T. G.; Kim, Y. S.; Kang, Jin-Seob; Bog, M. G.; Yokota, Y.; Mase, A.

    2013-08-01

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6-54 GHz), V band (48-72 GHz), and W band (72-108 GHz) to measure the density up to 7 × 1019 m-3 when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

  10. Upgrades of the high resolution imaging x-ray crystal spectrometers on experimental advanced superconducting tokamak

    SciTech Connect

    Lu, B.; Wang, F.; Fu, J.; Li, Y.; Wan, B.; Shi, Y.; Bitter, M.; Hill, K. W.; Lee, S. G.

    2012-10-15

    Two imaging x-ray crystal spectrometers, the so-called 'poloidal' and 'tangential' spectrometers, were recently implemented on experimental advanced superconducting tokamak (EAST) to provide spatially and temporally resolved impurity ion temperature (T{sub i}), electron temperature (T{sub e}) and rotation velocity profiles. They are derived from Doppler width of W line for Ti, the intensity ratio of Li-like satellites to W line for Te, and Doppler shift of W line for rotation. Each spectrometer originally consisted of a spherically curved crystal and a two-dimensional multi-wire proportional counter (MWPC) detector. Both spectrometers have now been upgraded. The layout of the tangential spectrometer was modified, since it had to be moved to a different port, and the spectrometer was equipped with two high count rate Pilatus detectors (Model 100 K) to overcome the count rate limitation of the MWPC and to improve its time resolution. The poloidal spectrometer was equipped with two spherically bent crystals to record the spectra of He-like and H-like argon simultaneously and side by side on the original MWPC. These upgrades are described, and new results from the latest EAST experimental campaign are presented.

  11. Edge-coherent-mode nature of the small edge localized modes in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, H. Q.; Xu, G. S.; Guo, H. Y.; Wan, B. N.; Wang, L.; Chen, R.; Ding, S. Y.; Yan, N.; Gong, X. Z.; Liu, S. C.; Shao, L. M.; Chen, L.; Zhang, W.; Liang, Y. F.; Hu, G. H.; Liu, Y. L.; Li, Y. L.; Zhao, N.

    2014-09-01

    High-confinement regime with high-frequency and low-energy-loss small edge localized modes (ELMs) was achieved in Experimental Advanced Superconducting Tokamak by using the lower hybrid current drive and ion cyclotron resonance heating with lithium wall conditioning. The small ELMs are usually accompanied with a quasi-coherent mode at frequency around 30 kHz, as detected by the Langmuir probes near the separatrix. The coherent mode, with weak magnetic perturbations different from the precursor of conventional ELMs, propagates in the electron diamagnetic drift direction in the lab frame with the poloidal wavelength λθ ˜ 14 cm, corresponding to both high poloidal and toroidal mode numbers (m > 60 and n > 12). This coherent mode, carrying high-temperature high-density filament-like plasma, drives considerable transport from the pedestal region into the scrape-off layer towards divertor region. The co-existence of small ELMs and quasi-coherent modes is beneficial for the sustainment of long pulse H-mode regime without significant confinement degradation.

  12. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak.

    PubMed

    Seo, Seong-Heon; Park, Jinhyung; Wi, H M; Lee, W R; Kim, H S; Lee, T G; Kim, Y S; Kang, Jin-Seob; Bog, M G; Yokota, Y; Mase, A

    2013-08-01

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6-54 GHz), V band (48-72 GHz), and W band (72-108 GHz) to measure the density up to 7 × 10(19) m(-3) when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

  13. Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures.

    PubMed

    Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J; Pfeiffer, Loren N; West, Ken W; Rokhinson, Leonid P

    2015-06-11

    Search for Majorana fermions renewed interest in semiconductor-superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor-superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields.

  14. Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures

    PubMed Central

    Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J.; Pfeiffer, Loren N.; West, Ken W.; Rokhinson, Leonid P.

    2015-01-01

    Search for Majorana fermions renewed interest in semiconductor–superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor–superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields. PMID:26067452

  15. High temperature superconductivity technology for advanced space power systems

    NASA Technical Reports Server (NTRS)

    Faymon, Karl A.; Myers, Ira T.; Connolly, Denis J.

    1990-01-01

    In 1987, the Lewis Research center of the NASA and the Argonne National Laboratory of the Department of Energy joined in a cooperative program to identify and assess high payoff space and aeronautical applications of high temperature superconductivity (HTSC). The initial emphasis of this effort was limited, and those space power related applications which were considered included microwave power transmission and magnetic energy storage. The results of these initial studies were encouraging and indicated the need of further studies. A continuing collaborative program with Argonne National Laboratory has been formulated and the Lewis Research Center is presently structuring a program to further evaluate HTSC, identify applications and define the requisite technology development programs for space power systems. This paper discusses some preliminary results of the previous evaluations in the area of space power applications of HTSC which were carried out under the joint NASA-DOE program, the future NASA-Lewis proposed program, its thrusts, and its intended outputs and give general insights on the anticipated impact of HTSC for space power applications of the future.

  16. Observations of compound sawteeth in ion cyclotron resonant heating plasma using ECE imaging on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Hussain, Azam; Zhao, Zhenling; Xie, Jinlin; Zhu, Ping; Liu, Wandong; Ti, Ang

    2016-04-01

    The spatial and temporal evolutions of compound sawteeth were directly observed using 2D electron cyclotron emission imaging on experimental advanced superconducting tokamak. The compound sawtooth consists of partial and full collapses. After partial collapse, the hot core survives as only a small amount of heat disperses outwards, whereas in the following full collapse a large amount of heat is released and the hot core dissipates. The presence of two q = 1 surfaces was not observed. Instead, the compound sawtooth occurs mainly at the beginning of an ion cyclotron resonant frequency heating pulse and during the L-H transition phase, which may be related to heat transport suppression caused by a decrease in electron heat diffusivity.

  17. Mechanical Design of a High Energy Beam Absorber for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab

    SciTech Connect

    Baffes, C.; Church, M.; Leibfritz, J.; Oplt, S.; Rakhno, I.; /Fermilab

    2012-05-10

    A high energy beam absorber has been built for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In the facility's initial configuration, an electron beam will be accelerated through 3 TTF-type or ILC-type SRF cryomodules to an energy of 750MeV. The electron beam will be directed to one of multiple downstream experimental and diagnostic beam lines and then deposited in one of two beam absorbers. The facility is designed to accommodate up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the driving design condition for the beam absorbers. The beam absorbers consist of water-cooled graphite, aluminum and copper layers contained in a helium-filled enclosure. This paper describes the mechanical implementation of the beam absorbers, with a focus on thermal design and analysis. The potential for radiation-induced degradation of the graphite is discussed.

  18. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lee, W; Park, H K; Lee, D J; Nam, Y U; Leem, J; Kim, T K

    2016-04-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm(-1). The upper limit corresponds to the normalized wavenumber kθρe of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.

  19. Development of a 4.5 K Pulse Tube Cryocooler for Superconducting Electronics

    NASA Astrophysics Data System (ADS)

    Nast, Ted; Olson, Jeff; Champagne, Patrick; Mix, Jack; Evtimov, Bobby; Roth, Eric; Collaco, Andre

    2008-03-01

    Lockheed Martin's (LM) Advanced Technology Center (ATC) has developed a four stage pulse tube cryocooler (stirling-type pulse tube system) to provide cooling at 4.5 K for superconducting digital electronics communications programs. These programs utilize superconducting niobium integrated circuits [1, 2]. A prior ATC 4 stage unit has provided cooling to 3.8 K. [3] The relatively high cooling loads for the present program led us to a new design which improves the 4.5 K power efficiency over prior systems. This design includes a unique pulse tube approach using both He-3 and He-4 working gas in two compression spaces. The compressor utilizes our standard moving magnet linear motor, clearance seal and flexure bearing system. The system is compact, lightweight and reliable and utilizes our aerospace cooler technology to provide unlimited lifetime. The unit is a proof of concept, but the construction is at an engineering model level. Follow on activities for improvements of performance and more compact packaging and future production for ground based communication systems is anticipated. This paper presents the experimental results at various cooling conditions. Primary results are shown for HYPRES cooling requirements and data is also included at lower cooling loads that may be required for future space missions. The system provides a maximum of 42 mW @ 4.5 K and a no load temperature of 3 K. The majority of this work was subcontracted by HYPRES and funded by the Army and Navy. A small part of this effort to obtain data at lower cooling loads (1-10 mW @ 4.5 K) was funded by LM internal funds.

  20. Advanced Electronics. Curriculum Development. Bulletin 1778.

    ERIC Educational Resources Information Center

    Eppler, Thomas

    This document is a curriculum guide for a 180-hour course in advanced electronics for 11th and 12th grades that has four instructional units. The instructional units are orientation, discrete components, integrated circuits, and electronic systems. The document includes a course flow chart; a two-page section that describes the course, lists…

  1. Electron-Phonon Interaction in Oxide Superconductors - Proceedings of the First Cinvestav Superconductivity Symposium

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Hashimoto, Takasu

    1991-12-01

    The Table of Contents for the book is as follows: * List of Invited Speakers * Preface * PHONONS * Lattice Vibrations of the Cuprate Superconductors * INFRARED * Evidence of Strong Electron-Phonon Interaction from the Infrared Spectra of YBa2Cu3O7 * Electron-Phonon Interaction and Infrared Spectra of High Temperature Superconductors * TUNNELING * Tunneling Studies of Bismuthate and Cuprate Superconductors * Phonon Mechanism of the High Tc Superconductivity Based on the Tunneling Structure * LATTICE INSTABILITIES * Lattice Instabilities in High Temperature Superconductors: The X Point Tilt Energy Surface for La2-xBaxCuO4 * Structural Instability and Strong Coupling in Oxide Superconductors * ISOTOPE EFFECT * On the Isotope Effect * Electron-Phonon Coupling, Oxygen Isotope Effect and Superconductivity in Ba1-xKxBio3 * BCJ AND ELIASHBERG THEORY * Weak Coupling Theory of the High Tc Superconductors Based on the Electron-Phonon Interaction * Phonon Self-Energy Effects in Migdal-Eliashberg Theory * OTHER TOPICS * Electron-Phonon Interaction and Superconductivity in BaxK1-xBio3 * The Effect of Strong Coulomb Correlations on Electron-Phonon Interactions in the Copper Oxides: Implications for Transport * EXPERIMENT (OTHER TOPICS) * Zinc Substitution Effects on the Superconducting Properties of Nd1.85Ce0.15CuO4-δ * SUMMARY * Manifestations of the e-ph Interaction: A Summary * Author Index

  2. Advances in superconductivity; Proceedings of the First International Symposium on Superconductivity (ISS '88), Nagoya, Japan, Aug. 28-31, 1988

    NASA Astrophysics Data System (ADS)

    Kitazawa, Koichi; Ishiguro, Takehiko

    Papers on superconductivity and superconductor applications are presented, covering topics such as electric power systems, magnetic energy storage, fusion power, magnetic resonance imaging, transportation, Josephson digital and analog devices with niobium junctions, Josephson parametric amplifiers, and organic superconductors. Topics related to oxide superconductors include superconductor mechanisms, crystal chemistry, electronic structure, phase diagrams, crystal growth, processing, microstructure, tapes and thick films, wires, and coils. Other topics include coherence length, magnetic properties, critical current, irradiation effect, thin film processing, chemical reactions and superconductor/substrate interaction, tunneling and tunneling junction, Bi- and Tl-based cuprate superconductors, the 110 K phase of Bi-Sr-Ca-Cu-O fabrication and microstructure, research policies, and trends in technology.

  3. ASC 84: applied superconductivity conference. Final program and abstracts

    SciTech Connect

    Not Available

    1984-01-01

    Abstracts are given of presentations covering: superconducting device fabrication; applications of rf superconductivity; conductor stability and losses; detectors and signal processing; fusion magnets; A15 and Nb-Ti conductors; stability, losses, and various conductors; SQUID applications; new applications of superconductivity; advanced conductor materials; high energy physics applications of superconductivity; electronic materials and characterization; general superconducting electronics; ac machinery and new applications; digital devices; fusion and other large scale applications; in-situ and powder process conductors; ac applications; synthesis, properties, and characterization of conductors; superconducting microelectronics. (LEW)

  4. Emergence of superconductivity in the canonical heavy-electron metal YbRh₂Si₂.

    PubMed

    Schuberth, Erwin; Tippmann, Marc; Steinke, Lucia; Lausberg, Stefan; Steppke, Alexander; Brando, Manuel; Krellner, Cornelius; Geibel, Christoph; Yu, Rong; Si, Qimiao; Steglich, Frank

    2016-01-29

    The smooth disappearance of antiferromagnetic order in strongly correlated metals commonly furnishes the development of unconventional superconductivity. The canonical heavy-electron compound YbRh2Si2 seems to represent an apparent exception from this quantum critical paradigm in that it is not a superconductor at temperature T ≥ 10 millikelvin (mK). Here we report magnetic and calorimetric measurements on YbRh2Si2, down to temperatures as low as T ≈ 1 mK. The data reveal the development of nuclear antiferromagnetic order slightly above 2 mK and of heavy-electron superconductivity almost concomitantly with this order. Our results demonstrate that superconductivity in the vicinity of quantum criticality is a general phenomenon.

  5. Fabrication of high-Tc superconducting hot electron bolometers for terahertz mixer applications

    NASA Astrophysics Data System (ADS)

    Villegier, Jean-Claude; Degardin, Annick F.; Guillet, Bruno; Houze, Frederic; Kreisler, Alain J.; Chaubet, Michel

    2005-03-01

    Superconducting Hot Electron Bolometer (HEB) mixers are a competitive alternative to Schottky diode mixers or other conventional superconducting receiver technologies in the terahertz frequency range because of their ultrawide bandwidth (from millimeter waves to the visible), high conversion gain, and low intrinsic noise level, even at 77 K. A new technological process has been developed to realize HEB mixers based on high temperature superconducting materials, using 15 to 40 nm thick layers of YBa2Cu3O7-δ (YBCO), sputtered on MgO (100) substrates by hollow cathode magnetron sputtering. Critical temperature values of YBCO films were found in the 85 to 91 K range. Sub-micron HEB bridges (0.8 μm x 0.8 μm) were obtained by combining electronic and UV lithography followed by selective etching techniques. Realization of YBCO HEB coupling to planar integrated gold antennas was also considered.

  6. Pressure effects on the electronic structure and superconducting critical temperature of Li2B2.

    PubMed

    Martínez-Guerra, E; Ortíz-Chi, F; Curtarolo, S; de Coss, R

    2014-03-19

    We present the structural, electronic and superconducting properties of Li2B2 under pressure within the framework of the density functional theory. The structural parameters, electronic band structure, phonon frequency of the E2g phonon mode and superconducting critical temperature Tc were calculated for pressures up to 20 GPa. We predicted that the superconducting critical temperature of Li2B2 is about 11 K and this decreases as pressure increases. We found that even though the lattice dynamics of the E2g phonon mode is similar to MgB2, the reduction of the σ-band density of states at Fermi level and the raising of the E2g phonon frequency with pressure were determinant to decrease λ and consequently Tc.

  7. Effects of Surface Electron Doping and Substrate on the Superconductivity of Epitaxial FeSe Films.

    PubMed

    Zhang, W H; Liu, X; Wen, C H P; Peng, R; Tan, S Y; Xie, B P; Zhang, T; Feng, D L

    2016-03-09

    Superconductivity in FeSe is greatly enhanced in films grown on SrTiO3 substrates, although the mechanism behind remains unclear. Recently, surface potassium (K) doping has also proven able to enhance the superconductivity of FeSe. Here, by using scanning tunneling microscopy, we compare the K doping dependence of the superconductivity in FeSe films grown on two substrates: SrTiO3 (001) and graphitized SiC (0001). For thick films (20 unit cells (UC)), the optimized superconducting (SC) gaps are of similar size (∼9 meV) regardless of the substrate. However, when the thickness is reduced to a few UC, the optimized SC gap is increased up to ∼15 meV for films on SrTiO3, whereas it remains unchanged for films on SiC. This clearly indicates that the FeSe/SrTiO3 interface can further enhance the superconductivity, beyond merely doping electrons. Intriguingly, we found that this interface enhancement decays exponentially as the thickness increases, with a decay length of 2.4 UC, which is much shorter than the length scale for relaxation of the lattice strain, pointing to interfacial electron-phonon coupling as the likely origin.

  8. Current status of the superconducting RF linac driver for the JAERI Free Electron Laser Facility

    SciTech Connect

    Minehara, E.J.; Sugimoto, M.; Sawamura, M.

    1995-12-31

    The commissioning of the superconducting rf linac driver for the JAERI free electron laser facility has been successfully performed at 10{approx}20 MeV before the end of the 1994 Japanese fiscal year. The performance obtained during the commissioning and current status of the JAERI FEL program at Tokai will be reported in detail.

  9. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

    PubMed Central

    Di Bernardo, A.; Millo, O.; Barbone, M.; Alpern, H.; Kalcheim, Y.; Sassi, U.; Ott, A. K.; De Fazio, D.; Yoon, D.; Amado, M.; Ferrari, A. C.; Linder, J.; Robinson, J. W. A.

    2017-01-01

    Electron pairing in the vast majority of superconductors follows the Bardeen–Cooper–Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K. PMID:28102222

  10. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor.

    PubMed

    Di Bernardo, A; Millo, O; Barbone, M; Alpern, H; Kalcheim, Y; Sassi, U; Ott, A K; De Fazio, D; Yoon, D; Amado, M; Ferrari, A C; Linder, J; Robinson, J W A

    2017-01-19

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  11. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

    NASA Astrophysics Data System (ADS)

    di Bernardo, A.; Millo, O.; Barbone, M.; Alpern, H.; Kalcheim, Y.; Sassi, U.; Ott, A. K.; de Fazio, D.; Yoon, D.; Amado, M.; Ferrari, A. C.; Linder, J.; Robinson, J. W. A.

    2017-01-01

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  12. Superconducting single electron transistor for charge sensing in Si/SiGe-based quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Zhen

    Si-based quantum devices, including Si/SiGe quantum dots (QD), are promising candidates for spin-based quantum bits (quits), which are a potential platform for quantum information processing. Meanwhile, qubit readout remains a challenging task related to semiconductor-based quantum computation. This thesis describes two readout devices for Si/SiGe QDs and the techniques for developing them from a traditional single electron transistor (SET). By embedding an SET in a tank circuit and operating it in the radio-frequency (RF) regime, a superconducting RF-SET has quick response as well as ultra high charge sensitivity and can be an excellent charge sensor for the QDs. We demonstrate such RF-SETs for QDs in a Si/SiGe heterostructure. Characterization of the SET in magnetic fields is studied for future exploration of advanced techniques such as spin detection and spin state manipulation. By replacing the tank circuit with a high-quality-factor microwave cavity, the embedded SET will be operated in the supercurrent regime as a single Cooper pair transistor (CPT) to further increase the charge sensitivity and reduce any dissipation. The operating principle and implementation of the cavity-embedded CPT (cCPT) will be introduced.

  13. Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity.

    PubMed

    Davis, J C Séamus; Lee, Dung-Hai

    2013-10-29

    Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron-electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron-electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electron-electron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs.

  14. General conditions for proximity induced odd-frequency superconductivity in two-dimensional electronic systems

    NASA Astrophysics Data System (ADS)

    Rossi, Enrico; Triola, Christopher; Badiane, Driss; Balatsky, Alexander V.

    We obtain the general conditions for the emergence of odd-frequency superconducting pairing in a two-dimensional (2D) electronic system proximity-coupled to a superconductor, making minimal assumptions about both the 2D system and the superconductor. Using our general results we show that a simple heterostructure formed by a monolayer of a group VI transition metal dichalcogenide, such as molybdenum disulfide, and an s-wave superconductor with Rashba spin-orbit coupling will exhibit odd-frequency superconducting pairing. Work supported by US DOE BES E304, KAW, ACS-PRF-53581-DNI5, and NSF-DMR-1455233.

  15. Ion beam processing of advanced electronic materials

    SciTech Connect

    Cheung, N.W.; Marwick, A.D.; Roberto, J.B.; International Business Machines Corp., Yorktown Heights, NY . Thomas J. Watson Research Center; Oak Ridge National Lab., TN )

    1989-01-01

    This report contains research programs discussed at the materials research society symposia on ion beam processing of advanced electronic materials. Major topics include: shallow implantation and solid-phase epitaxy; damage effects; focused ion beams; MeV implantation; high-dose implantation; implantation in III-V materials and multilayers; and implantation in electronic materials. Individual projects are processed separately for the data bases. (CBS)

  16. Observation of pedestal turbulence in edge localized mode-free H-mode on experimental advanced superconducting tokamak

    SciTech Connect

    Han, X. Zhang, T.; Zhang, S. B.; Wang, Y. M.; Shi, T. H.; Liu, Z. X.; Kong, D. F.; Qu, H.; Gao, X.

    2014-10-15

    Two different pedestal turbulence structures have been observed in edge localized mode-free phase of H-mode heated by lower hybrid wave and RF wave in ion cyclotron range of frequencies (ICRF) on experimental advanced superconducting tokamak. When the fraction of ICRF power P{sub ICRF}/P{sub total} exceeds 0.7, coherent mode is observed. The mode is identified as an electromagnetic mode, rotating in electron diamagnetic direction with a frequency around 50 kHz and toroidal mode number n = −3. Whereas when P{sub ICRF}/P{sub total} is less than 0.7, harmonic mode with frequency f = 40–300 kHz appears instead. The characteristics of these two modes are demonstrated preliminarily. The threshold value of heating power and also the plasma parameters are distinct.

  17. Space applications of superconducting microwave electronics at NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Leonard, R. F.; Bhasin, K. B.; Romanofsky, R. R.; Cubbage, C. D.; Chorey, C. Z.

    1993-01-01

    Since the discovery of high temperature superconductivity in 1987, NASA Lewis Research Center has been involved in efforts to demonstrate its advantages for applications involving microwave electronics in space, especially space communications. The program included thin film fabrication by means of laser ablation. Specific circuitry which was investigated includes microstrip ring resonators at 32 GHz, phase shifters which utilize a superconducting, optically activated switch, an 8x8 32 GHz superconducting microstrip antenna array, and an HTS-ring-resonator stabilized oscillator at 8 GHz. The latter two components are candidates for use in space experiments which are described in other papers. Experimental data on most of the circuits are presented as well as, in some cases, a comparison of their performance with an identical circuit utilizing gold or copper metallization.

  18. Electronic behavior of superconducting SmFeAsO0.75

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Ding, Y.; Zheng, B. C.; Shi, Z. X.; Ren, Z. A.

    2011-04-01

    High-quality polycrystalline SmFeAsO0.75 was synthesized with a superconducting transition width less than 1 K, and the electronic behavior was systematically studied by transport and specific heat measurements. An obvious superconducting jump was witnessed, together with a very small normalized superconducting jump, ΔC/γnTc ˜ 0.2, which is much smaller than expected from the BCS theory. A strong temperature-dependent Hall coefficient was found and attributed to the partial gapping of the Fermi surface up to the temperature of 160 K, which was predicted and supported by the emergence of the pseudogap. The charge-carrier density as well as the effective mass were also obtained and discussed in detail.

  19. Microscopic annealing process and its impact on superconductivity in T'-structure electron-doped copper oxides.

    PubMed

    Kang, Hye Jung; Dai, Pengcheng; Campbell, Branton J; Chupas, Peter J; Rosenkranz, Stephan; Lee, Peter L; Huang, Qingzhen; Li, Shiliang; Komiya, Seiki; Ando, Yoichi

    2007-03-01

    High-transition-temperature superconductivity arises in copper oxides when holes or electrons are doped into the CuO(2) planes of their insulating parent compounds. Whereas hole doping quickly induces metallic behaviour and superconductivity in many cuprates, electron doping alone is insufficient in materials such as R(2)CuO(4) (R is Nd, Pr, La, Ce and so on), where it is necessary to anneal an as-grown sample in a low-oxygen environment to remove a tiny amount of oxygen in order to induce superconductivity. Here we show that the microscopic process of oxygen reduction repairs Cu deficiencies in the as-grown materials and creates oxygen vacancies in the stoichiometric CuO(2) planes, effectively reducing disorder and providing itinerant carriers for superconductivity. The resolution of this long-standing materials issue suggests that the fundamental mechanism for superconductivity is the same for electron- and hole-doped copper oxides.

  20. Advanced Electronics Systems 1, Industrial Electronics 3: 9327.03.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    The 135 clock-hour course for the 12th year consists of outlines for blocks of instruction on transistor applications to basic circuits, principles of single sideband communications, maintenance practices, preparation for FCC licenses, application of circuits to advanced electronic systems, nonsinusoidal wave shapes, multivibrators, and blocking…

  1. Overview of advanced law enforcement electronic technology

    NASA Astrophysics Data System (ADS)

    Harden, W. R.

    1995-05-01

    Law enforcement and security management are using advanced electronic equipment to increase the effectiveness and efficiency of the budget restricted police officer force. Currently there is also significant national attention concerning the possible utilization of 'military' electronic hardware to implement the much sought after 'force multiplier' which can help to alleviate each jurisdictions economic restrictions. However, as we are now finding, the transfer of 'military' hardware for utilization by law enforcement personnel is not as economically viable as hoped. This paper will address some of the recent advances in electronic technology that are being derived from the military technology base. Additionally, comments are given concerning the economic impact as the technology is transferred to the law enforcement community.

  2. Breakdown of electron-pairs in the presence of an electric field of a superconducting ring.

    PubMed

    Pandey, Bradraj; Dutta, Sudipta; Pati, Swapan K

    2016-05-18

    The quantum dynamics of quasi-one-dimensional ring with varying electron filling factors is investigated in the presence of an external electric field. The system is modeled within a Hubbard Hamiltonian with attractive Coulomb correlation, which results in a superconducting ground state when away from half-filling. The electric field is induced by applying time-dependent Aharonov-Bohm flux in the perpendicular direction. To explore the non-equilibrium phenomena arising from the field, we adopt exact diagonalization and the Crank-Nicolson numerical method. With an increase in electric field strength, the electron pairs, a signature of the superconducting phase, start breaking and the system enters into a metallic phase. However, the strength of the electric field for this quantum phase transition depends on the electronic correlation. This phenomenon has been confirmed by flux-quantization of time-dependent current and pair correlation functions.

  3. Unconventional superconductivity in generalized Hubbard model: role of electron-hole symmetry breaking terms

    NASA Astrophysics Data System (ADS)

    Wysokiński, Marcin M.; Kaczmarczyk, Jan

    2017-03-01

    We investigate the effect of the electron-hole (e-h) symmetry breaking on d-wave superconductivity induced by non-local effects of correlations in the generalized Hubbard model. The symmetry breaking is introduced in a two-fold manner: by the next-to-nearest neighbor hopping of electrons and by the charge-bond interaction—the off-diagonal term of the Coulomb potential. Both terms lead to a pronounced asymmetry of the superconducting order parameter. The next-to-nearest neighbor hopping enhances superconductivity for h-doping, while diminishes it for e-doping. The charge-bond interaction alone leads to the opposite effect and, additionally, to the kinetic-energy gain upon condensation in the underdoped regime. With both terms included, with similar amplitudes, the height of the superconducting dome and the critical doping remain in favor of h-doping. The influence of the charge-bond interaction on deviations from {{d}{{x2}-{{y}2}}} symmetry of the shape of the gap at the Fermi surface in the momentum space is briefly discussed.

  4. Numerical study of Alfvén eigenmodes in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Hu, Youjun; Li, Guoqiang; Yang, Wenjun; Zhou, Deng; Ren, Qilong; Gorelenkov, N. N.; Cai, Huishan

    2014-05-15

    Alfvén eigenmodes in up-down asymmetric tokamak equilibria are studied by a new magnetohydrodynamic eigenvalue code. The code is verified with the NOVA code for the Solovév equilibrium and then is used to study Alfvén eigenmodes in a up-down asymmetric equilibrium of the Experimental Advanced Superconducting Tokamak. The frequency and mode structure of toroidicity-induced Alfvén eigenmodes are calculated. It is demonstrated numerically that up-down asymmetry induces phase variation in the eigenfunction across the major radius on the midplane.

  5. Conceptual design of a fast-ion D-alpha diagnostic on experimental advanced superconducting tokamak

    SciTech Connect

    Huang, J. Wan, B.; Hu, L.; Hu, C.; Heidbrink, W. W.; Zhu, Y.; Hellermann, M. G. von; Gao, W.; Wu, C.; Li, Y.; Fu, J.; Lyu, B.; Yu, Y.; Ye, M.; Shi, Y.

    2014-11-15

    To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been planned and is presently under development on Experimental Advanced Superconducting Tokamak. The greatest challenges for the design of a FIDA diagnostic are its extremely low intensity levels, which are usually significantly below the continuum radiation level and several orders of magnitude below the bulk-ion thermal charge-exchange feature. Moreover, an overlaying Motional Stark Effect (MSE) feature in exactly the same wavelength range can interfere. The simulation of spectra code is used here to guide the design and evaluate the diagnostic performance. The details for the parameters of design and hardware are presented.

  6. Analytical studies of advanced high-field designs: 20-tesla large-bore superconducting magnets

    SciTech Connect

    Hoard, R.W.; Cornish, D.N.; Scanlan, R.M.; Zbasnik, J.P.; Leber, R.L.; Hickman, R.B.; Lee, J.D.

    1983-09-30

    Several emerging technologies have been combined in a conceptual design study demonstrating the feasibility of producing ultrahigh magnetic fields from large-bore superconducting solenoid magnets. Several designs have been produced that approach peak fields of 20-T in 2.0-m diameter inner bores. The analytical expressions comprising the main features of CONDUCTOR and ADVMAGNET, the two computer programs used in the design of these advanced magnets, are also discussed. These magnets and design techniques will make a paramount contribution to the national mirror-fusion endeavor and to the newly emerging field of nuclear magnetic resonance (NMR) whole-body scanners.

  7. Advanced Electron Microscopy in Materials Physics

    SciTech Connect

    Zhu, Y.; Jarausch, K.

    2009-06-01

    Aberration correction has opened a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes and extending information limits. The imaging and analytical performance of these corrector-equipped microscopes affords an unprecedented opportunity to study structure-property relationships of matter at the atomic scale. This new generation of microscopes is able to retrieve high-quality structural information comparable to neutron and synchrotron x-ray experiments, but with local atomic resolution. These advances in instrumentation are accelerating the research and development of various functional materials ranging from those for energy generation, conversion, transportation and storage to those for catalysis and nano-device applications. The dramatic improvements in electron-beam illumination and detection also present a host of new challenges for the interpretation and optimization of experiments. During 7-9 November 2007, a workshop, entitled 'Aberration Corrected Electron Microscopy in Material Physics', was convened at the Center for Functional Nanomaterials, Brookhaven National Laboratories (BNL) to address these opportunities and challenges. The workshop was co-sponsored by Hitachi High Technologies, a leader in electron microscopy instrumentation, and BNL's Institute of Advanced Electron Microscopy, a leader in materials physics research using electron microscopy. The workshop featured presentations by internationally prominent scientists working at the frontiers of electron microscopy, both on developing instrumentation and applying it in materials physics. The meeting, structured to stimulate scientific exchanges and explore new capabilities, brought together {approx}100 people from over 10 countries. This special issue complies many of the advances in instrument performance and materials physics reported by the invited speakers and attendees at the workshop.

  8. Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity

    PubMed Central

    Davis, J. C. Séamus; Lee, Dung-Hai

    2013-01-01

    Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron–electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron–electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electron–electron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs. PMID:24114268

  9. Multiband Semimetallic Electronic Structure of Superconducting Ta2PdSe5

    PubMed Central

    Singh, David Joseph

    2015-01-01

    We report the electronic structure and related properties of the superconductor Ta2PdSe5 as determined from density functional calculations. The Fermi surface has two disconnected sheets, both derived from bands of primarily chalcogenide p states. These are a corrugated hole cylinder and a heavier complex shaped electron sheet. The sheets contain 0.048 holes and a compensating number of electrons per formula unit, making the material a semimetallic superconductor. The results support the presence of two band superconductivity, although a discrepancy in the specific heat is noted. This discrepancy is discussed as a possible consequence of Pd deficiency in samples. PMID:25909894

  10. Multiband semimetallic electronic structure of superconducting Ta2PdSe5

    DOE PAGES

    Singh, David Joseph

    2015-04-24

    We report the electronic structure and related properties of the superconductor Ta2PdSe5 as determined from density functional calculations. The Fermi surface has two disconnected sheets, both derived from bands of primarily chalcogenide p states. These are a corrugated hole cylinder and a heavier complex shaped electron sheet. The sheets contain 0.048 holes and a compensating number of electrons per formula unit, making the material a semimetallic superconductor. The results support the presence of two band superconductivity, although a discrepancy in the specific heat is noted. This discrepancy is discussed as a possible consequence of Pd deficiency in samples.

  11. Simulations of multipacting in the cathode stalk and FPC of 112 MHz superconducting electron gun

    SciTech Connect

    Xin T.; Ben-Zvi, I.; Belomestnykh, S.; Chang, X.; Rao, T.; Skaritka, J.; Wu, Q.; Wang, E.; Liang, X.

    2012-05-20

    A 112 MHz superconducting quarter-wave resonator electron gun will be used as the injector of the Coherent Electron Cooling (CEC) proof-of-principle experiment at BNL. Furthermore, this electron gun can be used for testing of the performance of various high quantum efficiency photocathodes. In a previous paper, we presented the design of the cathode stalks and a Fundamental Power Coupler (FPC). In this paper we present updated designs of the cathode stalk and FPC. Multipacting in the cathode stalk and FPC was simulated using three different codes. All simulation results show no serious multipacting in the cathode stalk and FPC.

  12. The superconducting phase and electronic excitations of (Rb,Cs) Fe 2 As 2

    NASA Astrophysics Data System (ADS)

    Kanter, J.; Shermadini, Z.; Khasanov, R.; Amato, A.; Bukowski, Z.; Batlogg, B.

    2011-03-01

    We present specific heat, transport and Muon-Spin Rotation (μ SR) results on (Rb,Cs) Fe 2 As 2 . RbFe 2 As 2 was only recently found to be superconducting below 2.6 K by Bukowski et al. Compared to the related BaFe 2 As 2 the electron density is lower and no magnetic order is observed. For the superconducting phase the superfluid density was calculated from μ SR data. The temperature dependence of the superfluid density and the magnetic penetration depth is well described by a multi-gap scenario. In addition the electronic contribution the specific heat was studied for different compositions and magnetic fields and reveals a high value for the Sommerfeld coefficient γ .

  13. Electron Heating and Quasiparticle Tunnelling in Superconducting Charge Qubits

    NASA Technical Reports Server (NTRS)

    Shaw, M. D.; Bueno, J.; Delsing, P.; Echternach, P. M.

    2008-01-01

    We have directly measured non-equilibrium quasiparticle tunnelling in the time domain as a function of temperature and RF carrier power for a pair of charge qubits based on the single Cooper-pair box, where the readout is performed with a multiplexed quantum capacitance technique. We have extracted an effective electron temperature for each applied RF power, using the data taken at the lowest power as a reference curve. This data has been fit to a standard T? electron heating model, with a reasonable correspondence with established material parameters.

  14. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    SciTech Connect

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R. Santhosh, M.

    2015-06-24

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  15. Correlated magnetic impurities in a superconductor: electron density profiles and robustness of superconductivity.

    PubMed

    Sacramento, P D; Dugaev, V K; Vieira, V R; Araújo, M A N

    2010-01-20

    The insertion of magnetic impurities in a conventional superconductor leads to various effects. In this work we show that the electron density is affected by the spins (considered as classical) both locally and globally. The charge accumulation is solved self-consistently. This affects the transport properties along magnetic domain walls. Also, we show that superconductivity is more robust if the spin locations are not random but correlated.

  16. The Necessity for a DoD Capability in Superconducting Electronics

    DTIC Science & Technology

    1990-11-01

    Aocession For NTIS GRA&I DTIC TAB Ut•, anounced Q Ju3tification by- a_ D~isribution/ Availability Codes Avail and/or Dist Special iiii i i PREFACE In January...initiatives with pressing needs for signal and data processing in systems on land, on sea, in the air, or on space-based platforms that demand close to 109...6. S. Takada, Chief, Superconductivity Electronics Section, Electrotechnical Laboratory, press release, December 1989. 7. A. Morita and S. Ishihara

  17. Chemically gated electronic structure of a superconducting doped topological insulator system

    NASA Astrophysics Data System (ADS)

    Wray, L. A.; Xu, S.; Neupane, M.; Fedorov, A. V.; Hor, Y. S.; Cava, R. J.; Hasan, M. Z.

    2013-07-01

    Angle resolved photoemission spectroscopy is used to observe changes in the electronic structure of bulk-doped topological insulator CuxBi2Se3 as additional copper atoms are deposited onto the cleaved crystal surface. Carrier density and surface-normal electrical field strength near the crystal surface are estimated to consider the effect of chemical surface gating on atypical superconducting properties associated with topological insulator order, such as the dynamics of theoretically predicted Majorana Fermion vortices.

  18. New generation of cryogen free advanced superconducting magnets for neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Kirichek, O.; Brown, J.; Adroja, D. T.; Manuel, P.; Kouzmenko, G.; Bewley, R. I.; Wotherspoon, R.

    2012-12-01

    Recent advances in superconducting technology and cryocooler refrigeration have resulted in a new generation of advanced superconducting magnets for neutron beam applications. These magnets have outstanding parameters such as high homogeneity and stability at highest magnetic fields possible, a reasonably small stray field, low neutron scattering background and larger exposure to neutron detectors. At the same time the pulse tube refrigeration technology provides a complete re-condensing regime which allows to minimise the requirements for cryogens without introducing additional noise and mechanical vibrations. The magnets can be used with dilution refrigerator insert which expands the temperature range from 20mK to 300K. Here we are going to present design, test results and the operational data of the 14T magnet for neutron diffraction and the 9T wide angle chopper magnet for neutron spectroscopy developed by Oxford Instruments in collaboration with ISIS neutron source. First scientific results obtained from the neutron scattering experiments with these magnets are also going to be discussed.

  19. Edge localized mode characteristics during edge localized mode mitigation by supersonic molecular beam injection in Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Lee, H. Y.; Hong, J. H.; Jang, J. H.; Park, J. S.; Choe, Wonho; Hahn, S. H.; Bak, J. G.; Lee, J. H.; Ko, W. H.; Lee, K. D.; Lee, S. H.; Lee, H. H.; Juhn, J.-W.; Kim, H. S.; Yoon, S. W.; Han, H.; Ghim, Y.-C.

    2015-12-15

    It has been reported that supersonic molecular beam injection (SMBI) is an effective means of edge localized mode (ELM) mitigation. This paper newly reports the changes in the ELM, plasma profiles, and fluctuation characteristics during ELM mitigation by SMBI in Korea Superconducting Tokamak Advanced Research. During the mitigated ELM phase, the ELM frequency increased by a factor of 2–3 and the ELM size, which was estimated from the D{sub α} amplitude, the fractional changes in the plasma-stored energy and the line-averaged electron density, and divertor heat flux during an ELM burst, decreased by a factor of 0.34–0.43. Reductions in the electron and ion temperatures rather than in the electron density were observed during the mitigated ELM phase. In the natural ELM phase, frequency chirping of the plasma fluctuations was observed before the ELM bursts; however, the ELM bursts occurred without changes in the plasma fluctuation frequency in the mitigated ELM phase.

  20. Superconductivity and metallic behavior in PbxCyOδ structures prepared by focused electron beam induced deposition

    NASA Astrophysics Data System (ADS)

    Winhold, M.; Weirich, P. M.; Schwalb, C. H.; Huth, M.

    2014-10-01

    Focused electron beam induced deposition as a direct-write approach possesses great potential to meet the demands for superconducting nanostructure fabrication especially regarding its 3D patterning capabilities combined with the high resolution in the nanometer regime. So far, however, it was not possible to fabricate superconducting structures with this technique. In this work, we present a lead-based superconductor prepared by focused electron beam induced deposition by dissociation of the precursor tetraethyllead. The as-grown structures exhibit metallic behavior and a minimum resistivity in the normal state of ρ = 16 μΩcm at T = 9 K followed by a superconducting transition at Tc = 7.2 K.

  1. Spin-liquid polymorphism in a correlated electron system on the threshold of superconductivity.

    PubMed

    Zaliznyak, Igor; Savici, Andrei T; Lumsden, Mark; Tsvelik, Alexei; Hu, Rongwei; Petrovic, Cedomir

    2015-08-18

    We report neutron scattering measurements which reveal spin-liquid polymorphism in an "11" iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe(1-x)(S,Se)(x). We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. Our results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike.

  2. First results from solid state neutral particle analyzer on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, J. Z.; Zhu, Y. B.; Zhao, J. L.; Wan, B. N.; Li, J. G.; Heidbrink, W. W.

    2016-11-01

    Full function integrated, compact solid state neutral particle analyzers (ssNPA) based on absolute extreme ultraviolet silicon photodiode have been successfully implemented on the experimental advanced superconducting tokamak to measure energetic particle. The ssNPA system has been operated in advanced current mode with fast temporal and spatial resolution capabilities, with both active and passive charge exchange measurements. It is found that the ssNPA flux signals are increased substantially with neutral beam injection (NBI). The horizontal active array responds to modulated NBI beam promptly, while weaker change is presented on passive array. Compared to near-perpendicular beam, near-tangential beam brings more passive ssNPA flux and a broader profile, while no clear difference is observed on active ssNPA flux and its profile. Significantly enhanced intensities on some ssNPA channels have been observed during ion cyclotron resonant heating.

  3. First results from solid state neutral particle analyzer on experimental advanced superconducting tokamak.

    PubMed

    Zhang, J Z; Zhu, Y B; Zhao, J L; Wan, B N; Li, J G; Heidbrink, W W

    2016-11-01

    Full function integrated, compact solid state neutral particle analyzers (ssNPA) based on absolute extreme ultraviolet silicon photodiode have been successfully implemented on the experimental advanced superconducting tokamak to measure energetic particle. The ssNPA system has been operated in advanced current mode with fast temporal and spatial resolution capabilities, with both active and passive charge exchange measurements. It is found that the ssNPA flux signals are increased substantially with neutral beam injection (NBI). The horizontal active array responds to modulated NBI beam promptly, while weaker change is presented on passive array. Compared to near-perpendicular beam, near-tangential beam brings more passive ssNPA flux and a broader profile, while no clear difference is observed on active ssNPA flux and its profile. Significantly enhanced intensities on some ssNPA channels have been observed during ion cyclotron resonant heating.

  4. Advanced thermal management technologies for defense electronics

    NASA Astrophysics Data System (ADS)

    Bloschock, Kristen P.; Bar-Cohen, Avram

    2012-05-01

    Thermal management technology plays a key role in the continuing miniaturization, performance improvements, and higher reliability of electronic systems. For the past decade, and particularly, the past 4 years, the Defense Advanced Research Projects Agency (DARPA) has aggressively pursued the application of micro- and nano-technology to reduce or remove thermal constraints on the performance of defense electronic systems. The DARPA Thermal Management Technologies (TMT) portfolio is comprised of five technical thrust areas: Thermal Ground Plane (TGP), Microtechnologies for Air-Cooled Exchangers (MACE), NanoThermal Interfaces (NTI), Active Cooling Modules (ACM), and Near Junction Thermal Transport (NJTT). An overview of the TMT program will be presented with emphasis on the goals and status of these efforts relative to the current State-of-the-Art. The presentation will close with future challenges and opportunities in the thermal management of defense electronics.

  5. Polarimetry at the Superconducting Darmstadt Electron Linac S-DALINAC

    NASA Astrophysics Data System (ADS)

    Eckardt, C.; Barday, R.; Bonnes, U.; Brunken, M.; Eichhorn, R.; Enders, J.; Heßler, C.; Müller, W. F. O.; Platz, M.; Poltoratska, Y.; Steiner, B.; Wagner, M.; Weiland, T.

    2009-08-01

    A spin polarized electron source will be installed at the S-DALINAC to extend the existing experimental capabilities polarization. In order to manipulate and monitor the beam polarization a Wien filter and different polarimeters will be installed. The already installed Wien filter and 100 keV Mott polarimeter and the planned 5 MeV Mott, 30-130 MeV Mo/ller and Compton transmission polarimeters are described.

  6. Advances in positron and electron scattering*

    NASA Astrophysics Data System (ADS)

    Limão-Vieira, Paulo; García, Gustavo; Krishnakumar, E.; Petrović, Zoran; Sullivan, James; Tanuma, Hajime

    2016-10-01

    The topical issue on Advances in Positron and Electron Scattering" combines contributions from POSMOL 2015 together with others devoted to celebrate the unprecedented scientific careers of our loyal colleagues and trusted friends Steve Buckman (Australian National University, Australia) and Michael Allan (University of Fribourg, Switzerland) on the occasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-Energy Positron and Positronium Physics and the XIX International Symposium on Electron-Molecule Collisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from 17-20 July 2015. The international workshop and symposium allowed to achieve a very privileged forum of sharing and developing our scientific expertise on current aspects of positron, positronium and antiproton interactions with electrons, atoms, molecules and solid surfaces, and related topics, as well as electron interactions with molecules in both gaseous and condensed phases. Particular topics include studies of electron interactions with biomolecules, electron induced surface chemistry and the study of plasma processes. Recent developments in the study of swarms are also fully addressed.

  7. Intense beam production of highly charged heavy ions by the superconducting electron cyclotron resonance ion source SECRAL.

    PubMed

    Zhao, H W; Sun, L T; Zhang, X Z; Guo, X H; Cao, Y; Lu, W; Zhang, Z M; Yuan, P; Song, M T; Zhao, H Y; Jin, T; Shang, Y; Zhan, W L; Wei, B W; Xie, D Z

    2008-02-01

    There has been increasing demand to provide higher beam intensity and high enough beam energy for heavy ion accelerator and some other applications, which has driven electron cyclotron resonance (ECR) ion source to produce higher charge state ions with higher beam intensity. One of development trends for highly charged ECR ion source is to build new generation ECR sources by utilization of superconducting magnet technology. SECRAL (superconducting ECR ion source with advanced design in Lanzhou) was successfully built to produce intense beams of highly charged ion for Heavy Ion Research Facility in Lanzhou (HIRFL). The ion source has been optimized to be operated at 28 GHz for its maximum performance. The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping. An innovative design of SECRAL is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. For 28 GHz operation, the magnet assembly can produce peak mirror fields on axis of 3.6 T at injection, 2.2 T at extraction, and a radial sextupole field of 2.0 T at plasma chamber wall. During the commissioning phase at 18 GHz with a stainless steel chamber, tests with various gases and some metals have been conducted with microwave power less than 3.5 kW by two 18 GHz rf generators. It demonstrates the performance is very promising. Some record ion beam intensities have been produced, for instance, 810 e microA of O(7+), 505 e microA of Xe(20+), 306 e microA of Xe(27+), and so on. The effect of the magnetic field configuration on the ion source performance has been studied experimentally. SECRAL has been put into operation to provide highly charged ion beams for HIRFL facility since May 2007.

  8. Electrical NEP in Hot-Electron Titanium Superconducting Bolometers

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Pereverzev, Sergey V.; Olaya, David; Wei, Jian; Gershenson, Michael E.; Sergeev, Andrei V.

    2008-01-01

    We are presenting the current progress on the titanium (Ti) hot-electron transition-edge devices. The ultimate goal of this work is to develop a submillimeter Hot-Electron Direct Detector (HEDD) with the noise equivalent power NEP = 10(sup -1) - 10(sup -20) W/Hz(sup 1/2) for the moderate resolution spectroscopy and Cosmic Microwave Background (CMB) studies on future space telescope (e.g., SPICA, SAFIR, SPECS, CMBPol) with cryogenically cooled (approximately 4-5 K) mirrors. Recently, we have achieved the extremely low thermal conductance (approximately 20 fW/K at 300 mK and approximately 0.1 fW/K at 40 mK) due to the electron-phonon decoupling in Ti nanodevices with niobium (Nb) Andreev contacts. This thermal conductance translates into the "phonon-noise" NEP approximately equal to 3 x 10(sup -21) W/Hz(sup 1/2) at 40 mK and NEP approximately equal to 3 x 10(sup -19) W/Hz(sup 1/2) at 300 mK. These record data indicate the great potential of the hot-electron detector for meeting many application needs. Beside the extremely low phonon-noise NEP, the nanobolometers have a very low electron heat capacitance that makes them promising as detectors of single THz photons. As the next step towards the practical demonstration of the HEDD, we fabricated and tested somewhat larger than in Ref.1 devices (approximately 6 micrometers x 0.35 micrometers x 40 nm) whose critical temperature is well reproduced in the range 300-350 mK. The output electrical noise measured in these devices with a low-noise dc SQUID is dominated by the thermal energy fluctuations (ETF) aka "phonon noise". This indicates the high electrothermal loop gain that effectively suppresses the contributions of the Johnson noise and the amplifier (SQUID) noise. The electrical NEP = 6.7 x 10(sup -18) W/Hz(sup 1/2) derived from these measurements is in good agreement with the predictions based on the thermal conductance data. The very low NEP and the high speed (approximately microns) are a unique combination not

  9. Control of the competition between a magnetic phase and a superconducting phase in cobalt-doped and nickel-doped NaFeAs using electron count.

    PubMed

    Parker, Dinah R; Smith, Matthew J P; Lancaster, Tom; Steele, Andrew J; Franke, Isabel; Baker, Peter J; Pratt, Francis L; Pitcher, Michael J; Blundell, Stephen J; Clarke, Simon J

    2010-02-05

    Using a combination of neutron, muon, and synchrotron techniques we show how the magnetic state in NaFeAs can be tuned into superconductivity by replacing Fe by either Co or Ni. The electron count is the dominant factor, since Ni doping has double the effect of Co doping for the same doping level. We follow the structural, magnetic, and superconducting properties as a function of doping to show how the superconducting state evolves, concluding that the addition of 0.1 electrons per Fe atom is sufficient to traverse the superconducting domain, and that magnetic order coexists with superconductivity at doping levels less than 0.025 electrons per Fe atom.

  10. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method

    SciTech Connect

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-15

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

  11. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

    PubMed

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-01

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

  12. Advanced electronics for the CTF MEG system.

    PubMed

    McCubbin, J; Vrba, J; Spear, P; McKenzie, D; Willis, R; Loewen, R; Robinson, S E; Fife, A A

    2004-11-30

    Development of the CTF MEG system has been advanced with the introduction of a computer processing cluster between the data acquisition electronics and the host computer. The advent of fast processors, memory, and network interfaces has made this innovation feasible for large data streams at high sampling rates. We have implemented tasks including anti-alias filter, sample rate decimation, higher gradient balancing, crosstalk correction, and optional filters with a cluster consisting of 4 dual Intel Xeon processors operating on up to 275 channel MEG systems at 12 kHz sample rate. The architecture is expandable with additional processors to implement advanced processing tasks which may include e.g., continuous head localization/motion correction, optional display filters, coherence calculations, or real time synthetic channels (via beamformer). We also describe an electronics configuration upgrade to provide operator console access to the peripheral interface features such as analog signal and trigger I/O. This allows remote location of the acoustically noisy electronics cabinet and fitting of the cabinet with doors for improved EMI shielding. Finally, we present the latest performance results available for the CTF 275 channel MEG system including an unshielded SEF (median nerve electrical stimulation) measurement enhanced by application of an adaptive beamformer technique (SAM) which allows recognition of the nominal 20-ms response in the unaveraged signal.

  13. Roadmap for the design of a superconducting electron cyclotron resonance ion source for Spiral2

    SciTech Connect

    Thuillier, T.; Angot, J.; Lamy, T.; Peaucelle, C.

    2012-02-15

    A review of today achieved A/Q = 3 heavy ions beams is proposed. The daily operation A/Q = 3 ion beam intensities expected at Spiral2 are at the limit or above best record 3rd generation electron cyclotron resonance ion source (ECRIS) intensities. The necessity to build a new fully superconducting to fulfill these requirements is outlined. A discussion on the volume of the future source is proposed and the minimum value of 12 liters is derived. An analysis of the x-ray absorption superconducting ECRIS is presented based on VENUS experimental data and geometry. This study underlines the necessity to include a complete x-ray study at the time of source conception. The specifications foreseen for the new ECRIS are presented, followed with the roadmap for the design.

  14. Topological Metal of NaBi with Ultralow Lattice Thermal Conductivity and Electron-phonon Superconductivity

    PubMed Central

    Li, Ronghan; Cheng, Xiyue; Xie, Qing; Sun, Yan; Li, Dianzhong; Li, Yiyi; Chen, Xing-Qiu

    2015-01-01

    By means of first-principles and ab initio tight-binding calculations, we found that the compound of NaBi is a three-dimensional non-trivial topological metal. Its topological feature can be confirmed by the presence of band inversion, the derived effective Z2 invariant and the non-trivial surface states with the presence of Dirac cones. Interestingly, our calculations further demonstrated that NaBi exhibits the uniquely combined properties between the electron-phonon coupling superconductivity in nice agreement with recent experimental measurements and the obviously anisotropic but extremely low thermal conductivity. The spin-orbit coupling effects greatly affect those properties. NaBi may provide a rich platform to study the relationship among metal, topology, superconductivity and thermal conductivity. PMID:25676863

  15. High sensitive THz superconducting hot electron bolometer mixers and transition edge sensors

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Miao, W.; Zhou, K. M.; Guo, X. H.; Zhong, J. Q.; Shi, S. C.

    2016-11-01

    Terahertz band, which is roughly defined as 0.1 THz to 10 THz, is an interesting frequency region of the electromagnetic spectrum to be fully explored in astronomy. THz observations play key roles in astrophysics and cosmology. High sensitive heterodyne and direct detectors are the main tools for the detection of molecular spectral lines and fine atomic structure spectral lines, which are very important tracers for probing the physical and chemical properties and dynamic processes of objects such as star and planetary systems. China is planning to build an THz telescope at Dome A, Antarctica, a unique site for ground-based THz observations. We are developing THz superconducting hot electron bolometer (HEB) mixers and transition edge sensors (TES), which are quantum limited and back-ground limited detectors, respectively. Here we first introduce the working principles of superconducting HEB and TES, and then mainly present the results achieved at Purple mountain Observatory.

  16. Design and first cold test of BNL superconducting 112 MHz QWR for electron gun applications

    SciTech Connect

    Belomestnykh, S.; Ben-Zvi, I.; Boulware, C.H.; Chang, X.; Grimm, T.L.; Siegel, B.; Than, R.; Winowski, M.

    2011-03-28

    Brookhaven National Laboratory and Niowave, Inc. have designed, fabricated, and performed the first cold test of a superconducting 112 MHz quarter-wave resonator (QWR) for electron gun experiments. The first cold test of the QWR cryomodule has been completed at Niowave. The paper discusses the cryomodule design, presents the cold test results, and outline plans to upgrade the cryomodule for future experiments. A quarter-wave resonator concept of superconducting RF (SRF) electron gun was proposed at BNL for electron cooling ion/proton beams at RHIC. QWRs can be made sufficiently compact even at low RF frequencies (long wavelengths). The long wavelength allows to produce long electron bunches, thus minimizing space charge effects and enabling high bunch charge. Also, such guns should be suitable for experiments requiring high average current electron beams. A 112 MHz QWR gun was designed, fabricated, and cold-tested in collaboration between BNL and Niowave. This is the lowest frequency SRF gun ever tested successfully. In this paper we describe the gun design and fabrication, present the cold test results, and outline plans for the cryomodule upgrade for future experiments.

  17. Characterization of MgB2 Superconducting Hot Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  18. Magnetic and superconducting quantum critical behavior of itinerant electronic systems

    NASA Astrophysics Data System (ADS)

    Sknepnek, Rastko

    Quantum phase transitions occur at zero temperature as a function of some non-thermal parameter, e.g., pressure or chemical composition. In addition to being of fundamental interest, quantum phase transitions are important because they are believed to underlie a number of interesting low temperature phenomena. Quantum phase transitions differ from the classical phase transitions in many important aspects, two of them being (i) the mode-coupling effects and (ii) the behavior in the presence of disorder. We devote two projects of this dissertation to each of the two. First, we investigate the quantum phase transition of itinerant electrons from a paramagnet to a state which displays long-period helical structures due to a Dzyaloshinskii instability of the ferromagnetic state. In particular, we study how the self generated effective long-range interaction recently identified in itinerant quantum ferromagnets is cut-off by the helical ordering. Second, we discuss a quantum phase transition between a disordered metal and an exotic (non-s-wave) superconductor. Like in the case of ferromagnetic quantum phase transition mode coupling effects lead to an effective long-range interaction between the anomalous density fluctuations. We find that the asymptotic critical region is characterized by run-away flow to large disorder. However, for weak coupling, this region is very narrow, and it is preempted by a wide crossover regime with mean-field critical behavior. Then, we present results of large-scale Monte Carlo simulations for a 3d Ising model with short range interactions and planar defects. We show that the phase transition in this system is smeared, i.e., there is no single critical temperature, but different parts of the system order at different temperatures. Our Monte-Carlo results are in good agreement with a recent theory. Finally, we present large-scale Monte-Carlo simulations of a 2d bilayer quantum Heisenberg antiferromagnet with random dimer dilution. In contrast

  19. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics

    SciTech Connect

    Bak, J. G.; Lee, S. G.; Son, D.; Ga, E. M.

    2007-04-15

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  20. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics

    NASA Astrophysics Data System (ADS)

    Bak, J. G.; Lee, S. G.; Son, D.; Ga, E. M.

    2007-04-01

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  1. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics.

    PubMed

    Bak, J G; Lee, S G; Son, D; Ga, E M

    2007-04-01

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  2. Advanced Power Electronics and Electric Motors Annual Report -- 2013

    SciTech Connect

    Narumanchi, S.; Bennion, K.; DeVoto, D.; Moreno, G.; Rugh, J.; Waye, S.

    2015-01-01

    This report describes the research into advanced liquid cooling, integrated power module cooling, high temperature air cooled power electronics, two-phase cooling for power electronics, and electric motor thermal management by NREL's Power Electronics group in FY13.

  3. First results of 28 GHz superconducting electron cyclotron resonance ion source for KBSI accelerator

    SciTech Connect

    Park, Jin Yong; Lee, Byoung-Seob; Choi, Seyong; Kim, Seong Jun; Ok, Jung-Woo; Yoon, Jang-Hee; Kim, Hyun Gyu; Shin, Chang Seouk; Hong, Jonggi; Bahng, Jungbae; Won, Mi-Sook

    2016-02-15

    The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

  4. First results of 28 GHz superconducting electron cyclotron resonance ion source for KBSI accelerator

    NASA Astrophysics Data System (ADS)

    Park, Jin Yong; Lee, Byoung-Seob; Choi, Seyong; Kim, Seong Jun; Ok, Jung-Woo; Yoon, Jang-Hee; Kim, Hyun Gyu; Shin, Chang Seouk; Hong, Jonggi; Bahng, Jungbae; Won, Mi-Sook

    2016-02-01

    The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

  5. Magnetism, f-electron localization and superconductivity in 122-type heavy-fermion metals.

    PubMed

    Steglich, F; Arndt, J; Stockert, O; Friedemann, S; Brando, M; Klingner, C; Krellner, C; Geibel, C; Wirth, S; Kirchner, S; Si, Q

    2012-07-25

    Both CeCu2Si2 and YbRh2Si2 crystallize in the tetragonal ThCr2Si2 crystal structure. Recent neutron-scattering results on normal-state CeCu2Si2 reveal a slowing down of the quasielastic response which complies with the scaling expected for a quantum critical point (QCP) of itinerant, i.e., three-dimensional spin-density-wave (SDW), type. This interpretation is in full agreement with the non-Fermi-liquid behavior observed in transport and thermodynamic measurements. The momentum dependence of the magnetic excitation spectrum reveals two branches of an overdamped dispersive mode whose coupling to the heavy charge carriers is strongly retarded. These overdamped spin fluctuations are considered to be the driving force for superconductivity in CeCu2Si2 (Tc = 600 mK). The weak antiferromagnet YbRh2Si2 (TN = 70 mK) exhibits a magnetic-field-induced QCP at BN = 0.06 T (B⊥c). There is no indication of superconductivity down to T = 10 mK. The magnetic QCP appears to concur with a breakdown of the Kondo effect. Doping-induced variations of the average unit-cell volume result in a detachment of the magnetic and electronic instabilities. A comparison of the properties of these isostructural compounds suggests that 3D SDW QCPs are favorable for unconventional superconductivity. The question whether a Kondo-breakdown QCP may also give rise to superconductivity, however, remains to be clarified.

  6. Superconductivity on the verge of electronic topological transition in Fe based superconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Haranath; Sen, Smritijit

    2017-04-01

    A comprehensive first principles study on the electronic topological transition in a number of 122 family of Fe based superconductors is presented. Doping as well as temperature driven Lifshitz transitions are predicted from ab-initio simulations in a variety of Fe based superconductors that are consistent with experimental findings. In all the studied compounds the Lifshitz transitions are consistently found to take place at a doping concentration just around where superconductivity is known to acquire the highest Tc and magnetism disappears. This indicates the intriguing heed to the inter-relationship between superconductivity and Lifshitz transition in Fe-based 122 materials. Systematically, the Lifshitz transition occurs (above certain threshold doping) in some of the electronic Fermi surfaces for hole doped 122 compounds, whereas in hole Fermi surfaces for electron as well as iso-electronic doped 122 compounds. Temperature driven Lifshitz transition is found to occur in the iso-electronic Ru-doped BaFe2As2 compounds. A systematic study of Fermi surface area e.g., variations of (i) areas of each individual Fermi surfaces, (ii) sum total areas of all the electron Fermi Surfaces, (iii) sum total areas of all the hole Fermi Surfaces, (iv) sum total areas of all the five Fermi Surfaces, (v) difference of all hole and all electron Fermi surface areas as a function of doping is a rare wealth of information that can be verified by the de Haas-van Alphen and allied effects (i.e. , Shubnikov-de Haas effect) are presented. Fermi surface area are found to carry sensitivity of topological modifications more acutely than the band structures and can be used as a better experimental tool to identify ETT/LT.

  7. First Demonstration of Electron Beam Generation and Characterization with an All Superconducting Radio-frequency (SRF) Photoinjector

    SciTech Connect

    Kamps, T; Barday, R; Jankowiak, A; Knobloch, J; Kugeler, O; Matveenko, A N; Neumann, A; Quast, T; Rudolph, J; Schubert, S G; Volker, J; Kneisel, P; Nietubyc, R; Sekutowicz, J K; Smedley, J; Volkov, V; Weinberg, G; Will, I

    2011-09-01

    In preparation for a high brightness, high average current electron source for the energy-recovery linac BERLinPro an all superconducting radio-frequency photoinjector is now in operation at Helmholtz-Zentrum Berlin. The aim of this experiment is beam demonstration with a high brightness electron source able to generate sub-ps pulse length electron bunches from a superconducting (SC) cathode film made of Pb coated on the backwall of a Nb SRF cavity. This paper describes the setup of the experiment and first results from beam measurements.

  8. Production of a highly charged uranium ion beam with RIKEN superconducting electron cyclotron resonance ion source

    SciTech Connect

    Higurashi, Y.; Ohnishi, J.; Nakagawa, T.; Haba, H.; Fujimaki, M.; Komiyama, M.; Kamigaito, O.; Tamura, M.; Aihara, T.; Uchiyama, A.

    2012-02-15

    A highly charged uranium (U) ion beam is produced from the RIKEN superconducting electron cyclotron resonance ion source using 18 and 28 GHz microwaves. The sputtering method is used to produce this U ion beam. The beam intensity is strongly dependent on the rod position and sputtering voltage. We observe that the emittance of U{sup 35+} for 28 GHz microwaves is almost the same as that for 18 GHz microwaves. It seems that the beam intensity of U ions produced using 28 GHz microwaves is higher than that produced using 18 GHz microwaves at the same Radio Frequency (RF) power.

  9. The third generation superconducting 28 GHz electron cyclotron resonance ion source VENUS (invited)

    SciTech Connect

    Lyneis, C.; Leitner, D.; Leitner, M.; Taylor, C.; Abbott, S.

    2010-02-15

    VENUS is a third generation electron cyclotron resonance (ECR) ion source, which incorporates a high field superconducting NbTi magnet structure, a 28 GHz gryotron microwave source and a state of the art closed cycle cryosystem. During the decade from initial concept to regular operation, it has demonstrated both the feasibility and the performance levels of this new generation of ECR ion sources and required innovation on magnet construction, plasma chamber design, and beam transport. In this paper, the development, performance, and major innovations are described as well as a look to the potential to construct a fourth generation ECR ion source.

  10. Simulation and beamline experiments for the superconducting electron cyclotron resonance ion source VENUS

    SciTech Connect

    Todd, Damon S.; Leitner, Daniela; Lyneis, Claude M.; Grote, David P.

    2008-02-15

    The particle-in-cell code WARP has been enhanced to incorporate both two- and three-dimensional sheath extraction models giving WARP the capability of simulating entire ion beam transport systems including the extraction of beams from plasma sources. In this article, we describe a method of producing initial ion distributions for plasma extraction simulations in electron cyclotron resonance (ECR) ion sources based on experimentally measured sputtering on the source biased disk. Using this initialization method, we present preliminary results for extraction and transport simulations of an oxygen beam and compare them with experimental beam imaging on a quartz viewing plate for the superconducting ECR ion source VENUS.

  11. Development of an 18 GHz superconducting electron cyclotron resonance ion source at RCNP.

    PubMed

    Yorita, Tetsuhiko; Hatanaka, Kichiji; Fukuda, Mitsuhiro; Kibayashi, Mitsuru; Morinobu, Shunpei; Okamura, Hiroyuki; Tamii, Atsushi

    2008-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source has recently been developed and installed in order to extend the variety and the intensity of ions at the RCNP coupled cyclotron facility. Production of several ions such as O, N, Ar, Kr, etc., is now under development and some of them have already been used for user experiments. For example, highly charged heavy ion beams like (86)Kr(21+,23+) and intense (16)O(5+,6+) and (15)N(6+) ion beams have been provided for experiments. The metal ion from volatile compounds method for boron ions has been developed as well.

  12. The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier

    SciTech Connect

    J.G. Kulpin, K.J. Kleman, R.A. Legg

    2012-07-01

    A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

  13. Orthogonal sequencing multiplexer for superconducting nanowire single-photon detectors with RSFQ electronics readout circuit.

    PubMed

    Hofherr, Matthias; Wetzstein, Olaf; Engert, Sonja; Ortlepp, Thomas; Berg, Benjamin; Ilin, Konstantin; Henrich, Dagmar; Stolz, Ronny; Toepfer, Hannes; Meyer, Hans-Georg; Siegel, Michael

    2012-12-17

    We propose an efficient multiplexing technique for superconducting nanowire single-photon detectors based on an orthogonal detector bias switching method enabling the extraction of the average count rate of a set of detectors by one readout line. We implemented a system prototype where the SNSPDs are connected to an integrated cryogenic readout and a pulse merger system based on rapid single flux quantum (RSFQ) electronics. We discuss the general scalability of this concept, analyze the environmental requirements which define the resolvability and the accuracy and demonstrate the feasibility of this approach with experimental results for a SNSPD array with four pixels.

  14. kz Dependent Electronic Structure Studies of CaC6 and Inter Layer State Driven Superconductivity

    NASA Astrophysics Data System (ADS)

    Kyung, Wonshik; Kim, Yeongkwan; Han, Garam; Leem, Choonshik; Kim, Chul; Koh, Yoonyoung; Kim, Beomyoung; Kim, Yeongwook; Kim, Junsung; Kim, Keunsu; Rotenberg, Eli; Denlinger, Jonathan; Kim, Changyoung; Yonsei University Team; Postech Collaboration; Advanced light source Collaboration

    2015-03-01

    We performed angle-resolved photoemission experiments on CaC6 and measured kz dependent electronic structures to investigate the interlayer states. The results reveal a spherical interlayer Fermi surface centered at the Γ point. We also find the graphene driven band possesses a weak kz dispersion. The overall electronic structure shows a peculiar single graphene layer periodicity in the kz direction although CaC6 unit cell is supposed to contain three graphene layers. This suggests that c-axis ordering of Ca has little effect on the electronic structure of CaC6. In addition to CaC6, we also studied the non-superconducting BaC6. For BaC6, the graphene band Dirac point energy is smaller than that of CaC6. Based on data from CaC6 and BaC6, we rule out Cxy phonon mode as the origin of the superconductivity in CaC6, which strongly suggests interlayer state driven supercondutivity.

  15. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    SciTech Connect

    Schwarz, S. Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-15

    The Electron Beam Ion Trap (EBIT) in NSCL’s reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT’s superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm{sup 2} has been reached when the EBIT magnet was operated at 4 T.

  16. Spatial Complexity Due to Bulk Electronic Liquid Crystals in Superconducting Dy-Bi2212

    NASA Astrophysics Data System (ADS)

    Carlson, Erica; Phillabaum, Benjamin; Dahmen, Karin

    2012-02-01

    Surface probes such as scanning tunneling microscopy (STM) have detected complex electronic patterns at the nanoscale in many high temperature superconductors. In cuprates, the pattern formation is associated with the pseudogap phase, a precursor to the high temperature superconducting state. Rotational symmetry breaking of the host crystal (i.e. from C4 to C2) in the form of electronic nematicity has recently been proposed as a unifying theme of the pseudogap phase [Lawler Nature 2010]. However, the fundamental physics governing the nanoscale pattern formation has not yet been identified. Here we use universal cluster properties extracted from STM studies of cuprate superconductors to identify the funda- mental physics controlling the complex pattern formation. We find that due to a delicate balance between disorder, interactions, and material anisotropy, the rotational symmetry breaking is fractal in nature, and that the electronic liquid crystal extends throughout the bulk of the material.

  17. An Electron Bunch Compression Scheme for a Superconducting Radio Frequency Linear Accelerator Driven Light Source

    SciTech Connect

    C. Tennant, S.V. Benson, D. Douglas, P. Evtushenko, R.A. Legg

    2011-09-01

    We describe an electron bunch compression scheme suitable for use in a light source driven by a superconducting radio frequency (SRF) linac. The key feature is the use of a recirculating linac to perform the initial bunch compression. Phasing of the second pass beam through the linac is chosen to de-chirp the electron bunch prior to acceleration to the final energy in an SRF linac ('afterburner'). The final bunch compression is then done at maximum energy. This scheme has the potential to circumvent some of the most technically challenging aspects of current longitudinal matches; namely transporting a fully compressed, high peak current electron bunch through an extended SRF environment, the need for a RF harmonic linearizer and the need for a laser heater. Additional benefits include a substantial savings in capital and operational costs by efficiently using the available SRF gradient.

  18. Design of a single-channel millimeter-wave interferometer system for Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Nam, Y. U.; Cheon, M. S.; Kwon, M.; Hwang, Y. S.

    2003-03-01

    A simple single-channel horizontal millimeter-wave interferometer has been designed for plasma electron density measurements on the Korea Superconducting Tokamak Advanced Research (KSTAR). To measure line integrated plasma densities of 2×1019 m-2 in the initial phase of the KSTAR, Gunn oscillator frequency of 280 GHz has been chosen to optimize errors due to both vibration on the beam path and refraction in the plasma. To reduce the free propagation length of the probing beam and to obtain small beam width on the vacuum windows, a retractable cassette system for deep positioning of the diagnostic system has been designed, where microwave parts are located as close as possible to the tokamak with a shielding box. A beam focusing system with concave reflecting mirrors has been designed on the cassette and on the inner wall of the tokamak to reduce beam losses and to minimize beam width in the plasma. The estimated total transmission loss is about 25 dB, and beam widths are reduced significantly in the range of 20-50 mm.

  19. Studies of challenge in lower hybrid current drive capability at high density regime in experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, M. H.; Li, Y. C.; Wang, M.; Liu, F. K.; Shan, J. F.; Li, J. G.; Wan, B. N.; Wan

    2017-02-01

    Aiming at a fusion reactor, two issues must be solved for the lower hybrid current drive (LHCD), namely good lower hybrid wave (LHW)-plasma coupling and effective current drive at high density. For this goal, efforts have been made to improve LHW-plasma coupling and current drive capability at high density in experimental advanced superconducting tokamak (EAST). LHW-plasma coupling is improved by means of local gas puffing and gas puffing from the electron side is taken as a routine way for EAST to operate with LHCD. Studies of high density experiments suggest that low recycling and high lower hybrid (LH) frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. With the combination of 2.45 GHz and 4.6 GHz LH waves, a repeatable high confinement mode plasma with maximum density up to 19~\\text{m}-3$ was obtained by LHCD in EAST. In addition, in the first stage of LHCD cyclic operation, an alternative candidate for more economical fusion reactors has been demonstrated in EAST and further work will be continued.

  20. First-principles study of the electronic structure of iron-selenium: Implications for electron-phonon superconductivity

    NASA Astrophysics Data System (ADS)

    Koufos, Alexander P.; Papaconstantopoulos, Dimitrios A.; Mehl, Michael J.

    2014-01-01

    We have performed density functional theory calculations using the linearized augmented plane wave method (LAPW) with the local density approximation (LDA) functional to study the electronic structure of the iron-based superconductor iron-selenium (FeSe). In our study, we have performed a comprehensive set of calculations involving structural, atomic, and spin configurations. All calculations were executed using the tetragonal lead-oxide or P4/nmm structure, with various volumes, c /a ratios, and internal parameters. Furthermore, we investigated the spin polarization using the LDA functional to assess ferromagnetism in this material. The paramagnetic LDA calculations find the equilibrium configuration of FeSe in the P4/nmm structure to have a volume of 472.5 a.u.3 with a c /a ratio of 1.50 and internal parameter of 0.255, with the ferromagnetic having comparable results to the paramagnetic case. In addition, we calculated total energies for FeSe using a pseudopotential method, and found comparable results to the LAPW calculations. Superconductivity calculations were done using the Gaspari-Gyorffy and the McMillan formalisms and found substantial electron-phonon coupling. Under pressure, our calculations show that the superconductivity critical temperature continues to rise, but underestimates the measured values.

  1. Superconducting magnet performance for 28 GHz electron cyclotron resonance ion source developed at the Korea Basic Science Institute

    SciTech Connect

    Park, Jin Yong; Choi, Seyong; Lee, Byoung-Seob; Yoon, Jang-Hee; Ok, Jung-Woo; Shin, Chang Seouk; Won, Mi-Sook; Kim, Byoung Chul; Ahn, Jung Keun

    2014-02-15

    A superconducting magnet for use in an electron cyclotron resonance ion source was developed at the Korea Basic Science Institute. The superconducting magnet is comprised of three solenoids and a hexapole magnet. According to the design value, the solenoid magnets can generate a mirror field, resulting in axial magnetic fields of 3.6 T at the injection area and 2.2 T at the extraction region. A radial field strength of 2.1 T can also be achieved by hexapole magnet on the plasma chamber wall. NbTi superconducting wire was used in the winding process following appropriate techniques for magnet structure. The final assembly of the each magnet involved it being vertically inserted into the cryostat to cool down the temperature using liquid helium. The performance of each solenoid and hexapole magnet was separately verified experimentally. The construction of the superconducting coil, the entire magnet assembly for performance testing and experimental results are reported herein.

  2. Advanced Electronic Systems. Curriculum Guide for Technology Education.

    ERIC Educational Resources Information Center

    Patrick, Dale R.

    This curriculum for a 1-semester or 1-year course in electronics is designed to take students from basic through advanced electronic systems. It covers several electronic areas, such as digital electronics, communication electronics, industrial process control, instrumentation, programmable controllers, and robotics. The guide contains…

  3. Electronic materials high-T(sub c) superconductivity polymers and composites structural materials surface science and catalysts industry participation

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The fifth year of the Center for Advanced Materials was marked primarily by the significant scientific accomplishments of the research programs. The Electronics Materials program continued its work on the growth and characterization of gallium arsenide crystals, and the development of theories to understand the nature and distribution of defects in the crystals. The High Tc Superconductivity Program continued to make significant contributions to the field in theoretical and experimental work on both bulk materials and thin films and devices. The Ceramic Processing group developed a new technique for cladding YBCO superconductors for high current applications in work with the Electric Power Research Institute. The Polymers and Composites program published a number of important studies involving atomistic simulations of polymer surfaces with excellent correlations to experimental results. The new Enzymatic Synthesis of Materials project produced its first fluorinated polymers and successfully began engineering enzymes designed for materials synthesis. The structural Materials Program continued work on novel alloys, development of processing methods for advanced ceramics, and characterization of mechanical properties of these materials, including the newly documented characterization of cyclic fatigue crack propagation behavior in toughened ceramics. Finally, the Surface Science and Catalysis program made significant contributions to the understanding of microporous catalysts and the nature of surface structures and interface compounds.

  4. Coupling an Ensemble of Electrons on Superfluid Helium to a Superconducting Circuit

    NASA Astrophysics Data System (ADS)

    Yang, Ge; Fragner, A.; Koolstra, G.; Ocola, L.; Czaplewski, D. A.; Schoelkopf, R. J.; Schuster, D. I.

    2016-01-01

    The quantized lateral motional states and the spin states of electrons trapped on the surface of superfluid helium have been proposed as basic building blocks of a scalable quantum computer. Circuit quantum electrodynamics allows strong dipole coupling between electrons and a high-Q superconducting microwave resonator, enabling such sensitive detection and manipulation of electron degrees of freedom. Here, we present the first realization of a hybrid circuit in which a large number of electrons are trapped on the surface of superfluid helium inside a coplanar waveguide resonator. The high finesse of the resonator allows us to observe large dispersive shifts that are many times the linewidth and make fast and sensitive measurements on the collective vibrational modes of the electron ensemble, as well as the superfluid helium film underneath. Furthermore, a large ensemble coupling is observed in the dispersive regime during experiment, and it shows excellent agreement with our numeric model. The coupling strength of the ensemble to the cavity is found to be ≈1 MHz per electron, indicating the feasibility of achieving single electron strong coupling.

  5. Drag coupling between Al thin films and two-dimensional electron gases near the superconducting transition

    NASA Astrophysics Data System (ADS)

    Farina, L. A.; Lewis, K. M.; Kurdak, C.; Ghosh, S.; Krishna, S.; Bhattacharya, P.

    2003-03-01

    We studied the coupling between vortices in a superconducting film and electrons in a two-dimensional electron gas (2DEG). We measured structures consisting of a thin Al film evaporated on a GaAs/AlGaAs heterostructure containing a 2DEG patterned in a 1mmx4μm Hall bar structure. This structure allowed us to vary the carrier density of the 2DEG in situ, by applying a voltage with respect to the Al. We looked for evidence of interaction by passing a current through the Al film and measuring the drag voltage induced in the 2DEG, near the superconducting transition temperature. Al films with sheet resistances of 20 Ω and 1 k Ω, located 650 Åand 1000 Åabove the 2DEG, respectively, were measured. The initial results indicate no drag resistance measured down to the 10nV range with 10nA-250 μA drive currents, for various 2DEG carrier densities. The opposite configuration was also measured, and showed no drag voltage. The theoretical implications of these results will be discussed. *current address: Center for High Technology Materials, Electrical and Computer Engineering Dept., Albuquerque, NM, 87106

  6. Interface Electronic Structure and Possible Superconductivity in CuCl/Si(111)

    NASA Astrophysics Data System (ADS)

    Rhim, S. H.; Yu, J.

    2005-03-01

    To investigate a possible interfacial superconductivity ootnotetextB.L. Mattes, Physica C 162,554 (1989); B.L. Mattes and C. L. Foiles, Physica 135B, 139 (1985) in CuCl/Si(111), we carried out electronic structure calculations using the highly precise FLAPW ootnotetextWimmer, Krakauer, Weinert, and Freeman, Phys.Rev.B, 24, 864 (1981) method. As a result of charge transfer between CuCl and Si layers, two-dimensional (2D) metallic states are found to be formed at the interface. From the geometry relaxation, it is shown that the ionic bonding of CuCl is weakened and there is mixed metallic and covalent bonding at the interface. The 2D conduction bands at the interface, sandwiched by the highly polarizable dielectric layers, resemble the 2D Cu-O dpσ bands of the Cu-oxide superconductors, which are considered to be responsible for high Tc superconductivity. To obtain Tc of the CuCl/Si interface based on the conventional electron-phonon(e-p) interactions, we calculated the e-p coupling constant, λ, within the rigid ion approximation ootnotetextG. D. Gaspari and B. L. Gyorffy, Phys. Rev. Lett. 28 801 (1972). The results indicate that a strong e-p coupling is present at the interface layers but is not enough to explain the previously reported high transition temperature^2.

  7. Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaobo; Saito, Shiro; Kemp, Alexander; Kakuyanagi, Kosuke; Karimoto, Shin-Ichi; Nakano, Hayato; Munro, William J.; Tokura, Yasuhiro; Everitt, Mark S.; Nemoto, Kae; Kasu, Makoto; Mizuochi, Norikazu; Semba, Kouichi

    2012-02-01

    We have experimentally demonstrated coherent strong coupling between a single macroscopic superconducting artificial atom (a gap tunable flux qubit [1]) and an ensemble of electron spins in the form of nitrogen--vacancy color centres in diamond. We have observed coherent exchange of a single quantum of energy between a flux qubit and a macroscopic ensemble consisting of about 3.0*10^7 NV- centers [2]. This is the first step towards the realization of a long-lived quantum memory and hybrid devices coupling microwave and optical systems. [1] Coherent operation of a gap-tunable flux qubit X. B. Zhu, A. Kemp, S. Saito, K. Semba, APPLIED PHYSICS LETTERS, Volume: 97, Issue: 10 pp. 102503 (2010) [2] Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond Xiaobo Zhu, Shiro Saito, Alexander Kemp, Kosuke Kakuyanagi, Shin-ichi Karimoto, Hayato Nakano, William J. Munro, Yasuhiro Tokura, Mark S. Everitt, Kae Nemoto, Makoto Kasu, Norikazu Mizuochi, and Kouichi Semba, Nature, Volume: 478, 221-224 (2011)

  8. Break the electron- hole balance and pressure induced superconductivity in Tungsten Ditelluride

    NASA Astrophysics Data System (ADS)

    Song, Fengqi; Pan, Xing-Chen

    Tungsten ditelluride has garnered immense interest due to the recent discovery of titanic unsaturated magnetoresistance up to 60 Tesla and its possible topological metal nature. The titanic unsaturated magnetoresistance is attributed to the perfect compensation between the opposite carriers in this material. Motivated by the small and sensitive Fermi surface of 5d electronic orbitals, we break the electron-hole balance by the application of high pressure. Superconductivity sharply appears at the pressure of 2.5 GPa, quickly reaching a maximum critical temperature of 7 K at around 16.8 GPa, and followed by a monotonic decrease in Tc with increasing pressure exhibiting the typical dome-shaped superconducting phase. What's more, linear magnetoresistance dominates the transport behavior under high pressure instead of semi-classical parabolic magnetoresistance, like in other topological metals. Refence: Nature Commun. 6, 7805 (2015), arXiv 1505, 07968. The authors would like to thank the National Key Projects for Basic Research in China, the National Natural Science Foundation of China , the NSF of Jiangsu Province, the PAPD project, and the Fundamental Research Funds for the Central Universities.

  9. Continuous wave superconducting radio frequency electron linac for nuclear physics research

    NASA Astrophysics Data System (ADS)

    Reece, Charles E.

    2016-12-01

    CEBAF, the Continuous Electron Beam Accelerator Facility, has been actively serving the nuclear physics research community as a unique forefront international resource since 1995. This cw electron linear accelerator (linac) at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility (Jefferson Lab) has continued to evolve as a precision tool for discerning the structure and dynamics within nuclei. Superconducting rf (SRF) technology has been the essential foundation for CEBAF, first as a 4 GeV machine, then 6 GeV, and currently capable of 12 GeV. We review the development, implementation, and performance of SRF systems for CEBAF from its early beginnings to the commissioning of the 12 GeV era.

  10. Results of RIKEN superconducting electron cyclotron resonance ion source with 28 GHz.

    PubMed

    Higurashi, Y; Ohnishi, J; Nakagawa, T; Haba, H; Tamura, M; Aihara, T; Fujimaki, M; Komiyama, M; Uchiyama, A; Kamigaito, O

    2012-02-01

    We measured the beam intensity of highly charged heavy ions and x-ray heat load for RIKEN superconducting electron cyclotron resonance ion source with 28 GHz microwaves under the various conditions. The beam intensity of Xe(20+) became maximum at B(min) ∼ 0.65 T, which was ∼65% of the magnetic field strength of electron cyclotron resonance (B(ECR)) for 28 GHz microwaves. We observed that the heat load of x-ray increased with decreasing gas pressure and field gradient at resonance zone. It seems that the beam intensity of highly charged heavy ions with 28 GHz is higher than that with 18 GHz at same RF power.

  11. Generation and measurement of ultrashort pulses from the Stanford Superconducting Accelerator free-electron laser

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-11-01

    The authors present results of frequency resolved optical gating (FROG) measurements on the Superconducting Accelerator (SCA) mid-IR free-electron laser (FEL) at Stanford. FROG retrieves complete amplitude and phase content of an optical pulse. First, they review the properties of FELs including the ability to tune wavelength and pulse length. In addition, the electron beam driving the FEL often affects the optical pulse shape. The SCA mid-IR FEL currently operates at wavelengths between 4 {micro}m and 10 {micro}m and its pulse length can be varied from 700 fs to 2 ps. They then describe details of the experimental layout and procedures particular to FELs and to the mid-IR. Finally, they show FROG measurements on the FEL including examples of nearly transform limited pulses, frequency chirped pulses, and pulses distorted by atmospheric water vapor absorption.

  12. Comparison between hot spot modeling and measurement of a superconducting hot electron bolometer mixer at submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Miao, Wei; Delorme, Yan; Feret, Alexandre; Lefevre, Rolland; Lecomte, Benoit; Dauplay, Fred; Krieg, Jean-Michel; Beaudin, Gerard; Zhang, Wen; Ren, Yuan; Shi, Sheng-Cai

    2009-11-01

    This paper presents the modeling and measurement of a quasioptical niobium nitride superconducting hot electron bolometer mixer at submillimeter wavelengths. The modeling is performed with a distributed hot spot model which is based on solving a heat balance equation for electron temperature along the superconducting microbridge. Particular care has been taken during the modeling concerning the temperature-dependent resistance and the bias current dependence of the critical temperature of the device. The dc and mixing characteristics of this mixer have been computed and we have observed a quite good match between the predicted and the measured results for both dc characteristics and mixing performances at submillimeter wavelengths.

  13. EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions

    NASA Astrophysics Data System (ADS)

    Poncé, S.; Margine, E. R.; Verdi, C.; Giustino, F.

    2016-12-01

    The EPW (Electron-Phonon coupling using Wannier functions) software is a Fortran90 code that uses density-functional perturbation theory and maximally localized Wannier functions for computing electron-phonon couplings and related properties in solids accurately and efficiently. The EPW v4 program can be used to compute electron and phonon self-energies, linewidths, electron-phonon scattering rates, electron-phonon coupling strengths, transport spectral functions, electronic velocities, resistivity, anisotropic superconducting gaps and spectral functions within the Migdal-Eliashberg theory. The code now supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric crystals, polar materials, and k and q-point parallelization. Considerable effort was dedicated to optimization and parallelization, achieving almost a ten times speedup with respect to previous releases. A computer test farm was implemented to ensure stability and portability of the code on the most popular compilers and architectures. Since April 2016, version 4 of the EPW code is fully integrated in and distributed with the Quantum ESPRESSO package, and can be downloaded through QE-forge at http://qe-forge.org/gf/project/q-e.

  14. Advanced electron microscopy characterization of multimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna Raj

    Research in noble metal nanoparticles has led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: PtPd, Au-Au3Cu, Cu-Pt, AgPd/Pt and AuCu/Pt nanoparticles. The objective of this work is to understand the physical and chemical properties of nanomaterials and describe synthesis, characterization, surface properties and growth mechanism of various bimetallic and multimetallic nanoparticles. The findings have provided us with novel and significant insights into the physical and chemical properties of noble metal nanoparticles. Different synthesis routes allowed us to synthesize bimetallic: Pt-Pd, Au-Au3Cu, Cu-Pt and trimetallic: AgPd/Pt, AuCu/Pt, core-shell and alloyed nanoparticles with monodispersed sizes, controlled shapes and tunable surface properties. For example, we have synthesized the polyhedral PtPd core-shell nanoparticles with octahedral, decahedral, and triangular plates. Decahedral PtPd core-shell structures are novel morphologies for this system. For the first time we fabricated that the Au core and Au3Cu alloyed shell nanoparticles passivated with CuS2 surface layers and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu ordered superlattice alloyed shell surrounded by CuS 2 surface layer. Additionally, we have described both experimental and theoretical methods of

  15. Simulations of the L-H transition on experimental advanced superconducting Tokamak

    SciTech Connect

    Weiland, Jan

    2014-12-15

    We have simulated the L-H transition on the EAST tokamak [Baonian Wan, EAST and HT-7 Teams, and International Collaborators, “Recent experiments in the EAST and HT-7 superconducting tokamaks,” Nucl. Fusion 49, 104011 (2009)] using a predictive transport code where ion and electron temperatures, electron density, and poloidal and toroidal momenta are simulated self consistently. This is, as far as we know, the first theory based simulation of an L-H transition including the whole radius and not making any assumptions about where the barrier should be formed. Another remarkable feature is that we get H-mode gradients in agreement with the α – α{sub d} diagram of Rogers et al. [Phys. Rev. Lett. 81, 4396 (1998)]. Then, the feedback loop emerging from the simulations means that the L-H power threshold increases with the temperature at the separatrix. This is a main feature of the C-mod experiments [Hubbard et al., Phys. Plasmas 14, 056109 (2007)]. This is also why the power threshold depends on the direction of the grad B drift in the scrape off layer and also why the power threshold increases with the magnetic field. A further significant general H-mode feature is that the density is much flatter in H-mode than in L-mode.

  16. Multiband superconductivity in the correlated electron filled skutterudite system Pr1-xCexPt4Ge12

    NASA Astrophysics Data System (ADS)

    Singh, Y. P.; Adhikari, R. B.; Zhang, S.; Huang, K.; Yazici, D.; Jeon, I.; Maple, M. B.; Dzero, M.; Almasan, C. C.

    2016-10-01

    Studies of superconductivity in multiband correlated electronic systems have become one of the central topics in condensed-matter and materials physics. In this paper, we present the results of thermodynamic measurements on the superconducting filled skutterudite system Pr1 -xCexPt4Ge12 (0 ≤x ≤0.2 ) to investigate how substitution of Ce at Pr sites affects superconductivity. We find that an increase in Ce concentration leads to a suppression of the superconducting transition temperature from Tc˜7.9 K for x =0 to Tc˜0.6 K for x =0.14 . Our analysis of the specific-heat data for x ≤0.07 reveals that superconductivity must develop in at least two bands: the superconducting order parameter has nodes on one Fermi pocket and remains fully gapped on the other. Both the nodal and nodeless gaps decrease, with the nodal gap being suppressed more strongly upon Ce substitution. Ultimately, the higher-Ce-concentration samples (x >0.07 ) display a nodeless gap only.

  17. A DFT study of electron-phonon mediated superconductivity in doped Mott-Hubbard proxy cubic-tetragonal copper monoxide

    NASA Astrophysics Data System (ADS)

    Grant, Paul

    We report our preliminary study of electron-phonon mediated Cooper pairing as a component underlying high temperature superconductivity, in the presence of a Hubbard U driven antiferromagnetic ground state, subject to itinerant carrier doping, in the copper oxide perovskites. Our model is based on a proxy CuO fcc cubic-tetragonal structure that contains the basic physics of the electronic structure of copper oxide perovskites readily amenable to numerical analysis. We explore its phase diagram as a function of carrier concentration and coulomb repulsion ranging from the pure Mott-Hubbard AF insulating state to that of a metallic Fermi liquid, focusing on those conditions which might manifest high temperature superconducting behavior. In the Fermi liquid state, we find clear evidence that superconductivity arises from Jahn-Teller instabilities in the CuO bond which guided Bednorz and Mueller on the path to their 1986 discovery.

  18. Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique

    NASA Astrophysics Data System (ADS)

    Portesi, C.; Borini, S.; Amato, G.; Monticone, E.

    2006-03-01

    In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.

  19. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Ren, J.; Zuo, G. Z.; Hu, J. S.; Sun, Z.; Yang, Q. X.; Li, J. G.; Zakharov, L. E.; Xie, H.; Chen, Z. X.

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak—both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  20. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Lampert, M.; Anda, G.; Réfy, D.; Zoletnik, S.; Czopf, A.; Erdei, G.; Guszejnov, D.; Kovácsik, Á.; Pokol, G. I.; Nam, Y. U.

    2015-07-15

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera’s measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  1. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  2. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    NASA Astrophysics Data System (ADS)

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun; Hu, Liqun; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-01

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey-predator model was found to reproduce the fishbone nonlinear process well.

  3. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    SciTech Connect

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun E-mail: lqhu@ipp.cas.cn; Hu, Liqun E-mail: lqhu@ipp.cas.cn; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-15

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey–predator model was found to reproduce the fishbone nonlinear process well.

  4. New Steady-State Quiescent High-Confinement Plasma in an Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Hu, J. S.; Sun, Z.; Guo, H. Y.; Li, J. G.; Wan, B. N.; Wang, H. Q.; Ding, S. Y.; Xu, G. S.; Liang, Y. F.; Mansfield, D. K.; Maingi, R.; Zou, X. L.; Wang, L.; Ren, J.; Zuo, G. Z.; Zhang, L.; Duan, Y. M.; Shi, T. H.; Hu, L. Q.; East Team

    2015-02-01

    A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H -mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.

  5. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak.

    PubMed

    Qu, H; Zhang, T; Han, X; Xiang, H M; Wen, F; Geng, K N; Wang, Y M; Kong, D F; Cai, J Q; Huang, C B; Gao, Y; Gao, X; Zhang, S

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  6. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lampert, M; Anda, G; Czopf, A; Erdei, G; Guszejnov, D; Kovácsik, Á; Pokol, G I; Réfy, D; Nam, Y U; Zoletnik, S

    2015-07-01

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera's measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  7. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Ren, J.; Zuo, G. Z.; Hu, J. S.; Sun, Z.; Yang, Q. X.; Li, J. G.; Xie, H.; Chen, Z. X.; Zakharov, L. E.

    2015-02-15

    A program involving the extensive and systematic use of lithium (Li) as a “first,” or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak—both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  8. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak.

    PubMed

    Ren, J; Zuo, G Z; Hu, J S; Sun, Z; Yang, Q X; Li, J G; Zakharov, L E; Xie, H; Chen, Z X

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak-both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  9. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Lampert, M.; Anda, G.; Czopf, A.; Erdei, G.; Guszejnov, D.; Kovácsik, Á.; Pokol, G. I.; Réfy, D.; Nam, Y. U.; Zoletnik, S.

    2015-07-01

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera's measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  10. Electronic, vibrational, superconducting and thermodynamic properties of cubic antiperovskite ZnNNi3

    NASA Astrophysics Data System (ADS)

    Tütüncü, H. M.; Srivastava, G. P.

    2013-12-01

    We present results of ab initio theoretical investigations of the structural and electronic properties of the cubic superconductor ZnNNi? by employing the plane wave pseudopotential method within the generalized gradient approximation. The density of states at the Fermi level is found to be governed by the Ni 3d electrons. A linear-response approach to the density functional theory is used to derive the phonon dispersion curves, vibrational density of states and the electron-phonon coupling parameter. The calculated electron-phonon coupling constant ? and the logarithmically averaged phonon frequency are calculated to be 0.654 and 169.89 K, respectively, giving the superconducting transition temperature T?=2.925 K according to the Allen-Dynes formula. Our calculated value of T? is in excellent accord with the corresponding experimental value of 3 K. Using the phonon dispersion results, we further present an assessment of important thermodynamical properties such as internal energy (E), Helmholtz free energy (F), constant-volume specific heat (C?), entropy (S) and Debye temperature (?) in the framework of quasi harmonic approximation theory.

  11. Commercial applications of electron beam advanced oxidation technology

    NASA Astrophysics Data System (ADS)

    Curry, Randy D.; Bosma, John T.

    1995-03-01

    Emerging commercial applications of electron-beam advanced oxidation technology offer a significant advancement in the treatment of waste steams. Both electron beam and X-ray (Brehmsstrahlung) advanced oxidation processes have been shown to be effective in the destruction of volatile and semivolatile organic compounds. Emerging commercial applications, however, far exceed in scope current applications of oxidation technologies for the destruction of simple semivolatile and volatile organic compounds in water. Emerging applications include direct treatment of contaminated soil, removal of metal ions from water and sterilization of water, sludges, and food. Application of electron beam advanced oxidation technologies are reviewed, along with electron- beam-generated X-ray (Brehmsstrahlung) advanced oxidation processes. Advantages of each technology are discussed along with advanced accelerator technologies which are applicable for commercial processing of waste streams. An overview of the U.S. companies and laboratories participating in this research area are included in this discussion.

  12. Electron Spin Resonance at the Level of 1 04 Spins Using Low Impedance Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Eichler, C.; Sigillito, A. J.; Lyon, S. A.; Petta, J. R.

    2017-01-01

    We report on electron spin resonance measurements of phosphorus donors localized in a 200 μ m2 area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low impedance microwave resonator design, we are able to detect around 2 ×1 04 spins with a signal-to-noise ratio of 1 in a single shot. The 150 Hz coupling strength between the resonator field and individual spins is significantly larger than the 1-10 Hz coupling rates obtained with typical coplanar waveguide resonator designs. Because of the larger coupling rate, we find that spin relaxation is dominated by radiative decay into the resonator and dependent upon the spin-resonator detuning, as predicted by Purcell.

  13. Appropriate microwave frequency selection for biasing superconducting hot electron bolometers as terahertz direct detectors

    NASA Astrophysics Data System (ADS)

    Jiang, S. L.; Li, X. F.; Jia, X. Q.; Kang, L.; Jin, B. B.; Xu, W. W.; Chen, J.; Wu, P. H.

    2017-04-01

    Terahertz (THz) direct detectors based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) and biased by a simple microwave (MW) source have been studied. The frequency and power of the MW are selected by measuring the MW responses of the current–voltage (I–V) curves and resistance–temperature (R–T) curves of the NbN HEBs. The non-uniform absorption theory is used to explain the current jumps in the I–V curves and the resistance jumps in the R–T curves. Compared to the thermal biasing, the MW biasing method can improve the sensitivity, make the readout system much easier and consumes less liquid helium, which is important for long lasting experiments. The noise equivalent power (NEP) of 1.6 pW Hz‑1/2 and the response time of 86 ps are obtained for the detectors working at 4.2 K and 0.65 THz.

  14. Ultrasensitive Superconducting Transition Edge Sensors Based On Electron-Phonon Decoupling

    NASA Technical Reports Server (NTRS)

    Jethava, Nikhil; Chervenak, James; Brown, Ari-David; Benford, Dominic; Kletetschka, Gunther; Mikula, Vilem; U-yen, Kongpop

    2011-01-01

    We have successfully fabricated the superconducting transition edge sensor (TES), bolometer technology that centers on the use of electron-phonon decoupling (EPD) to thermally isolate the bolometer. Along with material characterization for large format antenna coupled bolometer arrays, we present the initial test results of bolometer based on EPD designed for THz detection. We have selected a design approach that separates the two functions of photon absorption and temperature measurement, allowing separate optimization of the performance of each element. We have integrated Molybdenum/Gold (Mo/Au) bilayer TES and ion assisted thermally evaporated (IAE) Bismuth (Bi) films as radiation absorber coupled to a low-loss microstripline from Niobium (Nb) ground plane to a twin-slot antenna structure. The thermal conductance and the time constant of these devices have been measured, and are consistent with our calculations. The device exhibits a single time constant at 0.1 K of approx.160 IlS, which is compatible with readout by a high-bandwidth single SQUID or a time domain SQUID multiplexer. The effects of thermal conductance and electrothermal feedback are major determinants of the time constant, but the electronic heat capacity also plays a major role. The NEP achieved in the device described above is 2.5x10(exp -17)W(gamma)Hz. Our plan is to demonstrate a reduction of the volume in the superconducting element to 5 microns x 5 microns in films of half the thickness at Tc = 60mK. By calculation, this new geometry corresponds to an NEP reduction of two orders of magnitude to 2.5x10(exp -19)W/(gamma)Hz, with a time constant of 130/ls.

  15. Band- and momentum-dependent electron dynamics in superconducting Ba(Fe1-xCox)2As2 as seen via electronic Raman scattering

    SciTech Connect

    Muschler, B.

    2010-02-24

    We present details of carrier properties in high quality Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals obtained from electronic Raman scattering. The experiments indicate a strong band and momentum anisotropy of the electron dynamics above and below the superconducting transition highlighting the importance of complex band-dependent interactions. The presence of low energy spectral weight deep in the superconducting state suggests a gap with accidental nodes which may be lifted by doping and/or impurity scattering. When combined with other measurements, our observation of band and momentum dependent carrier dynamics indicate that the iron arsenides may have several competing superconducting ground states.

  16. Antenna-Coupled Superconducting Tunnel Junctions with Single-Electron Transistor Readout for Detection of Sub-mm Radiation

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Teufel, J.; Krebs, Carolyn (Technical Monitor)

    2002-01-01

    Antenna-coupled superconducting tunnel junction detectors have the potential for photon-counting sensitivity at sub-mm wavelengths. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  17. Emittance study of a 28 GHz electron cyclotron resonance ion source for the Rare Isotope Science Project superconducting linear accelerator

    SciTech Connect

    Park, Bum-Sik Hong, In-Seok; Jang, Ji-Ho; Jin, Hyunchang; Choi, Sukjin; Kim, Yonghwan

    2016-02-15

    A 28 GHz electron cyclotron resonance (ECR) ion source is being developed for use as an injector for the superconducting linear accelerator of the Rare Isotope Science Project. Beam extraction from the ECR ion source has been simulated using the KOBRA3-INP software. The simulation software can calculate charged particle trajectories in three dimensional complex magnetic field structures, which in this case are formed by the arrangement of five superconducting magnets. In this study, the beam emittance is simulated to understand the effects of plasma potential, mass-to-charge ratio, and spatial distribution. The results of these simulations and their comparison to experimental results are presented in this paper.

  18. Emittance study of a 28 GHz electron cyclotron resonance ion source for the Rare Isotope Science Project superconducting linear accelerator.

    PubMed

    Park, Bum-Sik; Hong, In-Seok; Jang, Ji-Ho; Jin, Hyunchang; Choi, Sukjin; Kim, Yonghwan

    2016-02-01

    A 28 GHz electron cyclotron resonance (ECR) ion source is being developed for use as an injector for the superconducting linear accelerator of the Rare Isotope Science Project. Beam extraction from the ECR ion source has been simulated using the KOBRA3-INP software. The simulation software can calculate charged particle trajectories in three dimensional complex magnetic field structures, which in this case are formed by the arrangement of five superconducting magnets. In this study, the beam emittance is simulated to understand the effects of plasma potential, mass-to-charge ratio, and spatial distribution. The results of these simulations and their comparison to experimental results are presented in this paper.

  19. Universal increase in the superconducting critical temperature of two-dimensional semiconductors at low doping by the electron-electron interaction.

    PubMed

    Calandra, Matteo; Zoccante, Paolo; Mauri, Francesco

    2015-02-20

    In two-dimensional multivalley semiconductors, at low doping, even a moderate electron-electron interaction enhances the response to any perturbation inducing a valley polarization. If the valley polarization is due to the electron-phonon coupling, the electron-electron interaction results in an enhancement of the superconducting critical temperature. By performing first-principles calculations beyond density functional theory, we prove that this effect accounts for the unconventional doping dependence of the superconducting transition temperature (T(c)) and of the magnetic susceptibility measured in Li(x)ZrNCI. Finally, we discuss what are the conditions for a maximal T(c) enhancement in weakly doped two-dimensional semiconductors.

  20. A high temperature superconductivity communications flight experiment

    NASA Technical Reports Server (NTRS)

    Ngo, P.; Krishen, K.; Arndt, D.; Raffoul, G.; Karasack, V.; Bhasin, K.; Leonard, R.

    1992-01-01

    The proposed high temperature superconductivity (HTSC) millimeter-wave communications flight experiment from the payload bay of the Space Shuttle Orbiter to the Advanced Communications Technology Satellite (ACTS) in geosynchronous orbit is described. The experiment will use a Ka-band HTSC phased array antenna and front-end electronics to receive a downlink communications signal from the ACTS. The discussion covers the system configuration, a description of the ground equipment, the spacecraft receiver, link performance, thermal loading, and the superconducting antenna array.

  1. Superconducting Cold-Electron Bolometers with JFET Readout for OLIMPO Balloon Telescope

    NASA Astrophysics Data System (ADS)

    Kuzmin, Leonid; Mauskopf, Phillip; Golubev, Dmitry

    2006-06-01

    The OLIMPO experiment is a 2.6 m balloon-borne telescope, aimed at measuring the Sunyaev- Zeldovich effect in clusters of Galaxies. OLIMPO will carry out surveys in four frequency bands centered at 140, 220, 410 and 540 GHz. The detector system consists of four bolometer arrays and incorporates new detector technologies that are potential candidates for future space missions. One of these technologies is the Capacitively Coupled Cold-Electron Bolometer (CEB) with JFET readout. The JFET readout coupled to semiconductor-based high-impedence bolometers has been developed already for the BOOMERanG and Planck-HFI experiments. The CEB is a planar antenna-coupled superconductong detector with high sensitivity and high dynamic range. Here, we discuss a scheme to match the relatively moderate dynamic resistance of CEB (~1kOhm) to the high noise equivalent resistance of JFET (1 MΩ). To achieve noise matching with JFET, a Cold-Electron Bolometer with a weak Superconducting Absorber (SCEB) has been proposed. In voltage-biased mode with voltage higher than (Delta 1-Delta 2) the IV of SIS' junctions has considerably increased dynamic resistance up to the level of Rj = 1000*Rn. Electron cooling will be still very effective for the incoming power. Simulations show that photon noise level can be achieved at 300 mK for a structure with Ti absorber and Al/Ti tunnel junctions for all frequency ranges with the estimated in-flight optical power load for OLIMPO.

  2. Electronic, vibrational, and superconducting properties of CaBeSi : First-principles calculations

    NASA Astrophysics Data System (ADS)

    Bersier, C.; Floris, A.; Sanna, A.; Profeta, G.; Continenza, A.; Gross, E. K. U.; Massidda, S.

    2009-03-01

    We report first-principles calculations on the normal and superconducting state of CaBexSi2-x (x=1) , in the framework of density-functional theory for superconductors. CaBeSi is isostructural and isoelectronic to MgB2 and this makes possible a direct comparison of the electronic and vibrational properties and the electron-phonon interaction of the two materials. Despite many similarities with MgB2 (e.g., σ and π bands at the Fermi level and an even larger density of states), according to our calculations CaBeSi has a very low critical temperature Tc≈0.4K consistent with the experiment. CaBeSi exhibits a complex gap structure, with three gaps at the Fermi level: besides the σ and π gaps (present also in MgB2 ), the appearance of a third gap is related to the anisotropy of the Coulomb repulsion, acting in different ways on the bonding and antibonding electronic π states.

  3. Electronic model for CoO2 layer based systems: chiral resonating valence bond metal and superconductivity.

    PubMed

    Baskaran, G

    2003-08-29

    Takada et al. have reported superconductivity in layered Na(x)CoO(2)yH(2)O (T(c) approximately equal to 5 K). We model a reference neutral CoO2 layer as an orbitally nondegenerate spin-1/2 antiferromagnetic Mott insulator on a triangular lattice and Na(x)CoO(2)yH(2)O as electron doped Mott insulators described by a t-J model. It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics lead to a gapful d-wave superconducting state. A chiral resonating valence bond (RVB) metal, a parity and time (PT) reversal violating state with condensed RVB gauge fields, with a possible weak ferromagnetism, and low temperature p-wave superconductivity are also suggested at higher dopings.

  4. Surface chemical deposition of advanced electronic materials

    NASA Astrophysics Data System (ADS)

    Bjelkevig, Cameron

    The focus of this work was to examine the direct plating of Cu on Ru diffusion barriers for use in interconnect technology and the substrate mediated growth of graphene on boron nitride for use in advanced electronic applications. The electrodeposition of Cu on Ru(0001) and polycrystalline substrates (with and without pretreatment in an iodine containing solution) has been studied by cyclic voltammetry (CV), current--time transient measurements (CTT), in situ electrochemical atomic force microscopy (EC-AFM), and X-ray photoelectron spectroscopy (XPS). The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. XPS measurements confirmed the presence and stability of adsorbed I on the Ru surface following pre-treatment in a KI/H2SO4 solution and following polarization to at least -200 mV vs. Ag/AgCl. CV data of samples pre-reduced in I-containing electrolyte exhibited a narrow Cu deposition peak in the overpotential region and a UPD peak. The kinetics of the electrodeposited Cu films was investigated by CTT measurements and applied to theoretical models of nucleation. The data indicated that a protective I adlayer may be deposited on an airexposed Ru electrode as the oxide surface is electrochemically reduced, and that this layer will inhibit reformation of an oxide during the Cu electroplating process. A novel method for epitaxial graphene growth directly on a dielectric substrate of systematically variable thickness was studied. Mono/multilayers of BN(111) were grown on Ru(0001) by atomic layer deposition (ALD), exhibiting a flat (non-nanomesh) R30(✓3x✓3) structure. BN(111) was used as a template for growth of graphene by chemical vapor deposition (CVD) of C2H4 at 1000 K. Characterization by LEED, Auger, STM/STS and Raman indicate the graphene is in registry with the BN substrate, and exhibits a HOPG-like 0 eV bandgap density

  5. Superconducting energy recovery linacs

    NASA Astrophysics Data System (ADS)

    Ben-Zvi, Ilan

    2016-10-01

    High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

  6. Electron Localization and Superconductivity in Two-Dimensional Metal Film Systems

    NASA Astrophysics Data System (ADS)

    Burns, Michael Joseph

    The low temperature electrical transport properties of very thin polycrystalline palladium and palladium-gold films grown on glass or fused quartz, and also the properties of epitaxially grown silver films on germanium (001), have been investigated. These, and other two dimensional electronic systems, display a nonmetallic conductivity which has been attributed to electron localization and/or electron-electron interaction effects. According to the various theories, some of the transport properties should display different behaviors, thus allowing one to distinguish between the two effects. Measurements of Pd and Pd-Au film resistivities as a function of temperature, electric and magnetic field, plus the thermopower, were performed on films ranging from 18 to 30 Angstroms in thickness, having resistivities from 600 to 500000 ohms/square at 10(DEGREES)K. The magnetotransport properties imply the presence of strong spin-orbit coupling, although the temperature dependence of the resistivity of these films does not. All 'metallic' samples (resistivities less than 30000 ohms/square) have a material specific thermopower which tends to zero as the temperature goes to zero. Samples whose resistivities increase above 30000 ohms/square have thermopowers which diverge as the temperature approaches zero. Thus the density of states for the electronic transport is zero at the Fermi energy (i.e. an energy gap opens in the density of states at 30000 ohms/square) for high -resistivity films. The very thin (2.5 monolayer) silver films epitaxially grown on Ge (001) consist of a monolayer coverage plus isolated three dimensional islands. Below 70(DEGREES)K the conductivity is dominated by the metal film and displays the temperature and electric and magnetic field dependencies characteristic of metallic weak localization in two dimensions. Below about 2(DEGREES)K, the resistance drops rapidly in a manner resembling an incomplete superconducting transition. The resistance is restored by

  7. Electron Bunch Timing with Femtosecond Precision in a Superconducting Free-Electron Laser

    SciTech Connect

    Loehl, F.; Arsov, V.; Felber, M.; Hacker, K.; Lorbeer, B.; Ludwig, F.; Matthiesen, K.-H.; Schlarb, H.; Schmidt, B.; Winter, A.; Jalmuzna, W.; Schmueser, P.; Schulz, S.; Zemella, J.; Szewinski, J.

    2010-04-09

    High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.

  8. Electron bunch timing with femtosecond precision in a superconducting free-electron laser.

    PubMed

    Löhl, F; Arsov, V; Felber, M; Hacker, K; Jalmuzna, W; Lorbeer, B; Ludwig, F; Matthiesen, K-H; Schlarb, H; Schmidt, B; Schmüser, P; Schulz, S; Szewinski, J; Winter, A; Zemella, J

    2010-04-09

    High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.

  9. Status report of the 28 GHz superconducting electron cyclotronresonance ion source VENUS

    SciTech Connect

    Leitner, Daniela; Lyneis, Claude M.; Loew, Timothy; Todd, D.S.; Virostek, S.; Tarvainen, O.

    2005-09-01

    The superconducting versatile electron cyclotron resonance ECR ion source for nuclear science (VENUS) is a next generation superconducting ECR ion source designed to produce high-current, high-charge-state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the rare isotope accelerator RIA front end, where the goal is to produce intense beams of medium-charge-state ions. Example beams for the RIA accelerator are 15 p mu A of Kr17+ (260 e mu A), 12 p mu A of Xe20+ (240e mu A), and 8 p mu A of U28+ (230 e mu A). To achieve these high currents, VENUS has been optimized for operation at 28 GHz, reaching maximal confinement fields of 4 and 3 T axially and over 2.2 T on the plasma chamber wall radially. After a commissioning phase at 18 GHz, the source started the 28 GHz operation in the summer of 2004. During that ongoing 28 GHz commissioning process, record ion-beam intensities have been extracted. For instance, measured extracted currents for the low to medium charge states were 270 e mu A of Xe27+ and 245 e mu A of Bi29+, while for the higher charge states 15 e mu A of Xe34+, 15 e mu A of Bi41+, and 0.5 e mu A of Bi50+ could be produced. Results from the ongoing 28 GHz commissioning as well as results using double-frequency heating with 18 and 28 GHz for oxygen and xenon are presented. The effect of the minimum B field on the ion source performance has been systematically measured for 18 and 28 GHz. In both cases the performance peaked at a minimum B field of about 80 percent of the resonance field. In addition, a strong dependence of the x-ray flux and energy on the minimum B field value was found.

  10. Electronic Structure of the Cuprate Superconducting and Pseudogap Phases from Spectroscopic Imaging STM

    SciTech Connect

    Davis, J.C.; Schmidt, A.R.; Fujita, K.; Kim, E.-A.; Lawler, M.J.; Eisaki, H.; Uchida, S.; Lee, D.-H.

    2011-06-21

    We survey the use of spectroscopic imaging scanning tunneling microscopy (SI-STM) to probe the electronic structure of underdoped cuprates. Two distinct classes of electronic states are observed in both the d-wave superconducting (dSC) and the pseudogap (PG) phases. The first class consists of the dispersive Bogoliubov quasiparticle excitations of a homogeneous d-wave superconductor, existing below a lower energy scale E = {Delta}{sub 0}. We find that the Bogoliubov quasiparticle interference (QPI) signatures of delocalized Cooper pairing are restricted to a k-space arc, which terminates near the lines connecting k = {+-}({pi}/a{sub 0},0) to k = {+-}(0,{pi}/a{sub 0}). This arc shrinks continuously with decreasing hole density such that Luttinger's theorem could be satisfied if it represents the front side of a hole-pocket that is bounded behind by the lines between k = {+-}({pi}/a{sub 0},0) and k = {+-}(0,{pi}/a{sub 0}). In both phases, the only broken symmetries detected for the |E| < {Delta}{sub 0} states are those of a d-wave superconductor. The second class of states occurs proximate to the PG energy scale E = {Delta}{sub 1}. Here the non-dispersive electronic structure breaks the expected 90{sup o}-rotational symmetry of electronic structure within each unit cell, at least down to 180{sup o}-rotational symmetry. This electronic symmetry breaking was first detected as an electronic inequivalence at the two oxygen sites within each unit cell by using a measure of nematic (C{sub 2}) symmetry. Incommensurate non-dispersive conductance modulations, locally breaking both rotational and translational symmetries, coexist with this intra-unit-cell electronic symmetry breaking at E = {Delta}{sub 1}. Their characteristic wavevector Q is determined by the k-space points where Bogoliubov QPI terminates and therefore changes continuously with doping. The distinct broken electronic symmetry states (intra-unit-cell and finite Q) coexisting at E {approx} {Delta}{sub 1} are

  11. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films.

    PubMed

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X J

    2016-02-08

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors.

  12. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films

    PubMed Central

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X. J.

    2016-01-01

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors. PMID:26853801

  13. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Study of Properties in Superconducting Nanowires

    NASA Astrophysics Data System (ADS)

    Liang, Fang-Ying; Wang, Jian-Hua; Zhang, Zhi-Gang

    2010-04-01

    We consider a simple approach of standard Ginzburg-Landau free-energy functional for a wire to study the properties of superconducting nanowires, and analyze the problem of quantum and thermally activated phase slips. In such systems one can consider a possibility for phase slips to be created not only due to thermal but also due to quantum fluctuations of a superconducting order parameter. We obtain some expressions of the free energy, the entropy, the specific heat and the bias current, respectively. The bias current I is a function of the temperature and the length of superconducting nanowires, and has a quantum phase slip. We obtain the stochastic dynamics of superconductive-resistive switching in hysteretic current-biased superconducting nanowires undergoing phase-slip fluctuations, and obtain the distribution of switching currents. Our results can be verified in modern experiments with superconducting nanowires.

  14. In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke; Kopas, Cameron; Wagner, Brian; Queen, Daniel; Newman, N.

    2016-09-01

    The physical nature and concentration of paramagnetic point defects in the dielectrics of superconducting planar microwave resonators have been determined using in-situ electron paramagnetic resonance spectroscopy. To perform this work, the quality factor of parallel plate and stripline resonators was measured as a function of the magnitude of a magnetic-field applied parallel to the electrode surfaces. YBa2Cu3O7-δ thin film electrodes proved to be a preferred choice over Nb and MgB2 because they are readily available and have a small surface resistance (Rs) up to high temperatures (˜77 K) and magnetic fields (i.e., <1 T). Stripline resonators with a widely used high performance microwave dielectric, Co2+-doped Ba(Zn1/3Nb2/3)O3, are shown to have losses dominated by d-electron spin-excitations in exchange-coupled Co2+ point-defect clusters, even in the absence of an applied magnetic field. A significant enhanced microwave loss in stripline and parallel plate resonators is found to correlate with the presence of paramagnetic Mn2+ dopants in Ba(Zn1/3Ta2/3)O3 ceramics and dangling bond states in amorphous Si thin films, although the identification of the dominant loss mechanism(s) in these dielectrics requires further investigation.

  15. Electronic structures and superconductivity of endohedrally doped C28 solids from first principles

    NASA Astrophysics Data System (ADS)

    Romero, Nichols A.; Kim, Jeongnim; Martin, Richard M.

    2007-11-01

    We present ab initio calculations of the crystalline phases of C28 : hyperdiamond and hyperlonsdaleite, in their pristine and endohedrally doped forms. These are hard materials with strong covalent bonds between the C28 molecules, and yet their electronic properties have remarkable similarities to the weakly bonded C28H4 molecular solids previously investigated [Phys. Rev. B 70, 140504(R) (2004)]. Our calculations show that they exhibit very narrow bands near the Fermi energy with an electron-phonon coupling that is well described by a molecular model and is larger than in C60 . Our study focuses on C28 solids endohedrally doped with Zr, a group-IVB tetravalent atom. Solid Zr@C28 is a small-gap insulator with Jahn-Teller distortions. Since the two structures considered are degenerate in energy, the actual material is expected to have disorder affecting the states at the Fermi energy and leading to a nonvanishing density of states. We conclude that the small density of states at the Fermi energy for Zr@C28 will lead to a superconducting transition temperature Tc lower than that found in K3C60 ; however, our results suggest that a higher Tc may be obtained using group-IIIB trivalent atoms.

  16. Design of the fundamental power coupler and photocathode inserts for the 112MHz superconducting electron gun

    SciTech Connect

    Xin, T.; Ben-Zvi, I.; Belomestnykh, S.; Chang, X.; Rao, T.; Skaritka, J.; Wu, Q.; Wang, E.; Liang, X.

    2011-07-25

    A 112 MHz superconducting quarter-wave resonator electron gun will be used as the injector of the Coherent Electron Cooling (CEC) proof-of-principle experiment at BNL. Furthermore, this electron gun can be the testing cavity for various photocathodes. In this paper, we present the design of the cathode stalks and a Fundamental Power Coupler (FPC) designated to the future experiments. Two types of cathode stalks are discussed. Special shape of the stalk is applied in order to minimize the RF power loss. The location of cathode plane is also optimized to enable the extraction of low emittance beam. The coaxial waveguide structure FPC has the properties of tunable coupling factor and small interference to the electron beam output. The optimization of the coupling factor and the location of the FPC are discussed in detail. Based on the transmission line theory, we designed a half wavelength cathode stalk which significantly brings down the voltage drop between the cavity and the stalk from more than 5.6 kV to 0.1 kV. The transverse field distribution on cathode has been optimized by carefully choosing the position of cathode stalk inside the cavity. Moreover, in order to decrease the RF power loss, a variable diameter design of cathode stalk has been applied. Compared to the uniform shape of stalk, this design gives us much smaller power losses in important locations. Besides that, we also proposed a fundamental power coupler based on the designed beam parameters for the future proof-of-principle CEC experiment. This FPC should give a strong enough coupling which has the Q external range from 1.5e7 to 2.6e8.

  17. Angular-divergence calculation for Experimental Advanced Superconducting Tokamak neutral beam injection ion source based on spectroscopic measurements

    SciTech Connect

    Chi, Yuan; Hu, Chundong; Zhuang, Ge

    2014-02-15

    Calorimetric method has been primarily applied for several experimental campaigns to determine the angular divergence of high-current ion source for the neutral beam injection system on the Experimental Advanced Superconducting Tokamak (EAST). A Doppler shift spectroscopy has been developed to provide the secondary measurement of the angular divergence to improve the divergence measurement accuracy and for real-time and non-perturbing measurement. The modified calculation model based on the W7AS neutral beam injectors is adopted to accommodate the slot-type accelerating grids used in the EAST's ion source. Preliminary spectroscopic experimental results are presented comparable to the calorimetrically determined value of theoretical calculation.

  18. Study of laser output power stabilization for a deuterium cyanide laser interferometer on the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Shi, N.; Gao, X.; Jie, Y. X.; Wang, E. H.

    2011-02-01

    A control system which can improve stabilization of laser power in long-term operation automatically is designed for a deuterium cyanide (DCN) far-infrared laser interferometer on the Experimental Advanced Superconducting Tokamak. It stabilizes the output power of the laser by a closed-loop control system aided by a programmable logic controller. The system has been applied to the DCN laser and it has been proven that it is effective in stabilizing the laser near the highest scope of the output power.

  19. Design of a magnetic shielding system for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak.

    PubMed

    Cui, Z Q; Chen, Z J; Xie, X F; Peng, X Y; Hu, Z M; Du, T F; Ge, L J; Zhang, X; Yuan, X; Xia, Z W; Hu, L Q; Zhong, G Q; Lin, S Y; Wan, B N; Fan, T S; Chen, J X; Li, X Q; Zhang, G H

    2014-11-01

    The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.

  20. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    PubMed Central

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Rüegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-01-01

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p  3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p  7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc  1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5  p  7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. PMID:26346548

  1. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs.

    PubMed

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K; Rüegg, Christian; Susner, Michael A; Sefat, Athena S; Zhigadlo, Nikolai D; Morenzoni, Elvezio

    2015-09-08

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 < or ~  p < or ~ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc(3.2) as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  2. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    SciTech Connect

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Ruegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  3. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: On Superconductivity State in Pure Graphene

    NASA Astrophysics Data System (ADS)

    Mousavi, Hamze

    2010-10-01

    We study theoretically the possibility of superconductivity state in pure graphene within the extended attractive Hubbard model. In the absence of disorder, when we use the local attractive interaction potential, U ⋍ 5t, where t is hopping term, pure graphene can be in superconductivity state.

  4. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    DOE PAGES

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; ...

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreasesmore » upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.« less

  5. Multiband semimetallic electronic structure of superconducting Ta2PdSe5

    SciTech Connect

    Singh, David Joseph

    2015-04-24

    We report the electronic structure and related properties of the superconductor Ta2PdSe5 as determined from density functional calculations. The Fermi surface has two disconnected sheets, both derived from bands of primarily chalcogenide p states. These are a corrugated hole cylinder and a heavier complex shaped electron sheet. The sheets contain 0.048 holes and a compensating number of electrons per formula unit, making the material a semimetallic superconductor. The results support the presence of two band superconductivity, although a discrepancy in the specific heat is noted. This discrepancy is discussed as a possible consequence of Pd deficiency in samples.

  6. Advances in High-Temperature Electronics

    NASA Astrophysics Data System (ADS)

    Normann, R. A.; Henfling, J. A.

    2001-05-01

    It has long been known that SOI (Silicon-On-Insulator) electronics are more resistant to elevated temperatures and radiation than common bulk silicon devices. Bulk silicon devices are used in consumer grade electronics. A new line of SOI devices have a proven life of 5 years at 225\\deg C where commercial electronics have an 80% failure rate at 180\\deg C and above. This improvement is the result of building each transistor on a non-conductive 'glass' substrate. The transistor isolation reduces the effects of heat, radiation and in general provides for better performing devices with greatly increased life expectancies. This paper shows how SOI electronics can greatly increase the instrumentation life of permanently installed electronics within the wellbore at any temperature. Information is provided from an SOI designed logging tool operating without any heat-shielding up to 300\\deg C. Additional information is provided on the future of micro-machines built out of silicon, silicon-carbide, and diamond. Silicon micro-machines are already being used to measure pressure, inclination, rotation and vibration. In the future, these micro-machines will offer a significant jump in technology for wellbore instrumentation.

  7. Los Alamos Advanced Free-Electron Laser

    SciTech Connect

    Chan, K.C.D.; Kraus, R.H.; Ledford, J.; Meier, K.L.; Meyer, R.E.; Nguyen, D.; Sheffield, R.L.; Sigler, F.L.; Young, L.M.; Wang, T.S.; Wilson, W.L.; Wood, R.L.

    1991-01-01

    At Los Alamos, we are building a free-electron laser (FEL) for industrial, medical, and research applications. This FEL, which will incorporate many of the new technologies developed over the last decade, will be compact in size, robust, and user-friendly. Electrons produced by a photocathode will be accelerated to 20 MeV by a high-brightness accelerator and transported using permanent-magnet quadrupoles and dipoles. They will form an electron beam with an excellent instantaneous beam quality of 10 {pi} mm mrad in transverse emittance and 0.3% in energy spread at a peak current up to 300 A. Including operation at higher harmonics, the laser wavelength extends form 3.7 {mu}m to 0.4 {mu}m. In this paper, we will describe the project and the programs to date. 10 refs., 10 figs., 1 tab.

  8. Thermal conductivity of the pyrochlore superconductor KOs2O6: strong electron correlations and fully gapped superconductivity.

    PubMed

    Kasahara, Y; Shimono, Y; Shibauchi, T; Matsuda, Y; Yonezawa, S; Muraoka, Y; Hiroi, Z

    2006-06-23

    To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (Tc=9.6 K), the thermal conductivity was measured down to low temperatures (approximately Tc/100). We found that the quasiparticle mean free path is strikingly enhanced below a transition at Tp=7.8 K, indicating enormous electron inelastic scattering in the normal state. In magnetic fields, the conduction at T-->0 K is nearly constant up to approximately 0.4Hc2, in contrast with the rapid growth expected for superconductors with an anisotropic gap. This unambiguously indicates a fully gapped superconductivity, in contrast with previous studies. These results highlight that KOs2O6 is unique among superconductors with strong electron correlations.

  9. 75 FR 21367 - Advanced Electronics, Inc.; Boston, MA; Notice of Negative Determination on Remand

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-23

    ... Employment and Training Administration Advanced Electronics, Inc.; Boston, MA; Notice of Negative... Department of Labor (Department) for further investigation Former Employees of Advanced Electronics, Inc. v... Adjustment Assistance (ATAA) applicable to workers and former workers of Advanced Electronics, Inc.,...

  10. Center for Space Power and Advanced Electronics, Auburn University

    NASA Technical Reports Server (NTRS)

    Deis, Dan W.; Hopkins, Richard H.

    1991-01-01

    The union of Auburn University's Center for Space Power and Advanced Electronics and the Westinghouse Science and Technology Center to form a Center for the Commercial Development of Space (CCDS) is discussed. An area of focus for the CCDS will be the development of silicon carbide electronics technology, in terms of semiconductors and crystal growth. The discussion is presented in viewgraph form.

  11. Development of Superconducting Transition Edge Sensors Based on Electron-Phonon Decoupling

    NASA Technical Reports Server (NTRS)

    Jethava, Nikhil; Chervenak, James; Brown, Ari-David; Benford, Dominic; Kletetschka, Gunther; Mikula, Vilem; U-yen, Kongpop

    2010-01-01

    We have successfully fabricated a superconducting transition edge sensor (TES), bolometer that centers on the use of electron-phonon decoupling (EPD) for thermal isolation. We have selected a design approach that separates the two functions of far-infrared and THz radiative power absorption and temperature measurement, allowing separate optimization of the performance of each element. We have integrated molybdenum/gold (Mo/Au) bilayer TES and ion assisted thermally evaporated (IAE) bismuth (Bi) films as radiation absorber coupled to a low-loss microstripline from niobium (Nb) ground plane to a twin-slot antenna structure. The thermal conductance (G) and the time constant for the different geometry device have been measured. For one such device, the measured G is 1.16 x 10(exp -10) W/K (plus or minus 0.61 x 10(exp- 10) W/K) at 60 mK, which corresponds to noise equivalent power (NEP) = 1.65 X 10(exp -18)W/vHz and time constant of approximately 5 microseconds.

  12. A simulation of X-ray shielding for a superconducting electron cyclotron resonance ion source

    SciTech Connect

    Park, Jin Yong; Won, Mi-Sook; Lee, Byoung-Seob; Yoon, Jang-Hee; Choi, Seyong; Ok, Jung-Woo; Choi, Jeong-Sik; Kim, Byoung-Chul

    2014-02-15

    It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source.

  13. The importance of the electron mean free path for superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Maniscalco, J. T.; Gonnella, D.; Liepe, M.

    2017-01-01

    Impurity-doping of niobium is an exciting new technology in the field of superconducting radio-frequency accelerators, producing cavities with record-high quality factor Q0 and Bardeen-Cooper-Schrieffer surface resistance that decreases with increasing radio-frequency field. Recent theoretical work has offered a promising explanation for this so-called "anti-Q-slope," but the link between the decreasing surface resistance and the shortened electron mean free path of doped cavities has remained elusive. In this work, we investigate this link, finding that the magnitude of this decrease varies directly with the mean free path: shorter mean free paths correspond to stronger anti-Q-slopes. We draw a theoretical connection between the mean free path and the overheating of the quasiparticles, which leads to the reduction of the anti-Q-slope towards the normal Q-slope of long-mean-free-path cavities. We also investigate the sensitivity of the residual resistance to trapped magnetic flux, a property that is greatly enhanced for doped cavities, and calculate an optimal doping regime for a given amount of trapped flux.

  14. First results from the new RIKEN superconducting electron cyclotron resonance ion source (invited).

    PubMed

    Nakagawa, T; Higurashi, Y; Ohnishi, J; Aihara, T; Tamura, M; Uchiyama, A; Okuno, H; Kusaka, K; Kidera, M; Ikezawa, E; Fujimaki, M; Sato, Y; Watanabe, Y; Komiyama, M; Kase, M; Goto, A; Kamigaito, O; Yano, Y

    2010-02-01

    The next generation heavy ion accelerator facility, such as the RIKEN radio isotope (RI) beam factory, requires an intense beam of high charged heavy ions. In the past decade, performance of the electron cyclotron resonance (ECR) ion sources has been dramatically improved with increasing the magnetic field and rf frequency to enhance the density and confinement time of plasma. Furthermore, the effects of the key parameters (magnetic field configuration, gas pressure, etc.) on the ECR plasma have been revealed. Such basic studies give us how to optimize the ion source structure. Based on these studies and modern superconducting (SC) technology, we successfully constructed the new 28 GHz SC-ECRIS, which has a flexible magnetic field configuration to enlarge the ECR zone and to optimize the field gradient at ECR point. Using it, we investigated the effect of ECR zone size, magnetic field configuration, and biased disk on the beam intensity of the highly charged heavy ions with 18 GHz microwaves. In this article, we present the structure of the ion source and first experimental results with 18 GHz microwave in detail.

  15. Pressure dependence of electronic structure and superconductivity of the MnX (X = N, P, As, Sb)

    PubMed Central

    Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2016-01-01

    A recently experimental discovered (Cheng et al., Phys. Rev. Lett. 114, 117001 (2015)) of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure makes MnP the first Mn-based superconductor. In this paper, we carry out first-principles calculations on MnX (X = N, P, As, Sb) and find superconducting critical temperature TC of MnP sharply increases near the critical pressure PC ≈ 8 GPa, which is in good agreement with the experiments. Electron-phonon coupling constant λ and electronic density of states at the Fermi level N (EF) are found to increase with pressure for MnP, which lead to the increase of TC of MnP. Moreover, we also find that the TC of MnAs and MnSb are higher than MnP, implying that the MnAs and MnSb may be the more potential Mn-based superconducting materials. PMID:26902857

  16. An electron tunneling study of superconductivity in amorphous Sn(sub 1-x)Cu(sub x) thin films

    NASA Technical Reports Server (NTRS)

    Naugle, D. G.; Watson, P. W., III; Rathnayaka, K. D. D.

    1995-01-01

    The amorphous phase of Sn would have a superconducting transition temperature near 8 K, much higher than that of crystalline Sn with T(sub c) = 3.5 K. To obtain the amorphous phase, however, it is necessary to use a Sn alloy, usually Cu, and quench condense the alloy films onto a liquid He temperature substrate. Alloying with Cu reduces the superconducting transition temperature almost linearly with Cu concentration with an extrapolation of T(sub c) to zero for x = 0.85. Analysis of the tunneling characteristics between a normal metal electrode with an insulating barrier and superconducting amorphous Sn-Cu films provides detailed information on the changes in the electron-phonon coupling which determines T(sub c) in these alloys. The change from very strong electron-phonon coupling to weak-coupling with the increase in Cu content of amorphous Sn-Cu alloys for the range 0.08 is less than or equal to x is less than or equal to 0.41 is presented and discussed in terms of theories of electron-phonon coupling in disordered metals.

  17. Pressure dependence of electronic structure and superconductivity of the MnX (X = N, P, As, Sb).

    PubMed

    Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2016-02-23

    A recently experimental discovered (Cheng et al., Phys. Rev. Lett. 114, 117001 (2015)) of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure makes MnP the first Mn-based superconductor. In this paper, we carry out first-principles calculations on MnX (X = N, P, As, Sb) and find superconducting critical temperature TC of MnP sharply increases near the critical pressure PC ≈ 8 GPa, which is in good agreement with the experiments. Electron-phonon coupling constant λ and electronic density of states at the Fermi level N (EF) are found to increase with pressure for MnP, which lead to the increase of TC of MnP. Moreover, we also find that the TC of MnAs and MnSb are higher than MnP, implying that the MnAs and MnSb may be the more potential Mn-based superconducting materials.

  18. Quantum functional devices for advanced electronics

    NASA Astrophysics Data System (ADS)

    Yokoyama, N.; Muto, S.; Imamura, K.; Takatsu, M.; Mori, T.; Sugiyama, Y.; Sakuma, Y.; Nakao, H.; Adachihara, T.

    Recent research in semiconductor device technology seems to be focused on reducing the cost and power dissipation of traditional Si CMOS integrated circuits, rather than developing new and advanced semiconductor devices. We believe however, that devices enter the nanometer-scale regime in the next century, where quantum mechanical effects play an important role in the device's function; therefore, it is important to continue basic research into the physics and technology of nanometer scale structures and device applications in order to cultivate "nanoelectronics". This paper reviews our research activities on quantum functional devices and discusses our future research direction.

  19. Recent Advancements in Functionalized Paper-Based Electronics.

    PubMed

    Lin, Yang; Gritsenko, Dmitry; Liu, Qian; Lu, Xiaonan; Xu, Jie

    2016-08-17

    Building electronic devices on ubiquitous paper substrates has recently drawn extensive attention due to its light weight, low cost, environmental friendliness, and ease of fabrication. Recently, a myriad of advancements have been made to improve the performance of paper electronics for various applications, such as basic electronic components, energy storage devices, generators, antennas, and electronic circuits. This review aims to summarize this progress and discuss different perspectives of paper electronics as well as the remaining challenges yet to be overcome in this field. Other aspects included in this review are the fundamental characteristics of paper, modification of paper with functional materials, and various methods for device fabrication.

  20. Status report of the 28 GHz superconducting electron cyclotron resonance ion source VENUS (invited)

    SciTech Connect

    Leitner, D.; Lyneis, C.M.; Loew, T.; Todd, D.S.; Virostek, S.; Tarvainen, O.

    2006-03-15

    The superconducting versatile electron cyclotron resonance (ECR) ion source for nuclear science (VENUS) is a next generation superconducting ECR ion source designed to produce high-current, high-charge-state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the rare isotope accelerator (RIA) front end, where the goal is to produce intense beams of medium-charge-state ions. Example beams for the RIA accelerator are 15 p {mu}A of Kr{sup 17+}(260 e {mu}A), 12 p {mu}A of Xe{sup 20+} (240 e {mu}A of Xe{sup 20+}), and 8 p {mu}A of U{sup 28+}(230 e {mu}A). To achieve these high currents, VENUS has been optimized for operation at 28 GHz, reaching maximal confinement fields of 4 and 3 T axially and over 2.2 T on the plasma chamber wall radially. After a commissioning phase at 18 GHz, the source started the 28 GHz operation in the summer of 2004. During that ongoing 28 GHz commissioning process, record ion-beam intensities have been extracted. For instance, measured extracted currents for the low to medium charge states were 270 e {mu}A of Xe{sup 27+} and 245 e {mu}A of Bi{sup 29+}, while for the higher charge states 15 e {mu}A of Xe{sup 34+}, 15 e {mu}A of Bi{sup 41+}, and 0.5 e {mu}A of Bi{sup 50+} could be produced. Results from the ongoing 28 GHz commissioning as well as results using double-frequency heating with 18 and 28 GHz for oxygen and xenon are presented. The effect of the minimum B field on the ion source performance has been systematically measured for 18 and 28 GHz. In both cases the performance peaked at a minimum B field of about 80% of the resonance field. In addition, a strong dependence of the x-ray flux and energy on the minimum B field value was found.

  1. Advanced power electronics and electric machinery program

    SciTech Connect

    None, None

    2007-12-01

    The U.S. Department of Energy (DOE) and the U.S. Council for Automotive Research (composed of automakers Ford, General Motors, and Chrysler) announced in January 2002 a new cooperative research effort. Known as "FreedomCAR" (derived from "Freedom" and "Cooperative Automotive Research"), it represents DOE's commitment to developing public/private partnerships to fund high-risk, high-payoff research into advanced automotive technologies. Efficient fuel cell technology, which uses hydrogen to power automobiles without air pollution, is a very promising pathway to achieving the ultimate vision. The new partnership replaces and builds upon the Partnership for a New Generation of Vehicles initiative that ran from 1993 through 2001.

  2. Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model

    NASA Astrophysics Data System (ADS)

    Zhu, Lijun; Zhu, Jian-Xin

    2011-03-01

    We study the non-local superconducting pairing of two interacting Anderson impurities, which has an instability near the quantum critical point from the competition between the Kondo effect and an antiferromagnetic inter-impurity spin exchange interaction. As revealed by the dynamics over the whole energy range, the superconducting pairing fluctuations acquire considerable strength from an energy scale much higher than the characteristic spin fluctuation scale while the low energy behaviors follow those of the staggered spin susceptibility. We argue that the superconducting pairing might not need the spin fluctuations as the glue, but rather originated from the effective Coulomb interaction. On the other hand, critical spin fluctuations in the vicinity of quantum criticality are also crucial to a superconducting pairing instability, by preventing a Fermi liquid fixed point being reached to keep the superconducting pairing fluctuations finite at low energies. A superconducting order, to reduce the accumulated entropy carried by the critical degrees of freedom, may arise favorably from this instability. This work is supported by the U.S. DOE through the LANL/LDRD program.

  3. Elimination of bubbles and improvement of the superconducting properties in MgB2 films annealed using electron beam

    NASA Astrophysics Data System (ADS)

    Xu, Zhuang; Kong, Xiangdong; Han, Li; Pang, Hua; Wu, Yue; Gao, Zhaoshun; Li, Xiaona

    2017-03-01

    MgB2 superconducting films can be readily obtained using the electron-beam annealing method. However, many bubbles existing in the film severely damage the surface morphology, which is known as the deleterious current-limiting mechanism. Based on morphology images and energy-dispersive spectroscopy spectra, we found that, during the annealing process, solid Mg-rich layers evaporate to form Mg vapour in the precursor film, resulting in bubbles in the film. By reducing the cycle thickness of the precursor film, we obtained MgB2 films with better properties. The root-mean-square surface roughness was 2.7 nm over a 10 × 10 μm area for a 100 nm-thick film, and the critical current density at 20 K was increased to 3.8 × 106 A cm‑2. These MgB2 films are suitable for fabricating MgB2 superconducting devices.

  4. New Trend in THz Detection: High Tc Superconducting Hot Electron Bolometer Technology May Exhibit Advantage vs Low Tc Devices

    NASA Astrophysics Data System (ADS)

    Kreisler, A. J.; Degardin, A. F.; Aurino, M.; Peroz, C.; Villegier, J.-C.; Beaudin, G.; Delorme, Y.; Redon, M.; Sentz, A.

    2007-07-01

    Superconducting hot electron bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the terahertz range because of their ultrawide bandwidth, high conversion gain, and low intrinsic noise level, even at 77 K. A technological process to realize HEBs based on high-Tc YBa2Cu3O7-zeta (YBCO) materials is described. Ultrathin 12 to 40 nm layers were sputtered on MgO (100) substrates, sub-micrometer constrictions (0.5 micrometer x 0.5 micrometer) were etched on these and log-periodic gold antennas were then integrated. Good superconducting properties were measured after the whole process. Electrical transport characteristics of the device are discussed, ageing effects are considered and regular bolometric THz response results are given.

  5. Electronic structure of a superconducting topological insulator Sr-doped Bi{sub 2}Se{sub 3}

    SciTech Connect

    Han, C. Q.; Chen, W. J.; Zhu, Fengfeng; Yao, Meng-Yu; Li, H.; Li, Z. J.; Wang, M.; Gao, Bo F.; Guan, D. D.; Liu, Canhua; Qian, Dong Jia, Jin-Feng; Gao, C. L.

    2015-10-26

    Using high-resolution angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy, the atomic and low energy electronic structure of the Sr-doped superconducting topological insulators (Sr{sub x}Bi{sub 2}Se{sub 3}) was studied. Scanning tunneling microscopy shows that most of the Sr atoms are not in the van der Waals gap. After Sr doping, the Fermi level was found to move further upwards when compared with the parent compound Bi{sub 2}Se{sub 3}, which is consistent with the low carrier density in this system. The topological surface state was clearly observed, and the position of the Dirac point was determined in all doped samples. The surface state is well separated from the bulk conduction bands in the momentum space. The persistence of separated topological surface state combined with small Fermi energy makes this superconducting material a very promising candidate for the time reversal invariant topological superconductor.

  6. Advanced thermal management techniques for space power electronics

    NASA Astrophysics Data System (ADS)

    Reyes, Angel Samuel

    1992-01-01

    Modern electronic systems used in space must be reliable and efficient with thermal management unaffected by outer space constraints. Current thermal management techniques are not sufficient for the increasing waste heat dissipation of novel electronic technologies. Many advanced thermal management techniques have been developed in recent years that have application in high power electronic systems. The benefits and limitations of emerging cooling technologies are discussed. These technologies include: liquid pumped devices, mechanically pumped two-phase cooling, capillary pumped evaporative cooling, and thermoelectric devices. Currently, liquid pumped devices offer the most promising alternative for electronics thermal control.

  7. Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides.

    PubMed

    Ang, R; Wang, Z C; Chen, C L; Tang, J; Liu, N; Liu, Y; Lu, W J; Sun, Y P; Mori, T; Ikuhara, Y

    2015-01-27

    Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2-xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal-insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom.

  8. Quantum spin correlations through the superconducting-to-normal phase transition in electron-doped superconducting Pr0.88LaCe0.12CuO4-delta.

    PubMed

    Wilson, Stephen D; Li, Shiliang; Zhao, Jun; Mu, Gang; Wen, Hai-Hu; Lynn, Jeffrey W; Freeman, Paul G; Regnault, Louis-Pierre; Habicht, Klaus; Dai, Pengcheng

    2007-09-25

    The quantum spin fluctuations of the S = 1/2 Cu ions are important in determining the physical properties of high-transition-temperature (high T(c)) copper oxide superconductors, but their possible role in the electron pairing of superconductivity remains an open question. The principal feature of the spin fluctuations in optimally doped high-T(c) superconductors is a well defined magnetic resonance whose energy (E(R)) tracks T(c) (as the composition is varied) and whose intensity develops like an order parameter in the superconducting state. We show that the suppression of superconductivity and its associated condensation energy by a magnetic field in the electron-doped high-T(c) superconductor Pr(0.88)LaCe(0.12)CuO(4-delta) (T(c) = 24 K), is accompanied by the complete suppression of the resonance and the concomitant emergence of static antiferromagnetic order. Our results demonstrate that the resonance is intimately related to the superconducting condensation energy, and thus suggest that it plays a role in the electron pairing and superconductivity.

  9. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Baca, D.M.; Chan, K.C.D.; Cheairs, R.B.; Fortgang, C.M.; Gierman, S.M.; Johnson, W.J.D.; Holcomb, D.E.; Kinross-Wright, J.; McCann, S.W.; Meier, K.L.; Plato, J.G.; Sheffield, R.L.; Sherwood, B.A.; Sigler, F.E.; Timmer, C.A.; Warren, R.W.; Weber, M.E.; Wilson, W.L.

    1992-09-01

    We report recent results on the high-brightness electron linac and initial performance of the Advanced FEL at Los Alamos. The design and construction of the Advanced FEL beamline are based upon integration of advanced technologies such as high-brightness photoinjector, high-gradient compact linac, and permanent-magnet beamline components. With the use of microwiggler, both permanent magnet and pulsed electromagnet, and compact optical resonator, the Advanced FEL will be the first of its kind small enough to be mounted on an optical table and yet capable of providing highpower optical output spanning the near-ir and visible regions. A schematic of the Advanced FEL is shown in. The source of high-current electron pulses is a laser-gated photoelectron injector which forms-an integral part of a high-gradient 1.2-m long rf linear accelerator. The latter is capable of accelerating electrons up to 20 MeV with room temperature operation and 25 MeV at 77K. The electrons are produced in 10-ps pulses with peak currents as high as 300 A. These electron pulses are transported in a brightness-preserving beamline consisting of permanent magnet dipoles and quadrupoles. The beamline has three 30{degrees} bends. The first bend allows for the photocathode drive laser input; the second allows for the FEL output and the third turns the electron beam into the floor for safety reasons. Additional information on the design physics of the Advanced FEL can be found elsewhere.

  10. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Baca, D.M.; Chan, K.C.D.; Cheairs, R.B.; Fortgang, C.M.; Gierman, S.M.; Johnson, W.J.D.; Holcomb, D.E.; Kinross-Wright, J.; McCann, S.W.; Meier, K.L.; Plato, J.G.; Sheffield, R.L.; Sherwood, B.A.; Sigler, F.E.; Timmer, C.A.; Warren, R.W.; Weber, M.E.; Wilson, W.L.

    1992-01-01

    We report recent results on the high-brightness electron linac and initial performance of the Advanced FEL at Los Alamos. The design and construction of the Advanced FEL beamline are based upon integration of advanced technologies such as high-brightness photoinjector, high-gradient compact linac, and permanent-magnet beamline components. With the use of microwiggler, both permanent magnet and pulsed electromagnet, and compact optical resonator, the Advanced FEL will be the first of its kind small enough to be mounted on an optical table and yet capable of providing highpower optical output spanning the near-ir and visible regions. A schematic of the Advanced FEL is shown in. The source of high-current electron pulses is a laser-gated photoelectron injector which forms-an integral part of a high-gradient 1.2-m long rf linear accelerator. The latter is capable of accelerating electrons up to 20 MeV with room temperature operation and 25 MeV at 77K. The electrons are produced in 10-ps pulses with peak currents as high as 300 A. These electron pulses are transported in a brightness-preserving beamline consisting of permanent magnet dipoles and quadrupoles. The beamline has three 30{degrees} bends. The first bend allows for the photocathode drive laser input; the second allows for the FEL output and the third turns the electron beam into the floor for safety reasons. Additional information on the design physics of the Advanced FEL can be found elsewhere.

  11. Superconductivity in Medicine

    NASA Astrophysics Data System (ADS)

    Alonso, Jose R.; Antaya, Timothy A.

    2012-01-01

    Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

  12. Superconductivity below 20 K in heavily electron-doped surface layer of FeSe bulk crystal.

    PubMed

    Seo, J J; Kim, B Y; Kim, B S; Jeong, J K; Ok, J M; Kim, Jun Sung; Denlinger, J D; Mo, S-K; Kim, C; Kim, Y K

    2016-04-06

    A superconducting transition temperature (Tc) as high as 100 K was recently discovered in one monolayer FeSe grown on SrTiO3. The discovery ignited efforts to identify the mechanism for the markedly enhanced Tc from its bulk value of 8 K. There are two main views about the origin of the Tc enhancement: interfacial effects and/or excess electrons with strong electron correlation. Here, we report the observation of superconductivity below 20 K in surface electron-doped bulk FeSe. The doped surface layer possesses all the key spectroscopic aspects of the monolayer FeSe on SrTiO3. Without interfacial effects, the surface layer state has a moderate Tc of 20 K with a smaller gap opening of 4.2 meV. Our results show that excess electrons with strong correlation cannot induce the maximum Tc, which in turn reveals the need for interfacial effects to achieve the highest Tc in one monolayer FeSe on SrTiO3.

  13. Superconductivity below 20 K in heavily electron-doped surface layer of FeSe bulk crystal

    PubMed Central

    Seo, J. J.; Kim, B. Y.; Kim, B. S.; Jeong, J. K.; Ok, J. M.; Kim, Jun Sung; Denlinger, J. D.; Mo, S. -K.; Kim, C.; Kim, Y. K.

    2016-01-01

    A superconducting transition temperature (Tc) as high as 100 K was recently discovered in one monolayer FeSe grown on SrTiO3. The discovery ignited efforts to identify the mechanism for the markedly enhanced Tc from its bulk value of 8 K. There are two main views about the origin of the Tc enhancement: interfacial effects and/or excess electrons with strong electron correlation. Here, we report the observation of superconductivity below 20 K in surface electron-doped bulk FeSe. The doped surface layer possesses all the key spectroscopic aspects of the monolayer FeSe on SrTiO3. Without interfacial effects, the surface layer state has a moderate Tc of 20 K with a smaller gap opening of 4.2 meV. Our results show that excess electrons with strong correlation cannot induce the maximum Tc, which in turn reveals the need for interfacial effects to achieve the highest Tc in one monolayer FeSe on SrTiO3. PMID:27050161

  14. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1998-05-19

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  15. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1997-03-11

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  16. Superconductivity in transition metals.

    PubMed

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified.

  17. An advanced arrangement of the combined propulsion, levitation and guidance system of superconducting Maglev

    SciTech Connect

    Fujie, Junji

    1999-09-01

    The PLG (combined Propulsion, Levitation and Guidance) method was proposed for a more favorable Maglev ground coil system, combining the functions of propulsion, levitation, and guidance of the vehicle into one coil. Research and development is currently being conducted on this method. In this paper, the characteristics of a newly-structured system for the PLG method is examined. The discussed characteristics include propulsion, levitation-guidance, vehicle dynamics in the cases of problems with the superconducting magnets, and the magnetic field on board the vehicle.

  18. Three energy scales in the superconducting state of hole-doped cuprates detected by electronic Raman scattering

    DOE PAGES

    Benhabib, S.; Gu, G. D.; Gallais, Y.; ...

    2015-10-06

    We explore by electronic Raman scattering the superconducting state of the Bi2Sr2CaCu2O8+δ (Bi-2212) crystal by performing a fine-tuned doping study. We find three distinct energy scales in A1g, B1g, and B2g symmetries which show three distinct doping dependencies. Above p=0.22, the three energies merge; below p=0.12, the A1g scale is no longer detectable, while the B1g and B2g scales become constant in energy. In between, the A1g and B1g scales increase monotonically with underdoping, while the B2g one exhibits a maximum at p=0.16. The three superconducting energy scales appear to be a universal feature of hole-doped cuprates. Furthermore, we proposemore » that the nontrivial doping dependencies of the three scales originate from the Fermi-surface changes and reveal competing orders inside the superconducting dome.« less

  19. Three energy scales in the superconducting state of hole-doped cuprates detected by electronic Raman scattering

    SciTech Connect

    Benhabib, S.; Gu, G. D.; Gallais, Y.; Cazayous, M.; Measson, M. -A.; Zhong, R. D.; Schneeloch, J.; Forget, A.; Colson, D.; Sacuto, A.

    2015-10-06

    We explore by electronic Raman scattering the superconducting state of the Bi2Sr2CaCu2O8+δ (Bi-2212) crystal by performing a fine-tuned doping study. We find three distinct energy scales in A1g, B1g, and B2g symmetries which show three distinct doping dependencies. Above p=0.22, the three energies merge; below p=0.12, the A1g scale is no longer detectable, while the B1g and B2g scales become constant in energy. In between, the A1g and B1g scales increase monotonically with underdoping, while the B2g one exhibits a maximum at p=0.16. The three superconducting energy scales appear to be a universal feature of hole-doped cuprates. Furthermore, we propose that the nontrivial doping dependencies of the three scales originate from the Fermi-surface changes and reveal competing orders inside the superconducting dome.

  20. Electronic structure properties and superconductivity of the β-pyrochlore Os oxides, AOs2O6 (A=alkali metal)

    NASA Astrophysics Data System (ADS)

    Saniz, R.

    2005-03-01

    The recently discoveredootnotetextT. Muramatsu et al. J. Phys. Soc. Jpn. 73, 10 (2004). family of superconducting β-pyrochlores AOs2O6 (A=alkali metal) represents a particularly interesting example of the interplay between superconductivity and orbital and crystal structure degrees of freedom. Indeed, the pyrochlore lattice formed by the Os-O staggered chains appears to lead to very high Sommerfeld coefficients, increasing of Tc under positive pressure, and other intriguing properties. We present results of a first-principles study of the electronic structure and superconducting properties of these materials (A=Na, K, Rb, and Cs) using the highly precise full-potential linearized augmented plane wave (FLAPW) method.ootnotetextWimmer, Krakauer, Weinert, Freeman, Phys. Rev. B 24, 864 (1981). We show that the observed increase of Tc with decreasing mass of A as well as under positive hydrostatic pressure can both be well understood within a conventional phonon-mediated pairing picture. Furthermore, the density of states at EF depends critically on spin-orbit coupling, due to a van Hove singularity near EF, with a direct effect on Tc; the Fermi surface shows strong nesting, which is reflected in the dynamic susceptibility and thus indicates that spin fluctuations may play an important role in these materials.

  1. Superconducting Multi-Cell Deflecting Cavity for Short-Pulse X-Ray Generation at the Advanced Photon Source

    SciTech Connect

    G.J. Waldschmidt, L.H. Morrison, R. Nassiri, R.A. Rimmer, K. Tian, H. Wang

    2009-05-01

    A superconducting multi-cell cavity for the production of short x-ray pulses at the Advanced Photon Source (APS) has been explored as an alternative to a single-cell cavity design in order to improve the packing factor and potentially reduce the number of high-power RF systems and low-level RF controls required. The cavity will operate at 2815 MHz in the APS storage ring and will require heavy damping of parasitic modes to maintain stable beam operation. Novel on-cell dampers, attached directly to the cavity body, have been utilized by taking advantage of the magnetic field null on the equatorial plane in order to enhance damping. Design issues and simulation results will be discussed.

  2. Numerical Investigation of a Cascaded Longitudinal Space-Charge Amplifier at the Fermilab's Advanced Superconducting Test Accelerator

    SciTech Connect

    Halavanau, A.; Piot, P.

    2015-06-01

    In a cascaded longitudinal space-charge amplifier (LSCA), initial density noise in a relativistic e-beam is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. This type of amplification process was shown to potentially result in large final density modulations [1] compatible with the production of broadband electromagnetic radiation. The technique was recently demonstrated in the optical domain [2]. In this paper we investigate, via numerical simulations, the performances of a cascaded LSCA beamline at the Fermilab’s Advanced Superconducting Test Accelerator (ASTA). We especially explore the properties of the produced broadband radiation. Our studies have been conducted with a grid-less three-dimensional space-charge algorithm.

  3. Fast valve based on double-layer eddy-current repulsion for disruption mitigation in Experimental Advanced Superconducting Tokamak.

    PubMed

    Zhuang, H D; Zhang, X D

    2015-05-01

    A fast valve based on the double-layer eddy-current repulsion mechanism has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to a double-layer eddy-current coil, a preload system was added to improve the security of the valve, whereby the valve opens more quickly and the open-valve time becomes shorter, making it much safer than before. In this contribution, testing platforms, open-valve characteristics, and throughput of the fast valve are discussed. Tests revealed that by choosing appropriate parameters the valve opened within 0.15 ms, and open-valve times were no longer than 2 ms. By adjusting working parameter values, the maximum number of particles injected during this open-valve time was estimated at 7 × 10(22). The fast valve will become a useful tool to further explore disruption mitigation experiments on EAST in 2015.

  4. BORON NITRIDE CAPACITORS FOR ADVANCED POWER ELECTRONIC DEVICES

    SciTech Connect

    N. Badi; D. Starikov; C. Boney; A. Bensaoula; D. Johnstone

    2010-11-01

    This project fabricates long-life boron nitride/boron oxynitride thin film -based capacitors for advanced SiC power electronics with a broad operating temperature range using a physical vapor deposition (PVD) technique. The use of vapor deposition provides for precise control and quality material formation.

  5. FY2009 Annual Progress Report for Advanced Power Electronics

    SciTech Connect

    Rogers, Susan A.

    2010-01-01

    The Advanced Power Electronics and Electric Machines (APEEM) subprogram within the Vehicle Technologies Program provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on understanding and improving the way the various new components of tomorrow's automobiles will function as a unified system to improve fuel efficiency.

  6. Epidermal electronics with advanced capabilities in near-field communication.

    PubMed

    Kim, Jeonghyun; Banks, Anthony; Cheng, Huanyu; Xie, Zhaoqian; Xu, Sheng; Jang, Kyung-In; Lee, Jung Woo; Liu, Zhuangjian; Gutruf, Philipp; Huang, Xian; Wei, Pinghung; Liu, Fei; Li, Kan; Dalal, Mitul; Ghaffari, Roozbeh; Feng, Xue; Huang, Yonggang; Gupta, Sanjay; Paik, Ungyu; Rogers, John A

    2015-02-25

    Epidermal electronics with advanced capabilities in near field communications (NFC) are presented. The systems include stretchable coils and thinned NFC chips on thin, low modulus stretchable adhesives, to allow seamless, conformal contact with the skin and simultaneous capabilities for wireless interfaces to any standard, NFC-enabled smartphone, even under extreme deformation and after/during normal daily activities.

  7. Development of a ferromagnetic component in the superconducting state of Fe-excess Fe1.12Te1-xSex by electronic charge redistribution

    PubMed Central

    Li, Wen-Hsien; Karna, Sunil K.; Hsu, Han; Li, Chi-Yen; Lee, Chi-Hung; Sankar, Raman; Cheng Chou, Fang

    2015-01-01

    The general picture established so far for the links between superconductivity and magnetic ordering in iron chalcogenide Fe1+y(Te1-xSex) is that the substitution of Se for Te directly drives the system from the antiferromagnetic end into the superconducting regime. Here, we report on the observation of a ferromagnetic component that developed together with the superconducting transition in Fe-excess Fe1.12Te1-xSex crystals using neutron and x-ray diffractions, resistivity, magnetic susceptibility and magnetization measurements. The superconducting transition is accompanied by a negative thermal expansion of the crystalline unit cell and an electronic charge redistribution, where a small portion of the electronic charge flows from around the Fe sites toward the Te/Se sites. First-principles calculations show consistent results, revealing that the excess Fe ions play a more significant role in affecting the magnetic property in the superconducting state than in the normal state and the occurrence of an electronic charge redistribution through the superconducting transition. PMID:26077466

  8. Advanced electron microscopy characterization of nanomaterials for catalysis

    DOE PAGES

    Su, Dong

    2017-02-11

    Transmission electron microscopy (TEM) has become one of the most powerful techniques in the fields of material science, inorganic chemistry and nanotechnology. In terms of resolutions, advanced TEM may reach a high spatial resolution of 0.05 nm, a high energy-resolution of 7 meV. In addition, in situ TEM can help researcher to image the process happened within 1 ms. This paper reviews the recent technical approaches of applying advanced TEM characterization on nanomaterials for catalysis. The text is organized according to the demanded information of nanocrystals from the perspective of application: for example, size, composition, phase, strain, and morphology. Themore » electron beam induced effect and in situ TEM are also introduced. As a result, I hope this review can help the scientists in related fields to take advantage of advanced TEM to their own researches.« less

  9. Adiabatic Demagnetization Refrigerator Field Mapping and Shielding Models for a 70 mK Superconducting Transition Edge Sensor Array and Associated Electronics

    SciTech Connect

    Ladner, D. R.; Martinez-Galarce, D. S.; McCammon, D.

    2006-04-27

    An X-ray detection instrument to be flown on a sounding rocket experiment (the Advanced Technology Solar Spectroscopic Imager -- ATSSI) for solar physics observations is being developed by the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL). The detector is a novel class of microcalorimeter, a superconducting Transition-Edge Sensor (TES), that coupled with associated SQUID and feedback electronics requires high temperature stability at {approx}70 mK to resolve the energy of absorbed X-ray photons emitted from the solar corona. The cooling system incorporates an existing Adiabatic Demagnetization Refrigerator (ADR) developed at the University of Wisconsin (UW), which was previously flown to study the diffuse cosmic X-ray background. The Si thermistor detectors for that project required 130 K shielded JFET electronic components that are much less sensitive to the external field of the ADR solenoid than are the 1st ({approx}70 mK) and 2nd ({approx}2 K) SQUID stages used with TESs for solar observations. Modification of the Wisconsin ADR design, including TES focal plane and electronics re-positioning, therefore requires a tradeoff between the existing ADR solenoid nulling coil geometry and a low mass passive solenoid shield, while preserving the vibration isolation features of the existing design. We have developed models to accurately compute the magnetic field with and without shielding or nulling coils at critical locations to guide the re-design of the detector subsystem. The models and their application are described.

  10. Preliminary investigation of force-reduced superconducting magnet configurations for advanced technology applications

    SciTech Connect

    Bouillard, J.X.

    1992-12-01

    The feasibility of new high-field low specific weight superconducting magnet designs using force-free fields is being explored analytically and numerically. This report attempts to assess the technical viability of force-free field concepts to produce high-field, low specific weight and large bore volume magnets, which could promote the use of high temperature superconductors. Several force-free/force-reduced magnet configurations are first reviewed, then discussed and assessed. Force-free magnetic fields, fields for which the current flows parallel to the field, have well-known mathematical solutions extending upon infinite domains. These solutions, however, are no longer force-free everywhere for finite geometries. In this preliminary study, force-free solutions such as the Lundquist solutions truncated to a size where the internal field of the coil matches an externally cylindrical magnetic field (also called a Lundquist coil) are numerically modeled and explored. Significant force-reduction for such coils was calculated, which may have some importance for the design of lighter toroidal magnets used in thermonuclear fusion power generation, superconducting magnetic energy storage (SMES), and mobile MHD power generation and propulsion.

  11. CONFERENCE SUMMARY: Summary and comment on superconducting analogue electronics research, including materials and fabrication, as presented at ISEC 07

    NASA Astrophysics Data System (ADS)

    Foley, C. P.

    2007-11-01

    The main theme at ISEC 2007 for superconducting materials, fabrication and analogue electronics was the description of incremental developments, including a few new directions that indicate breakthroughs in this area of research. The work on applications focused on their cost-benefit analysis (in order to improve their appeal), the development of simpler systems, making more of the data collected, improving packaging and being responsive to the power handling requirements for commercial systems. All papers presenting this level of research highlighted the importance of obtaining all the necessary details in order to investigate analogue devices and the effectiveness and commercial viability of their systems. This stage of development is important if we are to achieve the transition of superconducting electronics from the laboratory to commercial use. There were some exciting disruptive breakthroughs reported. These were in the areas of nano-SQUIDs, rotating gradiometers, superconducting scanning tunnelling microscopy (Hayashi et al) and the potential of superconducting photonics using optical interfaces with superconducting vortex flow transistors, for example. The materials research in low (LTS), high (HTS) and medium (MTS) critical temperature superconductors was reported. In LTS, nitrides emerged as important materials for use as new tunnel barriers, either insulating or semiconducting. Papers on BaN, NbN, TaN, GaN and Nb-Si superconducting materials were also presented. The MTS material of MgB2 is still under development (Zhao et al). There were also new research groups from South Africa and Turkey attending the conference. The fabrication research presented covered the areas of critical current Ic spread, which is still an issue in reducing the reproducibility of Josephson junctions, a 150 mm process for Nb/Al-AlOx/Nb and methods to improve barrier layers using both new materials and smooth surfaces at thin film interfaces (Du et al). New methods to make sub

  12. Electronic structure and unusual superconducting properties of of CaAlSi and SrAlSi

    NASA Astrophysics Data System (ADS)

    Mazin, Igor I.; Papaconstantopoulos, Dimitris

    2004-03-01

    We report full-potential LAPW calculations for CaAlSi and SrAlSi in ordered structures and in the virtual crystal approximation, at normal and elevated pressures. We also estimate the electron-phonon coupling using either frozen-phon calculations at the zone center, or the rigid muffin tin approximation. We conclude that there is no simple way to explain the recently reported qualitative disparity in the superconducting properties of the two compounds. An assumption of an ultrasoft phonon mode, on the other hand, allows to reconcile in a reasonable way the experimental findings with the theory.

  13. Future opportunities for advancing glucose test device electronics.

    PubMed

    Young, Brian R; Young, Teresa L; Joyce, Margaret K; Kennedy, Spencer I; Atashbar, Massood Z

    2011-09-01

    Advancements in the field of printed electronics can be applied to the field of diabetes testing. A brief history and some new developments in printed electronics components applicable to personal test devices, including circuitry, batteries, transmission devices, displays, and sensors, are presented. Low-cost, thin, and lightweight materials containing printed circuits with energy storage or harvest capability and reactive/display centers, made using new printing/imaging technologies, are ideal for incorporation into personal-use medical devices such as glucose test meters. Semicontinuous rotogravure printing, which utilizes flexible substrates and polymeric, metallic, and/or nano "ink" composite materials to effect rapidly produced, lower-cost printed electronics, is showing promise. Continuing research advancing substrate, "ink," and continuous processing development presents the opportunity for research collaboration with medical device designers.

  14. Advanced accelerating structures and their interaction with electron beams.

    SciTech Connect

    Gai, W.; High Energy Physics

    2008-01-01

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  15. Advanced Accelerating Structures and Their Interaction with Electron Beams

    SciTech Connect

    Gai Wei

    2009-01-22

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  16. Future Opportunities for Advancing Glucose Test Device Electronics

    PubMed Central

    Young, Brian R; Young, Teresa L; Joyce, Margaret K; Kennedy, Spencer I; Atashbar, Massood Z

    2011-01-01

    Advancements in the field of printed electronics can be applied to the field of diabetes testing. A brief history and some new developments in printed electronics components applicable to personal test devices, including circuitry, batteries, transmission devices, displays, and sensors, are presented. Low-cost, thin, and lightweight materials containing printed circuits with energy storage or harvest capability and reactive/display centers, made using new printing/imaging technologies, are ideal for incorporation into personal-use medical devices such as glucose test meters. Semicontinuous rotogravure printing, which utilizes flexible substrates and polymeric, metallic, and/or nano “ink” composite materials to effect rapidly produced, lower-cost printed electronics, is showing promise. Continuing research advancing substrate, “ink,” and continuous processing development presents the opportunity for research collaboration with medical device designers. PMID:22027300

  17. Recent progress of the Los Alamos advanced free electron laser

    SciTech Connect

    Nguyen, D.C.; Austin, R.H.; Chan, K.C.D.; Feldman, D.W.; Goldstein, J.C.; Gierman, S.M.; Kinross-Wright, J.M.; Kong, S.H.; Plato, J.G.; Russell, S.J.

    1994-05-01

    Many industrial and research applications can benefit from the availability of a compact, user-friendly, broadly tunable and high average power free electron laser (FEL). Over the past four years, the Los Alamos Advanced FEL has been built with these design goals. The key to a compact FEL is the integration of advanced beam technologies such as a high-brightness photoinjector, a high-gradient compact linac, and permanent magnet beamline components. These technologies enable the authors to shrink the FEL size yet maintain its high average power capability. The Advanced FEL has been in operation in the near ir (4-6 {mu}m) since early 1993. Recent results of the Advanced FEL lasing at saturation and upgrades to improve its average power are presented.

  18. ELECTRON HOLOGRAPHY OF ELECTROMAGNETIC FIELDS - RECENT THEORETICAL ADVANCES.

    SciTech Connect

    BELEGGIA,M.; POZZI, G.; TONOMURA, A.

    2007-01-01

    It has been shown in this work that the Fourier space approach can be fruitfully applied to the calculation of the fields and the associated electron optical phase shift of several magnetic and electrostatic structures, like superconducting vortices in conventional and high-T{sub c} superconductors, reverse biased p-n junctions, magnetic domains and nanoparticles. In all these cases, this novel approach has led to unexpected but extremely interesting results, very often expressed in analytical form, which allow the quantitative and reliable interpretation of the experimental data collected by means of electron holography or of more conventional Lorentz microscopy techniques. Moreover, it is worth recalling that whenever long-range electromagnetic fields are involved, a physical model of the object under investigation is necessary in order to take into account correctly the perturbation of the reference wave induced by the tail of the field protruding into the vacuum. For these reasons, we believe that the Fourier space approach for phase computations we have introduced and discussed in this chapter will represent an invaluable tool for the investigation of electromagnetic fields at the meso- and nano-scale.

  19. The superconducting coil system of the advanced modular stellarator Wendelstein 7-X

    SciTech Connect

    Maurer, W.

    1994-11-01

    Wendelstein 7-X (W 7-X) is the largest stellarator experiment envisaged worldwide. It is prepared in the Max-Planck-Institute for Plasma Physics in Garching near Munich, Germany. The main goal of the experiment is demonstration of the optimized stellarator concept as an appropriate route for a fusion reactor. Essential physics and technical goals of this experiment are: demonstration of stationary operation, achievement of plasma parameters which allow a reliable prediction of the properties of a future stellarator reactor plasma without striving for ignition, and generation of the magnetic confinement with superconducting modular coils in a stellarator for the first time. The optimization criteria of the coil system are described and the status of the engineering development programme for the coils which is a common task of IPP and the nuclear research center KfK in Karlsruhe are reported.

  20. Experimental validation of advanced regulations for superconducting magnet cooling undergoing periodic heat loads

    SciTech Connect

    Lagier, B.; Rousset, B.; Hoa, C.; Bonnay, P.

    2014-01-29

    Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and the refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.

  1. Experimental validation of advanced regulations for superconducting magnet cooling undergoing periodic heat loads

    NASA Astrophysics Data System (ADS)

    Lagier, B.; Rousset, B.; Hoa, C.; Bonnay, P.

    2014-01-01

    Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and the refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.

  2. Materials Advances for Next-Generation Ingestible Electronic Medical Devices.

    PubMed

    Bettinger, Christopher J

    2015-10-01

    Electronic medical implants have collectively transformed the diagnosis and treatment of many diseases, but have many inherent limitations. Electronic implants require invasive surgeries, operate in challenging microenvironments, and are susceptible to bacterial infection and persistent inflammation. Novel materials and nonconventional device fabrication strategies may revolutionize the way electronic devices are integrated with the body. Ingestible electronic devices offer many advantages compared with implantable counterparts that may improve the diagnosis and treatment of pathologies ranging from gastrointestinal infections to diabetes. This review summarizes current technologies and highlights recent materials advances. Specific focus is dedicated to next-generation materials for packaging, circuit design, and on-board power supplies that are benign, nontoxic, and even biodegradable. Future challenges and opportunities are also highlighted.

  3. Lower hybrid current drive and ion cyclotron range of frequencies heating experiments in H-mode plasmas in Experimental Advanced Superconducting Tokomak

    SciTech Connect

    Zhang, X. J.; Wan, B. N. Zhao, Y. P.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Wukitch, S.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.

    2014-06-15

    An ion cyclotron range of frequencies (ICRF) system with power up to 6.0 MW and a lower hybrid current drive (LHCD) system up to 4 MW have been applied for heating and current drive experiments in Experimental Advanced Superconducting Tokomak (EAST). Significant progress has been made with ICRF heating and LHCD for realizing the H-mode plasma operation in EAST. During 2010 and 2012 experimental campaigns, ICRF heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H minority heating (H-MH) mode. The H-MH mode produced good plasma performance, and realized H-mode using ICRF power alone in 2012. In 2010, H-modes were generated and sustained by LHCD alone, where lithium coating and gas puffing near the mouth of the LH launcher were applied to improve the LHCD power coupling and penetration into the core plasmas of H-modes. In 2012, the combination of LHCD and ICRH power extended the H-mode duration up to over 30 s. H-modes with various types of edge localized modes (ELMs) have been achieved with H{sub IPB98}(y, 2) ranging from 0.7 to over unity. A brief overview of LHCD and ICRF Heating experiment and their application in achieving H-mode operation during these two campaigns will be presented.

  4. Applications and Advances in Electronic-Nose Technologies

    PubMed Central

    Wilson, Alphus D.; Baietto, Manuela

    2009-01-01

    Electronic-nose devices have received considerable attention in the field of sensor technology during the past twenty years, largely due to the discovery of numerous applications derived from research in diverse fields of applied sciences. Recent applications of electronic nose technologies have come through advances in sensor design, material improvements, software innovations and progress in microcircuitry design and systems integration. The invention of many new e-nose sensor types and arrays, based on different detection principles and mechanisms, is closely correlated with the expansion of new applications. Electronic noses have provided a plethora of benefits to a variety of commercial industries, including the agricultural, biomedical, cosmetics, environmental, food, manufacturing, military, pharmaceutical, regulatory, and various scientific research fields. Advances have improved product attributes, uniformity, and consistency as a result of increases in quality control capabilities afforded by electronic-nose monitoring of all phases of industrial manufacturing processes. This paper is a review of the major electronic-nose technologies, developed since this specialized field was born and became prominent in the mid 1980s, and a summarization of some of the more important and useful applications that have been of greatest benefit to man. PMID:22346690

  5. Testing aspects of advanced coherent electron cooling technique

    SciTech Connect

    Litvinenko, V.; Jing, Y.; Pinayev, I.; Wang, G.; Samulyak, R.; Ratner, D.

    2015-05-03

    An advanced version of the Coherent-electron Cooling (CeC) based on the micro-bunching instability was proposed. This approach promises significant increase in the bandwidth of the CeC system and, therefore, significant shortening of cooling time in high-energy hadron colliders. In this paper we present our plans of simulating and testing the key aspects of this proposed technique using the set-up of the coherent-electron-cooling proof-of-principle experiment at BNL.

  6. Architectural development of an advanced EVA Electronic System

    NASA Technical Reports Server (NTRS)

    Lavelle, Joseph

    1992-01-01

    An advanced electronic system for future EVA missions (including zero gravity, the lunar surface, and the surface of Mars) is under research and development within the Advanced Life Support Division at NASA Ames Research Center. As a first step in the development, an optimum system architecture has been derived from an analysis of the projected requirements for these missions. The open, modular architecture centers around a distributed multiprocessing concept where the major subsystems independently process their own I/O functions and communicate over a common bus. Supervision and coordination of the subsystems is handled by an embedded real-time operating system kernel employing multitasking software techniques. A discussion of how the architecture most efficiently meets the electronic system functional requirements, maximizes flexibility for future development and mission applications, and enhances the reliability and serviceability of the system in these remote, hostile environments is included.

  7. The preliminary tests of the superconducting electron cyclotron resonance ion source DECRIS-SC2.

    PubMed

    Efremov, A; Bekhterev, V; Bogomolov, S; Drobin, V; Loginov, V; Lebedev, A; Yazvitsky, N; Yakovlev, B

    2012-02-01

    A new compact version of the "liquid He-free" superconducting ECR ion source, to be used as an injector of highly charged heavy ions for the MC-400 cyclotron, is designed and built at the Flerov Laboratory of Nuclear Reactions in collaboration with the Laboratory of High Energy Physics of JINR. The axial magnetic field of the source is created by the superconducting magnet and the NdFeB hexapole is used for the radial plasma confinement. The microwave frequency of 14 GHz is used for ECR plasma heating. During the first tests, the source shows a good enough performance for the production of medium charge state ions. In this paper, we will present the design parameters and the preliminary results with gaseous ions.

  8. SUPERCONDUCTING PHOTOINJECTOR

    SciTech Connect

    BEN-ZVI,I.; BURRILL, A.; CALAGA, R.; CHANG, X.; GROVER, R.; GUPTA, R.; HAHN, H.; HAMMONS, L.; KAYRAN, D.; KEWISCH, J.; LAMBIASE, R.; LITVINENKO, V.; MCINTYRE, G.; NAIK, D.; PATE, D.; PHILLIPS, D.; POZDEYEV, E.; RAO, T.; SMEDLEY, J.; THAN, R.; TODD, R.; WEISS, D.; WU, Q.; ZALTSMAN, A.; ET AL.

    2007-08-26

    One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at up to a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders..

  9. Advances in development of Nb3Sn superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Posen, Sam; Liepe, Matthias

    2014-11-01

    A 1.3 GHz Nb3Sn superconducting radio-frequency cavity prepared with a modified annealing step reached Bp k>50 mT , well above Bc 1=25 ±7 mT , without the strong Q -slope observed in previous Nb3Sn cavities. At 4.2 K, it has a Q0 of approximately 1 ×1 010 at >10 MV /m , far outperforming Nb at useable gradients. At 2 K, quench occurred at ˜55 mT , apparently due to a defect, so additional treatment may increase the maximum gradient. Material parameters of the coating were extracted from Q vs T data, including a Tc of 18.0 ±0.1 K , close to the maximum literature value. High power pulses were used to reach fields far higher than in CW measurements, and near Tc, quench fields close to the superheating field were observed. Based on a review of previous experience with Nb3Sn cavities, a speculative mechanism involving weak link grain boundaries is presented to explain how the modified annealing step could be the cause of the absence of strong Q -slope. Finally, an analysis of the progress to date provides hints that the path forward for Nb3Sn cavities should focus on minimizing defects.

  10. High resolution X-ray CT for advanced electronics packaging

    NASA Astrophysics Data System (ADS)

    Oppermann, M.; Zerna, T.

    2017-02-01

    Advanced electronics packaging is a challenge for non-destructive Testing (NDT). More, smaller and mostly hidden interconnects dominate modern electronics components and systems. To solve the demands of customers to get products with a high functionality by low volume, weight and price (e.g. mobile phones, personal medical monitoring systems) often the designers use System-in-Package solutions (SiP). The non-destructive testing of such devices is a big challenge. So our paper will impart fundamentals and applications for non-destructive evaluation of inner structures of electronics packaging for quality assurance and reliability investigations with a focus on X-ray methods, especially on high resolution X-ray computed tomography (CT).

  11. Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films.

    PubMed

    He, Shaolong; He, Junfeng; Zhang, Wenhao; Zhao, Lin; Liu, Defa; Liu, Xu; Mou, Daixiang; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2013-07-01

    The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.

  12. Superconductivity and metallic behavior in Pb{sub x}C{sub y}O{sub δ} structures prepared by focused electron beam induced deposition

    SciTech Connect

    Winhold, M. Weirich, P. M.; Schwalb, C. H.; Huth, M.

    2014-10-20

    Focused electron beam induced deposition as a direct-write approach possesses great potential to meet the demands for superconducting nanostructure fabrication especially regarding its 3D patterning capabilities combined with the high resolution in the nanometer regime. So far, however, it was not possible to fabricate superconducting structures with this technique. In this work, we present a lead-based superconductor prepared by focused electron beam induced deposition by dissociation of the precursor tetraethyllead. The as-grown structures exhibit metallic behavior and a minimum resistivity in the normal state of ρ = 16 μΩcm at T = 9 K followed by a superconducting transition at T{sub c} = 7.2 K.

  13. Size effect of strong-coupled superconducting In{sub 2}Bi nanoparticles: An investigation of short-range electron phonon coupling

    SciTech Connect

    Lin, Po-Yu; Gandhi, Ashish Chhaganlal; Wu, Sheng Yun

    2015-05-07

    We report the influence of the nanosized effect on the superconducting properties of bimetallic In{sub 2}Bi nanoparticles. In this study, the temperature- and applied magnetic field-dependence of the magnetization were utilized to investigate the electron-phonon coupling effect while controlling particle sizes 〈d〉 from 21(2) to 42(5) nm. As the particle size decreases, the electron-phonon constant λ{sub EP} decreases rapidly, signaling the short-range electron-phonon coupling effect which acts to confine the electrons within a smaller volume, thereby giving rise to a higher superconducting transition temperature T{sub C}. An enhanced superconducting transition was observed from the temperature dependence of magnetization, revealing a main diamagnetic Meissner state below T{sub C} ∼ 5.72(5) K for 〈d〉 = 31(1) nm In{sub 2}Bi nanoparticles. The variation of the T{sub C} is very sensitive to the particle size, which might be due to crystallinity and size uniformity of the samples. The electron-phonon coupling to low lying phonons is found to be the leading mechanism for the observed strong-coupling superconductivity in the In{sub 2}Bi system.

  14. Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates

    PubMed Central

    Giannetti, Claudio; Cilento, Federico; Conte, Stefano Dal; Coslovich, Giacomo; Ferrini, Gabriele; Molegraaf, Hajo; Raichle, Markus; Liang, Ruixing; Eisaki, Hiroshi; Greven, Martin; Damascelli, Andrea; van der Marel, Dirk; Parmigiani, Fulvio

    2011-01-01

    In strongly correlated systems the electronic properties at the Fermi energy (EF) are intertwined with those at high-energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high-energy scale physics associated with Mott-like excitations (|E−EF|>1 eV) is involved in the condensate formation. Here, we report the interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV, and the onset of HTSC. This is revealed by a novel optical pump-supercontinuum-probe technique that provides access to the dynamics of the dielectric function in Bi2Sr2Ca0.92Y0.08Cu2O8+δ over an extended energy range, after the photoinduced suppression of the superconducting pairing. These results unveil an unconventional mechanism at the base of HTSC both below and above the optimal hole concentration required to attain the maximum critical temperature (Tc). PMID:21673674

  15. Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates.

    PubMed

    Giannetti, Claudio; Cilento, Federico; Dal Conte, Stefano; Coslovich, Giacomo; Ferrini, Gabriele; Molegraaf, Hajo; Raichle, Markus; Liang, Ruixing; Eisaki, Hiroshi; Greven, Martin; Damascelli, Andrea; van der Marel, Dirk; Parmigiani, Fulvio

    2011-06-14

    In strongly correlated systems the electronic properties at the Fermi energy (E(F)) are intertwined with those at high-energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high-energy scale physics associated with Mott-like excitations (|E-E(F)|>1 eV) is involved in the condensate formation. Here, we report the interplay between the many-body high-energy CuO(2) excitations at 1.5 and 2 eV, and the onset of HTSC. This is revealed by a novel optical pump-supercontinuum-probe technique that provides access to the dynamics of the dielectric function in Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+δ) over an extended energy range, after the photoinduced suppression of the superconducting pairing. These results unveil an unconventional mechanism at the base of HTSC both below and above the optimal hole concentration required to attain the maximum critical temperature (T(c)).

  16. Superconductivity and its mechanism in an ab initio model for electron-doped LaFeAsO

    NASA Astrophysics Data System (ADS)

    Misawa, Takahiro; Imada, Masatoshi

    2014-12-01

    Two families of high-temperature superconductors whose critical temperatures are higher than 50 K are known. One are the copper oxides and the other are the iron-based superconductors. Comparisons of mechanisms between these two in terms of common ground as well as distinctions will greatly help in searching for higher Tc superconductors. However, studies on mechanisms for the iron family based on first principles calculations are few. Here we first show that superconductivity emerges in the state-of-the-art numerical calculations for an ab initio multi-orbital model of an electron-doped iron-based superconductor LaFeAsO, in accordance with experimental observations. Then the mechanism of the superconductivity is identified as enhanced uniform density fluctuations by one-to-one correspondence with the instability towards inhomogeneity driven by first-order antiferromagnetic and nematic transitions. Despite many differences, certain common features with the copper oxides are also discovered in terms of the underlying orbital-selective Mottness found in the iron family.

  17. Superconductivity and its mechanism in an ab initio model for electron-doped LaFeAsO.

    PubMed

    Misawa, Takahiro; Imada, Masatoshi

    2014-12-22

    Two families of high-temperature superconductors whose critical temperatures are higher than 50 K are known. One are the copper oxides and the other are the iron-based superconductors. Comparisons of mechanisms between these two in terms of common ground as well as distinctions will greatly help in searching for higher T(c) superconductors. However, studies on mechanisms for the iron family based on first principles calculations are few. Here we first show that superconductivity emerges in the state-of-the-art numerical calculations for an ab initio multi-orbital model of an electron-doped iron-based superconductor LaFeAsO, in accordance with experimental observations. Then the mechanism of the superconductivity is identified as enhanced uniform density fluctuations by one-to-one correspondence with the instability towards inhomogeneity driven by first-order antiferromagnetic and nematic transitions. Despite many differences, certain common features with the copper oxides are also discovered in terms of the underlying orbital-selective Mottness found in the iron family.

  18. Optimization of gaseous helium heater for 2 K cryogenic system for VECC’s superconducting electron linac

    NASA Astrophysics Data System (ADS)

    Ahammed, Manir; Ghosh, Siddhartha; Saha, Subrata; Singh, Sandeep Kumar; Bhattacharya, Tamal Kumar; DuttaGupta, Anjan; Pal, Gautam; Naik, Vaishali; Chakrabarti, Alok

    2014-09-01

    Niobium superconducting radiofrequency cavities are generally operated at around 2 K temperature to achieve a high quality factor by reducing residual surface losses. 2 K temperature is produce by lowering down the pressure of the helium by employing a sub-atmospheric vacuum pumping system. The cavities are immersed in liquid helium bath, maintained in the helium chamber. A special heater is optimized for warming up the helium gas coming out from the helium chamber to 300 K before it enters the pumping system. Keeping in view the uninterrupted and reliable operation of the superconducting electron linac and safe running of the liquid helium plant, a tubular heat exchanger type of heater is designed. Current is passed through the tubes of the heater so as to let the tube banks themselves act as heating element. He gas, passing through the tubes, absorbs the heat and warms up to the desired temperature. Unlike common notion, it has been observed that heater with longer length could reduce the requirement of the heater power but at the cost of extra pumping power, required to counter balance the excess pressure drop caused by the additional length of the heater. Pressure drop is kept within 50 Pa for 2 g/s helium flow rate. The whole lot of tubes, divided into 4 bundles, are electrically connected in series so that current rating of the feed-through could be kept within 750 A. This paper discusses the methodology used for optimizing the design of the heater.

  19. 78 FR 46621 - Status of the Office of New Reactors' Implementation of Electronic Distribution of Advanced...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-01

    ... COMMISSION Status of the Office of New Reactors' Implementation of Electronic Distribution of Advanced Reactor Correspondence AGENCY: Nuclear Regulatory Commission. ACTION: Implementation of electronic distribution of advanced reactor correspondence; issuance. SUMMARY: The U.S. Nuclear Regulatory Commission...

  20. Direct evidence for a magnetic f-electron-mediated pairing mechanism of heavy-fermion superconductivity in CeCoIn5.

    PubMed

    Van Dyke, John S; Massee, Freek; Allan, Milan P; Davis, J C Séamus; Petrovic, Cedomir; Morr, Dirk K

    2014-08-12

    To identify the microscopic mechanism of heavy-fermion Cooper pairing is an unresolved challenge in quantum matter studies; it may also relate closely to finding the pairing mechanism of high-temperature superconductivity. Magnetically mediated Cooper pairing has long been the conjectured basis of heavy-fermion superconductivity but no direct verification of this hypothesis was achievable. Here, we use a novel approach based on precision measurements of the heavy-fermion band structure using quasiparticle interference imaging to reveal quantitatively the momentum space (k-space) structure of the f-electron magnetic interactions of CeCoIn5. Then, by solving the superconducting gap equations on the two heavy-fermion bands Ek(α,β) with these magnetic interactions as mediators of the Cooper pairing, we derive a series of quantitative predictions about the superconductive state. The agreement found between these diverse predictions and the measured characteristics of superconducting CeCoIn5 then provides direct evidence that the heavy-fermion Cooper pairing is indeed mediated by f-electron magnetism.

  1. Advances in Electronic-Nose Technologies Developed for Biomedical Applications

    PubMed Central

    Wilson, Alphus D.; Baietto, Manuela

    2011-01-01

    The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry. PMID:22346620

  2. A beamline for high-pressure studies at the Advanced Light Source with a superconducting bending magnet as the source.

    PubMed

    Kunz, Martin; MacDowell, Alastair A; Caldwell, Wendel A; Cambie, Daniella; Celestre, Richard S; Domning, Edward E; Duarte, Robert M; Gleason, Arianna E; Glossinger, James M; Kelez, Nicholas; Plate, David W; Yu, Tony; Zaug, Joeseph M; Padmore, Howard A; Jeanloz, Raymond; Alivisatos, A Paul; Clark, Simon M

    2005-09-01

    A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 T superconducting bending magnet (superbend). Useful X-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness-preserving optics of the beamline. These optics are comprised of a plane parabola collimating mirror, followed by a Kohzu monochromator vessel with Si(111) crystals (E/DeltaE approximately equal 7000) and W/B4C multilayers (E/DeltaE approximately equal 100), and then a toroidal focusing mirror with variable focusing distance. The experimental enclosure contains an automated beam-positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detector (CCD or image-plate detector). Future developments aim at the installation of a second endstation dedicated to in situ laser heating and a dedicated high-pressure single-crystal station, applying both monochromatic and polychromatic techniques.

  3. Calibration of Fast Fiber-Optic Beam Loss Monitors for the Advanced Photon Source Storage Ring Superconducting Undulators

    SciTech Connect

    Dooling, J.; Harkay, K.; Ivanyushenkov, Y.; Sajaev, V.; Xiao, A.; Vella, Andrea K.

    2015-01-01

    We report on the calibration and use of fast fiber-optic (FO) beam loss monitors (BLMs) in the Advanced Photon Source storage ring (SR). A superconducting undulator prototype (SCU0) has been operating in SR Sector 6 (“ID6”) since the beginning of CY2013, and another undulator SCU1 (a 1.1-m length undulator that is three times the length of SCU0) is scheduled for installation in Sector 1 (“ID1”) in 2015. The SCU0 main coil often quenches during beam dumps. MARS simulations have shown that relatively small beam loss (<1 nC) can lead to temperature excursions sufficient to cause quenchingwhen the SCU0windings are near critical current. To characterize local beam losses, high-purity fused-silica FO cables were installed in ID6 on the SCU0 chamber transitions and in ID1 where SCU1 will be installed. These BLMs aid in the search for operating modes that protect the SCU structures from beam-loss-induced quenching. In this paper, we describe the BLM calibration process that included deliberate beam dumps at locations of BLMs. We also compare beam dump events where SCU0 did and did not quench.

  4. Simulation of fast-ion-driven Alfvén eigenmodes on the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Hu, Youjun; Todo, Y.; Pei, Youbin; Li, Guoqiang; Qian, Jinping; Xiang, Nong; Zhou, Deng; Ren, Qilong; Huang, Juan; Xu, Liqing

    2016-02-01

    Kinetic-MHD hybrid simulations are carried out to investigate possible fast-ion-driven modes on the Experimental Advanced Superconducting Tokamak. Three typical kinds of fast-ion-driven modes, namely, toroidicity-induced Alfvén eigenmodes, reversed shear Alfvén eigenmodes, and energetic-particle continuum modes, are observed simultaneously in the simulations. The simulation results are compared with the results of an ideal MHD eigenvalue code, which shows agreement with respect to the mode frequency, dominant poloidal mode numbers, and radial location. However, the modes in the hybrid simulations take a twisted structure on the poloidal plane, which is different from the results of the ideal MHD eigenvalue code. The twist is due to the radial phase variation of the eigenfunction, which may be attributed to the non-perturbative kinetic effects of the fast ions. By varying the stored energy of fast ions to change the fast ion drive in the simulations, it is demonstrated that the twist (i.e., the radial phase variation) is positively correlated with the fast ion drive.

  5. A Beamline for High-Pressure Studies at the Advanced Light Sourcewith a Superconducting Bending Magnet as the Source

    SciTech Connect

    Kunz, Martin; MacDowell, Alastair A.; Caldwell, Wendel A.; Cambie, Daniella; Celestre, Richard S.; Domning, Edward E.; Duarte,Robert M.; Gleason, Arianna E.; Glossinger, James M.; Kelez, Nicholas; Plate, David W.; Yu, Tony; Zaug, Joeseph M.; Padmore, Howard A.; Jeanloz,Raymond; Alivisatos, A. Paul; Clark, Simon M.

    2005-06-30

    A new facility for high-pressure diffraction andspectroscopy using diamond anvil high-pressure cells has been built atthe Advanced Light Source on Beamline 12.2.2. This beamline benefits fromthe hard X-radiation generated by a 6 Tesla superconducting bendingmagnet (superbend). Useful x-ray flux is available between 5 keV and 35keV. The radiation is transferred from the superbend to the experimentalenclosure by the brightness preserving optics of the beamline. Theseoptics are comprised of: a plane parabola collimating mirror (M1),followed by a Kohzu monochromator vessel with a Si(111) crystals (E/DE ~;7000) and a W/B4C multilayers (E/DE ~; 100), and then a toroidal focusingmirror (M2) with variable focusing distance. The experimental enclosurecontains an automated beam positioning system, a set of slits, ionchambers, the sample positioning goniometry and area detectors (CCD orimage-plate detector). Future developments aim at the installation of asecond end station dedicated for in situ laser-heating on one hand and adedicated high-pressure single-crystal station, applying bothmonochromatic as well as polychromatic techniques.

  6. A BEAMLINE FOR HIGH PRESSURE STUDIES AT THE ADVANCED LIGHT SOURCE WITH A SUPERCONDUCTING BENDING MAGNET AS THE SOURCE

    SciTech Connect

    Kunz, M; MacDowell, A A; Caldwell, W A; Cambie, D; Celestre, R S; Domning, E E; Duarte, R M; Gleason, A; Glossinger, J; Kelez, N; Plate, D W; Yu, T; Zaug, J M; Padmore, H A; Jeanloz, R; Alivisatos, A P; Clark, S M

    2005-04-19

    A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on Beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 Tesla superconducting bending magnet (superbend). Useful x-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness preserving optics of the beamline. These optics are comprised of: a plane parabola collimating mirror (M1), followed by a Kohzu monochromator vessel with a Si(111) crystals (E/{Delta}E {approx} 7000) and a W/B{sub 4}C multilayer (E/{Delta}E {approx} 100), and then a toroidal focusing mirror (M2) with variable focusing distance. The experimental enclosure contains an automated beam positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detectors (CCD or image-plate detector). Future developments aim at the installation of a second end station dedicated for in situ laser-heating on one hand and a dedicated high-pressure single-crystal station, applying both monochromatic as well as polychromatic techniques.

  7. A Beamline for High-Pressure Studies at the Advanced Light Sourcewith a Superconducting Bending Magnet as the Source

    SciTech Connect

    Kunz, Martin; MacDowell, Alastair A.; Caldwell, Wendel A.; Cambie, Daniella; Celestre, Richard S.; Domning, Edward E.; Duarte,Robert M.; Gleason, Arianna E.; Glossinger, James M.; Kelez, Nicholas; Plate, David W.; Yu, Tony; Zaug, Joeseph M.; Padmore, Howard A.; Jeanloz,Raymond; Alivisatos, A. Paul; Clark, Simon M.

    2005-06-30

    A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on Beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 Tesla superconducting bending magnet (superbend). Useful x-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness preserving optics of the beamline. These optics are comprised of: a plane parabola collimating mirror (M1), followed by a Kohzu monochromator vessel with a Si(111) crystals (E/DE {approx}7000) and a W/B4C multilayers (E/DE {approx} 100), and then a toroidal focusing mirror (M2) with variable focusing distance. The experimental enclosure contains an automated beam positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detectors (CCD or image-plate detector). Future developments aim at the installation of a second end station dedicated for in situ laser-heating on one hand and a dedicated high-pressure single-crystal station, applying both monochromatic as well as polychromatic techniques.

  8. Kinetic-MHD hybrid simulation of fishbone modes excited by fast ions on the experimental advanced superconducting tokamak (EAST)

    NASA Astrophysics Data System (ADS)

    Pei, Youbin; Xiang, Nong; Hu, Youjun; Todo, Y.; Li, Guoqiang; Shen, Wei; Xu, Liqing

    2017-03-01

    Kinetic-MagnetoHydroDynamic hybrid simulations are carried out to investigate fishbone modes excited by fast ions on the Experimental Advanced Superconducting Tokamak. The simulations use realistic equilibrium reconstructed from experiment data with the constraint of the q = 1 surface location (q is the safety factor). Anisotropic slowing down distribution is used to model the distribution of the fast ions from neutral beam injection. The resonance condition is used to identify the interaction between the fishbone mode and the fast ions, which shows that the fishbone mode is simultaneously in resonance with the bounce motion of the trapped particles and the transit motion of the passing particles. Both the passing and trapped particles are important in destabilizing the fishbone mode. The simulations show that the mode frequency chirps down as the mode reaches the nonlinear stage, during which there is a substantial flattening of the perpendicular pressure of fast ions, compared with that of the parallel pressure. For passing particles, the resonance remains within the q = 1 surface, while, for trapped particles, the resonant location moves out radially during the nonlinear evolution. In addition, parameter scanning is performed to examine the dependence of the linear frequency and growth rate of fishbones on the pressure and injection velocity of fast ions.

  9. Development of high-speed and wide-angle visible observation diagnostics on Experimental Advanced Superconducting Tokamak using catadioptric optics.

    PubMed

    Yang, J H; Yang, X F; Hu, L Q; Zang, Q; Han, X F; Shao, C Q; Sun, T F; Chen, H; Wang, T F; Li, F J; Hu, A L

    2013-08-01

    A new wide-angle endoscope for visible light observation on the Experimental Advanced Superconducting Tokamak (EAST) has been recently developed. The head section of the optical system is based on a mirror reflection design that is similar to the International Thermonuclear Experimental Reactor-like wide-angle observation diagnostic on the Joint European Torus. However, the optical system design has been simplified and improved. As a result, the global transmittance of the system is as high as 79.6% in the wavelength range from 380 to 780 nm, and the spatial resolution is <5 mm for the full depth of field (4000 mm). The optical system also has a large relative aperture (1:2.4) and can be applied in high-speed camera diagnostics. As an important diagnostic tool, the optical system has been installed on the HT-7 (Hefei Tokamak-7) for its final experimental campaign, and the experiments confirmed that it can be applied to the investigation of transient processes in plasma, such as ELMy eruptions in H-mode, on EAST.

  10. Modeling of advanced divertor configuration on experimental advanced superconducting tokamak by SOLPS5.0/B2.5-Eirene

    NASA Astrophysics Data System (ADS)

    Si, H.; Guo, H. Y.; Xu, G. S.; Xiao, B. J.; Luo, Z. P.; Guo, Y.; Wang, L.; Ding, R.

    2016-03-01

    Heat exhaust is one of the most challenging issues to be addressed for tokamak magnetic confinement fusion research. Detailed modeling with SOLPS5.0/B2.5-Eirene code package is carried out to examine an alternative advanced divertor configuration, i.e., quasi snowflake (QSF), for long pulse operation in EAST. Comparison is also made with the lower single null (LSN) divertor configuration. SOLPS predicts that the quasi snowflake configuration significantly reduces the peak heat flux at the lower divertor outer target, by a factor of 2-3, owing to the magnetic flux expansion. Furthermore, the density threshold for detachment is much lower for QSF, compared to LSN under the same upstream conditions. This indicates that QSF provides a promising tool for controlling heat flux at divertor target while maintaining a lower separatrix density, which is highly desirable for current drive, thus greatly facilitating long-pulse operation in EAST.

  11. 76 FR 12144 - Advanced Optics Electronics, Inc.; Order of Suspension of Trading

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-04

    ... COMMISSION Advanced Optics Electronics, Inc.; Order of Suspension of Trading March 2, 2011. It appears to the... securities of Advanced Optics Electronics, Inc. because it has not filed any periodic reports since the... of investors require a suspension of trading in Advanced Optics Electronics, Inc. Therefore, it...

  12. Superconducting properties of protactinium.

    PubMed

    Smith, J L; Spirlet, J C; Müller, W

    1979-07-13

    The superconducting transition temperature and upper critical magnetic field of protactinium were measured by alternating-current susceptibility techniques. Since the superconducting behavior of protactinium is affected by its 5f electron character, it is clear now that protactinium is a true actinide element.

  13. Production of low-Z ions in the Dresden superconducting electron ion beam source for medical particle therapy.

    PubMed

    Zschornack, G; Schwan, A; Ullmann, F; Grossmann, F; Ovsyannikov, V P; Ritter, E

    2012-02-01

    We report on experiments with a new superconducting electron beam ion source (EBIS-SC), the Dresden EBIS-SC, with the objective to meet the main requirements for their application in particle-therapy facilities. Synchrotrons as well as innovative accelerator concepts, such as high-gradient linacs which are driven by a large-current cyclotron (CYCLINACS) and direct drive RF linear accelerators may benefit from the advantages of EBISs in regard to their functional principle. First experimental studies of the production of low-Z ions such as H(+), H(2)(+), H(3)(+), C(4+), and C(6+) are presented. Particular attention is paid to the ion output, i.e., the number of ions per pulse and per second, respectively. Important beam parameters in this context are, among others, ion pulse shaping, pulse repetition rates, beam emittance, and ion energy spread.

  14. Studies of emittance of multiply charged ions extracted from high temperature superconducting electron cyclotron resonance ion source, PKDELIS

    SciTech Connect

    Rodrigues, G.; Lakshmy, P. S.; Kumar, Sarvesh; Mandal, A.; Kanjilal, D.; Roy, A.; Baskaran, R.

    2010-02-15

    For the high current injector project at Inter University Accelerator Centre, a high temperature superconducting electron cyclotron resonance (ECR) ion source, PKDELIS, would provide the high charge state ions. The emittance of the ECR ion source is an important parameter to design further beam transport system and to match the acceptances of the downstream radio frequency quadrupole and drift tube linac accelerators of the high current injector. The emittance of the analyzed beam of PKDELIS ECR source has been measured utilizing the three beam size technique. A slit and two beam profile monitors positioned at fixed distances from each other were used to measure the beam size. The digitized beam profiles have been analyzed to determine the emittance of various multiply charged ions. The variation of emittance with gas mixing, ultrahigh frequency power, and extraction energy are discussed in this presentation.

  15. Metal optics and superconductivity

    SciTech Connect

    Golovashkin, A.L.

    1989-01-01

    The articles contained in this collection are dedicated to the study of the electron structure of transition metals and superconducting alloys and compounds based on them. The study of the electron structure of materials is one of the central problems of solid-state physics and defines the solution of a number of problems. One of them is the problem of high-temperature superconductivity which has attracted exceptional attention from physicists in connection with the discovery of new classes of ceramic oxides which are superconducting at liquid-nitrogen temperature. The electron structure is one of the three whales on which all of superconductivity rests. It is frequently our ignorance of the electronic properties of a metal, alloy or compound in its normal state which makes it impossible to predict superconductivity in the material, preventing use from calculating the parameters of the superconducting state. There are now a number of effective methods for investigation of the electron structure of the metals and allows. This collection discusses metal optics, tunneling and magnetic measurements in superconductors. These methods are quite informative and allow us to obtain many important electron characteristics and temperature relations. Various characteristics of the superconducting compounds Nb{sub 3}Ge, Nb{sub 3}Al, nb{sub 3}Sn and Nb{sub 3}Ga with A15 structure and NbN with B1 structure, having rather high critical temperatures, are experimentally studied.

  16. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Austin, R.H.; Chan, K.C.D.

    1993-09-01

    The Los Alamos compact Advanced FEL has lased at 4.7 and 5.2 {mu}m with a 1-cm period wiggler and a high-brightness electron beam at 16.8 and 15.8 MeV, respectively. The measured electron beam normalized emittance is 1.7 {pi}{center_dot}mm{center_dot}mrad at a peak current of 100 A, corresponding to a beam brightness greater than 2 {times} 10{sup 12} A/m{sup 2}rad{sup 2}. Initial results indicate that the AFEL small signal gain is {approximately}8% at 0.3 nC (30 A peak). The maximum output energy is 7 mJ over a 2-{mu}s macropulse. The AFEL performance can be significantly enhanced by improvements in the rf and drive laser stability.

  17. Radiation-Hardened Electronics for Advanced Communications Systems

    NASA Technical Reports Server (NTRS)

    Whitaker, Sterling

    2015-01-01

    Novel approach enables high-speed special-purpose processors Advanced reconfigurable and reprogrammable communication systems will require sub-130-nanometer electronics. Legacy single event upset (SEU) radiation-tolerant circuits are ineffective at speeds greater than 125 megahertz. In Phase I of this project, ICs, LLC, demonstrated new base-level logic circuits that provide SEU immunity for sub-130-nanometer high-speed circuits. In Phase II, the company developed an innovative self-restoring logic (SRL) circuit and a system approach that provides high-speed, SEU-tolerant solutions that are effective for sub-130-nanometer electronics scalable to at least 22-nanometer processes. The SRL system can be used in the design of NASA's next-generation special-purpose processors, especially reconfigurable communication processors.

  18. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

    SciTech Connect

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J.-M.; Zasadzinski, J. F.

    2015-04-21

    Nanoscale defect structure within the magnetic penetration depth of ∼100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120 °C baking. Furthermore, we demonstrate that adding 800 °C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120 °C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120 °C bake.

  19. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J.-M.; Zasadzinski, J. F.

    2015-04-01

    Nanoscale defect structure within the magnetic penetration depth of ˜100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120 °C baking. Furthermore, we demonstrate that adding 800 °C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120 °C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120 °C bake.

  20. A nanoemitter based on a superconducting material

    NASA Astrophysics Data System (ADS)

    Hou, Jin-Long; Chang, Wei-Tse; Shih, Chih-Chiang; Yu, Yu-Fong; Fu, Tsu-Yi; Hwang, Ing-Shouh

    2016-06-01

    The coherence of an electron beam is crucial for the performance of electron microscopy, coherent diffractive imaging, holography, and many other advanced instrumentation methods that rely on the phase coherence of electron waves. Here we present a reliable method for preparing a niobium nanoemitter, which is thermally and chemically stable. The tip apex is a (100) facet with a lateral dimension of ˜1 nm, surrounded by four (310) facets. Adsorption of one monolayer of noble gas, particularly Xe, onto the nanoemitter greatly enhances the emission current and current stability. This electron source will probably possess both spatial and temporal coherence if the emitter is cooled below the superconducting temperature.

  1. Low-noise 1.5 THz waveguide-type hot-electron bolometer mixers using relatively thick NbTiN superconducting film

    NASA Astrophysics Data System (ADS)

    Shiino, Tatsuya; Furuya, Ryuta; Soma, Tatsuya; Watanabe, Yoshimasa; Sakai, Takeshi; Jiang, Ling; Maezawa, Hiroyuki; Yamakura, Tetsuya; Sakai, Nami; Yamamoto, Satoshi

    2015-03-01

    We have developed waveguide-type low-noise superconducting hot-electron bolometer (HEB) mixers for astronomical observations in the 1.3-1.5 THz region by using a relatively thick NbTiN superconducting film (10.8 nm). We have achieved a receiver noise temperature of 490 K (DSB: double side band) at 1.475 THz. This noise temperature corresponds to seven times the quantum noise. According to gain bandwidth measurements, the contribution of diffusion cooling is found to be responsible for such a good noise performance.

  2. HOM damping properties of fundamental power couplers in the superconducting electron gun of the energy recovery LINAC at Brookhaven National Laboratory

    SciTech Connect

    Hammons, L.; Hahn, H.

    2011-03-28

    Among the accelerator projects under construction at the Relativistic Heavy Ion Collider (RHIC) is an R and D energy recovery LINAC (ERL) test facility. The ERL includes both a five-cell superconducting cavity as well as a superconducting, photoinjector electron gun. Because of the high-charge and high-current demands, effective higher-order mode (HOM) damping is essential, and several strategies are being pursued. Among these is the use of the fundamental power couplers as a means for damping some HOMs. Simulation studies have shown that the power couplers can play a substantial role in damping certain HOMs, and this presentation discusses these studies along with measurements.

  3. Heavy-ion injector based on an electron cyclotron ion source for the superconducting linear accelerator of the Rare Isotope Science Project

    SciTech Connect

    Hong, In-Seok Kim, Yong-Hwan; Choi, Bong-Hyuk; Choi, Suk-Jin; Park, Bum-Sik; Jin, Hyun-Chang; Kim, Hye-Jin; Heo, Jeong-Il; Kim, Deok-Min; Jang, Ji-Ho

    2016-02-15

    The injector for the main driver linear accelerator of the Rare Isotope Science Project in Korea, has been developed to allow heavy ions up to uranium to be delivered to the inflight fragmentation system. The critical components of the injector are the superconducting electron cyclotron resonance (ECR) ion sources, the radio frequency quadrupole (RFQ), and matching systems for low and medium energy beams. We have built superconducting magnets for the ECR ion source, and a prototype with one segment of the RFQ structure, with the aim of developing a design that can satisfy our specifications, demonstrate stable operation, and prove results to compare the design simulation.

  4. Heavy-ion injector based on an electron cyclotron ion source for the superconducting linear accelerator of the Rare Isotope Science Project.

    PubMed

    Hong, In-Seok; Kim, Yong-Hwan; Choi, Bong-Hyuk; Choi, Suk-Jin; Park, Bum-Sik; Jin, Hyun-Chang; Kim, Hye-Jin; Heo, Jeong-Il; Kim, Deok-Min; Jang, Ji-Ho

    2016-02-01

    The injector for the main driver linear accelerator of the Rare Isotope Science Project in Korea, has been developed to allow heavy ions up to uranium to be delivered to the inflight fragmentation system. The critical components of the injector are the superconducting electron cyclotron resonance (ECR) ion sources, the radio frequency quadrupole (RFQ), and matching systems for low and medium energy beams. We have built superconducting magnets for the ECR ion source, and a prototype with one segment of the RFQ structure, with the aim of developing a design that can satisfy our specifications, demonstrate stable operation, and prove results to compare the design simulation.

  5. Magnetic Relaxation of Superconducting Quantum Dot and Tunneling of Electron in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Gulevich, D. R.; Kusmartsev, F. V.

    Quantum tunneling of vortices had been found to be an important novel phenomena for description of low temperature creep in high temperature superconductors (HTSCs). We speculate that quantum tunneling may be also exhibited in mesoscopic superconductors due to vortices trapped by the Bean-Livingston barrier. The London approximation and method of images is used to estimate the shape of the potential well in superconducting HTSC quantum dot. To calculate the escape rate we use the instanton technique. We model the vortex by a quantum particle tunneling from a two-dimensional ground state under magnetic field applied in the transverse direction. The resulting decay rates obtained by the instanton approach and conventional WKB are compared revealing complete coincidence with each other.

  6. Magnetic Relaxation of Superconducting Quantum Dot and Tunneling of Electron in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Gulevich, D. R.; Kusmartsev, F. V.

    2010-12-01

    Quantum tunneling of vortices had been found to be an important novel phenomena for description of low temperature creep in high temperature superconductors (HTSCs). We speculate that quantum tunneling may be also exhibited in mesoscopic superconductors due to vortices trapped by the Bean-Livingston barrier. The London approximation and method of images is used to estimate the shape of the potential well in superconducting HTSC quantum dot. To calculate the escape rate we use the instanton technique. We model the vortex by a quantum particle tunneling from a two-dimensional ground state under magnetic field applied in the transverse direction. The resulting decay rates obtained by the instanton approach and conventional WKB are compared revealing complete coincidence with each other.

  7. Microscopic derivation of GL theory for magnetism and superconductivity in multiband electronic systems

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Vladimir; Vafek, Oskar

    2012-02-01

    The superconductivity in pnictides arises due to interband scattering between Cooper pairs belonging to hole and particle Fermi surfaces. The amplitude of the scattering, while weak at bare level, is enhanced under RG flow, and competes with the SDW to become the leading instability when the hole and particle FS's are nearly, but not perfectly, nested. This motivates us to construct a GL theory with multiple order parameters from the microscopic action. It allows us to study the two competing orders and their interplay including a possible coexistence. The presence of both attractive and repulsive pairing terms requires a novel approach to the derivation with imaginary terms in the action as one consequence. The construction of the GL theory is a two-step process, with RG flow to an intermediate cut-off scale, determined by the deviations from the nesting, as the first step.

  8. Comment on "Superconductivity in electron-doped layered TiNCl with variable interlayer coupling"

    NASA Astrophysics Data System (ADS)

    Harshman, Dale R.; Fiory, Anthony T.

    2014-11-01

    In their article, Zhang et al. [Phys. Rev. B 86, 024516 (2012), 10.1103/PhysRevB.86.024516] present a remarkable result for Ax(S) yTiNCl compounds (α -phase TiNCl partially intercalated with alkali A and optionally co-intercalated molecular species S ), finding the superconducting transition temperature Tc scales with d-1, where the spacing d between TiNCl-layered structures depends on intercalant thickness. Recognizing that this behavior indicates interlayer coupling, Zhang et al. cite, among other papers, the interlayer Coulombic pairing mechanism picture [Harshman et al., J. Phys.: Condens. Matter 23, 295701 (2011), 10.1088/0953-8984/23/29/295701]. This Comment shows that superconductivity occurs by interactions between the chlorine layers of the TiNCl structure and the layers containing Ax, wherein the transverse Ax-Cl separation distance ζ is smaller than d . In the absence of pair-breaking interactions, the optimal transition temperature is modeled by Tc 0∝(σ/A ) 1 /2ζ-1 , where σ /A is the fractional charge per area per formula unit. Particularly noteworthy are the rather marginally metallic trends in resistivities of Ax(S) yTiNCl , indicating high scattering rates, which are expected to partially originate from remote Coulomb scattering (RCS) from the Ax ions. By modeling a small fraction of the RCS as inducing pair breaking, taken to cut off exponentially with ζ , observations of Tc7 Å . Since a spatially separated alkali-ion layer is not formed in L i0.13TiNCl , the observed Tc of 5.9 K is attributed to an intergrowth phase related to TiN (Tc=5.6 K ).

  9. Optical layout and mechanical structure of polarimeter-interferometer system for Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Zou, Z. Y.; Liu, H. Q. Jie, Y. X.; Wang, Z. X.; Shen, J. S.; An, Z. H.; Yang, Y.; Zeng, L.; Wei, X. C.; Li, G. S.; Zhu, X.; Ding, W. X.; Brower, D. L.; Lan, T.

    2014-11-15

    A Far-InfaRed (FIR) three-wave POlarimeter-INTerferometer (POINT) system for measurement current density profile and electron density profile is under development for the EAST tokamak. The FIR beams are transmitted from the laser room to the optical tower adjacent to EAST via ∼20 m overmoded dielectric waveguide and then divided into 5 horizontal chords. The optical arrangement was designed using ZEMAX, which provides information on the beam spot size and energy distribution throughout the optical system. ZEMAX calculations used to optimize the optical layout design are combined with the mechanical design from CATIA, providing a 3D visualization of the entire POINT system.

  10. Optical layout and mechanical structure of polarimeter-interferometer system for Experimental Advanced Superconducting Tokamaka)

    NASA Astrophysics Data System (ADS)

    Zou, Z. Y.; Liu, H. Q.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Wang, Z. X.; Shen, J. S.; An, Z. H.; Yang, Y.; Zeng, L.; Wei, X. C.; Li, G. S.; Zhu, X.; Lan, T.

    2014-11-01

    A Far-InfaRed (FIR) three-wave POlarimeter-INTerferometer (POINT) system for measurement current density profile and electron density profile is under development for the EAST tokamak. The FIR beams are transmitted from the laser room to the optical tower adjacent to EAST via ˜20 m overmoded dielectric waveguide and then divided into 5 horizontal chords. The optical arrangement was designed using ZEMAX, which provides information on the beam spot size and energy distribution throughout the optical system. ZEMAX calculations used to optimize the optical layout design are combined with the mechanical design from CATIA, providing a 3D visualization of the entire POINT system.

  11. Optical layout and mechanical structure of polarimeter-interferometer system for Experimental Advanced Superconducting Tokamak.

    PubMed

    Zou, Z Y; Liu, H Q; Jie, Y X; Ding, W X; Brower, D L; Wang, Z X; Shen, J S; An, Z H; Yang, Y; Zeng, L; Wei, X C; Li, G S; Zhu, X; Lan, T

    2014-11-01

    A Far-InfaRed (FIR) three-wave POlarimeter-INTerferometer (POINT) system for measurement current density profile and electron density profile is under development for the EAST tokamak. The FIR beams are transmitted from the laser room to the optical tower adjacent to EAST via ∼20 m overmoded dielectric waveguide and then divided into 5 horizontal chords. The optical arrangement was designed using ZEMAX, which provides information on the beam spot size and energy distribution throughout the optical system. ZEMAX calculations used to optimize the optical layout design are combined with the mechanical design from CATIA, providing a 3D visualization of the entire POINT system.

  12. Arc Welders' pneumoconiosis: application of advanced scanning electron microscopy.

    PubMed

    Guidotti, T L; Abraham, J L; DeNee, P B; Smith, J R

    1978-01-01

    Study of lung tissue from necropsy of a 58-year-old arc welder with arc welders' pneumoconiosis, confirmed by history, chest radiography, and pathology, demonstrates the versatility and usefulness of new techniques in scanning electron microscopy (SEM). Secondary electron imaging, the most familiar SEM mode, showed heavy cellular infiltrates in alveoli, the interstitium, and within the interstices of loose whorled fibrotic nodules. Backscattered electron imaging, in which contrast is proportional to elemental atomic number, revealed intracellular metal particles not otherwise visible. Microprobe analysis, energy-dispersive x-ray spectrometry, mapped elemeental iron over the particle image and identified traces of silicon in the whorled nodules. Arc welders' pneumoconiosis appears to be more than a benign siderosis resulting from particulate iron deposition. Simultaneous exposure to other components of welding fumes may alter the pathologic picture, inducing a more complicated fibrotic reaction. The more recently developed advanced techniques of SEM are well suited to the study of pneumoconioses and other problems of heterogenous tissue and mixed chemical systems.

  13. Hot electron injector Gunn diode for advanced driver assistance systems

    NASA Astrophysics Data System (ADS)

    Förster, A.; Lepsa, M. I.; Freundt, D.; Stock, J.; Montanari, S.

    2007-06-01

    This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap AlxGa1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced.

  14. Electron-Phonon Coupling and Superconducting Critical Temperature of the YIr2Si2 and LaIr2Si2 High-Temperature Polymorphs from First-Principles

    NASA Astrophysics Data System (ADS)

    Billington, David; Nickau, Simon A. C.; Farley, Tom; Ward, Jack R.; Sperring, Rosie F.; Millichamp, Thomas E.; Ernsting, David; Dugdale, Stephen B.

    2014-04-01

    Ab initio calculations of the electronic structure and lattice-vibrational properties were performed on the superconducting high-temperature polymorphs of YIr2Si2 and LaIr2Si2. The electron-phonon coupling constants λep were found to be 0.61 and 0.56 for YIr2Si2 and LaIr2Si2, respectively. The superconducting critical temperatures estimated from the Allen-Dynes formula agree well with the available experimental data and indicate that the superconductivity in these compounds can be explained by intermediate strength electron-phonon coupling.

  15. Superconducting active impedance converter

    DOEpatents

    Ginley, David S.; Hietala, Vincent M.; Martens, Jon S.

    1993-01-01

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductor allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology.

  16. Superconducting active impedance converter

    DOEpatents

    Ginley, D.S.; Hietala, V.M.; Martens, J.S.

    1993-11-16

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductors allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology. 12 figures.

  17. Optically induced lattice deformations, electronic structure changes, and enhanced superconductivity in YBa2Cu3O6.48.

    PubMed

    Mankowsky, R; Fechner, M; Först, M; von Hoegen, A; Porras, J; Loew, T; Dakovski, G L; Seaberg, M; Möller, S; Coslovich, G; Keimer, B; Dhesi, S S; Cavalleri, A

    2017-07-01

    Resonant optical excitation of apical oxygen vibrational modes in the normal state of underdoped YBa2Cu3O6+x induces a transient state with optical properties similar to those of the equilibrium superconducting state. Amongst these, a divergent imaginary conductivity and a plasma edge are transiently observed in the photo-stimulated state. Femtosecond hard x-ray diffraction experiments have been used in the past to identify the transient crystal structure in this non-equilibrium state. Here, we start from these crystallographic features and theoretically predict the corresponding electronic rearrangements that accompany these structural deformations. Using density functional theory, we predict enhanced hole-doping of the CuO2 planes. The empty chain Cu dy(2)-z(2) orbital is calculated to strongly reduce in energy, which would increase c-axis transport and potentially enhance the interlayer Josephson coupling as observed in the THz-frequency response. From these results, we calculate changes in the soft x-ray absorption spectra at the Cu L-edge. Femtosecond x-ray pulses from a free electron laser are used to probe changes in absorption at two photon energies along this spectrum and provide data consistent with these predictions.

  18. Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF

    SciTech Connect

    Demiralp, E.; Dasgupta, S.; Goddard, W.A. III

    1995-08-09

    The highest T{sub c} organic superconductors all involve the organic molecule bis(ethylenedithio)tetrathiafulvalene (denoted as BEDT-TTF or ET) coupled with an appropriate acceptor. This leads to ET, ET{sup +}, or (ET){sub 2}{sup +} species in the crystal. Using ab initio Hartree-Fock calculations (6-31G** basis set), we show that ET deforms to a boat structure with an energy 28 meV (0.65 kcal/mol) lower than that of planar ET (D{sub 2} symmetry). On the other hand, ET{sup +} is planar. Thus, conduction in this system leads to a coupling between charge transfer and the boat deformation vibrational modes at 20 cm{sup -1} (ET) and 28 cm{sup -1} (ET{sup +}). We suggest that this electron-phonon coupling is responsible for the superconductivity and predict the isotope shifts ({delta}T{sub c}) for experimental tests of the electron-transfer boat-vibration (ET-BV) mechanism. The low frequency of this boat mode and its coupling to various lattice modes could explain the sensitivity of T{sub c} to defects, impurities, and pressure. We suggest that new higher temperature organic donors can be sought by finding modifications that change the frequency and stability of this boat distortion mode. 25 refs., 5 figs., 4 tabs.

  19. Evolution of magnetic and superconducting fluctuations with doping of high-T{sub c} superconductors : an electronic Raman scattering study.

    SciTech Connect

    Blumberg, G.

    1998-01-14

    For YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 3{+-}{delta}} superconductors, electronic Raman scattering from high- and low-energy excitations has been studied in relation to the hole doping level, temperature, and energy of the incident photons. For underdoped superconductors, it is concluded that short range antiferromagnetic (AF) correlations persist with hole doping and doped single holes are incoherent in the AF environment. Above the superconducting (SC) transition temperature T{sub c} the system exhibits a sharp Raman resonance of B{sub 1g} symmetry and about 75 meV energy and a pseudogap for electron-hole excitations below 75 meV, a manifestation of a partially coherent state forming from doped incoherent quasi-particles. The occupancy of the coherent state increases with cooling until phase ordering at T{sub c} produces a global SC state.

  20. Optically induced lattice deformations, electronic structure changes, and enhanced superconductivity in YBa2Cu3O6.48

    PubMed Central

    Mankowsky, R.; Fechner, M.; Först, M.; von Hoegen, A.; Porras, J.; Loew, T.; Dakovski, G. L.; Seaberg, M.; Möller, S.; Coslovich, G.; Keimer, B.; Dhesi, S. S.; Cavalleri, A.

    2017-01-01

    Resonant optical excitation of apical oxygen vibrational modes in the normal state of underdoped YBa2Cu3O6+x induces a transient state with optical properties similar to those of the equilibrium superconducting state. Amongst these, a divergent imaginary conductivity and a plasma edge are transiently observed in the photo-stimulated state. Femtosecond hard x-ray diffraction experiments have been used in the past to identify the transient crystal structure in this non-equilibrium state. Here, we start from these crystallographic features and theoretically predict the corresponding electronic rearrangements that accompany these structural deformations. Using density functional theory, we predict enhanced hole-doping of the CuO2 planes. The empty chain Cu dy2-z2 orbital is calculated to strongly reduce in energy, which would increase c-axis transport and potentially enhance the interlayer Josephson coupling as observed in the THz-frequency response. From these results, we calculate changes in the soft x-ray absorption spectra at the Cu L-edge. Femtosecond x-ray pulses from a free electron laser are used to probe changes in absorption at two photon energies along this spectrum and provide data consistent with these predictions. PMID:28345009

  1. High-Performance electronics at ultra-low power consumption for space applications: From superconductor to nanoscale semiconductor technology

    NASA Technical Reports Server (NTRS)

    Duncan, Robert V.; Simmons, Jerry; Kupferman, Stuart; McWhorter, Paul; Dunlap, David; Kovanis, V.

    1995-01-01

    A detailed review of Sandia's work in ultralow power dissipation electronics for space flight applications, including superconductive electronics, new advances in quantum well structures, and ultra-high purity 3-5 materials, and recent advances in micro-electro-optical-mechanical systems (MEMS) is presented. The superconductive electronics and micromechanical devices are well suited for application in micro-robotics, micro-rocket engines, and advanced sensors.

  2. Advanced analytical electron microscopy for alkali-ion batteries

    DOE PAGES

    Qian, Danna; Ma, Cheng; Meng, Ying Shirley; ...

    2015-01-01

    Lithium-ion batteries are a leading candidate for electric vehicle and smart grid applications. However, further optimizations of the energy/power density, coulombic efficiency and cycle life are still needed, and this requires a thorough understanding of the dynamic evolution of each component and their synergistic behaviors during battery operation. With the capability of resolving the structure and chemistry at an atomic resolution, advanced analytical transmission electron microscopy (AEM) is an ideal technique for this task. The present review paper focuses on recent contributions of this important technique to the fundamental understanding of the electrochemical processes of battery materials. A detailed reviewmore » of both static (ex situ) and real-time (in situ) studies will be given, and issues that still need to be addressed will be discussed.« less

  3. Advanced analytical electron microscopy for alkali-ion batteries

    SciTech Connect

    Qian, Danna; Ma, Cheng; Meng, Ying Shirley; More, Karren; Chi, Miaofang

    2015-01-01

    Lithium-ion batteries are a leading candidate for electric vehicle and smart grid applications. However, further optimizations of the energy/power density, coulombic efficiency and cycle life are still needed, and this requires a thorough understanding of the dynamic evolution of each component and their synergistic behaviors during battery operation. With the capability of resolving the structure and chemistry at an atomic resolution, advanced analytical transmission electron microscopy (AEM) is an ideal technique for this task. The present review paper focuses on recent contributions of this important technique to the fundamental understanding of the electrochemical processes of battery materials. A detailed review of both static (ex situ) and real-time (in situ) studies will be given, and issues that still need to be addressed will be discussed.

  4. New Millennium DS2 electronic packaging an advanced electronic packaging "sandbox".

    NASA Astrophysics Data System (ADS)

    Arakaki, G.; D'Agostino, S.

    New Millennium Deep Space 2 (DS2), managed by the Jet Propulsion Laboratory (JPL), consists of a pair of probes that will be carried to Mars by the Mars Polar Lander. After release from the Lander, both probes enter the atmosphere, impact and penetrate the Martian surface. After impact, a soil sample is taken and analyzed for the presence of water. Other scientific data is collected during descent and after impact. The proposed size and mass of the probes imposed enormous constraints on the packaging of the electronics. To fit the electronics within the probe envelope, the DS2 became a virtual advanced packaging experiment: Chip-on-Board (COB) technology, High Density Interconnect (HDI) technology, and novel flexible interconnects were used in a highly integrated package to meet the requirements. This paper describes the development and testing of the DS2 electronics package and possible follow-on developments at JPL.

  5. Universality classes of metal-insulator transitions in strongly correlated electron systems and mechanism of high-temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Imada, Masatoshi

    2005-08-01

    We study three regimes of the Mott transitions characterized by classical, marginally quantum, and quantum. In the classical regime, the quantum degeneracy temperature is lower than the critical temperature of the Mott transition Tc , below which the first-order transition occurs. The quantum regime describes the Tc=0 boundary of the continuous transition. The marginal quantum region appears sandwiched by these two regimes. The classical transition is described by the Ising universality class. However, the Ginzburg-Landau-Wilson scheme breaks down when the quantum effects dominate. The marginal quantum critical region is categorized to an unusual universality class, where the order parameter exponent β , the susceptibility exponent γ , and the field exponent δ are given by β=d/2 , γ=2-d/2 , and δ=4/d , respectively, with d being the spatial dimensionality. It is shown that the transition is always at the upper critical dimension irrespective of the spatial dimensions. Therefore the mean-field exponents and the hyperscaling description become both valid at any dimension. The obtained universality classes agree with the recent experimental results on the Mott criticality in organic conductors such as κ-(ET)2Cu[N(CN)2]Cl and transition-metal compounds such as V2O3 . The marginal quantum criticality is characterized by the critically enhanced electron-density fluctuations at small wave number. The characteristic energy scale of the density fluctuation extends to the order of the Mott gap in contrast to the spin and orbital fluctuation scales and causes various unusual properties. The mode coupling theory shows that the marginal quantum criticality further generates non-Fermi-liquid properties in the metallic side. The effects of the long-range Coulomb force in the filling-control Mott transition are also discussed. A mechanism of high-temperature superconductivity emerges from the density fluctuations at small wave number inherent in the marginal quantum

  6. Electron Tunneling Studies of MOLYBDENUM(1-X) Rhenium(x): Enhancement of Superconductivity by a Resonance Mode.

    NASA Astrophysics Data System (ADS)

    Shum, Danny Pak-Chum

    It is well-known that a heavy impurity atom in a lattice of light atoms induces a lower frequency in-band resonance mode in the vibrational spectrum. The exact effect of such a mode on the lat- tice spectrum has not previously been reported and effects of such modes on superconductivity have not previously been described. Sputtered thin films of bcc Mo(,1-x)Re(,x), 0.2 < x < 0.4, have been pre- pared for this study because the Re atom is almost twice as heavy as Mo. High quality MoRe/Al(,2)O(,3)/Pb tunnel junctions on these films have been made with an in situ deposited and subsequently oxidized thin Al layer as barrier. Three phonon peaks were observed directly in the dV/dI and d('2)V/dI('2) curves. The (alpha)('2)F((omega)) spectra, determined from the data through the Eliashberg theory of superconductivity, all show an anomalous low energy peak, in addition to the Mo-derived transverse and longitudinal phonon peaks. This peak appears near 14 meV, in agreement with the Brout-Visscher theory and with neu- tron scattering data which first indicated the Re resonance mode in Mo(,.85)Re(,.15). We show that the resonance mode contributes strongly to (alpha)('2)F((omega)) and to strong coupling (delta)(=2(DELTA)/k(,B)T(,c) - 3.53) > 0. (delta) increases with (lamda)(,R), the Re contribution to the electron-phonon coupling con- stant (lamda). The dependences of the anomalous softening and width of the resonance mode on (lamda)(,R) fit the Yu-Anderson theory of local pho- non screening by a Fermi gas of electrons treated as Tomonago. bosons. These results explain the low N(0), high T(,c) behavior of Mo(,.6)Re(,.4). *DOE Report IS-T-1246. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.

  7. Advanced nanoimprint patterning for functional electronics and biochemical sensing

    NASA Astrophysics Data System (ADS)

    Wang, Chao

    Nano-fabrication has been widely used for a variety of disciplines, including electronics, material science, nano-optics, and nano-biotechnology. This dissertation focuses on nanoimprint lithography (NIL) based novel nano-patterning techniques for fabricating functional structures, and discusses their applications in advanced electronics and high-sensitivity molecular sensing. In this dissertation, examples of using nano-fabricated structures for promising electronic applications are presented. For instance, 10 nm and 18 nm features are NIL-fabricated for Si/SiGe heterojunction tunneling transistors and graphene nano-ribbon transistors, using shadow evaporation and line-width shrinking techniques, respectively. An ultrafast laser melting based method is applied on flexible plastic substrates to correct defects of nano-features. Nano-texturing of sapphire substrate is developed to improve the light extraction of GaN light emitting diodes (LEDs) by 70 %. A novel multi-layer nano-patterned Si-mediated catalyst is discovered to grow straight and uniform Si nanowires with optimized properties in size, location, and crystallization on amorphous SiO2 substrate. Nano-structures are also functionalized into highly sensitive bio-chemical sensors. Plasmonic nano-bar antenna arrays are demonstrated to effectively sense infrared molecules >10 times better than conventional plasmonic sensors. As small as 20 nm wide nano-channel fluidic devices are developed to linearize and detect DNA molecules for potential DNA sequencing. An integrated fluidic system is built to incorporate plasmonic nano-structures for 30X-enhanced fluorescence detection of large DNA molecules.

  8. Hartree-Fock Solutions of 2d Interacting Tight-Binding Electrons: Mott Properties and Room Temperature Superconductivity Indications

    NASA Astrophysics Data System (ADS)

    Cabo Montes de Oca, A.; March, N. H.; Cabo-Bizet, A.

    2014-12-01

    Former results for a tight-binding (TB) model of CuO planes in La2CuO4 are reinterpreted here to underline their wider implications. It is noted that physical systems being appropriately described by the TB model can exhibit the main strongly correlated electron system (SCES) properties, when they are solved in the HF approximation, by also allowing crystal symmetry breaking effects and noncollinear spin orientations of the HF orbitals. It is argued how a simple 2D square lattice system of Coulomb interacting electrons can exhibit insulator gaps and pseudogap states, and quantum phase transitions as illustrated by the mentioned former works. A discussion is also presented here indicating the possibility of attaining room temperature superconductivity, by means of a surface coating with water molecules of cleaved planes of graphite, being orthogonal to its c-axis. The possibility that 2D arrays of quantum dots can give rise to the same effect is also proposed to consideration. The analysis also furnishes theoretical insight to solve the Mott-Slater debate, at least for the La2CuO4 and TMO band structures. The idea is to apply a properly noncollinear GW scheme to the electronic structure calculation of these materials. The fact is that the GW approach can be viewed as a HF procedure in which the screening polarization is also determined. This directly indicates the possibility of predicting the assumed dielectric constant in the previous works. Thus, the results seem to identify that the main correlation properties in these materials are determined by screening. Finally, the conclusions also seem to be of help for the description of the experimental observations of metal-insulator transitions and Mott properties in atoms trapped in planar photonic lattices.

  9. Tuning the electronic and the crystalline structure of LaBi by pressure: From extreme magnetoresistance to superconductivity

    SciTech Connect

    Tafti, F. F.; Torikachvili, M. S.; Stillwell, R. L.; Baer, B.; Stavrou, E.; Weir, S. T.; Vohra, Y. K.; Yang, H. -Y.; McDonnell, E. F.; Kushwaha, S. K.; Gibson, Q. D.; Cava, R. J.; Jeffries, J. R.

    2017-01-01

    Extreme magnetoresistance (XMR) in topological semimetals is a recent discovery which attracts attention due to its robust appearance in a growing number of materials. To search for a relation between XMR and superconductivity, we study the effect of pressure on LaBi. By increasing pressure, we observe the disappearance of XMR followed by the appearance of superconductivity at P ≈ 3.5 GPa. We find a region of coexistence between superconductivity and XMR in LaBi in contrast to other superconducting XMR materials. The suppression of XMR is correlated with increasing zero-field resistance instead of decreasing in-field resistance. At higher pressures, P ≈ 11 GPa, we find a structural transition from the face-centered cubic lattice to a primitive tetragonal lattice, in agreement with theoretical predictions. The relationship between extreme magnetoresistance, superconductivity, and structural transition in LaBi is discussed.

  10. Tuning the electronic and the crystalline structure of LaBi by pressure: From extreme magnetoresistance to superconductivity

    NASA Astrophysics Data System (ADS)

    Tafti, F. F.; Torikachvili, M. S.; Stillwell, R. L.; Baer, B.; Stavrou, E.; Weir, S. T.; Vohra, Y. K.; Yang, H.-Y.; McDonnell, E. F.; Kushwaha, S. K.; Gibson, Q. D.; Cava, R. J.; Jeffries, J. R.

    2017-01-01

    Extreme magnetoresistance (XMR) in topological semimetals is a recent discovery which attracts attention due to its robust appearance in a growing number of materials. To search for a relation between XMR and superconductivity, we study the effect of pressure on LaBi. By increasing pressure, we observe the disappearance of XMR followed by the appearance of superconductivity at P ≈3.5 GPa. We find a region of coexistence between superconductivity and XMR in LaBi in contrast to other superconducting XMR materials. The suppression of XMR is correlated with increasing zero-field resistance instead of decreasing in-field resistance. At higher pressures, P ≈11 GPa, we find a structural transition from the face-centered cubic lattice to a primitive tetragonal lattice, in agreement with theoretical predictions. The relationship between extreme magnetoresistance, superconductivity, and structural transition in LaBi is discussed.

  11. Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation Using Superconducting Tunnel Junctions with Integrated Radio Frequency Single-Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Prober, D. E.; Rhee, K. W.; Schoelkopf, R. J.; Stahle, C. M.; Teufel, J.; Wollack, E. J.

    2004-01-01

    For high resolution imaging and spectroscopy in the FIR and submillimeter, space observatories will demand sensitive, fast, compact, low-power detector arrays with 104 pixels and sensitivity less than 10(exp -20) W/Hz(sup 0.5). Antenna-coupled superconducting tunnel junctions with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique. The device consists of an antenna to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure current through junctions contacting the absorber. We describe optimization of device parameters, and results on fabrication techniques for producing devices with high yield for detector arrays. We also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  12. The happy marriage between electron-phonon superconductivity and Mott physics in Cs3C60: A first-principle phase diagram

    NASA Astrophysics Data System (ADS)

    Capone, Massimo; Nomura, Yusuke; Sakai, Shiro; Giovannetti, Gianluca; Arita, Ryotaro

    The phase diagram of doped fullerides like Cs3C60 as a function of the spacing between fullerene molecules is characterized by a first-order transition between a Mott insulator and an s-wave superconductor with a dome-shaped behavior of the critical temperature. By means of an ab-initio modeling of the bandstructure, the electron-phonon interaction and the interaction parameter and a Dynamical Mean-Field Theory solution, we reproduce the phase diagram and demonstrate that phonon superconductivity benefits from strong correlations confirming earlier model predictions. The role of correlations is manifest also in infrared measurements carried out by L. Baldassarre. The superconducting phase shares many similarities with ''exotic'' superconductors with electronic pairing, suggesting that the anomalies in the ''normal'' state, rather than the pairing glue, can be the real common element unifying a wide family of strongly correlated superconductors including cuprates and iron superconductors

  13. Bulk Electronic Structure of Superconducting LaRu2P2 Single Crystals Measured by Soft-X-Ray Angle-Resolved Photoemission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Razzoli, E.; Kobayashi, M.; Strocov, V. N.; Delley, B.; Bukowski, Z.; Karpinski, J.; Plumb, N. C.; Radovic, M.; Chang, J.; Schmitt, T.; Patthey, L.; Mesot, J.; Shi, M.

    2012-06-01

    We present a soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it is significantly different from its counterpart in high-temperature superconducting Fe pnictides. In particular, the bandwidth renormalization present in the Fe pnictides (˜2-3) is negligible in LaRu2P2 even though the mass enhancement is similar in both systems. Our results suggest that the superconductivity in LaRu2P2 has a different origin with respect to the iron pnictides. Finally, we demonstrate that the increased probing depth of SX-ARPES, compared to the widely used ultraviolet ARPES, is essential in determining the bulk electronic structure in the experiment.

  14. The Commercial Opportunities for New Advanced Electronic Materials

    DTIC Science & Technology

    1989-08-07

    perovskite structure. Superconducting materials and dopings. The band-gap structure of the layers consist of complex linked arrays of perovskite cells ...its con parts only. The annual turnover for the solar cells OFF value. The importance of this device is that small alone is estimated to exceed $50...outer surface of a cyl- energy into electrical energy. Present day solar cells con- indrical drum. The properties required for an ideal vert 12-13

  15. Electron-phonon coupling in superconducting β-PdBi{sub 2}

    SciTech Connect

    Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini

    2015-06-24

    We have studied the electronic, transport and vibrational properties of low temperature superconductor β-PdBi{sub 2}. The band manifold clearly demonstrates the 2D-layered structure with multiple gaps. The intersection of bands at E{sub F} in the Γ-P, Γ-N directions gives rise to complicated Fermi surface topology, which contains quite complicated multiple connected sheets, as well as hole and electron-like pockets. From the low temperature specific heat, we have estimated the electron-phonon coupling constant λ{sub el-ph} which has a very high value of 3.66. The vibrational properties clearly illustrates that the strong coupling makes the lattice unstable. The calculated properties confirm that β-PdBi{sub 2} is an intermediate coupling superconductor.

  16. Quantum teleportation and entanglement swapping of electron spins in superconducting hybrid structures

    SciTech Connect

    Bubanja, Vladimir

    2015-06-15

    We present schemes for quantum teleportation and entanglement swapping of electronic spin states in hybrid superconductor–normal-metal systems. The proposed schemes employ subgap transport whereby the lowest order processes involve Cooper pair-electron and double Cooper-pair cotunneling in quantum teleportation and entanglement swapping protocols, respectively. The competition between elastic cotunneling and Cooper-pair splitting results in the success probability of 25% in both cases. Described implementations of these protocols are within reach of present-day experimental techniques.

  17. Superconductivity in aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Kubozono, Yoshihiro; Goto, Hidenori; Jabuchi, Taihei; Yokoya, Takayoshi; Kambe, Takashi; Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L. T.; Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya

    2015-07-01

    'Aromatic hydrocarbon' implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (Kxpicene, five benzene rings). Its superconducting transition temperatures (Tc's) were 7 and 18 K. Recently, we found a new superconducting Kxpicene phase with a Tc as high as 14 K, so we now know that Kxpicene possesses multiple superconducting phases. Besides Kxpicene, we discovered new superconductors such as Rbxpicene and Caxpicene. A most serious problem is that the shielding fraction is ⩽15% for Kxpicene and Rbxpicene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of Tc that is clearly observed in some phases of aromatic hydrocarbon superconductors, suggesting behavior not explained by the standard BCS picture of superconductivity. In this article, we describe the present status of this research field, and discuss its future prospects.

  18. A fast-time-response extreme ultraviolet spectrometer for measurement of impurity line emissions in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Zhang, Ling; Xu, Zong; Wu, Zhenwei; Zhang, Pengfei; Wu, Chengrui; Gao, Wei; Shen, Junsong; Chen, Yingjie; Liu, Xiang; Wang, Yumin; Gong, Xianzu; Hu, Liqun; Chen, Junlin; Zhang, Xiaodong; Wan, Baonian; Li, Jiangang; Morita, Shigeru; Ohishi, Tetsutarou; Goto, Motoshi; Dong, Chunfeng; and others

    2015-12-15

    A flat-field extreme ultraviolet (EUV) spectrometer working in the 20-500 Å wavelength range with fast time response has been newly developed to measure line emissions from highly ionized tungsten in the Experimental Advanced Superconducting Tokamak (EAST) with a tungsten divertor, while the monitoring of light and medium impurities is also an aim in the present development. A flat-field focal plane for spectral image detection is made by a laminar-type varied-line-spacing concave holographic grating with an angle of incidence of 87°. A back-illuminated charge-coupled device (CCD) with a total size of 26.6 × 6.6 mm{sup 2} and pixel numbers of 1024 × 255 (26 × 26 μm{sup 2}/pixel) is used for recording the focal image of spectral lines. An excellent spectral resolution of Δλ{sub 0} = 3-4 pixels, where Δλ{sub 0} is defined as full width at the foot position of a spectral line, is obtained at the 80-400 Å wavelength range after careful adjustment of the grating and CCD positions. The high signal readout rate of the CCD can improve the temporal resolution of time-resolved spectra when the CCD is operated in the full vertical binning mode. It is usually operated at 5 ms per frame. If the vertical size of the CCD is reduced with a narrow slit, the time response becomes faster. The high-time response in the spectral measurement therefore makes possible a variety of spectroscopic studies, e.g., impurity behavior in long pulse discharges with edge-localized mode bursts. An absolute intensity calibration of the EUV spectrometer is also carried out with a technique using the EUV bremsstrahlung continuum at 20-150 Å for quantitative data analysis. Thus, the high-time resolution tungsten spectra have been successfully observed with good spectral resolution using the present EUV spectrometer system. Typical tungsten spectra in the EUV wavelength range observed from EAST discharges are presented with absolute intensity and spectral identification.

  19. A fast-time-response extreme ultraviolet spectrometer for measurement of impurity line emissions in the Experimental Advanced Superconducting Tokamak.

    PubMed

    Zhang, Ling; Morita, Shigeru; Xu, Zong; Wu, Zhenwei; Zhang, Pengfei; Wu, Chengrui; Gao, Wei; Ohishi, Tetsutarou; Goto, Motoshi; Shen, Junsong; Chen, Yingjie; Liu, Xiang; Wang, Yumin; Dong, Chunfeng; Zhang, Hongmin; Huang, Xianli; Gong, Xianzu; Hu, Liqun; Chen, Junlin; Zhang, Xiaodong; Wan, Baonian; Li, Jiangang

    2015-12-01

    A flat-field extreme ultraviolet (EUV) spectrometer working in the 20-500 Å wavelength range with fast time response has been newly developed to measure line emissions from highly ionized tungsten in the Experimental Advanced Superconducting Tokamak (EAST) with a tungsten divertor, while the monitoring of light and medium impurities is also an aim in the present development. A flat-field focal plane for spectral image detection is made by a laminar-type varied-line-spacing concave holographic grating with an angle of incidence of 87°. A back-illuminated charge-coupled device (CCD) with a total size of 26.6 × 6.6 mm(2) and pixel numbers of 1024 × 255 (26 × 26 μm(2)/pixel) is used for recording the focal image of spectral lines. An excellent spectral resolution of Δλ0 = 3-4 pixels, where Δλ0 is defined as full width at the foot position of a spectral line, is obtained at the 80-400 Å wavelength range after careful adjustment of the grating and CCD positions. The high signal readout rate of the CCD can improve the temporal resolution of time-resolved spectra when the CCD is operated in the full vertical binning mode. It is usually operated at 5 ms per frame. If the vertical size of the CCD is reduced with a narrow slit, the time response becomes faster. The high-time response in the spectral measurement therefore makes possible a variety of spectroscopic studies, e.g., impurity behavior in long pulse discharges with edge-localized mode bursts. An absolute intensity calibration of the EUV spectrometer is also carried out with a technique using the EUV bremsstrahlung continuum at 20-150 Å for quantitative data analysis. Thus, the high-time resolution tungsten spectra have been successfully observed with good spectral resolution using the present EUV spectrometer system. Typical tungsten spectra in the EUV wavelength range observed from EAST discharges are presented with absolute intensity and spectral identification.

  20. Analysis of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

    1996-01-01

    The prospects of a YBa2Cu3O7(delta)(YBCO) hot-electron bolometer (HEB) mixer for a THz heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate.

  1. Final Scientific/Technical Report: Electronics for Large Superconducting Tunnel Junction Detector Arrays for Synchrotron Soft X-ray Research

    SciTech Connect

    Warburton, William K

    2009-03-06

    Superconducting tunnel junction (STJ) detectors offer a an approach to detecting soft x-rays with energy resolutions 4-5 times better and at rates 10 faster than traditions semiconductor detectors. To make such detectors feasible, however, then need to be deployed in large arrays of order 1000 detectors, which in turn implies that their processing electronics must be compact, fully computer controlled, and low cost per channel while still delivering ultra-low noise performance so as to not degrade the STJ's performance. We report on our progress in designing a compact, low cost preamplifier intended for this application. In particular, we were able to produce a prototype preamplifier of 2 sq-cm area and a parts cost of less than $30 that matched the energy resolution of the best conventional system to date and demonstrated its ability to acquire an STJ I-V curve under computer control, the critical step for determining and setting the detectors' operating points under software control.

  2. RF Single Electron Transistor Readout Amplifiers for Superconducting Astronomical Detectors for X-Ray to Sub-mm Wavelengths

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas; Aassime, Abdelhanin; Delsing, Per; Frunzio, Luigi; Li, Li-Qun; Prober, Daniel; Schoelkopf, Robert; Segall, Ken; Wilson, Chris; Stahle, Carl

    2000-01-01

    We report progress on using a new type of amplifier, the Radio-Frequency Single-Electron Transistor (RF-SET), to develop multi-channel sensor readout systems for fast and sensitive readout of high impedance cryogenic photodetectors such as Superconducting Tunnel Junctions and Single Quasiparticle Photon Counters. Although cryogenic, these detectors are desirable because of capabilities not other-wise attainable. However, high impedances and low output levels make low-noise, high-speed readouts challenging, and large format arrays would be facilitated by compact, low-power, on-chip integrated amplifiers. Well-suited for this application are RF-SETs, very high performance electrometers which use an rf readout technique to provide 100 MHz bandwidth. Small size, low power, and cryogenic operation allow direct integration with detectors, and using multiple rf carrier frequencies permits simultaneous readout of 20-50 amplifiers with a common electrical connection. We describe both the first 2-channel demonstration of this wavelength division multiplexing technique for RF-SETs, and Charge-Locked-Loop operation with 100 kHz of closed-loop bandwidth.

  3. Production of superconducting 1.3-GHz cavities for the European X-ray Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Singer, W.; Brinkmann, A.; Brinkmann, R.; Iversen, J.; Matheisen, A.; Moeller, W.-D.; Navitski, A.; Reschke, D.; Schaffran, J.; Sulimov, A.; Walker, N.; Weise, H.; Michelato, P.; Monaco, L.; Pagani, C.; Wiencek, M.

    2016-09-01

    The production of over 800 1.3-GHz superconducting (SC) cavities for the European X-ray Free Electron Laser (EXFEL), the largest in the history of cavity fabrication, has now been successfully completed. In the past, manufacturing of SC resonators was only partly industrialized; the main challenge for the EXFEL production was transferring the high-performance surface treatment to industry. The production was shared by the two companies RI Research Instruments GmbH (RI) and Ettore Zanon S.p.A. (EZ) on the principle of "build to print". DESY provided the high-purity niobium and NbTi for the resonators. Conformity with the European Pressure Equipment Directive (PED) was developed together with the contracted notified body TUEV NORD. New or upgraded infrastructure has been established at both companies. Series production and delivery of fully-equipped cavities ready for cold rf testing was started in December 2012, and finished in December 2015. More than half the cavities delivered to DESY as specified (referred to "as received") fulfilled the EXFEL specification. Further improvement of low-performing cavities was achieved by supplementary surface treatment at DESY or at the companies. The final achieved average gradient exceeded the EXFEL specification by approximately 25%. In the following paper, experience with the 1.3-GHz cavity production for EXFEL is reported and the main lessons learned are discussed.

  4. Production of highly charged heavy ions by 18 GHz superconducting electron cyclotron resonance at Research Center for Nuclear Physics.

    PubMed

    Yorita, Tetsuhiko; Hatanaka, Kichiji; Fukuda, Mitsuhiro; Kibayashi, Mitsuru; Morinobu, Shunpei; Okamura, Hiroyuki; Tamii, Atsushi

    2010-02-01

    An 18 GHz superconducting electron cyclotron resonance ion source has been installed as a subject of the azimuthally varying field cyclotron upgrade project (K. Hatanaka et al., in Proceedings of the 17th International Conference on Cyclotrons and Their Applications, Tokyo, Japan, 18-22 October 2004, pp. 115-117), in order to increase beam currents and to extend the variety of ions. The production development of several ions has been performed since 2006 and some of them have already been used for user experiments [T. Yorita et al., Rev. Sci. Instrum. 79, 02A311 (2008)]. Further optimizations for each component such as the material of plasma electrode, material, and shape of bias probe and mirror field have been continued and more intense ion beams have been obtained for O, N, and Ar. For the purpose of obtaining highly charged Xe with several microamperes, the optimization of position and shape of plasma electrode and bias disk has also been done and highly charged Xe(32+) beam has been obtained successfully.

  5. Electronic inhomogeneities in the superconducting phase of CaFe1.96Ni0.04As2 single crystals

    NASA Astrophysics Data System (ADS)

    Dutta, Anirban; Kumar, Neeraj; Thamizhavel, A.; Gupta, Anjan K.

    2015-02-01

    Superconductivity in CaFe2-xNixAs2 emerges in close proximity to an antiferromagnetic (AFM) ordered parent state and the AFM phase overlaps with superconducting (SC) phase for a small range of x-values. We present scanning tunneling microscopy and spectroscopy study of an underdoped CaFe2-xNixAs2 single crystal in the vicinity of the boundary of the two phases. Both resistivity and magnetic susceptibility measurements show a superconducting TC of 15 K and from later we deduce a superconducting fraction of 1.2%. Topographic images show reasonably flat surface with signatures of atomic resolution. Spectra between 120 K and 20 K are spatially homogeneous and show signatures of spin density wave (SDW) gap. Below TC, spectra show significant spatial inhomogeneity with a depression in density of states in±5 meV energy range. Inhomogeneity reduces significantly as the temperature goes above TC and disappears completely far above TC. These observations are discussed in terms of an inhomogeneous electronic phase that may exist due to the vicinity of this composition to the SC dome boundary on the underdoped side of the phase diagram.

  6. Advanced fertility diagnosis in stallion semen using transmission electron microscopy.

    PubMed

    Pesch, Sandra; Bostedt, Hartwig; Failing, Klaus; Bergmann, Martin

    2006-02-01

    Routine semen analysis of stallions is based on light microscopy (LM). However, there are still a number of animals that are subfertile or even infertile not being identified with conventional semen analysis. The objective of this study was to investigate the suitability of transmission electron microscopy (TEM) for advanced fertility diagnosis in stallion. We examined ejaculates of 46 stallions with known fertility. Animals were divided into three different groups: group 1, fertile stallions (pregnant mares> or =70%, n=29); group 2, subfertile stallions (pregnant mares 10-69%, n=14); group 3, infertile stallions (pregnant mares<10%, n=3). Ejaculates were collected in spring 2002. Conventional semen analysis (volume, sperm concentration, motility, live:dead ratio and percentage of morphologically normal sperm) was immediately performed after semen collection. Ultrastructural analysis included the evaluation of 200 acrosomes, heads, midpieces and cross-sections of tails as well as 100 longitudinal sections of tails from every ejaculate. Using LM, we found a significant increase of morphological deviations from 24.5% (x ) in group 1 to 34.5% in group 2 and 73.5% in group 3. Using TEM, we found a significant increase of detached acrosomes from 6.1% in group 1 to 7.6% in group 2 and 21.4% in group 3. Deviations in tubule pattern were also increased (but not significant) from 2.7% in fertile and 2.8% in subfertile to 11.4% in infertile stallions as well as multiple tails from 1.9% in fertile to 2.0% in subfertile and 8.9% in infertile. Our data indicate that TEM is suitable for advanced fertility diagnostic in stallions, giving a connection between fertility and morphology. It suggests that the most likely reason for sub- and infertility in stallion in case of increased LM pathomorphology of semen are acrosomal alterations, especially detached acrosomes.

  7. First-principles study of the superconductivity in MgB2 bulk and in its bilayer thin film based on electron-phonon coupling

    NASA Astrophysics Data System (ADS)

    Morshedloo, T.; Roknabadi, M. R.; Behdani, M.

    2015-02-01

    In this paper, phonon-mediated superconductivity has been investigated in MgB2 bulk structure and bilayer thin film by using first-principles calculations. The electronic band structure, total and partial density of states (DOS and PDOS), phonon dispersion, isotropic Eliashberg function α2F(ω), and electron-phonon coupling have been calculated within the framework of density functional theory (DFT). Our results indicate that holes at the top of boron σ bands mainly and holes in the boron π band partially contribute to formation of coupled holes in superconductivity state. The density of states at the Fermi energy level is increased for MgB2 bilayer with respect to its bulk structure. According to the phonon dispersion and Eliashberg function curves, coupling considerably occurs between holes at the top of the boron σ band by means of optical phonon mode for both structures. This phonon mode has the E2g symmetry at the Г point. We obtain electron-phonon coupling constants of 0.74 and 0.91 for bulk and bilayer structures, respectively. By using the Allen-Dynes formula, we estimate superconducting transition temperature TC of 40 K for bulk and 48 K for the thin film.

  8. Advanced Power Electronic Interfaces for Distributed Energy Systems Part 1: Systems and Topologies

    SciTech Connect

    Kramer, W.; Chakraborty, S.; Kroposki, B.; Thomas, H.

    2008-03-01

    This report summarizes power electronic interfaces for DE applications and the topologies needed for advanced power electronic interfaces. It focuses on photovoltaic, wind, microturbine, fuel cell, internal combustion engine, battery storage, and flywheel storage systems.

  9. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, Harry Lawrence; Elliott, Thomas S.

    1998-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  10. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, Harry L.; Elliott, Thomas S.

    1997-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  11. Modeling and Optimization of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applicaitons

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.; Burns, M. J.; Kleinsasser, A. W.; Delin, K. A.; Vasquez, R. P.

    1996-01-01

    The development of a YBa(sub 2)Cu(sub 3)O(sub 7-(kronecker delta))(YBCO) hot-electron bolometer (HEB) quasioptical mixer for a 2.5 heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of heat diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated....a single sideband temperature of less than 2000k is predicted.

  12. Theory of the orbital Kondo effect with assisted hopping in strongly correlated electron systems: Parquet equations, superconductivity, and mass enhancement

    NASA Astrophysics Data System (ADS)

    Penc, K.; Zawadowski, A.

    1994-10-01

    The orbital Kondo effect is treated in a model where, additional to the conduction band, there are localized orbitals close to the Fermi energy. If the hopping between the conduction band and the localized heavy orbitals depends on the occupation of the atomic orbitals in the conduction band, then orbital Kondo correlation occurs. The noncommutative nature of the coupling required for the Kondo effect is formally due to the form factors associated with the assisted hopping, which in the momentum representation depends on the momenta of the conduction electrons involved. The leading logarithmic vertex corrections are due to the local Coulomb interaction between the electrons on the heavy orbital and in the conduction band. The renormalized vertex functions are obtained as a solution of a closed set of differential equations and they show power behavior. The amplitude of large renormalization is determined by an infrared cutoff due to finite energy and dispersion of the heavy particles. The enhanced assisted hopping rate results in mass enhancement and attractive interaction in the conduction band. The superconductivity transition temperature calculated is largest for the intermediate mass enhancement, m*/m~=2-3. For larger mass enhancement the small one-particle weight (Z) in the Green's function reduces the transition temperature, which may be characteristic for other models as well. The theory is developed for different one-dimensional and square-lattice models, but the applicability is not limited to them. In the one-dimensional case charge- and spin-density susceptibilities are also discussed. Good candidates for the heavy orbital are f bands in the heavy fermionic systems and nonbonding oxygen orbitals in high-temperature superconductors and different flatbands in the quasi-one-dimensional organic conductors.

  13. Using advanced electron microscopy for the characterization of catalytic materials

    NASA Astrophysics Data System (ADS)

    Pyrz, William D.

    Catalysis will continue to be vitally important to the advancement and sustainability of industrialized societies. Unfortunately, the petroleum-based resources that currently fuel the energy and consumer product needs of an advancing society are becoming increasingly difficult and expensive to extract as supplies diminish and the quality of sources degrade. Therefore, the development of sustainable energy sources and the improvement of the carbon efficiency of existing chemical processes are critical. Further challenges require that these initiatives are accomplished in an environmentally friendly fashion since the effects of carbon-based emissions are proving to be a serious threat to global climate stability. In this dissertation, materials being developed for sustainable energy and process improvement initiatives are studied. Our approach is to use materials characterization, namely advanced electron microscopy, to analyze the targeted systems at the nano- or Angstrom-scale with the goal of developing useful relationships between structure, composition, crystalline order, morphology, and catalytic performance. One area of interest is the complex Mo-V-M-O (M=Te, Sb, Ta, Nb) oxide system currently being developed for the selective oxidation/ammoxidation of propane to acrylic acid or acrylonitrile, respectively. Currently, the production of acrylic acid and acrylonitrile rely on propylene-based processes, yet significant cost savings could be realized if the olefin-based feeds could be replaced by paraffin-based ones. The major challenge preventing this feedstock replacement is the development of a suitable paraffin-activating catalyst. Currently, the best candidate is the Mo-V-Nb-Te-O complex oxide catalyst that is composed of two majority phases that are commonly referred to as M1 and M2. However, there is a limited understanding of the roles of each component with respect to how they contribute to catalyst stability and the reaction mechanism. Aberration

  14. Evolution of the Electronic State through the Reduction Annealing in Electron-Doped Pr1.3-xLa0.7CexCuO4+δ (x=0.10) Single Crystals: Antiferromagnetism, Kondo Effect, and Superconductivity

    NASA Astrophysics Data System (ADS)

    Adachi, Tadashi; Mori, Yosuke; Takahashi, Akira; Kato, Masatsune; Nishizaki, Terukazu; Sasaki, Takahiko; Kobayashi, Norio; Koike, Yoji

    2013-06-01

    The evolution of the electronic state through the reduction annealing has been investigated in electron-doped Pr1.3-xLa0.7CexCuO4+δ (x=0.10) single crystals with the so-called T' structure. From the ab-plane and c-axis electrical resistivity measurements in magnetic fields, it has been found that, through the reduction annealing, the strongly localized state of carriers accompanied by the antiferromagnetic (AF) pseudogap in the as-grown crystal changes to a metallic state bringing about the Kondo effect without AF pseudogap and to a superconducting state. These results are able to be understood in terms of a model based on the strong electron correlation. The complete removal of excess oxygen in the T'-cuprates is expected to result in the appearance of superconductivity in a wide range of the Ce concentration including the parent compound of x=0.

  15. Conversion gain and noise of niobium superconducting hot-electron-mixers

    NASA Technical Reports Server (NTRS)

    Ekstrom, Hans; Karasik, Boris S.; Kollberg, Erik L.; Yngvesson, Sigfrid

    1995-01-01

    A study has been done of microwave mixing at 20 GHz using the nonlinear (power dependent) resistance of thin niobium strips in the resistive state. Our experiments give evidence that electron-heating is the main cause of the nonlinear phenomenon. Also a detailed phenomenological theory for the determination of conversion properties is presented. This theory is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V-characteristic. Knowing the electron temperature relaxation time, and using parameters derived from the I-V-characteristic also allows us to predict the -3 dB IF bandwidth. Experimental results are in excellent agreement with the theoretical predictions. The requirements on the mode of operation and on the film parameters for minimizing the conversion loss (and even achieving conversion gain) are discussed in some detail. Our measurements demonstrate an intrinsic conversion loss as low as 1 dB. The maximum IF frequency defined for -3 dB drop in conversion gain, is about 80 MHz. Noise measurements indicate a device output noise temperature of about 50 K and SSB mixer noise temperature below 250 K. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies.

  16. Distinguishing S-plus-minus and S-plus-plus electron pairing symmetries by neutron spin resonances in superconducting Sodium-Iron-Cobalt-Arsenic (transitional temperature = 18 Kelvin)

    SciTech Connect

    Das, Tanmoy; Balatsky, Alexander V.; Zhang, Chenglin; Li, Haifeng; Su, Yiki; Nethertom, Tucker; Redding, Caleb; Carr, Scott; Schneidewind, Astrid; Faulhaber, Enrico; Li, Shiliang; Yao, Daoxin; Bruckel, Thomas; Dai, Pengchen; Sobolev, Oleg

    2012-06-05

    A determination of the superconducting (SC) electron pairing symmetry forms the basis for establishing a microscopic mechansim for superconductivity. For iron pnictide superconductors, the s{sup {+-}}-pairing symmetry theory predicts the presence of a sharp neutron spin resonance at an energy below the sum of hole and electron SC gap energies (E {le} 2{Delta}). Although the resonances have been observed for various iron pnictide superconductors, they are broad in energy and can also be interpreted as arising from the s{sup ++}-pairing symmetry with E {ge} 2{Delta}. Here we use inelastic neutron scattering to reveal a sharp resonance at E = 7 meV in the SC NaFe{sub 0.935}Co{sub 0.045}As (T{sub c} = 18 K). By comparing our experiments with calculated spin-excitations spectra within the s{sup {+-}} and s{sup ++}-pairing symmetries, we conclude that the resonance in NaFe{sub 0.935}Co{sub 0.045}As is consistent with the s{sup {+-}}-pairing symmetry, thus eliminating s{sup ++}-pairing symmetry as a candidate for superconductivity.

  17. Superconductive wire

    DOEpatents

    Korzekwa, David A.; Bingert, John F.; Peterson, Dean E.; Sheinberg, Haskell

    1995-01-01

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

  18. Superconductive wire

    DOEpatents

    Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

    1995-07-18

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

  19. Convergent Beam Electron Diffraction Study of Bi-BASED High Temperature Superconducting Layered Compounds

    NASA Astrophysics Data System (ADS)

    Zhang, X. F.; Yan, Y. F.; Fung, K. K.

    Cleaved specimens of layered compounds Bi2Sr2(CaCuO2)nCuO6, n = 0, 1 and 2 phases have been studied by convergent beam electron diffraction. The identity and the symmetry of the phases have been determined from the higher order Laue zone (HOLZ) rings and the symmetry of their [001] patterns. In the case of Bi2Sr2CuO6, the [001] axial periodicity corresponds to the component of the wave vector of the monoclinic modulation along the c axis. Widely different axial periodicities have been obtained. This is interpreted as the manifestation of the variation of the monoclinic modulation. The presence of basal stacking fault lowers the symmetry of the [001] pattern.

  20. Superconducting transistor

    DOEpatents

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  1. Superconductivity in graphite intercalation compounds

    DOE PAGES

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; ...

    2015-02-26

    This study examines the field of superconductivity in the class of materials known as graphite intercalation compounds which has a history dating back to the 1960s. This paper recontextualizes the field in light of the discovery of superconductivity in CaC₆ and YbC₆ in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how this relates to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic statesmore » and phonon modes are most important for superconductivity and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.« less

  2. Superconductivity in graphite intercalation compounds

    SciTech Connect

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P. M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

    2015-02-26

    This study examines the field of superconductivity in the class of materials known as graphite intercalation compounds which has a history dating back to the 1960s. This paper recontextualizes the field in light of the discovery of superconductivity in CaC₆ and YbC₆ in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how this relates to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  3. Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe1.94Co0.06)2As2

    NASA Astrophysics Data System (ADS)

    Kyung, W. S.; Huh, S. S.; Koh, Y. Y.; Choi, K.-Y.; Nakajima, M.; Eisaki, H.; Denlinger, J. D.; Mo, S.-K.; Kim, C.; Kim, Y. K.

    2016-12-01

    The superconducting transition temperature (TC) in a FeSe monolayer on SrTiO3 is enhanced up to 100 K (refs ,,,). High TC is also found in bulk iron chalcogenides with similar electronic structure to that of monolayer FeSe, which suggests that higher TC may be achieved through electron doping, pushing the Fermi surface (FS) topology towards leaving only electron pockets. Such an observation, however, has been limited to chalcogenides, and is in contrast to the iron pnictides, for which the maximum TC is achieved with both hole and electron pockets forming considerable FS nesting instability. Here, we report angle-resolved photoemission characterization revealing a monotonic increase of TC from 24 to 41.5 K upon surface doping on optimally doped Ba(Fe1-xCox)2As2. The doping changes the overall FS topology towards that of chalcogenides through a rigid downward band shift. Our findings suggest that higher electron doping and concomitant changes in FS topology are favourable conditions for the superconductivity, not only for iron chalcogenides, but also for iron pnictides.

  4. Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe1.94Co0.06)2As2.

    PubMed

    Kyung, W S; Huh, S S; Koh, Y Y; Choi, K-Y; Nakajima, M; Eisaki, H; Denlinger, J D; Mo, S-K; Kim, C; Kim, Y K

    2016-12-01

    The superconducting transition temperature (TC) in a FeSe monolayer on SrTiO3 is enhanced up to 100 K (refs ,,,). High TC is also found in bulk iron chalcogenides with similar electronic structure to that of monolayer FeSe, which suggests that higher TC may be achieved through electron doping, pushing the Fermi surface (FS) topology towards leaving only electron pockets. Such an observation, however, has been limited to chalcogenides, and is in contrast to the iron pnictides, for which the maximum TC is achieved with both hole and electron pockets forming considerable FS nesting instability. Here, we report angle-resolved photoemission characterization revealing a monotonic increase of TC from 24 to 41.5 K upon surface doping on optimally doped Ba(Fe1-xCox)2As2. The doping changes the overall FS topology towards that of chalcogenides through a rigid downward band shift. Our findings suggest that higher electron doping and concomitant changes in FS topology are favourable conditions for the superconductivity, not only for iron chalcogenides, but also for iron pnictides.

  5. Measurement of groove features and dimensions of the vertical test cathode and the choke joint of the superconducting electron gun cavity of the Energy Recovery LINAC

    SciTech Connect

    Hammons, L.; Ke, M.

    2011-10-13

    A testing program for the superconducting electron gun cavity that has been designed for the Energy Recovery LINAC is being planned. The goal of the testing program is to characterize the RF properties of the gun cavity at superconducting temperatures and, in particular, to study multipacting that is suspected to be occurring in the choke joint of the cavity where the vertical test cathode is inserted. The testing program will seek to understand the nature and cause of this multipacting and attempt to eliminate it, if possible, by supplying sufficient voltage to the cavity. These efforts are motivated by the multipacting issues that have been observed in the processing of the fine-grain niobium gun cavity. This cavity, which is being processed at Thomas Jefferson National Laboratory for Brookhaven, has encountered multipacting at a gradient of approximately 3 MV/m and, to date, has resisted efforts at elimination. Because of this problem, a testing program is being established here in C-AD that will use the large-grain niobium gun cavity that currently resides at Brookhaven and has been used for room-temperature measurements. The large-grain and fine-cavities are identical in every aspect of construction and only differ in niobium grain size. Thus, it is believed that testing and conditioning of the large-grain cavity should yield important insights about the fine-grain cavity. One element of this testing program involves characterizing the physical features of the choke joint of the cavity where the multipacting is believed to be occurring and, in particular the grooves of the joint. The configuration of the cavity and the vertical test cathode is shown in Figure 1. In addition, it is important to characterize the groove of the vertical test cathode. The grooved nature of these two components was specifically designed to prevent multipacting. However, it is suspected that, because of the chemical processing that the fine-grain gun cavity underwent along with the

  6. Evaluation of superconducting quantum interference devices interfaced with digital signal processing electronics for biomagnetic applications

    SciTech Connect

    Kung, Pang-Jen, Flynn, E.R.; Bracht, R.R.; Lewis, P.S.

    1994-08-01

    The performance of a dc-SQUID magnetometer driven by both analog electronics and digital signal processors are investigated and compared for biomagnetic applications. Low-noise ( < 5 {mu} {Phi} {sub 0}/{radical}Hz at 1 Hz) dc-SQUIDs were fabricated by Conductus, Inc. using the all-refractory Nb/Al/Al{sub 2}O{sub 3}/Nb process on silicon substrates with on-chip modulation coils and integral washer damping resistors. A second-order gradiometer was magnetically coupled to the input coil of the SQUID to maximize the detected signal strength. The readout of this SQUID gradiometer was achieved using a conventional flux-locked loop (FLL) circuit to provide a linearized voltage output that was proportional to the flux applied to the SQUID. A shielded cylinder was constructed to house the magnetometer to reduce ambient field noise. To realize the digital feedback loop, the analog FLL is replaced except for the preamplifier by a digital signal processing board with dual 16-bit A/D and D/A converters. This approach shows several advantages over the analog scheme including operational flexibility, cost reduction, and possibly, the enhancement of dynamic ranges and slew rates.

  7. Superconducting interfaces between insulating oxides.

    PubMed

    Reyren, N; Thiel, S; Caviglia, A D; Kourkoutis, L Fitting; Hammerl, G; Richter, C; Schneider, C W; Kopp, T; Rüetschi, A-S; Jaccard, D; Gabay, M; Muller, D A; Triscone, J-M; Mannhart, J

    2007-08-31

    At interfaces between complex oxides, electronic systems with unusual electronic properties can be generated. We report on superconductivity in the electron gas formed at the interface between two insulating dielectric perovskite oxides, LaAlO3 and SrTiO3. The behavior of the electron gas is that of a two-dimensional superconductor, confined to a thin sheet at the interface. The superconducting transition temperature of congruent with 200 millikelvin provides a strict upper limit to the thickness of the superconducting layer of congruent with 10 nanometers.

  8. A 200 SUPERCONDUCTING RACETRACK MICROTRON,

    DTIC Science & Technology

    A race-track microtron is proposed consisting of two 180 degree magnets spaced 2.5 meters apart with a superconducting linac section between. The...MeV per turn. The electrons are injected into the microtron at about 12 MeV from a second superconducting accelerator section. The spacing between...superconducting linac sections, a beam current of 100 microamps at unity duty cycle is feasible. It is also possible to build the microtron using

  9. Application of advanced electronics to a future spacecraft computer design

    NASA Technical Reports Server (NTRS)

    Carney, P. C.

    1980-01-01

    Advancements in hardware and software technology are summarized with specific emphasis on spacecraft computer capabilities. Available state of the art technology is reviewed and candidate architectures are defined.

  10. Electron Precipitation at Mars: Advancing Our Understanding with MAVEN

    NASA Astrophysics Data System (ADS)

    Al Noori, H.; Lillis, R. J.; Fillingim, M. O.

    2015-12-01

    Electrons from the solar wind enter the Martian upper atmosphere from space in a process known as electron precipitation. These electrons are confined to move along magnetic field lines and, when those field lines intersect the atmosphere, the electrons collide with atmospheric neutral particles, resulting in heating, dissociation, ionization and excitation of those neutrals. Electron precipitation is an important source of energy input to the Mars upper atmosphere, and is typically the dominant source on the nightside. Past observations from Mars Global Surveyor have characterized patterns of electron precipitation, but only at ~400 km and ~2 AM local time. The MAVEN mission and in particular the SWEA instrument, provides an opportunity to study the distribution of suprathermal electrons in near-Mars space, over a range of altitudes from 120-6000 km and at a range of local times. We will present preliminary observations of flux patterns of these electrons.

  11. Superconducting Hot-Electron Bolometric Mixer Receivers, and Evolution of Ionized Nebulae

    NASA Astrophysics Data System (ADS)

    Kawamura, Hiroyuki Jonathan

    Receivers incorporating niobium nitride phonon-cooled hot-electron bolometric mixers have been constructed and characterized. The mixer elements are thin-film NbN microbridges with dimensions of ~4 nm thickness, 1-20 μm width and 1.5-4 μm length. These are incorporated in waveguide receivers operating at 200 GHz, 450 GHz, 660 GHz, and 900 GHz. Operating at 4.2 K, the double-sideband receiver noise temperatures in each frequency band were 750 K at 244 GHz, 410 K at 430 GHz, 483 K at 606 GHz, and 1150 K at 800 GHz, a an intermediate frequency of 1.4 GHz and 200 MHz bandwidth. The receiver noise temperature is generally less than 3 GHz K-1 for mixers most recently fabricated. The intermediate frequency bandwidth exceeds 2 GHz, and the local oscillator power for optimal mixing is ~1μW. In addition, the time-evolution of ionized nebulae was studied using difference maps generated by combining new high sensitivity Very Large Array radio interferometrer observations with archived data, separated by a time baseline of ~10 yr. The distances to two bright planetary nebulae are determined by detecting their expansion parallax: the distance to BD +30o3639 is 1.5 ± 0.4 kpc, and to NGC 6572 is 1.2 ± 0.4 kpc. These distances incorporate a new correction term, and are considerably more accurate than those reported previously. The difference mapping technique is for the first time used to study another class of objects, and applied to observe changes in two bright, well-studied compact H scII regions, W 3(OH) and NGC 7538. W 3(OH) is observed to expand at a rate of 3 km s-1, which although significantly smaller than the plasma sound speed, implies an age of ~3×103 yr. This measurement has important consequences for modeling evolution of compact H scII regions. In contrast NGC 7538 exhibits significant changes in the structure whose interpretation is difficult, but nevertheless suggest that structures observed in compact H scII regions are not static.

  12. Advanced Power Electronics Interfaces for Distributed Energy Workshop Summary: August 24, 2006, Sacramento, California

    SciTech Connect

    Treanton, B.; Palomo, J.; Kroposki, B.; Thomas, H.

    2006-10-01

    The Advanced Power Electronics Interfaces for Distributed Energy Workshop, sponsored by the California Energy Commission Public Interest Energy Research program and organized by the National Renewable Energy Laboratory, was held Aug. 24, 2006, in Sacramento, Calif. The workshop provided a forum for industry stakeholders to share their knowledge and experience about technologies, manufacturing approaches, markets, and issues in power electronics for a range of distributed energy resources. It focused on the development of advanced power electronic interfaces for distributed energy applications and included discussions of modular power electronics, component manufacturing, and power electronic applications.

  13. Magnetic and Superconducting Materials at High Pressures

    SciTech Connect

    Struzhkin, Viktor V.

    2015-03-24

    transitions from magnetic to nonmagnetic phases in a broad pressure-temperature range; using X-ray methods including the newly developed RIXS high-pressure technique to explore pressure-tuned electronic excitations in strongly correlated 3d-materials; and advancing transport and magnetic techniques for measurements on small samples at very high pressures in a wide temperature range, with the application of focused ion beam technology and photolithography tailored to the design of microcircuits down to a nanoscale size, thus expanding the horizon in the search for novel physical phenomena at ultrahigh pressures. Apply new optical magnetic sensing techniques with NV- centers in diamond to detect superconductivity and magnetic transitions with unprecedented spatial resolution.

  14. Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7K under pressure

    NASA Astrophysics Data System (ADS)

    Medvedev, S.; McQueen, T. M.; Troyan, I. A.; Palasyuk, T.; Eremets, M. I.; Cava, R. J.; Naghavi, S.; Casper, F.; Ksenofontov, V.; Wortmann, G.; Felser, C.

    2009-08-01

    The discovery of new high-temperature superconductors based on FeAs has led to a new `gold rush' in high-TC superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach TC values up to 55K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of β-Fe1.01Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7K under an applied pressure of 8.9GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as TC rises, owing to a collapse of the separation between the Fe2Se2 layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7GPa and completed at 38GPa), Fe1.01Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.

  15. Electronic and magnetic phase diagram of beta-Fe(1.01)Se with superconductivity at 36.7 K under pressure.

    PubMed

    Medvedev, S; McQueen, T M; Troyan, I A; Palasyuk, T; Eremets, M I; Cava, R J; Naghavi, S; Casper, F; Ksenofontov, V; Wortmann, G; Felser, C

    2009-08-01

    The discovery of new high-temperature superconductors based on FeAs has led to a new 'gold rush' in high-T(C) superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach T(C) values up to 55 K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of beta-Fe(1.01)Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as T(C) rises, owing to a collapse of the separation between the Fe(2)Se(2) layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe(1.01)Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.

  16. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  17. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  18. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  19. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  20. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... rail carrier must use a CBP-approved electronic data interchange system. (1) Through cargo in transit... and contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable...

  1. Vortex motion in superconducting single-crystal microstructures of NbSe2

    NASA Astrophysics Data System (ADS)

    Mills, Shaun; Staley, Neal; Puls, Conor; Shen, Chenyi; Li, Linjun; Xu, Zhuan; Liu, Ying

    2012-02-01

    Superconducting microstructures prepared by advanced nanofabrication methods can be used to address long-standing, fundamental questions concerning vortex motion, including vortex tunneling and the Aharonov-Casher effect of vortices. The observation of these phenomena requires devices with minimal disorder and the fewest dissipative normal electrons. We have developed a process to fabricate superconducting microstructures from single-crystal ultrathin flakes of the layered Type II superconductor NbSe2. Our process utilizes a multi-step electron beam lithography technique, whereby a NbSe2 flake is cut into a desired microstructure with appropriate electrical leads. Despite the small device dimensions, which feature line widths less than 40 nanometers, our devices are superconducting. We are currently working on superconducting microstructures of NbSe2 that involve integration of aluminum leads, aiming at the control and measurement of vortices in these novel structures.

  2. Electronic properties of PbMo6S8 and CuxMo6S8. [for superconductivity

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Alterovitz, S. A.

    1979-01-01

    Normal-state properties of sputtered, evaporated, and sintered PbMo6S8 and CuxMo6S8 (where x is between 1.6 and 2.5) samples are reported. These include the temperature dependence of resistivity, magnetoresistance, and Hall effect. When combined with superconducting properties (measured on the same samples) and theory, a number of Fermi-surface and superconducting parameters are derived. Fits to the temperature dependence of the resistivity are compared with similar fits for A-15 structure superconductors.

  3. Electron acceleration with advanced injection methods at the ASTRA laser

    NASA Astrophysics Data System (ADS)

    Poder, Kristjan; Carreira-Lopes, Nelson; Wood, Jonathan; Cole, Jason; Dangor, Bucker; Foster, Peta; Gopal, Ram; Kamperidis, Christos; Kononenko, Olena; Mangles, Stuart; Olgun, Halil; Palmer, Charlotte; Symes, Daniel; Pattathil, Rajeev; Najmudin, Zulfikar; Imperial College London Team; Central Laser Facility Collaboration; Tata InsituteFundamental Research Collaboration; DESY Collaboration

    2015-11-01

    Recent electron acceleration results from the ASTRA laser facility are presented. Experiments were performed using both the 40 TW ASTRA and the 350 TW ASTRA-Gemini laser. Fundamental electron beam properties relating to its quality were investigated both experimentally and with PIC simulations. For increased control over such parameters, various injection mechanisms such as self-injection and ionization injection were employed. Particular interest is given to the dynamics of ionization injected electrons in strongly driven wakes.

  4. USMC Electronic Warfare 2025: Trading Expertise for Advanced Technology

    DTIC Science & Technology

    2011-04-15

    airborne electronic warlare during the transition period away from legacy equipment. EA-6B pilots and Electroilic Countermeasures Officers ( ECMOs ...Electronic Warfare (EW) capability. As an EA-6B Electronic Countenneasures Officer ( ECMO ), I anticipate that both the United States Marine Corps and all... ECMOs . An increased workload for Radio Battalion will have the same effect that the assumption of an additional function of Marine aviation will have on

  5. Impact of E × B flow shear on turbulence and resulting power fall-off width in H-mode plasmas in experimental advanced superconducting tokamak

    SciTech Connect

    Yang, Q. Q. Zhong, F. C. E-mail: fczhong@dhu.edu.cn; Jia, M. N.; Xu, G. S. E-mail: fczhong@dhu.edu.cn; Wang, L.; Wang, H. Q.; Chen, R.; Yan, N.; Liu, S. C.; Chen, L.; Li, Y. L.; Liu, J. B.

    2015-06-15

    The power fall-off width in the H-mode scrape-off layer (SOL) in tokamaks shows a strong inverse dependence on the plasma current, which was noticed by both previous multi-machine scaling work [T. Eich et al., Nucl. Fusion 53, 093031 (2013)] and more recent work [L. Wang et al., Nucl. Fusion 54, 114002 (2014)] on the Experimental Advanced Superconducting Tokamak. To understand the underlying physics, probe measurements of three H-mode discharges with different plasma currents have been studied in this work. The results suggest that a higher plasma current is accompanied by a stronger E×B shear and a shorter radial correlation length of turbulence in the SOL, thus resulting in a narrower power fall-off width. A simple model has also been applied to demonstrate the suppression effect of E×B shear on turbulence in the SOL and shows relatively good agreement with the experimental observations.

  6. Monte Carlo simulation of a Bonner sphere spectrometer for application to the determination of neutron field in the Experimental Advanced Superconducting Tokamak experimental hall

    SciTech Connect

    Hu, Z. M.; Xie, X. F.; Chen, Z. J.; Peng, X. Y.; Du, T. F.; Cui, Z. Q.; Ge, L. J.; Li, T.; Yuan, X.; Zhang, X.; Li, X. Q.; Zhang, G. H.; Chen, J. X.; Fan, T. S.; Hu, L. Q.; Zhong, G. Q.; Lin, S. Y.; Wan, B. N.; Gorini, G.

    2014-11-15

    To assess the neutron energy spectra and the neutron dose for different positions around the Experimental Advanced Superconducting Tokamak (EAST) device, a Bonner Sphere Spectrometer (BSS) was developed at Peking University, with totally nine polyethylene spheres and a SP9 {sup 3}He counter. The response functions of the BSS were calculated by the Monte Carlo codes MCNP and GEANT4 with dedicated models, and good agreement was found between these two codes. A feasibility study was carried out with a simulated neutron energy spectrum around EAST, and the simulated “experimental” result of each sphere was obtained by calculating the response with MCNP, which used the simulated neutron energy spectrum as the input spectrum. With the deconvolution of the “experimental” measurement, the neutron energy spectrum was retrieved and compared with the preset one. Good consistence was found which offers confidence for the application of the BSS system for dose and spectrum measurements around a fusion device.

  7. A DFT study of electron-phonon coupling in proxy rocksalt CuX (X = S, Se, Te) structures and its relationship to possible manifestation of superconductivity

    NASA Astrophysics Data System (ADS)

    Grant, Paul; Hammond, Robert

    2015-03-01

    We have previously reported our computational studies on idealized copper monochalcogenide rocksalt structures, both cubic and tetragonal, focusing on their possible antiferromagnetic properties as determined within a Van Vleck-Mott-Anderson-Hubbard framework. For all values of Hubbard U in the range 0-7 eV, only copper monoxide exhibits a Mott-Hubbard electronic structure, the remainder (S, Se, Te) yielding metallic states characterized by nesting Fermi surfaces arising from Jahn-Teller degenerate s-p overlap. These results suggest exploring possible manifestation of superconductivity via electron-phonon mediated Cooper pairing. We will disclose our results to date applying the Eliashberg-McMillan-Allen-Dynes strong coupling framework to the DFT -derived electronic and vibrational states of CuS, CuSe and CuTe.

  8. Advances in tunable powerful lasers: The advanced free-electron laser

    SciTech Connect

    Singer, S.; Sheffield, R.

    1993-12-31

    In the past several decades, remarkable progress in laser science and technology has made it possible to obtain laser light from the ultra-violet to the far infra-red from a variety of laser types, and at power levels from milliwatts to kilowatts (and, some day, megawatts). However, the availability of tunable lasers at ``high`` power (above a few tens of watts) is more limited. Figure 1, an assessment of the availability of tunable lasers, shows the covered range to be about 400 to 2000 nanometers. A variety of dye lasers cover the visible and near infra red, each one of which is tunable over approximately a 10% range. In the same region, the TI:saphire laser is adjustable over a 20 to 25% range. And finally, optical parametric oscillators can cover the range from about 400 nanometers out to about 2000 nm (even farther at reduced energy output). The typical output energy per pulse may vary from a few to one hundred millijoules, and since repetition rates of 10 to 100 Hertz are generally attainable, average output powers of tens of watts are possible. In recent years, a new approach to powerful tunable lasers -- the Free-Electron Laser (FEL) -- has emerged. In this paper we will discuss advances in FEL technology which not only enable tunability at high average power over a very broad range of wavelengths, but also make this device more usable. At present, that range is about one micron to the far infra red; with extensions of existing technology, it should be extendable to the vacuum ultra violet region.

  9. Superconducting Electronic Film Structures

    DTIC Science & Technology

    1991-02-14

    superconductors, yttrium , barium, copper, oxides, high, critical, temperature, thin films, tunneling, barriers, thallium, sputtering. 19. ABSTRACT (Continue on...50*C lower than that required for YBCO. In common with YBCO, the best films grew epitaxially with a c-axis orientation on SrTiO3 , LaAIO 3, and NdGaO 3...for c-axis growth were (001) faces of LaAIO 3, NdGaO 3 , SrTiO3 , MgO. yttria-stabilized ZrO2 (YSZ), 11 and (1102) sapphire. Low substrate

  10. Superconducting Cable

    DOEpatents

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-07-22

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  11. Superconducting Cable

    DOEpatents

    Hughey, Raburn L.; Sinha, Uday K.; Reece, David S.; Muller, Albert C.

    2005-03-08

    In order to provide a flexible oxide superconducting cable which is reduced in AC loss, tape-shaped superconducting wires covered with a stabilizing metal are wound on a flexible former. The superconducting wires are preferably laid on the former at a bending strain of not more than 0.2%. In laying on the former, a number of tape-shaped superconducting wires are laid on a core member in a side-by-side manner, to form a first layer. A prescribed number of tape-shaped superconducting wires are laid on top of the first layer in a side-by-side manner, to form a second layer. The former may be made of a metal, plastic, reinforced plastic, polymer, or a composite and provides flexibility to the superconducting wires and the cable formed therewith.

  12. High temperature interfacial superconductivity

    SciTech Connect

    Bozovic, Ivan; Logvenov, Gennady; Gozar, Adrian Mihai

    2012-06-19

    High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.

  13. Interplay between superconductivity and magnetism in iron-based superconductors

    SciTech Connect

    Chubukov, Andrey V

    2015-06-10

    This proposal is for theoretical work on strongly correlated electron systems, which are at the center of experimental and theoretical activities in condensed-matter physics. The interest to this field is driven fascinating variety of observed effects, universality of underlying theoretical ideas, and practical applications. I propose to do research on Iron-based superconductors (FeSCs), which currently attract high attention in the physics community. My goal is to understand superconductivity and magnetism in these materials at various dopings, the interplay between the two, and the physics in the phase in which magnetism and superconductivity co-exist. A related goal is to understand the origin of the observed pseudogap-like behavior in the normal state. My research explores the idea that superconductivity is of electronic origin and is caused by the exchange of spin-fluctuations, enhanced due to close proximity to antiferromagnetism. The multi-orbital/multi-band nature of FeSCs opens routes for qualitatively new superconducting states, particularly the ones which break time-reversal symmetry. By all accounts, the coupling in pnictdes is below the threshold for Mott physics and I intend to analyze these systems within the itinerant approach. My plan is to do research in two stages. I first plan to address several problems within weak-coupling approach. Among them: (i) what sets stripe magnetic order at small doping, (ii) is there a preemptive instability into a spin-nematic state, and how stripe order affects fermions; (iii) is there a co-existence between magnetism and superconductivity and what are the system properties in the co-existence state; (iv) how superconductivity emerges despite strong Coulomb repulsion and can the gap be s-wave but with nodes along electron FSs, (v) are there complex superconducting states, like s+id, which break time reversal symmetry. My second goal is to go beyond weak coupling and derive spin-mediated, dynamic interaction between

  14. Nanofabrication by advanced electron microscopy using intense and focused beam∗

    PubMed Central

    Furuya, Kazuo

    2008-01-01

    The nanogrowth and nanofabrication of solid substances using an intense and focused electron beam are reviewed in terms of the application of scanning and transmission electron microscopy (SEM, TEM and STEM) to control the size, position and structure of nanomaterials. The first example discussed is the growth of freestanding nanotrees on insulator substrates by TEM. The growth process of the nanotrees was observed in situ and analyzed by high-resolution TEM (HRTEM) and was mainly controlled by the intensity of the electron beam. The second example is position- and size-controlled nanofabrication by STEM using a focused electron beam. The diameters of the nanostructures grown ranged from 4 to 20 nm depending on the size of the electron beam. Magnetic nanostructures were also obtained using an iron-containing precursor gas, Fe(CO)5. The freestanding iron nanoantennas were examined by electron holography. The magnetic field was observed to leak from the nanostructure body which appeared to act as a ‘nanomagnet’. The third example described is the effect of a vacuum on the size and growth process of fabricated nanodots containing W in an ultrahigh-vacuum field-emission TEM (UHV-FE-TEM). The size of the dots can be controlled by changing the dose of electrons and the partial pressure of the precursor. The smallest particle size obtained was about 1.5 nm in diameter, which is the smallest size reported using this method. Finally, the importance of a smaller probe and a higher electron-beam current with atomic resolution is emphasized and an attempt to develop an ultrahigh-vacuum spherical aberration corrected STEM (Cs-corrected STEM) at NIMS is reported. PMID:27877936

  15. High-resolution electron microscopy of advanced materials

    SciTech Connect

    Mitchell, T.E.; Kung, H.H.; Sickafus, K.E.; Gray, G.T. III; Field, R.D.; Smith, J.F.

    1997-11-01

    This final report chronicles a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The High-Resolution Electron Microscopy Facility has doubled in size and tripled in quality since the beginning of the three-year period. The facility now includes a field-emission scanning electron microscope, a 100 kV field-emission scanning transmission electron microscope (FE-STEM), a 300 kV field-emission high-resolution transmission electron microscope (FE-HRTEM), and a 300 kV analytical transmission electron microscope. A new orientation imaging microscope is being installed. X-ray energy dispersive spectrometers for chemical analysis are available on all four microscopes; parallel electron energy loss spectrometers are operational on the FE-STEM and FE-HRTEM. These systems enable evaluation of local atomic bonding, as well as chemical composition in nanometer-scale regions. The FE-HRTEM has a point-to-point resolution of 1.6 {angstrom}, but the resolution can be pushed to its information limit of 1 {angstrom} by computer reconstruction of a focal series of images. HRTEM has been used to image the atomic structure of defects such as dislocations, grain boundaries, and interfaces in a variety of materials from superconductors and ferroelectrics to structural ceramics and intermetallics.

  16. Electron Beam Transport in Advanced Plasma Wave Accelerators

    SciTech Connect

    Williams, Ronald L

    2013-01-31

    The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams were generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.

  17. Development of advanced electron holographic techniques and application to industrial materials and devices.

    PubMed

    Yamamoto, Kazuo; Hirayama, Tsukasa; Tanji, Takayoshi

    2013-06-01

    The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: GaAs compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.

  18. Transmission Electron Microscopy Advances Reveal Subtle Comet Dust Differences

    NASA Astrophysics Data System (ADS)

    Ishii, H. A.; Bradley, J. P.

    2015-07-01

    TEM advances in multi-SDD-detector EDX mapping applied to Wild 2 dust and likely-cometary CP IDPs demonstrates chondritic fine-grained material at terminal particles is unlike GEMS and consistent with debris generated during the deceleration process.

  19. Preface: Special Topic Section on Advanced Electronic Structure Methods for Solids and Surfaces

    SciTech Connect

    Michaelides, Angelos; Martinez, Todd J.; Alavi, Ali; Kresse, Georg

    2015-09-14

    This Special Topic section on Advanced Electronic Structure Methods for Solids and Surfaces contains a collection of research papers that showcase recent advances in the high accuracy prediction of materials and surface properties. It provides a timely snapshot of a growing field that is of broad importance to chemistry, physics, and materials science.

  20. TOPICAL REVIEW: Advances in high-field superconducting composites by addition of artificial pinning centres to niobium-titanium

    NASA Astrophysics Data System (ADS)

    Cooley, L. D.; Motowidlo, L. R.

    1999-08-01

    Artificial pinning-centre (APC) niobium-titanium composites attain critical current density Jc values higher than 4000 A mm-2 at 5 T, 4.2 K, surpassing the barrier reached by the conventional Nb-Ti composite process. At 2 T APC composites achieve more than double the Jc of conventional composites, making them particularly well suited for low-field applications. On the other hand, APC composites are inferior to conventional composites at 8 T, due to weak high-field pinning and reduced upper critical field. This review discusses fabrication techniques, microstructural development and superconducting and flux-pinning properties of APC composites. Key elements and underlying issues for achieving higher Jc are identified and discussed in terms of the current state of the art.

  1. Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation using Superconducting Tunnel Junctions with Radio-Frequency Single-Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

    2002-01-01

    The science drivers for the SPIRIT/SPECS missions demand sensitive, fast, compact, low-power, large-format detector arrays for high resolution imaging and spectroscopy in the far infrared and submillimeter. Detector arrays with 10,000 pixels and sensitivity less than 10(exp 20)-20 W/Hz(exp 20)0.5 are needed. Antenna-coupled superconducting tunnel junction detectors with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique when forming arrays. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  2. Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems

    NASA Technical Reports Server (NTRS)

    Zhao, Y.; Zhang, Q. R.; Zhang, H.

    1990-01-01

    A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed.

  3. Importance of the Fermi-surface topology to the superconducting state of the electron-doped pnictide Ba(Fe1-xCox)₂As₂

    DOE PAGES

    Liu, Chang; Palczewski, A. D.; Dhaka, R. S.; ...

    2011-07-25

    We used angle-resolved photoemission spectroscopy and thermoelectric power to study the poorly explored, highly overdoped side of the phase diagram of Ba(Fe1-xCox)₂As₂ high-temperature superconductor. Our data demonstrate that several Lifshitz transitions—topological changes of the Fermi surface—occur for large x. The central hole barrel changes to ellipsoids that are centered at Z at x~0.11 and subsequently disappear around x~0.2; changes in thermoelectric power occur at similar x values. Tc decreases and goes to zero around x~0.15—between the two Lifshitz transitions. Beyond x=0.2 the central pocket becomes electron-like and superconductivity does not exist. Our observations reveal the importance of the underlying Fermiologymore » in electron-doped iron arsenides. We speculate that a likely necessary condition for superconductivity in these materials is the presence of the central hole pockets rather than nesting between central and corner pockets.« less

  4. Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays

    NASA Astrophysics Data System (ADS)

    Plimley, Brian Christopher

    Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron

  5. Recent advances in molecular electronics based on carbon nanotubes.

    PubMed

    Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

    2010-01-01

    Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field.

  6. Superconductivity in diamond.

    PubMed

    Ekimov, E A; Sidorov, V A; Bauer, E D; Mel'nik, N N; Curro, N J; Thompson, J D; Stishov, S M

    2004-04-01

    Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields. With these physical properties, diamond is attractive for electronic applications, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500-2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature T(c) approximately 4 K; superconductivity survives in a magnetic field up to Hc2(0) > or = 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.

  7. Advanced Opto-Electronics (LIDAR and Microsensor Development)

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern C. (Technical Monitor); Spangler, Lee H.

    2005-01-01

    Our overall intent in this aspect of the project were to establish a collaborative effort between several departments at Montana State University for developing advanced optoelectronic technology for advancing the state-of-the-art in optical remote sensing of the environment. Our particular focus was on development of small systems that can eventually be used in a wide variety of applications that might include ground-, air-, and space deployments, possibly in sensor networks. Specific objectives were to: 1) Build a field-deployable direct-detection lidar system for use in measurements of clouds, aerosols, fish, and vegetation; 2) Develop a breadboard prototype water vapor differential absorption lidar (DIAL) system based on highly stable, tunable diode laser technology developed previously at MSU. We accomplished both primary objectives of this project, in developing a field-deployable direct-detection lidar and a breadboard prototype of a water vapor DIAL system. Paper summarizes each of these accomplishments.

  8. Superconducting Materials

    NASA Technical Reports Server (NTRS)

    1995-01-01

    After working with Lewis Research Center and Jet Propulsion Laboratory, Superconducting Technologies, Inc. (STI) adapted NASA requirements and refined its own standard production recipe. STI uses high temperature superconducting (HTS) materials in its basic products: high quality thin films, circuits and components. Applications include microwave circuits for radar to reduce interference.

  9. Superconducting Transition at 38 K in Insulating-Overdoped La2CuO4-La1:64Sr0:36CuO4 Superlattices: Evidence for Interface Electronic Redistribution from Resonant Soft X-Ray Scattering

    SciTech Connect

    Smadici, S.; Bozovic, I.; Lee, J. C. T.; Wang, S.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Deville Cavellin, C.

    2009-03-12

    We use resonant soft x-ray scattering (RSXS) to quantify the hole distribution in a superlattice of insulating La{sub 2}CuO{sub 4} (LCO) and overdoped La{sub 2-x}Sr{sub x}CuO{sub 4} (LSCO). Despite its nonsuperconducting constituents, this structure is superconducting with T{sub c} = 38 K. We found that the conducting holes redistribute electronically from LSCO to the LCO layers. The LCO layers were found to be optimally doped, suggesting they are the main drivers of superconductivity. Our results demonstrate the utility of RSXS for separating electronic from structural effects at oxide interfaces.

  10. Superconducting thermometer for cryogenics

    NASA Technical Reports Server (NTRS)

    White, F. A.

    1977-01-01

    Digital electronic device uses superconducting filaments as sensors. Simple solid-state circuitry combined with filaments comprise highly-reliable temperature monitor. Device has ability to track very fast thermal transients and "on/off" output is adaptable to remote sensing and telemetry.

  11. Advanced electron crystallography through model-based imaging

    PubMed Central

    Van Aert, Sandra; De Backer, Annick; Martinez, Gerardo T.; den Dekker, Arnold J.; Van Dyck, Dirk; Bals, Sara; Van Tendeloo, Gustaaf

    2016-01-01

    The increasing need for precise determination of the atomic arrangement of non-periodic structures in materials design and the control of nanostructures explains the growing interest in quantitative transmission electron microscopy. The aim is to extract precise and accurate numbers for unknown structure parameters including atomic positions, chemical concentrations and atomic numbers. For this purpose, statistical parameter estimation theory has been shown to provide reliable results. In this theory, observations are considered purely as data planes, from which structure parameters have to be determined using a parametric model describing the images. As such, the positions of atom columns can be measured with a precision of the order of a few picometres, even though the resolution of the electron microscope is still one or two orders of magnitude larger. Moreover, small differences in average atomic number, which cannot be distinguished visually, can be quantified using high-angle annular dark-field scanning transmission electron microscopy images. In addition, this theory allows one to measure compositional changes at interfaces, to count atoms with single-atom sensitivity, and to reconstruct atomic structures in three dimensions. This feature article brings the reader up to date, summarizing the underlying theory and highlighting some of the recent applications of quantitative model-based transmisson electron microscopy. PMID:26870383

  12. Advancing Small Satellite Electronics Heritage for Microfluidic Biological Experiments

    NASA Technical Reports Server (NTRS)

    White, Bruce; Mazmanian, Edward; Tapio, Eric

    2016-01-01

    DLR's Eu:CROPIS (Euglena and Combined Regenerative Organic-Food Production in Space) mission, launching in 2017, will carry multiple biological payloads into a sun-synchronous orbit, including NASA Ames' PowerCell experiment. PowerCell will attempt to characterize the viability of synthetic biology at micro-g, Lunar, and Martian gravity levels. PowerCell experiment requirements demand an electronic system similar to previous microfluidic biology payloads, but with an expanded feature set. As such, the system was based on PharmaSat (Diaz-Aguado et al. 2009), a previous successful biology payload from NASA Ames, and improved upon. Newer, more miniaturized electronics allow for greater capability with a lower part count and smaller size. Two identical PowerCell enclosures will fly. Each enclosure contains two separate and identical experiments with a 48-segment optical density measurement system, grow light system, microfluidic system for nutrient delivery and waste flushing, plus thermal control and environmental sensing/housekeeping including temperature, pressure, humidity, and acceleration. Electronics consist of a single Master PCB that interfaces to the spacecraft bus and regulates power and communication, plus LED, Detector, and Valve Manifold PCBs for each experiment. To facilitate ease of reuse on future missions, experiment electronics were designed to be compatible with a standard 3U small sat form factor and power bus, or to interface with a Master power/comm PCB for use in a larger satellite as in the case of PowerCell's flight on Eu:CROPIS.

  13. An experimental superconducting helical undulator

    SciTech Connect

    Caspi, S.; Taylor, C.

    1995-12-31

    Improvements in the technology of superconducting magnets for high energy physics and recent advancements in SC materials with the artificial pinning centers (APC){sup 2}, have made a bifilar helical SC device an attractive candidate for a single-pass free electron laser (FEL){sup 3}. Initial studies have suggested that a 6.5 mm inner diameter helical device, with a 27 mm period, can generate a central field of 2-2.5 Tesla. Additional studies have also suggested that with a stored energy of 300 J/m, such a device can be made self-protecting in the event of a quench. However, since the most critical area associated with high current density SC magnets is connected with quenching and training, a short experimental device will have to be built and tested. In this paper we discuss technical issues relevant to the construction of such a device, including a conceptual design, fields, and forces.

  14. Superconducting structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2003-04-01

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  15. Superconducting Structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2005-09-13

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  16. Surface electronic structure and evidence of plain s -wave superconductivity in (L i0.8F e0.2)OHFeSe

    NASA Astrophysics Data System (ADS)

    Yan, Y. J.; Zhang, W. H.; Ren, M. Q.; Liu, X.; Lu, X. F.; Wang, N. Z.; Niu, X. H.; Fan, Q.; Miao, J.; Tao, R.; Xie, B. P.; Chen, X. H.; Zhang, T.; Feng, D. L.

    2016-10-01

    (L i0.8F e0.2)OHFeSe is a newly discovered intercalated iron-selenide superconductor with a Tc above 40 K, which is much higher than the Tc of bulk FeSe (8 K). Here we report a systematic study of (L i0.8F e0.2)OHFeSe by low temperature scanning tunneling microscopy (STM). We observed two kinds of surface terminations, namely FeSe and (L i0.8F e0.2)OH surfaces. On the FeSe surface, the superconducting state is fully gapped with double coherence peaks, and a vortex core state with split peaks near EF is observed. Through quasiparticle interference (QPI) measurements, we clearly observed intra- and interpocket scatterings in between the electron pockets at the M point, as well as some evidence of scattering that connects Γ and M points. Upon applying the magnetic field, the QPI intensity of all the scattering channels are found to behave similarly. Furthermore, we studied impurity effects on the superconductivity by investigating intentionally introduced impurities and intrinsic defects. We observed that magnetic impurities such as Cr adatoms can induce in-gap states and suppress superconductivity. However, nonmagnetic impurities such as Zn adatoms do not induce visible in-gap states. Meanwhile, we show that Zn adatoms can induce in-gap states in thick FeSe films, which is believed to have an s±-wave pairing symmetry. Our experimental results suggest it is likely that (L i0.8F e0.2)OHFeSe is a plain s -wave superconductor, whose order parameter has the same sign on all Fermi surface sections.

  17. Advanced manufacturing of SIMOX for low power electronics

    NASA Astrophysics Data System (ADS)

    Alles, Michael; Krull, Wade

    1996-04-01

    Silicon-on-insulator (SOI) has emerged as a key technology for low power electronics. The merits of SOI technology have been demonstrated, and are gaining acceptance in the semiconductor industry. In order for the SOI approach to be viable, several factors must converge, including the availability of SOI substrates in sufficient quantity, of acceptable quality, and at a competitive price. This work describes developments in SIMOX manufacturing technology and summarizes progress in each of these areas.

  18. Advanced Strained-Superlattice Photocathodes for Polarized Electron Sources

    SciTech Connect

    Dr. Aaron Moy

    2005-01-31

    Polarized electrons have been essential for high-energy parity-violating experiments and measurements of the nucleon spin structure. The availability of a polarized electron beam was crucial to the success of the Stanford Linear Collider (SLC) in achieving a precise measurement of the electroweak mixing angle, and polarized electron beams will be required for all future linear colliders. Polarized electrons are readily produced by GaAs photocathode sources. When a circularly polarized laser beam tuned to the bandgap minimum is directed to the negative-electron-affinity (NEA) surface of a GaAs crystal, longitudinally polarized electrons are emitted into vacuum. The electron polarization is easily reversed by reversing the laser polarization. The important properties of these photocathodes for accelerator applications are: degree of polarization of the extracted beam; ability to extract sufficient charge to meet accelerator pulse-structure requirements; efficiency and stability of operation; and absence of any asymmetries in the beam properties (charge, position, energy, etc.) upon polarization reversal. The performance of GaAs photocathodes has improved significantly since they were first introduced in 1978 [1]. The theoretical maximum polarization of 50% for natural GaAs was first exceeded in 1991 using the lattice mismatch of a thin InGaAs layer epitaxially grown over a GaAs substrate to generate a strain in the former that broke the natural degeneracy between the heavy- and light-hole valence bands [2]. Polarizations as high as 78% were produced for the SLC from photocathodes based on a thin GaAs epilayer grown on GaAsP [3,4]. After 10 years of experience with many cathode samples at several laboratories [5], the maximum polarization using the GaAs/GaAsP single strained-layer cathode remained limited to 80%, while the quantum efficiency (QE) for a 100-nm epilayer is only 0.3% or less. Two factors were known to limit the polarization of these cathodes: (1) the

  19. Advanced Electron Holography Applied to Electromagnetic Field Study in Materials Science.

    PubMed

    Shindo, Daisuke; Tanigaki, Toshiaki; Park, Hyun Soon

    2016-11-17

    Advances and applications of electron holography to the study of electromagnetic fields in various functional materials are presented. In particular, the development of split-illumination electron holography, which introduces a biprism in the illumination system of a holography electron microscope, enables highly accurate observations of electromagnetic fields and the expansion of the observable area. First, the charge distributions on insulating materials were studied by using split-illumination electron holography and including a mask in the illumination system. Second, the three-dimensional spin configurations of skyrmion lattices in a helimagnet were visualized by using a high-voltage holography electron microscope. Third, the pinning of the magnetic flux lines in a high-temperature superconductor YBa2 Cu3 O7-y was analyzed by combining electron holography and scanning ion microscopy. Finally, the dynamic accumulation and collective motions of electrons around insulating biomaterial surfaces were observed by utilizing the amplitude reconstruction processes of electron holography.

  20. Applications of advanced electric/electronic technology to conventional aircraft

    NASA Technical Reports Server (NTRS)

    Heimbold, R. L.

    1980-01-01

    The desirability of seven advanced technologies as applied to three commercial aircraft of 1985 to 1995 was investigated. Digital fly by wire, multiplexing, ring laser gyro, integrated avionics, all electric airplane, electric load management, and fiber optics were considered for 500 passenger, 50 passenger, and 30 passenger aircraft. The major figure of merit used was Net Value of Technology based on procurement and operating cost over the life of the aircraft. An existing computer program, ASSET, was used to resize the aircraft and evalute fuel usage and maintenance costs for each candidate configuration. Conclusions were that, for the 500 passenger aircraft, all candidates had a worthwhile payoff with the all electric airplane having a large payoff.