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Sample records for superconducting flux pumps

  1. A thermally actuated superconducting flux pump

    Energy Technology Data Exchange (ETDEWEB)

    Coombs, Timothy [Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)], E-mail: tac1000@cam.ac.uk; Hong Zhiyong; Zhu Xiaomin [Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2008-02-01

    The concept of a superconducting flux pump is relatively straightforward. A small magnetic field repeatedly applied will lead to a much larger field being trapped within the superconductor. This field is limited by the volume of the superconductor and by its critical current but not by the excitation field. Here we will describe a new technique which facilitates the creation of high magnetic fields and where the magnitude of the trapped field is limited by the superconductor not the magnetising field. The technique is demonstrated using measurements taken using samples of bulk YBCO as YBCO has a very high irreversibility field and has the potential to trap high magnetic fields. The technique could be applied to other superconductors such as BSCCO or MgB{sub 2} and in other forms such as thin or thick films.

  2. Macroscopic Magnetic Coupling Effect: The Physical Origination of a High-Temperature Superconducting Flux Pump

    Science.gov (United States)

    Wang, Wei; Coombs, Tim

    2018-04-01

    We have uncovered at the macroscopic scale a magnetic coupling phenomenon in a superconducting YBa2Cu3O7 -δ (YBCO) film, which physically explains the mechanism of the high-temperature superconducting flux pump. The coupling occurs between the applied magnetic poles and clusters of vortices induced in the YBCO film, with each cluster containing millions of vortices. The coupling energy is verified to originate from the inhomogeneous field of the magnetic poles, which reshapes the vortex distribution, aggregates millions of vortices into a single cluster, and accordingly moves with the poles. A contrast study is designed to verify that, to provide the effective coupling energy, the applied wavelength must be short while the field amplitude must be strong, i.e., local-field inhomogeneity is the crucial factor. This finding broadens our understanding of the collective vortex behavior in an applied magnetic field with strong local inhomogeneity. Moreover, this phenomenon largely increases the controlled vortex flow rate by several orders of magnitude compared with existing methods, providing motivation for and physical support to a new branch of wireless superconducting dc power sources, i.e., the high-temperature superconducting flux pump.

  3. Magnetic-flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  4. A finite element calculation of flux pumping

    Science.gov (United States)

    Campbell, A. M.

    2017-12-01

    A flux pump is not only a fascinating example of the power of Faraday’s concept of flux lines, but also an attractive way of powering superconducting magnets without large electronic power supplies. However it is not possible to do this in HTS by driving a part of the superconductor normal, it must be done by exceeding the local critical density. The picture of a magnet pulling flux lines through the material is attractive, but as there is no direct contact between flux lines in the magnet and vortices, unless the gap between them is comparable to the coherence length, the process must be explicable in terms of classical electromagnetism and a nonlinear V-I characteristic. In this paper a simple 2D model of a flux pump is used to determine the pumping behaviour from first principles and the geometry. It is analysed with finite element software using the A formulation and FlexPDE. A thin magnet is passed across one or more superconductors connected to a load, which is a large rectangular loop. This means that the self and mutual inductances can be calculated explicitly. A wide strip, a narrow strip and two conductors are considered. Also an analytic circuit model is analysed. In all cases the critical state model is used, so the flux flow resistivity and dynamic resistivity are not directly involved, although an effective resistivity appears when J c is exceeded. In most of the cases considered here is a large gap between the theory and the experiments. In particular the maximum flux transferred to the load area is always less than the flux of the magnet. Also once the threshold needed for pumping is exceeded the flux in the load saturates within a few cycles. However the analytic circuit model allows a simple modification to allow for the large reduction in I c when the magnet is over a conductor. This not only changes the direction of the pumped flux but leads to much more effective pumping.

  5. Reluctance motor employing superconducting magnetic flux switches

    International Nuclear Information System (INIS)

    Spyker, R.L.; Ruckstadter, E.J.

    1992-01-01

    This paper reports that superconducting flux switches controlling the magnetic flux in the poles of a motor will enable the implementation of a reluctance motor using one central single phase winding. A superconducting flux switch consists of a ring of superconducting material surrounding a ferromagnetic pole of the motor. When in the superconducting state the switch will block all magnetic flux attempting to flow in the ferromagnetic core. When switched to the normal state the superconducting switch will allow the magnetic flux to flow freely in that pole. By using one high turns-count coil as a flux generator, and selectively channeling flux among the various poles using the superconducting flux switch, 3-phase operation can be emulated with a single-hase central AC source. The motor will also operate when the flux generating coil is driven by a DC current, provided the magnetic flux switches see a continuously varying magnetic flux. Rotor rotation provides this varying flux due to the change in stator pole inductance it produces

  6. A liquid helium piston pump with a superconducting drive

    International Nuclear Information System (INIS)

    Schmidt, C.

    1984-01-01

    This chapter describes a bellows pump where the driving force is achieved by an arrangement of three superconducting coils. The pump was designed for use in the supercritical helium flow circuit of the LCT-conductor test facility. The main advantage of the superconducting drive, compared to conventional pumps with external drive, is the compact design. Force transferring parts between 4.2 K and room temperature are not necessary. The pump was tested in a closed loop arrangement. The superconducting drive for a piston pump consists of a moving coil in a constant background field. Other coil configurations and the upscaling of the pump design are discussed

  7. Continuous magnetic flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A method and means for altering the intensity of a magnetic field by transposing flux from one location to the location desired fro the magnetic field are examined. The device described includes a pair of communicating cavities formed in a block of superconducting material, is dimensioned to be insertable into one of the cavities and to substantially fill the cavity. Magnetic flux is first trapped in the cavities by establishing a magnetic field while the superconducting material is above the critical temperature at which it goes superconducting. Thereafter, the temperature of the material is reduced below the critical value, and then the exciting magnetic field may be removed. By varying the ratios of the areas of the two cavities, it is possible to produce a field having much greater flux density in the second, smaller cavity, into which the flux transposed.

  8. Flux pumping, fluctuations and climbing fields

    International Nuclear Information System (INIS)

    Coombs, T A; Hadeler, O; Zhang, M; Matsuda, K

    2012-01-01

    This paper describes the behaviour of bulk superconductors when subjected to a varying magnetic field. A magnetic model is described together with experimental results which explain and describe the behaviour of superconducting bulks when subjected to varying magnetic fields. We demonstrate how the behaviour is dependent on the magnitude and period of the perturbations in the fields. The model which we use has been implemented using the Comsol™ pde solver. It is a fully integrated model which uses a variable heat source to regulate the magnetic circuit and thereby to achieve flux pumping. Comsol™ is used for post solution visualization and the model is presented alongside experimental results which support and confirm the conclusions from the model. (paper)

  9. Superconducting bearings for a LHe transfer pump

    Science.gov (United States)

    Kloeppel, S.; Muehsig, C.; Funke, T.; Haberstroh, C.; Hesse, U.; Lindackers, D.; Zielke, S.; Sass, P.; Schoendube, R.

    2017-12-01

    Superconducting bearings are used in a number of applications for high speed, low loss suspension. Most of these applications suspend a warm shaft and thus require continuous cooling, which leads to additional power consumption. Therefore, it seems advantageous to use these bearings in systems that are inherently cold. One respective application is a submerged pump for the transfer of liquid helium into mobile dewars. Centrifugal pumps require tight sealing clearances, especially for low viscosity fluids and small sizes. This paper covers the design and qualification of superconducting YBCO bearings for a laboratory sized liquid helium transfer pump. Emphasis is given to the axial positioning, which strongly influences the achievable volumetric efficiency.

  10. Flux penetration in a ferromagnetic/superconducting bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Adamus, Z.; Cieplak, M.Z.; Abal' Oshev, A. [Polish Acad Sci, Inst Phys, PL-02668 Warsaw, (Poland); Konczykowski, M. [CEA/DSM/DRECAM, Laboratoire des Solides Irradies, F-91191 Gif Sur Yvette, (France); Konczykowski, M. [Ecole Polytech, CNRS - UMR 7642, F-91128 Palaiseau, (France); Cheng, X.M.; Zhu, L.Y.; Chien, C.L. [Johns Hopkins Univ, Dept Phys and Astron, Baltimore, MD 21218 (United States)

    2007-07-01

    An array of miniature Hall sensors is used to study the magnetic flux penetration in a ferromagnetic/superconducting bilayer consisting of Nb as a superconducting layer and Co/Pt multilayer with perpendicular magnetic anisotropy as a ferromagnetic layer, separated by an amorphous Si layer to avoid the proximity effect. It is found that the magnetic domains in the ferromagnetic layer create a large edge barrier in the superconducting layer which delays flux penetration. The smooth flux profiles observed in the absence of magnetic pinning change into terraced profiles in the presence of domains. (authors)

  11. Superconducting current generators

    International Nuclear Information System (INIS)

    Genevey, P.

    1970-01-01

    After a brief summary of the principle of energy storage and liberation with superconducting coils,two current generators are described that create currents in the range 600 to 1400 A, used for two storage experiments of 25 kJ and 50 kJ respectively. The two current generators are: a) a flux pump and b) a superconducting transformer. Both could be developed into more powerful units. The study shows the advantage of the transformer over the flux pump in order to create large currents. The efficiencies of the two generators are 95 per cent and 40 to 60 per cent respectively. (author) [fr

  12. Superconducting transformers, rectifiers, and switches. (Review paper)

    International Nuclear Information System (INIS)

    Ignatov, V.E.; Koval'kov, G.A.; Moskvitin, A.I.

    Cryogenic rectifiers using power cryotrons have been fabricated by many foreign firms since 1960. Present-day flux pumps require a low voltage power supply (several tens of millivolts) and a high current (kiloamperes). Increasing the power supply voltage will quadratically increase the flux pump losses and, given the limitations of existing materials, are not economically profitable. Present-day, cryotron-type flux pumps can best be used in power systems as a power supply for superconducting magnets, solenoids, storage devices, and superconducting exciting coils for turbogenerators. To increase the voltage of the next generation of transformers for superconducting dc power transmission, a research program must be set up to improve the cryotrons and to develop systems based on a different principle of operation, for example, semiconductor devices based on the principle of the volume effect in the intermediate environment

  13. Flux trapping in superconducting cavities

    International Nuclear Information System (INIS)

    Vallet, C.; Bolore, M.; Bonin, B.; Charrier, J.P.; Daillant, B.; Gratadour, J.; Koechlin, F.; Safa, H.

    1992-01-01

    The flux trapped in various field cooled Nb and Pb samples has been measured. For ambient fields smaller than 3 Gauss, 100% of the flux is trapped. The consequences of this result on the behavior of superconducting RF cavities are discussed. (author) 12 refs.; 2 figs

  14. Operation of a direct current transformer used as a 'flux pump'; Fonctionnement du transformateur a courant continu utilise en 'pompe a flux'

    Energy Technology Data Exchange (ETDEWEB)

    Deschanels, J L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    The author derives the equations governing the operation of a flux pump with a superconducting transformer. He shows that these exists a limiting value of the current in the charge coil and that the limit is independent of this coil. (author) [French] L'auteur etablit les equations de fonctionnement d'une pompe a flux a transformateur supraconducteur, il montre l'existence d'une limite, du courant dans la self de charge et l'independance de cette limite vis-a-vis de cette self. (auteur)

  15. Vacuum physics analysis of HT-7 superconducting tokamak pump limiter

    International Nuclear Information System (INIS)

    Hu Jiansheng; Li Chengfu; He Yexi

    1998-10-01

    The pump limiter is analysed with HT-7 superconducting tokamak parameter and the pump limiter construction. The particle exhaust of the pump limiter can be to achieve about 7.7%. So the pump limiter can be applied in the HT-7 device and will make good affection in plasma discharge

  16. Coherence properties in superconducting flux qubits

    Energy Technology Data Exchange (ETDEWEB)

    Spilla, Samuele

    2015-02-16

    The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which has been observed in a SQUID subjected to fast, large-amplitude modifications of its effective potential shape. The motivations for this work come from the fact that in the past few years there have been attempts to interpret the supposed quantum behavior of physical systems, such as Josephson devices, within a classical framework. Moreover, we analyze the possibility of generating GHZ states, namely maximally entangled states, in a quantum system made out of three Josephson qubits. In particular, we investigate the possible limitations of the GHZ state generation due to coupling to bosonic baths. In the second part of the thesis we address a particular cause of decoherence of flux qubits which has been disregarded until now: thermal gradients, which can arise due to accidental non equilibrium quasiparticle distributions. The reason for these detrimental effects is that heat currents flowing through Josephson tunnel junctions in response to a temperature gradient are periodic functions of the phase difference between the electrodes. The phase dependence of the heat current comes from Andreev reflection, namely an interplay between the quasiparticles which carry heat and the superconducting condensate which is sensitive to the superconducting phase difference. Generally speaking

  17. Heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter

    International Nuclear Information System (INIS)

    Sung, Hae-Jin; Go, Byeong-Soo; Jiang, Zhenan; Park, Minwon; Yu, In-Keun

    2016-01-01

    Highlights: • A large-scale HTS generator module has been suggested to avoid issues such as a huge vacuum vessel and higher reliability. • The challenging heat loss analysis of a large-scale HTS generator has successfully been performed, enabling the design of an optimal support structure having a total heat loss of 43 W/400 kW. • The results prove the potential of a large-scale superconducting wind-power generator to operate efficiently, and support further development of the concept. - Abstract: The development of an effective high-temperature superconducting (HTS) generator is currently a research focus; however, the reduction of heat loss of a large-scale HTS generator is a challenge. This study deals with a heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter. The generator module consists of an HTS rotor of the generator and an HTS flux pump exciter. The specifications of the module were described, and the detailed configuration of the module was illustrated. For the heat loss analysis of the module, the excitation loss of the flux pump exciter, eddy current loss of all of the structures in the module, radiation loss, and conduction loss of an HTS coil supporter were assessed using a 3D finite elements method program. In the case of the conduction loss, different types of the supporters were compared to find out the supporter of the lowest conduction loss in the module. The heat loss analysis results of the module were reflected in the design of the generator module and discussed in detail. The results will be applied to the design of large-scale superconducting generators for wind turbines including a cooling system.

  18. Heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Hae-Jin, E-mail: haejin0216@gmail.com [Changwon National University, 20 Changwondaehak-ro, Changwon, 641-773 (Korea, Republic of); Go, Byeong-Soo [Changwon National University, 20 Changwondaehak-ro, Changwon, 641-773 (Korea, Republic of); Jiang, Zhenan [Robinson Research Institute, Victoria University of Wellington, PO Box 33436 (New Zealand); Park, Minwon [Changwon National University, 20 Changwondaehak-ro, Changwon, 641-773 (Korea, Republic of); Yu, In-Keun, E-mail: yuik@changwon.ac.kr [Changwon National University, 20 Changwondaehak-ro, Changwon, 641-773 (Korea, Republic of)

    2016-11-15

    Highlights: • A large-scale HTS generator module has been suggested to avoid issues such as a huge vacuum vessel and higher reliability. • The challenging heat loss analysis of a large-scale HTS generator has successfully been performed, enabling the design of an optimal support structure having a total heat loss of 43 W/400 kW. • The results prove the potential of a large-scale superconducting wind-power generator to operate efficiently, and support further development of the concept. - Abstract: The development of an effective high-temperature superconducting (HTS) generator is currently a research focus; however, the reduction of heat loss of a large-scale HTS generator is a challenge. This study deals with a heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter. The generator module consists of an HTS rotor of the generator and an HTS flux pump exciter. The specifications of the module were described, and the detailed configuration of the module was illustrated. For the heat loss analysis of the module, the excitation loss of the flux pump exciter, eddy current loss of all of the structures in the module, radiation loss, and conduction loss of an HTS coil supporter were assessed using a 3D finite elements method program. In the case of the conduction loss, different types of the supporters were compared to find out the supporter of the lowest conduction loss in the module. The heat loss analysis results of the module were reflected in the design of the generator module and discussed in detail. The results will be applied to the design of large-scale superconducting generators for wind turbines including a cooling system.

  19. Fractional flux excitations and flux creep in a superconducting film

    International Nuclear Information System (INIS)

    Lyuksyutov, I.F.

    1995-01-01

    We consider the transport properties of a modulated superconducting film in a magnetic field parallel to the film. Modulation can be either intrinsic, due to the layered structure of the high-T c superconductors, or artificial, e.g. due to thickness modulation. This system has an infinite set ( >) of pinned phases. In the pinned phase the excitation of flux loops with a fractional number of flux quanta by the applied current j results in flux creep with a generated voltage V ∝ exp[-jo/j[. (orig.)

  20. Enhancement of magnetic flux distribution in a DC superconducting electric motor

    International Nuclear Information System (INIS)

    Hamid, N A; Ewe, L S; Chin, K M

    2013-01-01

    Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

  1. Low-frequency excess flux noise in superconducting devices

    Energy Technology Data Exchange (ETDEWEB)

    Kempf, Sebastian; Ferring, Anna; Fleischmann, Andreas; Enss, Christian [Kirchhoff-Institute for Physics, Heidelberg University (Germany)

    2016-07-01

    Low-frequency noise is a rather universal phenomenon and appears in physical, chemical, biological or even economical systems. However, there is often very little known about the underlying processes leading to its occurrence. In particular, the origin of low-frequency excess flux noise in superconducting devices has been an unresolved puzzle for many decades. Its existence limits, for example, the coherence time of superconducting quantum bits or makes high-precision measurements of low-frequency signals using SQUIDs rather challenging. Recent experiments suggest that low-frequency excess flux noise in Josephson junction based devices might be caused by the random reversal of interacting spins in surface layer oxides and in the superconductor-substrate interface. Even if it turns out to be generally correct, the underlying physical processes, i.e. the origin of these spins, their physical nature as well as the interaction mechanisms, have not been resolved so far. In this contribution we discuss recent measurements of low-frequency SQUID noise which we performed to investigate the origin of low-frequency excess flux noise in superconducting devices. Within this context we give an overview of our measurement techniques and link our data with present theoretical models and literature data.

  2. Superconducting Electric Boost Pump for Nuclear Thermal Propulsion, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A submersible, superconducting electric boost pump sized to meet the needs of future Nuclear Thermal Propulsion systems in the 25,000 lbf thrust range is proposed....

  3. Geneva University - Superconducting flux quantum bits: fabricated quantum objects

    CERN Multimedia

    2007-01-01

    Ecole de physique Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet 1211 GENEVE 4 Tél: (022) 379 62 73 Fax: (022) 379 69 92 Lundi 29 janvier 2007 COLLOQUE DE LA SECTION DE PHYSIQUE 17 heures - Auditoire Stueckelberg Superconducting flux quantum bits: fabricated quantum objects Prof. Hans Mooij / Kavli Institute of Nanoscience, Delft University of Technology The quantum conjugate variables of a superconductor are the charge or number of Cooper pairs, and the phase of the order parameter. In circuits that contain small Josephson junctions, these quantum properties can be brought forward. In Delft we study so-called flux qubits, superconducting rings that contain three small Josephson junctions. When a magnetic flux of half a flux quantum is applied to the loop, there are two states with opposite circulating current. For suitable junction parameters, a quantum superposition of those macroscopic states is possible. Transitions can be driven with resonant microwaves. These quantum ...

  4. Superconductivity in the background of disordered flux state of spins

    International Nuclear Information System (INIS)

    Feng Shiping; Guo Rui; Han Fei

    1992-01-01

    The phase diagram of the copper oxide materials with the antiferromagnetic and the superconducting properties as a function of doping δ is obtained in the framework of the t-J model by using the Schwinger boson-slave fermion theory. The results show that the spiral order of spins competes and coexists with superconductivity for small doping δ. For large doping δ, superconductivity appears, which may be caused by the occurrence of a disordered flux state of spins. The phase diagram suggests a strong relationship between antiferromagnetism and superconductivity. (orig.)

  5. Flux sensitivity of a piecewise normal and superconducting metal loop

    International Nuclear Information System (INIS)

    Buettiker, M.; Klapwijk, T.M.

    1986-01-01

    We consider a loop composed of a superconducting segment and a normal segment with an Aharonov-Bohm flux through the hole of the loop. The normal segment is assumed to be long compared to the superconducting coherence length xi but short compared to a mean inelastic diffusion length. The elementary excitation spectrum of the ground state of this loop is periodic with period hc/2e as long as the superconducting segment is larger than xi. If the superconducting segment length becomes of the order of xi, quasiparticles can tunnel through the superconducting gap and give rise to an excitation spectrum which is periodic with period hc/e. .AE

  6. Correlated electron motion, flux states and superconductivity

    International Nuclear Information System (INIS)

    Lederer, P.; Poilblanc, D.; Rice, T.K.

    1989-01-01

    This paper discusses how, when the on-site correlation is strong, electrons can move by usual hopping only on to empty sites but they can exchange position with their neighbors by a correlated motion. The phase in the former process is fixed and it favors Bloch states. When the concentration of empty sites is small then the latter process dominates and one is free to introduce a phase provided it is chosen to be the same for ↑ and ↓-spin electrons. Since for a partly filled band of non-interacting electrons the introduction of a uniform commensurate flux lowers the energy, the correlated motion can lead to a physical mechanism to generate flux states. These states have a collective gauge variable which is the same for ↑ and ↓-spins and superconducting properties are obtained by expanding around the optimum gauge determined by the usual kinetic energy term. If this latter term has singularities at special fillings then these may affect the superconducting properties

  7. Recovery characteristics of flux-lock type superconducting fault current limiter

    International Nuclear Information System (INIS)

    Han, T.H.; Choi, H.S.; Lim, S.H.; Lee, N.Y.

    2007-01-01

    The flux-lock type superconducting fault current limiter (SFCL) has attractive characteristics that the current limiting level can be adjusted by a winding direction and the inductance ratio between two coils. We changed the winding direction and the number of coils to compare the resistive type SFCL with the flux-lock type SFCL. The initial limiting current (I ini ) and quench characteristic were dependent on the winding direction and the inductance ratio of two coils. As a winding number was increased from 21 to 42, I ini and quench characteristic were proportionally increased. In additive polarity winding, I ini was 10.2 A and the quench time (T q ) was 0.53 ms, which was faster than that of a subtractive polarity winding. The consumed energy and recovery characteristics in a superconducting element showed the same tendency. Recovery characteristics in the flux-lock type SFCL were dependent on the consumed energy of a superconducting element. The recovery time was related to a heat energy and it was represented as the consuming time of the heat energy. As the heat energy was shown in H 0.24I 2 Rt, the recovery time was shortened in the following order: a subtractive polarity winding, a resistive type and an additive polarity winding. It was known that the recovery time was proportional to a consumed energy of a superconducting element

  8. Flux-pinning-induced stresses in a hollow superconducting cylinder with flux creep and viscosity properties

    International Nuclear Information System (INIS)

    Feng, W.J.; Gao, S.W.

    2014-01-01

    Highlights: • Magnetoelastic problem for a superconducting cylinder with a hole is investigated. • The effects of both flux creep and viscous flux flow on stresses are analyzed. • For the FC case, the maximal hoop tensile stress always occurs at hole edge. • For the ZFC case, the maximal hoop stress is not certain to occur at hole edge. - Abstract: The magnetoelastic problem for a superconducting cylinder with a concentric hole placed in a magnetic field is investigated, where the flux creep and viscous flux flow have been considered. The stress distributions are derived and numerical calculated for the descending field in both the zero-field cooling (ZFC) and field cooling (FC) processes. The effects of applied magnetic field, flux creep and viscous flux flow on the maximal radial and hoop stresses are discussed in detail, and some novel phenomena are found. Among others, for the FC case, the maximal hoop tensile stress always occurs at the hole edge, whist for the ZFC case, the maximal stresses including both hoop and radial stresses either occur in the vicinity of the hole or occur at the position of flux frontier in the remagnetization process. For the descending field, in general, both the flux creep and viscosity parameters have important effects on the maximal radial and hoop stresses. All these phenomena are perhaps of vital importance for the application of superconductors

  9. Quantum routing of single optical photons with a superconducting flux qubit

    Science.gov (United States)

    Xia, Keyu; Jelezko, Fedor; Twamley, Jason

    2018-05-01

    Interconnecting optical photons with superconducting circuits is a challenging problem but essential for building long-range superconducting quantum networks. We propose a hybrid quantum interface between the microwave and optical domains where the propagation of a single-photon pulse along a nanowaveguide is controlled in a coherent way by tuning the electromagnetically induced transparency window with the quantum state of a flux qubit mediated by the spin in a nanodiamond. The qubit can route a single-photon pulse using the nanodiamond into a quantum superposition of paths without the aid of an optical cavity—simplifying the setup. By preparing the flux qubit in a superposition state our cavityless scheme creates a hybrid state-path entanglement between a flying single optical photon and a static superconducting qubit.

  10. High current and high power superconducting rectifiers

    International Nuclear Information System (INIS)

    Kate, H.H.J. ten; Bunk, P.B.; Klundert, L.J.M. van de; Britton, R.B.

    1981-01-01

    Results on three experimental superconducting rectifiers are reported. Two of them are 1 kA low frequency flux pumps, one thermally and magnetically switched. The third is a low-current high-frequency magnetically switched rectifier which can use the mains directly. (author)

  11. Origin and Reduction of 1 /f Magnetic Flux Noise in Superconducting Devices

    Science.gov (United States)

    Kumar, P.; Sendelbach, S.; Beck, M. A.; Freeland, J. W.; Wang, Zhe; Wang, Hui; Yu, Clare C.; Wu, R. Q.; Pappas, D. P.; McDermott, R.

    2016-10-01

    Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1 /fα, with α ≲1 , and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular O2 is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be reduced by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more than an order of magnitude and a suppression of 1 /f magnetic flux noise power spectral density of up to a factor of 5. These advances open the door to the realization of superconducting qubits with improved quantum coherence.

  12. Superconducting flux flow digital circuits

    International Nuclear Information System (INIS)

    Martens, J.S.; Zipperian, T.E.; Hietala, V.M.; Ginley, D.S.; Tigges, C.P.; Phillips, J.M.; Siegal, M.P.

    1993-01-01

    The authors have developed a family of digital logic circuits based on superconducting flux flow transistors that show high speed, reasonable signal levels, large fan-out, and large noise margins. The circuits are made from high-temperature superconductors (HTS) and have been shown to operate at over 90 K. NOR gates have been demonstrated with fan-outs of more than 5 and fully loaded switching times less than a fixture-limited 50 ps. Ring-oscillator data suggest inverter delay times of about 40ps when using a 3-μm linewidths. Simple flip-flops have also been demonstrated showing large noise margins, response times of less than 30 ps, and static power dissipation on the order of 30 nW. Among other uses, this logic family is appropriate as an interface between logic families such as single flux quantum and conventional semiconductor logic

  13. Fast Flux Test Facility replacement of a primary sodium pump

    International Nuclear Information System (INIS)

    Krieg, S.A.; Thomson, J.D.

    1985-01-01

    The Fast Flux Test Facility is a 400 MW Thermal Sodium Cooled Fast Reactor operated by Westinghouse Hanford Company for the US Department of Energy. During startup testing in 1979, the sodium level in one of the primary sodium pumps was inadvertently raised above the normal height. This resulted in distortion of the pump shaft. Pump replacement was carried out using special maintenance equipment. Nuclear radiation and contamination were not significant problems since replacement operations were carried out shortly after startup of the Fast Flux Test Facility

  14. Superconducting flux qubits with π-junctions

    International Nuclear Information System (INIS)

    Shcherbakova, Anastasia

    2014-01-01

    In this thesis, we present a fabrication technology of Al/AlO x /Al Josephson junctions on Nb pads. The described technology gives the possibility of combining a variety of Nb-based superconducting circuits, like pi-junction phase-shifters with sub-micron Al/AlO x /Al junctions. Using this approach, we fabricated hybrid Nb/Al flux qubits with and without the SFS-junctions and studied dispersive magnetic field response of these qubits as well as their spectroscopy characteristics.

  15. Flux flow, pinning, and resistive behavior in superconducting networks

    International Nuclear Information System (INIS)

    Teitel, S.

    1991-10-01

    We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. Flux flow resistance in two dimensional Josephson junction arrays has been calculated, and related to correlations in vortex structure. Randomness has been introduced, and its effects on the superconducting transition, and vortex mobility, have been studied. We find that randomness destroys phase coherence, yet the randomness induced pinning reduces flux flow resistance at low temperatures. Vortex line fluctuations in high temperature superconductors have been studied using a three dimensional XY model. We have considered the melting of the vortex line lattice, and the entanglement and cutting of vortex lines in the vortex line liquid phase. Vortex line entangling and cutting appear to occur on the same length scales in the liquid phase. The vortex structure function has been calculated and from it, elastic properties of the vortex line liquid have been inferred. The two dimensional classical Coulomb gas, where charges map onto vortices in the superconducting system, has been simulated. The melting transitions of ordered charge (vortex) lattices have been studied, and we find evidence that these transitions do not have the critical behavior expected from standard symmetry analysis

  16. Elimination of the induced current error in magnetometers using superconducting flux transformers

    International Nuclear Information System (INIS)

    Dummer, D.; Weyhmann, W.

    1987-01-01

    The changing magnetization of a sample in a superconducting flux transformer coupled magnetometer induces a current in the transformer which in turn changes the field at the sample. This ''image'' field and the error caused by it can be eliminated by sensing the current in the loop and nulling it by feedback through a mutual inductance. We have tested the technique on the superconducting transition of indium in an applied magnetic field and shown that the observed width of the transition is greatly reduced by maintaining zero current in the flux transformer

  17. Superconducting current generators; Generateurs supraconducteurs de courant

    Energy Technology Data Exchange (ETDEWEB)

    Genevey, P [Commissariat a l' Energie Atomique, Limeil-Brevannes (France). Centre d' Etudes

    1970-07-01

    After a brief summary of the principle of energy storage and liberation with superconducting coils,two current generators are described that create currents in the range 600 to 1400 A, used for two storage experiments of 25 kJ and 50 kJ respectively. The two current generators are: a) a flux pump and b) a superconducting transformer. Both could be developed into more powerful units. The study shows the advantage of the transformer over the flux pump in order to create large currents. The efficiencies of the two generators are 95 per cent and 40 to 60 per cent respectively. (author) [French] Apres un rappel succinct du principe de stockage d'energie dans un solenoide supraconducteur et de sa liberation, nous decrivons deux generateurs de courant qui nous ont permis d'obtenir les courants necessaires (600 a 1400 A) aux experiences de stockage d'energie envisagees (27 kJ et 50 kJ): 1) - une pompe a flux, 2) - un transformateur supraconducteur. Ces generateurs sont extrapolables. Cette etude montre que si nous voulons creer un courant intense, le transformateur grace a son rendement eleve (> 95 pour cent) est preferable actuellement aux pompes a flux dont le rendement est de 40 a 60 pour cent. (auteur)

  18. Design and market considerations for axial flux superconducting electric machine design

    Science.gov (United States)

    Ainslie, M. D.; George, A.; Shaw, R.; Dawson, L.; Winfield, A.; Steketee, M.; Stockley, S.

    2014-05-01

    In this paper, the authors investigate a number of design and market considerations for an axial flux superconducting electric machine design that uses high temperature superconductors. The axial flux machine design is assumed to utilise high temperature superconductors in both wire (stator winding) and bulk (rotor field) forms, to operate over a temperature range of 65-77 K, and to have a power output in the range from 10s of kW up to 1 MW (typical for axial flux machines), with approximately 2-3 T as the peak trapped field in the bulk superconductors. The authors firstly investigate the applicability of this type of machine as a generator in small- and medium-sized wind turbines, including the current and forecasted market and pricing for conventional turbines. Next, a study is also carried out on the machine's applicability as an in-wheel hub motor for electric vehicles. Some recommendations for future applications are made based on the outcome of these two studies. Finally, the cost of YBCO-based superconducting (2G HTS) wire is analysed with respect to competing wire technologies and compared with current conventional material costs and current wire costs for both 1G and 2G HTS are still too great to be economically feasible for such superconducting devices.

  19. Thermoelectric flux effect in superconducting indium

    International Nuclear Information System (INIS)

    Van Harlingen, D.J.

    1977-01-01

    In this paper we discuss a thermoelectric effect in superconductors which provides a mechanism for studying quasiparticle relaxation and scattering processes in non-equilibrium superconductors by transport measurements. We report measurements of the thermoelecric flux effect in samples consisting of indium and lead near the In transition temperature; in this temperature range, the contribution to DELTA/sub TAU/ from the Pb is insignificant and so values of OMEGA(T) are obtained for indium. The results of our experiments may be summarized as follows: (1) we have a thermally-generated flux effect in 5 superconducting In-Pb toroidal samples, (2) experimental tests suggest that the observed effect does indeed arise from the proposed thermoelectric flux effect, (3) OMEGA(T) for indium is found to diverge as (T/sub c/ - T)/sup -3/2/ more rapidly than predicted by simple theory, (4) OMEGA(T) at T/T sub c/ = .999 is nearly 10/sup 5/ larger than initially expected, (5) OMEGA (T) roughly correlates with the magnitude of the normal state thermoelectric coefficient for our samples

  20. Coupling nitrogen-vacancy centers in diamond to superconducting flux qubits

    DEFF Research Database (Denmark)

    Marcos, D.; Wubs, Martijn; Taylor, J.M.

    2010-01-01

    We propose a method to achieve coherent coupling between nitrogen-vacancy (NV) centers in diamond and superconducting (SC) flux qubits. The resulting coupling can be used to create a coherent interaction between the spin states of distant NV centers mediated by the flux qubit. Furthermore......, the magnetic coupling can be used to achieve a coherent transfer of quantum information between the flux qubit and an ensemble of NV centers. This enables a long-term memory for a SC quantum processor and possibly an interface between SC qubits and light....

  1. Quasi-One-Dimensional Intermittent Flux Behavior in Superconducting Films

    Directory of Open Access Journals (Sweden)

    A. J. Qviller

    2012-01-01

    Full Text Available Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa_{2}Cu_{3}O_{7-δ} deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a power law, and data collapse is obtained by finite-size scaling, with the depth of the flux front used as crossover length. The intermittent behavior shows no threshold value in the applied field, in contrast to conventional flux jumping. The results strongly suggest that the quasi-one-dimensional flux jumps are of a different nature than the thermomagnetic dendritic (branching avalanches that are commonly found in superconducting films.

  2. Effect of the magnet insertion on the performance of a superconducting pump

    International Nuclear Information System (INIS)

    Kondo, M.; Inoue, K.; Koshizuka, N.; Seki, H.; Murakami, M.; Hiragushi, M.; Akiyama, S.

    2014-01-01

    Highlights: • Non-contact rotation is possible by using permanent magnets and superconductors. • It is necessary to rotate a superconducting pump stably for practical applications. • We placed a permanent magnet at the bottom to increase the stiffness. • Inserting permanent magnets was effective in increasing the rotational stability. - Abstract: For medical and semiconductor fabrication lines, an ultra-clean and impurity-free environment is often required. In order to realize such a contaminant-free environment, it is desirable to employ a completely non-contact rotating mechanism. Such a non-contact rotation is possible by using a combination of permanent magnets and bulk superconductors. Furthermore, it is necessary to rotate a superconducting pump stably for practical applications. With the aim of increasing the stiffness of rotational parts, we placed a permanent magnet at the bottom such that the superconductors are sandwiched by top and bottom magnets. It was confirmed that the stiffness could surely be improved by arranging lower permanent magnets

  3. Effect of the magnet insertion on the performance of a superconducting pump

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, M., E-mail: mb12021@shibaura-it.ac.jp [Shibaura institute of Technology, Toyosu 3-7-5, Koto-ku, Tokyo 135-8548 (Japan); Inoue, K.; Koshizuka, N. [Shibaura institute of Technology, Toyosu 3-7-5, Koto-ku, Tokyo 135-8548 (Japan); Seki, H. [Awaji Materia, Kanda ogawacho 2-3-13, Chiyoda-ku, Tokyo 101-0045 (Japan); Murakami, M. [Shibaura institute of Technology, Toyosu 3-7-5, Koto-ku, Tokyo 135-8548 (Japan); Hiragushi, M. [Seikow Chemical Engineering and Machinery Ltd., Mizudocho 4-1-31, Amagasaki, Hyogo 661-0026 (Japan); Akiyama, S. [MAG-NEO, Suwa 1-4-23, Saitama Iwatsuki-ku, Saitama 339-0007 (Japan)

    2014-09-15

    Highlights: • Non-contact rotation is possible by using permanent magnets and superconductors. • It is necessary to rotate a superconducting pump stably for practical applications. • We placed a permanent magnet at the bottom to increase the stiffness. • Inserting permanent magnets was effective in increasing the rotational stability. - Abstract: For medical and semiconductor fabrication lines, an ultra-clean and impurity-free environment is often required. In order to realize such a contaminant-free environment, it is desirable to employ a completely non-contact rotating mechanism. Such a non-contact rotation is possible by using a combination of permanent magnets and bulk superconductors. Furthermore, it is necessary to rotate a superconducting pump stably for practical applications. With the aim of increasing the stiffness of rotational parts, we placed a permanent magnet at the bottom such that the superconductors are sandwiched by top and bottom magnets. It was confirmed that the stiffness could surely be improved by arranging lower permanent magnets.

  4. Flux-lock type of superconducting fault current limiters: A comprehensive review

    Science.gov (United States)

    Badakhshan, M.; Mousavi G., S. M.

    2018-04-01

    Power systems must be developed and extended to supply the continuous enhancement of demands for electrical energy. This development of systems in addition to the integration of distributed generation (DG) units to the power systems results higher capacity of system. Hence, short circuit current of network is confronted with persistent increasing. Since exploration of high temperature superconducting (HTS) materials, superconducting fault current limiters (SFCLs) have attracted a lot of attention all over the world. There are different types of SFCLs. Flux-lock type of SFCL because of its characteristics in fault current limitation is an important category of SFCLs. This paper aims to present a comprehensive review of research activities and applications of Flux-lock type of SFCLs in power systems.

  5. Pumps for cryogenic liquids with superconducting magnetic bearings. Final report; Pumpen fuer kryogene Fluessigkeiten mit supraleitenden Magnetlagern. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, G.; Fuchs, G.; Sorber, J.; Brosche, H.; Richter, M.; Frenzel, C.

    2000-07-01

    A liquid nitrogen pump with contactless superconducting magnetic bearings was to be developed on the basis of an available motor with superconducting bearings. Contactless superconducting magnetic bearings require practically no servicing. A high demand for pumps for cryogenic liquids is expected with the impending use of hydrogen as an energy source. The pumping of liquid nitrogen was demonstrated successfully with the new test aggregate. The maximum pumped volume was 17 l/min at a lift of 0.5 m and 6 l/min at a lift of 1 m. In all, 15 hours of operation were registered in the superconducting state of the bearing, which included 2 hours of uninterrupted pump operation. The higher speed range for which magnetic bearings are optimally suited was not reached. Operation at higher frequencies was impossible either because of stronger resonance amplituees or because the power system was too weak. [German] Ziel des Vorhabens war die Entwicklung einer Pumpe fuer fluessigen Stickstoff mit beruehrungslosen supraleitenden Magnetlagern auf der Basis eines vorhandenen supraleitend gelagerten Motors. Die beruehrungslose supraleitende Magnetlager sind praktisch wartungsfrei. Ein Bedarf an Pumpen fuer kryogene Fluessigkeiten entsteht insbesondere durch den in naher Zukunft zu erwartenden Einsatz von Wasserstoff als Energietraeger. Mit dem entworfenen Aggregat wurde das Pumpen von Fluessigstickstoff erfolgreich demonstriert. Der Foerderstrom betrug bei 0,5m Foerderhoehe maximal 17 l/min; beim 1m Foerderhoehe wurden maximal 6 l/min gemessen. Es wurden insgesamt ca. 15 Betriebsstunden in supraleitenden Zustand des Lagers, darunter 2 Stunden ununterbrochener Pumpbetrieb registriert. Der hoehere Drehzahlbereich, fuer den das Magnetlager eigentlich paedestiniert ist, konnte nicht erreicht werden. Ein Betrieb bei hoeheren (Ist-)Frequenzen war nicht moeglich, entweder durch staerkere Resonanzausschlaege oder durch einen zu schwachen Antrieb. (orig.)

  6. Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire

    International Nuclear Information System (INIS)

    Clem, John R.

    2011-01-01

    I introduce a critical-state theory incorporating both flux cutting and flux transport to calculate the magnetic-field and current-density distributions inside a type-II superconducting cylinder at its critical current in a longitudinal applied magnetic field. The theory is an extension of the elliptic critical-state model introduced by Romero-Salazar and Perez-Rodriguez. The vortex dynamics depend in detail on two nonlinear effective resistivities for flux cutting (ρ(parallel)) and flux flow (ρ(perpendicular)), and their ratio r = ρ(parallel)/ρ(perpendicular). When r c (φ) that makes the vortex arc unstable.

  7. Response of fractal penetration of magnetic flux to disorder landscape in superconducting films

    Science.gov (United States)

    Ye, Zuxin; Li, Qiang; Si, W. D.; Suenaga, M.; Solovyov, V. F.; Johnson, P. D.

    2005-10-01

    Magnetic flux front and induction contours in superconducting YBa2Cu3O7-δ films with defect size stilde ξ (superconducting coherence length) and s≫ξ are studied by magneto-optical imaging. Robust self-affine spatial correlation was observed using scaling analysis in the small pinning disorder-dominated ( stilde ξ) films. The roughness exponent α was determined to be ˜0.66 , independent of numbers of defects (or the film thickness). When the disorder landscape also included a distribution of large defects (s≫ξ) , the flux front and induction contours exhibited self-similarity, with a fractal dimension D determined to be ˜1.33 using the box-counting method. The remarkably different flux penetration patterns were shown to be the manifestation of self-organized criticality at different length scales.

  8. A superconducting linear motor drive for a positive displacement bellows pump for use in the g-2 cryogenics system

    International Nuclear Information System (INIS)

    Green, M.A.

    1994-10-01

    Forced two-phase cooling of indirectly cooled magnets requires circulation of liquid helium through the magnet cooling channel. A bellows helium pump is one possible way of providing helium flow to a magnet cooling system. Since the bellows type of helium pump is immersed in liquid helium, a superconducting linear motor drive appears to be an attractive option. This report describes a linear motor drive that employs oriented permanent magnet materials such as samarium-cobalt as the stator magnet system and a superconducting loud speaker voice coil type of drive as the armature of the linear motor. This report examines drive motor requirements for a helium pump

  9. Pressurizer pump reliability analysis high flux isotope reactor

    International Nuclear Information System (INIS)

    Merryman, L.; Christie, B.

    1993-01-01

    During a prolonged outage from November 1986 to May 1990, numerous changes were made at the High Flux Isotope Reactor (HFIR). Some of these changes involved the pressurizer pumps. An analysis was performed to calculate the impact of these changes on the pressurizer system availability. The analysis showed that the availability of the pressurizer system dropped from essentially 100% to approximately 96%. The primary reason for the decrease in availability comes because off-site power grid disturbances sometimes result in a reactor trip with the present pressurizer pump configuration. Changes are being made to the present pressurizer pump configuration to regain some of the lost availability

  10. Fast Flux Test Facility sodium pump operating experience - mechanical

    International Nuclear Information System (INIS)

    Buonamici, R.

    1987-11-01

    The Heat Transport System (HTS) pumps were designed, fabricated, tested, and installed in the Fast Flux Test Facility (FFTF) Plant during the period from September 1970 through July 1977. Since completion of the installation and sodium fill in December 1978, the FFTF Plant pumps have undergone extensive testing and operation with HTS testing and reactor operation. Steady-state hydraulic and mechanical performances have been and are excellent. In all, FFTF primary and secondary pumps have operated in sodium for approximately 75,000 hours and 79,000 hours, respectively, to August 24, 1987

  11. Measurements of flux pumping activation of trapped field magnets

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, Roy; Parks, Drew; Sawh, Ravi-Persad [Texas Center for Superconductivity, 202 Houston Science Center, University of Houston, Houston, TX 77204-5002 (United States); Davey, Kent [Physics Department, 617 Science and Research Building I, University of Houston, Houston, TX 77204-5005 (United States)

    2010-11-15

    Large grains of high temperature superconducting (HTS) material can be utilized as trapped field magnets (TFMs). Persistent currents are set up in the HTS when it is cooled in a magnetic field, or exposed to a magnetic field after cooling. TFMs have been improved over the past two decades by the efforts of a large number of worldwide research groups. However, applications using TFMs have lagged, in part due to the problem of high fields needed for activation. We describe herein experiments designed to observe the behaviour of TFM activation using repeated applications of low fields (called 'pumping'). Significant partial activation is obtained using a non-uniform pumping field (e.g., a small permanent magnet) which is higher in the centre of the HTS than at the periphery. Cooling in zero field followed by pumping with such a field results in trapping the full applied field, in comparison to half of the applied field being trapped by cooling in zero field followed by application of a uniform field. We find that for partial activation by cooling in a field and subsequent activation by pumping, the resulting fields are additive. We also conclude that for activation by fluxoid pumping, creep assists the process.

  12. Computation of Pump-Leak Flux Balance in Animal Cells

    Directory of Open Access Journals (Sweden)

    Igor A. Vereninov

    2014-11-01

    Full Text Available Background/Aims: Many vital processes in animal cells depend on monovalent ion transport across the plasma membrane via specific pathways. Their operation is described by a set of nonlinear and transcendental equations that cannot be solved analytically. Previous computations had been optimized for certain cell types and included parameters whose experimental determination can be challenging. Methods: We have developed a simpler and a more universal computational approach by using fewer kinetic parameters derived from the data related to cell balanced state. A file is provided for calculating unidirectional Na+, K+, and Cl- fluxes via all major pathways (i.e. the Na/K pump, Na+, K+, Cl- channels, and NKCC, KC and NC cotransporters under a balanced state and during transient processes. Results: The data on the Na+, K+, and Cl- distribution and the pump flux of K+ (Rb+ are obtained on U937 cells before and after inhibiting the pump with ouabain. There was a good match between the results of calculations and the experimentally measured dynamics of ion redistribution caused by blocking the pump. Conclusion: The presented approach can serve as an effective tool for analyzing monovalent ion transport in the whole cell, determination of the rate coefficients for ion transfer via major pathways and studying their alteration under various conditions.

  13. Flux-quantization effects in disordered normal metal rings and superconducting networks

    International Nuclear Information System (INIS)

    Li, Qiming.

    1989-01-01

    The effects of the magnetic flux on the properties of disordered normal metal rings and bond or site diluted two-dimensional superconducting networks are investigated theoretically, with an emphasis on the quantum coherence of the electrons and the localization nature in the disordered systems. The conductance of disordered metal rings in magnetic field is obtained via the Landauer's formula through calculations of the localization length L c . The important role of the ensemble averaging and the self-averaging to obtain the half-flux-quantum h/2e conductance oscillation is demonstrated unambiguously in both rings of a strictly one-dimensional geometry and rings with a finite width. The amplitude of the localization length oscillation is found to follow a universal relation for all the numerical data: Δ(L c /L) = α(L c /L) 2 . L is the radius of the ring. The expected universal conductance fluctuations are observed for L c /L ∼ 1. For L c > L, much larger oscillation amplitudes are obtained. In the case of two-dimensional site or bond percolation superconducting networks, the nature of the eigenstates and the effects on the superconducting-to-normal phase boundary is examined by finite-size transfer matrix calculations within the mean-field Ginzburg-Landau theory of second order phase transitions

  14. Fractional-flux Little-Parks resistance oscillations in disordered superconducting Au0.7In0.3 cylinders

    International Nuclear Information System (INIS)

    Zadorozhny, Yu.; Liu, Y.

    2001-01-01

    The resistance of disordered superconducting Au 0.7 In 0.3 cylindrical films was measured as a function of applied magnetic field. In the high-temperature part of the superconducting transition regime, the resistance oscillated with a period of h/2e in units of the enclosed magnetic flux. However, at lower temperatures, the resistance peaks split. We argue that this splitting is due to the emergence of an oscillation with a period of h/4e, half of the flux quantum for paired electrons. The possible physical origin of the h/4e resistance oscillation is discussed in the context of new minima in the free energy of a disordered superconducting cylinder. (orig.)

  15. Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations

    Science.gov (United States)

    Krebs, I.; Jardin, S. C.; Günter, S.; Lackner, K.; Hoelzl, M.; Strumberger, E.; Ferraro, N.

    2017-10-01

    A self-regulating magnetic flux pumping mechanism in tokamaks that maintains the core safety factor at q ≈1 , thus preventing sawteeth, is analyzed in nonlinear 3D magnetohydrodynamic simulations using the M3D-C1 code. In these simulations, the most important mechanism responsible for the flux pumping is that a saturated (m =1 ,n =1 ) quasi-interchange instability generates an effective negative loop voltage in the plasma center via a dynamo effect. It is shown that sawtoothing is prevented in the simulations if β is sufficiently high to provide the necessary drive for the (m =1 ,n =1 ) instability that generates the dynamo loop voltage. The necessary amount of dynamo loop voltage is determined by the tendency of the current density profile to centrally peak which, in our simulations, is controlled by the peakedness of the applied heat source profile.

  16. Improvement of the superconducting magnetic levitation system for the determination of the magnetic flux quantum

    International Nuclear Information System (INIS)

    Endo, T.; Sakamoto, Y.; Shiota, F.; Nakayama, K.; Nezu, Y.; Kikuzawa, M.; Hara, K.

    1989-01-01

    The authors describe an improvement of the preliminary superconducting magnetic levitation system in progress for the absolute determination of the magnetic flux quantum. This improvement includes the development of the flux-up method to determine the flux in terms of the Josephson voltage. The improvement is essential for the determination of the magnetic flux quantum as well as of the coil current in terms of the Josephson voltage and quantized Hall resistance

  17. The vortex structure and flux creep within superconducting permanent-magnet high aspect-ratio discs

    International Nuclear Information System (INIS)

    Watson, J.H.P.; Younas, I.

    1997-01-01

    Inhomogeneous type II superconducting discs magnetized by an applied field will retain some magnetization when field is switched off so the superconducting disc will behave as a permanent magnet after flux creep has reduced to a low value.This paper examines the superconducting vortex structure within superconducting permanent-magnet high aspect-ratio discs which is consistent with the calculated magnetic field distribution.The discs, with radius R, have the axis along the z-direction and the mid-plane of the disc corresponds to z = 0. These discs with large aspect ratios in the remnant state have a region between radius r l and R where the magnetic field is reversed. Surrounding the line r = r l and z = 0 there is a region where H cl which is in the Meissner state. Near r l the vortex lines are strongly curved. For radii r l vortex lines creep to larger values of r. For radii r > r l vortex lines creep to smaller values of r, meet at r l with vortex lines of opposite sign and form a continuous loop which decreases in size and is finally annihilated in the Meissner region. Flux creep induces lossless currents in the Meissner region. (author)

  18. Suppressing relaxation in superconducting qubits by quasiparticle pumping.

    Science.gov (United States)

    Gustavsson, Simon; Yan, Fei; Catelani, Gianluigi; Bylander, Jonas; Kamal, Archana; Birenbaum, Jeffrey; Hover, David; Rosenberg, Danna; Samach, Gabriel; Sears, Adam P; Weber, Steven J; Yoder, Jonilyn L; Clarke, John; Kerman, Andrew J; Yoshihara, Fumiki; Nakamura, Yasunobu; Orlando, Terry P; Oliver, William D

    2016-12-23

    Dynamical error suppression techniques are commonly used to improve coherence in quantum systems. They reduce dephasing errors by applying control pulses designed to reverse erroneous coherent evolution driven by environmental noise. However, such methods cannot correct for irreversible processes such as energy relaxation. We investigate a complementary, stochastic approach to reducing errors: Instead of deterministically reversing the unwanted qubit evolution, we use control pulses to shape the noise environment dynamically. In the context of superconducting qubits, we implement a pumping sequence to reduce the number of unpaired electrons (quasiparticles) in close proximity to the device. A 70% reduction in the quasiparticle density results in a threefold enhancement in qubit relaxation times and a comparable reduction in coherence variability. Copyright © 2016, American Association for the Advancement of Science.

  19. Superconducting Film Flux Transformer for a Sensor of a Weak Magnetic Field

    International Nuclear Information System (INIS)

    Ichkitidze, L; Mironyuk, A

    2012-01-01

    The object of study is a superconducting film flux transformer in the form of a square shaped loop with the tapering operative strip used in a sensor of a weak magnetic field. The magnetosensitive film element based on the giant magnetoresistance effect is overlapped with the tapering operative strip of the flux transformer; it is separated from the latter by the insulator film. It is shown that the topological nanostructuring of the operative strip of the flux transformer increases its gain factor by one or more orders of magnitude, i.e. increases its efficiency, which leads to a significant improvement of important parameters of a magnetic-field sensor.

  20. Evidence for preferential flux flow at the grain boundaries of superconducting RF-quality niobium

    Science.gov (United States)

    Sung, Z.-H.; Lee, P. J.; Gurevich, A.; Larbalestier, D. C.

    2018-04-01

    The question of whether grain boundaries (GBs) in niobium can be responsible for lowered operating field (B RF) or quality factor (Q 0) in superconducting radio frequency (SRF) cavities is still controversial. Here, we show by direct DC transport across planar GBs isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain boundary when the external magnetic field lies in the GB plane. However, increasing the misalignment between the GB plane and the external magnetic field vector markedly reduces preferential flux flow along the GB. Importantly, we find that preferential GB flux flow is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain boundaries of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly the final chemical treatment and the angle between the magnetic field and the GB plane, suggests two more reasons why real cavity performance can be so variable.

  1. Feasibility of laser pumping with neutron fluxes from present-day large tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Jassby, D.L.

    1986-08-01

    The minimum fusion-neutron flux needed to observe nuclear-pumped lasing with tokamaks can be reduced substantially by optimizing neutron scattering into the laser cell, located between adjacent toroidal-field coils. The laser lines most readily pumped are probably the /sup 3/He-Ne lines at 0.633 ..mu.. and in the infrared, where the /sup 3/He-Ne gas is excited by energetic ions produced in the /sup 3/He(n,p)T reaction. These lines are expected to lase at the levels of D-T neutron flux foreseen for the TFTR in 1989 (>>10/sup 12/ n/cm/sup 2//s), while amplification should be observable at the existing levels of D-D neutron flux (greater than or equal to 5 x 10/sup 9/ n/cm/sup 2//s). Lasing on the 1.73 ..mu.. and 2.63 ..mu.. transitions of Xe may be observable at the maximum expected levels of D-T neutron flux in TFTR enhanced by scattering.

  2. Feasibility of laser pumping with neutron fluxes from present-day large tokamaks

    International Nuclear Information System (INIS)

    Jassby, D.L.

    1986-08-01

    The minimum fusion-neutron flux needed to observe nuclear-pumped lasing with tokamaks can be reduced substantially by optimizing neutron scattering into the laser cell, located between adjacent toroidal-field coils. The laser lines most readily pumped are probably the 3 He-Ne lines at 0.633 μ and in the infrared, where the 3 He-Ne gas is excited by energetic ions produced in the 3 He(n,p)T reaction. These lines are expected to lase at the levels of D-T neutron flux foreseen for the TFTR in 1989 (>>10 12 n/cm 2 /s), while amplification should be observable at the existing levels of D-D neutron flux (≥ 5 x 10 9 n/cm 2 /s). Lasing on the 1.73 μ and 2.63 μ transitions of Xe may be observable at the maximum expected levels of D-T neutron flux in TFTR enhanced by scattering

  3. Active superconducting DC fault current limiter based on flux compensation

    International Nuclear Information System (INIS)

    Shi Jing; Tang Yuejin; Wang, Chen; Zhou Yusheng; Li Jingdong; Ren Li; Chen Shijie

    2006-01-01

    With the extensive application of DC power systems, suppression of DC fault current is an important subject that guarantees system security. This paper presents an active superconducting DC fault current limiter (DC-SFCL) based on flux compensation. The DC-SFCL is composed of two superconducting windings wound on a single iron core, the primary winding is in series with DC power system, and the second winding is connected with AC power system through a PWM converter. In normal operating state, the flux in the iron core is compensated to zero, and the SFCL has no influence on DC power system. In the case of DC system accident, through regulating the active power exchange between the SFCL's second winding and the AC power system, the current on the DC side can be limited to different level complying with the system demand. Moreover, the PWM converter that interface the DC system and AC system can be controlled as a reactive power source to supply voltage support for the AC side, which has little influence on the performance of SFCL. Using MATLAB SIMULINK, the mathematic model of the DC-SFCL is created, simulation results validate the dynamics of system, and the performance of DC-SFCL is confirmed

  4. The Pressure and Magnetic Flux Density Analysis of Helical-Type DC Electromagnetic Pump

    International Nuclear Information System (INIS)

    Lee, Geun Hyeong; Kim, Hee Reyoung

    2016-01-01

    The developed pressure was made by only electromagnetic force eliminating probability of impurities contact, therefore the high reactivity materials such as alkali were best match to electromagnetic pump. The heavy ion accelerator facility by Rare Isotope Science Project (RISP) in Korea is trying to construct accelerator using liquid lithium for high efficiency of acceleration by decreasing charge state. The helical-type DC electromagnetic pump was employed to make a charge stripper that decrease charge state of heavy ion. The specification of electromagnetic pump was developed pressure of 15 bar with flowrate of 6 cc/s in the condition of 200℃. The pressure of DC electromagnetic pump was analyzed in the aspects of current and number of duct turns. The developed pressure was almost proportional to input current because relatively low flowrate made negligible of the electromotive force and hydraulic pressure drop. The pressure and magnetic flux density of helical-type DC electromagnetic pump were analyzed. The pressure was proportion to input current and number of duct turns, and magnetic flux density was higher when ferromagnet was applied at electromagnetic pump. It seems that number of duct turns could be increase and ferromagnet could be applied in order to increase pressure of DC electromagnetic pump with constant input current

  5. Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

    International Nuclear Information System (INIS)

    Ciovati, G.; Geng, R.; Lushtak, Y.; Manini, P.; Maccallini, E.; Stutzman, M.

    2017-01-01

    The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF tests of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. The results showed that the cavity performance was not affected by the pump up to the quench gradient of 34 MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.

  6. Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, G., E-mail: gciovati@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Geng, R. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Lushtak, Y.; Manini, P.; Maccallini, E. [SAES Getters, S.p.A, Viale Italia, 77, 20020 Lainate, MI (Italy); Stutzman, M. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)

    2017-01-11

    The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF tests of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. The results showed that the cavity performance was not affected by the pump up to the quench gradient of 34 MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.

  7. Single-flux-quantum circuit technology for superconducting radiation detectors

    International Nuclear Information System (INIS)

    Fujimaki, Akira; Onogi, Masashi; Matsumoto, Tomohiro; Tanaka, Masamitsu; Sekiya, Akito; Hayakawa, Hisao; Yorozu, Shinichi; Terai, Hirotaka; Yoshikawa, Nobuyuki

    2003-01-01

    We discuss the application of the single-flux-quantum (SFQ) logic circuits to multi superconducting radiation detectors system. The SFQ-based analog-to-digital converters (ADCs) have the advantage in current sensitivity, which can reach less than 10 nA in a well-tuned ADC. We have also developed the design technology of the SFQ circuits. We demonstrate high-speed operation of large-scale integrated circuits such as a 2x2 cross/bar switch, arithmetic logic unit, indicating that our present SFQ technology is applicable to the multi radiation detectors system. (author)

  8. Flux pinning by voids in surface-oxidized superconducting niobium and vanadium

    International Nuclear Information System (INIS)

    Meij, G.P. van der.

    1984-01-01

    This thesis describes a study of flux pinning by small voids (roughly 10 nm) in the type II superconductors niobium and vanadium. These voids were created in rectangular foils (with typical dimensions of 30x3x0.2 mm) during an irradiation with fast neutrons in the High Flux Reactor at Petten at temperatures between 400 and 1000 0 C. The pinning force per unit volume is determined from the magnetic properties of the superconducting samples. The experiments were carried out in a slowly ramped magnetic field, as well as in a combination of a static and a much smaller alternating field. (Auth.)

  9. Dynamic behavior of superconducting flux qubit excited by a series of electromagnetic pulses

    International Nuclear Information System (INIS)

    Kiyko, A.S.; Omelyanchouk, A.N.; Shevchenko, S.N.

    2007-01-01

    We study theoretically the behavior of the superconducting flux qubit subjected to a series of electromagnetic pulses. The possibility of controlling system state via changing the parameters of the pulse is studied. We calculated the phase shift in a tank circuit weakly coupled to the qubit which can be measured by the impedance measurement technique. For the flux qubit we consider the possibility of estimating the relaxation rate from the impedance measurements by varying the delay time between the pulses

  10. Effect of Magnetic Flux Density and Applied Current on Temperature, Velocity and Entropy Generation Distributions in MHD Pumps

    Directory of Open Access Journals (Sweden)

    M. Kiyasatfar

    2011-01-01

    Full Text Available In the present study, simulation of steady state, incompressible and fully developed laminar flow has been conducted in a magneto hydrodynamic (MHD pump. The governing equations are solved numerically by finite-difference method. The effect of the magnetic flux density and current on the flow and temperature distributions in a MHD pump is investigated. The obtained results showed that controlling the flow and the temperature is possible through the controlling of the applied current and the magnetic flux. Furthermore, the effects of the magnetic flux density and current on entropy generation in MHD pump are considered. Our presented numerical results are in good agreement with the experimental data showed in literature.

  11. 'Speedy' superconducting circuits

    International Nuclear Information System (INIS)

    Holst, T.

    1994-01-01

    The most promising concept for realizing ultra-fast superconducting digital circuits is the Rapid Single Flux Quantum (RSFQ) logic. The basic physical principle behind RSFQ logic, which include the storage and transfer of individual magnetic flux quanta in Superconducting Quantum Interference Devices (SQUIDs), is explained. A Set-Reset flip-flop is used as an example of the implementation of an RSFQ based circuit. Finally, the outlook for high-temperature superconducting materials in connection with RSFQ circuits is discussed in some details. (au)

  12. Self-pumping effects and radiation linewidth of Josephson flux-flow oscillators

    DEFF Research Database (Denmark)

    Koshelets, V.P.; Shitov, S.V.; Shchukin, A.V.

    1997-01-01

    Flux-flow oscillators (FFO's) are being developed for integration with a SIS mixer for use in submillimeter wave receivers, The present work contains a detailed experimental study of the dc, microwave, and noise properties of Nb-AlOx-Nb FFO's, A model based on the Josephson self-pumping effect...

  13. Superconducting nanostructured materials

    International Nuclear Information System (INIS)

    Metlushko, V.

    1998-01-01

    Within the last year it has been realized that the remarkable properties of superconducting thin films containing a periodic array of defects (such as sub-micron sized holes) offer a new route for developing a novel superconducting materials based on precise control of microstructure by modern photolithography. A superconductor is a material which, when cooled below a certain temperature, loses all resistance to electricity. This means that superconducting materials can carry large electrical currents without any energy loss--but there are limits to how much current can flow before superconductivity is destroyed. The current at which superconductivity breaks down is called the critical current. The value of the critical current is determined by the balance of Lorentz forces and pinning forces acting on the flux lines in the superconductor. Lorentz forces proportional to the current flow tend to drive the flux lines into motion, which dissipates energy and destroys zero resistance. Pinning forces created by isolated defects in the microstructure oppose flux line motion and increase the critical current. Many kinds of artificial pinning centers have been proposed and developed to increase critical current performance, ranging from dispersal of small non-superconducting second phases to creation of defects by proton, neutron or heavy ion irradiation. In all of these methods, the pinning centers are randomly distributed over the superconducting material, causing them to operate well below their maximum efficiency. We are overcome this drawback by creating pinning centers in aperiodic lattice (see Fig 1) so that each pin site interacts strongly with only one or a few flux lines

  14. Stacked magnet superconducting bearing

    International Nuclear Information System (INIS)

    Rigney, T.K. II; Saville, M.P.

    1993-01-01

    A superconducting bearing is described, comprising: a plurality of permanent magnets magnetized end-to-end and stacked side-by-side in alternating polarity, such that flux lines flow between ends of adjacent magnets; isolating means, disposed between said adjacent magnets, for reducing flux leakage between opposing sides of said adjacent magnets; and a member made of superconducting material having at least one surface in communication with said flux lines

  15. Development of Novel High Temperature Superconducting Detectors Based on Flux Activation and Ultrafast Dynamics

    National Research Council Canada - National Science Library

    Frankel, Anatoly

    1998-01-01

    It is proposed to study quasiparticle (QP) relaxation dynamics and flux mechanism of HTS using pump/probe femtosecond spectroscopy and nonequilibrium photoresponse in the presence of a magnetic field (and/or bias current...

  16. High-Tc superconducting electric motors

    International Nuclear Information System (INIS)

    Schiferl, R.; Stein, J.

    1992-01-01

    In this paper, the advantages and limitations of using superconductors in motors are discussed. A synchronous motor with a high temperature superconducting field winding for pump and fan drive applications is described and some of its unique design features are identified. A 10,000 horsepower superconducting motor design is presented. The critical field and current density requirements for high temperature superconducting wire in motors is discussed. Finally, recent progress in superconducting wire performance is presented

  17. Superconducting 7 T Wave Length Shifter for BESSY-II

    CERN Document Server

    Borovikov, V M; Fedurin, M G; Repkov, V V; Karpov, G V; Kulipanov, G N; Kuzin, M V; Mezentsev, N A; Shkaruba, V A; Krämer, Dietrich; Richter, D

    2001-01-01

    A superconducting 3-pole Wave Length Shifter (WLS) with a maximum field of 7 T was fabricated and tested by BINP in collaboration with BESSY-II. The radiation point is fixed in the center of WLS at any field level by using two correctors. The magnetic field is stabilized with an accuracy of 10 sup - sup 4 at 7 T by a feedback system based on NMR probes and magnetic flux pumps. Persistent current operation mode is enabled by using superconducting persistent keys. The magnetic field homogeneity of 10 sup - sup 4 at 7 T is obtained as a result of shimming in the aperture of the magnet. A protection system based on cold diodes and dump resistors prevents the destruction of superconducting coils during the quench. Two screens with temperatures of 20 and 60 K cooled by cooling machine, two recondensers, HTSC current leads and cevlar suspensions of helium volume are used to decrease liquid helium consumption. The main features and operating mode of the WLS are described.

  18. Test Results of a 1.2 kg/s Centrifugal Liquid Helium Pump for the ATLAS Superconducting Toroid Magnet System

    CERN Document Server

    Pengo, R; Passardi, Giorgio; Pirotte, O; ten Kate, H H J

    2002-01-01

    The toroid superconducting magnet of ATLAS-LHC experiment at CERN will be indirectly cooled by means of forced flow of liquid helium at about 4.5 K. A centrifugal pump will be used, providing a mass flow of 1.2 kg/s and a differential pressure of 40 kPa (ca. 400 mbar) at about 4300 rpm. Two pumps are foreseen, one for redundancy, in order to feed in parallel the cooling circuits of the Barrel and the two End-Caps toroid magnets. The paper describes the tests carried out at CERN to measure the characteristic curves, i.e. the head versus the mass flow at different rotational speeds, as well as the pump total efficiency. The pump is of the "fullemission" type, i.e. with curved blades and it is equipped with an exchangeable inducer. A dedicated pump test facility has been constructed at CERN, which includes a Coriolis-type liquid helium mass flow meter. This facility is connected to the helium refrigerator used for the tests at CERN of the racetrack magnets of the Barrel and of the End-Cap toroids.

  19. The study of heat flux for disruption on experimental advanced superconducting tokamak

    Science.gov (United States)

    Yang, Zhendong; Fang, Jianan; Gong, Xianzu; Gan, Kaifu; Luo, Jiarong; Zhao, Hailin; Cui, Zhixue; Zhang, Bin; Chen, Meiwen

    2016-05-01

    Disruption of the plasma is one of the most dangerous instabilities in tokamak. During the disruption, most of the plasma thermal energy is lost, which causes damages to the plasma facing components. Infrared (IR) camera is an effective tool to detect the temperature distribution on the first wall, and the energy deposited on the first wall can be calculated from the surface temperature profile measured by the IR camera. This paper concentrates on the characteristics of heat flux distribution onto the first wall under different disruptions, including the minor disruption and the vertical displacement events (VDE) disruption. Several minor disruptions have been observed before the major disruption under the high plasma density in experimental advanced superconducting tokamak. During the minor disruption, the heat fluxes are mainly deposited on the upper/lower divertors. The magnetic configuration prior to the minor disruption is a lower single null with the radial distance between the two separatrices in the outer midplane dRsep = -2 cm, while it changes to upper single null (dRsep = 1.4 cm) during the minor disruption. As for the VDE disruption, the spatial distribution of heat flux exhibits strong toroidal and radial nonuniformity, and the maximum heat flux received on the dome plate can be up to 11 MW/m2.

  20. The Path to High Q-Factors in Superconducting Accelerating Cavities: Flux Expulsion and Surface Resistance Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Martinello, Martina [Illinois Inst. of Technology, Chicago, IL (United States)

    2016-12-01

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  1. The path to high Q-factors in superconducting accelerating cavities: Flux expulsion and surface resistance optimization

    Science.gov (United States)

    Martinello, Martina

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  2. Study of particle pumping characteristics for different pumping geometries in JT-60U and DIII-D divertors

    International Nuclear Information System (INIS)

    Takenaga, H.; Sakasai, A.; Kubo, H.

    2001-01-01

    Particle pumping characteristics were compared between pumping from the inner side private flux region (IPP) and pumping from both sides of the private flux region (BPP) in the JT-60U W shaped divertor, and between JT-60U IPP and pumping in the DIII-D lower baffled divertor. The pumping flux for BPP is smaller than that for IPP by about a factor of 2 with weak in-out asymmetry of recycling neutral flux and by a factor of 3.5-6.5 with strong in-out asymmetry. The reduction of the pumping flux for BPP is consistent with Monte Carlo simulations, where backflow at the outer pumping slot is observed due to in-out recycling asymmetry. The pumping flux in DIII-D at I p =0.8 MA and B T =1.6 T is comparable to or smaller than that for JT-60U IPP at I p =1.0 MA, B T =3.8 T and I p =1.5 MA, B T =3.5 T in the same density regime. In the DIII-D divertor with pumping from the private flux region, the pumping flux decreases with increasing in-out asymmetry. The pumping flux normalized by the integrated D α emission over the whole plasma exhibits a similar dependence on the distance between the pumping slot and the strike point in JT-60U IPP and the DIII-D lower divertor with pumping through the outer divertor plasma region. (author)

  3. Balance of unidirectional monovalent ion fluxes in cells undergoing apoptosis: why does Na+/K+ pump suppression not cause cell swelling?

    Science.gov (United States)

    Yurinskaya, Valentina E; Rubashkin, Andrey A; Vereninov, Alexey A

    2011-05-01

    Cells dying according to the apoptotic program, unlike cells dying via an unprogrammed mode, are able to avoid swelling and osmotic bursting with membrane disruption.There are indications that apoptosis is accompanied by suppression of the Na+/K+ pump and changes in the K+ and Cl− channels. It remains unclear how ion fluxes through individual ion pathways are integrated so as to induce loss of intracellular ions and concomitant apoptotic volume decrease. A decrease in activity of the sodium pump during apoptosis should cause cell swelling rather than shrinkage. We have made the first systemic analysis of the monovalent ion flux balance in apoptotic cells. Experimental data were obtained for human U937 cells treated with staurosporine for 4–5 h, which is known to induce apoptosis. The data include cellular Cl− content and fluxes, K+, Na+, water content and ouabain-sensitive and -resistant Rb+ fluxes.Unidirectional monovalent ion fluxeswere calculated using these data and a cell model comprising the double Donnan system with the Na+/K+ pump, Cl−, K+, Na+ channels, the Na+–K+–2Cl−cotransporter (NKCC), the Na+–Cl− cotransporter (NC), and the equivalent Cl−/Cl− exchange.Apoptotic cell shrinkage was found to be caused, depending on conditions, either by an increase in the integral channel permeability of membrane for K+ or by suppression of the pump coupledwith a decrease in the integral channel permeability of membrane for Na+. The decrease in the channel permeability of membrane for Na+ plays a crucial role in cell dehydration in apoptosis accompanied by suppression of the pump. Supplemental Table S1 is given for easy calculating flux balance under specified conditions.

  4. Superconducting Qubit with Integrated Single Flux Quantum Controller Part II: Experimental Characterization

    Science.gov (United States)

    Leonard, Edward, Jr.; Beck, Matthew; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

    We describe the characterization of a single flux quantum (SFQ) pulse generator cofabricated with a superconducting quantum circuit on a single chip. Resonant trains of SFQ pulses are used to induce coherent qubit rotations on the Bloch sphere. We describe the SFQ drive characteristics of the qubit at the fundamental transition frequency and at subharmonics (ω01 / n , n = 2 , 3 , 4 , ⋯). We address the issue of quasiparticle poisoning due to the proximal SFQ pulse generator, and we characterize the fidelity of SFQ-based rotations using randomized benchmarking. Present address: IBM T.J. Watson Research Center.

  5. A superconducting microcalorimeter for low-flux detection of near-infrared single photons

    International Nuclear Information System (INIS)

    Dreyling-Eschweiler, Jan

    2014-07-01

    This thesis covers the development and the characterization of a single photon detector based on a superconducting microcalorimeter. The detector development is motivated by the Any Light Particle Search II (ALPS II) experiment at DESY in Hamburg, which searches for weakly interacting sub-eV particles (WISPs). Therefore, a detection of low-fluxes of 1064 nm light is required. The work is divided in three analyses: the characterization of a milli-kelvin (mK) cryostat, the characterization of superconducting sensors for single photon detection, and the determination of dark count rates concerning 1064 nm signals. Firstly, an adiabatic demagnetization refrigerator (ADR) is characterized, which allows to reach mK-temperatures. During commissioning, the ADR cryostat is optimized and prepared to stably cool superconducting sensors at 80 mK±25 μK. It is found that sensors can be continuously operated for ∝20 h before recharging the system in -4 s -1 . By operating a fiber-coupled TES, it is found that the dark count rate for 1064 nm signals is dominated by pile-up events of near-infrared thermal photons coming through the fiber from the warm environment. Considering a detection efficiency of ∝18 %, a dark count rate of 8.6 . 10 -3 s -1 is determined for 1064 nm ALPS photons.Concerning ALPS II, this results in a sensitivity gain compared to the ALPS I detector. Furthermore, this thesis is the starting point of TES detector development in Hamburg, Germany.

  6. The study of heat flux for disruption on experimental advanced superconducting tokamak

    International Nuclear Information System (INIS)

    Yang, Zhendong; Fang, Jianan; Luo, Jiarong; Cui, Zhixue; Gong, Xianzu; Gan, Kaifu; Zhao, Hailin; Zhang, Bin; Chen, Meiwen

    2016-01-01

    Disruption of the plasma is one of the most dangerous instabilities in tokamak. During the disruption, most of the plasma thermal energy is lost, which causes damages to the plasma facing components. Infrared (IR) camera is an effective tool to detect the temperature distribution on the first wall, and the energy deposited on the first wall can be calculated from the surface temperature profile measured by the IR camera. This paper concentrates on the characteristics of heat flux distribution onto the first wall under different disruptions, including the minor disruption and the vertical displacement events (VDE) disruption. Several minor disruptions have been observed before the major disruption under the high plasma density in experimental advanced superconducting tokamak. During the minor disruption, the heat fluxes are mainly deposited on the upper/lower divertors. The magnetic configuration prior to the minor disruption is a lower single null with the radial distance between the two separatrices in the outer midplane dR_s_e_p = −2 cm, while it changes to upper single null (dR_s_e_p = 1.4 cm) during the minor disruption. As for the VDE disruption, the spatial distribution of heat flux exhibits strong toroidal and radial nonuniformity, and the maximum heat flux received on the dome plate can be up to 11 MW/m"2.

  7. Linearity of high-Tc dc superconducting quantum interference device operated in a flux-locked loop

    International Nuclear Information System (INIS)

    Nichols, D.G.; Dantsker, E.; Kleiner, R.; Mueck, M.; Clarke, J.

    1996-01-01

    Measurements have been made of the linearity of a high transition temperature dc superconducting quantum interference device (SQUID) operated at 77 K with 130 kHz flux modulation in a flux-locked loop. The degree of nonlinearity was determined from harmonic generation. A sinusoidal magnetic flux with harmonic content less than -130 dB was applied to the SQUID, which was cooled in a magnetic field below 10 -7 T, and the harmonics at the output of the flux-locked loop were measured with a spectrum analyzer. For input signals at frequencies up to 248 Hz and amplitudes up to 20Φ 0 rms (Φ 0 is the flux quantum), the second, third, and fourth harmonics were each at least 115 dB below the fundamental. At higher frequencies the harmonic content began to increase because of the reduction in the open-loop gain of the flux-locked loop. The magnitude of the harmonics was not measurably changed when the SQUID was cooled in a field of 100 μT. The amplitudes of the even harmonics depended critically on the amplitude of the 130 kHz flux modulation, and became zero when its peak-to-peak value was precisely Φ 0 /2. copyright 1996 American Institute of Physics

  8. Insulation systems for superconducting transmission cables

    DEFF Research Database (Denmark)

    Tønnesen, Ole

    1996-01-01

    the electrical insulation is placed outside both the superconducting tube and the cryostat. The superconducting tube is cooled by liquid nitrogen which is pumped through the hollow part of the tube.2) The cryogenic dielectric design, where the electrical insulation is placed inside the cryostat and thus is kept...

  9. Pump

    International Nuclear Information System (INIS)

    Mole, C.J.

    1983-01-01

    An electromagnetic pump for circulating liquid -metal coolant through a nuclear reactor wherein opposite walls of a pump duct serve as electrodes to transmit current radially through the liquid-metal in the ducts. A circumferential electric field is supplied to the liquid-metal by a toroidal electromagnet which has core sections interposed between the ducts. The windings of the electromagnet are composed of metal which is superconductive at low temperatures and the electromagnet is maintained at a temperature at which it is superconductive by liquid helium which is fed through the conductors which supply the excitation for the electromagnet. The walls of the ducts joining the electrodes include metal plates insulated from the electrodes backed up by insulators so that they are capable of withstanding the pressure of the liquid-metal. These composite wall structures may also be of thin metal strips of low electrical conductivity backed up by sturdy insulators. (author)

  10. Experimental characterization of the flux-line lattice in superconducting V3Si

    International Nuclear Information System (INIS)

    Christen, D.; Chang, Y.; Kerchner, H.; Larson, B.; Narayan, J.; SeKula, S.

    1983-01-01

    Several microscopic properties of the flux-line lattice (FLL) in three separate single crystals of V 3 Si have been investigated by means of small-angle neutron diffraction. These low-field FLL characterizations have been correlated with the following material and superconducting properties: the real crystal symmetry parallel to the applied magnetic field; the micro-structure as determined by TEM; magnetic irreversibilities in the mixed state; reversible flux-line motion in ac response; martensitic structural transformation observed by X-ray diffraction. The three samples, V 3 Si-MP3, -MP4, and -MP5 possessed different defect structures, and this was manifested foremost in the FLL perfection. At low field (B 0-.5 T, but a highly mosaic, nearly polycrystalline FLL at lower fields. Sample MP4 contained large (500-1000 A) incoherent precipitates, and showed only a polycrystalline FLL at low field. In both MP3 and MP5, distinct anisotropic correlations were observed between the FLL morphology and the real-crystal direction along the applied field. The FLL perfection was strongly dependent on the growth history. The peak width history dependence for two different scattering geometries can be qualitatively modeled by proposed flux-pinning mechanisms. Quantitative comparisons with critical current measurements, however, are not totally reconcilable

  11. Elastic flux creep in the mixed state of superconducting L2-xCexCuO4 single crystals

    International Nuclear Information System (INIS)

    Crusellas, M.A.; Fabrega, L.; Fontcuberta, J.; Martinez, B.; Obradors, X.; Pinol, S.

    1994-01-01

    We have performed measurements of the I-V characteristics and magnetic relaxation on L 2-x Ce x CuO 4 (L = Pr, Sm) superconducting single crystals (H//c), well below the critical temperature (T c ∼ 20 K). From both sets of data we have determined the current dependence of the effective flux creep energy barriers. An U(J) ∼-1nJ has been clearly identified in a region of the (H,T) plane. The relevance of the elastic properties of the vortex system on the flux creep energies is discussed. (orig.)

  12. Origin and Reduction of 1/f Magnetic Flux Noise in Superconducting Devices

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P.; Sendelbach, S.; Beck, M. A.; Freeland, J. W.; Wang, Zhe; Wang, Hui; Yu, Clare C.; Wu, R. Q.; Pappas, D. P.; McDermott, R.

    2016-10-01

    Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1=fα, with α ≲ 1, and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular O2 is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be reduced by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more than an order of magnitude and a suppression of 1=f magnetic flux noise power spectral density of up to a factor of 5. These advances open the door to the realization of superconducting qubits with improved quantum coherence.

  13. Magnetic-Flux Pumping in High-Performance, Stationary Plasmas with Tearing Modes

    International Nuclear Information System (INIS)

    Petty, C. C.; Austin, M. E.; Holcomb, C. T.; Jayakumar, R. J.; La Haye, R. J.; Luce, T. C.; Makowski, M. A.; Politzer, P. A.; Wade, M. R.

    2009-01-01

    Analysis of the change in the magnetic field pitch angles during edge localized mode events in high performance, stationary plasmas on the DIII-D tokamak shows rapid (<1 ms) broadening of the current density profile, but only when a m/n=3/2 tearing mode is present. This observation of poloidal magnetic-flux pumping explains an important feature of this scenario, which is the anomalous broadening of the current density profile that beneficially maintains the safety factor above unity and forestalls the sawtooth instability

  14. Local imaging of magnetic flux in superconducting thin films

    International Nuclear Information System (INIS)

    Shapoval, Tetyana

    2010-01-01

    Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-μm-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa 2 Cu 3 O 7-δ thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)

  15. Superconducting machines. Chapter 4

    International Nuclear Information System (INIS)

    Appleton, A.D.

    1977-01-01

    A brief account is given of the principles of superconductivity and superconductors. The properties of Nb-Ti superconductors and the method of flux stabilization are described. The basic features of superconducting d.c. machines are illustrated by the use of these machines for ship propulsion, steel-mill drives, industrial drives, aluminium production, and other d.c. power supplies. Superconducting a.c. generators and their design parameters are discussed. (U.K.)

  16. Enhanced flux pinning properties in superconducting YBa2Cu3O7−z films by a novel chemical doping approach

    International Nuclear Information System (INIS)

    Wang, W.T.; Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z.; Zhang, H.; Cheng, C.H.; Zhao, Y.

    2013-01-01

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa 2 Cu 3 O 7−z (YBCO) films were prepared on (0 0 l) LaAlO 3 substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T c spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping

  17. Flux pinning and flux flow studies in superconductors using flux flow noise techniques. Progress report, April 1, 1976--December 17, 1976

    International Nuclear Information System (INIS)

    Joiner, W.C.H.

    1976-12-01

    Measurements of flux flow noise power spectra have been combined with critical current measurements and measurements of current-voltage characteristics to study flux flow and local pinning interactions effective during flux flow. A model of flux flow noise generation in the presence of local pinning interactions is developed and applied to situations where pinning is dominated by: (1) grain boundaries, (2) normal metal precipitates in a superconducting matrix, (3) gross deformation producing a critical current peak effect, and (4) surface grooves imposed on a sample surface. In the case of pinning caused by normal metal precipitates in a superconducting matrix, unusual training and hysterisis effects are observed in the flux flow characteristics. The greater sensitivity of noise spectra, as compared with bulk critical current measurements, in obtaining a detailed picture of flux flow is emphasized

  18. Measurement of kinetic inductance of superconducting wires and application for measuring flux state of Josephson-junction loops

    Energy Technology Data Exchange (ETDEWEB)

    Shimazu, Y.; Yokoyama, T

    2004-10-01

    In order to realize strong coupling in a system of multiple flux qubits with a DC-SQUID, the use of kinetic inductance is advantageous because it can be much larger than geometrical inductance for narrow superconducting wires. We measured the inductance associated with narrow Al wires, and estimated the contributions of kinetic and geometrical inductances. The London penetration depth which determines the kinetic inductance is evaluated. We fabricated samples of two Josephson-junction loops and a DC-SQUID which are all coupled with kinetic inductances. The observed magnetic flux due to the loops is in good agreement with the result of numerical simulation based on the estimated inductances.

  19. Superconductivity: Phenomenology

    International Nuclear Information System (INIS)

    Falicov, L.M.

    1988-08-01

    This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect

  20. Pierre Gorce working on a helium pump.

    CERN Multimedia

    1975-01-01

    This type of pump was designed by Mario Morpurgo, to circulate liquid helium in superconducting magnets wound with hollow conductors. M. Morpurgo, Design and construction of a pump for liquid helium, CRYIOGENICS, February 1977, p. 91

  1. A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS

    Energy Technology Data Exchange (ETDEWEB)

    Hazra, Soumitra; Nandy, Dibyendu [Department of Physical Sciences, Indian Institute of Science Education and Research, Kolkata (India)

    2016-11-20

    At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting for the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.

  2. A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS

    International Nuclear Information System (INIS)

    Hazra, Soumitra; Nandy, Dibyendu

    2016-01-01

    At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting for the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.

  3. Superconducting Qubit with Integrated Single Flux Quantum Controller Part I: Theory and Fabrication

    Science.gov (United States)

    Beck, Matthew; Leonard, Edward, Jr.; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

    As the size of quantum processors grow, so do the classical control requirements. The single flux quantum (SFQ) Josephson digital logic family offers an attractive route to proximal classical control of multi-qubit processors. Here we describe coherent control of qubits via trains of SFQ pulses. We discuss the fabrication of an SFQ-based pulse generator and a superconducting transmon qubit on a single chip. Sources of excess microwave loss stemming from the complex multilayer fabrication of the SFQ circuit are discussed. We show how to mitigate this loss through judicious choice of process workflow and appropriate use of sacrificial protection layers. Present address: IBM T.J. Watson Research Center.

  4. Local imaging of magnetic flux in superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shapoval, Tetyana

    2010-01-26

    Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-{mu}m-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)

  5. Giant flux jumps through a thin superconducting Nb film in a vortex free region

    International Nuclear Information System (INIS)

    Tsindlekht, M.I.; Genkin, V.M.; Felner, I.; Zeides, F.; Katz, N.; Gazi, Š.; Chromik, Š.

    2016-01-01

    Highlights: Giant magnetic flux jumps into thin-walled cylinder were measured using peak up coil method in a swept magnetic field. Magnetic moment jumps were observed in magnetic fields lower and above Hc1. - Abstract: We measure the dynamics of magnetic field penetration into thin-walled superconducting niobium cylinders. It is shown that magnetic field penetrates through the wall of a cylinder in a series of giant jumps with amplitude 1 - 2 mT and duration of less than a microsecond in a wide range of magnetic fields, including the vortex free region. Surprisingly, the jumps take place when the total current in the wall, not the current density, exceeds a critical value. In addition, there are small jumps and/or smooth penetration, but their contribution reaches only ≃ 20 % of the total penetrating flux. The number of jumps decreases with increased temperature. Thermomagnetic instabilities cannot explain the experimental observations.

  6. Giant flux jumps through a thin superconducting Nb film in a vortex free region

    Energy Technology Data Exchange (ETDEWEB)

    Tsindlekht, M.I., E-mail: mtsindl@vms.huji.ac.il [The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Genkin, V.M.; Felner, I.; Zeides, F.; Katz, N. [The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Gazi, Š.; Chromik, Š. [The Institute of Electrical Engineering SAS, Dúbravská cesta 9, 84104 Bratislava (Slovakia)

    2016-10-15

    Highlights: Giant magnetic flux jumps into thin-walled cylinder were measured using peak up coil method in a swept magnetic field. Magnetic moment jumps were observed in magnetic fields lower and above Hc1. - Abstract: We measure the dynamics of magnetic field penetration into thin-walled superconducting niobium cylinders. It is shown that magnetic field penetrates through the wall of a cylinder in a series of giant jumps with amplitude 1 - 2 mT and duration of less than a microsecond in a wide range of magnetic fields, including the vortex free region. Surprisingly, the jumps take place when the total current in the wall, not the current density, exceeds a critical value. In addition, there are small jumps and/or smooth penetration, but their contribution reaches only ≃ 20 % of the total penetrating flux. The number of jumps decreases with increased temperature. Thermomagnetic instabilities cannot explain the experimental observations.

  7. Superconducting three element synchronous ac machine

    International Nuclear Information System (INIS)

    Boyer, L.; Chabrerie, J.P.; Mailfert, A.; Renard, M.

    1975-01-01

    There is a growing interest in ac superconducting machines. Of several new concepts proposed for these machines in the last years one of the most promising seems to be the ''three elements'' concept which allows the cancellation of the torque acting on the superconducting field winding, thus overcoming some of the major contraints. This concept leads to a device of induction-type generator. A synchronous, three element superconducting ac machine is described, in which a room temperature, dc fed rotating winding is inserted between the superconducting field winding and the ac armature. The steady-state machine theory is developed, the flux linkages are established, and the torque expressions are derived. The condition for zero torque on the field winding, as well as the resulting electrical equations of the machine, are given. The theoretical behavior of the machine is studied, using phasor diagrams and assuming for the superconducting field winding either a constant current or a constant flux condition

  8. Four-junction superconducting circuit

    Science.gov (United States)

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  9. Pumping behavior of sputtering ion pump

    Energy Technology Data Exchange (ETDEWEB)

    Chou, T.S.; Bittner, J.; Schuchman, J.

    1991-12-31

    To optimize the design of a distributed ion pump (DIP) for the Superconducting X-Ray Lithography Source (SXLS) the stability of the rotating electron cloud at very high magnetic field beyond transition, must be re-examined. In this work the pumping speed and frequency spectrum of a DIP at various voltages (1 to 10 KV) and various magnetic fields (0.1 to 4 Tesla) are measured. Three cell diameters 10 mm, 5 mm and 2.5 mm, each 8 mm long, and with 3 or 4 mm gaps between anode and cathode are investigated. In this study both the titanium cathodes and the stainless steel anode plates are perforated with holes comparable in size to the anode cell diameters. Only the partially saturated pumping behavior is under investigation. The ultimate pressure and conditioning of the pump will be investigated at a later date when the stability criterion for the electron cloud is better understood.

  10. Pumping behavior of sputtering ion pump

    Energy Technology Data Exchange (ETDEWEB)

    Chou, T.S.; Bittner, J.; Schuchman, J.

    1991-01-01

    To optimize the design of a distributed ion pump (DIP) for the Superconducting X-Ray Lithography Source (SXLS) the stability of the rotating electron cloud at very high magnetic field beyond transition, must be re-examined. In this work the pumping speed and frequency spectrum of a DIP at various voltages (1 to 10 KV) and various magnetic fields (0.1 to 4 Tesla) are measured. Three cell diameters 10 mm, 5 mm and 2.5 mm, each 8 mm long, and with 3 or 4 mm gaps between anode and cathode are investigated. In this study both the titanium cathodes and the stainless steel anode plates are perforated with holes comparable in size to the anode cell diameters. Only the partially saturated pumping behavior is under investigation. The ultimate pressure and conditioning of the pump will be investigated at a later date when the stability criterion for the electron cloud is better understood.

  11. Controllable conditional quantum oscillations and quantum gate operations in superconducting flux qubits

    International Nuclear Information System (INIS)

    Chen Aimin; Cho Samyoung

    2011-01-01

    Conditional quantum oscillations are investigated for quantum gate operations in superconducting flux qubits. We present an effective Hamiltonian which describes a conditional quantum oscillation in two-qubit systems. Rabi-type quantum oscillations are discussed in implementing conditional quantum oscillations to quantum gate operations. Two conditional quantum oscillations depending on the states of control qubit can be synchronized to perform controlled-gate operations by varying system parameters. It is shown that the conditional quantum oscillations with their frequency synchronization make it possible to operate the controlled-NOT and -U gates with a very accurate gate performance rate in interacting qubit systems. Further, this scheme can be applicable to realize a controlled multi-qubit operation in various solid-state qubit systems. (author)

  12. Hermetically sealed superconducting magnet motor

    Science.gov (United States)

    DeVault, Robert C.; McConnell, Benjamin W.; Phillips, Benjamin A.

    1996-01-01

    A hermetically sealed superconducting magnet motor includes a rotor separated from a stator by either a radial gap, an axial gap, or a combined axial and radial gap. Dual conically shaped stators are used in one embodiment to levitate a disc-shaped rotor made of superconducting material within a conduit for moving cryogenic fluid. As the rotor is caused to rotate when the field stator is energized, the fluid is pumped through the conduit.

  13. Magnetic flux periodicities and finite momentum pairing in unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Loder, Florian

    2009-12-22

    This work contains a thorough study of the magnetic flux periodicity of loops of conventional and unconventional, especially d-wave, superconductors. Although already in 1961, several independent works showed that the flux period of a conventional superconducting loop is the superconducting flux quantum hc/2e, this question has never been investigated deeply for unconventional superconductors. And indeed, we show here that d-wave superconducting loops show a basic flux period of the normal flux quantum hc/e, a property originating from the nodal quasi-particle states. This doubling of the flux periodicity is best visible in the persistent current circulating in the loop, and it affects other properties of the superconductor such as the periodicity of d-wave Josephson junctions. In the second part of this work, the theory of electron pairing with finite center-of-mass momentum, necessary for the description of superconducting loops, is extended to systems in zero magnetic field. We show that even in the field free case, an unconventional pairing symmetry can lead to a superconducting ground state with finite-momentum electron pairs. Such a state has an inhomogeneous charge density and therefore is a basis for the description of coexistence of superconductivity and stripe order. (orig.)

  14. New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

    International Nuclear Information System (INIS)

    Kalbus, E.; Schmidt, C.; Bayer-Raich, M.; Leschik, S.; Reinstorf, F.; Balcke, G.U.; Schirmer, M.

    2007-01-01

    The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60 m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272 μg m -2 d -1 MCB and 71 μg m -2 d -1 DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream. - We provide a new methodology to quantify the potential contaminant mass flux from an aquifer to a stream

  15. Flux dynamics in ultrasensitive superconducting focal planes

    Data.gov (United States)

    National Aeronautics and Space Administration — The performance of superconducting focal planes will drive the achievable specifications of ultrasensitive instruments for NASA astrophysics missions, yet they have...

  16. Spontaneous fluxoid formation in superconducting loops

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Rivers, R.

    2009-01-01

    We report on the experimental verification of the Zurek-Kibble scenario in an isolated superconducting ring over a wide parameter range. The probability of creating a single flux quantum spontaneously during the fast normal-superconducting phase transition of a wide Nb loop clearly follows...

  17. Hydrogen pumping and release by graphite under high flux plasma bombardment

    International Nuclear Information System (INIS)

    Hirooka, Y.; Leung, W.K.; Conn, R.W.; Goebel, D.M.; LaBombard, B.; Nygren, R.; Wilson, K.L.

    1988-01-01

    Inert gas (helium or argon) plasma bombardment has been found to increase the surface gas adsorptivity of isotropic graphite (POCO-graphite), which can then getter residual gases in a high vacuum system. The inert gas plasma bombardment was carried out at a flux ≅ 1 x 10 18 ions s -1 cm -2 to a fluence of the order of 10 21 ions/cm 2 and at temperatures around 800 0 C. The gettering capability of graphite can be easily recovered by repeating inert gas plasma bombardment. The activated graphite surface exhibits a smooth, sponge-like morphology with significantly increased pore openings, which correlates with the observed increase in the surface gas adsorptivity. The activated graphite surface has been observed to pump hydrogen plasma particles as well. From calibrated H-alpha measurements, the dynamic hydrogen retention capacity is evaluated to be as large as 2 x 10 18 H/cm 2 at temperatures below 100 0 C and at a plasma bombarding energy of 300 eV. The graphite temperature was varied between 15 and 480 0 C. Due to the plasma particle pumping capability, hydrogen recycling from the activated graphite surface is significantly reduced, relative to that from a pre-saturated surface. A pre-saturated surface was also observed to reproducibly pump a hydrogen plasma to a concentration of 9.5 x 10 17 H/cm 2 . The hydrogen retention capacity of graphite is found to decrease with increasing temperature. A transient pumping mechanism associated with the sponge-like surface morphology is conjectured to explain the large hydrogen retention capacity. Hydrogen release behavior under helium and argon plasma bombardment was also investigated, and the result indicated the possibility of some in-pore retrapping effect. 43 refs., 11 figs

  18. The replacement of an electromagnetic primary sodium sampling pump in the Fast Flux Test Facility

    International Nuclear Information System (INIS)

    Grygiel, M.L.; McCargar, C.G.

    1985-01-01

    On November 16, 1984 a leak was discovered in one of the Fast Flux Test Facility (FFTF) Primary Sodium Sampling System electromagnetic pumps. The leak was discovered in the course of routine cell entry to investigate a shorted trace heat element. The purpose of this paper is to describe the circumstances surrounding the occurrence of the leak, the actions taken to replace the damaged pump and the additional steps which were necessary to return the plant to power. In addition, the processes involved in producing the leak are described briefly. The relative ease of recovery from this incident is indicative of the overall feasibility of the Liquid Metal Reactor (LMR) operational concept

  19. Induction motor for superconducting synchronous/asynchronous motor

    International Nuclear Information System (INIS)

    Litz, D.C.; Haller, H.E. III.

    1975-01-01

    An induction motor structure for use on the outside of a superconducting rotor comprising a cylindrical shell of solid and laminated, magnetic iron with squirrel cage windings embedded in the outer circumference of said shell is described. The sections of the shell between the superconducting windings of the rotor are solid magnetic iron. The sections of the shell over the superconducting windings are made of laminations of magnetic iron. These laminations are parallel to the axis of the machine and are divided in halves with the laminations in each half oriented in diagonal opposition so that the intersection of the laminations forms a V. This structure presents a relatively high reluctance to leakage flux from the superconducting windings in the synchronous operating mode, while presenting a low reluctance path to the stator flux during asynchronous operation

  20. Pumping Characteristics of the DIII-D Cryopump

    International Nuclear Information System (INIS)

    A.S. Bozek; C.B. Baxi; R.W. Callis; M.A. Mahdavi; R.C. O'Neill; E.E. Reis

    1999-01-01

    Beginning in 1992, the first of the DIII-D divertor baffles and cryocondensation pumps was installed. This open divertor configuration, located on the outermost floor of the DIII-D vessel, includes a cryopump with a predicted pumping speed of 50,000 ell/s excluding obstructions such as support hardware. Taking the pump structural and support characteristics into consideration, the corrected pumping speed for D 2 is 30,000 ell/s [1]. In 1996, the second divertor baffle and cryopump were installed. This closed divertor structure, located on the outermost ceiling of the DIII-D vessel, has a cryopump with a predicted pumping speed of 32,000 ell/s. In the fall of 1999, the third divertor baffle and cryopump will be installed. This divertor structure will be located on the 45 o angled corner on the innermost ceiling of the DIII-D vessel, known as the private flux region of the plasma configuration. With hardware supports factored into the pumping speed calculation, the private flux cryopump is expected to have a pumping speed of 15,000 ell/s. There was question regarding the effectiveness of the private flux cryopump due to the close proximity of the private flux baffle. This led to a conductance calculation study of the impact of rotating the cryopump aperture by 180 o to allow for greater particle and gas exhaust into the cryopump's helium panel. This study concluded that the cost and schedule impact of changing the private flux cryopump orientation and design did not warrant the possible 20% (3,000 ell/s) increase in pumping ability gained by rotating the cryopump aperture 180 o . The comparison of pumping speed of the first two cryocondensation pumps with the measured results will be presented as well as the calculation of the pumping speed for the private flux cryopump now being installed

  1. Experimental characterization of the flux-line lattice in superconducting V3Si

    International Nuclear Information System (INIS)

    Christen, D.K.; Kerchner, H.R.; Narayan, J.; Chang, Y.K.; Larson, B.C.; Sekula, S.T.

    1982-01-01

    Several microscopic properties of the flux-line lattice (FLL) in three separate single crystals of V 3 Si have been investigated by means of small-angle neutron diffraction. These low-field FLL characterizations have been correlated with the following material and superconducting properties: (1) the real crystal symmetry parallel to the applied magnetic field; (2) the micro-structure as determined by TEM; (3) magnetic irreversibilities in the mixed state; (4) reversible flux-line motion in ac response; and (5) martensitic structural transformation observed by x-ray diffraction. The three samples, V 3 Si-MP3, -MP4, and -MP5 possessed different defect structures, and this was manifested foremost in the FLL perfection. At low field (B 0 K, only MP3, which is free of second-phase precipitates, showed a highly resolved FLL. Sample MP5 contains a low density of small (200 A) coherent precipitates, and revealed well-defined FLL Bragg peaks for B greater than or equal to 0.5 T, but a highly mosaic, nearly polycrystalline FLL at lower fields. Sample MP4 contained large (500 to 1000 A) incoherent precipitates, and showed only a polycrystalline FLL at low field. In both MP3 and MP5, distinct anisotropic correlations were observed between the FLL morphology and the real-crystal direction along the applied field. The FLL perfection was strongly dependent on the growth history. The peak width history dependence for two different scattering geometries can be qualitatively modeled by proposed flux-pinning mechanisms. Quantitative comparisons with critical current measurements, however, are not totally reconcilable

  2. rf SQUID system as tunable flux qubit

    Energy Technology Data Exchange (ETDEWEB)

    Ruggiero, B. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy)]. E-mail: b.ruggiero@cib.na.cnr.it; Granata, C. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Vettoliere, A. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Rombetto, S. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Russo, R. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Russo, M. [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Corato, V. [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-81031 Aversa (Italy); Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy); Silvestrini, P. [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-81031 Aversa (Italy); Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Italy)

    2006-08-21

    We present a fully integrated rf SQUID-based system as flux qubit with a high control of the flux transfer function of the superconducting transformer modulating the coupling between the flux qubit and the readout system. The control of the system is possible by including into the superconducting flux transformer a vertical two-Josephson-junctions interferometer (VJI) in which the Josephson current is precisely modulated from a maximum to zero by a transversal magnetic field parallel to the flux transformer plane. The proposed system can be also used in a more general configuration to control the off-diagonal terms in the Hamiltonian of the flux qubit and to turn on and off the coupling between two or more qubits.

  3. Flux flow and flux creep in thick films of YBCO. [Y-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Rickets, J.; Vinen, W.F.; Abell, J.S.; Shields, T.C. (Superconductivity Research Group, Univ. of Birmingham (United Kingdom))

    1991-12-01

    The results are described of new experiments designed to study flux creep and flux flow along a single flux percolation path in thick films of YBCO. The flux flow regime is studied by a four-point resistive technique using pulsed currents, and the flux creep regime by observing the rate at which flux enters a superconducting loop in parallel with the resistance that is associated with the flux percolation path. (orig.).

  4. Critical current density, irreversibility line, and flux creep activation energy in silver-sheathed Bi2Sr2Ca2Cu3Ox superconducting tapes

    International Nuclear Information System (INIS)

    Shi, D.; Wang, Z.; Sengupta, S.; Smith, M.; Goodrich, L.F.; Dou, S.X.; Liu, H.K.; Guo, Y.C.

    1992-08-01

    Transport data, magnetic hysteresis and flux creep activation energy experimental results are presented for silver-sheathed high-T c Bi 2 Sr 2 Ca 2 Cu 3 O x superconducting tapes. The 110 K superconducting phase was formed by lead doping in a Bi-Sr-Ca-Cu-0 system. The transport critical current density was measured at 4.0 K to be 0.7 x 10 5 A/cm 2 (the corresponding critical current is 74 A) at zero field and 1.6 x 10 4 A/cm 2 at 12 T for H parallel ab. Excellent grain alignment in the a-b plane was achieved by a short-melting method, which considerably improved the critical current density and irreversibility line. Flux creep activation energy as a function of current is obtained based on the magnetic relaxation measurements

  5. Color superconductivity, ZN flux tubes and monopole confinement in deformed N=2* super Yang-Mills theories

    International Nuclear Information System (INIS)

    Kneipp, Marco A.C.

    2003-11-01

    We study the ZN flux tubes and monopole confinement in deformed N=2* super Yang-Mills theories. In order to do that we consider an N=4 super Yang-Mills theory with an arbitrary gauge group G and add some N=2, N=1 and N=0 deformation terms. We analyze some possible vacuum solutions and phases of the theory, depending on the deformation terms which are added. In the Coulomb phase for the N=2* theory, G is broken to U(1)r and the theory has monopole solutions. Then, by adding some deformation terms, the theory passes to the Higgs or color superconducting phase, in which G is broken to its center CG. In this phase we construct the ZN flux tubes Ansatz and obtain the BPS string tension. We show that the monopole magnetic fluxes are linear integer combinations of the string fluxes and therefore the monopoles can become confined. Then, we obtain a bound for the threshold length of the string-breaking. We also show the possible formation of a confining system with 3 different monopoles for the SU(3) gauge group. Finally we show that the BPS string tensions of the theory satisfy the Casimir scaling law. (author)

  6. Anisotrophic currents and flux jumps in high-Tc superconducting films with self-organized arrays of planar defects

    International Nuclear Information System (INIS)

    Yurchenko, V.V.; Qviller, A.J.; Mozhaev, P.B.; Mozhaeva, J.E.; Hansen, J.B.; Jacobsen, C.S.; Kotelyanskii, I.M.; Pan, A.V.; Johansen, T.H.

    2010-01-01

    Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa 2 Cu 3 O 7-δ (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO 3 substrates with different miscut angles θ. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different directions of the current flow we determine the anisotropy parameter of the in-plane current, as well as its field and temperature dependences. The artificially introduced defects also have a dramatic effect on the dynamics of the flux propagation: for 10 o o the magnetic flux propagates along the easy channels intermittently, i.e. in a form of flux jumps. This behavior is indicative of thermo-magnetic instability in superconductors, but we argue that this effect can be of a different nature.

  7. A study on metastable superconducting magnets

    International Nuclear Information System (INIS)

    Koyama, Kenichi

    1976-01-01

    It is important to construct superconducting magnets as cheap as possible. One of the methods to achieve such a purpose is to save the superconducting material and operate the magnets at a high current density. Therefore it is useful to investigate the requirements for the operation of metastable superconducting magnets which can work at a current higher than the recovery current. Using the theory of flux jump, we introduce a ''stable current'' below which no flux jump can occur. On a rough approximation, it is given by I sub(s) =√A P sub(i) H sub(e) T sub(o) f(x)/rho where A : cross-section of the composite conductor. P sub(i) : total perimeter of all the superconducting cores. h sub(e) : effective heat transfer coefficient to the liquid helium through the stabilizer. T sub(o) : a characteristic temperature of the superconducting cores. f(x) : a characteristic function for the relative core radius x. rho : effective resistivity of the composite. Then it is shown that superconducting magnets can operate without unexpected normal transitions in the region enclosed by the two curves of I sub(s) and I sub(c). Next, we discuss the characteristics of our saddle shaped superconducting magnet for an one-KW MHD generator. We found that, 1) the magnet does safely operate in the metastable state; 2) the characteristics of the magnet are consistent with our theoretical results. (auth.)

  8. Stability analysis of magnetic flux in thin-film superconductors

    International Nuclear Information System (INIS)

    Denisov, Dmitry

    2007-01-01

    This work presents theoretical results in the physics of superconductivity. The first part of the work is dedicated to the problem of thermomagnetic instabilities and flux avalanches in thin film superconductors. The second part describes the problem of flux trapped in the hole of the superconducting ring (author)

  9. Oscillations of the energy, magnetic moment, and current with a period equal to the normal or superconducting flux quantum in cyclic systems

    International Nuclear Information System (INIS)

    Svirskii, M.S.

    1985-01-01

    Oscillations with a period equal to the normal or superconducting flux quantum occur in the current density and the orbital parts of the energy and the magnetic moment in cyclic systems. Transitions between these regimes can be induced by changing the number of electrons or by switching between states with different energies

  10. Scientific Affairs Division of NATO Advanced Study Institute: abstracts for nonequilibrium superconductivity, phonons and Kapitza boundaries

    International Nuclear Information System (INIS)

    1980-05-01

    Abstracts of papers presented at the meeting are given. Topics covered include: Kapitza resistance; superconducting tunneling; energy gap enhancement in superconductors; instabilities in nonequilibrium superconducting states; exchange of charge between superconducting pairs and quasiparticles; motion of magnetic flux (flux flow); and other new phenomena

  11. Enhanced flux pinning properties in superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} films by a novel chemical doping approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.T., E-mail: wtwang@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y., E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)

    2013-10-15

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} (YBCO) films were prepared on (0 0 l) LaAlO{sub 3} substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T{sub c} spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping.

  12. Superconducting active impedance converter

    International Nuclear Information System (INIS)

    Ginley, D.S.; Hietala, V.M.; Martens, J.S.

    1993-01-01

    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

  13. Flux free growth of large FeSe1/2Te1/2 superconducting single crystals by an easy high temperature melt and slow cooling method

    Directory of Open Access Journals (Sweden)

    P. K. Maheshwari

    2015-09-01

    Full Text Available We report successful growth of flux free large single crystals of superconducting FeSe1/2Te1/2 with typical dimensions of up to few cm. The AC and DC magnetic measurements revealed the superconducting transition temperature (Tc value of around 11.5K and the isothermal MH showed typical type-II superconducting behavior. The lower critical field (Hc1 being estimated by measuring the low field isothermal magnetization in superconducting regime is found to be above 200Oe at 0K. The temperature dependent electrical resistivity ρ(T  showed the Tc (onset to be 14K and the Tc(ρ = 0 at 11.5K. The electrical resistivity under various magnetic fields i.e., ρ(TH for H//ab and H//c demonstrated the difference in the width of Tc with applied field of 14Tesla to be nearly 2K, confirming the anisotropic nature of superconductivity. The upper critical and irreversibility fields at absolute zero temperature i.e., Hc2(0 and Hirr(0 being determined by the conventional one-band Werthamer–Helfand–Hohenberg (WHH equation for the criteria of normal state resistivity (ρn falling to 90% (onset, and 10% (offset is 76.9Tesla, and 37.45Tesla respectively, for H//c and 135.4Tesla, and 71.41Tesla respectively, for H//ab. The coherence length at the zero temperature is estimated to be above 20Å ´ by using the Ginsburg-Landau theory. The activation energy for the FeSe1/2Te1/2 in both directions H//c and H//ab is determined by using Thermally Activation Flux Flow (TAFF model.

  14. A superconducting microcalorimeter for low-flux detection of near-infrared single photons

    Energy Technology Data Exchange (ETDEWEB)

    Dreyling-Eschweiler, Jan

    2014-07-15

    This thesis covers the development and the characterization of a single photon detector based on a superconducting microcalorimeter. The detector development is motivated by the Any Light Particle Search II (ALPS II) experiment at DESY in Hamburg, which searches for weakly interacting sub-eV particles (WISPs). Therefore, a detection of low-fluxes of 1064 nm light is required. The work is divided in three analyses: the characterization of a milli-kelvin (mK) cryostat, the characterization of superconducting sensors for single photon detection, and the determination of dark count rates concerning 1064 nm signals. Firstly, an adiabatic demagnetization refrigerator (ADR) is characterized, which allows to reach mK-temperatures. During commissioning, the ADR cryostat is optimized and prepared to stably cool superconducting sensors at 80 mK±25 μK. It is found that sensors can be continuously operated for ∝20 h before recharging the system in <2 h. Furthermore, the adiabatic system reaches a chance of success of ∝80 % for a recharge without technical problems. Secondly, superconducting sensors are analyzed. The focus is on microcalorimetric transition-edge sensors (TESs) based on 20 nm Tungsten (W) films fabricated by the U.S. National Institute of Standards and Technology (NIST). NIST TESs have a near unity detection efficiency for 1064 nm light (literature value). The energy resolution for 1064 nm signals is measured to be <8 %. The exponential falling time of a photon pulse is 1.5 μs. Furthermore, by determining TES parameters, it is found that the linear TES theory describes measured photon pulses well. The TES response is read out by a superconducting quantum interference device (SQUID) fabricated by Physikalisch-Technische Bundesanstalt (PTB). The system bandwidth is measured to be 0.9 MHz. Finally, the operation in the ADR cryostat as well as the ALPS II laboratory is optimized. This setup forms the ALPS TES detector. Thirdly, the background is measured to

  15. Design considerations for superconducting magnets as a maglev pad

    International Nuclear Information System (INIS)

    Ichikawa, H.; Ogiwara, H.

    1974-01-01

    The design and construction of a thin superconducting magnet for a magnetically suspended high-speed train are explained. The superconducting magnet, which is to be used in a null-flux maglev train system, is called a 'wing-type' superconducting magnet because of its geometry. The wing-type superconducting magnet is about 1.5m long and weighs about 500kg, but its heat loss is within 1W, which is very small compared with that of conventional superconducting magnets. (author)

  16. Flux pinning characteristics in cylindrical niobium samples used for superconducting radio frequency cavity fabrication

    Science.gov (United States)

    Dhavale, Asavari S.; Dhakal, Pashupati; Polyanskii, Anatolii A.; Ciovati, Gianluigi

    2012-06-01

    We present the results from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low-temperature baking as they are typically applied to SRF cavities. The magnetization data are analyzed using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples, favorable to lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  17. Development of superconducting magnetic bearing using superconducting coil and bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Seino, H; Nagashima, K; Arai, Y [Railway Technical Research Institute, Hikari-cho 2-8-38, Kokubunji-shi, Tokyo (Japan)], E-mail: seino@rtri.or.jp

    2008-02-01

    The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated.

  18. Development of superconducting magnetic bearing using superconducting coil and bulk superconductor

    International Nuclear Information System (INIS)

    Seino, H; Nagashima, K; Arai, Y

    2008-01-01

    The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated

  19. Experimental formation of a fractional vortex in a superconducting bi-layer

    Science.gov (United States)

    Tanaka, Y.; Yamamori, H.; Yanagisawa, T.; Nishio, T.; Arisawa, S.

    2018-05-01

    We report the experimental formation of a fractional vortex generated by using a thin superconducting bi-layer in the form of a niobium bi-layer, observed as a magnetic flux distribution image taken by a scanning superconducting quantum interference device (SQUID) microscope. Thus, we demonstrated that multi-component superconductivity can be realized by an s-wave conventional superconductor, because, in these superconductors, the magnetic flux is no longer quantized as it is destroyed by the existence of an inter-component phase soliton (i-soliton).

  20. Entangled Coherent States Generation in two Superconducting LC Circuits

    International Nuclear Information System (INIS)

    Chen Meiyu; Zhang Weimin

    2008-01-01

    We proposed a novel pure electronic (solid state) device consisting of two superconducting LC circuits coupled to a superconducting flux qubit. The entangled coherent states of the two LC modes is generated through the measurement of the flux qubit states. The interaction of the flux qubit and two LC circuits is controlled by the external microwave control lines. The geometrical structure of the LC circuits is adjustable and makes a strong coupling between them achievable. This entangled coherent state generator can be realized by using the conventional microelectronic fabrication techniques which increases the feasibility of the experiment.

  1. High temperature superconductive flux gate magnetometer

    International Nuclear Information System (INIS)

    Gershenson, M.

    1991-01-01

    This paper proposes a different type of HTS superconducting magnetometer based on the non-linear magnetic behavior of bulk HTS materials. The device design is based on the generation of second harmonics which arise as a result of non-linear magnetization observed in Type-II superconductors. Even harmonics are generated from the non-linear interaction of an ac excitation signal with an external DC magnetic field which acts as a bias signal

  2. Flux penetration in a superconducting alloy with spatial by modulated concentration

    International Nuclear Information System (INIS)

    Dobrosavljevic, L.; Centre National de la Recherche Scientifique, 38 - Grenoble

    1976-01-01

    The flux penetration in inhomogeneous superconductors with periodic structure is studied. Superconducting alloys with the impurity concentration varying periodically in one direction are considered. In a London model the magnetic structure of a single vortex, the change of its self-energy and of the interaction between two vortices due to the concentration modulation are studied. The matching between the vortex lattice and the periodic modulation of the concentration are also studied: at some definite values of the external field, H=Hsub(n1,n2), the vortices are arranged in a triangular lattice in such a way that all the vortices lie in the high concentration regions. The projection of the sides of the triangles on the modulation direction is then a multiple of the modulation period L 0 . At H=Hsub(n1,n2) the Gibbs' free energy of the system is lowered and a pinning vortices takes place. The possibility of such a matching effect in the low field region (H> approximately Hsub(1)) and in the intermediate field region (Hsub(c1) [fr

  3. Earlier and recent aspects of superconductivity

    International Nuclear Information System (INIS)

    Bednorz, J.G.; Muller, K.A.

    1990-01-01

    Contemporary knowledge of superconductivity is set against its historical background in this book. First, the highlights of superconductivity research in the twentieth century are reviewed. Further contributions then describe the basic phenomena resulting from the macroscopic quantum state of superconductivity (such as zero resistivity, the Meissner-Ochsenfeld effect, and flux quantization) and review possible mechanisms, including the classical BCS theory and the more recent alternative theories. The main categories of superconductors - elements, intermetallic phases, chalcogenides, oxides and organic compounds - are described. Common features and differences in their structure and electronic properties are pointed out. This overview of superconductivity is completed by a discussion of properties related to the coherence length

  4. A strict experimental test of macroscopic realism in a superconducting flux qubit.

    Science.gov (United States)

    Knee, George C; Kakuyanagi, Kosuke; Yeh, Mao-Chuang; Matsuzaki, Yuichiro; Toida, Hiraku; Yamaguchi, Hiroshi; Saito, Shiro; Leggett, Anthony J; Munro, William J

    2016-11-04

    Macroscopic realism is the name for a class of modifications to quantum theory that allow macroscopic objects to be described in a measurement-independent manner, while largely preserving a fully quantum mechanical description of the microscopic world. Objective collapse theories are examples which aim to solve the quantum measurement problem through modified dynamical laws. Whether such theories describe nature, however, is not known. Here we describe and implement an experimental protocol capable of constraining theories of this class, that is more noise tolerant and conceptually transparent than the original Leggett-Garg test. We implement the protocol in a superconducting flux qubit, and rule out (by ∼84 s.d.) those theories which would deny coherent superpositions of 170 nA currents over a ∼10 ns timescale. Further, we address the 'clumsiness loophole' by determining classical disturbance with control experiments. Our results constitute strong evidence for the superposition of states of nontrivial macroscopic distinctness.

  5. Device for investigation of magnetic flux jumps in ribbon superconductors

    International Nuclear Information System (INIS)

    Andrianov, A.V.; Bashkirov, Yu.A.; Kremlev, M.G.

    1986-01-01

    A device for simulation of magnetic flux jumps in superconductors of conducting magnet sandwich-type windings super-applyed of a ribbon conductor is described. A superconducting magnet with a measuring cassetter are the main elements of the device. An external magnetic field is generated by a two-sectional superconducting magnet permitting to simulate the shape of the magnetic field characteristic for sandwich-type windings. Maximum radial component of the magnetic field is 2 T. Jumps of the magnetic flux are recorded by induction transducers and the magnetic field-by Hall trasducer. The effect of coating of standard metal on magnetic flux jumps in Nb 3 Sn base superconducting ribbon is considered

  6. Fraunhofer regime of operation for superconducting quantum interference filters

    DEFF Research Database (Denmark)

    Shadrin, A.V.; Constantinian, K.Y.; Ovsyannikov, G.A.

    2008-01-01

    Series arrays of superconducting quantum interference devices (SQUIDs) with incommensurate loop areas, so-called superconducting quantum interference filters (SQIFs), are investigated in the kilohertz and the gigahertz frequency range. In SQIFs made of high-T-c bicrystal junctions the flux...... range of more than 60 dB in the kilohertz range. In the 1-2 GHz range the estimated power gain is 20 dB and the magnetic flux noise level is as low as 10(-4)Phi(0)....

  7. Spatially resolved charge exchange flux calculations on the Toroidal Pumped Limiter of Tore Supra

    International Nuclear Information System (INIS)

    Marandet, Y.; Tsitrone, E.; Boerner, P.; Reiter, D.; Beaute, A.; Delchambre, E.; Escarguel, A.; Brezinsek, S.; Genesio, P.; Gunn, J.; Monier-Garbet, P.; Mitteau, R.; Pegourie, B.

    2009-01-01

    A spatially resolved calculation of the charge exchange particle and energy fluxes on the Toroidal Pumped Limiter (TPL) of Tore Supra is presented, as a first step towards a better understanding and modelling of carbon erosion, migration, as well as deuterium codeposition and bulk diffusion of deuterium in Tore Supra. The results are obtained with the EIRENE code run in a 3D geometry. Physical and chemical erosion maps on the TPL are calculated, and the contribution of neutrals to erosion, especially in the self-shadowed area, is calculated.

  8. Vacuum Technology for Superconducting Devices

    Energy Technology Data Exchange (ETDEWEB)

    Chiggiato, P [European Organization for Nuclear Research, Geneva (Switzerland)

    2014-07-01

    The basic notions of vacuum technology for superconducting applications are presented, with an emphasis on mass and heat transport in free molecular regimes. The working principles and practical details of turbomolecular pumps and cryopumps are introduced. The specific case of the Large Hadron Collider’s cryogenic vacuum system is briefly reviewed.

  9. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Dhavale Ashavai, Pashupati Dhakal, Anatolii A Polyanskii, Gianluigi Ciovati

    2012-04-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples which implies a lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  10. Flux pinning characteristics in cylindrical niobium samples used for superconducting radio frequency cavity fabrication

    International Nuclear Information System (INIS)

    Dhavale, Asavari S; Dhakal, Pashupati; Ciovati, Gianluigi; Polyanskii, Anatolii A

    2012-01-01

    We present the results from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low-temperature baking as they are typically applied to SRF cavities. The magnetization data are analyzed using a modified critical state model. The critical current density J c and pinning force F p are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples, favorable to lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities. (paper)

  11. Magnetic flux density distribution in superconducting cylinders of arbitrary cross section subjected to an axial magnetic field

    Science.gov (United States)

    Fournet, G.

    1982-07-01

    We show here how the application of the critical state model allows one to determine the magnetic flux density B⃗ in each point of a superconducting cylinder with an arbitrary cross section subjected to axial magnetic fields Hz; the B = 0 boundaries of the regions occupied by the vortices are so defined. We successively consider the cases where the critical current density Jc is either isotropic (constant or an arbitrary function of B) or tensorial, which means, for our problem, the use of two components Jcx and Jcy (either constant or depending on B but Jcx/Jcy remaining constant).

  12. A novel approach to calculate inductance and analyze magnetic flux density of helical toroidal coil applicable to Superconducting Magnetic Energy Storage systems (SMES)

    International Nuclear Information System (INIS)

    Alizadeh Pahlavani, M.R.; Shoulaie, A.

    2010-01-01

    In this paper, formulas are proposed for the self and mutual inductance calculations of the helical toroidal coil (HTC) by the direct and indirect methods at superconductivity conditions. The direct method is based on the Neumann's equation and the indirect approach is based on the toroidal and the poloidal components of the magnetic flux density. Numerical calculations show that the direct method is more accurate than the indirect approach at the expense of its longer computational time. Implementation of some engineering assumptions in the indirect method is shown to reduce the computational time without loss of accuracy. Comparison between the experimental measurements and simulated results for inductance, using the direct and the indirect methods indicates that the proposed formulas have high reliability. It is also shown that the self inductance and the mutual inductance could be calculated in the same way, provided that the radius of curvature is >0.4 of the minor radius, and that the definition of the geometric mean radius in the superconductivity conditions is used. Plotting contours for the magnetic flux density and the inductance show that the inductance formulas of helical toroidal coil could be used as the basis for coil optimal design. Optimization target functions such as maximization of the ratio of stored magnetic energy with respect to the volume of the toroid or the conductor's mass, the elimination or the balance of stress in some coordinate directions, and the attenuation of leakage flux could be considered. The finite element (FE) approach is employed to present an algorithm to study the three-dimensional leakage flux distribution pattern of the coil and to draw the magnetic flux density lines of the HTC. The presented algorithm, due to its simplicity in analysis and ease of implementation of the non-symmetrical and three-dimensional objects, is advantageous to the commercial software such as ANSYS, MAXWELL, and FLUX. Finally, using the

  13. Nano-electro-mechanical pump: Giant pumping of water in carbon nanotubes

    Science.gov (United States)

    Farimani, Amir Barati; Heiranian, Mohammad; Aluru, Narayana R.

    2016-05-01

    A fully controllable nano-electro-mechanical device that can pump fluids at nanoscale is proposed. Using molecular dynamics simulations, we show that an applied electric field to an ion@C60 inside a water-filled carbon nanotube can pump water with excellent efficiency. The key physical mechanism governing the fluid pumping is the conversion of electrical energy into hydrodynamic flow with efficiencies as high as 64%. Our results show that water can be compressed up to 7% higher than its bulk value by applying electric fields. High flux of water (up to 13,000 molecules/ns) is obtained by the electro-mechanical, piston-cylinder-like moving mechanism of the ion@C60 in the CNT. This large flux results from the piston-like mechanism, compressibility of water (increase in density of water due to molecular ordering), orienting dipole along the electric field and efficient electrical to mechanical energy conversion. Our findings can pave the way towards efficient energy conversion, pumping of fluids at nanoscale, and drug delivery.

  14. Anisotrophic currents and flux jumps in high-T{sub c} superconducting films with self-organized arrays of planar defects

    Energy Technology Data Exchange (ETDEWEB)

    Yurchenko, V.V., E-mail: vitaliy.yurchenko@fys.uio.n [Department of Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo (Norway); Qviller, A.J. [Department of Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo (Norway); Mozhaev, P.B.; Mozhaeva, J.E. [Department of Physics, Technical University of Denmark, Kgs. Lyngby DK-2800 (Denmark); Institute of Physics and Technology RAS, Moscow 117218 (Russian Federation); Hansen, J.B.; Jacobsen, C.S. [Department of Physics, Technical University of Denmark, Kgs. Lyngby DK-2800 (Denmark); Kotelyanskii, I.M. [Institute of Radio Engineering and Electronics RAS, Fryazino, 141190 Moscow District (Russian Federation); Pan, A.V. [Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong 2522 (Australia); Johansen, T.H. [Department of Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo (Norway)

    2010-10-01

    Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}(YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO{sub 3} substrates with different miscut angles {theta}. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different directions of the current flow we determine the anisotropy parameter of the in-plane current, as well as its field and temperature dependences. The artificially introduced defects also have a dramatic effect on the dynamics of the flux propagation: for 10{sup o}<{theta}<14{sup o} the magnetic flux propagates along the easy channels intermittently, i.e. in a form of flux jumps. This behavior is indicative of thermo-magnetic instability in superconductors, but we argue that this effect can be of a different nature.

  15. Survey of potential applications of superconducting suspensions

    International Nuclear Information System (INIS)

    Rao, D.K.; Bupara, S.S.

    1993-01-01

    The purpose of this report is to survey the recent developments in applying the bulk superconductors to mechanical applications. These applications, called superconducting suspensions, can be broadly divided into three groups - Passive Magnetic Bearings, Passive Superconducting Dampers and Active Superconducting Bearings. Basically, passive magnetic bearings utilize bulk superconductors to support a rotating shaft without contact while active superconducting bearings employ superconducting wires. Passive superconducting dampers, on the other hand, dissipate energy from a vibrating component. Over the past one year, dramatic improvements have been made in processing large-size specimens made of high grade bulk superconductors. As a result, they can meet the size requirements and load capacity requirements of many applications. With this size-scale up, one can utilize them in a wider number of applications than what was possible a few years back. At present several organizations have demonstrated the capability of passive magnetic bearings. The targeted applications include miniature cryoturboexpanders, cryoturbopumps, energy storage wheels and turbomolecular pumps. These demonstrations indicate that the passive magnetic bearings are closer to technology maturity. (orig.)

  16. Quantum Theory of Conducting Matter Superconductivity and Quantum Hall Effect

    CERN Document Server

    Fujita, Shigeji; Godoy, Salvador

    2009-01-01

    Explains major superconducting properties including zero resistance, Meissner effect, sharp phase change, flux quantization, excitation energy gap, and Josephson effects using quantum statistical mechanical calculations. This book covers the 2D superconductivity and the quantum Hall effects

  17. Cotransporters as molecular water pumps

    DEFF Research Database (Denmark)

    Zeuthen, Thomas; MacAulay, Nanna

    2002-01-01

    Molecular water pumps are membrane proteins of the cotransport type in which a flux of water is coupled to substrate fluxes by a mechanism within the protein. Free energy can be exchanged between the fluxes. Accordingly, the flux of water may be relatively independent of the external water chemical...

  18. The Study about Application of Transportation System of the Superconductive Electromagnetism Propulsion in the Harbor

    OpenAIRE

    涌井, 和也; 荻原, 宏康

    1999-01-01

    Electromagnetic propulsion is promising technique for a linear motor car, a ship and a space ship, in future. W. A Rice developed an electromagnetic pump for the liquid metal transfer. There are two electromagnetic propulsions : a superconductive electricity propulsion and a superconductive electromagnetic propulsion. A superconductive electricity propulsion ship uses a screw driven by a superconducting motor. This technique has merits of excellent navigation-ability, and the free degree of t...

  19. Sweeping a persisting superconducting magnet with a transformer

    International Nuclear Information System (INIS)

    Spencer, G.F.; Alexander, P.W.; Ihas, G.G.

    1982-01-01

    A method for sweeping a persisting superconducting magnet is described. The field sweep is achieved by including in the superconducting loop of the magnet a coil which acts as the secondary coil of a transformer. Variation of the current in the primary coil of the transformer, controlled from outside the cryostat, causes the field-sweeping action through flux-linking with the superconducting loop. Compared to directly changing the current in a magnet, this technique improves control by the ratio of the magnet's inductance to the transformer's inductance. The advantages of using an all-metal vacuum-tight superconducting feedthrough are discussed. (author)

  20. Method and Apparatus of Implementing a Magnetic Shield Flux Sweeper

    Science.gov (United States)

    Sadleir, John E. (Inventor)

    2018-01-01

    The present invention relates to a method and apparatus of protecting magnetically sensitive devices with a shield, including: a non-superconducting metal or lower transition temperature (T.sub.c) material compared to a higher transition temperature material, disposed in a magnetic field; means for creating a spatially varying order parameter's |.PSI.(r,T)|.sup.2 in a non-superconducting metal or a lower transition temperature material; wherein a spatially varying order parameter is created by a proximity effect, such that the non-superconducting metal or the lower transition temperature material becomes superconductive as a temperature is lowered, creating a flux-free Meissner state at a center thereof, in order to sweep magnetic flux lines to the periphery.

  1. Flux pinning and superconducting properties of ZnO added (Nd, Eu, Gd)Ba.sub.2./sub. Cu.sub.3./sub. O.sub.y./sub..

    Czech Academy of Sciences Publication Activity Database

    Muralidhar, M.; Sakai, N.; Jirsa, Miloš; Kono, T.; Murakami, M.; Hirabayashi, I.

    445-448, - (2006), s. 403-407 ISSN 0921-4534. [International Symposium on Superconductivity /18./. Tsukuba, 24.10.2005-26.10.2005] Institutional research plan: CEZ:AV0Z10100520 Keywords : microstructure * MgO seeds * critical current density * flux pinning * LRE-123 melt textured compounds Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.792, year: 2006

  2. Test of superconducting radio-frequency cavity bombarded by protons

    Science.gov (United States)

    O'Donnell, J. M.; McCloud, B. J.; Morris, C. L.; McClelland, J. B.; Rusnak, B.; Thiessen, H. A.; Langenbrunner, J. L.

    1992-05-01

    A beam of 2 × 10 10 protons/s was focused onto a small area on the high-field iris of a superconducting cavity operating at the resonance frequency. The input, reflected, and stored power were monitored. The cavity remained in steady state during this test. We conclude that such superconducting cavities will remain viable in the high-proton-flux environments proposed in the design of a superconducting accelerator for pions (PILAC).

  3. Test of superconducting radio-frequency cavity bombarded by protons

    Energy Technology Data Exchange (ETDEWEB)

    O' Donnell, J.M.; McCloud, B.J.; Morris, C.L.; McClelland, J.B.; Rusnak, B.; Thiessen, H.A. (Los Alamos National Lab., NM (United States)); Langenbrunner, J.L. (Dept. of Physics and Astronomy, Univ. Minnesota, Minneapolis, MN (United States))

    1992-05-10

    A beam of 2x10{sup 10} protons/s was focused onto a small area on the high-field iris of a superconducting cavity operating at the resonance frequency. The input, reflected, and stored power were monitored. The cavity remained in steady state during this test. We conclude that such superconducting cavities will remain viable in the high-proton-flux environments proposed in the design of a superconducting accelerator for pions (PILAC). (orig.).

  4. Dynamoelectric machine with a superconductive field winding that can operate in either a synchronous or an asynchronous mode

    International Nuclear Information System (INIS)

    Mole, C.J.; Haller, H.E. III.

    1977-01-01

    Two parallel magnetic flux paths are provided in a dynamoelectric machine having a superconductive field winding. A first, or main, magnetic flux path includes at least one area of nonferromagnetic or diamagnetic material. A second, or shunt, magnetic flux path prevents the relatively low frequency ac flux present during starting or asynchronous operation of the machine, when used as an ac motor, from penetrating the superconductive winding

  5. Gambling with Superconducting Fluctuations

    Science.gov (United States)

    Foltyn, Marek; Zgirski, Maciej

    2015-08-01

    Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.

  6. Method for obtaining large levitation pressure in superconducting magnetic bearings

    Science.gov (United States)

    Hull, John R.

    1996-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  7. ALT-I pump limiter experiments

    International Nuclear Information System (INIS)

    Goebel, D.M.; Conn, R.W.; Campbell, G.A.

    1987-09-01

    Results from the ALT-I pump limiter experiments in TEXTOR are presented. ALT-I has demonstrated control of the plasma density in a high recycling tokamak by pumping up to 15% of the core efflux. The closed pump limiter designs with restricted entrance geometries to reduce the backflow of neutral gas to the plasma remove over 50% of the ion flux incident on the collection slot. Up to 80% of the entrance ion flux is removed when the edge electron temperature is less than 10 eV and plasma-neutral gas interactions are minimized inside the limiter. Results from a 3-D Monte Carlo neutral gas transport code agree closely with these experimental results. The compound curvature of the head is found to distribute the heat over the surface as predicted in the original designs. Impurity removal experiments demonstrate that significant helium exhaust can be achieved with a pump limiter. During ohmic heating in TEXTOR, the energy and particle confinement times are proportional to the line averaged core density. With ICRH auxiliary heating, tau/sub E/ follow L-mode scaling independent of particle removal by the pump limiter. Pump limiter operation does not directly modify the SOL plasma density and electron temperature, but controls the core plasma density by changing the global recycling at the boundary. The global particle confinement, the particle flux to the limiter, and the edge electron temperature follow the changes in the core density and auxiliary heating power. 25 refs

  8. Modern aspects of Josephson dynamics and superconductivity electronics

    CERN Document Server

    Askerzade, Iman; Cantürk, Mehmet

    2017-01-01

    In this book new experimental investigations of properties of Josephson junctions and systems are explored with the help of recent developments in superconductivity. The theory of the Josephson effect is presented taking into account the influence of multiband and anisotropy effects in new superconducting compounds. Anharmonicity effects in current-phase relation on Josephson junctions dynamics are discussed. Recent studies in analogue and digital superconductivity electronics are presented. Topics of special interest include resistive single flux quantum logic in digital electronics. Application of Josephson junctions in quantum computing as superconducting quantum bits are analyzed. Particular attention is given to understanding chaotic behaviour of Josephson junctions and systems. The book is written for graduate students and researchers in the field of applied superconductivity.

  9. Construction and testing of a double acting bellows liquid helium pump

    International Nuclear Information System (INIS)

    Burns, W.A.; Green, M.A.; Ross, R.R.; Van Slyke, H.

    1980-05-01

    The double acting reciprocating bellows liquid helium pump built and tested at the Lawrence Berkeley Laboratory is described. The pump is capable of delivering 50 gs -1 of liquid helium to supply the two-phase cooling sytem for a large superconducting magnet. The pump is driven by a torque motor at room temperature; the reciprocating motion is transmitted to the pump through a shaft which operates between room temperature and 4 0 K. The design details of this liquid helium pump are presented. The helium pump has operated in a helium bath and in pumped forced flow helium circuits. The results of these experimental tests are presented in this report

  10. Electromagnetic pumping of liquid lithium in inertial confinement fusion reactors

    International Nuclear Information System (INIS)

    Baker, R.S.; Blink, J.A.; Tessier, M.J.

    1983-01-01

    The basic operating principles and geometries of ten electromagnetic pumps are described. Two candidate pumps, the annular-linear-induction pump and the helical-rotor electromagnetic pump, are compared for possible use in a full-scale liquid-lithium inertial confinement fusion reactor. A parametric design study completed for the helical-rotor pump is shown to be valid when applied to an experimental sodium pump. Based upon the preliminary HYLIFE requirements for a lithium flow rate per pump of 8.08 m 3 /s at a head of 82.5 kPa, a complete set of 70 variables are specified for a helical-rotor pump with either a normally conducting or a superconducting winding. The two alternative designs are expected to perform with efficiencies of 50 and 60%, respectively

  11. Flux Dynamics and Time Effects in a Carved out Superconducting Polycrystalline Bi-Sr-Ca-Cu-O Sample

    Energy Technology Data Exchange (ETDEWEB)

    Olutas, M [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey); Yetis, H [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey); Altinkok, A [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey); Soezeri, H [National Metrology Institute TUBITAK PO Box 21, 41470, Gebze-Kocaeli (Turkey); Kilic, K [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey); Kilic, A [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey); Cetin, O [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory 14280 Bolu (Turkey)

    2006-06-01

    Systematic slow transport relaxation (V-t curves) and magnetovoltage measurements (V-H curves) have been carried out in a carved out superconducting polycrystalline Bi-Sr-Ca-Cu-O sample as a function of current (I), temperature (T), and external field (H). The V-t curves reveal the details of the time evolution of the penetrated state within the granular structure of the sample and also give a direct evidence of the relaxation of the flux trapped inside the drilled hole on the time scale of the experiment. On the other hand, V-H curves exhibit several unusual interesting properties upon cycling of the external magnetic field in forward and reverse directions, and, in addition to irreversibilities, strong reversible effects are observed, which is associated with the trapping of the macroscopic flux bundles in the drilled hole. It is also observed that the field sweep rate influences dramatically the reversible and irreversible behavior of V-H curves. The experimental results were mainly interpreted in terms of current and field induced organization of the vortices.

  12. Flux Dynamics and Time Effects in a Carved out Superconducting Polycrystalline Bi-Sr-Ca-Cu-O Sample

    International Nuclear Information System (INIS)

    Olutas, M; Yetis, H; Altinkok, A; Soezeri, H; Kilic, K; Kilic, A; Cetin, O

    2006-01-01

    Systematic slow transport relaxation (V-t curves) and magnetovoltage measurements (V-H curves) have been carried out in a carved out superconducting polycrystalline Bi-Sr-Ca-Cu-O sample as a function of current (I), temperature (T), and external field (H). The V-t curves reveal the details of the time evolution of the penetrated state within the granular structure of the sample and also give a direct evidence of the relaxation of the flux trapped inside the drilled hole on the time scale of the experiment. On the other hand, V-H curves exhibit several unusual interesting properties upon cycling of the external magnetic field in forward and reverse directions, and, in addition to irreversibilities, strong reversible effects are observed, which is associated with the trapping of the macroscopic flux bundles in the drilled hole. It is also observed that the field sweep rate influences dramatically the reversible and irreversible behavior of V-H curves. The experimental results were mainly interpreted in terms of current and field induced organization of the vortices

  13. The study of superconducting order parameter dynamics

    International Nuclear Information System (INIS)

    Goldman, A.M.

    1988-01-01

    Flux quantization experiments have demonstrated the importance of long range phase coherence in the description of the superconducting state, an idea originally proposed as an integral part of the phenomenological theory of the Meissner-Ochsenfeld effect. The most striking experimental demonstration of the phase coherence of the superconducting state is that the maximum dc Josephson current in a thin-film tunneling junction exhibits a Fraunhofer-like dependence on magnetic field

  14. Critical field measurements in a superconducting networks

    International Nuclear Information System (INIS)

    Pannetier, B.; Chaussy, J.; Rammal, R.

    1984-01-01

    We have measured the critical field of a periodic two-dimensional network of superconducting indium. At low fields, the critical line Hsub(c)(T) reflects the network topology and exhibits well-defined cusps due to flux quantization corresponding to both integer and rational number of flux quanta phi 0 = h/2e per unit loop of the network [fr

  15. Search for a flux of cosmic-ray magnetic monopoles with an eight-channel superconducting detector

    International Nuclear Information System (INIS)

    Huber, M.E.; Cabrera, B.; Taber, M.A.; Gardner, R.D.

    1991-01-01

    A superconducting detector for cosmic-ray magnetic monopoles originally designed with a cross section of 1.5 m 2 (averaged over 4π solid angle) for double-coincident events was active from 5 May 1987 to 5 August 1988. The detector consists of eight independent inductive gradiometers located on the surface of an octagonal prism. The conductor is niobium-titanium foil and the current sensors are rf SQUID's. The signal-to-noise ratio for a single Dirac charge is greater than 50 in a 0.05-Hz bandwidth, and low-noise data was obtained over 547 days of continuous cryogenic operation. Of this time, we obtained ∼50% live time. Open circuits in portions of two gradiometers and occasional coupling of disturbances in adjacent gradiometers reduce the active sensing area to 1.1 m 2 . A closed-cycle helium liquefier eliminates helium transfers and increases the stability of the data. Anticoincidence instrumentation includes strain gauges, a flux-gate magnetometer, an ultrasonic motion detector, and a wideband rms rf voltmeter. The exposure to date represents a limit on the flux of cosmic-ray magnetic monopoles of 7.2x10 -13 cm -2 s -1 sr -1 at a 90% confidence level, eliminating most of the phase space for monopole plasma oscillation theories

  16. Performance of miniature electromagnetic pump at liquid nitrogen temperature; Kogata deji ponpu no ekitai chiso ondo ni okeru seino

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, K.; Herai, T. [Railway Technical Research Inst., Tokyo (Japan)

    1999-11-10

    Though it cools the radiant heat shield board of superconducting magnet for levitation system railway by the liquid nitrogen, the piping on the shield board must be made to circulate the refrigerant in order to maintain the large area, which covers superconducting coil at the uniform temperature. Though as a circulating pump, it had developed thermal pumps using the heater and systems using natural circulation, etc. until now, it examined circulation performance of liquid nitrogen using the electromagnetic pump that here, it was small, and that to do the operation is sure. (NEDO)

  17. Numerical simulation of the self-pumped long Josephson junction using a modified sine-Gordon model

    International Nuclear Information System (INIS)

    Sobolev, A.S.; Pankratov, A.L.; Mygind, J.

    2006-01-01

    We have numerically investigated the dynamics of a long Josephson junction (flux-flow oscillator) biased by a DC current in the presence of magnetic field. The study is performed in the frame of the modified sine-Gordon model, which includes the surface losses, RC-load at both FFO ends and the self-pumping effect. In our model the dumping parameter depends both on the spatial coordinate and the amplitude of the AC voltage. In order to find the DC FFO voltage the damping parameter has to be calculated by successive approximations and time integration of the perturbed sine-Gordon equation. The modified model, which accounts for the presence of the superconducting gap, gives better qualitative agreement with experimental results compare to the conventional sine-Gordon model

  18. Prospects for obtaining a superconducting filter to purify oxygen from argon

    International Nuclear Information System (INIS)

    Sawai, Yuichi; Ishizaki, Kozo; Yayashi, Shigeki; Jain, R.

    1993-01-01

    A possible superconducting filter, through which argon can pass and oxygen can not pass, is discussed theoretically. Oxygen and argon are paramagnetic and diamagnetic materials, respectively. The mixture of oxygen and argon can be separated in a magnetic field higher than 4 T 2 /m of BdB/dx, where B is the magnetic flux density and dB/dx is its gradient. Such a magnetic field can be obtained by a superconducting filter. Because magnetic flux does not pass through a superconducting body of the filter, and instead does along the penetrating pores, B in the penetrating pores and dB/dx on the surface of the filter are very high, which allows separation of argon from oxygen. 3 refs., 3 figs

  19. Electrokinetic pumps and actuators

    International Nuclear Information System (INIS)

    Phillip M. Paul

    2000-01-01

    Flow and ionic transport in porous media are central to electrokinetic pumping as well as to a host of other microfluidic devices. Electrokinetic pumping provides the ability to create high pressures (to over 10,000 psi) and high flow rates (over 1 mL/min) with a device having no moving parts and all liquid seals. The electrokinetic pump (EKP) is ideally suited for applications ranging from a high pressure integrated pump for chip-scale HPLC to a high flow rate integrated pump for forced liquid convection cooling of high-power electronics. Relations for flow rate and current fluxes in porous media are derived that provide a basis for analysis of complex microfluidic systems as well as for optimization of electrokinetic pumps

  20. Electrokinetic pumps and actuators

    Energy Technology Data Exchange (ETDEWEB)

    Phillip M. Paul

    2000-03-01

    Flow and ionic transport in porous media are central to electrokinetic pumping as well as to a host of other microfluidic devices. Electrokinetic pumping provides the ability to create high pressures (to over 10,000 psi) and high flow rates (over 1 mL/min) with a device having no moving parts and all liquid seals. The electrokinetic pump (EKP) is ideally suited for applications ranging from a high pressure integrated pump for chip-scale HPLC to a high flow rate integrated pump for forced liquid convection cooling of high-power electronics. Relations for flow rate and current fluxes in porous media are derived that provide a basis for analysis of complex microfluidic systems as well as for optimization of electrokinetic pumps.

  1. Frustrated magnetic response of a superconducting Nb film with a square lattice of columnar defects

    Energy Technology Data Exchange (ETDEWEB)

    Zadorosny, R; Ortiz, W A [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil); Lepienski, C M [Universidade Federal do Parana, Departamento de Fisica, Curitiba, PR (Brazil); Patino, E; Blamire, M G [Department of Materials Science, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)], E-mail: rafazad@df.ufscar.br

    2008-02-01

    The magnetic response of a superconducting system presenting a frustrated state is investigated. The system is a superconducting film with mechanically pierced columns, cooled in a field which is then removed. Frustration originates from the competition between return flux of a dipole - created by flux trapped in the empty columns - and flux exclusion by the surrounding superconductor in the Meissner state. The system resolves the incompatibility among conflicting constraints, leading to frustration, by eliminating return flux, which is possibly assimilated by nearby columns, as manifested by a sudden reduction of the magnetic moment on the decreasing field branch of the hysteresis loop.

  2. Frustrated magnetic response of a superconducting Nb film with a square lattice of columnar defects

    International Nuclear Information System (INIS)

    Zadorosny, R; Ortiz, W A; Lepienski, C M; Patino, E; Blamire, M G

    2008-01-01

    The magnetic response of a superconducting system presenting a frustrated state is investigated. The system is a superconducting film with mechanically pierced columns, cooled in a field which is then removed. Frustration originates from the competition between return flux of a dipole - created by flux trapped in the empty columns - and flux exclusion by the surrounding superconductor in the Meissner state. The system resolves the incompatibility among conflicting constraints, leading to frustration, by eliminating return flux, which is possibly assimilated by nearby columns, as manifested by a sudden reduction of the magnetic moment on the decreasing field branch of the hysteresis loop

  3. Magnetostatics of anisotropic superconducting ellipsoid

    International Nuclear Information System (INIS)

    Saif, A.G.

    1987-09-01

    The magnetization and the magnetic field distribution inside (outside) an anisotropic type II superconducting ellipsoid, with filamentary structure, is formulated. We have shown that the magnetic field in this case is different from that of the general anisotropic one. The nucleations of the flux lines for specimens with large demagnetization factors are theoretically studied. We have shown that the nucleations of the flux lines, for specimens with large demagnetization factor, appears at a field larger than that of ellipsoidal shape. (author). 15 refs

  4. [Computation of the K+, Na+ and Cl- fluxes through plasma membrane of animal cell with Na+/K+ pump, NKCC, NC cotransporters, and ionic channels with and without non-Goldman rectification in K+ channels. Norma and apoptosis].

    Science.gov (United States)

    Rubashkin, A A; Iurinskaia, V E; Vereninov, A A

    2010-01-01

    The balance of K+, Na+ and Cl- fluxes through cell membrane with the Na+/K+ pump, ion channels and NKCC and NC cotransporters is considered. It is shown that all unidirectional K+, Na+ and Cl- fluxes through cell membrane, permeability coefficients of ion channels and membrane potential can be computed for balanced ion distribution between cell and the medium if K+, Na+ and Cl- concentration in cell water and three fluxes are known: total Cl- flux, total K+ influx and ouabain-inhibitable "pump" component of the K+ influx. Changes in the mortovalent ion balance in lymphoid cells U937 induced to apoptosis by 1 microM staurosporine are analyzed as an example. It is found that the apoptotic shift in ion and water balance in studied cells is caused by a decrease in the pump activity which is accompanied by a decrease in the integral permeability of Na+ channels without significant increase in K+ and Cl- channel permeabilities. Computation shows that only a small part of the total fluxes of K+, Na+ and Cl- accounts for the fluxes via NKCC and NC cotransporters. Therefore, cotransport fluxes can not be studied using inhibitors.

  5. Large superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Jensen, Bogi Bech

    2012-01-01

    and the rotation speed is lowered in order to limit the tip speed of the blades. The ability of superconducting materials to carry high current densities with very small losses might facilitate a new class of generators operating with an air gap flux density considerably higher than conventional generators...... and thereby having a smaller size and weight [1, 2]. A 5 MW superconducting wind turbine generator forms the basics for the feasibility considerations, particularly for the YBCO and MgB2 superconductors entering the commercial market. Initial results indicate that a 5 MW generator with an active weight of 34...

  6. Superconducting push-pull flux quantum logic circuits

    International Nuclear Information System (INIS)

    Murphy, J.H.; Daniel, M.R.; Przybysz, J.X.

    1993-01-01

    A superconducting digital logic circuit is described comprising: a first circuit branch including first and second Josephson junctions electrically connected in series with each other; means for applying a positive bias voltage to a first end of said circuit branch; means for applying a negative bias voltage to a second end of said circuit branch; means for applying a first dual polarity input voltage signal to a first node in said circuit branch; and means for extracting a first output voltage signal from said first node in said circuit branch

  7. Analysis of Voltage Signals from Superconducting Accelerator Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Lizarazo, J.; Caspi, S.; Ferracin, P.; Joseph, J.; Lietzke, A. F.; Sabbi, G. L.; Wang, X.

    2009-10-30

    We present two techniques used in the analysis of voltage tap data collected during recent tests of superconducting magnets developed by the Superconducting Magnet Program at Lawrence Berkeley National Laboratory. The first technique was used on a quadrupole to provide information about quench origins that could not be obtained using the time-of-flight method. The second technique illustrates the use of data from transient flux imbalances occurring during magnet ramping to diagnose changes in the current-temperature margin of a superconducting cable. In both cases, the results of this analysis contributed to make improvements on subsequent magnets.

  8. Flux Flow, Pinning, and Resistive Behavior in Superconducting Networks

    International Nuclear Information System (INIS)

    Stephen Teitel

    2005-01-01

    Numerical simulators are used to study the behavior of interacting quantized vortices and vortex lines in superconducting networks, films, and three dimensional bulk samples. An emphasis is on the explanation of the phenomenological behavior of the ''high-Tc'' copper-oxide superconductors and related model systems

  9. Possibility of persistent voltage observation in a system of asymmetric superconducting rings

    International Nuclear Information System (INIS)

    Burlakov, A.A.; Gurtovoi, V.L.; Ilin, A.I.; Nikulov, A.V.; Tulin, V.A.

    2012-01-01

    The possibility of observing persistent voltage in superconducting rings of different arm widths is experimentally investigated. It was previously found that switching of the arms between superconducting and normal states by an AC current induces DC voltage oscillation in the magnetic field with a period corresponding to the flux quantum inside the ring. We used systems with a large number of asymmetric rings connected in series to investigate the possibility of observing this quantum phenomenon near the superconducting transition, where thermal fluctuations lead to switching of ring segments without an external influence and the persistent current is much smaller than in the superconducting state. -- Highlights: ► A possibility to observe the persistent voltage is investigated experimentally. ► The persistent voltage is a DC voltage observed at thermodynamic equilibrium. ► It oscillates in magnetic field like the persistent current in superconducting ring. ► The period of the oscillations corresponds to the flux quantum inside the ring. ► The quantum oscillations of the DC voltage were observed on asymmetric rings.

  10. Large impedances and Majorana bound states in superconducting circuits

    International Nuclear Information System (INIS)

    Ulrich, Jascha

    2017-01-01

    Superconducting circuits offer the opportunity to study quantum mechanics on mesoscopic scales unimpeded by dissipation. This fact and the nonlinearity of the Josephson inductance make it possible to use superconducting circuits as artificial atoms whose long-lived states can be selectively addressed and studied. A pronounced nonlinearity of the energy spectrum, however, requires quantum fluctuations of the flux across the Josephson junction which are large on the scale of the superconducting flux quantum Φ Q =h/2e. This implies charge fluctuations below the single Cooper-pair limit via flux-charge duality. The localization of charge leads to a strong susceptibility to interactions with charges in the environment which has motivated the search for schemes to decouple charges from their environment. This thesis is concerned with theoretical challenges arising from two complementary approaches to this problem: the realization of large impedances and the fractionalization of electrons by means of Majorana bound states. In recent years, the decoupling of charges from the environment through reactive large impedances, so-called ''superinductances'' L, has attracted much interest. These inductances feature small parasitic capacitance C such that the characteristic impedance √(L/C) is much larger than the superconducting resistance quantum R Q =h/4e 2 . Superinductances have various applications ranging from qubit designs such as the 0-π qubit or the fluxonium to impedance matching, Bloch oscillations and the stabilization of phase slips in superconducting nanowires. Although there exists a well-established formalism for the quantization of superconducting circuits in terms of node fluxes, this formalism is ill-suited for the description of fast flux transport with localized charges in large-impedance environments. In particular, the nonlinear capacitive behavior of phase slip junctions cannot be modeled in a straightforward way using node fluxes

  11. Second international Israeli conference on High Tc Superconductivity

    International Nuclear Information System (INIS)

    1993-01-01

    The superconductivity fields covered in this conference are: theory, applications, devices, flux properties high frequencies, Josephson junctions, magnetism, material sciences and physical properties of superconductors, spectroscopy and resonances and thin films

  12. Controlling the flux dynamics in superconductors by nanostructured magnetic arrays

    Science.gov (United States)

    Kapra, Andrey

    In this thesis we investigate theoretically how the critical current jc of nano-engineered mesoscopic superconducting film can be improved and how one can control the dynamics of the magnetic flux, e.g., the transition from flux-pinned to flux-flow regime, using arrays of magnetic nanostructures. In particularly we investigate: (1) Vortex transport phenomena in superconductors with deposited ferromagnetic structures on top, and the influence of the sample geometry on the critical parameters and on the vortex configurations. Changing geometry of the magnetic bars and magnetization of the bars will affect the critical current jc of the superconducting film. Such nanostructured ferromagnets strongly alter the vortex structure in its neighborhood. The influence of geometry, position and magnetization of the ferromagnet (single bar or regular lattice of the bars) on the critical parameters of the superconductor is investigated. (2) Effect of flux confinement in narrow superconducting channels with zigzag-shaped banks: the flux motion is confined in the transverse (perpendicular) direction of a diamond-cell-shape channel. The matching effect for the magnetic flux is found in the system relevantless of boundary condition. We discuss the dynamics of vortices in the samples and vortex pattern formation in the channel. We show how the inclusion of higher-Tc superconductor into the sample can lead to enhanced properties of the system. By adding an external driving force, we study the vortex dynamics. The different dynamic regimes are discussed. They allowed an effective control of magnetic flux in superconductors.

  13. Radiofrequency amplifier based on a DC superconducting quantum interference device

    International Nuclear Information System (INIS)

    Martinis, J.M.; Hilbert, C.; Clarke, J.

    1986-01-01

    A method is described of amplifying a radiofrequency signal consisting of: disposing a single symmetrically biased dc SQUID and an input coil within a superconducting shield, the dc SQUID having a superconducting ring interrupted by two shunted Josephson junctions, and the input coil being inductively coupled solely to the ring of the single SQUID, establishing a constant magnetic flux threading the SQUID ring, applying the radiofrequency signal to the input coil from outside of the superconducting shield, obtaining an amplified radiofrequency signal solely from across the ring of the single SQUID, transmitting the amplified radiofrequency signal from across the SQUID ring to the outside of the superconducting shield

  14. Integrated high-transition temperature magnetometer with only two superconducting layers

    DEFF Research Database (Denmark)

    Kromann, R.; Kingston, J.J.; Miklich, A.H.

    1993-01-01

    We describe the fabrication and testing of an integrated YBa2Cu3O7-x thin-film magnetometer consisting of a dc superconducting quantum interference device (SQUID), with biepitaxial grain boundary junctions, integrated with a flux transformer on a single substrate. Only two superconducting layers...... are required, the SQUID body serving as the crossunder that completes the multiturn flux transformer. The highest temperature at which any of the magnetometers functioned was 76 K. At 60 K the magnetic field gain of this device was 63, and the magnetic field noise was 160 fT Hz-1/2 at 2 kHz, increasing to 3...

  15. Design and investigations of the superconducting magnet system for the multipurpose superconducting electron cyclotron resonance ion source.

    Science.gov (United States)

    Tinschert, K; Lang, R; Mäder, J; Rossbach, J; Spädtke, P; Komorowski, P; Meyer-Reumers, M; Krischel, D; Fischer, B; Ciavola, G; Gammino, S; Celona, L

    2012-02-01

    The production of intense beams of heavy ions with electron cyclotron resonance ion sources (ECRIS) is an important request at many accelerators. According to the ECR condition and considering semi-empirical scaling laws, it is essential to increase the microwave frequency together with the magnetic flux density of the ECRIS magnet system. A useful frequency of 28 GHz, therefore, requires magnetic flux densities above 2.2 T implying the use of superconducting magnets. A cooperation of European institutions initiated a project to build a multipurpose superconducting ECRIS (MS-ECRIS) in order to achieve an increase of the performances in the order of a factor of ten. After a first design of the superconducting magnet system for the MS-ECRIS, the respective cold testing of the built magnet system reveals a lack of mechanical performance due to the strong interaction of the magnetic field of the three solenoids with the sextupole field and the magnetization of the magnetic iron collar. Comprehensive structural analysis, magnetic field calculations, and calculations of the force pattern confirm thereafter these strong interactions, especially of the iron collar with the solenoidal fields. The investigations on the structural analysis as well as suggestions for a possible mechanical design solution are given.

  16. Multi-proxy approach (Thorium-234, excess Barium) of export and remineralisation fluxes of carbon and biogenic elements associated with the oceanic biological pump

    International Nuclear Information System (INIS)

    Lemaitre, Nolwenn

    2017-01-01

    The main objective of this thesis is to improve our understanding of the different controls that affect the oceanic biological carbon pump. Particulate export and remineralisation fluxes were investigated using the thorium-234 ( 234 Th) and biogenic barium (Baxs) proxies. In the North Atlantic, the highest particulate organic carbon (POC) export fluxes were associated to biogenic (biogenic silica or calcium carbonate) and lithogenic minerals, ballasting the particles. Export efficiency was generally low (≤ 10%) and inversely related to primary production, highlighting a phase lag between production and export. The highest transfer efficiencies, i.e. the fraction of POC that reached 400 m, were driven by sinking particles ballasted by calcite or lithogenic minerals. The regional variation of meso-pelagic remineralisation was attributed to changes in bloom intensity, phytoplankton cell size, community structure and physical forcing (down-welling). Carbon remineralisation balanced, or even exceeded, POC export, highlighting the impact of meso-pelagic remineralisation on the biological pump with a near-zero, deep carbon sequestration for spring 2014. Export of trace metals appeared strongly influenced by lithogenic material advected from the margins. However, at open ocean stations not influenced by lithogenic matter, trace metal export rather depended on phytoplankton activity and biomass. A last part of this work focused on export of biogenic silica, particulate nitrogen and iron near the Kerguelen Island. This area is characterized by a natural iron-fertilization that increases export fluxes. Inside the fertilized area, flux variability is related to phytoplankton community composition. (author)

  17. Operating experience with a high capacity helium pump under supercritical conditions

    International Nuclear Information System (INIS)

    Lehmann, W.; Minges, J.

    1984-01-01

    This chapter discusses the development and testing of a high-capacity piston pump to provide forced cooling for large superconducting magnets. The pump is a three cylinder, vertically arranged single-acting piston pump equipped with a frequency controlled three-phase geared motor operating at room temperature. The pump is capable of delivering up to 150 g/s at a maximum speed of 310 rpm and under the inlet conditions of 4 bar/4.5 K. No decline was noticed in delivery head and efficiencies during more than 560 hours of operation. It is concluded that the pump satisfies all requirements for circulating large mass flows across great pressure differences as needed (e.g. in fusion magnet design)

  18. High power density superconducting motor for control applications

    International Nuclear Information System (INIS)

    Lopez, J; Granados, X; Lloberas, J; Torres, R; Grau, J; Maynou, R; Bosch, R

    2008-01-01

    A high dynamics superconducting low power motor for control applications has been considered for design. The rotor is cylindrical with machined bulks that generate the field by trapping flux in a four poles configuration. The toothless iron armature is wound by copper, acting iron only as magnetic screen. Details of the magnetic assembling, cryogenics and electrical supply conditioning will be reported. Improvements due to the use of a superconducting set are compared with performances of equivalent conventional motors

  19. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through Tc

    Science.gov (United States)

    Huang, Shichun; Kubo, Takayuki; Geng, R. L.

    2016-08-01

    Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80 K /m are studied under various applied magnetic fields from 5 to 20 μ T . We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity rfl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of d T /d s dependence of Rfl/Ba are also discussed.

  20. Thermally actuated magnetization flux pump in single-grain YBCO bulk

    Energy Technology Data Exchange (ETDEWEB)

    Yan Yu; Li Quan; Coombs, T A, E-mail: yy300@cam.ac.u, E-mail: ql229@cam.ac.u, E-mail: tac1000@cam.ac.u [EPEC Superconductivity Group, Electrical Engineering Department, Cambridge University, 9 J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom)

    2009-10-15

    Recent progress in material processing has proved that high temperature superconductors (HTS) have a great potential to trap large magnetic fields at cryogenic temperatures. For example, HTS are widely used in MRI scanners and in magnetic bearings. However, using traditional ways to magnetize, the YBCO will always need the applied field to be as high as the expected field on the superconductor or much higher than it, leading to a much higher cost than that of using permanent magnets. In this paper, we find a method of YBCO magnetization in liquid nitrogen that only requires the applied field to be at the level of a permanent magnet. Moreover, rather than applying a pulsed high current field on the YBCO, we use a thermally actuated material (gadolinium) as an intermedia and create a travelling magnetic field through it by changing the partial temperature so that the partial permeability is changed to build up the magnetization of the YBCO gradually after multiple pumps. The gadolinium bulk is located between the YBCO and the permanent magnet and is heated and cooled repeatedly from the outer surface to generate a travelling thermal wave inwards. In the subsequent experiment, an obvious accumulation of the flux density is detected on the surface of the YBCO bulk.

  1. Thermally actuated magnetization flux pump in single-grain YBCO bulk

    International Nuclear Information System (INIS)

    Yan Yu; Li Quan; Coombs, T A

    2009-01-01

    Recent progress in material processing has proved that high temperature superconductors (HTS) have a great potential to trap large magnetic fields at cryogenic temperatures. For example, HTS are widely used in MRI scanners and in magnetic bearings. However, using traditional ways to magnetize, the YBCO will always need the applied field to be as high as the expected field on the superconductor or much higher than it, leading to a much higher cost than that of using permanent magnets. In this paper, we find a method of YBCO magnetization in liquid nitrogen that only requires the applied field to be at the level of a permanent magnet. Moreover, rather than applying a pulsed high current field on the YBCO, we use a thermally actuated material (gadolinium) as an intermedia and create a travelling magnetic field through it by changing the partial temperature so that the partial permeability is changed to build up the magnetization of the YBCO gradually after multiple pumps. The gadolinium bulk is located between the YBCO and the permanent magnet and is heated and cooled repeatedly from the outer surface to generate a travelling thermal wave inwards. In the subsequent experiment, an obvious accumulation of the flux density is detected on the surface of the YBCO bulk.

  2. Results from the DITE pump-limiter experiment

    International Nuclear Information System (INIS)

    Johnson, P.C.; Fielding, S.J.; Matthews, G.F.; Pitts, R.; Pritchard, J.; Vayakis, G.

    1989-01-01

    Experiments have been carried out on the DITE tokamak with a large poloidal pump limiter of a relatively simple design. A particle exhaust into the pump limiter of 6% of the total particle flux leaving the plasma has been achieved. (orig.)

  3. Use of high-temperature superconducting films in superconducting bearings

    International Nuclear Information System (INIS)

    Cansiz, A.

    1999-01-01

    We have investigated the effect of high-temperature superconductor (HTS) films deposited on substrates that are placed above bulk HTSs in an attempt to reduce rotational drag in superconducting bearings composed of a permanent magnet levitated above the film/bulk HTS combination. According to the critical state model, hysteresis energy loss is inversely proportional to critical current density, J c , and because HTS films typically have much higher J c than that of bulk HTS, the film/bulk combination was expected to reduce rotational losses by at least one order of magnitude in the coefficient of fiction, which in turn is a measure of the hysteresis losses. We measured rotational losses of a superconducting bearing in a vacuum chamber and compared the losses with and without a film present. The experimental results showed that contrary to expectation, the rotational losses are increased by the film. These results are discussed in terms of flux drag through the film, as well as of the critical state model

  4. Microfabricated optically pumped magnetometer arrays for biomedical imaging

    Science.gov (United States)

    Perry, A. R.; Sheng, D.; Krzyzewski, S. P.; Geller, S.; Knappe, S.

    2017-02-01

    Optically-pumped magnetometers have demonstrated magnetic field measurements as precise as the best superconducting quantum interference device magnetometers. Our group develops miniature alkali atom-based magnetic sensors using microfabrication technology. Our sensors do not require cryogenic cooling, and can be positioned very close to the sample, making these sensors an attractive option for development in the medical community. We will present our latest chip-scale optically-pumped gradiometer developed for array applications to image magnetic fields from the brain noninvasively. These developments should lead to improved spatial resolution, and potentially sensitive measurements in unshielded environments.

  5. Superconducting generators for wind turbines: design considerations

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Abrahamsen, Asger Bech; Træholt, Chresten

    2010-01-01

    The harmonic content of high temperature superconductors (HTS) field winding in air-core high temperature superconducting synchronous machine (HTS SM) has been addressed in order to investigate tendency of HTS SM towards mechanical oscillation and additional loss caused by higher flux harmonic...

  6. The interplay of superconducting quantum circuits and propagating microwave states

    International Nuclear Information System (INIS)

    Goetz, Jan

    2017-01-01

    Superconducting circuit quantum electrodynamics (QED) has developed into a powerful platform for studying the interaction between matter and different states of light. In this context, superconducting quantum bits (qubits) act as artificial atoms interacting with quantized modes of the electromagnetic field. The field can be trapped in superconducting microwave resonators or propagating in transmission lines. In this thesis, we particularly study circuit QED systems where microwave fields are coupled with superconducting flux and transmon qubits. We optimize the coherence properties of the resonators, by analyzing loss mechanisms at excitation powers of approximately one photon on average. We find that two-level fluctuators associated with oxide layers at substrate and metal surfaces and metal-metal interfaces represent the predominant loss channel. Furthermore, we show how broadband thermal photon fields influence the relaxation and dephasing properties of a superconducting transmon qubit. To this end, we study several second-order loss channels of the transmon qubit and find that the broadband fields introduce a larger decay rate than expected from the Purcell filter defined by the resonator. Additionally, we show that qubit dephasing at the flux-insensitive point as well as low-frequency parameter fluctuations can be enhanced by thermal fields. Finally, we study how artificial atoms react to changes in inherent properties of the light fields. We perform a detailed analysis of the photon statistics of thermal fields using their relation to the qubits coherence properties. We quantitatively recover the expected n 2 + n-law for the photon number variance and confirm this result by direct correlation measurements. We then show a novel technique for the in-situ conversion of the interaction parity in light-matter interaction. To this end, we couple spatially controlled microwave fields to a flux qubit with two degrees of freedom.

  7. The interplay of superconducting quantum circuits and propagating microwave states

    Energy Technology Data Exchange (ETDEWEB)

    Goetz, Jan

    2017-06-26

    Superconducting circuit quantum electrodynamics (QED) has developed into a powerful platform for studying the interaction between matter and different states of light. In this context, superconducting quantum bits (qubits) act as artificial atoms interacting with quantized modes of the electromagnetic field. The field can be trapped in superconducting microwave resonators or propagating in transmission lines. In this thesis, we particularly study circuit QED systems where microwave fields are coupled with superconducting flux and transmon qubits. We optimize the coherence properties of the resonators, by analyzing loss mechanisms at excitation powers of approximately one photon on average. We find that two-level fluctuators associated with oxide layers at substrate and metal surfaces and metal-metal interfaces represent the predominant loss channel. Furthermore, we show how broadband thermal photon fields influence the relaxation and dephasing properties of a superconducting transmon qubit. To this end, we study several second-order loss channels of the transmon qubit and find that the broadband fields introduce a larger decay rate than expected from the Purcell filter defined by the resonator. Additionally, we show that qubit dephasing at the flux-insensitive point as well as low-frequency parameter fluctuations can be enhanced by thermal fields. Finally, we study how artificial atoms react to changes in inherent properties of the light fields. We perform a detailed analysis of the photon statistics of thermal fields using their relation to the qubits coherence properties. We quantitatively recover the expected n{sup 2} + n-law for the photon number variance and confirm this result by direct correlation measurements. We then show a novel technique for the in-situ conversion of the interaction parity in light-matter interaction. To this end, we couple spatially controlled microwave fields to a flux qubit with two degrees of freedom.

  8. Magnetic shielding of an inhomogeneous magnetic field source by a bulk superconducting tube

    International Nuclear Information System (INIS)

    Hogan, K; Fagnard, J-F; Wéra, L; Vanderheyden, B; Vanderbemden, P

    2015-01-01

    Bulk type-II irreversible superconductors can act as excellent passive magnetic shields, with a strong attenuation of low frequency magnetic fields. Up to now, the performances of superconducting magnetic shields have mainly been studied in a homogenous magnetic field, considering only immunity problems, i.e. when the field is applied outside the tube and the inner field should ideally be zero. In this paper, we aim to investigate experimentally and numerically the magnetic response of a high-T c bulk superconducting hollow cylinder at 77 K in an emission problem, i.e. when subjected to the non-uniform magnetic field generated by a source coil placed inside the tube. A bespoke 3D mapping system coupled with a three-axis Hall probe is used to measure the magnetic flux density distribution outside the superconducting magnetic shield. A finite element model is developed to understand how the magnetic field penetrates into the superconductor and how the induced superconducting shielding currents flow inside the shield in the case where the emitting coil is placed coaxially inside the tube. The finite element modelling is found to be in excellent agreement with the experimental data. Results show that a concentration of the magnetic flux lines occurs between the emitting coil and the superconducting screen. This effect is observed both with the modelling and the experiment. In the case of a long tube, we show that the main features of the field penetration in the superconducting walls can be reproduced with a simple analytical 1D model. This model is used to estimate the maximum flux density of the emitting coil that can be shielded by the superconductor. (paper)

  9. Fluctuation current in superconducting loops

    International Nuclear Information System (INIS)

    Berger, Jorge

    2012-01-01

    A superconducting loop that encloses noninteger flux holds a permanent current. On the average, this current is also present above T c , and has been measured in recent years. We are able to evaluate the permanent current within the TDGL or the Kramer-Watts-Tobin models for loops of general configuration, i.e., we don't require uniform cross section, material or temperature. We can also consider situations in which the width is not negligible in comparison to the radius. Our results agree with experiments. The situations with which we deal at present include fluctuation superconductivity in two-band superconductors, equilibrium thermal fluctuations of supercurrent along a weak link, and ratchet effects.

  10. Lightweight superconducting alternators

    International Nuclear Information System (INIS)

    Keim, T.A.

    1988-01-01

    One of the most efficient and most lightweight means of converting high-temperature heat energy to electricity is a turboalternator set. Turboalternators are potentially important components of burst-mode power systems, either chemical or nuclear powered. Also, they are probable key components in future electric propulsion systems. Existing examples of multimegawatt turbomachines have been optimized for a variety of aerospace uses, ranging from aircraft propulsion to rocket engine fuel pump drives. There is no corresponding history of multimegawatt alternators built to aerospace standards of mass, performance, and reliability. This paper discusses one of the few such development efforts presently in progress, and gives an indication of possible future potential. In large power ratings, superconducting generators offer substantial power density, specific weight, and efficiency advantages over competing technologies. A program at GE has led to the construction of a lightweight high-voltage 20-MW generator with a superconducting field winding. The first part of this paper describes the design of the generator. The second projects the capabilities of the generator to other ratings

  11. Effect of operating conditions on the performance of the bubble pump of absorption-diffusion refrigeration cycles

    Directory of Open Access Journals (Sweden)

    Benhmidene Ali

    2011-01-01

    Full Text Available The mathematical model will be able to predict the operated condition (required tube diameters, heat input and submergence ratio….. That will result in a successful bubble pump design and hence a refrigeration unit. In the present work a one-dimensional two-fluid model of boiling mixing ammonia-water under constant heat flux is developed. The present model is used to predict the outlet liquid and vapor velocities and pumping ratio for different heat flux input to pump. The influence of operated conditions such as: ammonia fraction in inlet solution and tube diameter on the functioning of the bubble pump is presented and discussed. It was found that, the liquid velocity and pumping ratio increase with increasing heat flux, and then it decreases. Optimal heat flux depends namely on tube diameter variations. Vapour velocity increases linearly with increasing heat flux under designed conditions.

  12. Scrape-off profiles and effects of limiter pumping in Tore Supra

    International Nuclear Information System (INIS)

    Budny, R.

    1986-11-01

    A one dimensional plasma scrape-off model was used to simulate Tore Supra discharges which are limited by various combinations of the pumped and inner limiters. Scrape-off profiles of the electron density and temperature, ion temperature, and neutral density are given. For each case, various fractions of the ion flux to the neutralizers were assumed to be pumped. Modifications of the scrap-off profiles caused by pumping are predicted. Pumping efficiencies are calculated including the effects of flux amplification caused by recycling. The pumping efficiency is estimated to be 8% for low-power discharges formed on the outer pumped limiter, 7.5% for intermediate-power discharges formed on the seven-module pumped-limiter system, and 5% for full-power discharges formed on both the inner limiter and the pumped-limiter system. The maximum particle removal rate is estimated to be 150 Tl/s

  13. Manipulation of a two-photon pump in superconductor - semiconductor heterostructures

    Science.gov (United States)

    Orth, Peter P.; Baireuther, Paul; Vekhter, Ilya; Schmalian, Joerg

    2014-03-01

    We investigate the photon statistics, entanglement and squeezing of a pn-junction sandwiched between two superconducting leads, and show that such an electrically-driven photon pump generates correlated and entangled pairs of photons. In particular, we demonstrate that the squeezing of the fluctuations in the quadrature amplitudes of the emitted light can be manipulated by changing the relative phase of the order parameters of the superconductors. This reveals how macroscopic coherence of the superconducting state can be used to tailor the properties of a two-photon state.

  14. Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation

    International Nuclear Information System (INIS)

    You, S.; Yun, G.S.; Bellan, P.M.

    2005-01-01

    Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated

  15. Determining Mass and Persistence of a Reactive Brominated-Solvent DNAPL Source Using Mass Depletion-Mass Flux Reduction Relationships During Pumping

    Science.gov (United States)

    Johnston, C. D.; Davis, G. B.; Bastow, T.; Annable, M. D.; Trefry, M. G.; Furness, A.; Geste, Y.; Woodbury, R.; Rhodes, S.

    2011-12-01

    Measures of the source mass and depletion characteristics of recalcitrant dense non-aqueous phase liquid (DNAPL) contaminants are critical elements for assessing performance of remediation efforts. This is in addition to understanding the relationships between source mass depletion and changes to dissolved contaminant concentration and mass flux in groundwater. Here we present results of applying analytical source-depletion concepts to pumping from within the DNAPL source zone of a 10-m thick heterogeneous layered aquifer to estimate the original source mass and characterise the time trajectory of source depletion and mass flux in groundwater. The multi-component, reactive DNAPL source consisted of the brominated solvent tetrabromoethane (TBA) and its transformation products (mostly tribromoethene - TriBE). Coring and multi-level groundwater sampling indicated the DNAPL to be mainly in lower-permeability layers, suggesting the source had already undergone appreciable depletion. Four simplified source dissolution models (exponential, power function, error function and rational mass) were able to describe the concentration history of the total molar concentration of brominated organics in extracted groundwater during 285 days of pumping. Approximately 152 kg of brominated compounds were extracted. The lack of significant kinetic mass transfer limitations in pumped concentrations was notable. This was despite the heterogeneous layering in the aquifer and distribution of DNAPL. There was little to choose between the model fits to pumped concentration time series. The variance of groundwater velocities in the aquifer determined during a partitioning inter-well tracer test (PITT) were used to parameterise the models. However, the models were found to be relatively insensitive to this parameter. All models indicated an initial source mass around 250 kg which compared favourably to an estimate of 220 kg derived from the PITT. The extrapolated concentrations from the

  16. Design and AC loss analysis of a superconducting synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Q [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Majoros, M [Department of Materials Science and Engineering, Ohio State University (United States); Hong, Z [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Campbell, A M [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Coombs, T A [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2006-11-15

    This paper gives a conceptual design of a superconducting synchronous motor consisting of both high-temperature superconducting rotating field winding and armature winding. The AC losses of the armature winding of the motor have been investigated experimentally and numerically, by considering the self-field of the superconducting coils and the rotating magnetic field exposed on the armature winding. The recent developments of YBCO-coated conductors present the possibility of achieving a wholly superconducting machine of significantly smaller size and weight than a conventional machine. Both the rotating field winding and the armature winding are composed of YBCO high-temperature superconducting (HTS) coils. A low AC loss armature winding design has been developed for this superconducting synchronous motor. The performance of the machine was investigated by modelling with the finite-element method. The machine's torque is calculated from first principles by considering the angle between the field and the armature main flux lines.

  17. Study on the flow reduction of forced flow superconducting magnet and its stable operation condition

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, Makoto [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    2001-03-01

    The forced flow superconducting coil especially made from a Cable-in-Conduit Conductor (CICC) is applied for large-scale devices such as fusion magnets and superconducting magnet energy storage (SMES) because it has high mechanical and electrical performance potential. The flow reduction phenomena caused by AC loss generation due to the pulsed operation was found based on the experimental results of three forced flow superconducting coils. And relation between the AC loss generation and flow reduction was defined from viewpoint of the engineering design and operation of the coils. Also the mechanism of flow reduction was investigated and stable operation condition under the flow reduction was clarified for forced flow superconducting coils. First, experiments of three different large-scale superconducting coils were carried out and experimental database of the flow reduction by AC loss generation was established. It was found experimentally that the flow reduction depends on the AC loss generation (W/m{sup 3}) in all of coils. It means the stable operation condition is defined not only the electro magnetism of superconducting coil but also flow condition. Mechanism of the flow reduction was investigated based on the experimental database. Hydraulics was applied to supercritical helium as a coolant. Also performances of the cryogenic pump by which coolant are supplied to the coil and friction of the superconductor as cooling path is considered for hydraulic estimation. The flow reduction of the coil is clarified and predictable by the equations of continuity, momentum and energy balance. Also total mass flow rate of coolant was discussed. The estimation method in the design phase was developed for total mass flow rate which are required under the flow reduction by AC losses. The friction of the superconductor and performance of cryogenic pump should be required for precise prediction of flow reduction. These values were obtained by the experiment data of coil and

  18. A double-superconducting axial bearing system for an energy storage flywheel model

    Science.gov (United States)

    Deng, Z.; Lin, Q.; Ma, G.; Zheng, J.; Zhang, Y.; Wang, S.; Wang, J.

    2008-02-01

    The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa2Cu3O7-x (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.

  19. Modeling and Error Analysis of a Superconducting Gravity Gradiometer.

    Science.gov (United States)

    1979-08-01

    quantum (bij magnetic flux linking elements i and u b N noise flux of SQUID W natural angular frequency W f angular frequency of forcing function Wi...SQUID superconducting quantum interference device TBAN tolerable background acceleration noise VIC voltage to current converter -xxiii- .4 Chapter I...to detect the minute vibrations induced in a 1 ton, cryogenically cooled and magnetically levitated gravitational wave antenna. The antenna concept

  20. Influence of magnetic history on flux jump fields

    International Nuclear Information System (INIS)

    Sosnowski, J.

    1986-01-01

    A formalism describing the fields at which flux jumps occur in hard superconductors has been confirmed by the description of an experimentally observed shift of flux jump fields in the second hysteresis loop of a Nb 3 Al superconducting sample. By fitting the theoretical model to experimental data, values of the proportionality parameter between the stability limit and the flux jump field, the first stability limit, and the first penetration field have been estimated

  1. Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

    Science.gov (United States)

    Gonnella, Dan; Kaufman, John; Liepe, Matthias

    2016-02-01

    Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

  2. Single-nitrogen-vacancy-center quantum memory for a superconducting flux qubit mediated by a ferromagnet

    Science.gov (United States)

    Lai, Yen-Yu; Lin, Guin-Dar; Twamley, Jason; Goan, Hsi-Sheng

    2018-05-01

    We propose a quantum memory scheme to transfer and store the quantum state of a superconducting flux qubit (FQ) into the electron spin of a single nitrogen-vacancy (NV) center in diamond via yttrium iron garnet (YIG), a ferromagnet. Unlike an ensemble of NV centers, the YIG moderator can enhance the effective FQ-NV-center coupling strength without introducing additional appreciable decoherence. We derive the effective interaction between the FQ and the NV center by tracing out the degrees of freedom of the collective mode of the YIG spins. We demonstrate the transfer, storage, and retrieval procedures, taking into account the effects of spontaneous decay and pure dephasing. Using realistic experimental parameters for the FQ, NV center and YIG, we find that a combined transfer, storage, and retrieval fidelity higher than 0.9, with a long storage time of 10 ms, can be achieved. This hybrid system not only acts as a promising quantum memory, but also provides an example of enhanced coupling between various systems through collective degrees of freedom.

  3. JET pump limiter

    International Nuclear Information System (INIS)

    Sonnenberg, K.; Deksnis, E.; Shaw, R.; Reiter, D.

    1988-01-01

    JET plans to install two pump limiter modules which can be used for belt-limiter, inner-wall and X-point discharges and, also, for 1-2s as the main limiter. A design is presented which is compatible with two diagnostic systems, and which allows partial removal of the pump limiter to provide access for remote-handling operations. The high heat-flux components are initially cooled during a pulse. Heat is removed between discharges by radiation and pressure contacts to a water-cooled support structure. The pumping edge will be made of annealed pyrolytic graphite. Exhaust efficiency has been estimated, for a 1-d edge model, using a Monte-Carlo calculation of neutral gas transport. When the pump limiter is operated together with other wall components we expect an efficiency of ≅ 5% (2.5 x 10 21 part/s). As a main limiter the efficiency increases to about 10%. (author)

  4. Chiral classical states in a rhombus and a rhombi chain of Josephson junctions with two-band superconducting elements

    CERN Document Server

    Dias, R G; Coutinho, B C; Martins, L P

    2014-01-01

    We present a study of Josephson junctions arrays with two-band superconducting elements in the highcapacitance limit. We consider two particular geometries for these arrays: a single rhombus and a rhombi chain with two-band superconducting elements at the spinal positions. We show that the rhombus shaped JJ circuit and the rhombi chain can be mapped onto a triangular JJ circuit and a JJ two-leg ladder, respectively, with zero effective magnetic flux, but with Josephson couplings that are magnetic flux dependent. If the two-band superconductors are in a sign-reversed pairing state, one observes transitions to or from chiral phase configurations in the mapped superconducting arrays when magnetic flux or temperature are varied. The phase diagram for these chiral configurations is discussed. When half-flux quantum threads each rhombus plaquette, new phase configurations of the rhombi chain appear that are characterized by the doubling of the periodicity of the energy density along the chain, with every other two-...

  5. The Influence of Grain Boundaries on the Properties of Superconducting Radio Frequency Cavity Niobium

    Science.gov (United States)

    Sung, Zu Hawn

    Grain boundaries (GBs) in niobium are multiply connected defects that may be responsible for significant performance degradation in superconducting radio frequency (RF) cavities. Magneto optical (MO) studies show that early flux penetration often occurs at GBs. One possible mechanism is that a locally reduced superconducting gap (Delta) at the GB reduces the depairing current density (Jb) and thus leads to a local reduction of the critical field. Alternatively vortices may penetrate the GB preferentially because of field enhancement at a GB groove, or for other reasons. In all these cases, the effect of high RF fields is to produce additional power dissipation, which in turn produces a reduction in quality factor (Q 0) and leads to a premature quench of the cavity. To further our understanding of the superconducting properties of SRF-quality Nb, we made extensive superconducting characterizations by magneto-optical imaging, which allowed assessment of the uniformity of properties on scales down to about 5 microm and by direct transport voltage-current methods in single and bi-crystals treated by standard cavity optimization treatments of BCP (buffered chemical treatment) and EP (electropolishing). We correlated these superconducting characterizations to microstructural properties using scanning laser and scanning electron microscopy and then thinned some samples to examine them at the nanometer scale using analytical transmission electron microscopy (TEM). We also developed special metallographic sample preparation techniques that allowed us to apply these experimental approaches to very soft superconducting RF niobium in the polished conditions characteristics of a real inner cavity surface. Using MO imaging, we found that GBs can preferentially admit flux penetration when the plane of a GB is aligned parallel to the vector of the external magnetic field. In DC transport in the superconducting state, we found preferential flux flow at the GB and could detect the

  6. Quasi-one-dimensional intermittent flux behavior in superconducting films

    OpenAIRE

    Qviller, A. J.; Yurchenko, V. V.; Galperin, Y. M.; Vestgården, J. I.; Mozhaev, Peter; Hansen, Jørn Bindslev; Johansen, T. H.

    2012-01-01

    Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa_{2}Cu_{3}O_{7-δ} deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a ...

  7. Superconducting qubits can be coupled and addressed as trapped ions

    Science.gov (United States)

    Liu, Y. X.; Wei, L. F.; Johansson, J. R.; Tsai, J. S.; Nori, F.

    2009-03-01

    Exploiting the intrinsic nonlinearity of superconducting Josephson junctions, we propose a scalable circuit with superconducting qubits (SCQs) which is very similar to the successful one now being used for trapped ions. The SCQs are coupled to the ``vibrational'' mode provided by a superconducting LC circuit or its equivalent (e.g., a superconducting quantum interference device). Both single-qubit rotations and qubit-LC-circuit couplings and/or decouplings can be controlled by the frequencies of the time-dependent magnetic fluxes. The circuit is scalable since the qubit-qubit interactions, mediated by the LC circuit, can be selectively performed, and the information transfer can be realized in a controllable way. [4pt] Y.X. Liu, L.F. Wei, J.R. Johansson, J.S. Tsai, F. Nori, Superconducting qubits can be coupled and addressed as trapped ions, Phys. Rev. B 76, 144518 (2007). URL: http://link.aps.org/abstract/PRB/v76/e144518

  8. Experimental investigation of biomimetic self-pumping and self-adaptive transpiration cooling.

    Science.gov (United States)

    Jiang, Pei-Xue; Huang, Gan; Zhu, Yinhai; Xu, Ruina; Liao, Zhiyuan; Lu, Taojie

    2017-09-01

    Transpiration cooling is an effective way to protect high heat flux walls. However, the pumps for the transpiration cooling system make the system more complex and increase the load, which is a huge challenge for practical applications. A biomimetic self-pumping transpiration cooling system was developed inspired by the process of trees transpiration that has no pumps. An experimental investigation showed that the water coolant automatically flowed from the water tank to the hot surface with a height difference of 80 mm without any pumps. A self-adaptive transpiration cooling system was then developed based on this mechanism. The system effectively cooled the hot surface with the surface temperature kept to about 373 K when the heating flame temperature was 1639 K and the heat flux was about 0.42 MW m -2 . The cooling efficiency reached 94.5%. The coolant mass flow rate adaptively increased with increasing flame heat flux from 0.24 MW m -2 to 0.42 MW m -2 while the cooled surface temperature stayed around 373 K. Schlieren pictures showed a protective steam layer on the hot surface which blocked the flame heat flux to the hot surface. The protective steam layer thickness also increased with increasing heat flux.

  9. Flux flow, pinning, and resistive behavior in superconducting networks

    International Nuclear Information System (INIS)

    Teitel, S.

    1993-10-01

    We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. The fluctuation of vortex lines in high temperature superconductors, in the presence of an external magnetic field, has been studied using a three dimensional XY model. We have continued earlier work and verified the existence of two distinct phase transitions in this model. As the vortex line lattice is heated, it melts first into a line liquid where superconductivity is destroyed for currents perpendicular to the applied magnetic field, but persists for currents parallel to the field. As heating continues, the thermal excitation of closed vortex line loops links all the lines together, leading to completely normal metal properties in all directions. Upon cooling of the vortex line liquid, we find that as the system width increases, one can get trapped into an entangled non-equilibrium state in which vortex line cuttings are frozen out on measurable nine scales. We have also continued simulations of the two dimensional Coulomb gas, as a model for vortex fluctuations in two dimensional arrays of Josephson junctions, and thin film superconductors. Our preliminary results support the accepted view of a Kosterlitz-Thouless melting of the vortex lattice, in the limit of a uniform continous film

  10. Experimental study of membrane pump for plasma devices

    International Nuclear Information System (INIS)

    Suzuki, Hajime; Ohyabu, Nobuyoshi; Nakamura, Yukio; Sagara, Akio; Motojima, Osamu; Livshits, A.; Notkin, M.; Busnyuk, A.; Komatsu, Kazuyuki

    1998-01-01

    Recycling control is a key to improve fusion plasma performance. The membrane pump has potential advantages for hydrogen pumping in fusion devices. However, there are unsolved issues for using membrane pump in LHD (Large Helical Device). The first issue is characteristics of the membrane pump under high incident hydrogen atom flux. The second issue is relationship between the surface condition and the pumping efficiency. Impurities from plasma may change the surface condition of the membrane. In order to solve these issues, a membrane pump system was fabricated and installed in a linear plasma device at NIFS (National Institute for Fusion Science). The membrane pump was successfully operated. (author)

  11. Broadband sample holder for microwave spectroscopy of superconducting qubits

    International Nuclear Information System (INIS)

    Averkin, A. S.; Karpov, A.; Glushkov, E.; Abramov, N.; Shulga, K.; Huebner, U.; Il'ichev, E.; Ustinov, A. V.

    2014-01-01

    We present a practical design and implementation of a broadband sample holder suitable for microwave experiments with superconducting integrated circuits at millikelvin temperatures. Proposed design can be easily integrated in standard dilution cryostats, has flat pass band response in a frequency range from 0 to 32 GHz, allowing the RF testing of the samples with substrate size up to 4 × 4 mm 2 . The parasitic higher modes interference in the holder structure is analyzed and prevented via design considerations. The developed setup can be used for characterization of superconducting parametric amplifiers, bolometers, and qubits. We tested the designed sample holder by characterizing of a superconducting flux qubit at 20 mK temperature

  12. Rotor-dynamic design aspects for a variable frequency drive based high speed cryogenic centrifugal pump in fusion devices

    International Nuclear Information System (INIS)

    Das, Jotirmoy; Vaghela, Hitensinh; Bhattacharya, Ritendra; Patel, Pratik; Shukla, Vinit; Shah, Nitin; Sarkar, Biswanath

    2015-01-01

    Superconducting magnets of large size are inevitable for fusion devices due to high magnetic field requirements. Forced flow cooling of the superconducting magnets with high mass flowrate of the order ∼3 kg/s is required to keep superconducting magnets within its safe operational boundaries during various plasma scenarios. This important requirement can be efficiently fulfilled by employing high capacity and high efficiency cryogenic centrifugal pumps. The efficiency > 70% will ensure overall lower heat load to the cryoplant. Thermo-hydraulic design of cryogenic centrifugal pump revealed that to achieve the operational regime with high efficiency, the speed should be ∼ 10,000 revolutions per minute. In this regard, the rotor-dynamic design aspect is quite critical from the operational stability point of view. The rotor shaft design of the cryogenic pump is primarily an outcome of optimization between thermal heat-in leak at cryogenic temperature level from ambient, cryogenic fluid impedance and designed rotation speed of the impeller wheel. The paper describes the basic design related to critical speed of the rotor shaft, rotor whirl and system instability prediction to explore the ideal operational range of the pump from the system stability point of view. In the rotor-dynamic analysis, the paper also describes the Campbell plots to ensure that the pump is not disturbed by any of the critical speeds, especially while operating near the nominal and enhanced operating modes. (author)

  13. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through T_{c}

    Directory of Open Access Journals (Sweden)

    Shichun Huang

    2016-08-01

    Full Text Available Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80  K/m are studied under various applied magnetic fields from 5 to 20  μT. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity r_{fl} of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of R_{fl}/B_{a} are also discussed.

  14. High-temperature superconducting conductors and cables

    International Nuclear Information System (INIS)

    Peterson, D.E.; Maley, M.P.; Boulaevskii, L.; Willis, J.O.; Coulter, J.Y.; Ullmann, J.L.; Cho, Jin; Fleshler, S.

    1996-01-01

    This is the final report of a 3-year LDRD project at LANL. High-temperature superconductivity (HTS) promises more efficient and powerful electrical devices such as motors, generators, and power transmission cables; however this depends on developing HTS conductors that sustain high current densities J c in high magnetic fields at temperatures near liq. N2's bp. Our early work concentrated on Cu oxides but at present, long wire and tape conductors can be best made from BSCCO compounds with high J c at low temperatures, but which are degraded severely at temperatures of interest. This problem is associated with thermally activated motion of magnetic flux lines in BSCCO. Reducing these dc losses at higher temperatures will require a high density of microscopic defects that will pin flux lines and inhibit their motion. Recently it was shown that optimum defects can be produced by small tracks formed by passage of energetic heavy ions. Such defects result when Bi is bombarded with high energy protons. The longer range of protons in matter suggests the possibility of application to tape conductors. AC losses are a major limitation in many applications of superconductivity such as power transmission. The improved pinning of flux lines reduces ac losses, but optimization also involves other factors. Measuring and characterizing these losses with respect to material parameters and conductor design is essential to successful development of ac devices

  15. Towards quantifying the response of the oceans’ biological pump to climate change

    Directory of Open Access Journals (Sweden)

    Philip Wallace Boyd

    2015-10-01

    Full Text Available The biological pump makes a major global contribution to the sequestration of carbon-rich particles in the oceans’ interior. This pump has many component parts from physics to ecology that together control its efficiency in exporting particles. Hence, the influence of climate change on the functioning and magnitude of the pump is likely to be complex and non-linear. Here, I employ a published 1-D coupled surface-subsurface Particulate Organic Carbon (POC export flux model to systematically explore the potential influence of changing oceanic conditions on each of the pump’s ‘moving parts’, in both surface and subsurface waters. These simulations were run for typical high (High Nutrient Low Chlorophyll, HNLC and low (Low Nutrient Low Chlorophyll, LNLC latitude sites. Next, I couple pump components that have common drivers, such as temperature, to investigate more complex scenarios involving concurrent climate-change mediated alteration of multiple ‘moving parts’ of the pump. Model simulations reveal that in the surface ocean, changes to algal community structure (i.e., a shift towards small cells has the greatest individual influence (decreased flux on downward POC flux in the coming decades. In subsurface waters, a shift in zooplankton community structure has the greatest single effect on POC flux (decreased in a future ocean. More complex treatments, in which up to ten individual factors (across both surface and subsurface processes were concurrently altered, ~ halved the POC flux at both high and low latitudes. In general climate-mediated changes to surface ocean processes had a greater effect on the magnitude of POC flux than alteration of subsurface processes, some of which negated one another. This relatively simple 1-D model provides initial insights into the most influential processes that may alter the future performance of this pump, and more importantly reveals many knowledge gaps that require urgent attention before we can

  16. Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

    International Nuclear Information System (INIS)

    EOz, E.; Myers, C.E.; Edwards, M.R.; Berlinger, B.; Brooks, A.; Cohen, S.A.

    2011-01-01

    The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-β plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMF o from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (τ fc ) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with τ fc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 10 3 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

  17. Pump limiter studies in Tore Supra

    International Nuclear Information System (INIS)

    Chatelier, M.; Bonnel, P.; Bruneau, J.L.; Gil, C.; Grisolia, C.; Loarer, T.; Martin, G.; Pegourie, B.; Rodriguez, L.

    1991-01-01

    The aim of the Tore Supra pump limiter program is to study particle exhaust with a pump limiter system in long-pulse discharges with continuous pellet fueling and strong auxiliary heating. The pump limiter system consists of six vertical modules, located at the bottom of the machine, and one horizontal module at the outer midplane. The instrumentation of the limiter included pressure gauges, a residual gas analyser Langmuir probes, a spectrometer and water calorimeters. Initial results in low-density discharges, with the outboard limiter only, showed a modest effect on the plasma density, while large exhaust fluxes were measured in the pump limiter, without any external fueling

  18. Particle removal with pump limiters in ISX-B

    International Nuclear Information System (INIS)

    Mioduszewski, P.; Emerson, L.C.; Simpkins, J.E.

    1983-01-01

    First pump limiter experiments were performed on ISX-B. Two pump limiter modules were installed in the top and bottom of one toroidal sector of the tokamak. The modules consist of inertia cooled, TiC coated graphite heads and Zr-Al getter pumps each with a pumping speed of 1000 to 2000 l/s. The objective of the initial experiments was the demonstration of plasma particle control with pump limiters. The first set of experiments were performed in ohmic discharges (OH) in which the effect of the pump limiters on the plasma density was clearly demonstrated. In discharges characterized by: I/sub p/ = 110 kA, B/sub T/ = 15 kG, anti n/sub e/ = 1 - 5 x 10 13 cm -3 and t = 0.3 s the pressure rise in the pump limiters was typically 2 mTorr with the pumps off and 0.7 mTorr after activating the pumps. When the pumps were activated, the line-average plasma density decreased by up to a factor 2 at identical gas flow rates. The second set of measurements were performed in neutral beam heated discharges (NBI) with injected powers between 0.6 MW and 1.0 MW. Due to a cooling problem on one of the Zr-Al pumps the NBI experiments were carried out with one limiter only. The maximum pressure observed in NBI-discharges was 5 mTorr without activating the pumps, i.e., approximately twice as high as in OH-discharges. The exhaust efficiency, which is defined as the removed particle flux over the total particle flux in the scrape-off layer is estimated to be 5%

  19. Analysis on fault current limiting and recovery characteristics of a flux-lock type SFCL with an isolated transformer

    International Nuclear Information System (INIS)

    Ko, Seckcheol; Lim, Sung-Hun; Han, Tae-Hee

    2013-01-01

    Highlights: ► Countermeasure to reduce the power burden of HTSC element consisting of the flux-lock type SFCL was studied. ► The power burden of HTSC element could be decreased by using the isolated transformer. ► The SFCL designed with the additive polarity winding could be confirmed to cause less power burden of the HTSC element. -- Abstract: The flux-lock type superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes. However, the superconducting element comprising the flux-lock type SFCL can be destructed when the high fault current passes through the SFCL. Therefore, the countermeasure to control the fault current and protect the superconducting element is required. In this paper, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, was proposed and the short-circuit experimental device to analyze the fault current limiting and the recovery characteristics of the flux-lock type SFCL with the isolated transformer were constructed. Through the short-circuit tests, the flux-lock type SFCL with the isolated transformer was confirmed to perform more effective fault current limiting and recovery operation compared to the flux-lock type SFCL without the isolated transformer from the viewpoint of the quench occurrence and the recovery time of the SFCL

  20. SNS Cryogenic Test Facility Kinney Vacuum Pump Commissioning and Operation at 2 K

    Energy Technology Data Exchange (ETDEWEB)

    Degraff, Brian D. [ORNL; Howell, Matthew P. [ORNL; Kim, Sang-Ho [ORNL; Neustadt, Thomas S. [ORNL

    2017-07-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) has built and commissioned an independent Cryogenic Test Facility (CTF) in support of testing in the Radio-frequency Test Facility (RFTF). Superconducting Radio-frequency Cavity (SRF) testing was initially conducted with the CTF cold box at 4.5 K. A Kinney vacuum pump skid consisting of a roots blower with a liquid ring backing pump was recently added to the CTF system to provide testing capabilities at 2 K. System design, pump refurbishment and installation of the Kinney pump will be presented. During the commissioning and initial testing period with the Kinney pump, several barriers to achieve reliable operation were experienced. Details of these lessons learned and improvements to skid operations will be presented. Pump capacity data will also be presented.

  1. SNS Cryogenic Test Facility Kinney Vacuum Pump Commissioning and Operation at 2 K

    Science.gov (United States)

    DeGraff, B.; Howell, M.; Kim, S.; Neustadt, T.

    2017-12-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) has built and commissioned an independent Cryogenic Test Facility (CTF) in support of testing in the Radio-frequency Test Facility (RFTF). Superconducting Radio-frequency Cavity (SRF) testing was initially conducted with the CTF cold box at 4.5 K. A Kinney vacuum pump skid consisting of a roots blower with a liquid ring backing pump was recently added to the CTF system to provide testing capabilities at 2 K. System design, pump refurbishment and installation of the Kinney pump will be presented. During the commissioning and initial testing period with the Kinney pump, several barriers to achieve reliable operation were experienced. Details of these lessons learned and improvements to skid operations will be presented. Pump capacity data will also be presented.

  2. Quantum heat engine with coupled superconducting resonators

    DEFF Research Database (Denmark)

    Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.

    2017-01-01

    We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....

  3. Triode for magnetic flux quanta.

    Science.gov (United States)

    Vlasko-Vlasov, Vitalii; Colauto, Fabiano; Benseman, Timothy; Rosenmann, Daniel; Kwok, Wai-Kwong

    We designed a magnetic vortex triode using an array of closely spaced soft magnetic Py strips on top of a Nb superconducting film. The strips act similar to the grid electrode in an electronic triode, where the electron flow is regulated by the grid potential. In our case, we tune the vortex motion by the magnetic charge potential of the strip edges, using a small magnetic field rotating in the film plane. The magnetic charges emerging at the stripe edges and proportional to the magnetization component perpendicular to the edge direction, form linear potential barriers or valleys for vortex motion in the superconducting layer. We directly imaged the normal flux penetration into the Py/Nb films and observed retarded or accelerated entry of the normal vortices depending on the in-plane magnetization direction in the stripes. The observed flux behavior is explained by interactions between magnetically charged lines and magnetic monopoles of vortices similar to those between electrically charged strings and point charges. We discuss the possibility of using our design for manipulation of individual vortices in high-speed, low-power superconducting electronic circuits. This work was supported by the U.S. DOE, Office of Science, Materials Sciences and Engineering Division, and Office of BES (contract DE-AC02-06CH11357). F. Colauto thanks the Sao Paulo Research Foundation FAPESP (Grant No. 2015/06.085-3).

  4. Embryogenic competence acquisition in sugarcane callus is associated with differential H+ pump abundance and activity.

    Science.gov (United States)

    Passamani, Lucas Z; Bertolazi, Amanda A; Ramos, Alessandro C; Santa-Catarina, Claudete; Thelen, Jay J; Silveira, Vanildo

    2018-06-22

    Somatic embryogenesis is an important biological process in several plant species, including sugarcane. Proteomics approaches have shown that H + pumps are differentially regulated during somatic embryogenesis; however, the relationship between H + flux and embryogenic competence is still unclear. This work aimed to elucidate the association between extracellular H + flux and somatic embryo maturation in sugarcane. We performed a microsomal proteomics analysis and analyzed changes in extracellular H + flux and H + pump (P-H + -ATPase, V-H + -ATPase and H + -PPase) activity in embryogenic and non-embryogenic callus. A total of 657 proteins were identified, 16 of which were H + pumps. We observed that P-H + -ATPase and H + -PPase were more abundant in embryogenic callus. Compared with non-embryogenic callus, embryogenic callus showed higher H + influx, especially on maturation day 14, as well as higher H+ pump activity (mainly P-H+-ATPase and H+-PPase activity). H+-PPase appears to be the major H + pump in embryogenic callus during somatic embryo formation, functioning in both vacuole acidification and PPi homeostasis. These results provide evidence for an association between higher H + pump protein abundance and, consequently, higher H + flux and embryogenic competence acquisition in the callus of sugarcane, allowing for optimization of the somatic embryo conversion process by modulating the activities of these H + pumps.

  5. Investigation of wire motion in superconducting magnets

    International Nuclear Information System (INIS)

    Ogitsu, T.; Tsuchiya, K.; Devred, A.

    1990-09-01

    The large Lorentz forces occuring during the excitation of superconducting magnets can provoke sudden motions of wire, which eventually release enough energy to trigger a quench. These wire motions are accompanied by two electromagnetic effects: an induced emf along the moved wire, and a local change in flux caused by the minute dislocation of current. Both effects cause spikes in the coil voltage. Voltage data recorded during the excitation of a superconducting quadrupole magnet which early exhibit such events are here reported. Interpretations of the voltage spikes in terms of energy release are also presented, leading to insights on the spectrum of the disturbances which occur in real magnets. 15 refs

  6. Anomalous reduction in the long-time flux creep relaxation in superconducting Ca10(Pt4As8)((Fe1‑x Pt x )2As2)5 (x ≈ 0.05) single crystals

    Science.gov (United States)

    Haberkorn, N.; Huang, Silu; Jin, R.

    2018-06-01

    We report the vortex dynamics of superconducting a Ca10(Pt4As8)((Fe1‑x Pt x )2As2)5 (x ≈ 0.05) single crystal with T c = 26 K investigated by performing magnetic measurements. The field dependence of the magnetization displays a second peak (SPM), typically related to a crossover between elastic and plastic vortex relaxation in a weak pinning scenario. Long-time flux creep relaxation measurements for fields smaller that of the SPM show that the vortex dynamics can be separated in two different regions. For magnetic fields smaller than the lower end of the SPM, glassy relaxation (with a characteristic glassy exponent μ) is observed. For magnetic fields between the lower end and the SPM, the flux creep rate decreases systematically to values below to the ones predicted by the collective theory. This effect can be understood by considering a stable vortex lattice configuration. As the field position of the SPM can be adjusted by modifying the quenched potential, our results suggest that extremely low flux creep relaxation rate may be tuned in many other superconducting materials.

  7. Development of an Ethernet enabled microcontroller based module for Superconducting Cyclotron ECR beam line control

    International Nuclear Information System (INIS)

    Chatterjee, M.; Koley, D.; Nabhiraj, P.Y.

    2012-01-01

    An Ethernet enabled control and data acquisition module is developed for remote control and monitoring of the ECR beam line equipment of the Superconducting Cyclotron. The PIC microcontroller based module supports multiple general purpose analog and digital inputs and outputs for interfacing with various equipments and an embedded web server. The remote monitoring and control of the equipment are achieved through the web based user interface. The user authenticated access to control parameters and module configuration parameters ensures the operational safety of the equipment under control. This module is installed in Superconducting Cyclotron ECR beam line for the control and monitoring of vacuum pumping modules, comprising of pumps, gate valves and dual vacuum gauges. The installation of these modules results in a distributed control with localised field cabling and hence better fault diagnosis. (author)

  8. About stability of levitating states of superconducting myxini of plasma traps-galateas

    International Nuclear Information System (INIS)

    Bishaev, A.M.; Bush, A.A.; Denis'uk, A.I.; D'yakonitsa, O.Y.; Kamentsev, K.Y.; Kozintseva, M.V.; Kolesnikova, T.G.; Shapovalov, M.M.; Voronchenko, S.A.; Gavrikov, M.B.; Savelyev, V.V.; Smirnov, P.G.

    2015-01-01

    To develop a plasma trap with levitating superconducting magnetic coils it is necessary to carry out the search of their stable levitating states. With this purpose, based upon the superconductor property to conserve the trapped magnetic flux, in the uniform gravitational field the analytical dependence of the potential energy of one or two superconducting rings, having trapped the given magnetic fluxes, in the field of the fixed ring with the constant current from the coordinates of the free rings and the deflection angle of their axes from the common axis of the magnetic system has been obtained in the thin ring approximation. Under magnetic fluxes of the same polarity in coils the existence of the found from the calculations equilibrium levitating states for the manufactured HTSC rings stable relative to the vertical shifts of levitating rings and to the deflection angle of their axes from the vertical has been confirmed experimentally

  9. Intrinsic Paramagnetic Meissner Effect Due to s-Wave Odd-Frequency Superconductivity

    Directory of Open Access Journals (Sweden)

    A. Di Bernardo

    2015-11-01

    Full Text Available In 1933, Meissner and Ochsenfeld reported the expulsion of magnetic flux—the diamagnetic Meissner effect—from the interior of superconducting lead. This discovery was crucial in formulating the Bardeen-Cooper-Schrieffer (BCS theory of superconductivity. In exotic superconducting systems BCS theory does not strictly apply. A classical example is a superconductor-magnet hybrid system where magnetic ordering breaks time-reversal symmetry of the superconducting condensate and results in the stabilization of an odd-frequency superconducting state. It has been predicted that under appropriate conditions, odd-frequency superconductivity should manifest in the Meissner state as fluctuations in the sign of the magnetic susceptibility, meaning that the superconductivity can either repel (diamagnetic or attract (paramagnetic external magnetic flux. Here, we report local probe measurements of faint magnetic fields in a Au/Ho/Nb trilayer system using low-energy muons, where antiferromagnetic Ho (4.5 nm breaks time-reversal symmetry of the proximity-induced pair correlations in Au. From depth-resolved measurements below the superconducting transition of Nb, we observe a local enhancement of the magnetic field in Au that exceeds the externally applied field, thus proving the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.

  10. Magnetic levitation force between a superconducting bulk magnet and a permanent magnet

    International Nuclear Information System (INIS)

    Wang, J J; He, C Y; Meng, L F; Li, C; Han, R S; Gao, Z X

    2003-01-01

    The current density J(ρ, z) in a disc-shaped superconducting bulk magnet and the magnetic levitation force F SBM z exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law E = E c (J/J c ) n and the material law B = μ 0 H. The magnetic levitation force F SBM z is dominated by the remnant current density J' 2 (ρ, z), which is induced by switching off the applied magnetizing field. High critical current density and flux creep exponent may increase the magnetic levitation force F SBM z . Large volume and high aspect ratio of the superconducting bulk can further enhance the magnetic levitation force F SBM z

  11. Small machinery for pumping and compressing helium near 40K

    International Nuclear Information System (INIS)

    Swift, W.L.; Sixsmith, H.

    1984-01-01

    There is a significant need for small, reliable pumps and compressors suitable for circulating helium at temperatures near 4 0 K. Most pumps or compressors which have been developed to data for these applications are designed for relatively limited use. They are generally used in laboratory environments where life requirements for the experiments may be relatively short, being of the order of several hundred hours. In recent years, several applications have been identified where pumps or compressors (at liquid helium temperatures) must have high reliability if they are to be used successfully. These applications include liquid helium circulation systems through superconducting magnets and transmission lines, and cold compression applications where the compressor is used as a vacuum pump to lower the temperature of a liquid helium bath. This paper discusses the technical considerations which must be taken into account in the design and development of machinery to meet these needs. The design of a centrifugal machine which can act as a helium pump or compressor is presented

  12. Seasonal copepod lipid pump promotes carbon sequestration in the deep North Atlantic.

    Science.gov (United States)

    Jónasdóttir, Sigrún Huld; Visser, André W; Richardson, Katherine; Heath, Michael R

    2015-09-29

    Estimates of carbon flux to the deep oceans are essential for our understanding of global carbon budgets. Sinking of detrital material ("biological pump") is usually thought to be the main biological component of this flux. Here, we identify an additional biological mechanism, the seasonal "lipid pump," which is highly efficient at sequestering carbon into the deep ocean. It involves the vertical transport and metabolism of carbon rich lipids by overwintering zooplankton. We show that one species, the copepod Calanus finmarchicus overwintering in the North Atlantic, sequesters an amount of carbon equivalent to the sinking flux of detrital material. The efficiency of the lipid pump derives from a near-complete decoupling between nutrient and carbon cycling—a "lipid shunt," and its direct transport of carbon through the mesopelagic zone to below the permanent thermocline with very little attenuation. Inclusion of the lipid pump almost doubles the previous estimates of deep-ocean carbon sequestration by biological processes in the North Atlantic.

  13. Process for applying a superconductive powder to a wide variety of substrates

    Science.gov (United States)

    Hooker, Matthew W.; Wise, Stephanie A.; Tran, Sang Q.

    1992-12-01

    A fine superconducting powder such as YBa2Cu3O(7-x), wherein x is less than one, is blended into a liquid mixture comprising an epoxy resin and a thinner. This liquid mixture with the blended superconducting powder is coated onto a substrate. Next, the thinner is evaporated and the remaining coating cured, resulting in a coating of cured epoxy resin having superconducting powder suspended therein. This coating exhibits the Meissner effect, i.e., it expels a magnetic flux which protects the substrate from external magnetic interference. Since the coated substrate need only be heated for evaporation and curing at relatively low temperatures compared to firing, the superconducting coating can be applied to a wide variety of different materials.

  14. Simulation of Field Dependence of Critical Current Densities of Bulk High Tc Superconducting Materials regarding Thermally Activated Flux Motion

    Science.gov (United States)

    Santosh, M.; Naik, S. Pavan Kumar; Koblischka, M. R.

    2017-07-01

    In the upcoming generation, bulk high temperature superconductors (HTS) will play a crucial and a promising role in numerous industrial applications ranging from Maglev trains to magnetic resonance imaging, etc. Especially, the bulk HTS as permanent magnets are suitable due to the fact that they can trap magnetic fields being several orders of magnitude higher than those of the best hard ferromagnets. The bulk HTS LREBa2Cu3O7-δ (LREBCO or LRE-123, LRE: Y, Gd, etc.,) materials could obtain very powerful compact superconducting super-magnets, which can be operated at the cheaper liquid nitrogen temperature or below due to higher critical temperatures (i.e., ∼90 K). As a result, the new advanced technology can be utilized in a more attractive manner for a variety of technological and medical applications which have the capacity to revolutionize the field. An understanding of the magnetic field dependence of the critical current density (J c(H)) is important to develop better adapted materials. To achieve this goal, a variety of Jc (H) behaviours of bulk LREBCO samples were modelled regarding thermally activated flux motion. In essence, the Jc (H) curves follows a certain criterion where an exponential model is applied. However, to fit the complete Jc (H) curve of the LRE-123 samples an unique model is necessary to explain the behavior at low and high fields. The modelling of the various superconducting materials could be understood in terms of the pinning mechanisms.

  15. Hydrogen pumping and release by graphite under high flux plasma bombardment

    International Nuclear Information System (INIS)

    Hirooka, Y.; Leung, W.K.; Conn, R.W.; Goebel, D.M.; Labombard, B.; Nygren, R.; Wilson, K.L.

    1988-01-01

    Inert gas (helium or argon) plasma bombardment has been found to increase the surface gas adsorptivity of isotropic graphite (POCO-graphite), which can then getter residual gases in a high vacuum system. The inert gas plasma bombardment was carried out at a flux ∼ 1 x 10 18 ions s -1 cm -2 to a fluence of the order of 10 21 ions/cm 2 and at temperatures around 800 degree C. The plasma bombarding energy was varied between 100 and 200 eV. The gettering speed of the activated graphite surface is estimated to be as large as 25 liters s -1 cm -2 at total pressures between 10 -6 and 10 -7 torr. The gettering capacity estimated is 0.025 torr-liter/cm 2 at room temperature. The gettering capability of graphite can be easily recovered by repeating inert gas plasma bombardment. The activated graphite surface exhibits a smooth, sponge-like morphology with significantly increased pore openings, which correlates with the observed increase in the surface gas adsorptivity. The activated graphite surface has been observed to pump hydrogen plasma particles as well. From calibrated H-alpha measurements, the dynamic hydrogen retention capacity is evaluated to be as large as 2 x 10 18 H/cm 2 at temperatures below 100 degree C and at a plasma bombarding energy of 300 eV

  16. Vortex dynamics in ferromagnetic/superconducting bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cieplak, M.Z.; Adamus, Z. [Polish Acad Sci, Inst Phys, PL-02668 Warsaw, (Poland); Konczykowski, M. [CEA, DSM, DRECAM, Lab Solides Irradies, Ecole Polytechnique, CNRS-UMR 7642, F-91128 Palaiseau (France); Zhu, L.Y.; Chien, C.L. [Johns Hopkins Univ, Dept Phys and Astron, Baltimore, MD 21218 (United States)

    2008-07-01

    The dependence of vortex dynamics on the geometry of magnetic domain pattern is studied in the superconducting/ferromagnetic bilayers, in which niobium is a superconductor, and Co/Pt multilayer with perpendicular magnetic anisotropy serves as a ferromagnetic layer. Magnetic domain patterns with different density of domains per surface area and different domain size, w, are obtained for Co/Pt with different thickness of Pt. The dense patterns of domains with the size comparable to the magnetic penetration depth (w {>=} {lambda}) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w {>=}{>=} {lambda}) enhance pinning less effectively and result in flux jumps during flux motion. (authors)

  17. Effects of ionizing scrape-off layers on local recycling in Tore Supra pump limiter experiments

    International Nuclear Information System (INIS)

    Chatelier, M.; Loarer, T.

    1992-01-01

    A series of ohmic discharges with active pumping in the Tore Supra outboard pump limiter has been analyzed with the DEGAS neutrals transport code and an analytic scrape-off layer (SOL) plasma model. Pumping speed and plenum pressure measurements indicated 5-10 torr.L/s throughput with only modest effects on density. A model is developed in which large exhaust fluxes, with little attendant effect on core plasma density, are explained in terms of SOL ionization of recycled and wall-desorbed neutrals. Particle balance with active pumping and constant line density requires that the wall return flux exceed the incident flux by approximately the pump throughput in the absence of external fueling. The radial profile of the H + source rate from ionization and dissociation of wall-desorbed molecules is seen to peak very near the radial position of the limiter throat. Consequently, a strong recycling vortex is created in the region of the limiter, with the ion flux amplified by factors of 2 at the outer limiter surfaces and > 3 within the limiter throat. The calculations indicate that less than 30% of the pump throughput is due to first-generation ions from the core efflux, with the balance from local recycling in the strongly ionizing SOL

  18. Orientation-free and differentially pumped addition of a low-flux reactive gas beam to a surface analysis system.

    Science.gov (United States)

    Harthcock, Colin; Jahanbekam, Abdolreza; Eskelsen, Jeremy R; Lee, David Y

    2016-11-01

    We describe an example of a piecewise gas chamber that can be customized to incorporate a low flux of gas-phase radicals with an existing surface analysis chamber for in situ and stepwise gas-surface interaction experiments without any constraint in orientation. The piecewise nature of this gas chamber provides complete angular freedom and easy alignment and does not require any modification of the existing surface analysis chamber. In addition, the entire gas-surface system is readily differentially pumped with the surface chamber kept under ultra-high-vacuum during the gas-surface measurements. This new design also allows not only straightforward reconstruction to accommodate the orientation of different surface chambers but also for the addition of other desired features, such as an additional pump to the current configuration. Stepwise interaction between atomic oxygen and a highly ordered pyrolytic graphite surface was chosen to test the effectiveness of this design, and the site-dependent O-atom chemisorption and clustering on the graphite surface were resolved by a scanning tunneling microscope in the nm-scale. X-ray photoelectron spectroscopy was used to further confirm the identity of the chemisorbed species on the graphite surface as oxygen.

  19. Vertical Josephson Interferometer for Tunable Flux Qubit

    Energy Technology Data Exchange (ETDEWEB)

    Granata, C [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Vettoliere, A [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Lisitskiy, M [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Rombetto, S [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Russo, M [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Ruggiero, B [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Corato, V [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy); Russo, R [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy); Silvestrini, P [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy)

    2006-06-01

    We present a niobium-based Josephson device as prototype for quantum computation with flux qubits. The most interesting feature of this device is the use of a Josephson vertical interferometer to tune the flux qubit allowing the control of the off-diagonal Hamiltonian terms of the system. In the vertical interferometer, the Josephson current is precisely modulated from a maximum to zero with fine control by a small transversal magnetic field parallel to the rf superconducting loop plane.

  20. Impact of cool-down conditions at T_{c} on the superconducting rf cavity quality factor

    Directory of Open Access Journals (Sweden)

    J.-M. Vogt

    2013-10-01

    Full Text Available Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS rely on continuous wave (CW operation for which superconducting radio-frequency (SRF systems are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and for many CW accelerators the complexity as well as the investment and operating costs of the cryoplant can prove to be prohibitive. We investigated ways to reduce the dynamic losses by improving the residual resistance (R_{res} of niobium cavities. Both the material treatment and the magnetic shielding are known to have an impact. In addition, we found that R_{res} can be reduced significantly when the cool-down conditions during the superconducting phase transition of the niobium are optimized. We believe that not only do the cool-down conditions impact the level to which external magnetic flux is trapped in the cavity but also that thermoelectric currents are generated which in turn create additional flux that can be trapped. Therefore, we investigated the generation of flux and the dynamics of flux trapping and release in a simple model niobium-titanium system that mimics an SRF cavity in its helium tank. We indeed found that thermal gradients along the system during the superconducting transition can generate a thermoelectric current and magnetic flux, which subsequently can be trapped. These effects may explain the observed variation of the cavity’s R_{res} with cool-down conditions.

  1. Superconducting cavity development at RRCAT

    International Nuclear Information System (INIS)

    Joshi, S.C.

    2015-01-01

    Raja Ramanna Centre for Advanced Technology (RRCAT), Indore pursuing a program on 'R and D Activities for High Energy Proton Linac based Spallation Neutron Source'. Spallation neutron source (SNS) facility will provide high flux pulse neutrons for research in the areas of condensed matter physics, materials science, chemistry, biology and engineering. This will complement the existing synchrotron light source facility, INDUS-2 at RRCAT and reactor based neutron facilities at BARC. RRCAT is also participating in approved mega project on 'Physics and Advanced Technology for High Intensity Proton Accelerator' to support activities of Indian Institutions - Fermilab Collaboration (IIFC). The SNS facility will have a 1 GeV superconducting proton injector linac and 1 GeV accumulator ring. The linac will comprise of large number of superconducting radio-frequency (SCRF) cavities operating at different RF frequencies housed in suitable cryomodules. Thus, an extensive SCRF cavity infrastructure setup is being established. In addition, a scientific and technical expertise are also being developed for fabrication, processing and testing of the SCRF cavities for series production. The paper presents the status of superconducting cavity development at RRCAT

  2. Magnetic levitation force between a superconducting bulk magnet and a permanent magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J J; He, C Y; Meng, L F; Li, C; Han, R S; Gao, Z X [Department of Physics, Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2003-04-01

    The current density J({rho}, z) in a disc-shaped superconducting bulk magnet and the magnetic levitation force F{sup SBM}{sub z} exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law E = E{sub c}(J/J{sub c}){sup n} and the material law B = {mu}{sub 0}H. The magnetic levitation force F{sup SBM}{sub z} is dominated by the remnant current density J'{sub 2}({rho}, z), which is induced by switching off the applied magnetizing field. High critical current density and flux creep exponent may increase the magnetic levitation force F{sup SBM}{sub z}. Large volume and high aspect ratio of the superconducting bulk can further enhance the magnetic levitation force F{sup SBM}{sub z}.

  3. Superconductivity

    International Nuclear Information System (INIS)

    Palmieri, V.

    1990-01-01

    This paper reports on superconductivity the absence of electrical resistance has always fascinated the mind of researchers with a promise of applications unachievable by conventional technologies. Since its discovery superconductivity has been posing many questions and challenges to solid state physics, quantum mechanics, chemistry and material science. Simulations arrived to superconductivity from particle physics, astrophysic, electronics, electrical engineering and so on. In seventy-five years the original promises of superconductivity were going to become reality: a microscopical theory gave to superconductivity the cloth of the science and the level of technological advances was getting higher and higher. High field superconducting magnets became commercially available, superconducting electronic devices were invented, high field accelerating gradients were obtained in superconductive cavities and superconducting particle detectors were under study. Other improvements came in a quiet progression when a tornado brought a revolution in the field: new materials had been discovered and superconductivity, from being a phenomenon relegated to the liquid Helium temperatures, became achievable over the liquid Nitrogen temperature. All the physics and the technological implications under superconductivity have to be considered ab initio

  4. Magnetic shield effect simulation of superconducting film shield covering directly coupled HTS dc-SQUID magnetometer

    International Nuclear Information System (INIS)

    Terauchi, N.; Noguchi, S.; Igarashi, H.

    2011-01-01

    A superconducting film shield over a SQUID ring improves the robustness of the SQUID with respect to magnetic noise. Supercurrent in the SQUID magnetometer and the superconducting film shield were simulated. The superconducting film shield reduces the influence of the external magnetic field on the SQUID ring. An HTS SQUID is a high sensitive magnetic sensor. In recent years, the HTS SQUID is widely used in various applications. In some applications, high robustness with respect to magnetic noise is required to realize stable operation at outside of a magnetic shielding room. The target of this paper is a directly coupled HTS dc-SQUID magnetometer. To enhance the robustness of the SQUID magnetometer, use of a superconducting thin film shield has been proposed. The magnetic field directly penetrating the SQUID ring causes the change of the critical current of Josephson junction, and then the SQUID magnetometer transitions into inoperative state. In order to confirm the magnetic shield effect of the superconducting film shield, electromagnetic field simulation with 3D edge finite element method was performed. To simulate the high temperature superconductor, E-J characteristics and c-axis anisotropy are considered. To evaluate the effect of the superconducting film shield, an external magnetic field which is supposed to be a magnetic noise is applied. From the simulation results, the time transition of the magnetic flux penetrating the SQUID ring is investigated and the effect of the superconducting film shield is confirmed. The amplitude of the magnetic flux penetrating the SQUID ring can be reduced to about one-sixth since the superconducting film shield prevents the magnetic noise from directly penetrating the SQUID ring.

  5. Weakening of flux-pinning strength for high-Tc superconductors in an alternating magnetic field

    International Nuclear Information System (INIS)

    Chen, Q.Y.

    1992-01-01

    This paper reports on the flux-pinning forces in high temperature superconductors which were found to be weakened in an ac field as the applied field strength or the frequency increases. In the weakly pinned regime, flux dynamics could be described with the concept of magnetic diffusion. Flux-motion-induced finite resistivity could lead to significant skin-effect which was reflected in the ac screening effectiveness. The frequency dependence of the relative local field within a superconducting hollow cylinder were used to deduce the flux-motion resistivity ρ. For superconducting YB 2 Cu 3 O 7 - x compounds at 77K it was found that ρ ∼(mu, Omega)-cm. The corresponding magnetic diffusion coefficient was ∼ 224 cm 2 /s. At 750 Hz the skin depth is around 1.54 mm as compared with the 2-mm sample wall thickness

  6. Flux transformers made of commercial high critical temperature superconducting wires.

    Science.gov (United States)

    Dyvorne, H; Scola, J; Fermon, C; Jacquinot, J F; Pannetier-Lecoeur, M

    2008-02-01

    We have designed flux transformers made of commercial BiSCCO tapes closed by soldering with normal metal. The magnetic field transfer function of the flux transformer was calculated as a function of the resistance of the soldered contacts. The performances of different kinds of wires were investigated for signal delocalization and gradiometry. We also estimated the noise introduced by the resistance and showed that the flux transformer can be used efficiently for weak magnetic field detection down to 1 Hz.

  7. Motor current and leakage flux signature analysis technique for condition monitoring

    International Nuclear Information System (INIS)

    Pillai, M.V.; Moorthy, R.I.K.; Mahajan, S.C.

    1994-01-01

    Till recently analysis of vibration signals was the only means available to predict the state of health of plant equipment. Motor current and leakage magnetic flux signature analysis is acquiring importance as a technique for detection of incipient damages in the electrical machines and as a supplementary technique for diagnostics of driven equipment such as centrifugal and reciprocating pumps. The state of health of the driven equipment is assessed by analysing time signal, frequency spectrum and trend analysis. For example, the pump vane frequency, piston stroke frequency, gear frequency and bearing frequencies are indicated in the current and flux spectra. By maintaining a periodic record of the amplitudes of various frequency lines in the frequency spectra, it is possible to understand the trend of deterioration of parts and components of the pump. All problems arising out of inappropriate mechanical alignment of vertical pumps are easily identified by a combined analysis of current, flux and vibration signals. It is found that current signature analysis technique is a sufficient method in itself for the analysis of state of health of reciprocating pumps and compressors. (author). 10 refs., 4 figs

  8. Superconducting and hybrid systems for magnetic field shielding

    International Nuclear Information System (INIS)

    Gozzelino, L; Gerbaldo, R; Ghigo, G; Laviano, F; Truccato, M; Agostino, A

    2016-01-01

    In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a superconducting (MgB 2 ) and in a hybrid configuration (MgB 2 /Fe) as a function of the applied magnetic field and of the position. The calculations are carried out using the vector potential formalism, taking into account simultaneously the non-linear properties of both the superconducting and the ferromagnetic material. On the basis of the good agreement between the experimental and the computed data we apply the same model to study the influence of the geometric parameters of the ferromagnetic cup as well as of the thickness of the lateral gap between the two cups on the shielding properties of the superconducting cup. The results show that in the considered non-ideal geometry, where the edge effect in the flux penetration cannot be disregarded, the superconducting shield is always the most efficient solution at low magnetic fields. However, a partial recovery of the shielding capability of the hybrid configuration occurs if a mismatch in the open edges of the two cups is considered. In contrast, at high magnetic fields the hybrid configurations are always the most effective. In particular, the highest shielding factor was found for solutions with the ferromagnetic cup protruding over the superconducting one. (paper)

  9. Integrated flux-flow oscillators for submillimeter wave receivers

    International Nuclear Information System (INIS)

    Koshelets, V.P.; Shchukin, A.V.; Shitov, S.V.; Filippenko, L.V.; Fischer, G.M.; Mygind, J.

    1994-01-01

    A superconducting Flux-Flow Oscillator (FFO) integrated on the same chip with a small Josephson junction detector has been experimentally investigated in the frequency range 100 - 450 GHz. Both the emitted power and the frequency of the FFO can be varied by adjusting the dc bias current and/or the applied dc magnetic field. Microwave powers as high as 0.3 μW have been measured at 375 GHz. The spectral width of the FFO is about 1 MHz as estimated from harmonic mixing experiments. Also a fully integrated superconducting submillimeter wave receiver using the FFO as local oscillator has been successfully tested. The circuit included coupling transformers, a superconducting variable attenuator and a detector junction with tuned-out capacitance. (orig.)

  10. The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

    International Nuclear Information System (INIS)

    Roy, S B; Sahni, V C; Myneni, G R

    2009-01-01

    We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m -1 ) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

  11. The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Roy, S. B.; Myneni, G. R.; Sahni, V. C.

    2009-10-01

    We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m-1) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

  12. Thermo-electric pump

    International Nuclear Information System (INIS)

    Georges, J.-L.; Veyret, J.-F.

    1973-01-01

    Description is given of a thermo-pump for electrically conductive liquid fluids, e.g. for a liquid metal such as sodium. This pump is characterized in that the piping for the circulation of the conductive liquid is constituted by a plurality of conduits defined by two co-axial cylinders and two walls parallel to their axis. Each conduit limited outside by a magnet, inside by a mild-iron tube, and laterally by two materials forming a thermocouple. The electric current generated by that thermo-couple and the magnetic flux generated by the magnets both loop the loop through an outer cylindrical nickel shell. This can be applied to sodium circulation loops for testing nuclear fuel elements [fr

  13. Operation of a forced two phase cooling system on a large superconducting magnet

    International Nuclear Information System (INIS)

    Green, M.A.; Burns, W.A.; Eberhard, P.H.; Gibson, G.H.; Pripstein, M.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Van Slyke, H.

    1980-05-01

    This paper describes the operation of a forced two phase cooling system on a two meter diameter superconducting solenoid. The magnet is a thin high current density superconducting solenoid which is cooled by forced two phase helium in tubes around the coil. The magnet, which is 2.18 meters in diameter and 3.4 meters long, has a cold mass of 1700 kg. The two phase cooling system contains less than 300 liters of liquid helium, most of which is contained in a control dewar. This paper describes the operating characteristics of the LBL two phase forced cooling system during cooldown and warm up. The paper presents experimental data on operations of the magnet using either a helium pump or the refrigerator compressor to circulate two phase helium through the superconducting coil cooling tubes

  14. Advances in superconductivity: new materials, critical currents and devices

    International Nuclear Information System (INIS)

    Pinto, R.; Malik, S.K.; Grover, A.K.; Ayyub, P.

    1997-01-01

    The discovery of superconductivity in the cuprates produced an explosive growth in research, driven by the quest for higher and higher superconducting transition temperatures. In the initial stages, the excitement was tremendous both in the physical sciences and in engineering. However, the complexity of the new materials on the one hand, and the absence of a viable theory on the other, have made further developments much more difficult. It is to be expected therefore, that the early excitement and the subsequent rapid advances have paved the way for more systematic and detailed studies of all aspects of superconductivity. The International Symposium was intended to provide a forum to review the progress in selected areas in superconductivity. The emphasis was on experimental and theoretical studies of the new superconductors, advances in the theoretical understanding, progress in studies of flux pinning and vortex dynamics which affect critical currents, and developments of novel material synthesis methods. Recent developments in the twin areas of thin films and devices were extensively discussed during the symposium. Papers relevant to INIS are indexed separately

  15. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  16. Melt formed superconducting joint between superconducting tapes

    International Nuclear Information System (INIS)

    Benz, M.G.; Knudsen, B.A.; Rumaner, L.E.; Zaabala, R.J.

    1992-01-01

    This patent describes a superconducting joint between contiguous superconducting tapes having an inner laminate comprised of a parent-metal layer selected from the group niobium, tantalum, technetium, and vanadium, a superconductive intermetallic compound layer on the parent-metal layer, a reactive-metal layer that is capable of combining with the parent-metal and forming the superconductive intermetallic compound, the joint comprising: a continuous precipitate of the superconductive intermetallic compound fused to the tapes forming a continuous superconducting path between the tapes

  17. The two Josephson junction flux qubit with large tunneling amplitude

    International Nuclear Information System (INIS)

    Shnurkov, V.I.; Soroka, A.A.; Mel'nik, S.I.

    2008-01-01

    In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and form of the potential barrier, which is determined by quantum-state engineering of the flux qubit circuit. The simplest circuit of the flux qubit is a superconducting loop interrupted by a Josephson nanoscale tunnel junction. The tunneling amplitude between two macroscopically different states can be increased substantially by engineering of the qubit circuit if the tunnel junction is replaced by a ScS contact. However, only Josephson tunnel junctions are particularly suitable for large-scale integration circuits and quantum detectors with present-day technology. To overcome this difficulty we consider here a flux qubit with high energy-level separation between the 'ground' and 'excited' states, consisting of a superconducting loop with two low-capacitance Josephson tunnel junctions in series. We demonstrate that for real parameters of resonant superposition between the two macroscopic states the tunneling amplitude can reach values greater than 1 K. Analytical results for the tunneling amplitude obtained within the semiclassical approximation by the instanton technique show good correlation with a numerical solution

  18. Report on the achievements in fiscal 1999. Research and development on a basic technology to apply superconductivity (Research and development on a basic technology to apply superconductivity); 1999 nendo chodendo oyo kiban gijutsu kenkyu kaihatsu seika hokokusho. Chodendo oyo kiban gijutsu kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-05-01

    The development of a basic technology to improve superconductivity characteristics has performed (1) studies on the high-temperature superconductivity mechanism, (2) studies on the critical current mechanism, and (3) search for materials. In Item (1), composition and temperature dependence were investigated by measuring superconductivity gap and change in the electron state of pseudo gap using photo-electron spectra and Raman scattering spectra. In Item (2), magnetic flux behavior in the vicinity of the irreversible line was investigated on magnetic flux dynamics of Bi2212 by measuring magnetic resistance and magnetization. High viscosity condition having strong magnetic flux liquid zone was discovered. In Item (3), Sr was used in place of Ba as the constituting element, and several new mercury-based superconductors were synthesized successfully by using the high pressure synthesizing method. In developing superconductive bulk materials and wire materials, elucidation was given on (1) an element technology for high magnetic power bulk materials, (2) an element technology for high critical temperature bulk materials, (3) a fundamental technology for manufacturing next generation wire materials, (4) a fundamental technology for manufacturing next generation large current conductors, and (5) growth mechanism in wire material crystals. Development of laminating and processing technologies for superconductive materials has worked on (1) a single crystal substrate technology, (2) a thin film lamination technology, (3) a standard bonding technology, (4) an advanced bonding technology, and (5) a thin film and bond evaluation technology. (NEDO)

  19. Potential of Partially Superconducting Generators for Large Direct-Drive Wind Turbines

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Abrahamsen, Asger Bech

    2017-01-01

    This paper aims at assessing the potential of partially superconducting generators for 10 MW direct-drive wind turbines by investigating their performance for a very wide range of excitation currents. Performance indicators such as shear stress and efficiency and other generator characteristics...... are compared for 12 different generator topologies. To be sufficiently attractive, superconducting generators must have significant advantages over permanent magnet direct-drive generators, which typically have shear stresses of the order of 53 kPa and efficiencies of 96%. Therefore, we investigate what...... they achieve this performance. By examining the maximum magnetic flux density at the location of the superconducting field winding, feasible superconductors can be chosen according to their engineering current density capabilities. It is found that high- and low-temperature superconductors can meet...

  20. Radiation effects on superconductivity in A15 materials

    International Nuclear Information System (INIS)

    Faehnle, M.

    1981-01-01

    At present the A15 superconductor Nb 3 Sn is one of the most attractive materials for the design of magnet systems for fusion reactors. There the materials are exposed to a high flux of neutrons up to 10 18 to 10 19 n/cm 2 during a continuous fusion reactor operation within ten years. As a result the critical parameters of the superconducting materials are changed which must be taken into account when designing reliable magnet systems. The neutron radiation damage in A15 materials thereby is characterized by small highly disordered regions within a less disordered matrix. The highly disordered regions are responsible for the increase of the critical current density after low-dose neutron irradiation of non-optimized materials and have an influence on the superconducting transition width. In contrast, the change of the superconducting parameters after high-dose irradiation may be understood essentially by considering the properties of the matrix alone. 23 refs

  1. Spectroscopy and coherent manipulation of single and coupled flux qubits

    International Nuclear Information System (INIS)

    Wu Yu-Lin; Deng Hui; Huang Ke-Qiang; Tian Ye; Yu Hai-Feng; Xue Guang-Ming; Jin Yi-Rong; Li Jie; Zhao Shi-Ping; Zheng Dong-Ning

    2013-01-01

    Measurements of three-junction flux qubits, both single flux qubits and coupled flux qubits, using a coupled direct current superconducting quantum interference device (dc-SQUID) for readout are reported. The measurement procedure is described in detail. We performed spectroscopy measurements and coherent manipulations of the qubit states on a single flux qubit, demonstrating quantum energy levels and Rabi oscillations, with Rabi oscillation decay time T Rabi = 78 ns and energy relaxation time T 1 = 315 ns. We found that the value of T Rabi depends strongly on the mutual inductance between the qubit and the magnetic coil. We also performed spectroscopy measurements on inductively coupled flux qubits. (general)

  2. Design and performance of main vacuum pumping system of SST-1 Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Ziauddin, E-mail: ziauddin@ipr.res.in; Pathan, Firozkhan; George, Siju; Dhanani, Kalpesh; Paravastu, Yuvakiran; Semwal, Pratibha; Pradhan, Subrata

    2014-01-15

    Highlights: •SST-1 Tokamak was successfully commissioned. •Vacuum vessel and cryostat were pumped down to 6.3 × 10{sup −7} mbar and 1.3 × 10{sup −5} mbar. •Leaks developed during baking were detected in-situ by RGA and confirmed later on. •Cryo-pumping effect was observed when LN2 thermal shields reached below 273 K. •Non-standard aluminum wire-seals have shown leak tightness < 1.0 × 10{sup −9} mbar l/s. -- Abstract: Steady-state Superconducting Tokamak (SST-1) was installed and it is commissioning for overall vacuum integrity, magnet systems functionality in terms of successful cool down to 4.5 K and charging up to 10 kA current was started from August 2012. Plasma operation of 100 kA current for more than 100 ms was also envisaged. It is comprised of vacuum vessel (VV) and cryostat (CST). Vacuum vessel, an ultra-high (UHV) vacuum chamber with net volume of 23 m{sup 3} was maintained at the base pressure of 6.3 × 10{sup −7} mbar for plasma confinement. Cryostat, a high-vacuum (HV) chamber with empty volume 39 m{sup 3} housing superconducting magnet system, bubble thermal shields and hydraulics for these circuits, maintained at 1.3 × 10{sup −5} mbar in order to provide suitable environment for these components. In order to achieve these ultimate vacuums, two numbers of turbo-molecular pumps (TMP) are installed in vacuum vessel while three numbers of turbo-molecular pumps are installed in cryostat. Initial pumping of both the chambers was carried out by using suitable Roots pumps. PXI based real time controlled system is used for remote operation of the complete pumping operation. In order to achieve UHV inside the vacuum vessel, it was baked at 150 °C for longer duration. Aluminum wire-seals were used for all non-circular demountable ports and a leak tightness < 1.0 × 10{sup −9} mbar l/s were achieved.

  3. MICROSTRUCTURE OF SUPERCONDUCTING MGB(2).

    Energy Technology Data Exchange (ETDEWEB)

    ZHU,Y.; LI,Q.; WU,L.; VOLKOV,V.; GU,G.; MOODENBAUGH,A.R.

    2001-07-12

    Recently, Akimitsu and co-workers [1] discovered superconductivity at 39 K in the intermetallic compound MgB{sub 2}. This discovery provides a new perspective on the mechanism for superconductivity. More specifically, it opens up possibilities for investigation of structure/properties in a new class of materials. With the exceptions of the cuprate and C{sub 60} families of compounds, MgB{sub 2} possesses the highest superconducting transition temperature T{sub c}. Its superconductivity appears to follow the BCS theory, apparently being mediated by electron-phonon coupling. The coherence length of MgB{sub 2} is reported to be longer than that of the cuprates [2]. In contrast to the cuprates, grain boundaries are strongly coupled and current density is determined by flux pinning [2,3]. Presently, samples of MgB{sub 2} commonly display inhomogeneity and porosity on the nanoscale, and are untextured. In spite of these obstacles, magnetization and transport measurements show that polycrystalline samples may carry large current densities circulating across many grains [3,4]. Very high values of critical current densities and critical fields have been recently observed in thin films [5,6]. These attributes suggest possible large scale and electronic applications. The underlying microstructure can be intriguing, both in terms of basic science and in applied areas. Subsequent to the discovery, many papers were published [1-13], most dealing with synthesis, physical properties, and theory. There have yet been few studies of microstructure and structural defects [11, 14]. A thorough understanding of practical superconducting properties can only be developed after an understanding of microstructure is gained. In this work we review transmission electron microscopy (TEM) studies of sintered MgB{sub 2} pellets [14]. Structural defects, including second phase particles, dislocations, stacking faults, and grain boundaries, are analyzed using electron diffraction, electron

  4. Creating nitrogen–vacancy ensembles in diamond for coupling with flux qubit

    International Nuclear Information System (INIS)

    Zheng Ya-Rui; Xing Jian; Chang Yan-Chun; Yan Zhi-Guang; Deng Hui; Wu Yu-Lin; Lü Li; Pan Xin-Yu; Zhu Xiao-Bo; Zheng Dong-Ning

    2017-01-01

    Hybrid quantum system of negatively charged nitrogen−vacancy (NV − ) centers in diamond and superconducting qubits provide the possibility to extend the performances of both systems. In this work, we numerically simulate the coupling strength between NV − ensembles and superconducting flux qubits and obtain a lower bound of 10 16 cm −3 for NV − concentration to achieve a sufficiently strong coupling of 10 MHz when the gap between NV-ensemble and flux qubit is 0. Moreover, we create NV − ensembles in different types of diamonds by 14 N + and 12 C + ion implantation, electron irradiation, and high temperature annealing. We obtain an NV − concentration of 1.05 × 10 16 cm −3 in the diamond with 1-ppm nitrogen impurity, which is expected to have a long coherence time for the low nitrogen impurity concentration. This shows a step toward performance improvement of flux qubit-NV − hybrid system. (paper)

  5. Flux expulsion and trapping in rotating discs of type II superconductors

    International Nuclear Information System (INIS)

    Boyer, R.; Leblanc, M.A.R.

    1977-01-01

    The magnetic flux rotating in step with a type II superconducting disc is measured with orthogonal pick up coils for various previous magnetic histories vs H 0 applied at right angles to the axis of rotation. For some initial magnetic states, flux expulsion, independent of the rate of rotation, occurs during the initial rotation. A simple model where flux lines leave the specimen against the magnetic pressure in the active region accounts for the observations. (author)

  6. Experimental Research of a Water-Source Heat Pump Water Heater System

    Directory of Open Access Journals (Sweden)

    Zhongchao Zhao

    2018-05-01

    Full Text Available The heat pump water heater (HPWH, as a portion of the eco-friendly technologies using renewable energy, has been applied for years in developed countries. Air-source heat pump water heaters and solar-assisted heat pump water heaters have been widely applied and have become more and more popular because of their comparatively higher energy efficiency and environmental protection. Besides use of the above resources, the heat pump water heater system can also adequately utilize an available water source. In order to study the thermal performance of the water-source heat pump water heater (WSHPWH system, an experimental prototype using the cyclic heating mode was established. The heating performance of the water-source heat pump water heater system, which was affected by the difference between evaporator water fluxes, was investigated. The water temperature unfavorably exceeded 55 °C when the experimental prototype was used for heating; otherwise, the compressor discharge pressure was close to the maximum discharge temperature, which resulted in system instability. The evaporator water flux allowed this system to function satisfactorily. It is necessary to reduce the exergy loss of the condenser to improve the energy utilization of the system.

  7. A study of an active magnetic shielding method for the superconductive Maglev vehicle

    International Nuclear Information System (INIS)

    Nemoto, K.; Komori, M.

    2010-01-01

    Various methods of magnetic shielding have been studied so far to reduce magnetic field strength inside the passenger room of the superconductive Maglev vehicle. Magnetic shielding methods with ferromagnetic materials are very useful, but they tend to be heavier for large space. Though some passive magnetic shielding methods using induced currents in superconducting bulks or superconducting coils have also been studied, the induced current is relatively small and it is difficult to get satisfactory magnetic shielding performance for the passenger room of the Maglev vehicle. Thus, we have proposed an active magnetic shielding method with some superconducting coils of the same length as propulsion-levitation-guidance superconducting coils of the Maglev vehicle. They are arranged under the passenger room of the Maglev vehicle. Then, we studied the shielding effect by canceling magnetic flux density in the passenger room by way of adjusting magnetomotive-forces of the magnetic shielding coils. As a result, it is found that a simple arrangement of two magnetic shielding coils for one propulsion-levitation-guidance superconducting coil on the vehicle shows an effective magnetic shielding.

  8. A study of an active magnetic shielding method for the superconductive Maglev vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Nemoto, K., E-mail: nemoto@kamakuranet.ne.j [Kyushu Institute of Technology, Dept. of Applied Science for Integrated System Engineering, 1-1 Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan); Komori, M. [Kyushu Institute of Technology, Dept. of Applied Science for Integrated System Engineering, 1-1 Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan)

    2010-11-01

    Various methods of magnetic shielding have been studied so far to reduce magnetic field strength inside the passenger room of the superconductive Maglev vehicle. Magnetic shielding methods with ferromagnetic materials are very useful, but they tend to be heavier for large space. Though some passive magnetic shielding methods using induced currents in superconducting bulks or superconducting coils have also been studied, the induced current is relatively small and it is difficult to get satisfactory magnetic shielding performance for the passenger room of the Maglev vehicle. Thus, we have proposed an active magnetic shielding method with some superconducting coils of the same length as propulsion-levitation-guidance superconducting coils of the Maglev vehicle. They are arranged under the passenger room of the Maglev vehicle. Then, we studied the shielding effect by canceling magnetic flux density in the passenger room by way of adjusting magnetomotive-forces of the magnetic shielding coils. As a result, it is found that a simple arrangement of two magnetic shielding coils for one propulsion-levitation-guidance superconducting coil on the vehicle shows an effective magnetic shielding.

  9. Making effective use of rod pumping systems in coalbed methane applications

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, A. [eProduction Solutions Inc., Kingwood, TX (United States)

    2003-07-01

    The advantages of optimizing coalbed methane (CBM) operations are increased production, reduced expenses, improved efficiency, and better inventory. The author discussed the CBM production cycle and the possible artificial lift options, including electric submersible pump (ESP), plunger lift, primary coolant pump (PCP), and reciprocating rod lift. The presentation focused on the rod lift, as it represents a low to moderate capital expenditure, has good system efficiency, an excellent fluid volume range, an excellent salvage value, excellent familiarity with equipment, and has readily available parts and service. The major disadvantage of the rod lift is that the fixed operating range does not adapt to changing reservoir characteristics. A comparison between the rod pump controller and the variable speed drive was presented. The well can be operated at or near the pumped off condition with variable speed drives with rod pumping intelligence. The author provided a closer examination of the variable frequency drive and the vector flux drive. The presentation also included a discussion of prime movers, drive and inclinometer, gearbox loading, rod load limiter, and dynamometer cards. Three case studies were presented: CSW1, CSW2, and CSW3. It was concluded that wells must be kept pumping, and that a Flux Vector Drive should be used along with an NEMA B motor and properly sized pumping unit and pump. tabs., figs.

  10. TNS superconducting ohmic-heating system

    International Nuclear Information System (INIS)

    Wang, S.T.; Fuja, R.; Kim, S.H.; Kustom, R.L.; Praeg, W.F.; Thompson, K.; Turner, L.R.

    1978-01-01

    The superconducting ohmic-heating (OH) system is the selected design for the General Atomics Co./Argonne National Laboratory TNS tokamak design studies. The key features of the OH system design are: (1) parallel coil connection, (2) better utilization of flux core by embedding support cylinder of the toroidal-field coil within the OH inner radius, (3) independent trim coils for correcting the stray fields, (4) low-loss high-current cryostable cable design and (5) OH coil cycling circuit using a reversing bridge. Detailed designs are presented

  11. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  12. Superconducting, magnetic and magnetotransport properties of FeTe1-xSex single crystals

    Science.gov (United States)

    Kumar, Rohit; Sudesh, Varma, G. D.

    2018-05-01

    The single crystalline samples with compositions FeTe1-xSex (0.25 ≤ x ≤ 0.50) have been prepared via self-flux method and the superconducting, magnetic and magnetotransport properties of the grown crystals were investigated. The superconducting onset temperatures have been determined from the measurements of zero field cooled magnetization and resistance with temperatures. In the present case, highest superconducting transition temperature TC (onset) ˜ 15 K has been obtained for x=0.5. The HC2 (T=0 K) values have been estimated by fitting the experimental HC2 - T plots with WHH model. The highest HC2(0) has been obtained for x=0.5. The activation energy of the thermally activated flux flow has been found from the broadening of superconducting transition in an applied magnetic field using the Arrhenius law. Our results show that the activation energy (U0) decreases with the increasing magnetic field. Furthermore, the magnetization measurements for x=0.4 and 0.5 samples have been performed at T=5 K in the magnetic field range ±7 T to estimate critical current density at different applied magnetic fields using Bean formula. We see that the sample x=0.5 has higher values of JC as compared to that of x=0.4 at all magnetic fields. This is in conformity with the behavior of U0-H plots.

  13. Flux tubes at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cea, Paolo [INFN, Sezione di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Dipartimento di Fisica dell’Università di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Cosmai, Leonardo [INFN, Sezione di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Cuteri, Francesca; Papa, Alessandro [Dipartimento di Fisica, Università della Calabria & INFN-Cosenza,Ponte Bucci, cubo 31C, I-87036 Rende (Cosenza) (Italy)

    2016-06-07

    The chromoelectric field generated by a static quark-antiquark pair, with its peculiar tube-like shape, can be nicely described, at zero temperature, within the dual superconductor scenario for the QCD confining vacuum. In this work we investigate, by lattice Monte Carlo simulations of the SU(3) pure gauge theory, the fate of chromoelectric flux tubes across the deconfinement transition. We find that, if the distance between the static sources is kept fixed at about 0.76 fm ≃1.6/√σ and the temperature is increased towards and above the deconfinement temperature T{sub c}, the amplitude of the field inside the flux tube gets smaller, while the shape of the flux tube does not vary appreciably across deconfinement. This scenario with flux-tube “evaporation” above T{sub c} has no correspondence in ordinary (type-II) superconductivity, where instead the transition to the phase with normal conductivity is characterized by a divergent fattening of flux tubes as the transition temperature is approached from below. We present also some evidence about the existence of flux-tube structures in the magnetic sector of the theory in the deconfined phase.

  14. A novel technology for control of variable speed pumped storage power plant

    Institute of Scientific and Technical Information of China (English)

    Seyed Mohammad Hassan Hosseini; Mohammad Reza Semsar

    2016-01-01

    Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control (DTFC) of a variable speed pumped storage power plant (VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP’s control strategies is studied. At the first, a wind turbine with the capacity 2.2 kW and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts (including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter (2LVSC) and three-level voltage source converter (3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion (THD) and ripple of rotor torque and flux.

  15. European roadmap on superconductive electronics - status and perspectives

    International Nuclear Information System (INIS)

    Anders, S.; Blamire, M.G.; Buchholz, F.-Im.; Crete, 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.

    2010-01-01

    Executive Summary: For four decades semiconductor electronics has followed Moore's law: with each generation of integration the circuit features became smaller, more complex and faster. This development is now reaching a wall so that smaller is no longer any faster. The clock rate has saturated at about 3-5 GHz and the parallel processor approach will soon reach its limit. The prime reason for the limitation the semiconductor electronics experiences is not the switching speed of the individual transistor, but its power dissipation and thus heat. Digital superconductive electronics is a circuit- and device-technology that is inherently faster at much less power dissipation than semiconductor electronics. It makes use of superconductors and Josephson junctions as circuit elements, which can provide extremely fast digital devices in a frequency range - dependent on the material - of hundreds of GHz: for example a flip-flop has been demonstrated that operated at 750 GHz. This digital technique is scalable and follows similar design rules as semiconductor devices. Its very low power dissipation of only 0.1 μW per gate at 100 GHz opens the possibility of three-dimensional integration. Circuits like microprocessors and analogue-to-digital converters for commercial and military applications have been demonstrated. In contrast to semiconductor circuits, the operation of superconducting circuits is based on naturally standardized digital pulses the area of which is exactly the flux quantum Φ 0 . The flux quantum is also the natural quantization unit for digital-to-analogue and analogue-to-digital converters. The latter application is so precise, that it is being used as voltage standard and that the physical unit 'Volt' is defined by means of this standard. Apart from its outstanding features for digital electronics, superconductive electronics provides also the most sensitive sensor for magnetic fields: the Superconducting Quantum Interference Device (SQUID). Amongst many

  16. Assessment of the impact of HTSCs on superconducting fault-current limiters

    International Nuclear Information System (INIS)

    Giese, R.F.; Runde, M.

    1992-01-01

    The possible impact of nitrogen-cooled superconductors on the design and cost of superconducting fault-current limiters is assessed by considering the technical specifications such devices must meet and by comparing material properties of 77-K and 4-K superconductors. The main advantage of operating superconducting at 77 K is that the refrigeration operating cost is reduced by a factor of up to 25, and the refrigeration capital cost is reduced by a factor of up to 10. The heat capacity at 77 K is several orders of magnitude larger than at 4 K. This phenomenon increases conductor stability against flux jumps but makes switching from the superconducting to normal state slow and difficult. Therefore, a high critical current density, probably at least 10 5 A/cm 2 , is required

  17. Collective-pinning properties of superconducting a-NbxGe and a-MoxSi films

    International Nuclear Information System (INIS)

    Woerdenweber, R.

    1987-01-01

    This thesis describes a study of superconducting flux pinning in amorphous NbGe and MoSi films of various compositions and thickness. Amorphous NbGe and MoSi alloys belong to the weak-coupling type-II superconductors in the extreme dirty limit. This feature enables to determine several important superconducting parameters from well-known theoretical expressions. It is also responsible for the weak pinning, which is necessary to observe the two-dimensional collective pinning properties according to the Larkin-Ovchinnikov theory. (Auth.)

  18. Optimum copper to superconductor ratio in cables for superconducting magnets at 1.9 K

    International Nuclear Information System (INIS)

    Wolf, R.

    1994-01-01

    In this paper the optimum copper to superconducting ratio is calculated to prevent quenching for superconducting cables used in accelerator magnets like the LHC dipoles, operating in superfluid helium at 1.9K. The duration of the perturbations leading to a quench are estimated from flux measurements made with pickup coils in the LHC dipole models. The optimum copper to superconducting ratio is then found by studying the minimum quench energy and the influence of the length and the duration or the perturbation and heat transfer to the surroundings. A comparison is made of the behavior at temperatures of 1.9 and 4.3 K

  19. Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory

    International Nuclear Information System (INIS)

    Chan, H.A.; Paik, H.J.

    1987-01-01

    Because of the equivalence principle, a global measurement is necessary to distinguish gravity from acceleration of the reference frame. A gravity gradiometer is therefore an essential instrument needed for precision tests of gravity laws and for applications in gravity survey and inertial navigation. Superconductivity and SQUID (superconducting quantum interference device) technology can be used to obtain a gravity gradiometer with very high sensitivity and stability. A superconducting gravity gradiometer has been developed for a null test of the gravitational inverse-square law and space-borne geodesy. Here we present a complete theoretical model of this instrument. Starting from dynamical equations for the device, we derive transfer functions, a common mode rejection characteristic, and an error model of the superconducting instrument. Since a gradiometer must detect a very weak differential gravity signal in the midst of large platform accelerations and other environmental disturbances, the scale factor and common mode rejection stability of the instrument are extremely important in addition to its immunity to temperature and electromagnetic fluctuations. We show how flux quantization, the Meissner effect, and properties of liquid helium can be utilized to meet these challenges

  20. Imaging phase slip dynamics in micron-size superconducting rings

    Science.gov (United States)

    Polshyn, Hryhoriy; Naibert, Tyler R.; Budakian, Raffi

    2018-05-01

    We present a scanning probe technique for measuring the dynamics of individual fluxoid transitions in multiply connected superconducting structures. In these measurements, a small magnetic particle attached to the tip of a silicon cantilever is scanned over a micron-size superconducting ring fabricated from a thin aluminum film. We find that near the superconducting transition temperature of the aluminum, the dissipation and frequency of the cantilever changes significantly at particular locations where the tip-induced magnetic flux penetrating the ring causes the two lowest-energy fluxoid states to become nearly degenerate. In this regime, we show that changes in the cantilever frequency and dissipation are well-described by a stochastic resonance (SR) process, wherein small oscillations of the cantilever in the presence of thermally activated phase slips (TAPS) in the ring give rise to a dynamical force that modifies the mechanical properties of the cantilever. Using the SR model, we calculate the average fluctuation rate of the TAPS as a function of temperature over a 32-dB range in frequency, and we compare it to the Langer-Ambegaokar-McCumber-Halperin theory for TAPS in one-dimensional superconducting structures.

  1. Role of α precipitates in flux pinning in a superconducting Ti-Nb-Ta-Zr quaternary alloy

    International Nuclear Information System (INIS)

    Osamura, K.; Tsunekawa, H.; Monju, Y.; Horiuchi, T.

    1984-01-01

    The precipitation behaviour of the α phase in a Ti-27 at.% Nb-6 at% Ta-6 at% Zr alloy has been investigated mainly by means of small-angle X-ray scattering measurements, by which the average size and number density of α precipitates were determined. The alloy was isothermally aged at 643 K after cold-rolling to various thicknesses. During ageing the average size of α precipitates increased but the number density decreased. The effect of cold-rolling was to increase the volume fraction of α precipitates. The superconducting critical current density was measured for the same specimens after the metallographical investigation. The specific pinning force produced by α precipitates, which corresponds to the global pinning force density divided by the number density of precipitates, was found to be proportional to the cube of the particle radius. It was found that the global pinning force density can be described using a scaling rule in terms of the volume fraction of α precipitates and the reduced magnetic field. The dominant global pinning force in the present foil specimens, as well as in commercial multifilamentary wires, is attributed to α precipitates. Dislocations and their secondary substructure introduced by cold-working also contributed to flux pinning, and could offer nucleation sites for the α phase. (author)

  2. Superconductivity: A testing ground for models of confinement

    International Nuclear Information System (INIS)

    Ball, J.S.; Caticha, A.

    1988-01-01

    The interaction of a magnetic monopole-antimonopole pair in a superconductor is calculated as a function of their separation and the value of the Landau-Ginzburg parameter. This direct numerical result is then compared to the bag approximation to the same interaction in a superconducting medium. The actual potential exhibits the same general features as those obtained in the bag calculation. If the bag pressure is used as a phenomenological parameter, rather than the value fixed by the superconducting energy density, the agreement is excellent. Numerically the actual problem was actually no more difficult than the bag calculation. The interaction between magnetic monopoles and antimonopoles in the superconducting vacuum state is similar to the interaction of heavy colored quarks in a flux-confining physical QCD vacuum state. This means that our results are probably a good indication of the general behavior of the QCD potential and of the reliability of the bag approximation in the calculation of this potential. Our results also show that the bag model is a good approximation to a dual superconductor. This indicates that a dual superconducting picture of QCD would lead to the same heavy-quark potential and perhaps retain more of the physics than the bag model

  3. Superconductivity

    International Nuclear Information System (INIS)

    Taylor, A.W.B.; Noakes, G.R.

    1981-01-01

    This book is an elementray introduction into superconductivity. The topics are the superconducting state, the magnetic properties of superconductors, type I superconductors, type II superconductors and a chapter on the superconductivity theory. (WL)

  4. Overview of the superconducting undulator development program at ANKA

    Energy Technology Data Exchange (ETDEWEB)

    Casalbuoni, S., E-mail: sara.casalbuoni@kit.edu; Cecilia, A.; Gerstl, S.; Glamann, N.; Grau, A.; Holubek, T.; Meuter, C.; Saez de Jauregui, D.; Voutta, R. [ANKA, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Boffo, C.; Gerhard, Th.; Turenne, M.; Walter, W. [Babcock Noell GmbH, Alfred Nobel Str. 20, 97080 Würzburg (Germany)

    2016-07-27

    Superconducting undulators (SCUs) have the potential to reach higher brilliance and flux with respect to the state of the art permanent magnet insertion devices. ANKA is collaborating with the industrial partner Babcock Noell GmbH (BNG) to realize NbTi conduction cooled planar devices for low emittance light sources, and is developing the instrumentation to characterize the magnetic field properties and to measure the beam heat load to a cold bore needed for the cryogenic design of SCUs. We present here: the most recent results obtained within the ANKA-BNG collaboration, the progress achieved in the development of the instrumentation, and the in house studies on the application of high temperature superconducting (HTS) tape to the SCU technology.

  5. Superconductivity

    International Nuclear Information System (INIS)

    Onnes, H.K.

    1988-01-01

    The author traces the development of superconductivity from 1911 to 1986. Some of the areas he explores are the Meissner Effect, theoretical developments, experimental developments, engineering achievements, research in superconducting magnets, and research in superconducting electronics. The article also mentions applications shown to be technically feasible, but not yet commercialized. High-temperature superconductivity may provide enough leverage to bring these applications to the marketplace

  6. A SUPER-CONDUCTING LINAC DRIVER FOR THE HFBR.

    Energy Technology Data Exchange (ETDEWEB)

    Alessi, J.; Raparia, D.; Ruggiero, A.G.

    2000-08-21

    This paper reports on the feasibility study of a proton Super-Conducting Linac (SCL) as a driver for the High-Flux Breeder Reactor (HFBR) at Brookhaven National Laboratory (BNL). The Linac operates in Continuous Wave (CW) mode to produce an average 10 MW of beam power. The Linac beam energy is 1.0 GeV. The average proton beam intensity in exit is 10 mA.

  7. Modeling of the free space and focused magnetic field profiles of the ORNL superconducting motor

    International Nuclear Information System (INIS)

    Bailey, J.M.; Rader, M.; Sohns, C.W.; McKeever, J.; Schwenterly, S.W.

    1992-01-01

    The ORNL superconducting motor, is a device consisting of 4 DC superconducting magnets in a square cross section. These coils are arranged in a N-S-N-S configuration and at present have no iron flux return paths. Experimentally the device has been operated and has been shown to produce 102.3 kg-m of locked rotor torque at 100 Ampers winding current. The superconductors were operating at 40 Kelvin. The peak magnetic field at 2,100 amperes operating current was 2 Tesla on the cryostat face. Recently there has been an effort under way to improve the operating parameters of the device by improving the flux utilization of the device. This was to be accomplished by the use of flux focusing pole pieces. The effects of the pole pieces and the vacuum magnetic field have been modeled with the MSC EMAS code to see the possible benefit of adding pole pieces to the in situ experiment

  8. The spheromak as a prototype for ultra-high-field superconducting magnets

    International Nuclear Information System (INIS)

    Furth, H.P.; Jardin, S.C.

    1987-08-01

    In view of current progress in the development of superconductor materials, the ultimate high-field limit of superconducting magnets is likely to be set by mechanical stress problems. Maximum field strength should be attainable by means of approximately force-free magnet windings having favorable ''MHD'' stability properties (so that small winding errors will not grow). Since a low-beta finite-flux-hole spheromak configuration qualifies as a suitable prototype, the theoretical and experimental spheromak research effort of the past decade has served to create a substantial technical basis for the design of ultra-high-field superconducting coils. 11 refs

  9. Superconductivity

    International Nuclear Information System (INIS)

    Andersen, N.H.; Mortensen, K.

    1988-12-01

    This report contains lecture notes of the basic lectures presented at the 1st Topsoee Summer School on Superconductivity held at Risoe National Laboratory, June 20-24, 1988. The following lecture notes are included: L.M. Falicov: 'Superconductivity: Phenomenology', A. Bohr and O. Ulfbeck: 'Quantal structure of superconductivity. Gauge angle', G. Aeppli: 'Muons, neutrons and superconductivity', N.F. Pedersen: 'The Josephson junction', C. Michel: 'Physicochemistry of high-T c superconductors', C. Laverick and J.K. Hulm: 'Manufacturing and application of superconducting wires', J. Clarke: 'SQUID concepts and systems'. (orig.) With 10 tabs., 128 figs., 219 refs

  10. Ferromagnetic Film on a Superconducting Substrate

    OpenAIRE

    Bulaevskii, L. N.; Chudnovsky, E. M.

    2000-01-01

    We study the equilibrium domain structure and magnetic flux around a ferromagnetic (FM) film with perpendicular magnetization M_0 on a superconducting (SC) substrate. At 4{\\pi}M_0> 1. Here \\lambda_L is the London penetration length. For 4{\\pi}M_0 > H_{c1} and l_{N} in excess of about 35 {\\lambda}_{L}, the domains are connected by SC vortices. We argue that pinning of vortices by magnetic domains in FM/SC multilayers can provide high critical currents.

  11. Theory of superconductivity

    International Nuclear Information System (INIS)

    Crisan, M.

    1988-01-01

    This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up to the 1987 results on high temperature superconductivity. Contents: Phenomenological Theory of Superconductivity; Microscopic Theory of Superconductivity; Theory of Superconducting Alloys; Superconductors in a Magnetic Field; Superconductivity and Magnetic Order; Superconductivity in Quasi-One-Dimensional Systems; and Non-Conventional Superconductivity

  12. Applied superconductivity

    CERN Document Server

    Newhouse, Vernon L

    1975-01-01

    Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec

  13. Cryogenic testing of the TPC superconducting solenoid

    International Nuclear Information System (INIS)

    Green, M.A.; Smits, R.G.; Taylor, J.D.

    1983-06-01

    This report describes the results of a series of tests on the TPC superconducting magnet cryogenic system which occurred during the winter and spring of 1983. The tests occurred at interaction region 2 of the PEP colliding beam facility at the Stanford Linear Accelerator Center (SLAC). The TPC Magnet Cryogenic System which was tested includes the following major components: a remote helium compressor with a full flow liquid nitrogen purification station, 400 meters of high pressure supply and low pressure return lines; and locally a CTi Model 2800 refrigerator with two Sulzer gas bearing turbines, the TPC magnet control dewar, 70 meters of transfer lines, and the TPC thin superconducting solenoid magnet. In addition, there is a conditioner (liquid nitrogen heat exchangers and gas heaters) system for cooldown and warmup of the magnet. This report describes the local cryogenic system and describes the various steps in the cooldown and operation of the TPC magnet. The tests were successful in that they showed that the TPC magnet could be cooled down in 24 hours and the magnet could be operated on the refrigerator or a helium pump with adequate cooling margin. The tests identified problems with the cryogenic system and the 2800 refrigerator. Procedures for successful operation and quenching of the superconducting magnet were developed. 19 references

  14. Study of the Relap5/mod3.2 wall heat flux partitioning model

    International Nuclear Information System (INIS)

    Hari, S.; Hassan, Y.A.

    2001-01-01

    The performance of the subcooled boiling model adapted in RELAP5/MOD3.2 computer code has been assessed in detail for low-pressure conditions and it has been found that the void fraction profile is under-predicted. In general, any subcooled boiling model is composed of individual sub-models that account for the different physical mechanism that govern the overall process, as the wall vapor generation, interfacial shear and condensation etc. The wall heat flux partitioning model is one of the important sub-models that is a constituent of any subcooled boiling model. The function of this model is to apportion the wall heat flux to the different components (as the single/two phase fluid or bubble), as the case may be, in a two-phase flow-boiling scenario adjacent to a heated wall. The ''pumping factor'' approach is generally followed by most of the wall heat flux partitioning models, for partitioning the wall heat flux. In this work, the wall heat flux partitioning model of RELAP5/MOD3.2 computer code is studied; in particular, the ''pumping factor'' formulation in the present code version is assessed for its performance under low-pressure conditions. In addition, three different ''pumping factor'' formulations available in the literature have been introduced into the RELAP5/MOD3.2 code. Simulations of two low-pressure subcooled flow boiling experiments were performed with the refined code versions to determine the appropriate pumping factor to be used under these conditions. (author)

  15. Flux pinning by voids in surface-oxidized superconducting niobium and vanadium

    International Nuclear Information System (INIS)

    Meij, G.P. van der.

    1984-03-01

    The volume pinning force in several niobium and vanadium samples with voids is determined at various temperatures. Reasonable agreement is found with the collective pinning theory of Larkin and Ovchinnikov above the field of maximum pinning, if the flux line lattice is assumed to be amorphous in this region and if the elementary pinning force is calculated from the quasi-classical theory of Thuneberg, Kurkijaervi, and Rainer. Also some history and relaxation effects are studied in an alternating field. A qualitative explanation is given in terms of flux line dislocations, which reduce the shear strength of the flux line lattice. (Auth.)

  16. Design of a gap tunable flux qubit with FastHenry

    Science.gov (United States)

    Akhtar, Naheed; Zheng, Yarui; Nazir, Mudassar; Wu, Yulin; Deng, Hui; Zheng, Dongning; Zhu, Xiaobo

    2016-12-01

    In the preparations of superconducting qubits, circuit design is a vital process because the parameters and layout of the circuit not only determine the way we address the qubits, but also strongly affect the qubit coherence properties. One of the most important circuit parameters, which needs to be carefully designed, is the mutual inductance among different parts of a superconducting circuit. In this paper we demonstrate how to design a gap-tunable flux qubit by layout design and inductance extraction using a fast field solver FastHenry. The energy spectrum of the gap-tunable flux qubit shows that the measured parameters are close to the design values. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374344, 11404386, and 91321208), the National Basic Research Program of China (Grant No. 2014CB921401), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07010300).

  17. Superconducting permanent magnets

    International Nuclear Information System (INIS)

    Wipf, S.L.; Laquer, H.L.

    1989-01-01

    The concept of superconducting permanent magnets with fields trapped in shells or cylinders of Type II superconductors is an old one. Unfortunately, the low values of 0.5 to 1T for the first flux jump field, which is independent of the actual current density, have frustrated its implementation with classical Type II superconductors. The fact that the flux jump fields for high temperature superconductors should be an order of magnitude larger at liquid nitrogen temperatures allows us to reconsider these options. Analysis of the hysteresis patterns, based on the critical state model, shows that, if the dimensions are chosen so that the sample is penetrated at a field B/sub p/, which is equal to or just less than the first flux jump field, B/sub fj/, a temporarily applied field of 2B/sub fj/ will trap 0.5 B/sub fj/. Thus for a 90 K superconductor with a B/sub fj/ of 6T, a permanent field of 3 T should be trapped, with an energy product of 1.8 MJ/m/sup 3/ (225 MG . Oe). This is five times as large as for the best permanent magnet materials. The authors discuss means to verify the analysis and the limitations imposed by the low critical current densities in presently available high temperature superconductors

  18. Superconductivity

    International Nuclear Information System (INIS)

    Caruana, C.M.

    1988-01-01

    Despite reports of new, high-temperature superconductive materials almost every day, participants at the First Congress on Superconductivity do not anticipate commercial applications with these materials soon. What many do envision is the discovery of superconducting materials that can function at much warmer, perhaps even room temperatures. Others hope superconductivity will usher in a new age of technology as semiconductors and transistors did. This article reviews what the speakers had to say at the four-day congress held in Houston last February. Several speakers voiced concern that the Reagan administration's apparent lack of interest in funding superconductivity research while other countries, notably Japan, continue to pour money into research and development could hamper America's international competitiveness

  19. Pulsed energy conversion with a dc superconducting magnet

    International Nuclear Information System (INIS)

    Cowan, M.; Cnare, E.C.; Leisher, W.B.; Tucker, W.K.; Wessenberg, D.L.

    1976-01-01

    A generator system for pulsed power is described which employs a dc superconducting magnet in a magnetic flux compression scheme. Experience with a small-scale generator together with projections of numerical models indicate potential applications to fusion research and commercial power generation. When the system is large enough pulse energy can exceed that stored in the magnet and pulse rise time can range from several microseconds to tens of milliseconds. (author)

  20. The g-2 storage ring superconducting magnet system

    International Nuclear Information System (INIS)

    Green, M.A.

    1993-09-01

    The g-2 μ lepton (muon) storage ring is a single dipole magnet that is 44 meters in circumference. The storage ring dipole field is created by three large superconducting solenoid coils. A single outer solenoid, 15.1 meters in diameter, carries 254 kA. Two inner solenoids, 13.4 meters in diameter, carry 127 kA each in opposition to the current carried by the outer solenoid. A room temperature C shaped iron yoke returns the magnetic flux and shapes the magnetic field in a 180 mm gap where the stored muon beam circulates. The gap induction will be 1.47 T. This report describes the three large superconducting solenoids, the cryogenic system needed to keep them cold, the solenoid power supply and the magnet quench protection system

  1. Application of a modified flux-coupling type superconducting fault current limiter to transient performance enhancement of micro-grid

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lei, E-mail: stclchen1982@163.com [School of Electrical Engineering, Wuhan University, Wuhan 430072 (China); Zheng, Feng; Deng, Changhong; Li, Shichun; Li, Miao; Liu, Hui [School of Electrical Engineering, Wuhan University, Wuhan 430072 (China); Zhu, Lin [Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville 37996 (United States); Guo, Fang [Department of Substation, Guang Dong Electric Power Design Institute, Guangzhou 510663 (China)

    2015-11-15

    Highlights: • A modified flux-coupling type SFCL is suggested to enhance the transient performance of a micro-grid. • The SFCL’s main contribution is to improve the micro-grid’s fault ride-through capability. • The SFCL also can make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. • The simulations show that the SFCL can availably strengthen the micro-grid’s voltage and frequency stability. - Abstract: Concerning the application and development of a micro-grid system which is designed to accommodate high penetration of intermittent renewable resources, one of the main issues is related to an increase in the fault-current level. It is crucial to ensure the micro-grid’s operational stability and service reliability when a fault occurs in the main network. In this paper, our research group suggests a modified flux-coupling type superconducting fault current limiter (SFCL) to enhance the transient performance of a typical micro-grid system. The SFCL is installed at the point of common coupling (PCC) between the main network and the micro-grid, and it is expected to actively improve the micro-grid’s fault ride-through capability. And for some specific faults, the micro-grid should disconnect from the main network, and the SFCL’s contribution is to make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. Related theory derivation, technical discussion and simulation analysis are performed. From the demonstrated results, applying the SFCL can effectively limit the fault current, maintain the power balance, and enhance the voltage and frequency stability of the micro-grid.

  2. Application of a modified flux-coupling type superconducting fault current limiter to transient performance enhancement of micro-grid

    International Nuclear Information System (INIS)

    Chen, Lei; Zheng, Feng; Deng, Changhong; Li, Shichun; Li, Miao; Liu, Hui; Zhu, Lin; Guo, Fang

    2015-01-01

    Highlights: • A modified flux-coupling type SFCL is suggested to enhance the transient performance of a micro-grid. • The SFCL’s main contribution is to improve the micro-grid’s fault ride-through capability. • The SFCL also can make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. • The simulations show that the SFCL can availably strengthen the micro-grid’s voltage and frequency stability. - Abstract: Concerning the application and development of a micro-grid system which is designed to accommodate high penetration of intermittent renewable resources, one of the main issues is related to an increase in the fault-current level. It is crucial to ensure the micro-grid’s operational stability and service reliability when a fault occurs in the main network. In this paper, our research group suggests a modified flux-coupling type superconducting fault current limiter (SFCL) to enhance the transient performance of a typical micro-grid system. The SFCL is installed at the point of common coupling (PCC) between the main network and the micro-grid, and it is expected to actively improve the micro-grid’s fault ride-through capability. And for some specific faults, the micro-grid should disconnect from the main network, and the SFCL’s contribution is to make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. Related theory derivation, technical discussion and simulation analysis are performed. From the demonstrated results, applying the SFCL can effectively limit the fault current, maintain the power balance, and enhance the voltage and frequency stability of the micro-grid.

  3. Ferromagnetic film on a superconducting substrate

    International Nuclear Information System (INIS)

    Bulaevskii, L. N.; Chudnovsky, E. M.

    2001-01-01

    We study the equilibrium domain structure and magnetic flux around a ferromagnetic film with perpendicular magnetization M 0 on a superconducting (SC) substrate. At 4πM 0 c1 the SC is in the Meissner state and the equilibrium domain width in the film, l, scales as (l/4πλ L )=(l N /4πλ L ) 2/3 with the domain width on a normal (nonsuperconducting) substrate, l N /4πλ L >>1; λ L being the London penetration length

  4. Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation

    Science.gov (United States)

    Sung, Z.-H.; Wang, M.; Polyanskii, A. A.; Santosh, C.; Balachandran, S.; Compton, C.; Larbalestier, D. C.; Bieler, T. R.; Lee, P. J.

    2017-05-01

    This study shows that low angle grain boundaries (LAGBs) can be created by small 5% strains in high purity (residual resistivity ratio ≥ 200) superconducting radio frequency (SRF)-grade single crystalline niobium (Nb) and that these boundaries act as hydrogen traps as indicated by the distribution of niobium hydrides (Nb1-xHx). Nb1-xHx is detrimental to SRF Nb cavities due to its normal conducting properties at cavity operating temperatures. By designing a single crystal tensile sample extracted from a large grain (>5 cm) Nb ingot slice for preferred slip on one slip plane, LAGBs and dense dislocation boundaries developed. With chemical surface treatments following standard SRF cavity fabrication practice, Nb1-xHx phases were densely precipitated at the LAGBs upon cryogenic cooling (8-10 K/min). Micro-crystallographic analysis confirmed heterogeneous hydride precipitation, which included significant hydrogen atom accumulation in LAGBs. Magneto-optical imaging analysis showed that these sites can then act as sites for both premature flux penetration and eventually flux trapping. However, this hydrogen related degradation at LAGBs did not completely disappear even after an 800 °C/2 h anneal typically used for hydrogen removal in SRF Nb cavities. These findings suggest that hydride precipitation at an LAGB is facilitated by a non-equilibrium concentration of vacancy-hydrogen (H) complexes aided by mechanical deformation and the hydride phase interferes with the recovery process under 800 °C annealing.

  5. Replumbing of the Biological Pump caused by Millennial Climate Variability

    Science.gov (United States)

    Galbraith, E.; Sarmiento, J.

    2008-12-01

    It has been hypothesized that millennial-timescale variability in the biological pump was a critical instigator of glacial-interglacial cycles. However, even in the absence of changes in ecosystem function (e.g. due to iron fertilization), determining the mechanisms by which physical climate variability alters the biological pump is not simple. Changes in upper ocean circulation and deep water formation have previously been shown to alter both the downward flux of organic matter and the mass of respired carbon in the ocean interior, often in non- intuitive ways. For example, a reduced upward flux of nutrients at the global scale will decrease the global rate of export production, but it could either increase or decrease the respired carbon content of the ocean interior, depending on where the reduced upward flux of nutrients occurs. Furthermore, viable candidates for physical climate forcing are numerous, including changes in the westerly winds, changes in the depth of the thermocline, and changes in the formation rate of North Atlantic Deep Water, among others. We use a simple, prognostic, light-and temperature-dependent model of biogeochemical cycling within a state-of-the- art global coupled ocean-atmosphere model to examine the response of the biological pump to changes in the coupled Earth system over multiple centuries. The biogeochemical model explicitly distinguishes respired carbon from preformed and saturation carbon, allowing the activity of the biological pump to be clearly quantified. Changes are forced in the model by altering the background climate state, and by manipulating the flux of freshwater to the North Atlantic region. We show how these changes in the physical state of the coupled ocean-atmosphere system impact the distribution and mass of respired carbon in the ocean interior, and the relationship these changes bear to global patterns of export production via the redistribution of nutrients.

  6. 3D Magnetic field modeling of a new superconducting synchronous machine using reluctance network method

    Science.gov (United States)

    Kelouaz, Moussa; Ouazir, Youcef; Hadjout, Larbi; Mezani, Smail; Lubin, Thiery; Berger, Kévin; Lévêque, Jean

    2018-05-01

    In this paper a new superconducting inductor topology intended for synchronous machine is presented. The studied machine has a standard 3-phase armature and a new kind of 2-poles inductor (claw-pole structure) excited by two coaxial superconducting coils. The air-gap spatial variation of the radial flux density is obtained by inserting a superconducting bulk, which deviates the magnetic field due to the coils. The complex geometry of this inductor usually needs 3D finite elements (FEM) for its analysis. However, to avoid a long computational time inherent to 3D FEM, we propose in this work an alternative modeling, which uses a 3D meshed reluctance network. The results obtained with the developed model are compared to 3D FEM computations as well as to measurements carried out on a laboratory prototype. Finally, a 3D FEM study of the shielding properties of the superconducting screen demonstrates the suitability of using a diamagnetic-like model of the superconducting screen.

  7. Voltage spike detection in high field superconducting accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Orris, D.F.; Carcagno, R.; Feher, S.; Makulski, A.; Pischalnikov, Y.M.; /Fermilab

    2004-12-01

    A measurement system for the detection of small magnetic flux changes in superconducting magnets, which are due to either mechanical motion of the conductor or flux jump, has been developed at Fermilab. These flux changes are detected as small amplitude, short duration voltage spikes, which are {approx}15mV in magnitude and lasts for {approx}30 {micro}sec. The detection system combines an analog circuit for the signal conditioning of two coil segments and a fast data acquisition system for digitizing the results, performing threshold detection, and storing the resultant data. The design of the spike detection system along with the modeling results and noise analysis will be presented. Data from tests of high field Nb{sub 3}Sn magnets at currents up to {approx}20KA will also be shown.

  8. Voltage spike detection in high field superconducting accelerator magnets

    International Nuclear Information System (INIS)

    Orris, D.F.; Carcagno, R.; Feher, S.; Makulski, A.; Pischalnikov, Y.M.

    2004-01-01

    A measurement system for the detection of small magnetic flux changes in superconducting magnets, which are due to either mechanical motion of the conductor or flux jump, has been developed at Fermilab. These flux changes are detected as small amplitude, short duration voltage spikes, which are ∼15mV in magnitude and lasts for ∼30(micro)sec. The detection system combines an analog circuit for the signal conditioning of two coil segments and a fast data acquisition system for digitizing the results, performing threshold detection, and storing the resultant data. The design of the spike detection system along with the modeling results and noise analysis will be presented. Data from tests of high field Nb3Sn magnets at currents up to ∼20KA will also be shown

  9. Time variations of fields in superconducting magnets and their effects on accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Herrup, D.A.; Syphers, M.J.; Johnson, D.E.; Johnson, R.P.; Tollestrup, A.V.; Hanft, R.W.; Brown, B.C.; Lamm, M.J.; Kuchnir, M.; McInturff, A.D.

    1988-08-22

    A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs.

  10. Time variations of fields in superconducting magnets and their effects on accelerators

    International Nuclear Information System (INIS)

    Herrup, D.A.; Syphers, M.J.; Johnson, D.E.

    1988-01-01

    A report on the time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron has been published. A field variation of order 1 gauss at the aperture radius is observed. Studies on both full sized Tevatron, dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on new laboratory tests and the latest accelerator operation are presented. 9 refs., 4 figs

  11. Signatures of topological phase transitions in mesoscopic superconducting rings

    International Nuclear Information System (INIS)

    Pientka, Falko; Romito, Alessandro; Duckheim, Mathias; Oppen, Felix von; Oreg, Yuval

    2013-01-01

    We investigate Josephson currents in mesoscopic rings with a weak link which are in or near a topological superconducting phase. As a paradigmatic example, we consider the Kitaev model of a spinless p-wave superconductor in one dimension, emphasizing how this model emerges from more realistic settings based on semiconductor nanowires. We show that the flux periodicity of the Josephson current provides signatures of the topological phase transition and the emergence of Majorana fermions (MF) situated on both sides of the weak link even when fermion parity is not a good quantum number. In large rings, the MF hybridize only across the weak link. In this case, the Josephson current is h/e periodic in the flux threading the loop when fermion parity is a good quantum number but reverts to the more conventional h/2e periodicity in the presence of fermion-parity changing relaxation processes. In mesoscopic rings, the MF also hybridize through their overlap in the interior of the superconducting ring. We find that in the topological superconducting phase, this gives rise to an h/e-periodic contribution even when fermion parity is not conserved and that this contribution exhibits a peak near the topological phase transition. This signature of the topological phase transition is robust to the effects of disorder. As a byproduct, we find that close to the topological phase transition, disorder drives the system deeper into the topological phase. This is in stark contrast to the known behavior far from the phase transition, where disorder tends to suppress the topological phase. (paper)

  12. Solutions stability of one-dimensional parametric superconducting magnetic levitation model analysis by the first approximation

    International Nuclear Information System (INIS)

    Shvets', D.V.

    2009-01-01

    By the first approximation analyzing stability conditions of unperturbed solution of one-dimensional dynamic model with magnetic interaction between two superconducting rings obtained. The stability region in the frozen magnetic flux parameters space was constructed.

  13. Superconducting Sweet-Spot in Microcrystalline Graphite Revealed by Point-Contact Spectroscopy

    Science.gov (United States)

    Arnold, F.; Nyéki, J.; Saunders, J.

    2018-05-01

    In this letter we describe the observation of a magnetic field dependent electronic gap, suggestive of local superconductivity, in the point-contact spectrum of micro-crystalline graphite. Magnetic field dependent point-contact spectroscopy was carried out at a temperature of 1.8K using an etched aluminium tip. At zero field a gap structure in the differential conductance is observed, showing a gap of Δ = 4.2 meV. On applying magnetic fields of up to 500mT, this gap gradually closes, following the theoretical prediction by Ginzburg and Landau for a fully flux-penetrated superconductor. By applying BCS-theory, we infer a critical superconducting temperature of 14K.

  14. 3D-computation of a thermal process in a superconducting coil

    International Nuclear Information System (INIS)

    Netter, D.; Leveque, J.; Rezzoug, A.; Caron, J.P.; Sargos, F.M.

    1995-01-01

    This study deals with the resistive zone propagation in a superconducting coil during a quench, taking into account both the flux density distribution and the anisotropy of the thermal parameters. A Finite Difference Method is used to solve the heat diffusion equation and the flux density is calculated by means of a semi-analytical method. The 3-D model is suitable to describe the quench of thick coils and it can be applied to the study of thermal stability. As an application, a 10 kJ-solenoid is studied

  15. Experimental study on performance of pulsed liquid jet pump

    International Nuclear Information System (INIS)

    Xu Weihui; Gao Chuanchang; Qin Haixia

    2010-01-01

    The device performance characteristics of transformer type pulsed liquid pump device were experimentally studied. The effects of the area ratio, work pressure and pulse parameters on the performance of the pulsed liquid jet pump device were performed in the tests. The potency of pulsed jet on improving the performance of the liquid jet pump device was also studied through the comparison with invariable jet pump at the same conditions. The results show that the pulsed jet can significantly improve the performance of transformer type jet pump devices. Area ratio and pulse parameters are the critical factors to the performance of the pulsed liquid jet pump device. The jet pump device performances are significantly improved by reducing the area ratio or by increasing the pulsed frequency. The flux characteristics of the pulsed liquid jet pump device presents the typical negative linear,the potency of pulsed jet in improving the performance of jet pump device with small area ratio can be more significant. The efficiency curve of pulsed liquid jet pump is similar to the parabola. At higher pulsed frequency, the top efficiency point of the pulsed jet pump moves to the higher flow ratio. The high efficiency area of the pulsed jet pump also is widened with the increase of the pulsed frequency. (authors)

  16. Advances in the measurement of weak magnetic fields

    International Nuclear Information System (INIS)

    Li Damin; Huang Minzhe.

    1992-01-01

    The state-of-art and general features of instruments for measuring weak magnetic fields (such as the non-directional magnetometer, induced coil magnetometer, proton magnetometer, optical pumping magnetometer, flux-gate magnetometer and superconducting quantum magnetometer) are briefly described. Emphasis is laid on the development of a novel technique used in the flux-gate magnetometer and the liquid nitrogen SQUID. Typical applications of the measuring techniques for weak magnetic fields are given

  17. Quantification of the lithogenic carbon pump following a dust deposition event

    Science.gov (United States)

    Bressac, M.; Guieu, C.; Doxaran, D.; Bourrin, F.; Desboeufs, K.; Leblond, N.; Ridame, C.

    2013-08-01

    Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to affine the "ballast hypothesis". In the framework of the DUNE project, two artificial seedings were performed seven days apart within large mesocosms. A suite of optical and biogeochemical measurements were used to quantify surface POC export following simulated dust events within a low-nutrient low-chlorophyll ecosystem. The two successive seedings led to a 2.3-6.7 fold higher POC flux as compared to the POC flux observed in controlled mesocosms. A simple linear regression analysis revealed that the lithogenic fluxes explained more than 85% of the variance in POC fluxes. At the scale of a dust deposition event, we estimated that 42-50% of POC fluxes were strictly associated with lithogenic particles through an aggregation process. Lithogenic ballasting also likely impacted the remaining POC fraction which resulted from the fertilization effect. The observations support the "ballast hypothesis" and provide a quantitative estimation of the surface POC export abiotically triggered by dust deposition. In this work, we demonstrate that the strength of such a "lithogenic carbon pump" depends on the biogeochemical conditions of the water column at the time of deposition. Based on these observations, we suggest that this "lithogenic carbon pump" could represent a major component of the biological pump in oceanic areas subjected to intense atmospheric forcing.

  18. Thermal coupling effect on the vortex dynamics of superconducting thin films: time-dependent Ginzburg–Landau simulations

    Science.gov (United States)

    Jing, Ze; Yong, Huadong; Zhou, Youhe

    2018-05-01

    In this paper, vortex dynamics of superconducting thin films are numerically investigated by the generalized time-dependent Ginzburg–Landau (TDGL) theory. Interactions between vortex motion and the motion induced energy dissipation is considered by solving the coupled TDGL equation and the heat diffusion equation. It is found that thermal coupling has significant effects on the vortex dynamics of superconducting thin films. Branching in the vortex penetration path originates from the coupling between vortex motion and the motion induced energy dissipation. In addition, the environment temperature, the magnetic field ramp rate and the geometry of the superconducting film also greatly influence the vortex dynamic behaviors. Our results provide new insights into the dynamics of superconducting vortices, and give a mesoscopic understanding on the channeling and branching of vortex penetration paths during flux avalanches.

  19. Observation of distinct, temperature dependent flux noise near bicrystal grain boundaries in YBa2Cu3O7-x films

    DEFF Research Database (Denmark)

    Bukh, K. R.; Jacobsen, Claus Schelde; Hansen, Jørn Bindslev

    2000-01-01

    The characteristics of the magnetic flux noise in high temperature superconducting thin-films of yttrium-barium-copper-oxide (YBa2Cu3O7) in the vicinity of artificial grain boundaries have been studied by means of a low critical temperature superconducting quantum interference device (SQUID...

  20. Flux qubit to a transmission line

    Energy Technology Data Exchange (ETDEWEB)

    Haeberlein, Max; Baust, Alexander; Zhong, Ling; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany); Anderson, Gustav; Wang, Lujun; Eder, Peter; Fischer, Michael; Goetz, Jan; Xie, Edwar; Schwarz, Manuel; Wulschner, Karl Friedrich; Deppe, Frank; Fedorov, Kirill; Huebl, Hans; Menzel, Edwin [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany)

    2015-07-01

    Within the last decade, superconducting qubits coupled to microwave resonators have been extensively studied within the framework of quantum electrodynamics. Ultimately, quantum computing seems within reach in such architectures. However, error correction schemes are necessary to achieve the required fidelity in multi-qubit operations, drastically increasing the number of qubits involved. In this work, we couple a flux qubit to a transmission line where it interacts with itinerant microwave photons granting access to all-optical quantum computing. In this approach, travelling photons generate entanglement between two waveguides, containing the qubit information. In this presentation, we show experimental data on flux qubits coupled to transmission lines. Furthermore, we will discuss entanglement generation between two separate paths.

  1. Radiation-effects limits on copper in superconducting magnets

    Energy Technology Data Exchange (ETDEWEB)

    Guinan, M.W.

    1983-05-25

    The determination of the response of copper stabilizers to neutron irradiation in fusion-reactor superconducting magnets requires information in four areas: (1) neutron flux and spectrum determination, (2) resistivity changes at zero field, (3) resistivity changes at field, and (4) the cyclic irradiation and annealing. Applications of our current understanding of the limits of copper stabilizers in fusion-reactor designs are explored in two examples. Recommendations for future additions to the data base are discussed.

  2. Radiation-effects limits on copper in superconducting magnets

    International Nuclear Information System (INIS)

    Guinan, M.W.

    1983-01-01

    The determination of the response of copper stabilizers to neutron irradiation in fusion-reactor superconducting magnets requires information in four areas: (1) neutron flux and spectrum determination, (2) resistivity changes at zero field, (3) resistivity changes at field, and (4) the cyclic irradiation and annealing. Applications of our current understanding of the limits of copper stabilizers in fusion-reactor designs are explored in two examples. Recommendations for future additions to the data base are discussed

  3. Application of an analytical method for the field calculation in superconducting magnets

    International Nuclear Information System (INIS)

    Martinelli, G.; Morini, A.

    1983-01-01

    Superconducting magnets are taking on ever-growing importance due to their increasing prospects of utilization in electrical machines, nuclear fusion, MHD conversion and high-energy physics. These magnets are generally composed of cylindrical or saddle coils, while a ferromagnetic shield is generally situated outside them. This paper uses an analytical method for calculating the magnetic field at every point in a superconducting magnet composed of cylindrical or saddle coils. The method takes into account the real lengths and finite thickness of the coils as well as their radial and axial ferromagnetic shields, if present. The values and distribution of the flux density for some superconducting magnets of high dimensions and high magnetic field, composed of cylindrical or saddle coils, are also given. The results obtained with analytical method are compared with those obtained using numerical methods

  4. Ferromagnetic film on a superconducting substrate

    Energy Technology Data Exchange (ETDEWEB)

    Bulaevskii, L. N.; Chudnovsky, E. M.

    2001-01-01

    We study the equilibrium domain structure and magnetic flux around a ferromagnetic film with perpendicular magnetization M{sub 0} on a superconducting (SC) substrate. At 4{pi}M{sub 0}>1; {lambda}{sub L} being the London penetration length.

  5. Superconducting quantum interference monitor of charged particle beam current

    International Nuclear Information System (INIS)

    Gertsev, K.F.; Mikheev, M.S.

    1981-01-01

    Description and test results of the monitor of charged particle beam current on the base of the high-frequency superconducting quantum interference detector with lead slotted shield are presented. The toroidal superconducting coil, which covers the measured beam has 16 turns wound by the lead belt of 7 mm width with 0.5 mm gaps between the turns. A superconducting low-coupling monitor having two holes and point oxidated niobium contact has been used in the mode of quanta counting of magnetic flux. The lead point shield was 2 mm thick and it had 30 mm aperture. The coefficient of background shielding within 0-200 Hz frequency range constituted more than 10 8 . The threshold current resolution of the monitor had the value less than 01 μA √Hz. The suggested monitor requires helium cooling. The proposed design of the monitor is applicable for mounting on the vacuum chamber when it is surrounded by helium conductor. In other cases mounting of low-powerful autonomic system or cryostat of helium storage up to several weeks is possible [ru

  6. Observation of quantum Zeno effect in a superconducting flux qubit

    International Nuclear Information System (INIS)

    Kakuyanagi, K; Baba, T; Matsuzaki, Y; Nakano, H; Saito, S; Semba, K

    2015-01-01

    When a quantum state is subjected to frequent measurements, the time evolution of the quantum state is frozen. This is called the quantum Zeno effect. Here, we observe such an effect by performing frequent discrete measurements in a macroscopic quantum system, a superconducting quantum bit. The quantum Zeno effect induced by discrete measurements is similar to the original idea of the quantum Zeno effect. By using a Josephson bifurcation amplifier pulse readout, we have experimentally suppressed the time evolution of Rabi oscillation using projective measurements, and also observed the enhancement of the quantum state holding time by shortening the measurement period time. This is a crucial step to realize quantum information processing using the quantum Zeno effect. (papers)

  7. European roadmap on superconductive electronics - status and perspectives

    Science.gov (United States)

    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

    Executive SummaryFor four decades semiconductor electronics has followed Moore’s law: with each generation of integration the circuit features became smaller, more complex and faster. This development is now reaching a wall so that smaller is no longer any faster. The clock rate has saturated at about 3-5 GHz and the parallel processor approach will soon reach its limit. The prime reason for the limitation the semiconductor electronics experiences is not the switching speed of the individual transistor, but its power dissipation and thus heat. Digital superconductive electronics is a circuit- and device-technology that is inherently faster at much less power dissipation than semiconductor electronics. It makes use of superconductors and Josephson junctions as circuit elements, which can provide extremely fast digital devices in a frequency range - dependent on the material - of hundreds of GHz: for example a flip-flop has been demonstrated that operated at 750 GHz. This digital technique is scalable and follows similar design rules as semiconductor devices. Its very low power dissipation of only 0.1 μW per gate at 100 GHz opens the possibility of three-dimensional integration. Circuits like microprocessors and analogue-to-digital converters for commercial and military applications have been demonstrated. In contrast to semiconductor circuits, the operation of superconducting circuits is based on naturally standardized digital pulses the area of which is exactly the flux quantum Φ0. The flux quantum is also the natural quantization unit for digital-to-analogue and analogue-to-digital converters. The latter application is so precise, that it is being used as voltage standard and that the physical unit ‘Volt’ is defined by means of this standard. Apart from its outstanding features for digital electronics, superconductive electronics provides also the most sensitive sensor for magnetic fields: the Superconducting Quantum Interference Device (SQUID). Amongst

  8. Study of the disorder by means of the superconducting penetration depth

    International Nuclear Information System (INIS)

    Arce, R.D.

    1982-11-01

    Measurements of the weak magnetic field penetration depth in the amorphous superconducting systems Lasub(1-x) Msub(x), being M = Cu, Al, Ga and Au, and in the Zr 70 Cu 30 system are presented. Measurements of the sample geometrical factors and the flux expulsion between the lowest temperature reached and the critical temperature, allows the determination of zero temperature penetration depth. The measurement of the flux expulsion as a function of temperature is used to determine the temperature dependence of penetration depth, used to evaluate the temperature dependence superconducting gap. The magnetization measurements have been made using an rf-SQUID. The evolution of the penetration depth with annealing is studied in the La 70 Cu 30 and Zr 70 Cu 30 systems. Measurements of the electrical resistivity and the critical temperature are used to verify the Gorkov equations in these materials. The variation of the penetration depth with annealing suggests that a metallurgical phase separation occurs within the submicrometer range. Penetration depth measurement is a tool to detect this type of phase separation in high kappa materials. (M.E.L.) [es

  9. Cryogenic Characteristics of the ATLAS Barrel Toroid Superconducting Magnet

    CERN Document Server

    Pengo, R; Delruelle, N; Pezzetti, M; Pirotte, O; Passardi, Giorgio; Dudarev, A; ten Kate, H

    2008-01-01

    ATLAS, one of the experiments of the LHC accelerator under commissioning at CERN, is equipped with a large superconducting magnet the Barrel Toroid (BT) that has been tested at nominal current (20500 A). The BT is composed of eight race-track superconducting coils (each one weights about 45 tons) forming the biggest air core toroidal magnet ever built. By means of a large throughput centrifugal pump, a forced flow (about 10 liter/second at 4.5 K) provides the indirect cooling of the coils in parallel. The paper describes the results of the measurements carried out on the complete cryogenic system assembled in the ATLAS cavern situated 100 m below the ground level. The measurements include, among other ones, the static heat loads, i.e., with no or constant current in the magnet, and the dynamic ones, since additional heat losses are produced, during the current ramp-up or slow dump, by eddy currents induced on the coil casing.

  10. Controllable Quantum States Mesoscopic Superconductivity and Spintronics (MS+S2006)

    Science.gov (United States)

    Takayanagi, Hideaki; Nitta, Junsaku; Nakano, Hayato

    2008-10-01

    Mesoscopic effects in superconductors. Tunneling measurements of charge imbalance of non-equilibrium superconductors / R. Yagi. Influence of magnetic impurities on Josephson current in SNS junctions / T. Yokoyama. Nonlinear response and observable signatures of equilibrium entanglement / A. M. Zagoskin. Stimulated Raman adiabatic passage with a Cooper pair box / Giuseppe Falci. Crossed Andreev reflection-induced giant negative magnetoresistance / Francesco Giazotto -- Quantum modulation of superconducting junctions. Adiabatic pumping through a Josephson weak link / Fabio Taddei. Squeezing of superconducting qubits / Kazutomu Shiokawa. Detection of Berrys phases in flux qubits with coherent pulses / D. N. Zheng. Probing entanglement in the system of coupled Josephson qubits / A. S. Kiyko. Josephson junction with tunable damping using quasi-particle injection / Ryuta Yagi. Macroscopic quantum coherence in rf-SQUIDs / Alexey V. Ustinov. Bloch oscillations in a Josephson circuit / D. Esteve. Manipulation of magnetization in nonequilibrium superconducting nanostructures / F. Giazotto -- Superconducting qubits. Decoherence and Rabi oscillations in a qubit coupled to a quantum two-level system / Sahel Ashhab. Phase-coupled flux qubits: CNOT operation, controllable coupling and entanglement / Mun Dae Kim. Characteristics of a switchable superconducting flux transformer with a DC-SQUID / Yoshihiro Shimazu. Characterization of adiabatic noise in charge-based coherent nanodevices / E. Paladino -- Unconventional superconductors. Threshold temperatures of zero-bias conductance peak and zero-bias conductance dip in diffusive normal metal/superconductor junctions / Iduru Shigeta. Tunneling conductance in 2DEG/S junctions in the presence of Rashba spin-orbit coupling / T. Yokoyama. Theory of charge transport in diffusive ferromagnet/p-wave superconductor junctions / T. Yokoyama. Theory of enhanced proximity effect by the exchange field in FS bilayers / T. Yokoyama. Theory of

  11. Flux-line cutting in granular high-temperature superconductors

    International Nuclear Information System (INIS)

    Perez-Rodriguez, F.; Perez-Gonzalez, A.; Clem, J.R.; Gandolfini, G.; LeBlanc, M.A.

    1997-01-01

    The magnetic response of granular high-temperature superconducting plates subjected to a dc-bias magnetic field and an increasing field perpendicular to it is studied both experimentally and theoretically. The theoretical model is based upon the double critical-state model, which considers not only flux transport but also flux-line cutting effects. Curves of magnetization for the system of grains decoupled by the applied magnetic field in sintered slabs of YBa 2 Cu 3 O 7-x and NdBa 2 Cu 3 O 7-x are analyzed. Good agreement between experimental results and theory is obtained. copyright 1997 The American Physical Society

  12. Design prospect of remountable high-temperature superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Hashizume, Hidetoshi, E-mail: hidetoshi.hashizume@qse.tohoku.ac.jp; Ito, Satoshi

    2014-10-15

    The remountable (mountable and demountable repeatedly) high-temperature superconducting (HTS) magnet has been proposed for huge and complex superconducting magnets in future fusion reactors to fabricate and repair easily the magnet and access inner structural components. This paper summarizes progress in R and D activities of mechanical joints of HTS conductors in terms of the electrical resistance and heat transfer performance at the joint region. The latest experimental results show the low joint resistance, 4 nΩ under 70 kA current condition using REBCO HTS conductor with mechanical lap joint system, and for the cooling system the maximum heat flux of 0.4 MW/m{sup 2} is removed by using bronze sintered porous media with sub-cooled liquid nitrogen. These values indicate that there is large possibility to design the remountable HTS magnet for fusion reactors.

  13. Cryogenic techniques for large superconducting magnets in space

    Science.gov (United States)

    Green, M. A.

    1989-01-01

    A large superconducting magnet is proposed for use in a particle astrophysics experiment, ASTROMAG, which is to be mounted on the United States Space Station. This experiment will have a two-coil superconducting magnet with coils which are 1.3 to 1.7 meters in diameter. The two-coil magnet will have zero net magnetic dipole moment. The field 15 meters from the magnet will approach earth's field in low earth orbit. The issue of high Tc superconductor will be discussed in the paper. The reasons for using conventional niobium-titanium superconductor cooled with superfluid helium will be presented. Since the purpose of the magnet is to do particle astrophysics, the superconducting coils must be located close to the charged particle detectors. The trade off between the particle physics possible and the cryogenic insulation around the coils is discussed. As a result, the ASTROMAG magnet coils will be operated outside of the superfluid helium storage tank. The fountain effect pumping system which will be used to cool the coil is described in the report. Two methods for extending the operating life of the superfluid helium dewar are discussed. These include: operation with a third shield cooled to 90 K with a sterling cycle cryocooler, and a hybrid cryogenic system where there are three hydrogen-cooled shields and cryostat support heat intercept points.

  14. Numerical analysis of magnetic field in superconducting magnetic energy storage

    International Nuclear Information System (INIS)

    Kanamaru, Y.; Amemiya, Y.

    1991-01-01

    This paper reports that the superconducting magnetic energy storage (SMES) is more useful than the other systems of electric energy storage because of larger stored energy and higher efficiency. The other systems are the battery, the flywheel, the pumped-storage power station. Some models of solenoid type SMES are designed in U.S.A. and Japan. But a high magnetic field happens by the large scale SMES in the living environment, and makes the erroneous operations of the computer display, the pacemaker of the heart and the electronic equipments. We study some fit designs of magnetic shielding of the solenoidal type SMES for reduction of the magnetic field in living environment. When some superconducting shielding coils are over the main storage coil, magnetic field reduces remarkably than the case of non shielding coil. The calculated results of the magnetic field are obtained y the finite element method

  15. Fusion neutron yield and flux calculation on HT-7 superconducting tokamak

    International Nuclear Information System (INIS)

    Fu Yanzhang; Zhu Yubao; Chen Juequan

    2006-01-01

    Neutron yield and flux have been numerically estimated on HT-7 tokamak. The total fusion neutron yield and neutron flux distribution on different positions and azimuth angles of the device are presented. Analyses on the errors induced by ion temperature and density distribution factors are given in detail. The results of the calculations provide a useful database for neutron diagnostics and neutron radiation protection. (authors)

  16. Flux-transfer losses in helically wound superconducting power cables

    International Nuclear Information System (INIS)

    Clem, John R; Malozemoff, A P

    2013-01-01

    Minimization of ac losses is essential for economic operation of high-temperature superconductor (HTS) ac power cables. A favorable configuration for the phase conductor of such cables has two counter-wound layers of HTS tape-shaped wires lying next to each other and helically wound around a flexible cylindrical former. However, if magnetic materials such as magnetic substrates of the tapes lie between the two layers, or if the winding pitch angles are not opposite and essentially equal in magnitude to each other, current distributes unequally between the two layers. Then, if at some point in the ac cycle the current of either of the two layers exceeds its critical current, a large ac loss arises from the transfer of flux between the two layers. A detailed review of the formalism, and its application to the case of paramagnetic substrates including the calculation of this flux-transfer loss, is presented. (paper)

  17. Development and numerical analysis of low specific speed mixed-flow pump

    International Nuclear Information System (INIS)

    Li, H F; Huo, Y W; Pan, Z B; Zhou, W C; He, M H

    2012-01-01

    With the development of the city, the market of the mixed flow pump with large flux and high head is prospect. The KSB Shanghai Pump Co., LTD decided to develop low speed specific speed mixed flow pump to meet the market requirements. Based on the centrifugal pump and axial flow pump model, aiming at the characteristics of large flux and high head, a new type of guide vane mixed flow pump was designed. The computational fluid dynamics method was adopted to analyze the internal flow of the new type model and predict its performances. The time-averaged Navier-Stokes equations were closed by SST k-ω turbulent model to adapt internal flow of guide vane with larger curvatures. The multi-reference frame(MRF) method was used to deal with the coupling of rotating impeller and static guide vane, and the SIMPLEC method was adopted to achieve the coupling solution of velocity and pressure. The computational results shows that there is great flow impact on the head of vanes at different working conditions, and there is great flow separation at the tailing of the guide vanes at different working conditions, and all will affect the performance of pump. Based on the computational results, optimizations were carried out to decrease the impact on the head of vanes and flow separation at the tailing of the guide vanes. The optimized model was simulated and its performance was predicted. The computational results show that the impact on the head of vanes and the separation at the tailing of the guide vanes disappeared. The high efficiency of the optimized pump is wide, and it fit the original design destination. The newly designed mixed flow pump is now in modeling and its experimental performance will be getting soon.

  18. Development and numerical analysis of low specific speed mixed-flow pump

    Science.gov (United States)

    Li, H. F.; Huo, Y. W.; Pan, Z. B.; Zhou, W. C.; He, M. H.

    2012-11-01

    With the development of the city, the market of the mixed flow pump with large flux and high head is prospect. The KSB Shanghai Pump Co., LTD decided to develop low speed specific speed mixed flow pump to meet the market requirements. Based on the centrifugal pump and axial flow pump model, aiming at the characteristics of large flux and high head, a new type of guide vane mixed flow pump was designed. The computational fluid dynamics method was adopted to analyze the internal flow of the new type model and predict its performances. The time-averaged Navier-Stokes equations were closed by SST k-ω turbulent model to adapt internal flow of guide vane with larger curvatures. The multi-reference frame(MRF) method was used to deal with the coupling of rotating impeller and static guide vane, and the SIMPLEC method was adopted to achieve the coupling solution of velocity and pressure. The computational results shows that there is great flow impact on the head of vanes at different working conditions, and there is great flow separation at the tailing of the guide vanes at different working conditions, and all will affect the performance of pump. Based on the computational results, optimizations were carried out to decrease the impact on the head of vanes and flow separation at the tailing of the guide vanes. The optimized model was simulated and its performance was predicted. The computational results show that the impact on the head of vanes and the separation at the tailing of the guide vanes disappeared. The high efficiency of the optimized pump is wide, and it fit the original design destination. The newly designed mixed flow pump is now in modeling and its experimental performance will be getting soon.

  19. Non-preferential fuelling of the Na(+)/K(+)-ATPase pump.

    Science.gov (United States)

    Fernández-Moncada, Ignacio; Barros, L Felipe

    2014-06-15

    There is abundant evidence that glycolysis and the Na(+)/K(+)-ATPase pump are functionally coupled, and it is thought that the nature of the coupling is energetic, with glycolysis providing the ATP that fuels the pump. This notion has been instrumental to current models of brain energy metabolism. However, structural and biophysical considerations suggest that the pump should also have access to mitochondrial ATP, which is much more abundant. In the present study, we have investigated the source of ATP that fuels the Na(+) pump in astrocytes, taking advantage of the high temporal resolution of recently available FRET nanosensors for glucose, lactate and ATP. The activity of the Na(+) pump was assessed in parallel with the Na(+)-sensitive dye SBFI AM (Na(+)-binding benzofuran isophthalate acetoxymethyl ester). OXPHOS (oxidative phosphorylation) inhibition resulted in bulk ATP depletion and a 5-fold stimulation of glycolytic flux, in spite of which Na(+) pumping was inhibited by 90%. Mathematical modelling of ATP dynamics showed that the observed pump failure is inconsistent with preferential fuelling of the Na(+) pump by glycolytic ATP. We conclude that the nature of the functional coupling between the Na(+) pump and the glycolytic machinery is not energetic and that the pump is mainly fuelled by mitochondrial ATP.

  20. Interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

    2015-07-15

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

  1. Technology development of fabrication NbTi and Nb3 Sn superconducting wires

    International Nuclear Information System (INIS)

    Rodrigues Junior, D.; Bormio, C.; Baldan, C.A.; Ramos, M.J.; Pinatti, D.G.

    1988-01-01

    The technology development of NbTi and Nb 3 Sn superconducting wires are studied, mentioning the use of fluxes capture theory in the sizing of wires fabrication. The fabrication process, the thermal treatment and the experimental datas of critical temperature and current of Nb 3 Sn wires are described. (C.G.C.) [pt

  2. Controlled initialization of superconducting π-phaseshifters and possible applications

    International Nuclear Information System (INIS)

    Mielke, Olaf; Ortlepp, Thomas; Toepfer, Hannes; Kunert, Juergen; Meyer, Hans-Georg

    2010-01-01

    The rapid single-flux quantum electronics (RSFQ) is a superconducting, naturally digital circuit family which is currently close to being commercially applied. RSFQ is outstanding because of its very low switching energy resulting in very low power consumption. This advantage causes, however, a significant influence of thermal noise. For industrial applications, a certain noise immunity is required which is still a challenge, especially for circuits of higher complexity. Integrating phase-shifting elements is a new concept for further improvements concerning stability against the influence of thermal noise. We have already shown that the implementation of phase-shifting elements significantly reduces the influence of thermal noise on circuit behavior by experimentally analyzing the bit-error rate (Mielke et al 2009 IEEE Trans. Appl. Supercond. 19 621-5). Concepts which are easily implementable in standard niobium technology are especially promising. The π-phaseshifter consists of a superconducting loop which is able to store a single flux quantum. The loop current related to the stored flux creates a well-defined phase shift. To achieve the correct functionality of complex circuits it is essential to store exactly one flux quantum in each π-phaseshifter during the cooling down of the chip. Thus, for studying the feasibility of this new approach, the initialization reliability of the π-phaseshifter needs to be verified. We present an experimental investigation of this reliability to obtain a general assessment for the application of the π-phaseshifter in niobium technology. Furthermore, we compare the configuration shielded by a solid ground plane with a configuration with a ground-plane hole below the π-phaseshifter. Justified by the experimental results we suggest programmable RSFQ circuits based on π-phaseshifters. The characteristics of these devices can be influenced by a controlled initialization of the π-phaseshifter. The fabrication was performed by

  3. Superconducting coil and method of stress management in a superconducting coil

    Science.gov (United States)

    McIntyre, Peter M.; Shen, Weijun; Diaczenko, Nick; Gross, Dan A.

    1999-01-01

    A superconducting coil (12) having a plurality of superconducting layers (18) is provided. Each superconducting layer (18) may have at least one superconducting element (20) which produces an operational load. An outer support structure (24) may be disposed outwardly from the plurality of layers (18). A load transfer system (22) may be coupled between at least one of the superconducting elements (20) and the outer support structure (24). The load transfer system (22) may include a support matrix structure (30) operable to transfer the operational load from the superconducting element (20) directly to the outer support structure (24). A shear release layer (40) may be disposed, in part, between the superconducting element (20) and the support matrix structure (30) for relieving a shear stress between the superconducting element (20) and the support matrix structure (30). A compliant layer (42) may also be disposed, in part, between the superconducting element (20) and the support matrix structure (30) for relieving a compressive stress on the superconducting element (20).

  4. Hybrid type I-type II superconducting behavior in magnesium diboride

    International Nuclear Information System (INIS)

    Kunchur, M.N.; Saracila, G.; Arcos, D.A.; Cui, Y.; Pogrebnyakov, A.; Orgiani, P.; Xi, X.X.

    2006-01-01

    In traditional type-II superconductors, an applied magnetic field depresses the transition temperature and introduces magnetic flux vortices that cause resistive losses accompanied by a broadening of the transition. High-field high-pulsed-current measurements have revealed a new hybrid behavior in disordered magnesium diboride films: The superconductivity survives high magnetic fields by entering a mixed state with vortices (like a type II superconductor) but holds its vortices nearly motionless and avoids dissipation (like a type I superconductor). A study of this phenomenon in magnesium diboride films with varying degrees of scattering indicate that the hybrid type I-type II behavior arises from the two-band nature of the superconductivity and the different degrees of influence that disorder exerts on its different bands. (author)

  5. Moderation of flux jumps dynamics by eddy-currents in a disk shape NbTi superconductor

    International Nuclear Information System (INIS)

    Vasiliev, S.; Nabialek, A.; Piechota, S.; Szymczak, H.; Chabanenko, V.V.; Rusakov, V.

    2004-01-01

    We studied the moderation of the flux jumps dynamics in a disc shape NbTi-50% superconductor caused by eddy-currents induced in two copper cylinders attached to both surfaces of the investigated sample. We investigated experimentally the time of the flux jump duration, amount of the magnetic flux entering the sample during the jump as well as the sine structure of the jumps as a function of temperature and the external magnetic field. A simple theoretical model, which describes the magnetic field dependence of the amount of the magnetic flux entering the superconducting sample during the flux jump, was developed. (author)

  6. Measurement of the terrestrial magnetic field and its anomalies; Mesures du champ magnetique terrestre et de ses anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Duret, D.

    1994-12-31

    After a presentation of the terrestrial magnetic field and its various anomalies, the different types of magnetometers commonly used are reviewed with their characteristics and performances: scalar magnetometers (free precession and continuous polarization proton magnetometers, dynamic polarization proton magnetometers, optical pumping magnetometers, electronic resonance scalar magnetometers (without pumping)); vectorial magnetometers (flux gate magnetometers, induction magnetometers, suspended magnet magnetometers, superconducting magnetometers, integrated magnetometers, resonance directional magnetometers). The magnetometry market and applications are discussed. 20 figs., 9 tabs., 72 refs.

  7. Measurement of the terrestrial magnetic field and its anomalies

    International Nuclear Information System (INIS)

    Duret, D.

    1994-01-01

    After a presentation of the terrestrial magnetic field and its various anomalies, the different types of magnetometers commonly used are reviewed with their characteristics and performances: scalar magnetometers (free precession and continuous polarization proton magnetometers, dynamic polarization proton magnetometers, optical pumping magnetometers, electronic resonance scalar magnetometers (without pumping)); vectorial magnetometers (flux gate magnetometers, induction magnetometers, suspended magnet magnetometers, superconducting magnetometers, integrated magnetometers, resonance directional magnetometers). The magnetometry market and applications are discussed. 20 figs., 9 tabs., 72 refs

  8. Minimum Quench Energy and Early Quench Development in NbTi Superconducting Strands

    CERN Document Server

    Breschi, M; Boselli, M; Bottura, Luca; Devred, Arnaud; Ribani, P L; Trillaud, F

    2007-01-01

    The stability of superconducting wires is a crucial task in the design of safe and reliable superconducting magnets. These magnets are prone to premature quenches due to local releases of energy. In order to simulate these energy disturbances, various heater technologies have been developed, such as coated tips, graphite pastes, and inductive coils. The experiments studied in the present work have been performed using a single-mode diode laser with an optical fiber to illuminate the superconducting strand surface. Minimum quench energies and voltage traces at different magnetic flux densities and transport currents have been measured on an LHC-type, Cu/NbTi wire bathed in pool boiling helium I. This paper deals with the numerical analysis of the experimental data. In particular, a coupled electromagnetic and thermal model has been developed to study quench development and propagation, focusing on the influence of heat exchange with liquid helium.

  9. Superconductivity

    International Nuclear Information System (INIS)

    Kakani, S.L.; Kakani, Shubhra

    2007-01-01

    The monograph provides readable introduction to the basics of superconductivity for beginners and experimentalists. For theorists, the monograph provides nice and brief description of the broad spectrum of experimental properties, theoretical concepts with all details, which theorists should learn, and provides a sound basis for students interested in studying superconducting theory at the microscopic level. Special chapter on the theory of high-temperature superconductivity in cuprates is devoted

  10. A quark-antiquark potential from a superconducting model of confinement

    Directory of Open Access Journals (Sweden)

    J.W. Alcock

    1983-10-01

    Full Text Available The Landau-Ginzburg phenomenological theory of superconductivity is used as a model of flux confinement. A monopole pair of sources is included to simulate a quark-antiquark system. The interaction energy is found in the static approximation appropriate for heavy quark systems, and equated with the interquark potential. This potential is compared with other suggested phenomenological potentials and succeeds in reproducing heavy quark spectra.

  11. Quasi-one-dimensional intermittent flux behavior in superconducting films

    DEFF Research Database (Denmark)

    Qviller, A. J.; Yurchenko, V. V.; Galperin, Y. M.

    2012-01-01

    Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa2Cu3O7-δ deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. ...

  12. Nonclassical correlations in superconducting circuits

    Energy Technology Data Exchange (ETDEWEB)

    Migliore, Rosanna [Dipartimento di Scienze Fisiche ed Astronomiche, Universita di Palermo (Italy); CNR-INFM, UdR CNISM di Palermo, Palermo (Italy); Scala, Matteo [Dipartimento di Scienze Fisiche ed Astronomiche, Universita di Palermo (Italy); Departamento de Optica, Facultad de Fisica, Universidad Complutense, Madrid (Spain); Guccione, Marina; Sanchez-Soto, Luis L. [Dipartimento di Scienze Fisiche ed Astronomiche, Universita di Palermo (Italy); Messina, Antonino [Departamento de Optica, Facultad de Fisica, Universidad Complutense, Madrid (Spain)

    2009-05-15

    A key step on the road map to solid-state quantum information processing (and to a deeper understanding of many counterintuitive aspects of quantum mechanics) is the generation and manipulation of nonclassical correlations between different quantum systems. Within this framework, we analyze the possibility of generating maximally entangled states in a system of two superconducting flux qubits, as well as the effectof their own environments on the entanglement dynamics. The analysis reported here confirms that the phenomena of sudden birth and sudden death of the entanglement do not depend on the particular measure of the entanglement adopted (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Flux creep in Bi2Sr2CaCu2O8 epitaxial films

    International Nuclear Information System (INIS)

    Zeldov, E.; Amer, N.M.; Koren, G.; Gupta, A.

    1990-01-01

    We incorporate the experimentally deduced flux line potential well structure into the flux creep model. Application of this approach to the resistive transition in Bi 2 Sr 2 CaCu 2 O 8 epitaxial films explains the power law voltage-current characteristics and the nonlinear current dependence of the activation energy. The results cannot be accounted for by a transition into a superconducting vortex-glass phase

  14. Self-generated magnetic flux in YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

    OpenAIRE

    Mints, R. G.; Papiashvili, Ilya

    2000-01-01

    Grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films are considered as Josephson junctions with a critical current density $j_c(x)$ alternating along the junction. A self-generated magnetic flux is treated both analytically and numerically for an almost periodic distribution of $j_c(x)$. We obtained a magnetic flux-pattern similar to the one which was recently observed experimentally.

  15. A three dimensional calculation of neutron streaming through ITER tokamak pumping ducts with the Monte Carlo code TRIPOLI-2

    International Nuclear Information System (INIS)

    Bresard, I.; Diop, C.M.; Giancarli, L.; Gervaise, F.

    1991-01-01

    In the frame of the ITER tokamak project, the streaming of neutrons through pumping ducts up to the properly so called pumping system is studied. The gas evacuation device of the ITER plasma consists of a set of vacuum pumps which are located in a room which is outside the main machine building. These pumps receive the exhaust gas through several pumping ducts with a cross section of about four square meters and a length of about ten meters. Although insensitive to the magnetic field, the 14 MeV neutrons from plasma D-T thermonuclear reactions can penetrate in the divertor and reach the room pumping device by propagation through the bent ducts. Different components of this system, such as the bellows, turbomolecular pumps, etc., are irradiated and that raises radiation problems. In this study we determine, by using 3D Monte Carlo transport code TRIPOLI-2, neutron fluxes, dose rates and heatings due to neutrons which have streamed out the plasma through the bent ducts, at several points of the pumping room. Results show the neutron flux attenuation reachs a factor 10 -5 from plasma chamber to the pumping hall; the neutron heatings are estimated to 1.9x10 -3 W/cm 3 in bellow stainless steel at duct entrance, and 8x10 -7 W/cm 3 in the turbopumping stainless steel structure, inside pumping hall. The neutron fluxes obtained will be used to compute gamma source produced by radiative, inelastic process and gamma rays from formed activation products. Then, the knowledge of gamma source will allow to compute gamma dose rate and heating. The dose rates and heatings obtained will contribute to the definition of the ITER pumping system technical options and to establish pumping hall access conditions, also. (orig.)

  16. Y-junction of superconducting Josephson chains

    International Nuclear Information System (INIS)

    Giuliano, Domenico; Sodano, Pasquale

    2009-01-01

    We show that, for pertinent values of the fabrication and control parameters, an attractive finite coupling fixed point emerges in the phase diagram of a Y-junction of superconducting Josephson chains. The new fixed point arises only when the dimensionless flux f piercing the central loop of the network equals π and, thus, does not break time-reversal invariance; for f≠π, only the strongly coupled fixed point survives as a stable attractive fixed point. Phase slips (instantons) have a crucial role in establishing this transition: we show indeed that, at f=π, a new set of instantons-the W-instantons-comes into play to destabilize the strongly coupled fixed point. Finally, we provide a detailed account of the Josephson current-phase relationship along the arms of the network, near each one of the allowed fixed points. Our results evidence remarkable similarities between the phase diagram accessible to a Y-junction of superconducting Josephson chains and the one found in the analysis of quantum Brownian motion on frustrated planar lattices

  17. Sudden flux change studies in high field superconducting accelerator magnets

    International Nuclear Information System (INIS)

    Feher, S.; Bordini, B.; Carcagno, R.; Makulski, A.; Orris, D.F.; Pischalnikov, Y.M.; Sylvester, C.; Tartaglia, M.; Tompkins, J.C.; Zlobin, A.V.

    2004-01-01

    As part of the High Field Magnet Program at Fermilab many magnets have been tested which utilize multi strand Rutherford type cable made of state-of-the art Nb 3 Sn strands. During these magnet tests we observed sudden flux changes by monitoring coil voltages and the magnetic field close to the magnets. These flux changes might be linked to magnet instabilities. The voltage spike signals were correlated with quench antenna signals, a strong indication that these are magnet phenomena. With a new high resolution voltage spike detection system, we were able to observe the detailed structure of the spikes. Two fundamentally different signal shapes were distinguished, most likely generated by different mechanisms

  18. Improvements in or relating to superconducting members and methods of manufacture thereof

    International Nuclear Information System (INIS)

    Madson, P.E.; Charlesworth, J.P.; Armstrong, D.

    1975-01-01

    Reference is made to superconducting materials having comparatively high critical temperatures and critical magnetic fields. Such materials include compounds of A15 crystal structure having the general formula A 3 B, where A is Nb or V and B is one or more of the elements Al, Ga, In, Si, Ge and Sn. A method for manufacturing such materials is described in BP 1 333 554. The present specification is concerned with 'stabilisation' of materials manufactured by the method described in the earlier specification. By 'stabilization' is here meant prrevention or reduction of the undesirable effects of sudden movement of magnetic flux, known as 'flux jumps'. Two methods of stabilization are combined in the same material, known respectively as 'filamentary stabilization', in which the superconducting material is present in the form of fine filaments in a normally conducting matrix, and 'dynamic stabilization', in which a proportion of the normally conducting matrix material takes the form of a material of high electrical conductivity, such as pure Cu. (G.B.)

  19. Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around Tc

    Science.gov (United States)

    Romanenko, A.; Grassellino, A.; Melnychuk, O.; Sergatskov, D. A.

    2014-05-01

    We report a strong effect of the cooling dynamics through Tc on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120 °C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance, while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.

  20. Physics of Limiting Phenomena in Superconducting Microwave Resonators: Vortex Dissipation, Ultimate Quench and Quality Factor Degradation Mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Checchin, Mattia [Illinois Inst. of Technology, Chicago, IL (United States)

    2016-12-01

    Superconducting niobium accelerating cavities are devices operating in radio-frequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described in detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associate d to the

  1. Physics of limiting phenomena in superconducting microwave resonators: Vortex dissipation, ultimate quench and quality factor degradation mechanisms

    Science.gov (United States)

    Checchin, Mattia

    Superconducting niobium accelerating cavities are devices operating in radiofrequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described in detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associated to the superheating

  2. Superconductivity

    International Nuclear Information System (INIS)

    Langone, J.

    1989-01-01

    This book explains the theoretical background of superconductivity. Includes discussion of electricity, material fabrication, maglev trains, the superconducting supercollider, and Japanese-US competition. The authors reports the latest discoveries

  3. ac superconducting articles

    International Nuclear Information System (INIS)

    Meyerhoff, R.W.

    1977-01-01

    A noval ac superconducting cable is described. It consists of a composite structure having a superconducting surface along with a high thermally conductive material wherein the superconducting surface has the desired physical properties, geometrical shape and surface finish produced by the steps of depositing a superconducting layer upon a substrate having a predetermined surface finish and shape which conforms to that of the desired superconducting article, depositing a supporting layer of material on the superconducting layer and removing the substrate, the surface of the superconductor being a replica of the substrate surface

  4. Designs for a TFTR full-power pumped limiter

    International Nuclear Information System (INIS)

    Budny, R.

    1986-10-01

    A pumped-limiter system which would provide increased particle control and enhance the performance of full-power discharges is being considered for TFTR. The system consists of two toroidal belts located near the Zirconium-Aluminium (ZrAl) getter panels. The limiter blades would be made of carbon/carbon composite in order to have a very thin profile, allowing a large fraction of the scrape-off flux to be pumped. Simulations of the plasma scrape-off and neutral transport indicate that the limiter pumping should reduce the recycling coefficient by 10 to 25%. Simulations of central plasma processes indicate that the lowered recycling could increase Q/sub fusion/ by more than 100%. This paper discusses the designs and the performance predictions for the system

  5. Structures for handling high heat fluxes

    International Nuclear Information System (INIS)

    Watson, R.D.

    1990-01-01

    The divertor is recognized as one of the main performance limiting components for ITER. This paper reviews the critical issues for structures that are designed to withstand heat fluxes >5 MW/m 2 . High velocity, sub-cooled water with twisted tape inserts for enhanced heat transfer provides a critical heat flux limit of 40-60 MW/m 2 . Uncertainties in physics and engineering heat flux peaking factors require that the design heat flux not exceed 10 MW/m 2 to maintain an adequate burnout safety margin. Armor tiles and heat sink materials must have a well matched thermal expansion coefficient to minimize stresses. The divertor lifetime from sputtering erosion is highly uncertain. The number of disruptions specified for ITER must be reduced to achieve a credible design. In-situ plasma spray repair with thick metallic coatings may reduce the problems of erosion. Runaway electrons in ITER have the potential to melt actively cooled components in a single event. A water leak is a serious accident because of steam reactions with hot carbon, beryllium, or tungsten that can mobilize large amounts of tritium and radioactive elements. If the plasma does not shutdown immediately, the divertor can melt in 1-10 s after a loss of coolant accident. Very high reliability of carbon tile braze joints will be required to achieve adequate safety and performance goals. Most of these critical issues will be addressed in the near future by operation of the Tore Supra pump limiters and the JET pumped divertor. An accurate understanding of the power flow out of edge of a DT burning plasma is essential to successful design of high heat flux components. (orig.)

  6. High-temperature superconductivity

    International Nuclear Information System (INIS)

    Ginzburg, V.L.

    1987-07-01

    After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

  7. Superconducting accelerator technology

    International Nuclear Information System (INIS)

    Grunder, H.A.; Hartline, B.K.

    1986-01-01

    Modern and future accelerators for high energy and nuclear physics rely increasingly on superconducting components to achieve the required magnetic fields and accelerating fields. This paper presents a practical overview of the phenomenon of superconductivity, and describes the design issues and solutions associated with superconducting magnets and superconducting rf acceleration structures. Further development and application of superconducting components promises increased accelerator performance at reduced electric power cost

  8. Test of a cryogenic set-up for a 10 meter long liquid nitrogen cooled superconducting power cable

    DEFF Research Database (Denmark)

    Træholt, Chresten; Rasmussen, Carsten; Kühle (fratrådt), Anders Van Der Aa

    2000-01-01

    High temperature superconducting power cables may be cooled by a forced flow of sub-cooled liquid nitrogen. One way to do this is to circulate the liquid nitrogen (LN2) by means of a mechanical pump through the core of the cable and through a sub-cooler.Besides the cooling station, the cryogenics...... cable. We report on our experimental set-up for testing a 10 meter long high temperature superconducting cable with a critical current of 3.2 kA at 77K. The set-up consists of a custom designed cable end termination, current lead, coolant feed-through, liquid nitrogen closed loop circulation system...

  9. The energy dependence of photon-flux and efficiency in the NRF measurement

    Energy Technology Data Exchange (ETDEWEB)

    Agar, Osman [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Karamanoglu Mehmetbey University, Department of Physics, 70100 Karaman (Turkey); Gayer, Udo; Merter, Laura; Pai, Haridas; Pietralla, Norbert; Ries, Philipp; Romig, Christopher; Werner, Volker; Schillling, Marcel; Zweidinger, Markus [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany)

    2016-07-01

    The calibration of the detector efficiency and the photon-flux distribution play an important role during the analysis of nuclear resonance fluorescence (NRF) measurements. The nucleus {sup 11}B is a frequently used calibration target with well-known photo-excitation cross sections. The product of photon flux and efficiency is determined exploiting γ-ray transitions of the {sup 11}B monitoring target. Photon-flux calibrations from numerous measurements at the superconducting Darmstadt electron linear accelerator (S-DALINAC) are carried out up to the neutron separation threshold, in order to obtain a system check of influences of absorbers on the flux, and to check against different GEANT models as well as parametrizations of the Schiff formula.

  10. Superconducting technology

    International Nuclear Information System (INIS)

    2010-01-01

    Superconductivity has a long history of about 100 years. Over the past 50 years, progress in superconducting materials has been mainly in metallic superconductors, such as Nb, Nb-Ti and Nb 3 Sn, resulting in the creation of various application fields based on the superconducting technologies. High-T c superconductors, the first of which was discovered in 1986, have been changing the future vision of superconducting technology through the development of new application fields such as power cables. On basis of these trends, future prospects of superconductor technology up to 2040 are discussed. In this article from the viewpoints of material development and the applications of superconducting wires and electronic devices. (author)

  11. Superconducting pinning in BCC niobium-base alloys

    International Nuclear Information System (INIS)

    Hu, S.

    1981-01-01

    The structure dependence of critical current density J/sub c/ in superconducting alloys Nb--Zr and Nb--Ti was studied by means of x-ray analysis and tensile test. Experimental results indicate that, in the absence of second phase particles, annealing increases J/sub c/ in deformed alloys due to rearrangement of dislocations into cell structure and the cell walls are effective pinning centers for magnetic flux. In the precipitation process of second phase particles, new dislocations are formed due to the relaxation of coherent stress field. These new dislocations increases the dislocation density and the flux pinning ability of the cell walls, which in turn lead to a further increase of J/sub c/. The mechanism that causes precipitates to increase the current-carrying ability in Nb--Zr and Nb--Ti alloys is therefore the same as that of cold-work deformation

  12. Theory of a peristaltic pump for fermionic quantum fluids

    Science.gov (United States)

    Romeo, F.; Citro, R.

    2018-05-01

    Motivated by the recent developments in fermionic cold atoms and in nanostructured systems, we propose the model of a peristaltic quantum pump. Differently from the Thouless paradigm, a peristaltic pump is a quantum device that generates a particle flux as the effect of a sliding finite-size microlattice. A one-dimensional tight-binding Hamiltonian model of this quantum machine is formulated and analyzed within a lattice Green's function formalism on the Keldysh contour. The pump observables, as, e.g., the pumped particles per cycle, are studied as a function of the pumping frequency, the width of the pumping potential, the particles mean free path, and system temperature. The proposed analysis applies to arbitrary peristaltic potentials acting on fermionic quantum fluids confined to one dimension. These confinement conditions can be realized in nanostructured systems or, in a more controllable way, in cold atoms experiments. In view of the validation of the theoretical results, we describe the outcomes of the model considering a fermionic cold atoms system as a paradigmatic example.

  13. Theory of the Knight Shift and Flux Quantization in Superconductors

    Science.gov (United States)

    Cooper, L. N.; Lee, H. J.; Schwartz, B. B.; Silvert, W.

    1962-05-01

    Consequences of a generalization of the theory of superconductivity that yields a finite Knight shift are presented. In this theory, by introducing an electron-electron interaction that is not spatially invariant, the pairing of electrons with varying total momentum is made possible. An expression for Xs (the spin susceptibility in the superconducting state) is derived. In general Xs is smaller than Xn, but is not necessarily zero. The precise magnitude of Xs will vary from sample to sample and will depend on the nonuniformity of the samples. There should be no marked size dependence and no marked dependence on the strength of the magnetic field; this is in accord with observation. The basic superconducting properties are retained, but there are modifications in the various electromagnetic and thermal properties since the electrons paired are not time sequences of this generalized theory on flux quantization arguments are presented.(auth)

  14. Towards a physics-integrated view on divertor pumping

    International Nuclear Information System (INIS)

    Day, Chr.; Gleason-González, C.; Hauer, V.; Igitkhanov, Y.; Kalupin, D.; Varoutis, S.

    2014-01-01

    Highlights: • Physics-integrated design approaches are to be preferred over approaches based on simple requirement lists. • A physics-integrated assessment is presented for the divertor vacuum pumping system based on detachment onset conditions for the divertor. • This approach considers density dependent pump albedo to reflect the effects of gas recycling at the divertor and the changes in flow regime with density. • A comparison with DEMO indicates that the divertor pumping system for a pulsed DEMO scales less than linearly with fusion power. - Abstract: One key requirement to design the inner fuel cycle of a divertor tokamak is defined by the torus vessel gas throughput and composition, and the sub-divertor neutral pressure at which the exhaust gas has to be pumped. This paper illustrates how divertor physics aspects can be translated to requirements on the divertor vacuum pumping system. An example workflow is presented that links the realization of detachment conditions with the sub-divertor neutral gas flow patterns in order to determine the appropriate number of torus vacuum pumps. For the example case of a fusion DEMO size machine, it was found that 7 actively pumping cryopumps (ITER-type) are necessary to handle the gas throughput that is needed to manage the heat flux and densities related to detachment onset

  15. Switching process between bistable positons of multiquantum flux tubes in a thin-film type I superconductor

    International Nuclear Information System (INIS)

    Parisi, J.; Huebener, R.P.; Muhlemeier, B.

    1983-01-01

    A superconducting memory device based on a bistable vortex position represents an interesting storage medium for future Josephson computers. In order to study the operational mode of such a single-flux quantum memory cell, we use as a model system multiquantum flux tubes in a thin-film type I superconductor (Pb). By employing high-resolution stroboscopic magnetooptical flux detection, we are able to globally visualize both spatial and temporal behavior of rapidly switching individual flux tubes. All experimental results agree reasonably well with theoretical model considerations of the energy balance during the elementary switching process

  16. Quantum heat engine with coupled superconducting resonators

    DEFF Research Database (Denmark)

    Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.

    2017-01-01

    the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal......We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....

  17. Gauge models of planar high-temperature superconductivity without parity violation

    International Nuclear Information System (INIS)

    Mavromatos, N.E.; Grenoble-1 Univ., 74 - Annecy

    1993-02-01

    A status report is given of a parity-invariant model of two-dimensional superconductivity. The model consists of two-species of fermions coupled with opposite sign to an Abelian gauge field and is closely related to QED 3 . The dynamical generation of a parity-conserving fermion mass and the finite temperature symmetry restoration transition is studied, and it is shown, how the parity-invariant model arises as an effective long-wavelength theory of the dynamics of holes in a two-dimensional quantum antiferromagnetic system on a bi-partite lattice. The model exhibits type-II superconductivity without parity or time-reversal symmetry violation, a high value of 2 Δ /k B T c , flux quantization with quantum hc/2e and a two-dimensional Meissner effect. (author) 82 refs.; 15 figs.; 4 tabs

  18. Magnetic design of a 14 mm period prototype superconducting undulator

    Energy Technology Data Exchange (ETDEWEB)

    Gehlot, Mona, E-mail: mona_gehlot@yahoo.com [Insertion Device Development Laboratory, School of Physics, Devi Ahilya University, Indore 452001, MP (India); Mishra, G. [Insertion Device Development Laboratory, School of Physics, Devi Ahilya University, Indore 452001, MP (India); Institute of Engineering, UNAM (Mexico); Soleil, Paris (France); Trillaud, Frederic [Institute of Engineering, UNAM (Mexico); Sharma, Geetanjali [Soleil, Paris (France)

    2017-02-21

    In this paper we report the design of a 14 mm period prototype superconducting undulator that is under fabrication at Insertion Device Development Laboratory (IDDL) at Devi Ahilya Vishwavidyalaya, Indore, India. The field computations are made in RADIA and results are presented in an analytical form for computation of the on axis field and the field on the surface of the coil. On the basis of the findings, a best fit is presented for the model to calculate the field dependence on the gap and the current density. The fit is compared with Moser-Rossmanith formula proposed earlier to predict the magnetic flux density of a superconducting undulator. The field mapping is used to calculate the field integrals and its dependence on gap and current densities as well.

  19. Enhancing the design of a superconducting coil for magnetic energy storage systems

    International Nuclear Information System (INIS)

    Indira, Gomathinayagam; UmaMaheswaraRao, Theru; Chandramohan, Sankaralingam

    2015-01-01

    Highlights: • High magnetic flux density of SMES coil to reduce the size. • YBCO Tapes for the construction of HTS magnets. • Relation between energy storage and length of the coil wound by various materials. • Design with a certain length of second-generation HTS. - Abstract: Study and analysis of a coil for Superconducting Magnetic Energy Storage (SMES) system is presented in this paper. Generally, high magnetic flux density is adapted in the design of superconducting coil of SMES to reduce the size of the coil and to increase its energy density. With high magnetic flux density, critical current density of the coil is degraded and so the coil is wound with High Temperature Superconductors (HTS) made of different materials. A comparative study is made to emphasize the relationship between the energy storage and length of the coil wound by Bi2223, SF12100, SCS12100 and YBCO tapes. Recently for the construction of HTS magnets, YBCO tapes have been used. Simulation models for various designs have been developed to analyze the magnetic field distribution for the optimum design of energy storage. The design which gives the maximum stored energy in the coil has been used with a certain length of second-generation HTS. The performance analysis and the results of comparative study are done

  20. Enhancing the design of a superconducting coil for magnetic energy storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Indira, Gomathinayagam, E-mail: gindu80@gmail.com [EEE Department, Prince Shri Venkateshwara Padmavathy Engineering College, Chennai (India); UmaMaheswaraRao, Theru, E-mail: umesh.theru@gmail.com [Divison of Power Engineering and Management, Anna University, Chennai (India); Chandramohan, Sankaralingam, E-mail: cdramo@gmail.com [Divison of Power Engineering and Management, Anna University, Chennai (India)

    2015-01-15

    Highlights: • High magnetic flux density of SMES coil to reduce the size. • YBCO Tapes for the construction of HTS magnets. • Relation between energy storage and length of the coil wound by various materials. • Design with a certain length of second-generation HTS. - Abstract: Study and analysis of a coil for Superconducting Magnetic Energy Storage (SMES) system is presented in this paper. Generally, high magnetic flux density is adapted in the design of superconducting coil of SMES to reduce the size of the coil and to increase its energy density. With high magnetic flux density, critical current density of the coil is degraded and so the coil is wound with High Temperature Superconductors (HTS) made of different materials. A comparative study is made to emphasize the relationship between the energy storage and length of the coil wound by Bi2223, SF12100, SCS12100 and YBCO tapes. Recently for the construction of HTS magnets, YBCO tapes have been used. Simulation models for various designs have been developed to analyze the magnetic field distribution for the optimum design of energy storage. The design which gives the maximum stored energy in the coil has been used with a certain length of second-generation HTS. The performance analysis and the results of comparative study are done.

  1. Cryogenic techniques for large superconducting magnets in space

    International Nuclear Information System (INIS)

    Green, M.A.

    1988-12-01

    A large superconducting magnet is proposed for use in a particle astrophysics experiment, ASTROMAG, which is to be mounted on the United States Space Station. This experiment will have a two-coil superconducting magnet with coils which are 1.3 to 1.7 meters in diameter. The two-coil magnet will have zero net magnetic dipole moment. The field 15 meters from the magnet will approach earth's field in low earth orbit. The issue of high Tc superconductor will be discussed in the paper. The reasons for using conventional niobium-titanium superconductor cooled with superfluid helium will be presented. Since the purpose of the magnet is to do particle astrophysics, the superconducting coils must be located close to the charged particle detectors. The trade off between the particle physics possible and the cryogenic insulation around the coils is discussed. As a result, the ASTROMAG magnet coils will be operated outside of the superfluid helium storage tank. The fountain effect pumping system which will be used to cool the coil is described in the report. Two methods for extending the operating life of the superfluid helium dewar are discussed. These include: operation with a third shield cooled to 90 K with a sterling cycle cryocooler, and a hybrid cryogenic system where there are three hydrogen-cooled shields and cryostat support heat intercept points. Both of these methods will extend the ASTROMAG cryogenic operating life from 2 years to almost 4 years. 14 refs., 8 figs., 4 tabs

  2. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  3. The design, magnetization and control of a superconducting permanent magnet synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y; Pei, R; Xian, W; Hong, Z; Coombs, T A [Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)], E-mail: yj222@cam.ac.uk

    2008-06-15

    This paper describes in detail the method of magnetization of a superconducting permanent magnet synchronous motor. The rotor of the motor consists of 60 superconducting pucks, which are magnetized by two additional copper windings. The pulse field magnetization (PFM) method is considered and the resulted distribution of the magnetizing flux linkage from the rotor is not a perfect sine wave in the air gap, which leads to a large torque ripple and harmonics of the stator currents. In order to suppress the torque ripple, an iterative learning control (ILC) algorithm is used in addition to the former field-oriented control method. The results show the ILC algorithm can largely reduce the torque ripple.

  4. Peak Fields of Nb$_{3}$Sn Superconducting Undulators and a Scaling Law

    CERN Document Server

    Kim, S H

    2005-01-01

    The peak fields on the beam axis and the maximum fields in the conductor of Nb$_{3}$Sn superconducting undulators (SCUs) were calculated for an undulator period length of 16 mm. Using a simple scaling law for SCUs [1], the peak fields, as well as the conductor maximum fields and the current densities, were calculated for a period range of 8 to 32 mm. The critical current densities of commercially available Nb$_{3}$Sn superconducting strands were used for the calculations. The achievable peak fields are limited mainly by the flux-jump instabilities at low fields. The possible or feasible peak field will also be compared with that achieved in prototype development of SCUs.

  5. Synchronization of x-ray pulses to the pump laser in an ultrafast x-ray facility

    International Nuclear Information System (INIS)

    Corlett, J.N.; Barry, W.; Byrd, J.M.; Schoenlein, R.; Zholents, A.

    2002-01-01

    Accurate timing of ultrafast x-ray probe pulses emitted from a synchrotron radiation source with respect to a pump laser exciting processes in the sample under study is critical for the investigation of structural dynamics in the femtosecond regime. We describe a scheme for synchronizing femtosecond x-ray pulses relative to a pump laser. X-ray pulses of <100 fs duration are generated from a proposed source based on a recirculating superconducting linac [1,2,3]. Short x-ray pulses are obtained by a process of electron pulse compression, followed by transverse temporal correlation of the electrons, and ultimately x-ray pulse compression. Timing of the arrival of the x-ray pulse with respect to the pump laser is found to be dominated by the operation of the deflecting cavities which provide the transverse temporal correlation of the electrons. The deflecting cavities are driven from a highly stable RF signal derived from a modelocked laser oscillator which is also the origin of the pump l aser pulses

  6. Edge plasma control: Particle channeling in Tore Supra pump limiter and ergodic divertor

    International Nuclear Information System (INIS)

    Ghendrih, P.; Samain, A.; Grosman, A.; Capes, H.; Morera, J.P.

    1989-01-01

    Improved pumping efficiency can be achieved on Tore Supra by channeling process for particles, i.e. channeling of neutrals in the throat of pump limiters and channeling of plasma towards neutralizer plates in the ergodic divertor. The plugging length for the pump limiter throat is computed and numerical evidence of plasma flux channeling between the conductor bars of the ergodic divertor is presented. The effect of the Tore Supra ergodic divertor on edge plasma state and edge plasma transport is discussed. (orig.)

  7. Is the Ca2+-ATPase from sarcoplasmic reticulum also a heat pump?

    Science.gov (United States)

    Kjelstrup, Signe; de Meis, Leopoldo; Bedeaux, Dick; Simon, Jean-Marc

    2008-11-01

    We calculate, using the first law of thermodynamics, the membrane heat fluxes during active transport of Ca(2+) in the Ca(2+)-ATPase in leaky and intact vesicles, during ATP hydrolysis or synthesis conditions. The results show that the vesicle interior may cool down during hydrolysis and Ca(2+)-uptake, and heat up during ATP synthesis and Ca(2+)-efflux. The heat flux varies with the SERCA isoform. Electroneutral processes and rapid equilibration of water were assumed. The results are consistent with the second law of thermodynamics for the overall processes. The expression for the heat flux and experimental data, show that important contributions come from the enthalpy of hydrolysis for the medium in question, and from proton transport between the vesicle interior and exterior. The analysis give quantitative support to earlier proposals that certain, but not all, Ca(2+)-ATPases, not only act as Ca(2+)-pumps, but also as heat pumps. It can thus help explain why SERCA 1 type enzymes dominate in tissues where thermal regulation is important, while SERCA 2 type enzymes, with their lower activity and better ability to use the energy from the reaction to pump ions, dominate in tissues where this is not an issue.

  8. Hysteresis of critical currents of superconducting bridges in low perpendicular magnetic fields

    International Nuclear Information System (INIS)

    Aomine, T.; Tanaka, E.; Yamasaki, S.; Tani, K.; Yonekura, A.

    1989-01-01

    Hysteresis of critical currents I c of superconducting bridges with In, Nb, and NbN has been studied in low perpendicular magnetic fields. Influences of bridge geometry, small field sweep, trapped flux, and bombardment of argon ions on the hysteresis were made clear. The experimental results suggest that the edge pinning and trapped flux in the bank of bridges are associated with the hysteresis. The peak value of I c of NbN bridges, as well as granular Al and In bridges reported before, in decreasing fields agrees with the calculated pair-breaking current. The origin of the hysteresis is discussed

  9. Superconductivity revisited

    CERN Document Server

    Dougherty, Ralph

    2013-01-01

    While the macroscopic phenomenon of superconductivity is well known and in practical use worldwide in many industries, including MRIs in medical diagnostics, the current theoretical paradigm for superconductivity (BCS theory) suffers from a number of limitations, not the least of which is an adequate explanation of high temperature superconductivity. This book reviews the current theory and its limitations and suggests new ideas and approaches in addressing these issues. The central objective of the book is to develop a new, coherent, understandable theory of superconductivity directly based on molecular quantum mechanics.

  10. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  11. Plugging regime in the pump limiter throat

    International Nuclear Information System (INIS)

    Ghendrih, P.; Grosman, A.; Samain, A.; Capes, H.; Morera, J.P.

    1988-08-01

    The plugging regime -with no outstreaming neutral flux- is studied for a closed configuration pump limiter (throat). We derive the plugging length and the neutral density build-up at the neutralizer plate. The analytical expressions are supported by numerical evidence. We find an improved efficiency related to the throat effect mainly due to neutral-sidewall interactions

  12. Proceedings of the fourth international conference and exhibition: World Congress on superconductivity. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Krishen, K.; Burnham, C. [eds.] [National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center

    1994-12-31

    This document contains papers presented at the 4th International Conference Exhibition: World Congress on Superconductivity held at the Marriott Orlando World Center, Orlando, Florida, June 27--July 1, 1994. This conference encompassed research, technology, applications, funding, political, and social aspects of superconductivity. Specifically, the areas of research, technology, and development covered during the conference included high-temperature materials, thin films, C-60 based superconductors, persistent magnetic fields and shielding, fabrication methodology, space applications, physical applications, performance characterization, device applications, weak link effects and flux motion, accelerator technology, superconductivity energy, storage, future research and development directions, medical applications, granular superconductors, wire fabrication technology, computer applications, technical and commercial challenges, and power and energy applications. The key objective of this conference was to provide a forum for the world community to share technological results of recent advances made in the field of superconductivity and to discuss translation of the research to technology which will benefit humanity. More than 150 presentations were made at this conference. Individual papers are indexed separately on the Energy Data Bases.

  13. Proceedings of the fourth international conference and exhibition: World Congress on superconductivity. Volume 2

    International Nuclear Information System (INIS)

    Krishen, K.; Burnham, C.

    1994-01-01

    This document contains papers presented at the 4th International Conference Exhibition: World Congress on Superconductivity held at the Marriott Orlando World Center, Orlando, Florida, June 27--July 1, 1994. This conference encompassed research, technology, applications, funding, political, and social aspects of superconductivity. Specifically, the areas of research, technology, and development covered during the conference included high-temperature materials, thin films, C-60 based superconductors, persistent magnetic fields and shielding, fabrication methodology, space applications, physical applications, performance characterization, device applications, weak link effects and flux motion, accelerator technology, superconductivity energy, storage, future research and development directions, medical applications, granular superconductors, wire fabrication technology, computer applications, technical and commercial challenges, and power and energy applications. The key objective of this conference was to provide a forum for the world community to share technological results of recent advances made in the field of superconductivity and to discuss translation of the research to technology which will benefit humanity. More than 150 presentations were made at this conference. Individual papers are indexed separately on the Energy Data Bases

  14. Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch

    International Nuclear Information System (INIS)

    Hoffmann, Elisabeth Christiane Maria

    2013-01-01

    The field of cavity quantum electrodynamics (QED) studies the interaction between light and matter on a fundamental level. In typical experiments individual natural atoms are interacting with individual photons trapped in three-dimensional cavities. Within the last decade the prospering new field of circuit QED has been developed. Here, the natural atoms are replaced by artificial solid state quantum circuits offering large dipole moments which are coupled to quasi-onedimensional cavities providing a small mode volume and hence a large vacuum field strength. In our experiments Josephson junction based superconducting quantum bits are coupled to superconducting microwave resonators. In circuit QED the number of parameters that can be varied is increased and regimes that are not accessible using natural atoms can be entered and investigated. Apart from design flexibility and tunability of system parameters a particular advantage of circuit QED is the scalability to larger system size enabled by well developed micro- and nanofabrication tools. When scaling up the resonator-qubit systems beyond a few coupled circuits, the rapidly increasing number of interacting subsystems requires an active control and directed transmission of quantum signals. This can, for example, be achieved by implementing switchable coupling between two microwave resonators. To this end, a superconducting flux qubit is used to realize a suitable coupling between two microwave resonators, all working in the Gigahertz regime. The resulting device is called quantum switch. The flux qubit mediates a second order tunable and switchable coupling between the resonators. Depending on the qubit state, this coupling can compensate for the direct geometric coupling of the two resonators. As the qubit may also be in a quantum superposition state, the switch itself can be ''quantum'': it can be a superposition of ''on'' and ''off''. This work presents the theoretical background, the fabrication techniques and

  15. Air-lift pumps characteristics under two-phase flow conditions

    International Nuclear Information System (INIS)

    Kassab, Sadek Z.; Kandil, Hamdy A.; Warda, Hassan A.; Ahmed, Wael H.

    2009-01-01

    Air-lift pumps are finding increasing use where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids in nuclear applications must be handled and when a compressed air is readily available as a source of a renewable energy for water pumping applications. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters. For this purpose, an air-lift pump was designed and tested. Experiments were performed for nine submergence ratios, and three risers of different lengths with different air injection pressures. Moreover, the pump was tested under different two-phase flow patterns. A theoretical model is proposed in this study taking into account the flow patterns at the best efficiency range where the pump is operated. The present results showed that the pump capacity and efficiency are functions of the air mass flow rate, submergence ratio, and riser pipe length. The best efficiency range of the air-lift pumps operation was found to be in the slug and slug-churn flow regimes. The proposed model has been compared with experimental data and the most cited models available. The proposed model is in good agreement with experimental results and found to predict the liquid volumetric flux for different flow patterns including bubbly, slug and churn flow patterns

  16. Physical properties in flux line lattice state in MgB2 probed by μSR

    International Nuclear Information System (INIS)

    Ohishi, Kazuki; Muranaka, Takahiro; Akimitsu, Jun; Koda, Akihiro; Higemoto, Wataru; Kadono, Ryosuke

    2002-01-01

    We have performed muon spin rotation (μSR) measurements to deduce the magnetic penetration depth λ in the flux line lattice state of MgB 2 microscopically. It is observed that λ shows a quadratic temperature dependence which is predicted for the case of superconducting gap with line nodes. Furthermore, it clearly exhibits a strong field dependence, where λ increases almost linearly with H. These results strongly suggest that the superconducting order parameter in MgB 2 is highly anisotropic. (author)

  17. Characterization of double-loop four-Josephson-junction flux qubit

    International Nuclear Information System (INIS)

    Shimazu, Y.; Saito, Y.; Wada, Z.

    2009-01-01

    An advantage of a double-loop four-Josephson-junction (4-JJ) flux qubit is the tunability of the energy gap at a symmetry point, i.e., the point at which the double-well potential of the qubit is symmetric. The energy gap is controlled via the magnetic flux in a DC superconducting quantum interference device (DC-SQUID) loop incorporated in a 4-JJ qubit. We investigate the locus of the symmetry point in the plane of two control fluxes of the qubit, taking into account the asymmetry in the DC-SQUID, which is inevitable in practical cases. The observed positions of the qubit steps are in reasonable agreement with the calculated locus of the symmetry point. We estimate the asymmetry parameter of the DC-SQUID from this analysis.

  18. Local Magnetic Measurements of Trapped Flux Through a Permanent Current Path in Graphite

    Science.gov (United States)

    Stiller, Markus; Esquinazi, Pablo D.; Quiquia, José Barzola; Precker, Christian E.

    2018-04-01

    Temperature- and field-dependent measurements of the electrical resistance of different natural graphite samples suggest the existence of superconductivity at room temperature in some regions of the samples. To verify whether dissipationless electrical currents are responsible for the trapped magnetic flux inferred from electrical resistance measurements, we localized them using magnetic force microscopy on a natural graphite sample in remanent state after applying a magnetic field. The obtained evidence indicates that at room temperature a permanent current flows at the border of the trapped flux region. The current path vanishes at the same transition temperature T_c≈ 370 K as the one obtained from electrical resistance measurements on the same sample. This sudden decrease in the phase is different from what is expected for a ferromagnetic material. Time-dependent measurements of the signal show the typical behavior of flux creep of a permanent current flowing in a superconductor. The overall results support the existence of room-temperature superconductivity at certain regions in the graphite structure and indicate that magnetic force microscopy is suitable to localize them. Magnetic coupling is excluded as origin of the observed phase signal.

  19. Superconductivity in Medicine

    Science.gov (United States)

    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.

  20. Quantum information storage using tunable flux qubits

    Energy Technology Data Exchange (ETDEWEB)

    Steffen, Matthias; Brito, Frederico; DiVincenzo, David; Farinelli, Matthew; Keefe, George; Ketchen, Mark; Kumar, Shwetank; Milliken, Frank; Rothwell, Mary Beth; Rozen, Jim; Koch, Roger H, E-mail: msteffe@us.ibm.co [IBM Watson Research Center, Yorktown Heights, NY 10598 (United States)

    2010-02-10

    We present details and results for a superconducting quantum bit (qubit) design in which a tunable flux qubit is coupled strongly to a transmission line. Quantum information storage in the transmission line is demonstrated with a dephasing time of T{sub 2}approx2.5 mus. However, energy lifetimes of the qubit are found to be short (approx10 ns) and not consistent with predictions. Several design and material changes do not affect qubit coherence times. In order to determine the cause of these short coherence times, we fabricated standard flux qubits based on a design which was previously successfully used by others. Initial results show significantly improved coherence times, possibly implicating losses associated with the large size of our qubit. (topical review)

  1. Interplay of dendritic avalanches and gradual flux penetration in superconducting MgB2 films

    International Nuclear Information System (INIS)

    Shantsev, D V; Goa, P E; Barkov, F L; Johansen, T H; Kang, W N; Lee, S I

    2003-01-01

    Magneto-optical imaging was used to study a zero-field-cooled MgB 2 film at 9.6 K where in a slowly increasing field the flux penetrates by an abrupt formation of large dendritic structures. Simultaneously, a gradual flux penetration takes place, eventually covering the dendrites, and a detailed analysis of this process is reported. We find an anomalously high gradient of the flux density across a dendrite branch, and a peak value that decreases as the applied field increases. This unexpected behaviour is reproduced by flux creep simulations based on the non-local field-current relation in the perpendicular geometry. The simulations also provide indirect evidence that flux dendrites are formed at an elevated local temperature, consistent with a thermo-magnetic mechanism of the instability

  2. Zurek–Kibble Symmetry Breaking Process in Superconducting Rings; Spontaneous Fluxon Formation in Annular Josephson Tunnel Junctions

    DEFF Research Database (Denmark)

    Aarøe, Morten; Monaco, Roberto; Dmitriev, P

    2007-01-01

    We report on new investigations of spontaneous symmetry breaking in non-adiabatic phase transitions. This Zurek-Kibble (ZK) process is mimicked in solid state systems by trapping of magnetic flux quanta, fluxons, in a long annular Josephson tunnel junction quenched through the normal-superconducting...

  3. Numerical Analysis of Rotating Pumping Flows in Inter-Coil Rotor Cavities and Short Cooling Grooves of a Generator

    Directory of Open Access Journals (Sweden)

    Wei Tong

    2001-01-01

    Full Text Available An important characteristic of wall rotating-driven flows is the tendency of fluid with high angular momentum to be flung radially outward. For a generator, the rotor rotating-driven flow, usually referred to as the rotating pumping flow, plays an important role in rotor winding cooling. In this study, three-dimensional numerical analyzes are presented for turbulent pumping flow in the inter-coil rotor cavity and short cooling grooves of a generator. Calculations of the flow field and the mass flux distribution through the grooves were carried out in a sequence of four related cases Under an isothermal condition: (a pumping flow, which is the self-generated flow resulted from the rotor pumping action; (b mixing flow, which is the combination of the ventilating flow and pumping flow, under a constant density condition; (c mixing flow, with density modeled by the ideal gas law; and (d mixing flow, with different pressure differentials applied on the system. The comparisons of the results from these cases can provide useful information regarding the impacts of the ventilating flow, gas density, and system pressure differential on the mass flux distribution in the short cooling grooves. Results show that the pumping effect is strong enough to generate the cooling flow for rotor winding cooling. Therefore, for small- or mid-size generators ventilation fans may be eliminated. It also suggests that increasing the chimney dimension can improve the distribution uniformity of mass flux through the cooling grooves.

  4. Sodium pumping: pump problems

    International Nuclear Information System (INIS)

    Guer, M.; Guiton, P.

    Information on sodium pumps for LMFBR type reactors is presented concerning ring pump design, pool reactor pump design, secondary pumps, sodium bearings, swivel joints of the oscillating annulus, and thermal shock loads

  5. Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

    Science.gov (United States)

    Liarte, Danilo B.; Posen, Sam; Transtrum, Mark K.; Catelani, Gianluigi; Liepe, Matthias; Sethna, James P.

    2017-03-01

    Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-T c materials such as Nb3Sn, NbN, and MgB2. Indeed, beyond the so-called superheating field {H}{sh}, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for {H}{sh}, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB2? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.

  6. Surface flux density distribution characteristics of bulk high-T c superconductor in external magnetic field

    International Nuclear Information System (INIS)

    Nishikawa, H.; Torii, S.; Yuasa, K.

    2005-01-01

    This paper describes the measured results of the two-dimensional flux density distribution of a YBCO bulk under applied AC magnetic fields with various frequency. Melt-processed oxide superconductors have been developed in order to obtain strong pinning forces. Various electric mechanical systems or magnetic levitation systems use those superconductors. The major problem is that cracks occur because the bulk superconductors are brittle. The bulk may break in magnetizing process after cracks make superconducting state instable. The trapped flux density and the permanent current characteristics of bulk superconductors have been analyzed, so as to examine the magnetizing processes or superconducting states of the bulk. In those studies, the two-dimensional surface flux density distributions of the bulk in static fields are discussed. On the other hand, the distributions in dynamic fields are little discussed. We attempted to examine the states of the bulk in the dynamic fields, and made a unique experimental device which has movable sensors synchronized with AC applied fields. As a result, the two-dimensional distributions in the dynamic fields are acquired by recombining the one-dimensional distributions. The dynamic states of the flux of the bulk and the influences of directions of cracks are observed from the distributions. In addition, a new method for measuring two-dimensional flux density distribution under dynamic magnetic fields is suggested

  7. Superconductivity in technology

    International Nuclear Information System (INIS)

    Komarek, P.

    1976-01-01

    Physics, especially high energy physics and solid state physics was the first area in which superconducting magnets were used but in the long run, the most extensive application of superconductivity will probably be in energy technology. Superconducting power transmission cables, magnets for energy conversion in superconducting electrical machines, MHD-generators and fusion reactors and magnets for energy storage are being investigated. Magnets for fusion reactors will have particularly large physical dimensions, which means that much development effort is still needed, for there is no economic alternative. Superconducting surfaces in radio frequency cavities can give Q-values up to a factor of 10 6 higher than those of conventional resonators. Particle accelerators are the important application. And for telecommunication, simple coaxial superconducting radio frequency cables seem promising. The tunnel effect in superconducting junctions is now being developed commercially for sensitive magnetometers and may soon possibly feature in the memory cells of computer devices. Hence superconductivity can play an important role in the technological world, solving physical and technological problems and showing economic advantages as compared with possible conventional techniques, bearing also in mind the importance of reliability and safety. (author)

  8. Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around T{sub c}

    Energy Technology Data Exchange (ETDEWEB)

    Romanenko, A., E-mail: aroman@fnal.gov; Grassellino, A., E-mail: annag@fnal.gov; Melnychuk, O.; Sergatskov, D. A. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

    2014-05-14

    We report a strong effect of the cooling dynamics through T{sub c} on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120 °C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance, while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.

  9. Analysis of pumping-induced unsaturated regions beneath aperennial river

    Energy Technology Data Exchange (ETDEWEB)

    Su, G.W.; Jasperse, J.; Seymour, D.; Constantz, J.; Zhou, Q.

    2007-05-15

    The presence of an unsaturated region beneath a streambedduring groundwater pumping near streams reduces the pumping capacity whenit reaches the well screens, changes flow paths, and alters the types ofbiological transformations in the streambed sediments. Athree-dimensional, multi-phase flow model of two horizontal collectorwells along the Russian River near Forestville, California was developedto investigate the impact of varying the ratio of the aquifer tostreambed permeability on (1) the formation of an unsaturated regionbeneath the stream, (2) the pumping capacity, (3) stream-water fluxesthrough the streambed, and (4) stream-water travel times to the collectorwells. The aquifer to streambed permeability ratio at which theunsaturated region was initially observed ranged from 10 to 100. The sizeof the unsaturated region beneath the streambed increased as the aquiferto streambed permeability ratio increased. The simulations also indicatedthat for a particular aquifer permeability, decreasing the streambedpermeability by only a factor of 2-3 from the permeability wheredesaturation initially occurred resulted in reducing the pumpingcapacity. In some cases, the stream-water fluxes increased as thestreambed permeability decreased. However, the stream water residencetimes increased and the fraction of stream water that reached that thewells decreased as the streambed permeability decreased, indicating thata higher streambed flux does not necessarily correlate to greaterrecharge of stream water around the wells.

  10. Component and system simulation models for High Flux Isotope Reactor

    International Nuclear Information System (INIS)

    Sozer, A.

    1989-08-01

    Component models for the High Flux Isotope Reactor (HFIR) have been developed. The models are HFIR core, heat exchangers, pressurizer pumps, circulation pumps, letdown valves, primary head tank, generic transport delay (pipes), system pressure, loop pressure-flow balance, and decay heat. The models were written in FORTRAN and can be run on different computers, including IBM PCs, as they do not use any specific simulation languages such as ACSL or CSMP. 14 refs., 13 figs

  11. Development for LMR coolant technology - Development of a submersible-in-pool electromagnetic pump

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sang Hee; Kim, Hee Reyoung; Lee, Sang Don; Seo, Chun Ho [Seoul National University, Seoul (Korea, Republic of); Cho, Su Won [Kyungki University, Suwon (Korea, Republic of)

    1995-08-01

    The conceptual and detailed designs of an annular linear induction electromagnetic pump of small scale submersible-in-pool type are performed for the purpose of domestic development of the pumps used for the high-temperature natrium coolant transportation in liquid metal reactors. The pump drawings for and input power of 1,100 VA, an input frequency of 17 Hz, a maximum flowrate of 60 l/min and a maximum operation temperature of 600 deg C are obtained from the optimum design analyses by solving MHD and equivalent circuit equations. The characteristics of pump materials in the high temperature and neutron irradiation environment are reflected in designing the pump, and theoretical analyses for improving the pump performance and efficiency are tried through calculations of magnetic flux and temperature distributions inside the pump. The present project contributes to the further design of engineering proto-type electromagnetic pump with higher capacity and the development of liquid metal reactor with innovative simplicity. 44 refs., 4 tabs., 33 figs. (author)

  12. Synthesis, properties and space applications of chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting powders

    International Nuclear Information System (INIS)

    Trivedi, A.; Sundahl, R.C.; Olson, W.L.; Welsh, L.B.; Polak, A.J.; Dolgin, B.P.; Barder, T.J.; Karasek, K.R.; Parker, C.A.

    1988-01-01

    Processing properties of and chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders were evaluated. The authors have successfully developed a method for precipitating stoichiometric oxalate precursors for YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders. Precipitation and calcination conditions were found to dramatically impact upon key powder characteristics such as particle size, morphology, phase composition and microscopic homogeneity. Four space applications were identified: a superconducting motor/generator, a magnetic bearing, an electromagnetic coupling, and a motor commutator. The primary device, a motor, would make use of superconducting windings and a superconducting flux bottle to improve efficiency

  13. High temperature superconducting compounds II; Proceedings of the Second Symposium, Anaheim, CA, Feb. 20, 21, 1990

    International Nuclear Information System (INIS)

    Whang, S.H.; Dasgupta, A.; Laibowitz, R.

    1990-01-01

    Various topics relevant to the production and implementation of high-temperature superconducting compounds are highlighted including critical current; texturing; ceramics and novel processing; composites; deformation and consolidation; thin films; microstructures; tapes, filaments, and ribbons; and thermodynamics. The thermally activated flux creep, critical current density and current enhancement in high-temperature superconductors are addressed. Also discussed are the phase stability and microstructure of doped superconductors, mechanical considerations in the processing of high-Tc superconductors, fabrication and application of high current density, high RTc superconducting thin films and devices, the effect of substrate temperature and RF biasing on the composition of sputtered Bi-based superconducting thin films, and optical electron microanalysis of cuprate superconductors. The microstructure dependence of critical current density and fabrication of double-layered ribbons from cuprate are also discussed

  14. Superconductivity of tin and lead after heavy ion irradiation below 7.2 K

    International Nuclear Information System (INIS)

    Klaumuenzer, S.

    1978-01-01

    In this work the influence of radiation defects induced by heavy ion irradiation at low temperatures on the specific residual resistivity, the critical temperature of superconductivity, and the width of the resistive-superconductive phase transition have been measured for lead and tin as a function of dose and subsequent isochronous annealing. In the case of lead the critical magnetic field parallel to the surface of the sample, which in a wide range of defect contrations is identical with the surface superconductivity critical field, also has been measured at 5 K and 6 K as a function of dose and subsequent isochronous annealing. As projectiles 25 MeV oxygen ions have been used for irradiation, with a sufficiently low particle flux to obtain irradiation temperatures below about 7.2 K. However these temperatures are large enough to allow for free motion of interstitial atoms in the case of lead. For tin the results presented here also suggest free motion of the defects. (orig./WBU) [de

  15. Magnetic shielding for superconducting RF cavities

    Science.gov (United States)

    Masuzawa, M.; Terashima, A.; Tsuchiya, K.; Ueki, R.

    2017-03-01

    Magnetic shielding is a key technology for superconducting radio frequency (RF) cavities. There are basically two approaches for shielding: (1) surround the cavity of interest with high permeability material and divert magnetic flux around it (passive shielding); and (2) create a magnetic field using coils that cancels the ambient magnetic field in the area of interest (active shielding). The choice of approach depends on the magnitude of the ambient magnetic field, residual magnetic field tolerance, shape of the magnetic shield, usage, cost, etc. However, passive shielding is more commonly used for superconducting RF cavities. The issue with passive shielding is that as the volume to be shielded increases, the size of the shielding material increases, thereby leading to cost increase. A recent trend is to place a magnetic shield in a cryogenic environment inside a cryostat, very close to the cavities, reducing the size and volume of the magnetic shield. In this case, the shielding effectiveness at cryogenic temperatures becomes important. We measured the permeabilities of various shielding materials at both room temperature and cryogenic temperature (4 K) and studied shielding degradation at that cryogenic temperature.

  16. Model of a thermal energy storage device integrated into a solar assisted heat pump system for space heating

    International Nuclear Information System (INIS)

    Badescu, Viorel

    2003-01-01

    Details about modelling a sensible heat thermal energy storage (TES) device integrated into a space heating system are given. The two main operating modes are described. Solar air heaters provide thermal energy for driving a vapor compression heat pump. The TES unit ensures a more efficient usage of the collected solar energy. The TES operation is modeled by using two non-linear coupled partial differential equations for the temperature of the storage medium and heat transfer fluid, respectively. Preliminary results show that smaller TES units provide a higher heat flux to the heat pump vaporiser. This makes the small TES unit discharge more rapidly during time periods with higher thermal loads. The larger TES units provide heat during longer time periods, even if the heat flux they supply is generally smaller. The maximum heat flux is extracted from the TES unit during the morning. Both the heat pump COP and exergy efficiency decrease when the TES unit length increases. Also, the monthly thermal energy stored by the TES unit and the monthly energy necessary to drive the heat pump compressor are increased by increasing the TES unit length

  17. Storage and on-demand release of microwaves using superconducting resonators with tunable coupling

    International Nuclear Information System (INIS)

    Pierre, Mathieu; Svensson, Ida-Maria; Raman Sathyamoorthy, Sankar; Johansson, Göran; Delsing, Per

    2014-01-01

    We present a system which allows to tune the coupling between a superconducting resonator and a transmission line. This storage resonator is addressed through a second, coupling resonator, which is frequency-tunable and controlled by a magnetic flux applied to a superconducting quantum interference device. We experimentally demonstrate that the lifetime of the storage resonator can be tuned by more than three orders of magnitude. A field can be stored for 18 μs when the coupling resonator is tuned off resonance and it can be released in 14 ns when the coupling resonator is tuned on resonance. The device allows capture, storage, and on-demand release of microwaves at a tunable rate.

  18. Bridging the Gap for High-Coherence, Strongly Coupled Superconducting Qubits

    Science.gov (United States)

    Yoder, Jonilyn; Kim, David; Baldo, Peter; Day, Alexandra; Fitch, George; Holihan, Eric; Hover, David; Samach, Gabriel; Weber, Steven; Oliver, William

    Crossovers can play a critical role in increasing superconducting qubit device performance, as long as device coherence can be maintained even with the increased fabrication and circuit complexity. Specifically, crossovers can (1) enable a fully-connected ground plane, which reduces spurious modes and crosstalk in the circuit, and (2) increase coupling strength between qubits by facilitating interwoven qubit loops with large mutual inductances. Here we will describe our work at MIT Lincoln Laboratory to integrate superconducting air bridge crossovers into the fabrication of high-coherence capacitively-shunted superconducting flux qubits. We will discuss our process flow for patterning air bridges by resist reflow, and we will describe implementation of air bridges within our circuits. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) and by the Assistant Secretary of Defense for Research and Engineering under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  19. Quench-Induced Degradation of the Quality Factor in Superconducting Resonators

    Science.gov (United States)

    Checchin, M.; Martinello, M.; Romanenko, A.; Grassellino, A.; Sergatskov, D. A.; Posen, S.; Melnychuk, O.; Zasadzinski, J. F.

    2016-04-01

    Quench of superconducting radio-frequency cavities frequently leads to the lowered quality factor Q0 , which had been attributed to the additional trapped magnetic flux. Here we demonstrate that the origin of this magnetic flux is purely extrinsic to the cavity by showing no extra dissipation (unchanged Q0) after quenching in zero magnetic field, which allows us to rule out intrinsic mechanisms of flux trapping such as generation of thermal currents or trapping of the rf field. We also show the clear relation of dissipation introduced by quenching to the orientation of the applied magnetic field and the possibility to fully recover the quality factor by requenching in the compensated field. We discover that for larger values of the ambient field, the Q -factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during quench. Our findings are of special practical importance for accelerators based on low- and medium-β accelerating structures residing close to focusing magnets, as well as for all high-Q cavity-based accelerators.

  20. Impurity Content Optimization to Maximize Q-Factors of Superconducting Resonators

    Energy Technology Data Exchange (ETDEWEB)

    Martinello, Martina [Fermilab; Checchin, Mattia [IIT, Chicago; Grassellino, Anna [Fermilab; Melnychuk, Oleksandr [Fermilab; Posen, Sam [Fermilab; Romanenko, Alexander [Fermilab; Sergatskov, Dmitri [Fermilab; Zasadzinski, John [IIT, Chicago (main)

    2017-05-01

    Quality factor of superconducting radio-frequency (SRF) cavities is degraded whenever magnetic flux is trapped in the cavity walls during the cooldown. In this contribution we study how the trapped flux sensitivity, defined as the trapped flux surface resistance normalized for the amount of trapped flux, depends on the mean free path. A systematic study of a variety of 1.3 GHz cavities with different surface treatments (EP, 120 C bake and different N-doping) is carried out. A bell shaped trend appears for the range of mean free path studied. Over-doped cavities fall at the maximum of this curve defining the largest values of sensitivity. In addition, we have studied the trend of the BCS surface resistance contribution as a function of mean free path, showing that N-doped cavities follow close to the theoretical minimum. Adding these results together we show that the 2/6 N-doping treatment gives the highest Q-factor values at 2 K and 16 MV/m, as long as the magnetic field fully trapped during the cavity cooldown is lower than 10 mG.

  1. Aperiodic superconducting phase boundary of periodic micronetworks in a magnetic field

    International Nuclear Information System (INIS)

    Nori, F.; Niu, Q.

    1988-01-01

    We study flux quantization in periodic arrays with two elementary cells having an irrational ratio of areas. In particular, we calculate the superconducting-normal phase boundary T/sub c/(H) and we analyze the origin of its overall and fine structure as a function of the network size. We discuss our theoretical results, exploiting the electronic tight-binding analogy to the Ginzburg-Landau equations, and compare them with the experimental ones

  2. Liquid Hydrogen Recirculation System for Forced Flow Cooling Test of Superconducting Conductors

    Science.gov (United States)

    Shirai, Y.; Kainuma, T.; Shigeta, H.; Shiotsu, M.; Tatsumoto, H.; Naruo, Y.; Kobayashi, H.; Nonaka, S.; Inatani, Y.; Yoshinaga, S.

    2017-12-01

    The knowledge of forced flow heat transfer characteristics of liquid hydrogen (LH2) is important and necessary for design and cooling analysis of high critical temperature superconducting devices. However, there are few test facilities available for LH2 forced flow cooling for superconductors. A test system to provide a LH2 forced flow (∼10 m/s) of a short period (less than 100 s) has been developed. The test system was composed of two LH2 tanks connected by a transfer line with a controllable valve, in which the forced flow rate and its period were limited by the storage capacity of tanks. In this paper, a liquid hydrogen recirculation system, which was designed and fabricated in order to study characteristics of superconducting cables in a stable forced flow of liquid hydrogen for longer period, was described. This LH2 loop system consists of a centrifugal pump with dynamic gas bearings, a heat exchanger which is immersed in a liquid hydrogen tank, and a buffer tank where a test section (superconducting wires or cables) is set. The buffer tank has LHe cooled superconducting magnet which can produce an external magnetic field (up to 7T) at the test section. A performance test was conducted. The maximum flow rate was 43.7 g/s. The lowest temperature was 22.5 K. It was confirmed that the liquid hydrogen can stably circulate for 7 hours.

  3. Twisting Anderson pseudospins with light: Quench dynamics in terahertz-pumped BCS superconductors

    Science.gov (United States)

    Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew S.

    2017-03-01

    We study the preparation (pump) and the detection (probe) of far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment [R. Matsunaga, Y. I. Hamada, K. Makise, Y. Uzawa, H. Terai, Z. Wang, and R. Shimano, Phys. Rev. Lett. 111, 057002 (2013), 10.1103/PhysRevLett.111.057002], an intense monocycle THz pulse with center frequency ω ≃Δ was injected into a superconductor with BCS gap Δ ; the subsequent postpump evolution was detected via the optical conductivity. It was argued that nonlinear coupling of the pump to the Anderson pseudospins of the superconductor induces coherent dynamics of the Higgs (amplitude) mode Δ (t ) . We validate this picture in a two-dimensional BCS model with a combination of exact numerics and the Lax reduction method, and we compute the nonequilibrium phase diagram as a function of the pump intensity. The main effect of the pump is to scramble the orientations of Anderson pseudospins along the Fermi surface by twisting them in the x y plane. We show that more intense pump pulses can induce a far-from-equilibrium phase of gapless superconductivity ("phase I"), originally predicted in the context of interaction quenches in ultracold atoms. We show that the THz pump method can reach phase I at much lower energy densities than an interaction quench, and we demonstrate that Lax reduction (tied to the integrability of the BCS Hamiltonian) provides a general quantitative tool for computing coherent BCS dynamics. We also calculate the Mattis-Bardeen optical conductivity for the nonequilibrium states discussed here.

  4. Pumps and pump facilities. 2. ed.

    International Nuclear Information System (INIS)

    Bohl, W.; Bauerfeind, H.; Gutmann, G.; Leuschner, G.; Matthias, H.B.; Mengele, R.; Neumaier, R.; Vetter, G.; Wagner, W.

    1981-01-01

    This book deals with the common fundamental aspects of liquid pumps and gives an exemplary choice of the most important kinds of pumps. The scientific matter is dealt with by means of practical mathematical examples among other ways of presenting the matter. Survey of contents: Division on main operational data of pumps - pipe characteristics - pump characteristics - suction behaviour of the pumps - projecting and operation of rotary pumps - boiler feed pumps - reactor feed pumps - oscillating positive-displacement pumps - eccentric spiral pumps. (orig./GL) [de

  5. Test report for run-in acceptance testing of Project W-151 300 HP mixing pumps

    International Nuclear Information System (INIS)

    Berglin, B.G.

    1998-01-01

    This report documents the results of a performance demonstration and operational checkout of three 300 HP mixer pumps in accordance with WHC-SD-WI51-TS-001 ''Mixer Pump Test Specification for Project W-151'' and Statement of Work 8K520-EMN-95-004 ''Mixer Pump Performance Demonstration at MASF'' in the 400 Area Maintenance and Storage Facility (MASF) building. Testing of the pumps was performed by Fast Flux Test Facility (FFTF) Engineering and funded by the Tank Waste Remediation System (TWRS) Project W-151. Testing began with the first pump on 04-01-95 and ended with the third pump on 11-01-96. Prior to testing, the MASF was modified and prepared to meet the pump testing requirements set forth by the Test Specification and the Statement of Work

  6. Time-resolved X-ray diffraction study on superconducting YBa{sub 2}Cu{sub 3}O{sub 7} epitaxially grown on SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Luebcke, A.

    2007-07-01

    In this PhD thesis time-resolved X-ray diffraction in optical pump - X-ray probe scheme was applied for the first time to a High-Temperature Superconductor in the superconducting state. The aim was to study the possible lattice response to optical Cooper pair breaking. As sample a thin YBa{sub 2}Cu{sub 3}O{sub 7} film with a superconducting transition temperature of T{sub c}=90 K, epitaxially grown on a SrTiO{sub 3} single crystal was used. (orig.)

  7. Pinning of a curved flux line by macroscopic inclusions in a type II superconductor

    International Nuclear Information System (INIS)

    Shehata, L.N.; Saif, A.G.

    1983-08-01

    The pinning force is calculated as a function of the distance between a curved (or straight) flux line and the centre of a macroscopic superconducting (or normal) ellipsoidal inclusion. When the ellipsoidal tends to a spherical inclusion the results agree with those previously obtained. (author)

  8. Superconductivity program for electric systems, Superconductivity Technology Center, Los Alamos National Laboratory, annual progress report for fiscal year 1997

    Energy Technology Data Exchange (ETDEWEB)

    Willis, J.O.; Newnam, B.E. [eds.; Peterson, D.E.

    1999-03-01

    Development of high-temperature superconductors (HTS) has undergone tremendous progress during the past year. Kilometer tape lengths and associated magnets based on BSCCO materials are now commercially available from several industrial partners. Superconducting properties in the exciting YBCO coated conductors continue to be improved over longer lengths. The Superconducting Partnership Initiative (SPI) projects to develop HTS fault current limiters and transmission cables have demonstrated that HTS prototype applications can be produced successfully with properties appropriate for commercial applications. Research and development activities at LANL related to the HTS program for Fiscal Year 1997 are collected in this report. LANL continues to support further development of Bi2223 and Bi2212 tapes in collaboration with American Superconductor Corporation (ASC) and Oxford Superconductivity Technology, Inc. (OSTI), respectively. The tape processing studies involving novel thermal treatments and microstructural characterization have assisted these companies in commercializing these materials. The research on second-generation YBCO-coated conductors produced by pulsed-laser deposition (PLD) over buffer template layers produced by ion beam-assisted deposition (IBAD) continues to lead the world. The applied physics studies of magnetic flux pinning by proton and heavy ion bombardment of BSCCO and YBCO tapes have provided many insights into improving the behavior of these materials in magnetic fields. Sections 4 to 7 of this report contain a list of 29 referred publications and 15 conference abstracts, a list of patent and license activities, and a comprehensive list of collaborative agreements in progress and completed.

  9. Structural features that optimize high temperature superconductivity

    International Nuclear Information System (INIS)

    Jorgensen, J.D.; Hinks, D.G. Chmaissem, O.; Argyriou, D.N.; Mitchell, J.F.; Dabrowski, B.

    1996-01-01

    For example, various defects can be introduced into the blocking layer to provide the optimum carrier concentration, but defects that form in or adjacent to the CuO 2 layers will lower T c and eventually destroy superconductivity. After these requirements are satisfied, the highest T c 's are observed for compounds (such as the HgBa 2 Ca n-1 CuO 2n+2+x family) that have flat and square CuO 2 planes and long apical Cu-O bonds. This conclusion is confirmed by the study of materials in which the flatness of the CuO 2 plane can be varied in a systematic way. In more recent work, attention has focused on how the structure can be modified, for example, by chemical substitution, to improve flux pinning properties. Two strategies are being investigated: (1) Increasing the coupling of pancake vortices to form vortex-lines by shortening or ''metallizing'' the blocking layer; and (2) the formation of defects that pin flux

  10. Understanding and application of superconducting materials

    International Nuclear Information System (INIS)

    Moon, Byeong Mu; Lee, Chun Heung

    1997-02-01

    This book deals with superconducting materials, which contains from basic theory to application of superconducting materials. The contents of this book are mystery of superconducting materials, properties of superconducting materials, thermodynamics of superconducting materials, theoretical background of superconducting materials, tunnelling and quantum interference, classification and properties of superconducting materials, high temperature superconducting materials, production and analysis of superconducting materials and application of superconducting materials.

  11. Desgn of a 20-MJ superconducting ohmic-heating coil

    International Nuclear Information System (INIS)

    Singh, S.K.; Murphy, J.H.; Janocko, M.A.; Haller, H.E.; Litz, D.C.; Eckels, P.W.; Rogers, J.D.; Thullen, P.

    1979-01-01

    Conceptual designs of 20-MJ superconducting coils which were developed to demonstrate the feasibility of an ohmic-heating system were discussed. The superconductor materials were NbTi and Nb 3 Sn for the pool boil and forced-flow cooling, respectively. The coils were designed to be cryostable for bipolar operation from +7 to -7 tesla maximum field within one second. The structural design addresses the distribution of structure and structural materials used in the pulsed field environment. The cyclic stresses anticipated and the fatigue limits of the structural materials were examined in view of the operating life of the coil. The coils were designed to generate the flux swings while simultaneously meeting the limitations imposed by cooling, insulation, current density and the stresses in the materials. Both the pool and forced cooled conductors have the same criterion for cryostability, i.e., the conductor must return to the superconducting state from an initial temperature of 20 0 K while the full transport current is flowing through the conductor

  12. Precise Thermometry for Next Generation LHC Superconducting Magnet Prototypes

    CERN Document Server

    Datskov, V; Bottura, L; Perez, J C; Borgnolutti, F; Jenninger, B; Ryan, P

    2013-01-01

    The next generation of LHC superconducting magnets is very challenging and must operate in harsh conditions: high radiation doses in a range between 10 and 50 MGy, high voltage environment of 1 to 5 kV during the quench, dynamic high magnetic field up to 12 T, dynamic temperature range 1.8 K to 300 K in 0.6 sec. For magnet performance and long term reliability it is important to study dynamic thermal effects, such as the heat flux through the magnet structure, or measuring hot spot in conductors during a magnet quench with high sampling rates above 200 Hz. Available on the market cryogenic temperature sensors comparison is given. An analytical model for special electrically insulating thermal anchor (Kapton pad) with high voltage insulation is described. A set of instrumentation is proposed for fast monitoring of thermal processes during normal operation, quenches and failure situations. This paper presents the technology applicable for mounting temperature sensors on high voltage superconducting (SC) cables....

  13. Superconductivity, intergrain, and intragrain critical current densities of materials

    International Nuclear Information System (INIS)

    Thompson, J.R.; Brynestad, J.; Kroeger, D.M.; Kim, Y.C.; Sekula, S.T.; Christen, D.K.; Specht, E.D.

    1989-01-01

    Bulk sintered and powdered samples of the high-temperature superconductive compounds Tl 2 Ca 2 Ba 2 Cu 3 O/sub 1+//sub δ/ (Tl-2:2:2:3) and Tl 2 Ca 2 Ba 2 Cu 2 O/sub 8+//sub δ/ (Tl-2:1:2:2) have been synthesized with phase purity of approximately 90%. The materials were characterized by x-ray-diffraction, metallographic, and electron microprobe analyses. The electronic and superconductive properties were investigated through measurement of the electrical resistivity and the critical current density J/sub c/ using transport methods and by extensive magnetization measurements. Primary results and conclusions are that (1) the intragrain J/sub c/ values were large, much larger than the transport values; (2) both sintered and powdered materials exhibited large flux creep; (3) and the J/sub c/ decreased exponentially with temperature. These features are qualitatively very similar to those found in the corresponding YBa 2 Cu 3 O/sub z/ (with z≅7) series of compounds

  14. Compact high-field superconducting quadrupole magnet with holmium poles

    Energy Technology Data Exchange (ETDEWEB)

    Barlow, D.B.; Kraus, R.H. Jr.; Lobb, C.T.; Menzel, M.T. (Los Alamos National Lab., NM (United States)); Walstrom, P.L. (Grumman Space Systems, Los Alamos, NM (United States))

    1992-03-15

    A compact high-field superconducting quadrupole magnet was designed and built with poles made of the rare-earth metal holmium. The magnet is intended for use in superconducting coupled-cavity linear accelerators where compact high-field quadrupoles are needed, but where the use of permanent magnets is ruled out because of trapped-flux losses. The magnet has a clear bore diameter of 1.8 cm, outside diameter of 11 cm, length of 11 cm, and pole tip length of 6 cm. The effect of using holmium, a material with a higher saturation field than iron, was investigated by replacing poles made of iron with identical poles made of holmium. The magnet was operated at a temperature of 4.2 K and reached a peak quadrupole field gradient of 355 T/m, a 10% increase over the same magnet with iron poles. This increase in performance is consistent with calculations based on B-H curves that were measured for holmium at 4.2 K. (orig.).

  15. Submicron superconducting structures

    International Nuclear Information System (INIS)

    Golovashkin, A.I.; Lykov, A.N.

    1986-01-01

    An overview of works concerning superconducting structures of submicron dimensions and a system of such structures is given. It is noted that usage of the above structures in superconducting microelectronics permits, first, to increase the element packing density, to decrease the signal transmission time, capacity, power dissipated in high-frequency applications. Secondly, negligible coherence length in transition metals, their alloys and high-temperature compounds also restrict the dimensions of superconducting weak couplings when the 'classical' Josephson effect is displayed. The most effective methods for production of submicron superconducting structures are the following: lithography, double scribering. Recently the systems of superconducting submicron elements are extensively studied. It is shown that such systems can be phased by magnetic field

  16. Academic training: Applied superconductivity

    CERN Multimedia

    2007-01-01

    LECTURE SERIES 17, 18, 19 January from 11.00 to 12.00 hrs Council Room, Bldg 503 Applied Superconductivity : Theory, superconducting Materials and applications E. PALMIERI/INFN, Padova, Italy When hearing about persistent currents recirculating for several years in a superconducting loop without any appreciable decay, one realizes that we are dealing with a phenomenon which in nature is the closest known to the perpetual motion. Zero resistivity and perfect diamagnetism in Mercury at 4.2 K, the breakthrough during 75 years of several hundreds of superconducting materials, the revolution of the "liquid Nitrogen superconductivity"; the discovery of still a binary compound becoming superconducting at 40 K and the subsequent re-exploration of the already known superconducting materials: Nature discloses drop by drop its intimate secrets and nobody can exclude that the last final surprise must still come. After an overview of phenomenology and basic theory of superconductivity, the lectures for this a...

  17. Particle exhaust of helium plasmas with actively cooled outboard pump limiter on Tore Supra

    International Nuclear Information System (INIS)

    Uckan, T.; Mioduszewski, P.K.; Loarer, T.; Chatelier, M.; Guilhem, D.; Lutz, T.; Nygren, R.E.; Mahdavi, M.A.

    1995-08-01

    The superconducting tokamak Tore Supra was designed for long-pulse (30-s) high input power operation. Here observations on the particle-handling characteristics of the actively cooled modular outboard pump limiter (OPL) are presented for helium discharges. The important experimental result was that a modest pumping speed (1 m 3 /s) of the OPL turbomolecular pump (TMP) provided background helium exhaust. This result came about due to a well-conditioned vessel wall with helium discharges that caused no wall outgasing. The particle accountability in these helium discharges was excellent, and the well-conditioned wall did not play a significant role in the particle balance. The helium density control, 25% density drop with OPL exhaust efficiency of ∼1%, was possible with TMP although this may not be the case with reactive gases such as deuterium. The observed quadratic increase of the OPL neutral pressure with helium density was consistent with an improvement of the particle control with increasing plasma density

  18. Laser Diode Pumped Solid State Lasers

    Science.gov (United States)

    1987-01-01

    Report N66001-83-C-0071, 17 April 1986, prepared for NOSC. 4.6 W.T. Welford, R. Winston , "The Option of Nonimaging Concentrators ," Academic Press, 1978...by non-imac optics such as reflective or refractive flux concentrators . Simple considerations regarding the optimum pumping configuration, high marks...reduced if the arrays can stand-off from the Nd:YAG laser. As mentioned before, compound parabolic concentrators or refractive optics cat employed to

  19. Imaging the Statics and Dynamics of Superconducting Vortices and Antivortices Induced by Magnetic Microdisks

    Directory of Open Access Journals (Sweden)

    R. B. G. Kramer

    2011-10-01

    Full Text Available If a magnet of microscopic dimensions is brought in close proximity to a superconductor, the quantized nature of their interaction due to the creation of flux quanta in the superconducting system becomes noticeable. Herein, we directly image, via scanning Hall microscopy, the vortex-antivortex pairs in a superconducting film created by micromagnets. The number of antivortices at equilibrium conditions can be changed either by tuning the magnetic moment of the magnets or by annihilation with externally induced vortices. We demonstrate that small ac field excitations shake the antivortices sitting next to the micromagnets whereas no sizable motion is observed for the vortices sitting on top of the magnets, clearly revealing the different mobility of these two vortex species. A metastable state, which is obtained by applying a field after the system has been cooled down below the superconducting transition, shows a complex graded distribution of coexisting vortices and antivortices forming an intertwined critical state.

  20. Flux line patterns in Bi2Sr2Ca1Cu2Ox

    International Nuclear Information System (INIS)

    Weiss, F.; Hardy, V.; Provost, J.; Ruyter, A.; Simon, C.

    1994-01-01

    Results of the defect influence on the flux line lattice in Bi 2 Sr 2 Ca 1 Cu 2 O x single crystals are presented. These crystals, non irradiated or irradiated at GANIL with heavy ions (Pb 56+ , 6 GeV) have been decorated with Ni particles in the superconducting state using the Bitter technique. The defects involved are columnar defects. Resulting decorated flux line patterns have been characterized using scanning electron microscopy and computer image analysis. Disorder of the decorated flux line networks has been found to be strongly dependent on the defect density, which results from the irradiation. In order to characterize this disorder, a method for determining elastic energy terms in the deformation of flux line patterns has been investigated. This method can be applied if Fourier transforms of the decorated flux line patterns exhibit distinct reflections. (orig.)

  1. Gradiometric tunable-gap flux qubits in a circuit QED architecture

    International Nuclear Information System (INIS)

    Schwarz, Manuel Johannes

    2015-01-01

    In circuit quantum electrodynamics or quantum simulation experiments, superconducting quantum bits with long coherence time, high in situ tunability and usually large anharmonicity are required. In contrast to the popular transmon, the gradiometric tunable-gap flux qubit meets all these requirements. We fabricate and characterize such a qubit and demonstrate its first implementation into a transmission line resonator. We show spectroscopy and first time domain results.

  2. A New Facility for Testing Superconducting Solenoid Magnets with Large Fringe Fields at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Orris, D. [Fermilab; Carcagno, R. [Fermilab; Nogiec, J. [Fermilab; Rabehl, R. [Fermilab; Sylvester, C. [Fermilab; Tartaglia, M. [Fermilab

    2013-09-01

    Testing superconducting solenoid with no iron flux return can be problematic for a magnet test facility due to the large magnetic fringe fields generated. These large external fields can interfere with the operation of equipment while precautions must be taken for personnel supporting the test. The magnetic forces between the solenoid under test and the external infrastructure must also be taken under consideration. A new test facility has been designed and built at Fermilab specifically for testing superconducting magnets with large external fringe fields. This paper discusses the test stand design, capabilities, and details of the instrumentation and controls with data from the first solenoid tested in this facility: the Muon Ionization Cooling Experiment (MICE) coupling coil.

  3. Above-cutoff impedance measurements of pumping holes for the Collider Liner

    International Nuclear Information System (INIS)

    Walling, L.; Barts, T.; Ruiz, E.; Turner, W.; Spayd, N.

    1994-04-01

    A holed liner was considered for the Superconducting Super Collider (SSC) Collider Ring because of vacuum problems caused by photon-induced desorption. The liner would serve to shield the cold surface of the beam tube from the synchrotron radiation and the holes (or slots) would allow distributed pumping by gas-absorption material that could be placed between the liner and the beam tube. The impedance of holes and slots in a liner were studied by means of simulations using both MAFIA and HFSS, analytical modelling, wire measurements and electron beam measurements

  4. The state of superconductivity

    International Nuclear Information System (INIS)

    Clark, T.D.

    1981-01-01

    The present status of applications based on the phenomena of superconductivity are reviewed. Superconducting materials, large scale applications, the Josephson effect and its applications, and superconductivity in instrumentation, are considered. The influence that superconductivity has had on modern theories of elementary particles, such as gauge symmetry breaking, is discussed. (U.K.)

  5. Superconductivity - applications

    International Nuclear Information System (INIS)

    The paper deals with the following subjects: 1) Electronics and high-frequency technology, 2) Superconductors for energy technology, 3) Superconducting magnets and their applications, 4) Electric machinery, 5) Superconducting cables. (WBU) [de

  6. Gated-controlled electron pumping in connected quantum rings

    International Nuclear Information System (INIS)

    Lima, R.P.A.; Domínguez-Adame, F.

    2014-01-01

    We study the electronic transport across connected quantum rings attached to leads and subjected to time-harmonic side-gate voltages. Using the Floquet formalism, we calculate the net pumped current generated and controlled by the side-gate voltage. The control of the current is achieved by varying the phase shift between the two side-gate voltages as well as the Fermi energy. In particular, the maximum current is reached when the side-gate voltages are in quadrature. This new design based on connected quantum rings controlled without magnetic fields can be easily integrated in standard electronic devices. - Highlights: • We introduce and study a minimal setup to pump electrons through connected quantum rings. • Quantum pumping is achieved by time-harmonic side-gate voltages instead of the more conventional time-dependent magnetic fluxes. • Our new design could be easily integrated in standard electronic devices

  7. Absence of localization in a disordered one-dimensional ring threaded by an Aharonov-Bohm flux

    International Nuclear Information System (INIS)

    Heinrichs, Jean

    2009-01-01

    Absence of localization is demonstrated analytically to leading order in weak disorder in a one-dimensional Anderson model of a ring threaded by an Aharonov-Bohm (AB) flux. The result follows from adapting an earlier perturbation treatment of disorder in a superconducting ring subjected to an imaginary vector potential proportional to a depinning field for flux lines bound to random columnar defects parallel to the axis of the ring. The absence of localization in the ring threaded by an AB flux for sufficiently weak disorder is compatible with large free-electron-type persistent current obtained in recent studies of the above model.

  8. Characterization of superconducting transmission line resonators

    Energy Technology Data Exchange (ETDEWEB)

    Goetz, Jan; Summer, Philipp; Meier, Sebastian; Haeberlein, Max; Wulschner, Karl Friedrich; Eder, Peter; Fischer, Michael; Schwarz, Manuel; Deppe, Frank; Fedorov, Kirill; Huebl, Hans; Menzel, Edwin [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Krawczyk, Marta; Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Baust, Alexander; Xie, Edwar; Zhong, Ling; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany)

    2015-07-01

    Superconducting transmission line resonators are widely used in circuit quantum electrodynamics experiments as quantum bus or storage devices. For these applications, long coherence times, which can be linked to the internal quality factor of the resonators, are crucial. Here, we show a systematic study of the internal quality factor of niobium thin film resonators. We analyze different cleaning methods and substrate parameters for coplanar waveguide as well as microstrip geometries. In addition, we investigate the impact of a niobium-aluminum interface which is necessary for galvanically coupled flux qubits made from aluminum. This interface can be avoided by fabricating the complete resonator-qubit structure using Al/AlO{sub x}/Al technology during fabrication.

  9. Basic Study of Superconductive Actuator

    OpenAIRE

    涌井, 和也; 荻原, 宏康

    2000-01-01

    There are two kinds of electromagnetic propulsion ships : a superconductive electromagnetic propulsion ship and a superconductive electricity propulsion ship. A superconductive electromagnetic propulsion ship uses the electromagnetic force (Lorenz force) by the interaction between a magnetic field and a electric current. On the other hand, a superconductive electricity propulsion ship uses screws driven by a superconductive motor. A superconductive propulsion ship technique has the merits of ...

  10. 100 years of superconductivity

    CERN Document Server

    Rogalla, Horst

    2011-01-01

    Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in superconductivity, the book includes contributions from many pioneers who are responsible for important steps forward in the field.The text first discusses interesting stories of the discovery and gradual progress of theory and experimentation. Emphasizi

  11. An innovative experiment on superconductivity, based on video analysis and non-expensive data acquisition

    International Nuclear Information System (INIS)

    Bonanno, A; Bozzo, G; Camarca, M; Sapia, P

    2015-01-01

    In this paper we present a new experiment on superconductivity, designed for university undergraduate students, based on the high-speed video analysis of a magnet falling through a ceramic superconducting cylinder (T c  = 110 K). The use of an Atwood’s machine allows us to vary the magnet’s speed and acceleration during its interaction with the superconductor. In this way, we highlight the existence of two interaction regimes: for low crossing energy, the magnet is levitated by the superconductor after a transient oscillatory damping; for higher crossing energy, the magnet passes through the superconducting cylinder. The use of a commercial-grade high speed imaging system, together with video analysis performed using the Tracker software, allows us to attain a good precision in space and time measurements. Four sensing coils, mounted inside and outside the superconducting cylinder, allow us to study the magnetic flux variations in connection with the magnet’s passage through the superconductor, permitting us to shed light on a didactically relevant topic as the behaviour of magnetic field lines in the presence of a superconductor. The critical discussion of experimental data allows undergraduate university students to grasp useful insights on the basic phenomenology of superconductivity as well as on relevant conceptual topics such as the difference between the Meissner effect and the Faraday-like ‘perfect’ induction. (paper)

  12. Superconducting Switch for Fast On-Chip Routing of Quantum Microwave Fields

    Science.gov (United States)

    Pechal, M.; Besse, J.-C.; Mondal, M.; Oppliger, M.; Gasparinetti, S.; Wallraff, A.

    2016-08-01

    A switch capable of routing microwave signals at cryogenic temperatures is a desirable component for state-of-the-art experiments in many fields of applied physics, including but not limited to quantum-information processing, communication, and basic research in engineered quantum systems. Conventional mechanical switches provide low insertion loss but disturb operation of dilution cryostats and the associated experiments by heat dissipation. Switches based on semiconductors or microelectromechanical systems have a lower thermal budget but are not readily integrated with current superconducting circuits. Here we design and test an on-chip switch built by combining tunable transmission-line resonators with microwave beam splitters. The device is superconducting and as such dissipates a negligible amount of heat. It is compatible with current superconducting circuit fabrication techniques, operates with a bandwidth exceeding 100 MHz, is capable of handling photon fluxes on the order of 1 05 μ s-1 , equivalent to powers exceeding -90 dBm , and can be switched within approximately 6-8 ns. We successfully demonstrate operation of the device in the quantum regime by integrating it on a chip with a single-photon source and using it to route nonclassical itinerant microwave fields at the single-photon level.

  13. Superconducting current in a bisoliton superconductivity model

    International Nuclear Information System (INIS)

    Ermakov, V.N.; Kruchinin, S.P.; Ponezha, E.A.

    1991-01-01

    It is shown that the transition into a superconducting state with the current which is described by a bisoliton superconductivity model is accompanied by the deformation of the spectrum of one-particle states of the current carriers. The deformation value is proportional to the conducting current force. The residuaby resistance in such state is absent

  14. Coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compound

    International Nuclear Information System (INIS)

    Lu, T.P.; Wu, C.C.; Chou, W.H.; Lan, M.D.

    2010-01-01

    The magnetic and superconducting properties of the Sm-doped FeAs-based superconducting compound were investigated under wide ranges of temperature and magnetic field. After the systematical magnetic ion substitution, the superconducting transition temperature decreases with increasing magnetic moment. The hysteresis loop of the La 0.87-x Sm x Sr 0.13 FeAsO sample shows a superconducting hysteresis and a paramagnetic background signal. The paramagnetic signal is mainly attributed to the Sm moments. The experiment demonstrates that the coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compounds is possible. Unlike the electron doped FeAs-based superconducting compounds SmFeAsOF, the hole doped superconductivity is degraded by the substitution of La by Sm. The hole-doped and electron-doped sides are not symmetric.

  15. Crystal growth of YFe{sub 2}Ge{sub 2} and the dependence of its superconducting properties on sample preparation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiasheng; Semeniuk, Konstantin; Reiss, Pascal; Brown, Philip; Grosche, Malte [Cavendish Lab., Cambridge (United Kingdom); Feng, Zhuo [London Centre of Nanotechnology, UCL, London (United Kingdom); Lampronti, Giulio [Cambridge Univ., Dept. of Earth Sciences, Cambridge (United Kingdom)

    2016-07-01

    The d-electron system YFe{sub 2}Ge{sub 2} exhibits an unusually high Sommerfeld ratio of specific heat capacity of C/T ∝ 100 mJ/(molK{sup 2}), signaling strong electronic correlations. Evidence of superconductivity has been reported in polycrystals and in flux-grown single crystals with residual resistance ratios (RRR) of the order of 50, but these samples show no thermodynamic signatures of a bulk superconducting transition. We find that by combining (i) a prereaction of YFe{sub 2}, (ii) careful control of nominal composition, and (iii) subsequent annealing procedures, the polycrystalline YFe{sub 2}Ge{sub 2} samples grown using a radio-frequency (RF) induction furnace can reach RRR values ∝ 200 with resistive superconducting transitions temperatures of around 1.85 K. This new generation of sample displays clear heat capacity anomalies as well as nearly 100% diamagnetic screening, confirming the bulk nature of its superconductivity. We present details of the sample preparation and characterization and discuss the correlation between nominal composition and superconductivity.

  16. Superconducting coil configurations, with low flux leakage, for energy storage

    International Nuclear Information System (INIS)

    Vincent-Viry, O.; Mailfert, A.; Trassart, D.

    2001-01-01

    This paper presents two original types of SMES structures for energy storage. These two groups of SMES structures proceeded from an ideal structure: the full toroid, are modeled by the use of purely surface current densities. Their main advantage is to present no flux leakage, they give then satisfactory solution to the problem of energy storage. (orig.)

  17. Particle exhaust studies in Tore Supra with a pump limiter

    International Nuclear Information System (INIS)

    Klepper, C.C.; Haste, G.R.; Horton, L.D.; Mioduszewski, P.K.; Uckan, T.; Bonnel, P.; Bruneau, J.L.; Chatelier, M.; Gil, C.; Grisolia, C.; Loarer, T.; Martin, G.; Pegourie, B.; Rodriguez, L.; Watkins, J.G.

    1990-01-01

    The aim of the Tore Supra pump limiter program is to study particle exhaust with a pump limiter system in long-pulse discharges with continuous pellet fueling and strong auxiliary heating. The pump limiter system consists of six vertical modules, located at the bottom of the machine, and one horizontal module at the outer midplane. The results presented here were obtained with the horizontal module only. This module was equipped with two titanium pumps with a total pumping speed of 100000 L/s. The instrumentation of the limiter included pressure gauges, a residual gas analyzer, Langmuir probes, a spectrometer viewing the neutralizer plate for H α and impurity measurements, and water calorimeters. All diagnostics have been commissioned and are operational. Initial results were obtained in low-density discharges, with no gas puffing during the shot. While only a modest effect on the plasma density was observed, large exhaust fluxes were measured in the pump limiter. The most likely source of this gas was outgassing of the graphite walls. Straightforward particle balance between the plasma efflux and the pump limiter exhaust, as applied in previous pump limiter experiments, did not apply. The core plasma and the edge plasma seemed to be largely decoupled and a multi-layer model is being developed to explain the experimental results. (orig.)

  18. Superconducting pulsed magnets

    CERN Multimedia

    CERN. Geneva

    2006-01-01

    Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mechanisms and calculation of total losses in the magnet. The need for cooling to minimize temperature rise in a magnet. Measuring ac losses in wires and in magnets. Lecture 5. Stab...

  19. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    OpenAIRE

    Dhavale, Asavari S.; Dhakal, Pashupati; Polyanskii, Anatolii A.; Ciovati, Gianluigi

    2012-01-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculat...

  20. New superconducting coil configuration for energy storage

    International Nuclear Information System (INIS)

    Tokorabet, M.; Mailfert, A.; Colteu, A.

    1998-01-01

    Energy storage using superconducting coils involves the problem of electromagnetic field pollution outside the considered system. Different configurations are widely studied: the torus, the alone solenoid and multiple parallel solenoids enclosed in one container. A new configuration which minimizes the external pollution is studied in this paper. The theoretical system is composed of two spherical distributions of the current which are concentric. The analytical study uses solution of Laplace equations. Parametric study covers energy, flux density and geometrical data. The second study concerns the numerical approach of this design using coaxial solenoids. A comparison between this new system and the known systems is presented as a conclusion. (orig.)

  1. High heat flux testing impact on the Tore Supra toroidal pumped limiter achievement

    International Nuclear Information System (INIS)

    Schlosser, J.; Escourbiac, F.; Cordier, J.J.; Mitteau, R.; Durocher, A.; Grosman, A.

    2003-01-01

    The toroidal pumped limiter of Tore Supra is made of 576 elementary high heat flux (HHF) cooled plasma-facing components (PFCs) and designed to sustain 10 MW/m 2 in steady state. One of the main technical difficulties is to ensure a high quality of the bond between the carbon fiber composite armor tile and the water-cooled heat sink due to the high thermal stresses that develop at the bond during operation. Consequently, a HHF facility able to reproduce in service operation of PFCs is required all along the development and manufacturing route. In Europe, the FE200 facility (electron beam, 200 kW, France) operating since 1991, was extensively used for such a development. A first testing campaign in 1995 was devoted to the qualification of this bond: AMC technology from Plansee GmbH was selected. Afterwards, a second campaign on scale-one elements (1996) allowed an optimization of the element design and series production to be launched. During the mass production, a non-destructive control process - cheaper and faster than HHF testing - based on infrared characterization was routinely operated on 100% of the manufactured elements. Strong variability of the bond quality was observed and a repair process allowing the replacement of deficient tiles was developed. In 2000 and 2001, 2 campaigns of HHF testing were launched to correlate the non-destructive measurements and to optimize and validate the repair process. This was done, in two steps, with success. This yielded moreover interesting information for qualifying both tests across each other and also to analyze the fatigue evolution of the bond. The qualification and the achievement of the Tore Supra limiter has greatly been made possible by such HHF tests, which appears as essential before and during PFC manufacturing. (authors)

  2. Exchangers man the pumps

    Science.gov (United States)

    Barkla, Bronwyn J; Hirschi, Kendal D

    2008-01-01

    Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H+-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca2+/H+ exchangers and H+ pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca2+ flux. These results suggest cautious interpretation of mutant Ca2+/H+ exchanger phenotypes that may be due to either perturbed Ca2+ or H+ transport. PMID:19841670

  3. Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Elisabeth Christiane Maria

    2013-05-29

    The field of cavity quantum electrodynamics (QED) studies the interaction between light and matter on a fundamental level. In typical experiments individual natural atoms are interacting with individual photons trapped in three-dimensional cavities. Within the last decade the prospering new field of circuit QED has been developed. Here, the natural atoms are replaced by artificial solid state quantum circuits offering large dipole moments which are coupled to quasi-onedimensional cavities providing a small mode volume and hence a large vacuum field strength. In our experiments Josephson junction based superconducting quantum bits are coupled to superconducting microwave resonators. In circuit QED the number of parameters that can be varied is increased and regimes that are not accessible using natural atoms can be entered and investigated. Apart from design flexibility and tunability of system parameters a particular advantage of circuit QED is the scalability to larger system size enabled by well developed micro- and nanofabrication tools. When scaling up the resonator-qubit systems beyond a few coupled circuits, the rapidly increasing number of interacting subsystems requires an active control and directed transmission of quantum signals. This can, for example, be achieved by implementing switchable coupling between two microwave resonators. To this end, a superconducting flux qubit is used to realize a suitable coupling between two microwave resonators, all working in the Gigahertz regime. The resulting device is called quantum switch. The flux qubit mediates a second order tunable and switchable coupling between the resonators. Depending on the qubit state, this coupling can compensate for the direct geometric coupling of the two resonators. As the qubit may also be in a quantum superposition state, the switch itself can be ''quantum'': it can be a superposition of ''on'' and ''off''. This work

  4. High-current applications of superconductivity

    International Nuclear Information System (INIS)

    Komarek, P.

    1995-01-01

    The following topics were dealt with: superconducting materials, design principles of superconducting magnets, magnets for research and engineering, superconductivity for power engineering, superconductivity in nuclear fusion technology, economical considerations

  5. Vacuum technology issues for the SSC [Superconducting Super Collider

    International Nuclear Information System (INIS)

    Joestlein, H.

    1989-01-01

    The Superconducting Super Collider, to be built in Texas, will provide an energy of 40 TeV from colliding proton beams. This energy is twenty times higher than currently available from the only other cryogenic collider, the Fermilab Tevatron, and will allow experiments that can lead to a better understanding of the fundamental properties of matter. The energy scale and the size of the new machine pose intriguing challenges and opportunities for the its vacuum systems. The discussion will include the effects of synchrotron radiation on cryogenic beam tubes, cold adsorption pumps for hydrogen, methods of leak checking large cryogenic systems, the development of cold beam valves, and radiation damage to components, especially electronics. 9 figs., 1 tab

  6. Half-integer flux quantum effect in cuprate superconductors - a probe of pairing symmetry

    International Nuclear Information System (INIS)

    Tsuei, C.C.; Kirtley, J.R.; Gupta, A.; Sun, J.Z.; Moler, K.A.; Wang, J.H.

    1996-01-01

    Based on macroscopic quantum coherence effects arising from pair tunneling and flux quantization, a series of tricrystal experiments have been designed and carried out to test the order parameter symmetry in high-T c cuprate superconductors. By using a scanning SQUID microscope, we have directly and non-invasively observed the spontaneously generated half-integer flux quantum effect in controlled-orientation tricrystal cuprate superconducting systems. The presence or absence of the half-integer flux quantum effect as a function of the tricrystal geometry allows us to prove that the order parameter symmetry in the YBCO and Tl2201 systems is consistent with that of the d x 2 -y 2 pair state. (orig.)

  7. Laser activated superconducting switch

    International Nuclear Information System (INIS)

    Wolf, A.A.

    1976-01-01

    A superconducting switch or bistable device is described consisting of a superconductor in a cryogen maintaining a temperature just below the transition temperature, having a window of the proper optical frequency band for passing a laser beam which may impinge on the superconductor when desired. The frequency of the laser is equal to or greater than the optical absorption frequency of the superconducting material and is consistent with the ratio of the gap energy of the switch material to Planck's constant, to cause depairing of electrons, and thereby normalize the superconductor. Some embodiments comprise first and second superconducting metals. Other embodiments feature the two superconducting metals separated by a thin film insulator through which the superconducting electrons tunnel during superconductivity

  8. Transport relaxation measurements and glassy state effects in superconducting MgB2

    International Nuclear Information System (INIS)

    Olutas, M.; Yetis, H.; Altinkok, A.; Kilic, A.; Kilic, K.

    2008-01-01

    Time dependent effects in superconducting MgB 2 have been studied systematically for the first time by transport relaxation measurements (V-t curves) as a function of transport current (I), temperature (T) and external magnetic field (H). At very low dissipation levels (below ∼1 μV), it was observed that the sample voltage grows up smoothly in time by exhibiting the details of initial stage of relaxation process. At high dissipation levels, steady state corresponding to constant flow rate is maintained within a very short time and monitoring of details of flux dynamic evolving along sample becomes difficult on long time scales. Another interesting behavior is the appearance of voltage peak when the transport current was reduced to a finite value. After peak, it was observed that the sample voltage relaxes smoothly by leveling off within a very short time. The evolution of V-t curves suggests that formation of resistive flow channels along sample develops easily, which is quite similar to that of obtained for the superconducting ceramic samples whose grain boundaries are improved. Time dependent effects were also observed in magnetovoltage measurements (V-H curves) as the field sweep rate (dH/dt) varies. The observations were interpreted mainly in terms of flux trapping in grains

  9. Superconducting Quantum Interferometers for Nondestructive Evaluation

    Directory of Open Access Journals (Sweden)

    M. I. Faley

    2017-12-01

    Full Text Available We review stationary and mobile systems that are used for the nondestructive evaluation of room temperature objects and are based on superconducting quantum interference devices (SQUIDs. The systems are optimized for samples whose dimensions are between 10 micrometers and several meters. Stray magnetic fields from small samples (10 µm–10 cm are studied using a SQUID microscope equipped with a magnetic flux antenna, which is fed through the walls of liquid nitrogen cryostat and a hole in the SQUID’s pick-up loop and returned sidewards from the SQUID back to the sample. The SQUID microscope does not disturb the magnetization of the sample during image recording due to the decoupling of the magnetic flux antenna from the modulation and feedback coil. For larger samples, we use a hand-held mobile liquid nitrogen minicryostat with a first order planar gradiometric SQUID sensor. Low-Tc DC SQUID systems that are designed for NDE measurements of bio-objects are able to operate with sufficient resolution in a magnetically unshielded environment. High-Tc DC SQUID magnetometers that are operated in a magnetic shield demonstrate a magnetic field resolution of ~4 fT/√Hz at 77 K. This sensitivity is improved to ~2 fT/√Hz at 77 K by using a soft magnetic flux antenna.

  10. Superconducting linac

    International Nuclear Information System (INIS)

    Bollinger, L.M.; Shepard, K.W.; Wangler, T.P.

    1978-01-01

    This project has two goals: to design, build, and test a small superconducting linac to serve as an energy booster for heavy ions from an FN tandem electrostatic accelerator, and to investigate various aspects of superconducting rf technology. The main design features of the booster are described, a status report on various components (resonators, rf control system, linac control system, cryostats, buncher) is given, and plans for the near future are outlined. Investigations of superconducting-linac technology concern studies on materials and fabrication techniques, resonator diagnostic techniques, rf-phase control, beam dynamics computer programs, asymmetry in accelerating field, and surface-treatment techniques. The overall layout of the to-be-proposed ATLAS, the Argonne Tandem-Linac Accelerator System, is shown; the ATLAS would use superconducting technology to produce beams of 5 to 25 MeV/A. 6 figures

  11. Modular pump limiter systems for large tokamaks

    International Nuclear Information System (INIS)

    Uckan, T.; Klepper, C.C.; Mioduszewski, P.K.; McGrath, R.T.

    1987-09-01

    Long-pulse (>10-s) operation of large tokamaks with high-power (>10-MW) heating and extensive external fueling will require correspondingly efficient particle exhaust for density control. A pump limiter can provide the needed exhaust capability by removing a small percentage of the particles, which would otherwise be recycled. Single pump limiter modules have been operated successfully on ISX-B, PDX, TEXTOR, and PLT. An axisymmetric pump limiter is now being installed and will be studied in TEXTOR. A third type of pump limiter is a system that consists of several modules and exhibits performance different from that of a single module. To take advantage of the flexibility of a modular pump limiter system in a high-power, long-pulse device, the power load must be distributed among a number of modules. Because each added module changes the performance of all the others, a set of design criteria must be defined for the overall limiter system. The design parameters for the modules are then determined from the system requirements for particle and power removal. Design criteria and parameters are presented, and the impact on module design of the state of the art in engineering technology is discussed. The relationship between modules are considered from the standpoint of flux coverage and shadowing effects. The results are applied to the Tore Supra tokamak. A preliminary conceptual design for the Tore Supra pump limiter system is discussed, and the design parameters of the limiter modules are presented. 21 refs., 12 figs

  12. Superconductivity and electron microscopy

    International Nuclear Information System (INIS)

    Hawkes, P.W.; Valdre, U.

    1977-01-01

    In this review article, two aspects of the role of superconductivity in electron microscopy are examined: (i) the development of superconducting devices (mainly lenses) and their incorporation in electron microscopes; (ii) the development of electron microscope techniques for studying fundamental and technological problems associated with superconductivity. The first part opens with a brief account of the relevant properties of conventional lenses, after which the various types of superconducting lenses are described and their properties compared. The relative merits and inconveniences of superconducting and conventional lenses are examined, particular attention being paid to the spherical and chromatic aberration coefficients at accelerating voltages above a megavolt. This part closes with a survey of the various microscope designs that have been built or proposed, incorporating superconducting components. In the second part, some methods that have been or might be used in the study of superconductivity in the electron microscope are described. A brief account of the types of application for which they are suitable is given. (author)

  13. Superconductivity in transition metals.

    Science.gov (United States)

    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. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  14. Pumping behavior of sputter ion pumps

    International Nuclear Information System (INIS)

    Chou, T.S.; McCafferty, D.

    The ultrahigh vacuum requirements of ISABELLE is obtained by distributed pumping stations. Each pumping station consists of 1000 l/s titanium sublimation pump for active gases (N 2 , H 2 , O 2 , CO, etc.), and a 20 l/s sputter ion pump for inert gases (methane, noble gases like He, etc.). The combination of the alarming production rate of methane from titanium sublimation pumps (TSP) and the decreasing pumping speed of sputter ion pumps (SIP) in the ultrahigh vacuum region (UHV) leads us to investigate this problem. In this paper, we first describe the essential physics and chemistry of the SIP in a very clean condition, followed by a discussion of our measuring techniques. Finally measured methane, argon and helium pumping speeds are presented for three different ion pumps in the range of 10 -6 to 10 -11 Torr. The virtues of the best pump are also discussed

  15. Flux Creep Investigation in Bi2Sr2CaCu2O8+d High-Temperature Superconductor

    Directory of Open Access Journals (Sweden)

    G. R. Blanca

    2004-12-01

    Full Text Available The flux creep process in a c-axis Bi2Sr2CaCu2O8+d thin film was investigated at different temperatures and applied fields using the Kim-Anderson (KA approach. The peaked behavior shown in the magnetoresistance profile was attributed to the competing mechanisms of flux motion and sample-intrinsic transition near Tc.Within the temperature range where the competition occurs, U increases with temperature and consequently a decrease in the superconducting volume corresponds to a decrease in the flux creep. Moreover, the flux creep potential barrier varies with applied current I at all temperatures consistent with the KA model.

  16. Conceptual design of a high heat flux toroidal pumped limiter for Tore Supra

    International Nuclear Information System (INIS)

    Doceul, L.; Schlosser, J.; Chappuis, Ph.; Chatelier, M.; Cocat, J.P.; Deck, C.; Faisse, F.; Grosman, A.; Mitteau, R.; Tonon, G.

    1994-01-01

    In the frame of the Tore-Supra upgrade, where it is planned to inject up to 25 MW during a time up to 1000 s, a complete toroidal pumped limiter covered of CFC (Carbon Fiber Composite) tiles is being designed. The design is based on the important experience gained from the operation on Tore Supra of actively cooled plasma facing components and pumped limiters. This toroidal limiter covers 7.5 m 2 of the bottom part of the inner vessel and is composed of 576 elementary components. Each element is built from dispersion strengthened copper (DSCu) protected by brazed CFC flat tiles and cooled by pressurised water at 150 deg C. This limiter is designed to sustain 15 MW of convective power. (author) 7 refs.; 5 figs., 3 tabs

  17. Initial operating experience and recent development on the TRIUMF optically pumped polarized H- ion source

    International Nuclear Information System (INIS)

    Schmor, P.W.; Law, W.M.; Levy, C.D.P.; McDonald, M.

    1988-01-01

    A polarized H - ion source using optical pumping techniques has been developed at TRIUMF. This source was used to demonstrate (on an ion source test stand) the feasibility of producing 10- μA of ∼ 60% polarized H - ion beam in a dc mode suitable for injection into the TRIUMF cyclotron. The source has been installed in a 300 kV high voltage terminal connected to the cyclotron via a recently constructed beam transport line. A polarization of 80% is anticipated near the end of 1988 after the installation of a superconducting solenoid to the source. In this paper the authors describe the initial operating experience, recent developments, and the future plans for the TRIUMF optically pumped polarized ion source

  18. Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

    Science.gov (United States)

    Bressac, M.; Guieu, C.; Doxaran, D.; Bourrin, F.; Desboeufs, K.; Leblond, N.; Ridame, C.

    2014-02-01

    Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to refine the "ballast hypothesis". In the framework of the DUNE (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) project, two artificial seedings were performed seven days apart within large mesocosms. A suite of optical and biogeochemical measurements were used to quantify surface POC export following simulated dust events within a low-nutrient, low-chlorophyll ecosystem. The two successive seedings led to a 2.3-6.7-fold higher POC flux than the POC flux observed in controlled mesocosms. A simple linear regression analysis revealed that the lithogenic fluxes explained more than 85% of the variance in POC fluxes. On the scale of a dust-deposition event, we estimated that 42-50% of POC fluxes were strictly associated with lithogenic particles (through aggregation and most probably sorption processes). Lithogenic ballasting also likely impacted the remaining POC fraction which resulted from the fertilization effect. The observations support the "ballast hypothesis" and provide a quantitative estimation of the surface POC export abiotically triggered by dust deposition. In this work, we demonstrate that the strength of such a "lithogenic carbon pump" depends on the biogeochemical conditions of the water column at the time of deposition. Based on these observations, we suggest that this lithogenic carbon pump could represent a major component of the biological pump in oceanic areas subjected to intense atmospheric forcing.

  19. Research and development project for flywheel energy storage system using high-temperature superconducting magnetic bearing

    International Nuclear Information System (INIS)

    Shinagawa, Jiro; Ishikawa, Fumihiko

    1996-01-01

    Recent progress in the research and development of an yttrium-based oxide high-temperature superconductor has enabled the production of a large-diameter bulk with a strong flux-pinning force. A combination of this superconductor and a permanent magnet makes it feasible to fabricate a non-contact, non-controlled superconducting magnetic bearing with a very small rotational loss. Use of the superconducting magnetic bearing for a flywheel energy storage system may pave the way to the development of a new energy storage system that has great energy storage efficiency. >From relevant data measured with a miniature model of the high-temperature superconducting magnetic bearing, a conceptual design of an 8 MWh flywheel energy storage system was developed, using the new bearing which proved to be potentially capable of achieving a high energy storage efficiency of 84%. A 100 Wh-class experimental system was install that attained a high revolution rate of 17.000 rpm. (author)

  20. Linear arrangement of metallic and superconducting defects in a thin superconducting sample

    International Nuclear Information System (INIS)

    Barba-Ortega, J.; Sardella, Edson; Albino Aguiar, J.

    2013-01-01

    Highlights: • We study the influence of superconducting and metallic defects on the vortex configurations in a thin mesoscopic disk. • We found that the vortex–defect interaction leads to interesting vortex configurations. • The first vortex entry is always (never) found sitting on the metallic (superconducting) defect position. -- Abstract: The vortex matter in a superconducting disk with a linear configuration of metallic and superconducting defects is studied. Effects associated to the pinning (anti-pinning) force of the metallic (superconducting) defect on the vortex configuration and on the thermodynamic critical fields are analyzed in the framework of the Ginzburg Landau theory. We calculate the loop of the magnetization, vorticity and free energy curves as a function of the magnetic field for a thin disk. Due to vortex–defect attraction for a metallic defect (repulsion for a superconducting defect), the vortices always (never) are found to be sitting on the defect position