Superconductivity of individual grains and inter-grain boundaries for polycrystalline FeSr2YCu2O6+y

International Nuclear Information System (INIS)

Yamaguchi, K.; Hata, Y.; Mochiku, T.; Yasuoka, H.

2013-01-01

Polycrystalline FeSr 2 YCu 2 O 6+y was synthesized and its transport and magnetic properties were studied. Diamagnetism was observed below 60 K. Zero resistivity was observed below 38 K under zero magnetic field and below 10 K under 160 kOe. A two-step transition was observed in resistivity measurement due to the superconductivity in individual grains and across inter-grain boundaries. The critical current density in individual grains, J c intra , at 2 K under 1 kOe was deduced 3.4 × 10 5 A/cm 2 from the Bean model. In contrast, the critical current density in inter-grain boundaries, J c inter , at 2 K was 1.7 A/cm 2 in voltage–current measurement. The two-step transition seems to result from the large difference between J c intra and J c inter

Vapor bubble growth in highly superheated liquid

International Nuclear Information System (INIS)

Pavlov, P.A.

1981-01-01

Dynamics of the bubble growth in the volume of the uniformally superheated liquid is considered. It is supposed that its growth is hampered by heat transfer. An asymptotic expression for the bubble growth rate at high superheatings when heat hold by liquid is comparable with heat of steam formation, is found by the automodel solution of the heat transfer equation. Writing the radius square in the form of a functional applicable for the calculation of steam formation at the pressure change in superheated liquid is suggested for eveluation calculations [ru

Detection in superheated water chromatography

International Nuclear Information System (INIS)

Chienthavorn, O.

1999-11-01

Superheated water has been used successfully as an eluent in liquid chromatography and has been coupled to various modes of detection, ultraviolet (UV), fluorescence, and nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). A number of compounds were examined on poly(styrene-divinylbenzene) (PS-DVB), polybutadiene (PBD), and octadecylsilyl bonded silica (ODS) column with isothermal and temperature programmes. The PS-DVB column was mostly used throughout the project as it was the most stable. Not only pure water could serve as superheated water mobile phase; inorganic buffered water and ion-pairing reagent with a concentration of 1-3 mM of the buffer and reagent were also exploited. It was shown that the pH could be controlled during the separation without salt precipitation and the separations followed a conventional reversed-phase HPLC method. Results from fluorescence detection showed good separation of a series of vitamins, such as pyridoxine, riboflavin, thiamine, and some analgesics. The relationship of riboflavin using the detection was linear and the detection limit was seven times higher than that of a conventional method. Simultaneous separation and identification using superheated water chromatography-NMR was demonstrated. With using a stop flow method, NMR spectra of model drugs, namely barbiturates, paracetamol, caffeine and phenacetin were obtained and the results agreed with reference spectra, confirming a perfect separation. A demonstration to obtain COSY spectrum of salicylamide was also performed. The method was expanded to the coupling of superheated water LC to NMR-MS. Results from the hyphenated detection method showed that deuteration and degradation happened in the superheated water conditions. The methyl group hydrogens of pyrimidine ring of sulfonamide and thiamine were exchanged with deuterium. Thiamine was decomposed to 4-methyl-5-thiazoleethanol and both were deuterated under the conditions. (author)

Separated type nuclear superheating reactor

International Nuclear Information System (INIS)

Hida, Kazuki.

1993-01-01

In a separated type nuclear superheating reactor, fuel assemblies used in a reactor core comprise fuel rods made of nuclear fuel materials and moderator rods made of solid moderating materials such as hydrogenated zirconium. Since the moderating rods are fixed or made detachable, high energy neutrons generated from the fuel rods are moderated by the moderating rods to promote fission reaction of the fuel rods. Saturated steams supplied from the BWR type reactor by the fission energy are converted to high temperature superheated steams while passing through a steam channel disposed between the fuel rods and the moderating rods and supplied to a turbine. Since water is not used but solid moderating materials sealed in a cladding tube are used as moderation materials, isolation between superheated steams and water as moderators is not necessary. Further, since leakage of heat is reduced to improve a heat efficiency, the structure of the reactor core is simplified and fuel exchange is facilitated. (N.H.)

Two-dimensional modeling of water spray cooling in superheated steam

Directory of Open Access Journals (Sweden)

Ebrahimian Vahid

2008-01-01

Full Text Available Spray cooling of the superheated steam occurs with the interaction of many complex physical processes, such as initial droplet formation, collision, coalescence, secondary break up, evaporation, turbulence generation, and modulation, as well as turbulent mixing, heat, mass and momentum transfer in a highly non-uniform two-phase environment. While it is extremely difficult to systematically study particular effects in this complex interaction in a well defined physical experiment, the interaction is well suited for numerical studies based on advanced detailed models of all the processes involved. This paper presents results of such a numerical experiment. Cooling of the superheated steam can be applied in order to decrease the temperature of superheated steam in power plants. By spraying the cooling water into the superheated steam, the temperature of the superheated steam can be controlled. In this work, water spray cooling was modeled to investigate the influences of the droplet size, injected velocity, the pressure and velocity of the superheated steam on the evaporation of the cooling water. The results show that by increasing the diameter of the droplets, the pressure and velocity of the superheated steam, the amount of evaporation of cooling water increases. .

Growth rate of YBCO-Ag superconducting single grains

Science.gov (United States)

Congreve, J. V. J.; Shi, Y. H.; Dennis, A. R.; Durrell, J. H.; Cardwell, D. A.

2017-12-01

The large scale use of (RE)Ba2Cu3O7 bulk superconductors, where RE=Y, Gd, Sm, is, in part, limited by the relatively poor mechanical properties of these inherently brittle ceramic materials. It is reported that alloying of (RE)Ba2Cu3O7 with silver enables a significant improvement in the mechanical strength of bulk, single grain samples without any detrimental effect on their superconducting properties. However, due to the complexity and number of inter-related variables involved in the top seeded melt growth (TSMG) process, the growth of large single grains is difficult and the addition of silver makes it even more difficult to achieve successful growth reliably. The key processing variables in the TSMG process include the times and temperatures of the stages within the heating profile, which can be derived from the growth rate during the growth process. To date, the growth rate of the YBa2Cu3O7-Ag system has not been reported in detail and it is this lacuna that we have sought to address. In this work we measure the growth rate of the YBCO-Ag system using a method based on continuous cooling and isothermal holding (CCIH). We have determined the growth rate by measuring the side length of the crystallised region for a number of samples for specified isothermal hold temperatures and periods. This has enabled the growth rate to be modelled and from this an optimized heating profile for the successful growth of YBCO-Ag single grains to be derived.

Superheating of Ag nanowires studied by molecular dynamics simulations

International Nuclear Information System (INIS)

Duan Wenshi; Ling Guangkong; Hong Lin; Li Hong; Liang Minghe

2008-01-01

The melting process of Ag nanowires was studied by molecular dynamics (MD) simulations at the atomic level. It is indicated that the Ag nanowires with Ni coating can be superheated depending on their radius and size. Also, in this paper the mechanism of superheating was analyzed and ascribed to the epitaxial Ag/Ni interface suppressing the nucleation and growth of melt. For the analysis, a thermodynamic model was constructed to describe the superheating mechanism of the Ni-coated Ag nanowires by considering the Ag/Ni interface free energy. We showed that the nucleation and growth of the Ag melt phase are both suppressed by the low energy Ag/Ni interfaces in Ni-coated Ag wires and the suppression of melt growth is crucial and plays a major role in the process of melting. The thermodynamic analysis gave a quantitative relation of superheating with the Ag wire radius and the contact angle of melting. The superheating decreased with Ag wire radius and also depended on the Ag/Ni interfacial condition. The results of the thermodynamic model were consistent with those of the MD simulations

Superconducting wires and methods of making thereof

Energy Technology Data Exchange (ETDEWEB)

Xu, Xingchen; Sumption, Michael D.; Peng, Xuan

2018-03-13

Disclosed herein are superconducting wires. The superconducting wires can comprise a metallic matrix and at least one continuous subelement embedded in the matrix. Each subelement can comprise a non-superconducting core, a superconducting layer coaxially disposed around the non-superconducting core, and a barrier layer coaxially disposed around the superconducting layer. The superconducting layer can comprise a plurality of Nb.sub.3Sn grains stabilized by metal oxide particulates disposed therein. The Nb.sub.3Sn grains can have an average grain size of from 5 nm to 90 nm (for example, from 15 nm to 30 nm). The superconducting wire can have a high-field critical current density (J.sub.c) of at least 5,000 A/mm.sup.2 at a temperature of 4.2 K in a magnetic field of 12 T. Also described are superconducting wire precursors that can be heat treated to prepare superconducting wires, as well as methods of making superconducting wires.

Explosive Boiling of Superheated Cryogenic Liquids

CERN Document Server

Baidakov, V G

2007-01-01

The monograph is devoted to the description of the kinetics of spontaneous boiling of superheated liquefied gases and their solutions. Experimental results are given on the temperature of accessible superheating, the limits of tensile strength of liquids due to processes of cavitation and the rates of nucleation of classical and quantum liquids. The kinetics of evolution of the gas phase is studied in detail for solutions of cryogenic liquids and gas-saturated fluids. The properties of the critical clusters (bubbles of critical sizes) of the newly evolving gas phase are analyzed for initial st

Surface boiling of superheated liquid

Energy Technology Data Exchange (ETDEWEB)

Reinke, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-01-01

A basic vaporization mechanism that possibly affects the qualitative and quantitative prediction of the consequences of accidental releases of hazardous superheated liquids was experimentally and analytically investigated. The studies are of relevance for the instantaneous failure of a containment vessel filled with liquefied gas. Even though catastrophical vessel failure is a rare event, it is considered to be a major technological hazard. Modeling the initial phase of depressurisation and vaporization of the contents is an essential step for the subsequent analysis of the spread and dispersion of the materials liberated. There is only limited understanding of this inertial expansion stage of the superheated liquid, before gravity and atmospheric turbulence begin to dominate the expansion. This work aims at a better understanding of the vaporization process and to supply more precise source-term data. It is also intended to provide knowledge for the prediction of the behavior of large-scale releases by the investigation of boiling on a small scale. Release experiments with butane, propane, R-134a and water were conducted. The vaporization of liquids that became superheated by sudden depressurisation was studied in nucleation-site-free glass receptacles. Several novel techniques for preventing undesired nucleation and for opening the test-section were developed. Releases from pipes and from a cylindrical geometry allowed both linear one-dimensional, and radial-front two-dimensional propagation to be investigated. Releases were made to atmospheric pressure over a range of superheats. It was found that, above a certain superheat temperature, the free surface of the metastable liquid rapidly broke up and ejected a high-velocity vapor/liquid stream. The zone of intense vaporization and liquid fragmentation proceeded as a front that advanced into the test fluids. No nucleation of bubbles in the bulk of the superheated liquid was observed. (author) figs., tabs., refs.

Surface boiling of superheated liquid

International Nuclear Information System (INIS)

Reinke, P.

1997-01-01

A basic vaporization mechanism that possibly affects the qualitative and quantitative prediction of the consequences of accidental releases of hazardous superheated liquids was experimentally and analytically investigated. The studies are of relevance for the instantaneous failure of a containment vessel filled with liquefied gas. Even though catastrophical vessel failure is a rare event, it is considered to be a major technological hazard. Modeling the initial phase of depressurisation and vaporization of the contents is an essential step for the subsequent analysis of the spread and dispersion of the materials liberated. There is only limited understanding of this inertial expansion stage of the superheated liquid, before gravity and atmospheric turbulence begin to dominate the expansion. This work aims at a better understanding of the vaporization process and to supply more precise source-term data. It is also intended to provide knowledge for the prediction of the behavior of large-scale releases by the investigation of boiling on a small scale. Release experiments with butane, propane, R-134a and water were conducted. The vaporization of liquids that became superheated by sudden depressurisation was studied in nucleation-site-free glass receptacles. Several novel techniques for preventing undesired nucleation and for opening the test-section were developed. Releases from pipes and from a cylindrical geometry allowed both linear one-dimensional, and radial-front two-dimensional propagation to be investigated. Releases were made to atmospheric pressure over a range of superheats. It was found that, above a certain superheat temperature, the free surface of the metastable liquid rapidly broke up and ejected a high-velocity vapor/liquid stream. The zone of intense vaporization and liquid fragmentation proceeded as a front that advanced into the test fluids. No nucleation of bubbles in the bulk of the superheated liquid was observed. (author) figs., tabs., refs

Superheated emulsions in neutron spectrometry by varying ambient pressure

International Nuclear Information System (INIS)

Das, Mala; Sawamura, Teruko

2005-01-01

The principle of present work lies on the dependence of the threshold neutron energy on the dimensionless quantity ''degree of metastability (ss)'' of superheated liquids. The response of the superheated emulsions consists of the drops of superheated liquid (C 2 Cl 2 F 4 , b.p. 3.77 deg. C) has been measured at different 'ss' by varying ambient pressure at different temperatures, in the presence of neutrons generated in Pb by a (γ,n) reaction from 45 MeV electron LINAC of Hokkaido University. To unfold the neutron energy spectrum, a relationship has been developed between the 'ss' of superheated liquids and the threshold neutron energy. The spectrum at the detector position has been calculated by the MCNP code and a comparison has been made with the experimental spectrum. The utilisation of 'ss' is more flexible as this relation can be applied to both positive and negative ambient pressures as well as at different ambient temperatures

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

Construction for wet steam drying and further superheating of the dry steam

International Nuclear Information System (INIS)

1978-01-01

The steam drying operates by a coarse- and a fine trap. The subsequent superheating occurs in a superheating tube nest. Everything is fixed in a cylindric container; the coarse trap is arranged on the bottom zone, and the superheating tubes are arranged along the container axis almost up to the container top around a pipe. (DG) [de

Grain boundaries in high temperature superconductors

NARCIS (Netherlands)

Hilgenkamp, Johannes W.M.; Mannhart, J.

2002-01-01

Since the first days of high-Tc superconductivity, the materials science and the physics of grain boundaries in superconducting compounds have developed into fascinating fields of research. Unique electronic properties, different from those of the grain boundaries in conventional metallic

Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for SCWR in superheated steam

International Nuclear Information System (INIS)

Abe, Hiroshi; Hong, Seung Mo; Watanabe, Yutaka

2014-01-01

Highlights: • Effect of cold work on oxidation kinetics was clearly observed for 15Cr–20Ni SS. • The tube-shaped 15Cr–20Ni SS showed very good oxidation resistance. • The machined layer by cold drawing has a significant role to mitigate oxidation. - Abstract: Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for supercritical-water-cooled reactor (SCWR), including three types of 15Cr–20Ni stainless steels (1520 SSs), in the temperature range of 700–780 °C superheated steam have been investigated. Effect of temperature, dissolved oxygen (DO), degree of cold work (CW), and machined layer by cold drawing process on the oxidation kinetics assuming power-law kinetics are discussed. Characteristics of oxide layers and its relation to oxidation behaviors are also discussed. The effect of DO on the weight gain behavior in superheated steam at 700 °C was minor for all specimens at least up to 200 ppb DO. The tube-shaped specimens of 1520 SSs showed very good oxidation resistance at 700–780 °C. There was no clear difference in the oxidation kinetics among the three investigated types of 1520 SSs. The machined layer formed at the tube surface has a significant role to mitigate oxidation in superheated steam. A fine-grained microstructure near the surface due to recrystallization by cold drawing process is effective to form the protective Cr 2 O 3 layer. It has been suggested that since Cr diffusion in the outside surface of tubes is accelerated as a result of an increased dislocation density and/or grain refinement by cold drawing, tube specimens show very slow oxidation kinetics. Breakdown of the protective Cr 2 O 3 layer and nodule oxide formation were partly observed on the tube-shaped specimens of 15Cr–20Ni SSs. The reliability of Cr 2 O 3 layer has to be carefully examined to predict the oxidation kinetics after long-term exposure

Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for SCWR in superheated steam

Energy Technology Data Exchange (ETDEWEB)

Abe, Hiroshi, E-mail: hiroshi.abe@qse.tohoku.ac.jp; Hong, Seung Mo; Watanabe, Yutaka

2014-12-15

Highlights: • Effect of cold work on oxidation kinetics was clearly observed for 15Cr–20Ni SS. • The tube-shaped 15Cr–20Ni SS showed very good oxidation resistance. • The machined layer by cold drawing has a significant role to mitigate oxidation. - Abstract: Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for supercritical-water-cooled reactor (SCWR), including three types of 15Cr–20Ni stainless steels (1520 SSs), in the temperature range of 700–780 °C superheated steam have been investigated. Effect of temperature, dissolved oxygen (DO), degree of cold work (CW), and machined layer by cold drawing process on the oxidation kinetics assuming power-law kinetics are discussed. Characteristics of oxide layers and its relation to oxidation behaviors are also discussed. The effect of DO on the weight gain behavior in superheated steam at 700 °C was minor for all specimens at least up to 200 ppb DO. The tube-shaped specimens of 1520 SSs showed very good oxidation resistance at 700–780 °C. There was no clear difference in the oxidation kinetics among the three investigated types of 1520 SSs. The machined layer formed at the tube surface has a significant role to mitigate oxidation in superheated steam. A fine-grained microstructure near the surface due to recrystallization by cold drawing process is effective to form the protective Cr{sub 2}O{sub 3} layer. It has been suggested that since Cr diffusion in the outside surface of tubes is accelerated as a result of an increased dislocation density and/or grain refinement by cold drawing, tube specimens show very slow oxidation kinetics. Breakdown of the protective Cr{sub 2}O{sub 3} layer and nodule oxide formation were partly observed on the tube-shaped specimens of 15Cr–20Ni SSs. The reliability of Cr{sub 2}O{sub 3} layer has to be carefully examined to predict the oxidation kinetics after long-term exposure.

Treating bituminous minerals. [use of superheated steam

Energy Technology Data Exchange (ETDEWEB)

MacIvor, G

1880-12-21

In this new procedure, the superheated steam is the agent by which the heat is directly applied to the rock; the superheated steam is made to pass between the rocks and into the vessel or retort in which the rock is contained and where the extraction of the bitumen or the distillation of the mineral oils is carried out. The temperature of the heating apparatus in which the steam is superheated, is easily regulated at will in accord with the desired result. When one wishes to extract only bitumen, the temperature of the steam is raised to a point sufficiently high to loosen and separate the bitumen without permitting any condensation of water inside the retort. When it is desired to produce a mineral oil, the temperature is increased in such a way that all the volatile products are distilled from the rock and come into the condenser. By means of this process, any temperature up to a full red heat, can be maintained in the retort, making possible many variations in the kind of products obtainable from the rock.

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.

Thermoeconomic optimization of subcooled and superheated vapor compression refrigeration cycle

International Nuclear Information System (INIS)

Selbas, Resat; Kizilkan, Onder; Sencan, Arzu

2006-01-01

An exergy-based thermoeconomic optimization application is applied to a subcooled and superheated vapor compression refrigeration system. The advantage of using the exergy method of thermoeconomic optimization is that various elements of the system-i.e., condenser, evaporator, subcooling and superheating heat exchangers-can be optimized on their own. The application consists of determining the optimum heat exchanger areas with the corresponding optimum subcooling and superheating temperatures. A cost function is specified for the optimum conditions. All calculations are made for three refrigerants: R22, R134a, and R407c. Thermodynamic properties of refrigerants are formulated using the Artificial Neural Network methodology

Process for superheating the steam generated by a light water nuclear reactor

International Nuclear Information System (INIS)

Vakil, H.B.; Brown, D.H.

1976-01-01

A process is submitted for superheating the pressurised steam generated in a light water nuclear reactor in which the steam is brought to 340 0 C at least. This superheated steam is used to operate a turbo-generator unit. The characteristic of the process is that an exothermal chemical reaction is used to generate the heat utilised during the superheating stage. The chemical reaction is a mechanisation, oxidation-reduction or hydrogenation reaction [fr

Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

OpenAIRE

Xin Zhao; G. Ciovati; T. R. Bieler

2010-01-01

The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical micro...

Preparation and characterisation of superheated drop detectors

International Nuclear Information System (INIS)

Krishnamoorthy, P.

1989-01-01

Basic mechanism of bubble nucleation in superheated drops with respect to minimum energy of radiation and temperature is discussed. Experimental details and techniques for the preparation of Superheated Drop Detectors (SDDs) is explained. For the sample preparation, homogeneous composition of polymer (Morarfloc) and glycerine was used as the host medium and three different refrigerants Mafron-21, Mafron-12 and Mafron-11/12 (50:50) were chosen as the sensitive liquids. A pressure reactor developed at Health and Safety Laboratory is used for dispersing the sensitive liquid drops in the homogeneous composition under pressure. Some of the imporatant detector characteristics were studied. (author). 26 refs., 9 figs., 1 tab

Effect of microwave-enhanced superconductivity in YBa2Cu3O7 bi-crystalline grain boundary weak-links

International Nuclear Information System (INIS)

Fu, C.M.; Chen, C.M.; Lin, H.C.

1994-01-01

We have studied systematically the effect of microwave irradiation on the temperature dependent resistivity R(T) and the current-voltage (I-V) characteristics of YBa 2 Cu 3 O 7-x (YBCO) bicrystalline grain boundary weak-links (GBWLs), with grain boundary of three different tilt angles. The superconducting transition temperature, T c , has significant enhancement upon microwave irradiation. The microwave enhanced T c is increased as a function of incidence microwave power, but limited to an optimum power level. The GBWLs of 45 degrees tilt boundary has shown to be most sensitive to the microwave irradiation power, and the GBWLs of 36.8 degrees tilt boundary has displayed a moderate response. In contrast, no enhancement of T c was observed in the GBWLs of 24 degrees tilt boundary, as well as in the uniform films. Under the microwave irradiation, the R(T) dependence is hysteretic as the transition taken from superconducting state to normal state and vice versa. Mechanisms associated with the redistribution of nonequilibrium quasiparticles under microwave irradiation are discussed

Neutron-gamma discrimination by pulse analysis with superheated drop detector

International Nuclear Information System (INIS)

Das, Mala; Seth, S.; Saha, S.; Bhattacharya, S.; Bhattacharjee, P.

2010-01-01

Superheated drop detector (SDD) consisting of drops of superheated liquid of halocarbon is irradiated to neutrons and gamma-rays from 252 Cf fission neutron source and 137 Cs gamma source, respectively, separately. Analysis of pulse height of signals at the neutron and gamma-ray sensitive temperature provides significant information on the identification of neutron and gamma-ray induced events.

Melting of superheated molecular crystals

Science.gov (United States)

Cubeta, Ulyana; Bhattacharya, Deepanjan; Sadtchenko, Vlad

2017-07-01

Melting dynamics of micrometer scale, polycrystalline samples of isobutane, dimethyl ether, methyl benzene, and 2-propanol were investigated by fast scanning calorimetry. When films are superheated with rates in excess of 105 K s-1, the melting process follows zero-order, Arrhenius-like kinetics until approximately half of the sample has transformed. Such kinetics strongly imply that melting progresses into the bulk via a rapidly moving solid-liquid interface that is likely to originate at the sample's surface. Remarkably, the apparent activation energies for the phase transformation are large; all exceed the enthalpy of vaporization of each compound and some exceed it by an order of magnitude. In fact, we find that the crystalline melting kinetics are comparable to the kinetics of dielectric α-relaxation in deeply supercooled liquids. Based on these observations, we conclude that the rate of non-isothermal melting for superheated, low-molecular-weight crystals is limited by constituent diffusion into an abnormally dense, glass-like, non-crystalline phase.

Response of Superheated Droplet Detector (SDD) and Bubble Detector (BD) to interrupted irradiations

Energy Technology Data Exchange (ETDEWEB)

Mondal, Prasanna Kumar, E-mail: prasanna_ind_82@yahoo.com; Sarkar, Rupa, E-mail: sarkar_rupa2003@yahoo.com; Chatterjee, Barun Kumar, E-mail: barun_k_chatterjee@yahoo.com

2017-06-11

Superheated droplet detectors (SDD) and bubble detectors (BD) are suspensions of micron-sized superheated liquid droplets in inert medium. The metastable droplets can vaporise upon interaction with ionising radiation generating visible bubbles. In this work, we investigated the response of SDD and BD to interrupted neutron irradiations. We observed that the droplet vaporisation rates for SDD and BD are different in nature. The unusual increase in droplet vaporisation rate observed when the SDD is exposed to neutrons after few minutes of radiation-off period is absent for BD. - Highlights: • Superheated droplet detectors (SDD) and bubble detectors (BD) are suspensions of superheated liquid droplets in inert medium. • The bubble nucleation in superheated droplets can be induced by ionising radiation. • The droplet vaporisation rate for SDD is non-monotonic when it is irradiated periodically to neutrons. • For BD the droplet vaporisation rate decrease monotonically when it is irradiated periodically to neutrons.

PREFACE: PASREG 2003: International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials

Science.gov (United States)

Murakami, Masato; Cardwell, David; Salama, Kamel; Krabbes, Gernot; Habisreuther, Tobias; Gawalek, Wolfgang

2005-02-01

Superconducting melt-textured bulk (RE)BCO large grain materials are one of the most promising materials for power applications of high temperature superconductivity at the liquid nitrogen temperature range. Industrial applications are expected in high-speed low-loss magnetic bearings for flywheel energy storage devices, high-dynamic high-torque electric reluctance motors, and MAGLEV transportation systems. The material has high magnetic field trapping capability and therefore a new class of high-field superconducting permanent magnets will soon appear. However, there is still the need to improve the magnetic and mechanical material properties, as well as to increase the single domain size. This special issue contains papers concerning these topics presented at the International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials. The workshop was held on the 30 June-2 July 2003 in Jena, Germany, and was organized by the Institut fuer Physikalische Hochtechnologie, Jena. It was the fourth in the series of PASREG workshops after Cambridge, UK (1997), Morioka, Japan (1999), and Seattle, USA (2001). Sixty two contributions were presented at the workshop, 38 oral presentations and 24 poster presentations. This special issue contains 42 papers. The editors are grateful for the support of many colleagues who reviewed the manuscripts to guarantee their high technical quality. The editors also wish to thank Doris Litzkendorf and Tobias Habisreuther from Institut fuer Physikalische Hochtechnologie, Jena, for their assistance with the organization and handling of the manuscripts. Many thanks to the workshop co-chairman Gernot Krabbes from Leibniz-Institut fuer Festkoerper und Werkstoffforschung, Dresden, for hosting the workshop participants in Dresden. Finally, all attendees wish to acknowledge the efforts of Wolfgang Gawalek, Tobias Habisreuther, Doris Litzkendorf and the Team of Department Magnetics from the Institut fuer

Acoustic response of superheated droplet detectors to neutrons

International Nuclear Information System (INIS)

Gao Size; Zhang Guiying; Ni Bangfa; Zhao Changjun; Zhang Huanqiao; Guan Yongjing; Chen Zhe; Xiao Caijin; Liu Chao; Liu Cunxiong

2012-01-01

The search for dark matter (DM) is a hot field nowadays, a number of innovative techniques have emerged. The superheated droplet technique is relatively mature; however, it is recently revitalized in a number of frontier fields including the search for DM. In this work, the acoustic response of Superheated Droplet Detectors (SDDs) to neutrons was studied by using a 252 Cf neutron source, SDDs developed by the China Institute of Atomic Energy, a sound sensor, a sound card and a PC. Sound signals were filtered. The characteristics of FFT spectra, power spectra and time constants were used to determine the authenticity of the bubbles analyzed.

Radiation dosimetry and spectrometry with superheated emulsions

International Nuclear Information System (INIS)

D'Errico, Francesco

2001-01-01

Detectors based on emulsions of overexpanded halocarbon droplets in tissue equivalent aqueous gels or soft polymers, known as 'superheated drop detectors' or 'bubble (damage) detectors', have been used in radiation detection, dosimetry and spectrometry for over two decades. Recent technological advances have led to the introduction of several instruments for individual and area monitoring: passive integrating meters based on the optical or volumetric registration of the bubbles, and active counters detecting bubble nucleations acoustically. These advances in the instrumentation have been matched by the progress made in the production of stable and well-specified emulsions of superheated droplets. A variety of halocarbons are employed in the formulation of the detectors, and this permits a wide range of applications. In particular, halocarbons with a moderate degree of superheat, i.e. a relatively small difference between their operating temperature and boiling point, can be used in neutron dosimetry and spectrometry since they are only nucleated by energetic heavy ions such as those produced by fast neutrons. More recently, halocarbons with an elevated degree of superheat have been utilised to produce emulsions that nucleate with much smaller energy deposition and detect low linear energy transfer radiations, such as photons and electrons. This paper reviews the detector physics of superheated emulsions and their applications in radiation measurements, particularly in neutron dosimetry and spectrometry

Surface morphology of laser superheated Pb(111)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Z. H.; Lin, Bo; Zeng, X. L.; Elsayed-Ali, H. E.

1998-05-01

The step density on the vicinal Pb(111) surface after laser superheating and melting is investigated using reflection high-energy electron diffraction. The (00) beam profiles parallel and perpendicular to the incident beam are analyzed. For laser heating with ˜100 ps laser pulses, surface superheating does not significantly change the density of the steps and step edge roughness. A sudden increase in the average terrace width is observed after laser surface melting. The average terrace width and the string length at the step edge become as large as those at room temperature. The average terrace width at 573 K changes from 38±15 to 64±19 Å after laser surface melting, while the average string length at the step edge changes from 50±12 to 250±38 Å.

Superheated drop, open-quotes Bubbleclose quotes, dosimeters

International Nuclear Information System (INIS)

Harper, M.J.; Lindler, K.W.; Nelson, M.E.; Johnson, T.L.; Jones, C.R.; Rabovsky, J.L.; Rao, N.; Kerschner, H.F.; Reil, G.K.; Schwartz, R.B.

1991-01-01

Superheated Drop Dosimeters (SDD) offer a sensitive, immediate measure of the neutron dose equivalent, but their dynamic range is limited and their response varies with temperature, pressure, and vibration. They contain thousands of superheated liquid drops in a stabilizing matrix. High linear energy transfer (LET) radiation triggers vaporization of the drops into visible bubbles. If the matrix is a liquid, the bubbles slowly rise, and the number present indicates the dose rate. Dose may be measured by displacement of the matrix, or by counting the sounds of vaporization. If the matrix is a gel, the bubbles are fixed, and their number is proportional to the dose equivalent. Our research has focused on modeling and elimination of the environmental response, extension of the dynamic range, and tests and evaluations of prototype devices

Rapid Generation of Superheated Steam Using a Water-containing Porous Material

Science.gov (United States)

Mori, Shoji; Okuyama, Kunito

Heat treatment by superheated steam has been utilized in several industrial fields including sterilization, desiccation, and cooking. In particular, cooking by superheated steam is receiving increased attention because it has advantages of reducing the salt and fat contents in foods as well as suppressing the oxidation of vitamin C and fat. In this application, quick startup and cut-off responses are required. Most electrically energized steam generators require a relatively long time to generate superheated steam due to the large heat capacities of the water in container and of the heater. Zhao and Liao (2002) introduced a novel process for rapid vaporization of subcooled liquid, in which a low-thermal-conductivity porous wick containing water is heated by a downward-facing grooved heating block in contact with the upper surface of the wick structure. They showed that saturated steam is generated within approximately 30 seconds from room-temperature water at a heat flux 41.2 kW⁄m2. In order to quickly generate superheated steam of approximately 300°C, which is required for cooking, the heat capacity of the heater should be as small as possible and the imposed heat flux should be so high enough that the porous wick is able to dry out in the vicinity of the contact with the heater and that the resulting heater temperature becomes much higher than the saturation temperature. The present paper proposes a simple structured generator to quickly produce superheated steam. Only a fine wire heater is contacted spirally on the inside wall in a hollow porous material. The start-up, cut-off responses and the rate of energy conversion for input power are investigated experimentally. Superheated steam of 300°C is produced in approximately 19 seconds from room-temperature water for an input power of 300 W. The maximum rate of energy conversion in the steady state is approximately 0.9.

Field limit and nano-scale surface topography of superconducting radio-frequency cavity made of extreme type II superconductor

Science.gov (United States)

Kubo, Takayuki

2015-06-01

The field limit of a superconducting radio-frequency cavity made of a type II superconductor with a large Ginzburg-Landau parameter is studied, taking the effects of nano-scale surface topography into account. If the surface is ideally flat, the field limit is imposed by the superheating field. On the surface of cavity, however, nano-defects almost continuously distribute and suppress the superheating field everywhere. The field limit is imposed by an effective superheating field given by the product of the superheating field for an ideal flat surface and a suppression factor that contains the effects of nano-defects. A nano-defect is modeled by a triangular groove with a depth smaller than the penetration depth. An analytical formula for the suppression factor of bulk and multilayer superconductors is derived in the framework of the London theory. As an immediate application, the suppression factor of the dirty Nb processed by electropolishing is evaluated by using results of surface topographic study. The estimated field limit is consistent with the present record field of nitrogen-doped Nb cavities. Suppression factors of surfaces of other bulk and multilayer superconductors, and those after various surface processing technologies, can also be evaluated by using the formula.

Fragility of superheated melts and glass-forming ability in Pr-based alloys

International Nuclear Information System (INIS)

Meng, Q.G.; Zhou, J.K.; Zheng, H.X.; Li, J.G.

2006-01-01

The kinetic viscosity (η) of superheated melts, thermal properties (T x , T m , T L ) and X-ray diffraction analysis on the Pr-based bulk metallic glasses (BMG) are reported and discussed. A new refined concept, the superheated fragility defined as M' = E S δ x /k B , has been developed based on common solidification theory and the Arrhenius equation. The interrelationship between this kind of fragility and the glass-forming ability (GFA) is elaborated on and evaluated in Pr-based BMG and Al-based amorphous ribbon alloys. Using viscosity data of superheated melts, it is shown, theoretically and experimentally, that the fragility parameter M' may be used as a GFA indicator for metallic alloys

Cascade control of superheated steam temperature with neuro-PID controller.

Science.gov (United States)

Zhang, Jianhua; Zhang, Fenfang; Ren, Mifeng; Hou, Guolian; Fang, Fang

2012-11-01

In this paper, an improved cascade control methodology for superheated processes is developed, in which the primary PID controller is implemented by neural networks trained by minimizing error entropy criterion. The entropy of the tracking error can be estimated recursively by utilizing receding horizon window technique. The measurable disturbances in superheated processes are input to the neuro-PID controller besides the sequences of tracking error in outer loop control system, hence, feedback control is combined with feedforward control in the proposed neuro-PID controller. The convergent condition of the neural networks is analyzed. The implementation procedures of the proposed cascade control approach are summarized. Compared with the neuro-PID controller using minimizing squared error criterion, the proposed neuro-PID controller using minimizing error entropy criterion may decrease fluctuations of the superheated steam temperature. A simulation example shows the advantages of the proposed method. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Temperature dependence of the experimental penetration depth of superconducting thin films

International Nuclear Information System (INIS)

Fink, H.J.; Gruenfeld, V.; Pastawski, H.

1982-01-01

Experimental magnetic field penetration depths delta(t,d,H) of the stable and superheated Meissner state were calculated as a function of temperature for various applied magnetic fields and various film thicknesses for two cases: (1) lambda(t)/d<< kappa→infinity and (2) kappa< or approx. =2lambda(t)/d (lambda is the Ginzburg-Landau penetration depth, d is the film thickness, kappa is the GL parameter). The results of the first case should be a useful tool for obtaining lambda(0) of amorphous superconducting thin films

Effect of microwave-enhanced superconductivity in YBa{sub 2}Cu{sub 3}O{sub 7} bi-crystalline grain boundary weak-links

Energy Technology Data Exchange (ETDEWEB)

Fu, C.M.; Chen, C.M.; Lin, H.C. [National Chiao-Tung Univ., Taiwan (China)] [and others

1994-12-31

We have studied systematically the effect of microwave irradiation on the temperature dependent resistivity R(T) and the current-voltage (I-V) characteristics of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bicrystalline grain boundary weak-links (GBWLs), with grain boundary of three different tilt angles. The superconducting transition temperature, T{sub c}, has significant enhancement upon microwave irradiation. The microwave enhanced T{sub c} is increased as a function of incidence microwave power, but limited to an optimum power level. The GBWLs of 45{degrees} tilt boundary has shown to be most sensitive to the microwave irradiation power, and the GBWLs of 36.8{degrees} tilt boundary has displayed a moderate response. In contrast, no enhancement of T{sub c} was observed in the GBWLs of 24{degrees} tilt boundary, as well as in the uniform films. Under the microwave irradiation, the R(T) dependence is hysteretic as the transition taken from superconducting state to normal state and vice versa. Mechanisms associated with the redistribution of nonequilibrium quasiparticles under microwave irradiation are discussed.

Advances in development of Nb3Sn superconducting radio-frequency cavities

Science.gov (United States)

Posen, Sam; Liepe, Matthias

2014-11-01

A 1.3 GHz Nb3Sn superconducting radio-frequency cavity prepared with a modified annealing step reached Bp k>50 mT , well above Bc 1=25 ±7 mT , without the strong Q -slope observed in previous Nb3Sn cavities. At 4.2 K, it has a Q0 of approximately 1 ×1 010 at >10 MV /m , far outperforming Nb at useable gradients. At 2 K, quench occurred at ˜55 mT , apparently due to a defect, so additional treatment may increase the maximum gradient. Material parameters of the coating were extracted from Q vs T data, including a Tc of 18.0 ±0.1 K , close to the maximum literature value. High power pulses were used to reach fields far higher than in CW measurements, and near Tc, quench fields close to the superheating field were observed. Based on a review of previous experience with Nb3Sn cavities, a speculative mechanism involving weak link grain boundaries is presented to explain how the modified annealing step could be the cause of the absence of strong Q -slope. Finally, an analysis of the progress to date provides hints that the path forward for Nb3Sn cavities should focus on minimizing defects.

Biodiesel production via injection of superheated methanol technology at atmospheric pressure

International Nuclear Information System (INIS)

Ang, Gaik Tin; Tan, Kok Tat; Lee, Keat Teong; Mohamed, Abdul Rahman

2014-01-01

Highlights: • Non-catalytic superheated methanol for biodiesel production is developed. • Crude Jatropha curcas oil with high FFA can be directly used as oil feedstock. • High content of biodiesel can be produced. • Separation of FAME and glycerol from the sample product is easy. - Abstract: In this high demand of renewable energy market, biodiesel was extensively produced via various catalytic and non-catalytic technologies. Conventional catalytic transesterification for biodiesel production has been shown to have limitation in terms of sensitivity to high water and free fatty acid, complicated separation and purification of biodiesel. In this study, an alternative and innovative approach was carried out via non-catalytic superheated methanol technology to produce biodiesel. Similar to supercritical reaction, the solvent need to be heated beyond the critical temperature but the reactor pressure remained at 0.1 MPa (atmospheric pressure). Transesterification reaction with superheated methanol was carried out at different reaction temperature within the limit of 270–300 °C and at different methanol flow rate ranging from 1 ml/min to 3 ml/min for 4 h. Results obtained showed that the highest biodiesel yield at 71.54% w/w was achieved at reaction temperature 290 °C and methanol flow rate at 2 ml/min with 88.81% w/w FAME content, implying the huge potential of superheated technology in producing FAME

La moral de los superhéroes

Directory of Open Access Journals (Sweden)

Jhon Rozo Mila

2015-12-01

Full Text Available Los superhéroes, el deber moral y la obligación; El caso de Spider-Man y los X-Men. Laura Victoria Bolaño Pérez; Universidad del Rosario, colección Ópera Prima, Bogotá, 2012, 309 págs.

A superconducting detector for X and gamma imagery

International Nuclear Information System (INIS)

Anon.

1981-01-01

The magnetic behavior of certain superconducting materials enables metastable states of magnetization to be obtained which can be destroyed by an external perturbation. It is this property of small semiconducting grains that is exploited in the realization of a flat matrix screen for X and gamma ray detection. This solid state matrix screen, which is made of tin grains and superconducting pins provides a directly digitized image suitable for medical and industrial application [fr

Magnetic signature of granular superconductivity in electrodeposited Pb nanowires

Energy Technology Data Exchange (ETDEWEB)

Riminucci, Alberto, E-mail: a.riminucci@bo.ismn.cnr.it [CNR, Institute for Nanostructured Materials, Via Gobetti 101, 40129 Bologna (Italy); H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Schwarzacher, Walther [H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

2014-06-14

Nanocrystalline freestanding Pb nanowires ∼200 nm in diameter were fabricated by electrodeposition into track etched polycarbonate membranes in order to study their superconducting properties. Their superconducting critical temperature, as determined by measuring the Meissner effect, was the same as for bulk Pb, but their critical field was greatly enhanced up to ∼3000 Oe. By assuming the wires consisted of spherical superconducting grains, an estimated grain size r = 60 ± 25 nm was obtained from the magnetization measured as a function of the applied magnetic field at a fixed temperature. An independent estimate for r = 47 ± 12 nm, in good agreement with the previous one, was obtained from the magnetization measured as a function of temperature at a fixed applied magnetic field. Transmission electron microscopy was used to characterize grain size at the wire edges, where a grain size in agreement with the magnetic studies was observed.

Basic aspects of high-Tc grain boundary devices

International Nuclear Information System (INIS)

Mannhart, J.; Moler, K.A.; Sigrist, M.

1996-01-01

Grain boundaries are extensively used as high-quality Josephson junctions in high-T c superconductors. Their superconducting characteristics can generally be well described by conventional models of strongly coupled Josephson junctions. Here, we report on highly anomalous critical current vs. magnetic field dependencies of grain boundaries in YBa 2 Cu 3 O 7-x . Direct imaging with scanning SQUID microscopy provides evidence of magnetic flux generated by single grain boundaries. Conventional Josephson junction models cannot explain these effects if a superconducting order parameter with a pure s-wave symmetry is assumed. The results have significant implications for our understanding of the properties of grain boundaries in high-T c superconductors and for their applications. (orig.)

Comparison of Deformation in High-Purity Single/Large Grain and Polycrystalline Niobium Superconducting Cavities

International Nuclear Information System (INIS)

Ganapati Rao Myneni; Peter Kneisel

2005-01-01

The current approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Recently, a new technique was developed at Jefferson Laboratory that enables the fabrication of single-crystal high-purity Nb SRF cavities. To better understand the differences between SRF cavities fabricated out of fine-grained polycrystalline sheet in the standard manner and single crystal cavities fabricated by the new technique, two half-cells were produced according to the two different procedures and compared using a variety of analytical techniques including optical microscopy, scanning laser confocal microscopy, profilometry, and X-ray diffraction. Crystallographic orientations, texture, and residual stresses were determined in the samples before and after forming and this poster presents the results of this ongoing study

Lifetime of superheated steam components

International Nuclear Information System (INIS)

Stoklossa, K.H.; Oude-Hengel, H.H.; Kraechter, H.J.

1974-01-01

The current evaluation schemes in use for judging the lifetime expectations of superheated steam components are compared with each other. The influence of pressure and temperature fluctuations, the differences in the strength of the wall, and the spread band of constant-strainrates are critically investigated. The distribution of these contributory effects are demonstrated in the hight of numerous measuring results. As an important supplement to these evaluation schemes a newly developed technique is introduced which is designed to calculate failure probabilities. (orig./RW) [de

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

Investigation of in-house superconducting radio-frequency 9-cell cavity made of large grain niobium at KEK

Science.gov (United States)

Dohmae, Takeshi; Umemori, Kensei; Yamanaka, Masashi; Watanabe, Yuichi; Inoue, Hitoshi

2017-12-01

The first in-house, 9-cell, superconducting radio-frequency cavity made of large grain Nb was fabricated at KEK. Some characteristic techniques were employed for the fabrication that were not used for fine grain (FG) Nb. Even though a penetrated hole was created during electron beam welding, it was successfully repaired and did not affect the cavity performance. The completed cavity then underwent vertical tests (VTs) via several surface treatment processes. A defect that caused quenches was found after a VT at 25 mm from the equator where the typical local grinding machine developed at KEK could not be utilized. A new local grinding machine using a 3D printer was thus developed for the first time, and it completely removed this defect. Finally, the cavity achieved a maximum Q0 value of 3.8 ×1010 and accelerating gradient of 38 MV/m. The obtained Q0 value is about 1.5 times higher than that for the KEK in-house FG cavity.

Production of Seamless Superconducting Radio Frequency Cavities from Ultra-fine Grained Niobium, Phase II Final Report

Energy Technology Data Exchange (ETDEWEB)

Roy Crooks, Ph.D., P.E.

2009-10-31

The positron and electron linacs of the International Linear Collider (ILC) will require over 14,000, nine-cell, one meter length, superconducting radio frequency (SRF) cavities [ILC Reference Design Report, 2007]. Manufacturing on this scale will benefit from more efficient fabrication methods. The current methods of fabricating SRF cavities involve deep drawing of the halves of each of the elliptical cells and joining them by high-vacuum, electron beam welding, with at least 19 circumferential welds per cavity. The welding is costly and has undesirable effects on the cavity surfaces, including grain-scale surface roughening at the weld seams. Hydroforming of seamless tubes avoids welding, but hydroforming of coarse-grained seamless tubes results in strain-induced surface roughening. Surface roughness limits accelerating fields, because asperities prematurely exceed the critical magnetic field and become normal conducting. This project explored the technical and economic feasibility of an improved processing method for seamless tubes for hydroforming. Severe deformation of bulk material was first used to produce a fine structure, followed by extrusion and flow-forming methods of tube making. Extrusion of the randomly oriented, fine-grained bulk material proceeded under largely steady-state conditions, and resulted in a uniform structure, which was found to be finer and more crystallographically random than standard (high purity) RRR niobium sheet metal. A 165 mm diameter billet of RRR grade niobium was processed into five, 150 mm I.D. tubes, each over 1.8 m in length, to meet the dimensions used by the DESY ILC hydroforming machine. Mechanical properties met specifications. Costs of prototype tube production were approximately twice the price of RRR niobium sheet, and are expected to be comparable with economies of scale. Hydroforming and superconducting testing will be pursued in subsequent collaborations with DESY and Fermilab. SRF Cavities are used to construct

Advances in development of Nb_{3}Sn superconducting radio-frequency cavities

Directory of Open Access Journals (Sweden)

Sam Posen

2014-11-01

Full Text Available A 1.3 GHz Nb_{3}Sn superconducting radio-frequency cavity prepared with a modified annealing step reached B_{pk}>50  mT, well above B_{c1}=25±7  mT, without the strong Q-slope observed in previous Nb_{3}Sn cavities. At 4.2 K, it has a Q_{0} of approximately 1×10^{10} at >10  MV/m, far outperforming Nb at useable gradients. At 2 K, quench occurred at ∼55  mT, apparently due to a defect, so additional treatment may increase the maximum gradient. Material parameters of the coating were extracted from Q vs T data, including a T_{c} of 18.0±0.1  K, close to the maximum literature value. High power pulses were used to reach fields far higher than in CW measurements, and near T_{c}, quench fields close to the superheating field were observed. Based on a review of previous experience with Nb_{3}Sn cavities, a speculative mechanism involving weak link grain boundaries is presented to explain how the modified annealing step could be the cause of the absence of strong Q-slope. Finally, an analysis of the progress to date provides hints that the path forward for Nb_{3}Sn cavities should focus on minimizing defects.

Gamma ray sensitivity of superheated liquid

International Nuclear Information System (INIS)

Sawamura, Teruko; Sugiyama, Noriyuki; Narita, Masakuni

2000-01-01

The superheated drop detector (SDD) is composed of droplets of sensitive liquid with a low-boiling point and a medium supporting the dispersed droplets throughout the medium. The SDD has been mainly used for neutron dosimetry and recently also for gamma-rays. While for neutrons the conditions for bubble formation have been discussed, there has been little work for gamma-rays. We investigated the conditions for low LET radiation, such as protons and gamma-rays, and showed octafluoropropane (C 3 F 8 , boiling point -36.7degC) as advantageous liquid. The bubble formation condition is given by the energy density imparted from the charged particle to the sensitive liquid. The energy density requirement means that the energy must be deposited over a definite region length, effective to produce the vapor nucleus that becomes the visible bubble. Recently for γ-rays, Evans and Wang proposed the model that the vaporization was triggered by the energy deposition in a 'cluster' including many events in proximity in a superheated liquid. Measurements of the γ-ray sensitivity have not been sufficiently carried out and therefore the effective length or the cluster model has not been well-established. In this study the detection sensitivity was evaluated by measuring the life time of a liquid drop exposed to γ-rays. We developed a device trapping a superheated drop, where a single drop of test liquid was trapped and decompressed by an acoustic standing wave field. When a liquid drop with volume V[cm 3 ] is exposed to a γ-ray flux φ γ [cm -2 s -1 ], the average evaporation rate λ(T, P) [s -1 ] (T: temperature, P: decompressed pressure) is expressed as λ(T, P)=K γ Vφ γ (1), K γ [cm -1 ] is the γ-ray detection sensitivity per unit volume of the sensitive liquid and unit fluence. If the average rate of spontaneous evaporation is λ 0 (T, P), then the probability distribution of the life time t, the probability that t > τ, is expressed by X(τ)=exp{-(λ+λ 0 )�

Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

Directory of Open Access Journals (Sweden)

Guo J.

2015-06-01

Full Text Available Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

Superheated-steam test of ethylene propylene rubber cables using a simultaneous aging and accident environment

International Nuclear Information System (INIS)

Bennett, P.R.; St Clair, S.D.; Gilmore, T.W.

1986-06-01

The superheated-steam test exposed different ethylene propylene rubber (EPR) cables and insulation specimens to simultaneous aging and a 21-day simultaneous accident environment. In addition, some insulation specimens were exposed to five different aging conditions prior to the 21-day simultaneous accident simulation. The purpose of this superheated-steam test (a follow-on to the saturated-steam tests (NUREG/CR-3538)) was to: (1) examine electrical degradation of different configurations of EPR cables; (2) investigate differences between using superheated-steam or saturated-steam at the start of an accident simulation; (3) determine whether the aging technique used in the saturated-steam test induced artificial degradation; and (4) identify the constituents in EPR that affect moisture absorption

Study of the grain boundary widening in YBaCuO superconducting ceramics induced by gamma rays

International Nuclear Information System (INIS)

Cruz Inclan, Carlos M.; Leyva Fabelo, Antonio

2001-01-01

The behavior of the thickness of the weak link with the irradiation dose was explained qualitatively and quantitatively using the migration model of the defects in the superconducting grains stimulated by the action of the gamma rays. The value of the diffusion constant associated with the migration, obtained through this model, results higher than the reported value in the literature. This difference may be associated with a notable reduction in the activation energy of the process. It was demonstrated that the variations induced by the gamma radiation in the transition width and in the critical temperature, measured by transportation methods, do not have any influence in the behavior of the intergrain link with the irradiation doses

Method of manufacturing a niobium-aluminum-germanium superconductive material

Science.gov (United States)

Wang, J.L.F.; Pickus, M.R.; Douglas, K.E.

A method for manufacturing flexible Nb/sub 3/ (Al,Ge) multifilamentary superconductive material in which a sintered porous Nb compact is infiltrated with an Al-Ge alloy. It is deformed and heat treated in a series of steps at successively higher temperatures preferably below 1000/sup 0/C during the heat treatment, cladding material such as copper can be applied to facilitate a deformation step preceding the heat treatment and can remain in place through the heat treatment to serve as a temperature stabilizer for the superconductive material produced. These lower heat treatment temperatures favor formation of filaments with reduced grain size and with more grain boundaries which in turn increase the current-carrying capacity of the superconductive material.

Automatic read out system for superheated emulsion based neutron detector

International Nuclear Information System (INIS)

Meena, J.P.; Parihar, A.; Vaijapurkar, S.G.; Mohan, Anand

2010-01-01

Full text: Defence Laboratory, Jodhpur (DLJ) has developed superheated emulsion technology for neutron and gamma measurements. The laboratory has attempted to develop reader system to display neutron dose and dose rate based on acoustic technique. The paper presents a microcontroller based automatic reader system for neutron measurements using indigenously developed superheated emulsion detector. The system is designed for real time counting of bubbles formed in superheated emulsion detector. A piezoelectric transducer is used for sensing bubble acoustic. The front end of system is mainly consisting of specially designed signal conditioning unit consisted of piezoelectric transducer, an amplifier, a high-pass filter, a differentiator, a comparator and monostable multivibrator. The system is based on PIC 18F6520 microcontroller having large internal SRAM, 10-bit internal ADC, I 2 C interface, UART/USART modules. The paper also describes the design of following peripheral units interfaced to microcontroller temperature and battery monitoring, display, keypad and a serial communication. The reader system measures and displays neutron dose and dose rate, number of bubble and elapsed time. The developed system can be used for detecting very low neutron leakage in the accelerators, nuclear reactors and nuclear submarines. The important features of system are compact, light weight, cost effective and high neutron sensitivity. The prototype was tested and evaluated by exposing to 241 Am-Be neutron source and results have been reported

Investigation of inter-grain critical current density in Bi2Sr2CaCu2O8+δ superconducting wires and its relationship with the heat treatment protocol

Science.gov (United States)

Pallecchi, I.; Leveratto, A.; Braccini, V.; Zunino, V.; Malagoli, A.

2017-09-01

In this work we investigate the effect of each different heat treatment stage in the fabrication of Bi2Sr2CaCu2O8+δ superconducting wires on intra-grain and inter-grain superconducting properties. We measure magnetic critical temperature T c values and transport critical current density J c at temperatures from 4 K to 40 K and in fields up to 7 T. From an analysis of the temperature dependence of the self-field critical current density J c(T) that takes into account weak link behavior and the proximity effect, we study grain boundary (GB) transparency to supercurrents; we also establish a relationship between GB oxygenation in the different steps of the fabrication process and GB transparency to supercurrents. We find that GB oxygenation starts in the first crystallization stage, but it becomes complete in the plateau at 836 °C and in slow cooling stages and is further enhanced in the prolonged post-annealing step. Such oxygenation makes GBs more conductive, thus improving the inter-grain J c value and temperature dependence. On the other hand, from inspection of the T c values in the framework of the phase diagram dome, we find that grains are already oxygenated in the crystallization step up to the optimal doping, while successive slow cooling and post-annealing treatments further enhance the degree of overdoping, especially if carried out in oxygen atmosphere rather than in air.

Large, real time detectors for solar neutrinos and magnetic monopoles

International Nuclear Information System (INIS)

Gonzalez-Mestres, L.

1990-01-01

We discuss the present status of superheated superconducting granules (SSG) development for the real time detection of magnetic monopoles of any speed and of low energy solar neutrinos down to the pp region (indium project). Basic properties of SSG and progress made in the recent years are briefly reviewed. Possible ways for further improvement are discussed. The performances reached in ultrasonic grain production at ∼ 100 μm size, as well as in conventional read-out electronics, look particularly promising for a large scale monopole experiment. Alternative approaches are briefly dealt with: induction loops for magnetic monopoles; scintillators, semiconductors or superconducting tunnel junctions for a solar neutrino detector based on an indium target

Semi-automatic bubble counting system for superheated droplet detectors

International Nuclear Information System (INIS)

Reina, Luiz C.; Bellido, Luis F.; Ramos, Paulo R.; Silva, Ademir X. da; Facure, Alessandro; Dantas, Jose E.R.

2009-01-01

Neutron dose rate measurements are normally performed by means of PADC, CR-39 and TLD detectors. Although, none of these devices can give instant reading of the neutron dose, recently new kind of detectors are being developed, based on the formation of tiny drops in a superheated liquid suspended in a polymer or gel solution, called superheated droplet detector (SDD) or also as bubble detectors (BD), with no response for gamma radiation. This work describes the experimental setup and the developed procedures for acquiring and processing digital images obtained with bubble detector spectrometer (BDS), developed by Bubble Technology Industries, for personal neutron dosimeter and/or neutron energy fluence measurements in nuclear facilities. The results of the neutron measurements obtained during the F-18 production, at the RDS-111 cyclotron, are presented. These neutron measurements were the first ones with this type of BDS detectors in a particle accelerator facility in Brazil and it was very important to estimate neutron dose rate received by occupationally exposed individuals. (author)

The active personnel dosimeter---APFEL enterprises superheated drop detector

International Nuclear Information System (INIS)

Ipe, N.E.; Donahue, R.J.; Busick, D.D.

1991-03-01

The Active Personnel Dosimeter (APD) provides a digital readout of events caused by neutrons interacting with superheated liquid droplets. The droplets are suspended in a gel held in a replaceable cartridge. Upon neutron interaction, the superheated droplet vaporizes, forming a bubble. The sound produced in this process is recorded by transducers that sense the accompanying pressure pulse. The APD electronically discriminates against spurious noise and vibration. Studies with the production prototype APDs indicate that the detector response is linear up to about 0.40 mSv, with large variations sometimes from predicted values and between cartridges at higher dose equivalents. The response to standard neutron sources (bare 252 Cf, PuBe, PuB, PuF, PuLi) is reported and compared with the expected response. Unirradiated cartridges self-nucleate when heated to temperatures of 46 degrees C. The APD is insensitive to low-energy photons but responds to high-energy photons and electrons. 8 refs., 2 figs., 3 tabs

Comparative Study on the Effects of Boiling, Steaming, Grilling, Microwaving and Superheated Steaming on Quality Characteristics of Marinated Chicken Steak

Science.gov (United States)

Choi, Yun-Sang; Kim, Young-Boong; Jeon, Ki-Hong; Kim, Eun-Mi; Sung, Jung-Min; Kim, Hyun-Wook

2016-01-01

The effects of five different cooking methods (boiling, steaming, grilling, microwaving, and superheated steaming) on proximate composition, pH, color, cooking loss, textural properties, and sensory characteristics of chicken steak were studied. Moisture content and lightness value (L*-value) were higher in superheated steam cooked chicken steak than that of the other cooking treatments such as boiling, steaming, grilling and microwaving cooking (pcooked chicken steak was lower than that in the other cooking treatments (pchicken steak cooked using various methods (p>0.05). Among the sensory characteristics, tenderness score, juiciness score and overall acceptability score were the highest for the superheated steam samples (p0.05). These results show that marinated chicken steak treated with superheated steam in a preheated 250℃ oven and 380℃ steam for 5 min until core temperature reached 75℃ improved the quality characteristics and sensory properties the best. Therefore, superheated steam was useful to improve cooked chicken steak. PMID:27499656

PREFACE PASREG: The 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials (Washington DC, 29-31 July 2010) PASREG: The 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials (Washington DC, 29-31 July 2010)

Science.gov (United States)

Freyhardt, Herbert; Cardwell, David; Strasik, Mike

2010-12-01

Large grain, (RE)BCO bulk superconductors fabricated by top seeded melt growth (TSMG) are able to generate large magnetic fields compared to conventional, iron-based permanent magnets. Following 20 years of development, these materials are now beginning to realize their considerable potential for a variety of engineering applications such as magnetic separators, flywheel energy storage and magnetic bearings. MgB2 has also continued to emerge as a potentially important bulk superconducting material for engineering applications below 20 K due to its lack of granularity and the ease with which complex shapes of this material can be fabricated. This issue of Superconductor Science and Technology contains a selection of papers presented at the 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials, including MgB2, held 29th-31sy July 2010 at the Omni Shoreham Hotel, Washington DC, USA, to report progress made in this field in the previous three year period. The workshop followed those held previously in Cambridge, UK (1997), Morioka, Japan (1999), Seattle, USA (2001), Jena, Germany (2003), Tokyo, Japan (2005) and again in Cambridge, UK (2007). The scope of the seventh PASREG workshop was extended to include processing and characterization aspects of the broader spectrum of bulk high temperature superconducting (HTS) materials, including melt-cast Bi-HTS and bulk MgB2, recent developments in the field and innovative applications of bulk HTS. A total of 38 papers were presented at this workshop, of which 30 were presented in oral form and 8 were presented as posters. The organizers wish to acknowledge the efforts of Sue Butler of the University of Houston for her local organization of the workshop. The eighth PASREG workshop will be held in Taiwan in the summer of 2012.

BOILER-SUPERHEATED REACTOR

Science.gov (United States)

Heckman, T.P.

1961-05-01

A nuclear power reactor of the type in which a liquid moderator-coolant is transformed by nuclear heating into a vapor that may be used to drive a turbo- generator is described. The core of this reactor comprises a plurality of freely suspended tubular fuel elements, called fuel element trains, within which nonboiling pressurized liquid moderator-coolant is preheated and sprayed through orifices in the walls of the trains against the outer walls thereof to be converted into vapor. Passage of the vapor ovcr other unwetted portions of the outside of the fuel elements causes the steam to be superheated. The moderatorcoolant within the fuel elements remains in the liqUid state, and that between the fuel elements remains substantiaily in the vapor state. A unique liquid neutron-absorber control system is used. Advantages expected from the reactor design include reduced fuel element failure, increased stability of operation, direct response to power demand, and circulation of a minimum amount of liquid moderatorcoolant. (A.G.W.)

Bubble dynamics in a superheated liquid

International Nuclear Information System (INIS)

Sha, W.T.; Shah, V.L.

1977-09-01

The report presents an extensive literature survey on bubble dynamics. Growth of a single spherical bubble moving in a uniformly superheated liquid is considered. Equations of motion and energy are presented in the forms that take into consideration the interaction between the motion and the growth. The fourth-order Runge-Kutta method is used to obtain a simultaneous solution of equations of motion and growth rate, and the solution is compared with available experimental results. Results for liquid sodium are presented for a range of pressures and Jakob numbers

Atomization of Impinging Droplets on Superheated Superhydrophobic Surfaces

Science.gov (United States)

Emerson, Preston; Crockett, Julie; Maynes, Daniel

2017-11-01

Water droplets impinging smooth superheated surfaces may be characterized by dynamic vapor bubbles rising to the surface, popping, and causing a spray of tiny droplets to erupt from the droplet. This spray is called secondary atomization. Here, atomization is quantified experimentally for water droplets impinging superheated superhydrophobic surfaces. Smooth hydrophobic and superhydrophobic surfaces with varying rib and post microstructuring were explored. Each surface was placed on an aluminum heating block, and impingement events were captured with a high speed camera at 3000 fps. For consistency among tests, all events were normalized by the maximum atomization found over a range of temperatures on a smooth hydrophobic surface. An estimate of the level of atomization during an impingement event was created by quantifying the volume of fluid present in the atomization spray. Droplet diameter and Weber number were held constant, and atomization was found for a range of temperatures through the lifetime of the impinging droplet. The Leidenfrost temperature was also determined and defined to be the lowest temperature at which atomization ceases to occur. Both atomization and Leidenfrost temperature increase with decreasing pitch (distance between microstructures).

Influence of pulse electric current on structure and superconducting properties of high temperature superconductor

International Nuclear Information System (INIS)

Rajchenko, A.I.; Flis, A.A.; Chernenko, L.I.; Kryuchkova, N.I.

1998-01-01

The influence of high-density pulse current treatment at room temperature on structure and superconducting properties of HTSC Y Ba 2 Cu 3 O x ceramics is studied. The structures of the samples are found to undergo appreciable changes as the density of pulse current is gradually increased from its minimum value; as a certain threshold value is attained, there occurs a melting-off of coarse grains with a partial destroying of intergrain contact areas followed by superconductivity loss. A further increase in the treatment current density results in a restoration of the superconducting properties probably due to the occurrence of aligned-with-current superconducting bridges between the melted-off grains. The superconducting transition temperature in the samples does not charge but subsequent thermal treatment causes this temperature to increase

New developments on transition radiation detectors using superconducting granules

International Nuclear Information System (INIS)

Yuan, L.C.L.

1977-01-01

By raising slightly either the temperature or the magnetic field to above that of the critical temperature or the critical magnetic field, the type I superconducting granules would still remain in the superconducting state which becomes a metastable state and is called the superheated superconducting state. If a relativistic charged particle incident on such a granule which is located in a colloidal suspension has imported to it an energy that is above the threshold energy (for state flipping) of the granule then it would flip to the normal state. The threshold energy of a granule is a function of the square of its radius, whereas the energy loss of a charged particle due to ionization is linearly proportional to the radius. The size of the granule can be pre-determined to be such that its threshold energy is slightly above the ionization loss of a relativistic charged particle. Then the traversal of the charged particle through such a granule would not affect the superconducting state of the granule unless a transition x-ray radiation is emitted at the surface of the granule by the traversing particle and the x-ray transition radiation is immediately absorbed either in total or partially by the metallic granule causing it to flip to the normal state. The total intensity of the x-ray transition radiation is linearly proportional to the Lorentz factor γ of the traversing particle, and the number of granules flipped would also be a measure of γ. Three methods for detecting the flipping of granules from the superconducting state to the normal state are described. They include the frequency measuring method, the SQUID method, and the pulse method with low noise amplifier system

Surface morphology of laser superheated Pb(100)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Z.H.; Lin, B.; Elsayed-Ali, H.E.

1999-11-01

The change in the surface vacancy density after heating of Pb(100) with {approximately}100 ps laser pulses is investigated using reflection high-energy electron diffraction. The surface vacancy density remains unchanged when the surface is superheated without melting. However, when the laser fluence is high enough to cause surface melting, the surface vacancy density increases. This increase in vacancy density is attributed to fast diffusion of atoms in the liquid film formed on Pb(100) during laser melting.

Superconducting oxide thin films by ion beam sputtering

International Nuclear Information System (INIS)

Kobrin, P.H.; DeNatale, J.F.; Housley, R.M.; Flintoff, J.F.; Harker, A.B.

1987-01-01

Superconducting thin films of ternary copper oxides from the Y-Ba-Cu-O and La-Sr-Cu-O systems have been deposited by ion beam sputtering of ceramic targets. Crystallographic orientation of the polycrystalline films has been shown to vary with substrate identity, deposition temperature and annealing temperature. The onset of the superconductive transition occurs near 90K in the Y-Ba-Cu-O system. Fe impurities of < 0.2% have been found to inhibit the superconducting transition, probably by migrating to the grain boundaries

Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity

Science.gov (United States)

Dhakal, P.; Ciovati, G.; Myneni, G. R.; Gray, K. E.; Groll, N.; Maheshwari, P.; McRae, D. M.; Pike, R.; Proslier, T.; Stevie, F.; Walsh, R. P.; Yang, Q.; Zasadzinzki, J.

2013-04-01

Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of “medium purity” Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800-1400°C was done in a newly designed vacuum induction furnace. Q0 values of the order of 2×1010 at 2.0 K and peak surface magnetic field (Bp) of 90 mT were achieved reproducibly. A Q0 value of (5±1)×1010 at 2.0 K and Bp=90mT was obtained after heat treatment at 1400°C. This is the highest value ever reported at this temperature, frequency, and field. Samples heat treated with the cavity at 1400°C were analyzed by secondary ion mass spectrometry, x-ray photoelectron spectroscopy, energy dispersive x ray, point-contact tunneling, and x-ray diffraction, and revealed a complex surface composition which includes titanium oxide, increased carbon, and nitrogen content but reduced hydrogen concentration compared to a non-heat-treated sample.

A novel transition radiation detector utilizing superconducting microspheres for measuring the energy of relativistic high-energy charged particles

International Nuclear Information System (INIS)

Yuan, Luke C.L.; Chen, C.P.; Huang, C.Y.; Lee, S.C.; Waysand, G.; Perrier, P.; Limagne, D.; Jeudy, V.; Girard, T.

2000-01-01

A novel transition radiation detector (TRD) utilizing superheated superconducting microspheres of tin of 22-26, 27-32 and 32-38 μm in diameter, respectively, has been constructed which is capable of measuring accurately the energy of relativistic high-energy charged particles. The test has been conducted in a high-energy electron beam facility at the CERN PS in the energy range of 1-10 GeV showing an energy dependence of the TR X-ray photon produced and hence the value γ=E/mc 2 of the charged particle

Quench cooling of superheated debris beds in containment during LWR core meltdown accidents

International Nuclear Information System (INIS)

Ginsberg, T.; Chen, J.C.

1984-01-01

Light water reactor core meltdown accident sequence studies suggest that superheated debris beds may settle on the concrete floor beneath the reactor vessel. A model for the heat transfer processes during quench of superheated debris beds cooled by an overlying pool of water has been presented in a prior paper. This paper discusses the coolability of decay-heated debris beds from the standpoint of their transient quench characteristics. It is shown that even though a debris bed configuration may be coolable from the point of view of steady-state decay heat removal, the quench behavior from an initially elevated temperature may lead to bed melting prior to quench of the debris

Superheating in nucleate boiling calculated by the heterogeneous nucleation theory

International Nuclear Information System (INIS)

Gerum, E.; Straub, J.; Grigull, U.

1979-01-01

With the heterogeneous nucleation theory the superheating of the liquid boundary layer in nucleate boiling is described not only for the onset of nuclear boiling but also for the boiling crisis. The rate of superheat depends on the thermodynamic stability of the metastable liquid, which is influenced by the statistical fluctuations in the liquid and the nucleation at the solid surface. Because of the fact that the cavities acting as nuclei are too small for microscopic observation, the size and distribution function of the nuclei on the surface necessary for the determination of the probability of bubble formation cannot be detected by measuring techniques. The work of bubble formation reduced by the nuclei can be represented by a simple empirical function whose coefficients are determined from boiling experiments. Using this the heterogeneous nucleation theory describes the superheating of the liquid. Several fluids including refrigerants, liquid gases, organic liquids and water were used to check the theory. (author)

Numerical simulation of superheated vapor bubble rising in stagnant liquid

Science.gov (United States)

Samkhaniani, N.; Ansari, M. R.

2017-09-01

In present study, the rising of superheated vapor bubble in saturated liquid is simulated using volume of fluid method in OpenFOAM cfd package. The surface tension between vapor-liquid phases is considered using continuous surface force method. In order to reduce spurious current near interface, Lafaurie smoothing filter is applied to improve curvature calculation. Phase change is considered using Tanasawa mass transfer model. The variation of saturation temperature in vapor bubble with local pressure is considered with simplified Clausius-Clapeyron relation. The couple velocity-pressure equation is solved using PISO algorithm. The numerical model is validated with: (1) isothermal bubble rising and (2) one-dimensional horizontal film condensation. Then, the shape and life time history of single superheated vapor bubble are investigated. The present numerical study shows vapor bubble in saturated liquid undergoes boiling and condensation. It indicates bubble life time is nearly linear proportional with bubble size and superheat temperature.

Critical current of high Tc superconducting Bi223/Ag tapes

NARCIS (Netherlands)

Huang, Y.; ten Haken, Bernard; ten Kate, Herman H.J.

1998-01-01

The magnetic field dependence of the critical current of various high Tc superconducting Bi2223/Ag tapes indicates that the transport current is carried through two paths: one is through weakly-linked grain boundaries (Josephson junctions); another is through well-connected grains. The critical

A MATHEMATICAL MODEL OF THE ROASTING CHESTNUTS PROCESS BY SUPERHEATED STEAM

Directory of Open Access Journals (Sweden)

A. N. Ostrikov

2013-01-01

Full Text Available The mathematic modeling for chestnuts roasting process by superheated steam is conducted. Diffusion and thermal diffusion coefficients are used for process description. Initial conditions and boundary conditions of the third kind for thermal conductivity and mass transfer equations are set.

Automatic readout system for superheated emulsion based neutron detector

International Nuclear Information System (INIS)

Meena, J.P.; Parihar, A.; Vaijapurkar, S.G.; Mohan, Anand

2011-01-01

The paper presents a microcontroller based automatic reader system for neutron measurement using indigenously developed superheated emulsion detector. The system is designed for real time counting of bubbles formed in superheated emulsion detector. A piezoelectric transducer is used for sensing bubble acoustic during the nucleation. The front end of system is mainly consisting of specially designed signal conditioning unit, piezoelectric transducer, an amplifier, a high-pass filter, a differentiator, a comparator and monostable multivibrator. The system is based on PlC 18F6520 microcontroller having large internal SRAM, 10-bit internal ADC, I 2 C interface, UART/USART modules. The paper also describes the design of following microcontroller peripheral units viz temperature monitoring, battery monitoring, LCD display, keypad and a serial communication. The reader system measures and displays neutron dose and dose rate, number of bubble and elapsed time. The developed system can be used for detecting very low neutron leakage in the accelerators, nuclear reactors and nuclear submarines. The important features of system are compact, light weight, cost effective and high neutron sensitivity. The prototype was tested and evaluated by exposing to 241 Am-Be neutron source and results have been reported. (author)

Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity

Directory of Open Access Journals (Sweden)

P. Dhakal

2013-04-01

Full Text Available Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of “medium purity” Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800–1400°C was done in a newly designed vacuum induction furnace. Q_{0} values of the order of 2×10^{10} at 2.0 K and peak surface magnetic field (B_{p} of 90 mT were achieved reproducibly. A Q_{0} value of (5±1×10^{10} at 2.0 K and B_{p}=90  mT was obtained after heat treatment at 1400°C. This is the highest value ever reported at this temperature, frequency, and field. Samples heat treated with the cavity at 1400°C were analyzed by secondary ion mass spectrometry, x-ray photoelectron spectroscopy, energy dispersive x ray, point-contact tunneling, and x-ray diffraction, and revealed a complex surface composition which includes titanium oxide, increased carbon, and nitrogen content but reduced hydrogen concentration compared to a non-heat-treated sample.

Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity

Energy Technology Data Exchange (ETDEWEB)

Dhakal, P.; Ciovati, G.; Myneni, G. R.; Gray, K. E.; Groll, N.; Maheshwari, P.; McRae, D. M.; Pike, R.; Proslier, T.; Stevie, F.; Walsh, R. P.; Yang, Q.; Zasadzinzki, J.

2013-04-01

Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of “medium purity” Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800–1400°C was done in a newly designed vacuum induction furnace. Q{sub 0} values of the order of 2×10{sup 10} at 2.0 K and peak surface magnetic field (B{sub p}) of 90 mT were achieved reproducibly. A Q{sub 0} value of (5±1)×10{sup 10} at 2.0 K and B{sub p}=90mT was obtained after heat treatment at 1400°C. This is the highest value ever reported at this temperature, frequency, and field. Samples heat treated with the cavity at 1400°C were analyzed by secondary ion mass spectrometry, x-ray photoelectron spectroscopy, energy dispersive x ray, point-contact tunneling, and x-ray diffraction, and revealed a complex surface composition which includes titanium oxide, increased carbon, and nitrogen content but reduced hydrogen concentration compared to a non-heat-treated sample.

Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

Science.gov (United States)

Zhao, Xin; Ciovati, G.; Bieler, T. R.

2010-12-01

The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced by crystal defects (e.g. dislocations). All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. The local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observed degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.

Percolation modelling for highly aligned polycrystalline superconducting tapes

Energy Technology Data Exchange (ETDEWEB)

Rutter, N A; Glowacki, B A; Evetts, J E [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); IRC in Superconductivity, Madingley Road, Cambridge CB3 0HE (United Kingdom)

2000-11-01

Surface and bulk texture measurements have been carried out on highly aligned NiFe tapes, suitable for use as coated conductor substrates. Data from small-area electron backscatter diffraction measurements are compared with those from bulk x-ray analysis in the development of a two-dimensional percolation model, and the two are shown to give very similar results. No evidence of grain-to-grain correlation is found. The model is then developed to assess how the properties of a superconducting layer grown epitaxially on buffered tapes will depend on parameters such as sample size, grain size and the extent of grain alignment. (author)

Quench cooling of superheated debris beds in containment during LWR core meltdown accidents

International Nuclear Information System (INIS)

Ginsberg, T.; Chen, J.C.

1984-01-01

Light water reactor core meltdown accident sequence studies suggest that superheated debris beds may settle on the concrete floor beneath the reactor vessel. A model for the heat transfer processes during quench (removal of stored energy from initial temperature to saturation temperature) of superheated debris beds cooled by an overlying pool of water has been presented in a prior paper. This paper discusses the coolability of decay-heated debris beds from the standpoint of their transient quench characteristics. It is shown that even though a debris bed configuration may be coolable from the point of view of steady-state decay heat removal, the quench behavior from an initially elevated temperature may lead to bed melting prior to quench of the debris

High-Tc superconductivity of Tl-Ba-Ca-Cu-O samples

International Nuclear Information System (INIS)

Porjesz, T.; Kirschner, I.; Kovacs, G.

1988-08-01

A TlBaCaCuO 4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the sample exhibits superconductivity with an onset of 121 K and zero resistivity of 106 K and the other part of them shows a sharp drop in resistivity at 130 K which hints at an existence of superconducting grains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of critical magnetic fields. (author). 5 refs, 6 figs

Microwave super-heated boiling of organic liquids: Origin, effect and application

NARCIS (Netherlands)

Chemat, F.; Esveld, E.

2001-01-01

This paper reports the state of the art of the microwave super-heated boiling phenomenon. When a liquid is heated by microwaves, the temperature increases rapidly to reach a steady temperature while refluxing. It happens that this steady state temperature can be up to 40 K higher than the boiling

New safety experiments in decommissioned superheated steam reactor at Karlstein

International Nuclear Information System (INIS)

Koerting, K.

1986-01-01

This article gives a concise summary of the Status Report of the Superheated Steam Reactor Safety Program (PHDR) Project, held at KfK on Dec. 5, 1985. The results discussed dealt with fire experiments, shock tests simulating airplane crashes, temperature shocks in the reactor pressure vessel, studies of crack detection in pressure vessels and blasting experiments associated with nuclear plant decommissioning

Coexistence of superconductivity and superparamagnetism in Pb-Co electrodeposited nanowires

Energy Technology Data Exchange (ETDEWEB)

Riminucci, Alberto [CNR-ISMN, Bologna (Italy); H.H.Wills Physics Laboratory, Bristol (United Kingdom); Schwarzacher, Walther [H.H.Wills Physics Laboratory, Bristol (United Kingdom)

2017-03-15

Pb-Co nanowires were electrodeposited in 100 nm nominal pore diameter polycarbonate membranes. Above the T{sub C} of Pb we modelled the behaviour of the wires with a Langevin function, obtaining a Co volume of (1.06 ± 0.01) x 10{sup -7} cm{sup 3} divided into clusters of ∼10 atoms in size. The magnetic response of the wires in the 3-10 K interval, which comprises T{sub C}, was modelled by adding spherical superconducting Pb grains to the Co clusters; the Pb grains were found to be (87 ± 6) nm in diameter. The Co clusters were not interacting and were not magnetically screened by the superconducting Pb. (orig.)

Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

Directory of Open Access Journals (Sweden)

Xin Zhao

2010-12-01

Full Text Available The performance of superconducting radio-frequency (SRF resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots” were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD, and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced by crystal defects (e.g. dislocations. All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. The local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observed degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.

A process for superheating steam in a nuclear power station circuit and device for putting in operation this process

International Nuclear Information System (INIS)

Monteil, Marcel; Forestier, Jean; Leblanc, Bernard; Monteil, Pierre

1975-01-01

A process is described for superheating steam in a nuclear power station circuit, comprising a turbine with a high pressure chamber and a low pressure chamber. It consists in superheating the steam between the high and low pressure chambers of the turbine by using as heating fluid water under pressure at vaporisation temperature, directly taken from the recirculation or circulation flow water of the reactor or of the steam generators. The process is adapted to a pressurised water reactor using a once-through steam generator comprising in succession an economiser, a vaporiser and a superheater, the superheating water being taken at the vaporiser intake. It is also adapted for a boiling water reactor, in that the water is taken directly from the reactor vessel and at a suitable level in the recirculation water [fr

Sound speed of isobaric heat capacity in the saturated and superheated vapour of cesium, rubidium and potassium

International Nuclear Information System (INIS)

Novikov, I.I.; Roschupkin, V.V.

1985-01-01

The paper reviews the work carried out on the thermodynamic properties of alkali metal vapours. The most systematic investigations concern the sound velocity measurements for saturated and superheated vapours of caesium, for saturated vapour of rubidium, and for superheated vapour of potassium. The Joule-Thompson coefficient has been studied in caesium vapour, and the isobaric heat capacity of potassium vapour has also been examined. The experimental methods for all these experiments are described, and the data obtained are presented in tabular form. (U.K.)

Reduction of metal oxides in metal carbide fusion superheated with plasma

Energy Technology Data Exchange (ETDEWEB)

Hedai, L

1981-01-01

A significant part of metals is capable of binding a high quantity of carbon in the form of carbide. The carbide fusion produced as a result of smelting and superheating, metal carbides with the use of plasma might be a medium to be utilized for the reduction of different metal oxides, whilst also the original carbide structure of the metal carbides will be reduced to metallic structure. The experiments conducted by making use of plasma equipment, of 20, 55 and 100 kW performances are described. On the basis of the results of the experiments performed, the following statements are to be made. The oxide reductions taking place in the metal carbide fusion might also be carried out in open-hearth furnaces, because reducing atmosphere is not necessitated during this procedure. The quantity of energy required is basically defined by the energy needed for smelting and superheating the metal carbide. The method for producing the metal described may be mainly applied for the allied production of high-purity steels as well as for that of ferro-alloys.

Proof of the Parr Formula for the superheating field

CERN Document Server

Del Castillo, P

2003-01-01

In \\cite{BoHe4}, in order to prove the De Gennes Formula \\cite{Ge1966}, C. Bolley and B. Helffer have obtained an upper bound for the superheating field $h^{sh}(\\ka)$ in a semi-infinite film in the weak-$\\kappa$ limit. Precisely, they have proved that $\\ka \\left(h^{sh}(\\ka)\\right)^2\\leq 2^{-\\frac{3}{2}}+\\mathcal{O}(\\ka^{\\frac{1}{2}}).$ In this paper, we improve this result and get the upper bound

El auge del género de superhéroes y la nueva industria cinematográfica global

Directory of Open Access Journals (Sweden)

Vicente GARCÍA-ESCRIVÁ

2018-01-01

Full Text Available Proveniente del mundo del cómic, la figura del superhéroe debutó con éxito en el cine a finales de la década de los 70. Sin embargo, ha sido durante los últimos quince años cuando esta figura ha cobrado un extraordinario protagonismo y, en sus múltiples variantes, ha dado pie a buena parte de las franquicias cinematográficas que en la actualidad dominan las salas de cine de todo el planeta. Al hilo de este nuevo paisaje fílmico, el presente artículo se propone explorar la naturaleza del cine de superhéroes, un apabullante espectáculo audiovisual que es consumido por millones de espectadores en todo el mundo, con especial incidencia entre el público infantil y juvenil. Tal indagación conduce a examinar las narrativas desplegadas en estas series de películas, así como a analizar la propia figura del superhéroe en el contexto de un cine saturado de efectos visuales y acción trepidante. Finalmente, el artículo trata de señalar las razones de fondo que han llevado a la industria de Hollywood a apostar por el género de superhéroes como fórmula recurrente para atraer al público a las salas de cine.

Development of a new pressure dependent threshold superheated drop detector for neutrons

Energy Technology Data Exchange (ETDEWEB)

Rezaeian, Peiman [Radiation Applications Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 11365-3486, Tehran (Iran, Islamic Republic of); Raisali, Gholamreza, E-mail: graisali@aeoi.org.ir [Radiation Applications Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 11365-3486, Tehran (Iran, Islamic Republic of); Akhavan, Azam [Radiation Applications Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 11365-3486, Tehran (Iran, Islamic Republic of); Ghods, Hossein [Physics and Accelerators Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 11365-3486, Tehran (Iran, Islamic Republic of); Hajizadeh, Bardia [Radiation Protection Division, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)

2015-03-11

In this paper, a set of superheated drop detectors operated at different pressures is developed and fabricated by adding an appropriate amount of Freon-12 liquid on the free surface of the detector. The fabricated detectors have been used for determination of the threshold pressure for 2.89 MeV neutrons of a neutron generator in order to estimate the thermodynamic efficiency. Finally, knowing the thermodynamic efficiency of the detector and in a similar manner, the threshold pressure for {sup 241}Am–Be neutrons is determined and accordingly, the maximum neutron energy of the source spectrum is estimated. The maximum neutron energy of the {sup 241}Am–Be is estimated as 10.97±2.11 MeV. The agreement between this measured maximum energy and the reported value of the {sup 241}Am–Be neutron source shows that the method developed to apply pressure on the superheated drop detectors can be used to control the energy threshold of these detectors.

Development of a new pressure dependent threshold superheated drop detector for neutrons

International Nuclear Information System (INIS)

Rezaeian, Peiman; Raisali, Gholamreza; Akhavan, Azam; Ghods, Hossein; Hajizadeh, Bardia

2015-01-01

In this paper, a set of superheated drop detectors operated at different pressures is developed and fabricated by adding an appropriate amount of Freon-12 liquid on the free surface of the detector. The fabricated detectors have been used for determination of the threshold pressure for 2.89 MeV neutrons of a neutron generator in order to estimate the thermodynamic efficiency. Finally, knowing the thermodynamic efficiency of the detector and in a similar manner, the threshold pressure for 241 Am–Be neutrons is determined and accordingly, the maximum neutron energy of the source spectrum is estimated. The maximum neutron energy of the 241 Am–Be is estimated as 10.97±2.11 MeV. The agreement between this measured maximum energy and the reported value of the 241 Am–Be neutron source shows that the method developed to apply pressure on the superheated drop detectors can be used to control the energy threshold of these detectors

On the superconducting phase diagram of high Tc superconductors

International Nuclear Information System (INIS)

de la Cruz, F.

1990-01-01

The tendency of oxide superconductors to show granularity has been pointed out since the beginning of research on superconductivity in this type of materials. Nevertheless, only very recently the full phase diagram and characteristics of the grains have been determined. In this paper, the authors review and discuss the different critical fields and their relation to the transport of superconducting current. The superconducting response of single crystals of High Tc superconductors is discussed. Special attention is devoted to the behavior of the vortex lattice and, in particular, to the recent discovery of the quenching of H c1 in YBaCuO, several degrees below Tc

Superconducting-electromagnetic hybrid bearing using YBCO bulk blocks for passive axial levitation

Science.gov (United States)

Nicolsky, R.; de Andrade, R., Jr.; Ripper, A.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Gawalek, W.; Habisreuther, T.; Strasser, T.

2000-06-01

A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90° from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.

Use of basic principle of nucleation in determining temperature-threshold neutron energy relationship in superheated emulsions

CERN Document Server

Das, M; Chatterjee, B K; Roy, S C

2003-01-01

Detection of neutrons through use of superheated emulsions has been known for about two decades. The minimum neutron energy (threshold) required to nucleate drops of a given liquid has a dependence on the temperature of the liquid. The basic principle of nucleation has been utilized to find the relationship between the operating temperature and threshold neutron energy for superheated emulsions made of R-114 liquid. The threshold energy thus determined for different temperatures has been compared with accurate experimental results obtained using monoenergetic neutron sources. The agreement is found to be satisfactory and confirms the applicability of the present simple method to other liquids.

Fabrication of superconducting wire using organometallic precursors and infiltration

International Nuclear Information System (INIS)

Lee, Y.J.

1991-01-01

Organometallic precursors from naphthenic acid and metal nitrates were used for the synthesis of YBCO oxide superconducting compounds. The characteristics of metal naphthenates as organometallic precursors were investigated by IR spectra, viscosity measurements, and infiltration. 123 superconducting compound obtained from 123 naphthenate showed a Tc of 90 degree K and a rather dense and elongated microstructure. Also, the melting behavior of Ba-cuprates which were used for 123 making was studied. A low-temperature melting process was developed to fabricate silver-sheathed superconducting wire with the powder-in-tube method; flowing argon gas is introduced to the system at 930-945 degree C to reduce the melting temperature of the 123 compound without silver sheath melting. It resulted in a 90 degree K Tc superconducting core with dense and locally aligned microstructure. SEM-EDS and XRD analysis, 4-probe resistance and Jc measurements, and carbon-content determinations were carried out to characterize the microstructure, grain alignment, and superconducting properties of the samples

Grain boundary effects in nanocrystalline diamond

Czech Academy of Sciences Publication Activity Database

Mareš, Jiří J.; Hubík, Pavel; Krištofik, Jozef; Nesládek, Miloš

2008-01-01

Roč. 205, č. 9 (2008), 2163-2168 ISSN 1862-6300 R&D Projects: GA ČR(CZ) GA202/06/0040 Institutional research plan: CEZ:AV0Z10100521 Keywords : diamond film * grain boundary * superconductivity * noise * ballistic transport Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.205, year: 2008

LET dependence of bubbles evaporation pulses in superheated emulsion detectors

Energy Technology Data Exchange (ETDEWEB)

Di Fulvio, Angela; Huang, Jean; Staib, Lawrence [Yale University, Department of Diagnostic Radiology, TAC N140, New Haven, CT 06520-8043 (United States); D’Errico, Francesco [Yale University, Department of Diagnostic Radiology, TAC N140, New Haven, CT 06520-8043 (United States); Scuola di Ingegneria, Universitá di Pisa, Largo Lucio Lazzarino 1, Pisa (Italy)

2015-06-01

Superheated emulsion detectors are suspensions of metastable liquid droplets in a compliant inert medium. Upon interaction with ionizing radiation, the droplets evaporate, generating visible bubbles. Bubble expansion associated with the boiling of the droplets is accompanied by pressure pulses in both the sonic and ultrasonic frequency range. In this work, we analyzed the signal generated by bubble evaporation in the frequency and time domain. We used octafluoropropane (R-218) based emulsions, sensitive to both photons and neutrons. The frequency content of the detected pulses appears to extend well into the hundreds of kHz, beyond the range used in commercial devices to count bubbles as they are formed (typically 1–10 kHz). Kilohertz components characterize the early part of the waveforms, potentially containing information about the energetics of the explosive bubble initial growth phase. The power spectral density of the acoustic signal produced by neutron-induced evaporation shows a characteristic frequency pattern in the 200–400 kHz range, which is not observed when bubbles evaporate upon gamma ray-induced irradiation. For practical applications, detection of ultrasonic pulses associated with the boiling of the superheated drops can be exploited as a fast readout method, negligibly affected by mechanical ambient noise.

Measures of maximum magnetic field in 3 GHz radio frequency superconducting cavities; Mesures du gradient accelerateur maximum dans des cavites supraconductrices en regime impulsionnel a 3 GHz

Energy Technology Data Exchange (ETDEWEB)

Thomas, Catherine [Paris-11 Univ., 91 Orsay (France)

2000-01-19

Theoretical models have shown that the maximum magnetic field in radio frequency superconducting cavities is the superheating field H{sub sh}. For niobium, H{sub sh} is 25 - 30% higher than the thermodynamical H{sub c} field: H{sub sh} within (240 - 274) mT. However, the maximum magnetic field observed so far is in the range H{sub c,max} = 152 mT for the best 1.3 GHz Nb cavities. This field is lower than the critical field H{sub c1} above which the superconductor breaks up into divided normal and superconducting zones (H{sub c1}{<=}H{sub c}). Thermal instabilities are responsible for this low value. In order to reach H{sub sh} before thermal breakdown, high power short pulses are used. The cavity needs then to be strongly over-coupled. The dedicated test bed has been built from the collaboration between Istituto Nazionale di Fisica Nucleare (INFN) - Sezione di Genoa, and the Service d'Etudes et Realisation d'Accelerateurs (SERA) of Laboratoire de l'Accelerateur Lineaire (LAL). The maximum magnetic field, H{sub rf,max}, measurements on INFN cavities give lower results than the theoretical speculations and are in agreement with previous results. The superheating magnetic fields is linked to the magnetic penetration depth. This superconducting characteristic length can be used to determine the quality of niobium through the ratio between the resistivity measured at 300 K and 4.2 K in the normal conducting state (RRR). Results have been compared to previous ones and agree pretty well. They show that the RRR measured on cavities is superficial and lower than the RRR measured on samples which concerns the volume. (author)

Signatures of granular superconductivity and Josephson effects in macroscopic measurements: the case of new superconductors

Directory of Open Access Journals (Sweden)

S Senoussi

2006-09-01

Full Text Available   We report systematic investigations of the magnetic superconducting properties of the new superconducting materials (NS: New high temperature superconductors (HTS, Organic superconductors (OS, fullerenes, carbon nanotubes, MgB2 etc. We show that, contrary to conventional superconductors where the superconducting state can be coherent over several tenths of km, the macroscopic coherence range lc of the NS is often as short as 0.1 to 10 µm typically. As a consequence, the magnetic properties are dominated by granular-like effects as well as Josephson coupling between grains. Here, we concentrate on HTS ceramics and organic superconductors exclusively. In the first case we observe three distinct regimes: (i At very low field (H < 5 Oe to say all the grains are coupled via Josephson effect and lc can be considered as infinite. (2 At intermediate field (5 < H < 50 Oe, typically the grains are gradually decoupled by H and/or T. (iii At higher fields all the grains are decoupled and lc roughly coincides with the diameter of the metallurgical grains. The case of OS is more subtle and is connected with a kind of order-disorder transition that occurs in most of them. For instance, in this study, we exploit quenched disorder (after crossing such a transition in the -(BEDT-TTF2Cu[N(CN2]Br layered organic superconductor to get new insights on both the superconducting state (T £ 11.6 K and the glassy transition at Tg, by studying the superconducting properties as functions of annealing time and annealing temperature around the glassy transition. Our main result is that the data can be described by a percolation molecular cluster model in which the topology and the growth of the molecular clusters obey an Ising spin-glass-like model with Tg ≈ 80 K for the hydrogenated compound and Tg ≈ 55 K for the fully deuterated one.

The atomic-scale origins of grain boundary superconducting properties

International Nuclear Information System (INIS)

Pennycook, S.J.; Chisholm, M.F.; Buban, J.; Browning, N.D.; Prouteau, C.; Univ. of Illinois, Chicago, IL; Nellist, P.D.

1998-02-01

Due to the extremely short coherence lengths of the high-T c superconductors, defects such as grain boundaries are obvious barriers to the flow of supercurrent. Within a few months of the discovery of these materials, it was shown how the critical current dropped four orders of magnitude as the grain boundary misorientation increased from zero to 45 degree. Even today, there is no quantitative understanding of this behavior. A qualitative understanding is however possible through atomic resolution Z-contrast imaging on YBa 2 Cu 3 O 7-δ and SrTiO 3 bicrystal grain boundaries, combined with bond-valence-sum analysis. The Z-contrast image of a YBa 2 Cu 3 O 7-δ low angle grain boundary shows the same kind of reconstructed dislocation cores as seen in SrTiO 3 , containing reconstructions on both the Cu and Y/Ba sublattices. An image of an asymmetric 30 degree boundary in YBa 2 Cu 3 O 7-δ shows the same units and unit sequence as expected for SrTiO 3 . YBa 2 Cu 3 O 7-δ boundaries are wavy because of their non-equilibrium growth process, and therefore mostly asymmetric in nature, although small segments have the symmetric structure. It seems reasonable to assume that boundaries of other angles will also have similar structures in these two materials

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

Energy Technology Data Exchange (ETDEWEB)

Achatz, Philipp

2009-05-15

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n{sub c} for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers ({approx} 500 cm{sup -1}) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g{sub c}. The granularity also influences significantly the superconducting properties by introducing the superconducting gap {delta} in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

International Nuclear Information System (INIS)

Achatz, Philipp

2009-01-01

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n c for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers (∼ 500 cm -1 ) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g c . The granularity also influences significantly the superconducting properties by introducing the superconducting gap Δ in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the first time in aluminum

Superconductivity: a quasiclassical theory of multiple interface geometry

International Nuclear Information System (INIS)

Rameshwar, Rudra; Prashant, Sagar; Prasad, Jagdish

2005-01-01

In many cases of interests such as a multilayer mesoscopic structure or the grain boundaries network in high technologies, one deal with the situation where multiple interfaces should be treated simultaneously on equal footing. In this paper we have focused on theoretically concept, i.e. even an isolated interface poses certain difficulties. Since abrupt changes violate the quasiclassical condition, the standard theory of superconductivity in terms of the quasiclassical matrix Green function g R is invalid at interfaces. The interface is included via the boundary condition derived by Zaitsev a cubic matrix relation in superconductivity. (author)

Magnetic response of superconducting mesoscopic-size YBCO powder

Energy Technology Data Exchange (ETDEWEB)

Deimling, C.V. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)], E-mail: cesard@df.ufscar.br; Motta, M.; Lisboa-Filho, P.N. [Laboratorio de Materiais Supercondutores, Departamento de Fisica, Universidade Estadual Paulista, Bauru, SP Brazil (Brazil); Ortiz, W.A. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)

2008-07-15

In this work it is reported the magnetic behavior of submicron and mesoscopic-size superconducting YBCO powders, prepared by a modified polymeric precursors method. The grain size and microstructure were analyzed using scanning electron microscopy (SEM). Measurements of magnetization and AC-susceptibility as a function of temperature were performed with a quantum design SQUID magnetometer. Our results indicated significant differences on the magnetic propreties, in connection with the calcination temperature and the pressure used to pelletize the samples. This contribution is part of an effort to study vortex dynamics and magnetic properties of submicron and mesoscopic-size superconducting samples.

Numerical evaluation of electromagnetic force induced in high Tc superconductor with grain boundary

International Nuclear Information System (INIS)

Hashizume, Hidetoshi; Toda, Saburo; Maeda, Koutaro

1996-01-01

After high T c superconducting material was discovered, its superconducting characteristic has been improved so that its critical current density becomes comparable with that of metal alloy superconductors. Together with this progress of the high T c material, it is considered to apply the materials to generating levitation force in combination with permanent magnets. In this case, it becomes very important to evaluate quantitatively the electromagnetic force for designing of the devices. Some researches have used numerical analysis to evaluate the force, where the grain boundary was ignored or treated as nonconducting. In the real materials, however, some part of the screening current can pass through the grain boundary. In this paper, therefore, two dimensional electromagnetic analysis was performed with a new method to treat the grain boundaries, and its effect on the levitation force was discussed

Nonlinear dynamics of a vapor bubble expanding in a superheated region of finite size

Energy Technology Data Exchange (ETDEWEB)

Annenkova, E. A., E-mail: a-a-annenkova@yandex.ru [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Kreider, W. [Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105 (United States); Sapozhnikov, O. A. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105 (United States)

2015-10-28

Growth of a vapor bubble in a superheated liquid is studied theoretically. Contrary to the typical situation of boiling, when bubbles grow in a uniformly heated liquid, here the superheated region is considered in the form of a millimeter-sized spherical hot spot. An initial micron-sized bubble is positioned at the hot spot center and a theoretical model is developed that is capable of studying bubble growth caused by vapor pressure inside the bubble and corresponding hydrodynamic and thermal processes in the surrounding liquid. Such a situation is relevant to the dynamics of vapor cavities that are created in soft biological tissue in the focal region of a high-intensity focused ultrasound beam with a shocked pressure waveform. Such beams are used in the recently proposed treatment called boiling histotripsy. Knowing the typical behavior of vapor cavities during boiling histotripsy could help to optimize the therapeutic procedure.

Process and devices of detection of hard electromagnetic or particle radiations using a superconducting element

International Nuclear Information System (INIS)

Drukier, A.K.; Valette, Claude; Waysand, Georges.

1975-01-01

The invention relates to processes and systems for the detection of hard electromagnetic or particle radiations and the sensors fitted to these systems. 'Hard radiations' means those whose energy is greater than a variable threshold, depending on the applications, but always more than 5 keV. The use of these sensors and the associated systems can therefore be envisaged in radiography and also in emission gammagraphy in the biological, anatomic and medical fields. In these processes, in order to detect a photon or a radiation particle, use is made of the transition phenomenon of a homogeneous grain of superconducting material of the first kind, from the metastable superconducting state to the normal state, under the effect of a photoelectron ejected by the impact of the photon or of the particle on the grain of superconducting material [fr

An experimental investigation of the isochoric heat capacity of superheated steam and mixtures of superheated steam and hydrogen gas

International Nuclear Information System (INIS)

Nowak, E.S.; Chan, J.S.

1975-01-01

Measurements on the specific heat at constant volume of superheated steam and hydrogen gas mixtures at concentrations varying from 1.6 to 0.8 moles of water vapor per mole of hydrogen gas were made for temperatures ranging from 240 to 400 deg C. It was found that the experimental specific heat values of the mixtures are in good agreement with the ideal mixture values only near the saturation temperature of steam. The difference between the measured and the calculated ideal mixture values is a function of temperature, pressure and composition varying from about 11 to 24% at conditions far removed from the saturation temperature of steam. This indicates the heat of mixing is of significance in the steam-hydrogen system

AUTOMATIC CONTROL SYSTEM OF THE DRUM BOILER SUPERHEATED STEAM TEMPERATURE.

Directory of Open Access Journals (Sweden)

Juravliov A.A.

2006-04-01

Full Text Available The control system of the temperature of the superheated steam of the drum boiler is examined. Main features of the system are the PI-controller in the external control loop and introduction of the functional component of the error signal of the external control loop with the negative feedback of the error signal between the prescribed value of steam flowrate and the signal of the steam flowrate in the exit of the boiler in the internal control loop.

The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

International Nuclear Information System (INIS)

Zu, Z.J.; Chen, Y.L.

1988-01-01

Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper

Performance study of ejector cooling cycle at critical mode under superheated primary flow

International Nuclear Information System (INIS)

Tashtoush, Bourhan; Alshare, Aiman; Al-Rifai, Saja

2015-01-01

Highlights: • The ECC is modeled using EES Software and it is validated with published data. • Detailed analysis of the ECC with different refrigerants is conducted. • The constant pressure mixing is better than constant area mixing ejectors. • R134a is the selected refrigerant for the best cooling cycle performance. • The superheated primary flow at critical mode is achieved with EJ2 ejector used. - Abstract: In this work the performance of the ejector cooling cycle is investigated at critical mode, where, the effects of ejector geometry, refrigerant type, and operating condition are studied. The ejector cooling cycle is modeled with EES Software. The mass, momentum, and energy conservation principles are applied to the secondary and primary flows to investigate the performance of the ejector cooling cycle under superheated primary flow. The refrigerant R134 a is selected based on the merit of its environmental and performance characteristics. The primary working fluid in the refrigeration cycle is maintained at superheated conditions for optimal ejector performance. The solar generator temperature ranges are 80–100 °C. The operating temperature of evaporator range is 8–12 °C and the optimal condensation temperature is in the range of 28–40 °C. It is found that constant-pressure mixing ejector generates higher backpressure than constant-area mixing ejector for the same entrainment ratio and COP. The type of ejector is selected based on the performance criteria of the critical backpressure and choking condition of the primary flow, the so called EJ2 type ejector meets the criteria. The COP is found to be in the range of 0.59–0.67 at condenser backpressure of 24 bar due to higher critical condenser pressure and higher generator temperature

Structure and superconducting properties of Nb-Zr alloy films made by a high-rate sputtering

International Nuclear Information System (INIS)

Sekine, Hisashi; Inoue, Kiyoshi; Tachikawa, Kyoji

1978-01-01

Superconducting Nb-Zr alloy films have been prepared by a continuous high-rate sputtering on tantalum substrates. A deposition rate of 330 nm/min has been attained. The compositional profile in the Nb-Zr film is quite uniform and the film has nearly the same composition as that of the target. The films deposited in a pure argon atmosphere show a columnar structure grown perpendicular to the substrate. The grain size strongly depends on the substrate temperature. The phase transformations in the Nb-Zr film become more apparent and the structure becomes closer to the equilibrium state as the film is deposited in higher atmosphere pressures and/or at lower target voltages. The superconducting transition temperature T sub(c) of the films is about the same as that of bulk samples. The dependence of T sub(c) on the substrate temperature is explainable on the phase transformations in the film. Critical current density J sub(c) and its anisotropy is closely related to the grain structure of the film. Grain boundaries seem to act as the most predominant flux pinning centers in the films. Effects of oxygen in the sputtering atmosphere on the structure and superconducting properties of the Nb-Zr films have been also investigated. Oxygen significantly decreases the grain size of the film. Oxygen increases J sub(c) but decreases T sub(c) of the film. (auth.)

Boiling of superheated liquids near the spinodal: II Application

Science.gov (United States)

aus der Wiesche, S.; Rembe, C.; Hofer, E. P.

The general theory of boiling near the spinodal as critical phenomenon will be used on the nucleation process of explosive evaporating liquids. In experiments with thermal micro heater the occurrence of the critical opalescence can be demonstrated which is characteristic for phase transitions of second order. In case of water the experiments permit the determination of the gradient energy coefficient κ for nonuniform systems. The homogeneous nucleation rate for extremely superheated water at normal pressure is discussed. It is found that the explosive evaporation starts very closed to the spinodal and leads to spatial extended nuclei in contrast to the conventional nucleation mode.

Impact of radiation exposure on mechanical and superconducting properties of Bi-2212 superconductor ceramics

International Nuclear Information System (INIS)

Azlan Abdul Rahman; Nasri Abdul Hamid; Abdul Aziz Mohamed; Mohd Shahrul Nizam Abdullah; Samsul Isman; Hidayah Zainal

2013-01-01

Full-text: For practical applications of high-temperature superconductor ceramics, the compounds must be able to sustain extreme mechanical stress and external magnetic field. Bi-2212 superconductor is one of the existing superconductors that are commonly used in various applications. Improvement in the microstructure enhanced the connectivity of the adjacent grains within the superconducting grains, and as such improved the mechanical strength of the ceramics. The ability of the superconductor ceramics to sustain superconducting properties in external magnetic field is also required. The compounds must be able to maintain high transport critical current density (Jc) in magnetic field. Another potential application of superconductors is at the nuclear facilities. Thus, study on the impact of radiation exposure on the mechanical and superconducting properties is very important to gauge the viability of superconductor ceramics in such environment. In this study, the mechanical and superconducting properties between exposure and non-irradiated samples are compared. Characterization will be done by the temperature dependence on electrical resistance measurements, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and measurements of transport critical current (Jc) dependence on temperature in magnetic field. (author)

Development of microstructure and superconductivity of silver-clad Bi(2223) composite tapes in the process of heat treatment

International Nuclear Information System (INIS)

Guo, Y.C.; Liu, H.K.; Dou, S.X.

1994-01-01

A systematic study on the development of phase composition, microstructure and superconducting properties (critical temperature Tc and critical current density J c ) in silver-clad (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10 composite tapes during the process of heat treatment has been conducted using X-ray diffraction, scanning electron microscopy and electrical measurements. The correlation between the tape's high Tc phase purity, microstructure and superconducting properties at different heat treatment stages has been carefully analysed and explained. The results indicate that pure high Tc phase, high degree of grain alignment, high mass density and good connection between grains are all essential for superconducting tapes to carry a large current. With the optimized process parameters, a critical current density J c up to 32665 A cm -2 (corresponding critical current, 42.3 A) at 77 K and self-magnetic field for silver-clad (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10 superconducting composite tapes has been achieved. (orig.)

Thermally activated phase slippage in high-Tc grain-boundary Josephson junctions

International Nuclear Information System (INIS)

Gross, R.; Chaudhari, P.; Dimos, D.; Gupta, A.; Koren, G.

1990-01-01

The effect of thermally activated phase slippage (TAPS) in YBa 2 Cu 3 O 7 grain-boundary Josephson junctions has been studied. TAPS has been found to be responsible for the dc noise voltage superimposed on the dc Josephson current near the transition temperature. Because of the reduced Josephson coupling energy of the grain-boundary junctions, which is caused by a reduced superconducting order parameter at the grain-boundary interface, TAPS is present over a considerable temperature range. The implications of TAPS on the applicability of high-T c Josephson junctions are outlined

Beginning point of metal to insulator transition for Bi-2223 superconducting matrix doped with Eu nanoparticles

International Nuclear Information System (INIS)

Yildirim, G.

2013-01-01

Highlights: •Standard measurements such as bulk density, ρ-T, J ct , XRD, SEM and EDX examinations for characterization of the samples. •Role of Eu inclusions on the microstructural, electrical and superconducting properties of Bi-2223 phase. •Determination of metal to insulator transition due to Eu impurities in the Bi-2223 superconducting matrix. •From the Eu content level of x = 0.5 onwards, destruction of the superconducting phases. •Constant retrogression of the microstructural and superconducting properties with the Eu individuals. -- Abstract: This comprehensive study examines the change of the microstructural, electrical and superconducting properties of the Eu doped Bi 1.8 Pb 0.4 Eu x Sr 2 Ca 2.2 Cu 3.0 O y ceramic cuprates (with x ⩽ 0.7) produced by the conventional solid state reaction method at the constant annealing temperature of 840 °C for 24 h with the aid of the standard characterization measurements such as bulk density, dc resistivity (ρ-T), transport critical current density (J c ), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron dispersive X-ray (EDX) examinations. For the full characterization of the pure and Eu doped Bi-2223 samples, the degree of granularity (from the bulk density and porosity measurements); the room temperature resistivity, onset–offset critical transition temperature, variation of transition temperature, hole carrier concentration, spin-gap opening temperature and thermodynamic fluctuations (from the dc resistivity experiments); the texturing, crystal structure, crystallite size, phase purity and cell parameters (from the XRD investigations); the variation of the flux pinning centers and the boundary weak-links between the superconducting grains (from the critical current density values); the crystallinity, specimen surface morphology, grain connectivity between the superconducting grains and grain size distribution (from the SEM examinations), the elemental compositions and

Vapour phase motion in cryogenic systems containing superheated and subcooled liquids

Science.gov (United States)

Kirichenko, Yu. A.; Chernyakov, P. S.; Seregin, V. E.

The development of vent pipelines, and venting storage tanks for cryogenic liquids requires the knowledge of the law of motion as well as regularities of vapour content variation in the liquid and heat dissipation by the vapour phase. This is a theoretical study of the effect of superheating (subcooling) of the liquid, relative acceleration and reduced pressure upon the size and velocity of noninteracting vapour bubbles, moving in the liquid, and upon their resistance and heat transfer coefficients.

Prospects for SIMPLE 2000: a large-mass, low-background superheated droplet detector for WIMP searches

International Nuclear Information System (INIS)

Collar, J.I.; Girard, T.A.; Miley, H.S.; Waysand, G.

2000-01-01

The Superheated Instrument for Massive Particle searches (SIMPLE 2000) will consist of an array of 8-16 large active mass (approx. 15 g) superheated droplet detectors (SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make the use of SDDs an attractive approach for the detection of weakly interacting massive particles (WIMPs), namely their intrinsic insensitivity to minimally ionizing particles, high fluorine content, low cost and operation at near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from prototype SDDs for SIMPLE, as well as on the expected immediate increase in sensitivity of the programme, which aims at an exposure of > 25 kg day during 2000. The ability of modest-mass fluorine-rich detectors to investigate regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out. (author)

Prospects for SIMPLE 2000: a large-mass, low-background superheated droplet detector for WIMP searches

International Nuclear Information System (INIS)

Collar, J I; Puibasset, J; Girard, T A; Limagne, D; Miley, H S; Waysand, G

2000-01-01

The Superheated Instrument for Massive Particle searches (SIMPLE 2000) will consist of an array of 8-16 large active mass (≅15 g) superheated droplet detectors (SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make the use of SDDs an attractive approach for the detection of weakly interacting massive particles (WIMPs), namely their intrinsic insensitivity to minimally ionizing particles, high fluorine content, low cost and operation at near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from prototype SDDs for SIMPLE, as well as on the expected immediate increase in sensitivity of the programme, which aims at an exposure of > 25 kg day during 2000. The ability of modest-mass fluorine-rich detectors to investigate regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out

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.

The inhomogeneities of (Pb,Bi)2223 superconducting tapes and their detection

International Nuclear Information System (INIS)

Leeuwen, S. van

1999-05-01

This thesis consists of two parts: first, the inhomogeneities that were observed in high temperature superconducting (Pb,Bi)2223 tapes were studied followed by the design of two rigs which were built to detect them. These investigations concentrated on (Pb,Bi)2223 phase high temperature superconducting tapes. Superconductors and their applications were briefly evaluated. It was found that high temperature superconductors have unique properties which cannot be duplicated by their counterparts. However, it was noted that there are significant improvements to be made before they can be commercially viable. An investigation was carried out into the variation of core density within cross sections and along lengths of (Pb,Bi)2223 tapes during fabrication. It was observed that rolling and thermal treatment brought about a non-uniform core density in both these aspects of tile tape. This was followed by an investigation into the effect of core density on the formation of the (Pb,Bi)2223 phase. It was shown that a high core density formed the (Pb,Bi)2223 phase at a slower rate than a lower core density under the thermal treatment. A high core density and a slow heating rate produced smaller 2212 grains at the end of the incubation period. Smaller 2212 grains were thought to be linked to the faster formation of the (Pb,B1)2223 phase. The highest Jc was from a high core density tape which had the smaller 2212 grains at the end of incubation period. Smaller 2212 grains were thought to aid a more homogeneous conversion to the (Pb,Bi)2223 phase. Alloy-sheathed (Pb,Bi)2223 superconducting tapes were produced in order to fabricate a more homogeneous core density. It was found that the alloy sheath (with an addition of 15% wt Ag in the precursor powder) changed the characteristics of the core in several ways: the formation of the (Pb,Bi)2223 phase was homogeneous across the thickness of the core, a smaller 2212 grain size was formed at the end of the incubation period and a higher

Boiling of superheated liquids near the spinodal: II. Application

Energy Technology Data Exchange (ETDEWEB)

Aus der Wiesche, S.; Rembe, C.; Hofer, E.P. [Ulm Univ. (Germany). Dept. of Measurement, Control and Microtechnology

1999-07-01

The general theory of boiling near the spinodal as critical phenomenon will be used on the nucleation process of explosive evaporating liquids. In experiments with thermal micro heater the occurrence of the critical opalescence can be demonstrated which is characteristic for phase transitions of second order. In case of water the experiments permit the determination of the gradient energy coefficient {kappa} for nonuniform systems. The homogeneous nucleation rate for extremely superheated water at normal pressure is discussed. It is found that the explosive evaporation starts very closed to the spinodal and leads to spatial extended nuclei in contrast to the conventional nucleation mode. (orig.) With 5 figs., 16 refs.

Prospects for SIMPLE 2000 A large-mass, low-background Superheated Droplet Detector for WIMP searches

CERN Document Server

Collar, J I; Girard, T A; Limagne, D; Miley, H S; Waysand, G

2000-01-01

SIMPLE 2000 ({\\underline S}uperheated {\\underline I}nstrument for {\\underline M}assive {\\underline P}artic{\\underline {LE}} searches) will consist of an array of eight to sixteen large active mass ($\\sim15$ g) Superheated Droplet Detectors(SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make of SDDs an attractive approach for the detection of Weakly Interacting Massive Particles (WIMPs), namely their intrinsic insensitivity to minimum ionizing particles, high fluorine content, low cost and operation near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from SIMPLE prototype SDDs, as well as on the expected immediate increase in sensitivity of the program, which aims at an exposure of $>$25 kg-day during the year 2000. The ability of modest-mass fluorine-rich detectors to explore regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out.

Machine Learning Method Applied in Readout System of Superheated Droplet Detector

Science.gov (United States)

Liu, Yi; Sullivan, Clair Julia; d'Errico, Francesco

2017-07-01

Direct readability is one advantage of superheated droplet detectors in neutron dosimetry. Utilizing such a distinct characteristic, an imaging readout system analyzes image of the detector for neutron dose readout. To improve the accuracy and precision of algorithms in the imaging readout system, machine learning algorithms were developed. Deep learning neural network and support vector machine algorithms are applied and compared with generally used Hough transform and curvature analysis methods. The machine learning methods showed a much higher accuracy and better precision in recognizing circular gas bubbles.

Characterisation of nano-grains in MgB2 superconductors by transmission Kikuchi diffraction

International Nuclear Information System (INIS)

Wong, D.C.K.; Yeoh, W.K.; Trimby, P.W.; De Silva, K.S.B.; Bao, P.; Li, W.X.; Xu, X.; Dou, S.X.; Ringer, S.P.; Zheng, R.K.

2015-01-01

We report the first application of the emerging transmission Kikuchi diffraction technique in the scanning electron microscope to investigate nano-grain structures in polycrystalline MgB 2 superconductors. Two sintering conditions were considered, and the resulting differences in superconducting properties are correlated to differences in grain structure. A brief comparison to X-ray diffraction results is presented and discussed. This work focusses more on the application of this technique to reveal grain structure, rather than on the detailed differences between the two sintering temperatures

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.

Formation of gas bubbles in gas superheated water

International Nuclear Information System (INIS)

Finkelstein, Y.

1984-05-01

The phenomenon of bubbles formation in supersaturated solutions of gases in water is a transport process, the final result of which is a separation of phases. In spite of its widespread appearance in industry and in nature, no model exists that can explain it and predict the degree of supersaturation which a gas-water solution can tolerate before bubbles are formed. The objective of this study was to fill this gap, and indeed, an extensive experimental work was carried out, a model was established and simple but accurate means were developed for predicting the tolerable degree of supersaturation of gas-water solutions. The model is also capable of predicting quite accurately the activation phenomenon in water. Superheating and supercooling phenomena were also examined in the light of the new model. (author)

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...

Study on niobium carbide dispersed superconducting tapes

Energy Technology Data Exchange (ETDEWEB)

Wada, H; Tachikawa, K [National Research Inst. for Metals, Tokyo (Japan); Oh' asa, M [Science Univ. of Tokyo (Japan)

1977-11-01

Niobium carbide (NbC) dispersed superconducting tapes have been fabricated by two metallurgical processes. In the first process, Ni-Nb-C alloys are directly arc melted and hot worked in air and the NbC phase is distributed in the form of fine discrete particles. In the second process, Ni-Nb and Ni-Nb-Cu alloys are arc melted, hot worked and subjected to solid-state carburization. NbC then precipitates along the grain boundaries, forming a network. The highest superconducting transition temperature attained is about 11 K. Taken together with the lattice parameter measurement, this indicates that NbC with a nearly perfect NaCl structure is formed in both processes. Measured values of the upper critical field, the critical current density and the volume fraction of the NbC phase are also discussed.

Design of H2/H∞ RMPC for Boiler Superheated Steam Temperature Based on Memoryless Feedback Multistep Strategy

Directory of Open Access Journals (Sweden)

Pu Han

2017-01-01

Full Text Available The collection of superheated steam temperature models of a thermal power plant under different loads can be approximated to “multimodel” linear uncertain systems. After transformation, the tracking system was obtained from “multimodel” linear uncertain systems. For this tracking uncertain system, a mixed H2/H∞ robust model predictive control (HRMPC based on a memoryless feedback multistep strategy is proposed. A multistep control strategy combines the advantages of predictive control rolling optimization with memoryless feedback control thoughts. It could effectively decrease the controller optimization parameter and ensure closed-loop system stability, and, at the same time, it also achieved acceptable control performance. Successful application to the superheated steam temperature system of a 300 MW thermal power plant verified the study of the HRMPC-P cascade controller design scheme in terms of feasibility and effectiveness.

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

Determination of the inter- and intra-granular critical currents in superconducting YBa2Cu3O7 welds

International Nuclear Information System (INIS)

Bozzo, B; Iliescu, S; Bartolome, E; Palau, A; Granados, X; Puig, T; Obradors, X; Amoros, J; Carrera, M

2005-01-01

A method for determining simultaneously the inter- and intra-grain critical currents has been developed in welded YBa 2 Cu 3 O 7 (YBCO) ceramics by solving the Inverse Problem for local maps of the magnetic field in the remanent state. From that current distribution, the current density flowing through the superconducting weld as well as the current density circulating inside the grains can be deduced. The method is discussed and it is applied to several examples of YBCO/Ag/YBCO welds. The results obtained show that it is possible to obtain superconducting joints with a quality at the same level as that of the starting material

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...

Structural and superconducting properties of as-cast Nb3Al

International Nuclear Information System (INIS)

Mondal, Puspen; Manekar, Meghmalhar; Roy, S.B.; Kumar, Ravi; Ganguli, Tapas

2007-01-01

We present the results of x-ray diffraction and magnetization measurements on the as-cast compound Nb 3 Al. X-ray diffraction shows the presence of the Al 5 Nb 3 Al phase along with a bcc Nb-Al solid solution. The average grain size of Nb 3 Al estimated from the line broadening is about 35 nm. Magnetization measurements show a superconducting transition temperature of about 16.8 K which is amongst the highest known T c for the as-cast sample. In the superconducting state, the sample shows interesting thermo-magnetic history effects in the temperature and field variation of magnetization. (author)

Advantageous grain boundaries in iron pnictide superconductors

Science.gov (United States)

Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

2011-01-01

High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries—the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (>1 MA cm−2) and nearly constant up to a critical angle θc of ∼9°, which is substantially larger than the θc of ∼5° for YBa2Cu3O7–δ. Even at θGB>θc, the decay of JcBGB was much slower than that of YBa2Cu3O7–δ. PMID:21811238

Investigation of local losses as a function of material removal in a large-grain superconducting niobium cavity

International Nuclear Information System (INIS)

Gianluigi Ciovati; Peter Kneisel

2006-01-01

The performance of a superconducting radio-frequency (RF) cavity made of residual resistivity ratio (RRR) > 200 large-grain niobium has been investigated as a function of material removal, between 70 and 240 ?m, by buffered chemical polishing (BCP). Temperature maps of the cavity surface at 1.7 and 2.0 K were taken for each step of chemical etching and revealed localized losses (''hot-spots''), which contribute to the degradation of the cavity quality factor as a function of the RF surface field. It was found that the number of ''hot-spots'' decreased for larger material removal. Interestingly, the losses at the ''hot-spots'' at different locations evolved differently for successive material removal. The cavity achieved peak surface magnetic fields of about of 130 mT and was limited mostly by thermal quench. By measuring the temperature dependence of the surface resistance (Rs) at low field between 4.2 K and 1.7 K, the variation of material parameters such as the energy gap at 0 K, the residual resistance and the mean free path as a function of material removal could also be investigated. This contribution presents the results of the RF tests along with the temperature maps and the analysis of the losses caused by the ''hot-spots''

Superconducting thin films

International Nuclear Information System (INIS)

Hebard, A.F.; Vandenberg, J.M.

1982-01-01

This invention relates to granular metal and metal oxide superconducting films formed by ion beam sputter deposition. Illustratively, the films comprise irregularly shaped, randomly oriented, small lead grains interspersed in an insulating lead oxide matrix. The films are hillock-resistant when subjected to thermal cycling and exhibit unusual josephson-type switching characteristics. Depending on the oxygen content, a film may behave in a manner similar to that of a plurality of series connected josephson junctions, or the film may have a voltage difference in a direction parallel to a major surface of the film that is capable of being switched from zero voltage difference to a finite voltage difference in response to a current larger than the critical current

An investigation into preparation of silver sheathed superconducting wires with a high critical temperature

International Nuclear Information System (INIS)

Chaffron, Laurent

1992-01-01

We have shown that the critical current density of YBaCuO superconducting wires prepared using 'powder in tube' method is limited by the following principal factors: - cracks and porosity arising from the shrinkage of the powder during sintering, - irregularities in the wire section, - presence of secondary phases in the phase diagram of the three oxides, - incomplete re-oxidation at the centre of the wire, - insufficient, or complete lack of, texture in the wire, - presence of amorphous, non superconducting phase across the grains that blocks grain boundary migration. We have reduced the deleterious effects due to the first four factors by modifying prior nature of the powder, by reinforcing the sheath and by modifying the thermal treatments. We also used creep sintering to produce a strong texture; however, our study shows that texture, though necessary, is not a sufficient condition for a high current. This is because the latter is limited by the presence of the amorphous phase at too many grain boundaries. Finally, we have obtained wires in which grain boundaries are clean and which have very high critical currents by melting the wire in a thermal gradient and by passing it through the gradient very slowly. Such a technique, however, is too slow for producing superconductors. (author) [fr

Influences of superheated steam roasting on changes in sugar, amino acid and flavour active components of cocoa bean (Theobroma cacao).

Science.gov (United States)

Zzaman, Wahidu; Bhat, Rajeev; Yang, Tajul Aris; Easa, Azhar Mat

2017-10-01

Roasting is one of the important unit operations in the cocoa-based industries in order to develop unique flavour in products. Cocoa beans were subjected to roasting at different temperatures and times using superheated steam. The influence of roasting temperature (150-250°C) and time (10-50 min) on sugars, free amino acids and volatile flavouring compounds were investigated. The concentration of total reducing sugars was reduced by up to 64.61, 77.22 and 82.52% with increased roasting temperature at 150, 200 and 250°C for 50 min, respectively. The hydrophobic amino acids were reduced up to 29.21, 36.41 and 48.87% with increased roasting temperature at 150, 200 and 250°C for 50 min, respectively. A number of pyrazines, esters, aldehydes, alcohols, ketones, carboxyl acids and hydrocarbons were detected in all the samples at different concentration range. Formation of the most flavour active compounds, pyrazines, were the highest concentration (2.96 mg kg -1 ) at 200°C for 10 min. The superheated steam roasting method achieves the optimum roasting condition within a short duration Therefore, the quality of cocoa beans can be improved using superheated steam during the roasting process. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

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.

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).

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

Biaxial magnetic grain alignment

International Nuclear Information System (INIS)

Staines, M.; Genoud, J.-Y.; Mawdsley, A.; Manojlovic, V.

2000-01-01

Full text: We describe a dynamic magnetic grain alignment technique which can be used to produce YBCO thick films with a high degree of biaxial texture. The technique is, however, generally applicable to preparing ceramics or composite materials from granular materials with orthorhombic or lower crystal symmetry and is therefore not restricted to superconducting applications. Because magnetic alignment is a bulk effect, textured substrates are not required, unlike epitaxial coated tape processes such as RABiTS. We have used the technique to produce thick films of Y-247 on untextured silver substrates. After processing to Y-123 the films show a clear enhancement of critical current density relative to identically prepared untextured or uniaxially textured samples. We describe procedures for preparing materials using magnetic biaxial grain alignment with the emphasis on alignment in epoxy, which can give extremely high texture. X-ray rocking curves with FWHM of as little as 1-2 degrees have been measured

Kinetic studies of sea mango (Cerbera odollam) oil for biodiesel production via injection of superheated methanol vapour technology

International Nuclear Information System (INIS)

Ang, Gaik Tin; Tan, Kok Tat; Lee, Keat Teong; Mohamed, Abdul Rahman

2015-01-01

Highlights: • Sea mango oil with high FFA was directly used to produce biodiesel. • Non-catalytic superheated methanol transesterification system is developed. • High content of FAME can be obtained. • Kinetic modelling based on reaction mechanism is proposed and verified. • Kinetic study for reversible transesterification and esterification reactions. - Abstract: In this study, sea mango (Cerbera odollam) oil which is rich in free fatty acid was utilised as the feedstock in one-step superheated methanol vapour (SMV) transesterification reaction without going through pre-treatment step. SMV transesterification reaction was initiated by injecting superheated methanol vapour into sea mango oil phase. Effect of methanol flow rate at the range of 1–4 mL/min as well as effect of reaction temperatures at the range of 260–290 °C was studied based on FAME production rates at constant initial oil volume of 100 mL. Kinetic modelling of semi-batch system, incorporating second-order of three-stepwise reversible transesterification of triglycerides (TG) and second order of reversible esterification of free fatty acid (FFA) were verified simultaneously using ordinary differential equation (ODE45) solver. It shows that transesterification reaction of TG and esterification of FFA would occur simultaneously. The high activation energy of 50 kJ/mol and low reaction rate constant of 1.62 × 10"−"4 dm"3/mol min verified that the reaction of TG to become diglycerides (DG) as the rate limiting step in this semi-batch SMV system.

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...

Thermally activated phase slippage in high- T sub c grain-boundary Josephson junctions

Energy Technology Data Exchange (ETDEWEB)

Gross, R.; Chaudhari, P.; Dimos, D.; Gupta, A.; Koren, G. (IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (USA))

1990-01-08

The effect of thermally activated phase slippage (TAPS) in YBa{sub 2}Cu{sub 3}O{sub 7} grain-boundary Josephson junctions has been studied. TAPS has been found to be responsible for the dc noise voltage superimposed on the dc Josephson current near the transition temperature. Because of the reduced Josephson coupling energy of the grain-boundary junctions, which is caused by a reduced superconducting order parameter at the grain-boundary interface, TAPS is present over a considerable temperature range. The implications of TAPS on the applicability of high-{ital T}{sub {ital c}} Josephson junctions are outlined.

Thermal Hydraulic Design and Analysis of a Water-Cooled Ceramic Breeder Blanket with Superheated Steam for CFETR

Science.gov (United States)

Cheng, Xiaoman; Ma, Xuebin; Jiang, Kecheng; Chen, Lei; Huang, Kai; Liu, Songlin

2015-09-01

The water-cooled ceramic breeder blanket (WCCB) is one of the blanket candidates for China fusion engineering test reactor (CFETR). In order to improve power generation efficiency and tritium breeding ratio, WCCB with superheated steam is under development. The thermal-hydraulic design is the key to achieve the purpose of safe heat removal and efficient power generation under normal and partial loading operation conditions. In this paper, the coolant flow scheme was designed and one self-developed analytical program was developed, based on a theoretical heat transfer model and empirical correlations. Employing this program, the design and analysis of related thermal-hydraulic parameters were performed under different fusion power conditions. The results indicated that the superheated steam water-cooled blanket is feasible. supported by the National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)

The initial phase of sudden releases of superheated liquid

International Nuclear Information System (INIS)

Schmidli, J.

1994-04-01

The catastrophic failure of a pressure vessel containing a liquefied substance, leading to an instantaneous release of its whole contents is considered as one of the major technological hazards. Due to the rapid depressurization caused by vessel failure, the fluid becomes superheated and unstable. Part of the fluid will evaporate using its internal energy and the two-phase mixture forming will be accelerated. This flashing process can be very violent, as experiments and incidents actually happened have shown. In the past, a number of dispersion models were developed to predict the history of an instantaneous release. In most of these models the source term is considered to be a gas volume at rest and not a rapidly expanding aerosol, as could be observed. Furthermore, it is usually assumed that all of the remaining fluid is entrained into the expanding cloud and nothing is deposited on the ground to form a pool. This work concentrates on the initial phase of the sudden release of superheated liquids with the aim to gain a better understanding of the flashing process and of the physical mechanisms involved, leading to a reliable prediction of the source term. Therefore, more than 400 experiments with propane, butane, refrigerant 12 and 114 were conducted. The experiments were initiated by shattering spherical glass flasks of different sizes. The main parameters varied were the liquid superheat and the filling level of the vessel. Using high-speed video and movie recordings and very fast responding measurement devices, it was possible to study the initial phase of such releases during which gravity plays no role. For sufficiently large released internal energy, the initial evolution of the release was always spherical with a constant radial expansion velocity during he first milliseconds until instabilities appeared at the surface of the droplet/vapor cloud that was formed. For all the experimental conditions, the fraction of the initial liquid falling on the ground

Fractional Josephson vortices at YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries

OpenAIRE

Mints, R. G.; Papiashvili, Ilya

2001-01-01

We report numerical simulations of magnetic flux patterns in asymmetric 45$^{\\circ}$ [001]-tilt grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.

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

Low-temperature mechanical properties of superconducting radio frequency cavity materials

Science.gov (United States)

Byun, Thak Sang; Kim, Sang-Ho; Mammosser, John

2009-08-01

Low-temperature mechanical behaviors have been investigated for the constituent materials of superconducting radio frequency cavities. Test materials consist of small grain Nb, single crystal Nb, large grain Nb (bicrystal), Ti45Nb-Nb weld joint (e-beam welded), and Ti-316L bimetal joint (explosion welded). The strength of all test metals displayed strong temperature dependence and the Ti-316L bimetal showed the highest strength and lowest ductility among the test materials. The fracture toughness of the small grain Nb metals decreased with decreasing test temperature and reached the lower shelf values (30-40 MPa √m) at or above 173 K. The Ti45Nb base and Ti45Nb-Nb weld metals showed much higher fracture toughness than the small grain Nb. An extrapolation and comparison with existing data showed that the fracture toughness of the small grain Nb metals at 4 K was expected to be similar to those at 173 and 77 K. The results from optical photography at a low magnification and fractography by a scanning electron microscope were consistent with corresponding mechanical properties.

Low-temperature mechanical properties of superconducting radio frequency cavity materials

Energy Technology Data Exchange (ETDEWEB)

Byun, Thak Sang [ORNL; Kim, Sang-Ho [ORNL; Mammosser, John [ORNL

2009-01-01

Low temperature mechanical behaviors have been investigated for the constituent materials of superconducting radio frequency cavities. Test materials consist of small grain Nb, single crystal Nb, large grain Nb (bicrystal), Ti45Nb-Nb weld joint (e-beam welded), and Ti-316L bimetal joint (explosion welded). The strength of all test metals displayed strong temperature dependence and the Ti-316L bimetal showed the highest strength and lowest ductility among the test materials. The fracture toughness of the small grain Nb metals decreased with decreasing test temperature and reached the lower shelf values (30 40 MPa m) at or above 173 K. The Ti45Nb base and Ti45Nb-Nb weld metals showed much higher fracture toughness than the small grain Nb. An extrapolation and comparison with existing data showed that the fracture toughness of the small grain Nb metals at 4 K was expected to be similar to those at 173 K and 77 K. The results from optical photography at a low magnification and fractography by a scanning electron microscope were consistent with corresponding mechanical properties.

A Method for Suppressing Superconductivity of Thin Films

Science.gov (United States)

Suppula, Tarmo; Pekola, Jukka; Kauppinen, Juha

2003-03-01

We have developed a method for suppressing superconductivity of thin films. Thin stripes of cobalt grown by e-gun evaporation and patterned by e-beam lithography were placed in the vicinity of aluminium thin film structures. The cobalt stripes were magnetized at 4.2 K with a superconducting coil and the remanence suppressed superconductivity of the Al stripe at temperatures down to 50 mK at least. The magnetization remained in thermal cycling and in a longer storage at room temperature. Motivation for this work is the Coulomb Blockade Thermometer(CBT)^1 which has to be in a normal state to operate. The CBT sensor contains aluminium which is superconducting at temperatures below 1.4 K. An external magnetic field is not always available or acceptable in cryostats. A small grain of permanent magnet mounted to the sensor is another solution, but suspicious if the sensor is put in strong magnetic fields or if "zero field" environment is required. We have shown that suitably patterned and magnetized Co stripes in the vicinity of tunnel junctions of the CBT can solve this problem. The amount of magnetic material in the sensor, as well as the stray field, is very small. This technique may be useful in other low temperature thin film devices also. 1) Product of Nanoway Ltd.

Investigations on the propagation of free surface boiling in a vertical superheated liquid column

International Nuclear Information System (INIS)

Das, P.K.; Bhat, G.S.; Arakeri, V.H.

1987-01-01

Some experimental studies on boiling propagation in a suddenly depressurized superheated vertical liquid column are reported. The propagation velocity of this phase change has been measured using an optical method. This velocity is strongly dependent on liquid superheat, liquid purity and test section size. The measured velocities of less than 5 m s -1 are significantly lower than the sonic velocity. Present observations suggest that the dominant mechanism for boiling propagation is convection. (author)

Investigations on the propagation of free surface boiling in a vertical superheated liquid column

Energy Technology Data Exchange (ETDEWEB)

Das, P.K.; Bhat, G.S.; Arakeri, V.H.

1987-04-01

Some experimental studies on boiling propagation in a suddenly depressurized superheated vertical liquid column are reported. The propagation velocity of this phase change has been measured using an optical method. This velocity is strongly dependent on liquid superheat, liquid purity and test section size. The measured velocities of less than 5 m s/sup -1/ are significantly lower than the sonic velocity. Present observations suggest that the dominant mechanism for boiling propagation is convection.

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)

Grain size dependence of the critical current density in YBa2Cu3Ox superconductors

International Nuclear Information System (INIS)

Kuwabara, M.; Shimooka, H.

1989-01-01

The grain size dependence of the critical current density in bulk single-phase YBa 2 Cu 3 O x ceramics was investigated. The grain size of the materials was changed to range approximately from 1.0 to 25 μm by changing the conditions of power processing and sintering, associated with an increase in the sintered density of the materials with increasing grain size. The critical current density has been found to exhibit a significant grain size dependence, changing from 880 A/cm 2 to a value of 100 A/cm 2 with a small increase in the average grain size from 1.2 to 2.0 μm. This seems to provide information about the nature of the weak link between superconducting grains which might govern the critical current density of the materials

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

Nuclear power plant and apparatus for superheating steam

International Nuclear Information System (INIS)

Schluderberg, D.C.

1983-01-01

The invention consists of an apparatus for superheating steam, the apparatus comprising a horizontally disposed generally cylindrical elongate shell, inlet means in the shell for receiving steam, outlet means in the shell for discharching the steam, and a bundle of inclined tubes positioned in the flow path of the steam, each of the tubes having a length which is less than the diameter of the shell and opening into and extending in an upward direction from an outlet header to an inlet header, the inlet header beeing connected to a source of vapor, and the outlet header beeing connected to a condensate drain, characterised in that the test bundle comprises two banks of the tubes, the angle at which each of the tubes of one of the banks extends relative to a vertical longitudinal centerplane, the tubes of one of the banks terminate at and open into the inlet header, and the tubes of the other banks terminate at an open into another inlet header

An acoustical bubble counter for superheated drop detectors

International Nuclear Information System (INIS)

Taylor, C.; Montvila, D.; Flynn, D.; Brennan, C.; D'Errico, F.

2006-01-01

A new bubble counter has been developed based on the well-established approach of detecting vaporization events acoustically in superheated drop detectors (SDDs). This counter is called the Framework Scientific ABC 1260, and it represents a major improvement over prior versions of this technology. By utilizing advanced acoustic pattern recognition software, the bubble formation event can be differentiated from ambient background noise, as well as from other acoustic signatures. Additional structural design enhancements include a relocation of the electronic components to the bottom of the device; thus allowing for greater stability, easier access to vial SDDs without exposure to system electronics. Upgrades in the electronics permit an increase in the speed of bubble detection by almost 50%, compared with earlier versions of the counters. By positioning the vial on top of the device, temperature and sound insulation can be accommodated for extreme environments. Lead shells can also be utilized for an enhanced response to high-energy neutrons. (authors)

An acoustical bubble counter for superheated drop detectors.

Science.gov (United States)

Taylor, Chris; Montvila, Darius; Flynn, David; Brennan, Christopher; d'Errico, Francesco

2006-01-01

A new bubble counter has been developed based on the well-established approach of detecting vaporization events acoustically in superheated drop detectors (SDDs). This counter is called the Framework Scientific ABC 1260, and it represents a major improvement over prior versions of this technology. By utilizing advanced acoustic pattern recognition software, the bubble formation event can be differentiated from ambient background noise, as well as from other acoustic signatures. Additional structural design enhancements include a relocation of the electronic components to the bottom of the device; thus allowing for greater stability, easier access to vial SDDs without exposure to system electronics. Upgrades in the electronics permit an increase in the speed of bubble detection by almost 50%, compared with earlier versions of the counters. By positioning the vial on top of the device, temperature and sound insulation can be accommodated for extreme environments. Lead shells can also be utilized for an enhanced response to high-energy neutrons.

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

The investigation of recrystallization developed in the largely undercooled Ni–3 at.% Sn alloy

International Nuclear Information System (INIS)

Chen, Q.; Chen, Z.; Liu, F.; Cui, R.X.; Liang, T.

2015-01-01

Highlights: • The grain refinement occurred at ΔT ⩾ 230 K. • Plastic deformation and recrystallization led to grain refinement. • Grain refinement was evidenced directly by TEM. • Misorientation and different plane spacing were detected by high-resolution TEM. - Abstract: Using the molten glass purification combined with the cycle superheating methods, a refined grain was achieved in undercooled Ni–3 at.% Sn alloy. The characteristics of microstructures and substructures of the refined grain were investigated by the classical nucleation theory, the dimensionless superheating model and the stress accumulation model. The grain refinement occurring inevitably at high undercooling (ΔT) was ascribed to the plastic deformation of dendrites and subsequent recrystallization, which were evidenced by the transmission electron microscopy (TEM) (e.g. different types of dislocations, defects and sub-grain boundaries) and high-resolution TEM (e.g. misorientation and different plane spacings)

Neutron skyshine measurement at a K1200 superconducting heavy ion cyclotron using bubble dosimeters

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, B. [Safety Div., Australian Nuclear Science and Technology Organisation, Menai (Australia); Ronningen, R.M. [Michigan State Univ., National Superconducting Cyclotron Lab., East Lansing, MI (United States); Rossi, P. [Michigan State Univ., Office of Radiation, Chemical and Biological Safety, East Lansing, MI (United States)

1999-07-01

Understanding the characteristics of the neutron skyshine radiation is necessary for an accurate assessment of the environmental dose in the vicinity of the containment of a high-energy particle accelerator. At the National Superconducting Cyclotron Laboratory (NSCL), neutron skyshine was measured, using beams of 140 MeV/nucleon {sup 4}He and 80 MeV/nucleon {sup 22}Ne ions from the K1200 superconducting cyclotron. After passing through a radioactive-beam production target, the ion beam stopped in a solid aluminium stopping bar inside of a dipole magnet, resulting in the production of high energy fragmentation as well as evaporation neutrons in the NSCL Analysis Hall. The neutron dose equivalent and energy spectrum at the 1.37 m thick concrete roof of the Analysis Hall, directly above the aluminium target bar (reference point), were estimated, using a spherical 'rem-counter' and a set of seven Bonner-spheres, respectively. The skyshine dose, from neutrons transmitted through 21.5-cm local iron 'shielding' of the dipole magnet and the concrete roof, were evaluated using superheated bubble dosimeters at 50 m, 75 m, 100 m and 115 m from the reference point. The neutron doses beyond the extremity of the NSCL facility were extrapolated from the results of this investigation and were used to predict the exposure to members of the public by considering the operation schedule of the K1200 cyclotron. (authors)

First Dark Matter Limits from a Large-Mass, Low-Background Superheated Droplet Detector

CERN Document Server

Collar, J.I.; Girard, T.A.; Limagne, D.; Miley, H.S.; Waysand, G.

2000-01-01

We report on the fabrication aspects and calibration of the first large active mass ($\\sim15$ g) modules of SIMPLE, a search for particle dark matter using Superheated Droplet Detectors (SDDs). While still limited by the statistical uncertainty of the small data sample on hand, the first weeks of operation in the new underground laboratory of Rustrel-Pays d'Apt already provide a sensitivity to axially-coupled Weakly Interacting Massive Particles (WIMPs) competitive with leading experiments, confirming SDDs as a convenient, low-cost alternative for WIMP detection.

Ideal metastability fields and field penetration in type-I and type-II superconducting InBi single spheres

International Nuclear Information System (INIS)

Pettersen, G.; Parr, H.

1979-01-01

In a continuation of earlier work on the InBi alloys system, we have studied the superconducting properties of small, single spheres of InBi 0.80, 1.24, 1.70, 2.15, and 2.65 at.% Bi. The transition temperatures are 3.538, 3.659, 3.796, 3.908, and 4.044 +- 0.008 K. Assuming the penetration depth lambda to be proportional to y = 1(1-t 4 )/sup 1/2/, we determine lambda/sub o/ = dlambda/dy to be 810, 950, 1065, undetermined, and 1720 A +- 3%, respectively. The field dependence of lambda was studied up to the ideal superheating field H/sub sh/. We find lambda (H/sub sh/)/lambda (H = 0) = 1.53, 1.52, 1.42, undetermined, and 1.41 +- 0.05, respectively. Thus the relative increase in lambda close to H/sub sh/ is roughly independent of composition. These are the first measurements of lambda (H) in ''strong'' fields for type-II superconductors. The Ginzburg-Landau parameter kappa was determined from H/sub c/3. We find kappa/sub c/3(t = ) = 0.454, 0.636, 0.835, 0.984, and 1.22. The knowledge of H/sub c/ limits the accuracy to 2--5%. Ideal superheating was observed both in the type-I and type-II region. At t = 1, we find H/sub sh//H/sub c/ = 1.80, 1.48, 1.28, 1.17, and 1.13 +- 3--8%. This roughly agrees with numerical calculations of H/sub sh/(kappa). Thus, ideal superheating of the Meissner state to well above H/sub c/ is firmly established even for type-II superconductors. The results for H/sub sh/ are in good agreement with numerical calculations from Ginzburg-Landau theory. Assuming these theoretical results to hold, kappa (t = 1) can be calculated self-consistently from H/sub c/3 and H/sub sh/ for all metals investigated by the single-sphere method, giving values considered to be more accurate than any other available. Finally, we have obtained qualitative and quantitative results on the intermediate and mixed states in our spheres

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

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

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

Numerical Study of Single Bubble Growth on and Departure from a Horizontal Superheated Wall by Three-dimensional Lattice Boltzmann Method

Science.gov (United States)

Feng, Yuan; Li, Hui-Xiong; Guo, Kai-Kai; Zhao, Jian-Fu; Wang, Tai

2018-05-01

A three-dimensional hybrid lattice Boltzmann method was used to simulate the progress of a single bubble's growth and departure from a horizontal superheated wall. The evolutionary process of the bubble shapes and also the temperature fields during pool nucleate boiling were obtained and the influence of the gravitational acceleration on the bubble departure diameter (BDD), the bubble release frequency (BRF) and the heat flux on the superheated wall was analyzed. The simulation results obtained by the present three-dimensional numerical studies demonstrate that the BDD is proportional to g^{-0.301}, the BRF is proportional to g^{-0.58}, and the averaged wall heat flux is proportional to g^{0.201}, where g is the gravitational acceleration. These results are in good agreement with the common-used experimental correlations, indicating the rationality of the present numerical model and results.

Mean-field approach to unconventional superconductivity

International Nuclear Information System (INIS)

Sacks, William; Mauger, Alain; Noat, Yves

2014-01-01

Highlights: • A model Hamiltonian for unconventional superconductivity (SC) is proposed. • The pseudogap (PG) state is described in terms of pair fluctuations. • SC coherence is restored by a new pair–pair interaction, which counteracts fluctuations. • Given the temperature dependence of the parameters, the SC to PG transition is examined. • The theory fits the ‘peak–dip–hump’ features of cuprate and pnictide excitation spectra. - Abstract: We propose a model that connects the quasiparticle spectral function of high-T c superconductors to the condensation energy. Given the evidence for pair correlations above T c , we consider a coarse-grain Hamiltonian of fluctuating pairs describing the incoherent pseudogap (PG) state, together with a novel pair–pair interaction term that restores long-range superconducting (SC) coherence below T c . A mean-field solution then leads to a self-consistent gap equation containing the new pair–pair coupling. The corresponding spectral function A(k,E) reveals the characteristic peak–dip–hump features of cuprates, now observed on iron pnictides (LiFeAs). The continuous transition from SC to PG states is discussed

Effects of Zn doping on crystal structure, Raman spectra and superconductivity of SmBa2Cu3O7−δ systems

International Nuclear Information System (INIS)

Xue, Renzhong; Dai, Haiyang; Chen, Zhenping; Li, Tao; Xue, Yuncai

2013-01-01

Highlights: ► Zn ions affect significantly the lattice parameter of the SmBa 2 Cu 3−x Zn x O 7−δ (SBCZO) ceramic. ► Raman spectra of SBCZO samples obviously change with increasing Zn doping content. ► The superconducting transition temperature decreases with increasing Zn content. ► Induced lattice disorder and local magnetic moment in CuO 2 planes are related to suppression of T c . -- Abstract: Polycrystalline SmBa 2 Cu 3−x Zn x O 7−δ (SBCZO) (x = 0.0–0.4) samples are prepared by the usual solid-state reaction technique. The effects of Zn doping on the structure, the grain morphology, Raman spectra and electronic transport properties of SBCZO systems have been investigated. The orthorhombic structure of the samples does not change remarkably. The samples become denser and grain boundary becomes unclear with the increase of Zn content. Raman spectra exhibit different features with increasing Zn content which shows that Zn ions act as strong scattering centers to the charge carriers in the CuO 2 planes, enhance the disorder of the CuO 2 planes and increase oxygen depletion in Cu-O chains. The measurements of the resistivity show that the superconducting transition temperature T c decreases rapidly and the superconducting transition width increases gradually with increasing Zn contents. Furthermore, the changes of the samples’ normal state resistivity from metallic to semi-conducting behavior show the increase of heterogeneities with increasing Zn content which causes inter-grain or intra-grain disorders. All the results suggest that lattice disorder in the CuO 2 planes, the oxygen content change in Cu-O chains and local weak superconductivity regions due to the substitution of Zn for Cu are related to the suppression of T c in the SBCZO systems

Superconducting and normal state properties of niobium-potasium chloride composites

International Nuclear Information System (INIS)

Boysel, R.M.

1981-01-01

The electrical resistivity, current-voltage characteristics, critical currents, and DC magnetic susceptibility of composites consisting of 50 μm grains of Nb randomly dispersed in a KCl medium were measured. Data were taken between 1.2K and 20K in magnetic fields from 0 to +- 5G. The resistivity and current-voltage characteristics were measured using a standard four-terminal AC technique with a voltage sensitivity of 1 to 2nV, and the magnetic susceptibility was measured using an rf SQUID magnetometer. We found that samples with rho/sub n/ 2 . For 0.1Ω-cm 10Ω-cm there was no superconducting transition. The susceptibility decreased slowly below the grain transition temperature T/sub infinity/ and even below T/sub c/ in samples which underwent resistive transitions. The shape of the resistive transitions and the kink structure in the I-V's require a phase coherent transition model to adequately describe them. However, the poor fit of the theory to our data, the existence of the voltage steps, and the changing susceptibility below the resistive transition indicate that sample disorder plays a more important role in the superconducting transition of composites than is currently accounted for by phase coherent transition theories

Mathematical Modeling of Ultra-Superheated Steam Gasification

Science.gov (United States)

Xin, Fen

Pure steam gasification has been of interest in hydrogen production, but with the challenge of supplying heat for endothermic reactions. Traditional solutions included either combusting feedstocks at the price of decreasing carbon conversion ratio, or using costly heating apparatus. Therefore, a distributed gasifier with an Ultra-Superheated-Steam (USS) generator was invented, satisfying the heat requirement and avoiding carbon combustion in steam gasification. This project developed the first version of the Ultra-Superheated-Steam-Fluidization-Model (USSFM V1.0) for the USS gasifier. A stand-alone equilibrium combustion model was firstly developed to calculate the USS mixture, which was the input to the USSFM V1.0. Model development of the USSFM V1.0 included assumptions, governing equations, boundary conditions, supporting equations and iterative schemes of guessed values. There were three nested loops in the dense bed and one loop in the freeboard. The USSFM V1.0 included one main routine and twenty-four subroutines. The USSFM V1.0 was validated with experimental data from the Enercon USS gasifier. The calculated USS mixture had a trace of oxygen, validating the initial expectation of creating an oxygen-free environment in the gasifier. Simulations showed that the USS mixture could satisfy the gasification heat requirement without partial carbon combustion. The USSFM V1.0 had good predictions on the H2% in all tests, and on other variables at a level of the lower oxygen feed. Provided with higher oxygen feed, the USSFM V1.0 simulated hotter temperatures, higher CO% and lower CO2%. Errors were explained by assumptions of equilibrium combustion, adiabatic reactors, reaction kinetics, etc. By investigating specific modeling data, gas-particle convective heat transfers were found to be critical in energy balance equations of both emulsion gas and particles, while bubble size controlled both the mass and energy balance equations of bubble gas. Parametric study

Influence of geological variations on lignite drying kinetics in superheated steam atmosphere for Belchatow deposit located in the central Poland

Directory of Open Access Journals (Sweden)

Sciazko Anna

2016-01-01

Full Text Available Lignite-fired coal power plants suffer from a significant heat loss due to the high moisture content in this energy carrier. Water removal from fuel is an indispensable treatment for improving the combustion process, which will foster the efficient utilization of lignite. Superheated steam fluidized bed drying is expected for this purpose in a power generation sector. Understanding drying kinetics of lignite will greatly reinforce design process of a dryer. Physical features as well as the drying behaviour may be divergent among the lignite originated from different depths and positions in a certain mine. To reveal and clarify the influence of the geological features, the drying characteristics of several grades of lignite from the Belchatow mine in Poland were investigated. The attempts to clarify the influence of the divergent properties of the investigated samples on the drying kinetics in superheated steam were presented in this paper.

Role of grain size in superconducting boron-doped nanocrystalline diamond thin films grown by CVD

Czech Academy of Sciences Publication Activity Database

Zhang, G.; Janssens, S.D.; Vanacken, J.; Timmermans, M.; Vacík, Jiří; Ataklti, G.W.; Decelle, W.; Gillijns, W.; Goderis, B.; Haenen, K.; Wagner, P.; Moshchalkov, V.V.

2011-01-01

Roč. 84, č. 21 (2011), 214517/1-214517/10 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10480505 Keywords : Nanocrystalline diamond * Superconducting transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

Microstructure and composition of electromagnetically-characterized YBa2Cu3O7-δ grain boundaries

International Nuclear Information System (INIS)

Babcock, S.E.; Zhang, Na; Cai, Xue Yu; Larbalestier, D.C.; Gao, Yufei; Merkle, K.L.; Kaiser, D.L.

1991-01-01

The electrical character (flux-pinning, Josephson junction, or resistive) of the grain boundaries in approximately twenty flux-grown YBa 2 Cu 3 O 7-δ bicrystals was determined in previous studies. A selection of these same bicrystals now have been thinned for study by transmission and scanning transmission electron microscopy. High-spatial resolution imaging and analytical techniques reveal microstructural differences among these boundaries that are consistent with their diverse electrical characteristics. The observations offer preliminary insight into some of the feature that control the grain boundary superconducting properties and re-emphasize the very fine scale on which the grain boundary electrical character is determined. 11 refs., 6 figs

A study on the development of high Tc superconducting materials and on the effects of neutron irradiation

International Nuclear Information System (INIS)

Won, Dong Yeon; Chang, In Soon; Lee, Jong Min

1990-08-01

An Ag-sheathed (Pb,Bi)SrCaCuO superconducting tape was prepared by the cold rolling and post heat treatment method. The tape shows a c-oriented texture perpendicular to the rolling direction. The aligned grain structure may be resulted from the anisotropic grain growth of the high Tc superconducting phase. The bulk (Pb,Bi)SrCaCuO samples with (a) Tc=10lK and (b) 96K were prepared by the solid state reaction method and were neutron-irradiated up to 1.5 x 10 1 8 n/cm 2 . After irradiation the zero resistance temperature(Tc) of (a) was decreased to 96K but (b) did not show any change in Tc. The critical current density of (a) also decreased from 0.75A/cm 2 but (b) was constant as 1.5 A/cm 2 after irradiation. (Author)

Influence of the type of working fluid in the lower cycle and superheated steam parameters in the upper cycle on effectiveness of operation of binary power plant

Directory of Open Access Journals (Sweden)

Stachel Aleksander A.

2015-03-01

Full Text Available In the paper presented have been the results of the analysis of effectiveness of operation of binary power plant consisting of combined two Clausius-Rankine cycles, namely the binary cycle with water as a working fluid in the upper cycle and organic substance as a working fluid in the lower cycle, as well as a single fluid component power plant operating also in line with the C-R cycle for superheated steam, with water as a working fluid. The influence of the parameters of superheated steam in the upper cycle has been assessed as well as the type of working fluid in the lower cycle. The results of calculations have been referred to the single-cycle classical steam power plant operating at the same parameters of superheated steam and the same mass flow rate of water circulating in both cycles. On the basis of accomplished analysis it has been shown that the binary power plant shows a greater power with respect to the reference power plant.

Intrinsic noise of a superheated droplet detector for neutron background measurements in massively shielded facilities

Directory of Open Access Journals (Sweden)

Fernandes Ana C.

2017-01-01

Full Text Available Superheated droplet detectors are a promising technique to the measurement of low-intensity neutron fields, as detectors can be rendered insensitive to minimum ionizing radiations. We report on the intrinsic neutron-induced signal of C2ClF5 devices fabricated by our group that originate from neutron- and alpha-emitting impurities in the detector constituents. The neutron background was calculated via Monte Carlo simulations using the MCNPX-PoliMi code in order to extract the recoil distributions following neutron interaction with the atoms of the superheated liquid. Various nuclear techniques were employed to characterise the detector materials with respect to source isotopes (238U, 232Th and 147Sm for the normalisation of the simulations and also light elements (B, Li having high (α, n neutron production yields. We derived a background signal of ~10-3 cts/day in a 1 liter detector of 1-3 wt.% C2ClF5, corresponding to a detection limit in the order of 10-8 n cm-2s-1. Direct measurements in a massively shielded underground facility for dark matter search have confirmed this result. With the borosilicate detector containers found to be the dominant background source in current detectors, possibilities for further noise reduction by ~2 orders of magnitude based on selected container materials are discussed.

Organic chemical hydrides as storage medium of hydrogen on the basis of superheated liquid-film concept

International Nuclear Information System (INIS)

Shinya Hodoshima; Atsushi Shono; Kazumi Satoh; Yasukazu Saito

2006-01-01

A catalysis pair of tetralin dehydrogenation / naphthalene hydrogenation has been proposed in the present paper as an organic chemical hydride for operating stationary fuel cells. Catalytic naphthalene hydrogenation, having been commercialized since the 1940's, proceeds to generate decalin via tetralin as an intermediate. The storage capacities of tetralin (3.0 wt%, 28.2 kg-H 2 / m 3 ) are lower than decalin (7.3 wt%, 64.8 kg-H 2 / m 3 ) but both tetralin dehydrogenation and naphthalene hydrogenation are much faster than the decalin / naphthalene pair. Moreover, existing infrastructures, e.g., gas station and tank lorry, are available for storage, transportation and supply of hydrogen. As for the stationary fuel cells with large space for hydrogen storage, tetralin as a hydrogen carrier is superior to decalin in terms of fast hydrogen supply. Rapid hydrogen supply from tetralin under mild conditions was only accomplished with the carbon supported metal catalysts in the 'superheated liquid-film states' under reactive distillation conditions. In contrast to the ordinary suspended states, the catalyst layer superheated in the liquid-film state gave high catalytic performances at around 250 C. As a result, serious coke formation over the catalyst surface and excessive exergy consumption were prevented simultaneously. (authors)

From materials control to astrophysics: metastable superconductors

International Nuclear Information System (INIS)

Waysand, G.

1984-01-01

The basic properties of metastable superconducting materials are reviewed: superheated domain, size of the granules, reading of the change of state. In the case of superheating, the phase transition can occur following two paths: a) increase of temperature (thermal nucleation) which allows an analysis of the calorimetric behavior for particle detection; b) increase of the applied magnetic field which allows the evaluation of surface defects promoting the nucleation of the normal state, and, more generally, the study of the superheated material as a disordered system. The thermal nucleation is useful for X-ray detection in non-destructive control as well as for the solar neutrino detection in real time. The magnetic nucleation is the basis for a proposal of detection of magnetic monopoles by induction [fr

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}.

Density and critical current of metal-sheathed superconducting YBa2Cu3Oy ceramics deformed by hydroextrusion and subsequent drawing-rolling

International Nuclear Information System (INIS)

Karpov, M.I.; Korzhov, V.P.; Gnesin, B.A.; Snegirev, A.A.

1994-01-01

The critical-current density j c in ceramic superconductors is strongly dependent on texture, which is determined by the orientation of ceramic grains with respect to the specimen axes and by the misalignment between grains. Y ceramics with prolate grains aligned parallel to the long axis of the specimen were obtained by melt solidification. Such ceramics exhibited j c = 18500 A/cm 2 at 77 K in zero magnetic field. Texturing was also achieved by rolling Ag-sheathed powder of superconducting ceramics. This method ensured critical current densities (2-7) x 10 3 A/cm 2 in Y, Bi, and Tl ceramics. In flat ceramic samples, the grains of a superconducting phase were oriented in such a way that the crystallographic c axis was perpendicular to the rolling plane. In this work, the authors studied the effect of rolling deformation on the current-carrying capacity j c and density p of metal-sheathed YBa 2 Cu 3 O y ceramics that were first subjected to hydroextrusion and drawing at ∼20, 550, and 700 degrees C. The data obtained for j c and p were compared with the texture factor

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).

Chemical casting of high-Tc superconducting BiSCCO

International Nuclear Information System (INIS)

Toth, L.E.; Das, B.N.; Rayne, R.J.; Bender, B.A.; Lechter, W.L.; Hoff, H.A.; Osofsky, M.S.; Soulen, R.J. Jr.

1989-01-01

BiSCCO has been successfully cast into a number of useful shapes. This casting process differs significantly from traditional casting in that the process includes a change in the oxygen content of the melt. A heat treatment is required to restore the original chemistry, properly form the BiSCCO crystal structure and develop the superconducting properties. This paper emphasizes the microstructures of as-cast and heat treated BiSCCO. Casting causes considerable grain alignment of the BiSCCO platelets. The platelets align preferentially along the thermal gradients which exist during the solidification process

Superconducting properties of powder-metallurgically produced Cu-Nb3Sn composite wires

International Nuclear Information System (INIS)

Schaper, W.; Wecker, J.; Heine, K.; Bormann, R.; Freyhardt, H.C.

1988-01-01

The critical current density of composite superconducting wires can be improved by ternary or quaternary additions. If these additions are incorporated into the A15 phase the upper critical field can be increased. An increase in this field, however, can only be realized if the additions do not strongly deteriorate the critical temperature. An enhanced upper critical field in connection with a favorable grain size of the A15 phase finally leads to improved critical current densities in the entire field range. With these parameters as guidelines, the effects of Ti, In, Ga, and Ge additions to the bronze and of Ta additions to the niobium on the superconducting properties of PM produced Cu-Nb 3 Sn wires were investigated

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

Thermophysical properties of a highly superheated and undercooled Ni-Si alloy melt

Science.gov (United States)

Wang, H. P.; Cao, C. D.; Wei, B.

2004-05-01

The surface tension of superheated and undercooled liquid Ni-5 wt % Si alloy was measured by an electromagnetic oscillating drop method over a wide temperature range from 1417 to 1994 K. The maximum undercooling of 206 K (0.13TL) was achieved. The surface tension of liquid Ni-5 wt % Si alloy is 1.697 N m-1 at the liquidus temperature 1623 K, and its temperature coefficient is -3.97×10-4 N m-1 K-1. On the basis of the experimental data of surface tension, the other thermophysical properties such as the viscosity, the solute diffusion coefficient, and the density of liquid Ni-5 wt % Si alloy were also derived.

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

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

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

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

Multi-cell superconducting structures for high energy e+ e- colliders and free electron laser linacs

CERN Document Server

Sekutowicz, J

2008-01-01

This volume, which is the first in the EuCARD Editorial Series on “Accelerator Science and Technology”, is closely combined with the most advanced particle accelerators – based on Superconducting Radio Frequency (SRF) technology. In general, SRF research includes following areas: high gradient cavities, cavity prototyping, thin film technologies, large grain and mono-crystalline niobium and niobium alloys, quenching effects in superconducting cavities, SRF injectors, photo-cathodes, beam dynamics, quality of electron beams, cryogenics, high power RF sources, low level RF controls, tuners, RF power coupling to cavities, RF test infrastructures, etc. The monograph focuses on TESLA structures used in FLASH machine and planned for XFEL and ILC experiments.

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)

Large grain CBMM Nb ingot slices: An ideal test bed for exploring the microstructure-electromagnetic property relationships relevant to SRF

International Nuclear Information System (INIS)

Sung, Zu-Hawn; Lee, Peter J.; Polyanskii, Anatolii; Balachandran, Shreyas; Chetri, Santosh; Larbalestier, David C.; Wang, Mingmin; Compton, Christopher; Bieler, Thomas R.

2015-01-01

High purity (RRR > 200), large grain (> 5-10 cm) niobium ingot slices have been successfully used to fabricate radio frequency (RF) cavities for particle accelerators. They offer significantly reduced fabrication cost by eliminating processing steps and furthermore they provide the opportunity to study the influence of individual grain boundaries in SRF Nb. Here we summarize our measurements of grain boundary (GB) effects on the superconducting properties of large grain high purity niobium sheet manufactured by CBMM. We show by magneto-optical (MO) imaging that GBs allow premature flux penetration, but only when they are oriented close to the direction of the magnetic field. However, even low angle GBs produced by minor deformations commensurate with half-cell forming produce localized flux penetration. The transport properties of grain boundaries were investigated by direct transport across them and evidence for preferential vortex flow along the GBs of SRF Nb was observed for the first time. Using transmission electron microscopy (TEM) and micro crystallographic analysis with electron backscattered diffraction (EBSD), we were able to quantitatively characterize surface substructures that can lead to localized thermal breakdown of superconductivity. Important to these studies was the development of sample preparation techniques that made the cutout single, bi-crystal and tri-crystal Nb coupons as representative as possible of the surface properties of cavities manufactured by standard techniques

Hydrogen storage by organic chemical hydrides and hydrogen supply to fuel cells with superheated liquid-film-type catalysis

International Nuclear Information System (INIS)

Hodoshima, S.; Shono, A.; Sato, K.; Saito, Y.

2004-01-01

Organic chemical hydrides, consisting of decalin / naphthalene and tetralin / naphthalene pairs, have been proposed as the storage medium of hydrogen for operating fuel cells in mobile and static modes. The target values in the DOE Hydrogen Plan, U.S., on storage ( 6.5 wt%, 62.0 kg-H 2 / m 3 ) are met with decalin ( 7.3 wt%, 64.8 kg-H 2 / m 3 ). In addition, existing gas stations and tank lorries are available for storage and supply of hydrogen by utilizing the decalin / naphthalene pair, suggesting that decalin is suitable for operating fuel-cell vehicles. Tetralin dehydrogenation proceeds quite rapidly, assuring a predominant power density, though its storage densities ( 3.0 wt%, 28.2 kg-H 2 / m 3 ) are relatively low. Efficient hydrogen supply from decalin or tetralin by heating at 210-280 o C was attained only with the carbon-supported nano-size metal catalysts in the 'superheated liquid-film states' under reactive distillation conditions, where coke formation over the catalyst surface was prevented. The catalyst layer superheated in the liquid-film states gave high reaction rates and conversions, minimizing the evaporation loss under boiling conditions and exergy loss in hydrogen energy systems. (author)

Heat conduction in superconducting lead thallium alloys

International Nuclear Information System (INIS)

Ho, J.L.N.

1975-01-01

The heat conduction of six strong coupling superconducting Pb--Tl alloy specimens (1 to 20 percent wt Tl) was investigated with the emphasis on the effects of impurities upon the phonon thermal conductivity. All the specimens were annealed at 275 0 C for one week. Results show that the superconducting state phonon thermal conductivity of Pb--Tl is in reasonably good agreement with BRT theory. The strong coupling superconductivity of lead alloys can be handled by scaling the gap parameter using a constant factor. The results presented also show that the phonon thermal conductivity at low temperatures of well annealed lead-thallium alloys can be analyzed in terms of phonon scattering by the grain boundaries, point defects, conduction electrons, and other phonons. The phonon-dislocation scattering was found to be unimportant. The phonon relaxation rate due to point defects is in reasonably good agreement with the Klemens theory for the long range strain field scattering introduced by the thallium impurities. At low temperatures, the normal state phonon thermal conductivity showed an increase in the phonon-electron relaxation rate as the thallium concentration increases. The increase of the phonon-electron relaxation rate is attributed to the change of the Fermi surface caused by the presence of thallium impurity. The effect of the strong electron-phonon coupling character upon the phonon-electron relaxation rate has also been considered in terms of the electron-phonon enhancement factor found in the specific heat measurements

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...

Conductivity and superconductivity of (Bi,Pb)-Sr-Ca-Cu-O

International Nuclear Information System (INIS)

Gazda, M.; Kusz, B.; Klimczuk, T.; Natali, R.; Stizza, S.

2007-01-01

The (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics may be considered as disordered metal and superconductor. Depending on the heat treatment conditions the materials are either composed of the oval grains of the 2212 or 2201 phases embedded in the insulating matrix or they mainly contain the 2212 plate-like crystallites weakly connected one with another. The materials have large resistivity and usually large negative temperature coefficient of resistivity (TCR). The granular and disordered character of the materials is also reflected in their superconducting properties. Both the normal-state and superconducting properties correlate one with another. The glass-ceramic samples were obtained by annealing the amorphous solid at temperatures between 840 and 860 deg. C. The measurements of the temperature dependence of resistivity in annealed samples were carried out with the conventional four-terminal method in a temperature range from 3 to 300 K

Development of a theoretical model for polycrystalline superconducting anisotropic using the effective medium approximation

International Nuclear Information System (INIS)

Cruz-García, A.; Muné, P; Govea-Alcaide, E.

2008-01-01

Full text: In this paper, is a study of the transport properties in anisotropic polycrystalline superconducting. The presence of certain order of orientation of grains in polycrystalline superconducting (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+delta , is modeled by introducing a probability of orientation, gamma factor. In addition, is included in the model the concentration c, which characterize the contribution of porosity to the decrease in the conductivity of the Crystal, transparent. Assumes that pores and pimples are ellipsoid flattened with similar dimensions and takes into account the values of conductivity of beads in each direction. The calculation is based on the application of a generalization of the approximation of the effective way to the study of heterogeneous media, which is called coherent potential approximation (APC). The results are compared with an empirical model developed recently for samples of YBa 2 Cu 3 O 7 -delta (YBCO) which enriches its employment and applied to ceramic superconducting in general. (author)

New results of development on high efficiency high gradient superconducting rf cavities

Energy Technology Data Exchange (ETDEWEB)

Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Li, Z. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hao, Z. K. [Peking Univ., Beijing (China); Liu, K. X. [Peking Univ., Beijing (China); Zhao, H. Y. [OTIC, Ningxia (China); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

2015-09-01

We report on the latest results of development on high-efficiency high-gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are E_acc = 41 MV/m at Q₀ = 6.5×10¹⁰ at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and E_acc = 49 MV/m at Q₀ = 1.5×10¹⁰ at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

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.

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.

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

Large Tc depression at low angle [100] tilt grain boundaries in bulk Bi2Sr2CaCu2O8+δ bicrystals

International Nuclear Information System (INIS)

Li, Q.; Tsay, Y.N.; Zhu, Y.; Suenaga, M.; Gu, G.D.; Koshizuka, N.

1997-01-01

Large depression of T c at 7 degree [100] tilt grain boundaries was observed in bulk Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) bicrystals by measuring the zero-field electrical transport properties of the grain boundaries and the constituent single crystals over an extended range of currents and voltages. The T c -depressed region was determined to be around 20 nm, comparable to the width of the strain field associated with the observed array of grain-boundary dislocations. Superconducting coupling of the grain boundaries increases sharply as temperature decreases below the grain-boundary T c congruent 68 K. copyright 1997 American Institute of Physics

Firetube boiler with high efficiency for producing saturated or superheated steam

Energy Technology Data Exchange (ETDEWEB)

Carosso, V J; Carosso, J Y

1976-10-07

This boiler for producing saturated or super-heated steam is to be manufactured in one piece or in units which can be assembled at site without skilled workers, at the factory. It is to have a high efficiency and dimensions which permit the transport of the completely assembled boiler by road transport. The relatively small water-steam vessel lies across the longitudinal axis of the boiler in the rear boiler space over a battery of preheater tubes. By these measures and by a very detailed and appropriately described rational arrangement of other parts, such as convection bundles, primary and secondary superheater, evaporation tubes, which form an 'evaporation shield', upper and lower longitudinal chambers with vertical connecting pipes of different crossections, the above mentioned condition for space requirement is fulfilled and a high efficiency should be achieved, but with considerable expense.

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.

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)

Numerical analysis of single and multiple particles of Belchatow lignite dried in superheated steam

Science.gov (United States)

Zakrzewski, Marcin; Sciazko, Anna; Komatsu, Yosuke; Akiyama, Taro; Hashimoto, Akira; Kaneko, Shozo; Kimijima, Shinji; Szmyd, Janusz S.; Kobayashi, Yoshinori

2018-03-01

Low production costs have contributed to the important role of lignite in the energy mixes of numerous countries worldwide. High moisture content, though, diminishes the applicability of lignite in power generation. Superheated steam drying is a prospective method of raising the calorific value of this fuel. This study describes the numerical model of superheated steam drying of lignite from the Belchatow mine in Poland in two aspects: single and multi-particle. The experimental investigation preceded the numerical analysis and provided the necessary data for the preparation and verification of the model. Spheres of 2.5 to 30 mm in diameter were exposed to the drying medium at the temperature range of 110 to 170 °C. The drying kinetics were described in the form of moisture content, drying rate and temperature profile curves against time. Basic coal properties, such as density or specific heat, as well as the mechanisms of heat and mass transfer in the particular stages of the process laid the foundations for the model construction. The model illustrated the drying behavior of a single particle in the entire range of steam temperature as well as the sample diameter. Furthermore, the numerical analyses of coal batches containing particles of various sizes were conducted to reflect the operating conditions of the dryer. They were followed by deliberation on the calorific value improvement achieved by drying, in terms of coal ingredients, power plant efficiency and dryer input composition. The initial period of drying was found crucial for upgrading the quality of coal. The accuracy of the model is capable of further improvement regarding the process parameters.

Chevrel phases superconductive and ultrafine powders synthesis and characterization; Synthese et caracterisation de poudres ultrafines supraconductrices de phases de Chevrel

Energy Technology Data Exchange (ETDEWEB)

Even-Boudjada, S

1994-12-01

This work deals with the Chevrel phases superconductive and ultrafine powders synthesis and characterization. The first part of this study presents some new way of synthesis (precipitation, coprecipitation) of Chevrel phases precursors powders (PbS, SnS, MoS{sub 2}) and their characterizations (X-ray fluorescence analysis, ICP mass spectroscopy, scanning electron microscopy, transmission electron microscopy and laser granulometry). These new synthesis methods lead to quasi spherical morphology grains and very weak size grains (0.2 to 0.5 {mu}m) whereas the chemical preparation from the solid state elements gives very different morphology grains (small plates) with a size of 1 to 20 {mu}m. In the second part is shown the interest of the binary Mo{sub 6} S{sub 8} as precursor in the synthesis of ternary superconductive phases (Li, Ni, Cu, Pb). The last part presents the formation reaction of the phase PbMo{sub 6} S{sub 8} and its main chemical and physical properties. Thus some calorimetric measures associated with X-ray diffraction analysis have been realized and have allowed to understand the different reactions occurring during the PbMo{sub 6}S{sub 8} synthesis. (O.L.). 100 refs., figs., tabs.

Misfit dislocations and phase transformations in high-T sub c superconducting films

CERN Document Server

Gutkin, M Y

2002-01-01

A theoretical model is suggested that describes the effects of misfit stresses on defect structures, phase content and critical transition temperature T sub c in high-T sub c superconducting films. The focus is placed on the exemplary case of YBaCuO films deposited onto LaSrAlO sub 4 substrates. It is theoretically revealed here that misfit stresses are capable of inducing phase transformations controlled by the generation of misfit dislocations in growing cuprate films. These transformations, in the framework of the suggested model, account for experimental data on the influence of the film thickness on phase content and critical temperature T sub c of superconducting cuprate films, reported in the literature. The potential role of stress-assisted phase transformations in suppression of critical current density across grain boundaries in high-T sub c superconductors is briefly discussed.

First runs with the ORPHEUS dark matter detector

CERN Document Server

Czapek, G; Hauser, M; Janos, S; Loaiza, P; Moser, U; Pretzl, K; Brandt, B V D; Konter, J A; Mango, S; Ebert, T; Kainer, K U; Knoop, K M

2002-01-01

The ORPHEUS dark matter experiment is completed at our shallow depth laboratory in Bern (70 m.w.e.). The detector relies on measuring the magnetic flux variation produced by weakly interacting massive particles (WIMPs) as they heat 30 mu m diameter superheated superconducting tin granules (SSG) and induce superconducting-to-normal phase transitions. In an initial phase, 0.45 kg of tin granules in a segmented detector volume have been used. Preliminary results of the experiment will be reported.

Transport relaxation measurements and glassy state effects in superconducting MgB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Olutas, M. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey)], E-mail: olutas_m@ibu.edu.tr; Yetis, H.; Altinkok, A.; Kilic, A.; Kilic, K. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey)

2008-09-15

Time dependent effects in superconducting MgB{sub 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 {approx}1 {mu}V), 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.

Statistical evaluations concerning the failure behaviour of formed parts with superheated steam flow. Pt. 1

International Nuclear Information System (INIS)

Oude-Hengel, H.H.; Vorwerk, K.; Heuser, F.W.; Boesebeck, K.

1976-01-01

Statistical evaluations concerning the failure behaviour of formed parts with superheated-steam flow were carried out using data from VdTUEV inventory and failure statistics. Due to the great number of results, the findings will be published in two volumes. This first part will describe and classify the stock of data and will make preliminary quantitative statements on failure behaviour. More differentiated statements are made possible by including the operation time and the number of start-ups per failed part. On the basis of time-constant failure rates some materials-specific statements are given. (orig./ORU) [de

Simulation of shell-and-tube condensers of the refrigerating machines with superheated and subcooled refrigerant

International Nuclear Information System (INIS)

Ciconkov, Risto

1994-01-01

Opposite to many authors who found the simulation of the shell-and-tube condensers on the condensing process only, in this work all thermodynamic processes which appear such as: the process of cooling the superheated refrigerant to the saturated vapor, the process of condensation and option with subcooling are considered. A selection of heat transfer equations is made corresponding to the processes, a mathematical model and adequate computer programme are composed. The functioning of this programme is presented on a concrete example. A computer programing knowledge for the using programme is not necessary. Neither is a programme support. (author)

A neutron spectrometer based on temperature variations in superheated drop compositions

CERN Document Server

Apfel, R E

2002-01-01

The response of superheated drop detectors (SDDs) to neutron radiation varies in a self-consistent manner with variations in temperature and pressure, making such compositions suitable for neutron spectrometry. The advantage of this approach is that the response functions of candidate materials versus energy as the temperature or pressure is varied are nested and have distinct thresholds, with no thermal neutron response. These characteristics permit unfolding without the uncertainties associated with other spectrometry techniques, where multiple solutions are possible, thus requiring an initial guess of the spectrum. A spectrometer was developed based on the well-established technology for acoustic sensing of bubble events interfaced with a proportional-integral-derivative temperature controller. The active monitor for neutrons, called REMbrandt sup T sup M , was used as the platform for controlling temperature on a SDD probe and for data acquisition, thereby automating the process of measuring the neutron e...

Numerical simulation and analysis of single grain YBCO processed from graded precursor powders

OpenAIRE

Zou, J; Ainslie, Mark Douglas; Hu, D; Zhai, W; Kumar, N Devendra; Durrell, John Hay; Shi, Yunhua; Cardwell, David Anthony

2015-01-01

Large single-grain bulk high-temperature superconducting materials can trap high magnetic fields in comparison with conventional permanent magnets, making them ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. However, macro-segregation of Y-211 inclusions in melt processed Y–Ba–Cu–O (YBCO) limits the macroscopic critical current density Jc of such bulk supercond...

Vertical Growth of Superconducting Crystalline Hollow Nanowires by He+ Focused Ion Beam Induced Deposition.

Science.gov (United States)

Córdoba, Rosa; Ibarra, Alfonso; Mailly, Dominique; De Teresa, José Ma

2018-02-14

Novel physical properties appear when the size of a superconductor is reduced to the nanoscale, in the range of its superconducting coherence length (ξ 0 ). Such nanosuperconductors are being investigated for potential applications in nanoelectronics and quantum computing. The design of three-dimensional nanosuperconductors allows one to conceive novel schemes for such applications. Here, we report for the first time the use of a He + focused-ion-beam-microscope in combination with the W(CO) 6 precursor to grow three-dimensional superconducting hollow nanowires as small as 32 nm in diameter and with an aspect ratio (length/diameter) of as much as 200. Such extreme resolution is achieved by using a small He + beam spot of 1 nm for the growth of the nanowires. As shown by transmission electron microscopy, they display grains of large size fitting with face-centered cubic WC 1-x phase. The nanowires, which are grown vertically to the substrate, are felled on the substrate by means of a nanomanipulator for their electrical characterization. They become superconducting at 6.4 K and show large critical magnetic field and critical current density resulting from their quasi-one-dimensional superconducting character. These results pave the way for future nanoelectronic devices based on three-dimensional nanosuperconductors.

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.

Metallurgy, fabrication, and superconducting properties of multifilamentary Nb3Al composites

International Nuclear Information System (INIS)

Hafstrom, J.W.

1976-01-01

The control of metallurgical structure during fabrication that will improve the superconducting properties of multifilamentary, aluminium-stabilized, Nb 3 Al composites is described. Composites are fabricated by placing niobium rods in an aluminum matrix, and then drawing to wire. Nb 3 Al is formed at temperatures exceeding 1800 0 C for about 5 s and ordered at 750 0 C for 48 h. A critical current, J/sub c/(H), in excess of 10 5 A/cm 2 (F/sub p/ approximately equal to 7 x 10 8 dynes/cm 3 ) at 7 T and a T/sub c/ to 18.2 K are obtained. Attempts to improve J/sub c/(H) by controlling the grain size in the Nb 3 Al diffused layer are discussed. Precipitates, arising from the addition of carbon during Nb 3 Al layer growth, do not appear to be effective as grain-boundary or flux pinners. When 1 percent Zr is added to the Nb, the growth of the Nb 3 Al layer is accelerated, T/sub c/ is lowered and J/sub c/(H) is not significantly improved. J/sub c/(H) rapidly decreases with an increase in Nb 3 Al or (Nb-Zr) 3 Al layer thickness, d. J/sub c/(H) is independent of d in composites with d greater than or approximately equal to 1.5 μm. In general, the Nb 3 Al grain size appears comparable to d for d less than or equal to 1 μm. Significant improvement of J/sub c/(H) for Nb 3 Al superconducting composites reacted at temperatures above 1800 0 C (to achieve T/sub c/ greater than 17 K) is achieved only by maintaining the layer thickness well below d approximately equal to 1.0 μm

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.

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

Neutron detection using superheated drops. Progress report, 1 May 1981-15 November 1982

International Nuclear Information System (INIS)

Apfel, R.E.

1981-11-01

The goal of this research has been to determine whether neutron detectors based on superheated drops not only have the characteristics desirable for neutron dosimetry (sensitivity and energy response, etc.) but also have the practical attributes (stability and ease of handling) which warrant later commercial development. Initial experiments with five materials (Freons 12, 114, 142B, and isobutane and cis-2-butene) indicate threshold neutron energies ranging from thermal to 5 MeV depending on the material, and an energy response which follows the general shape of the dose equivalent response of the body as set forth by the Commission on Radiological Protection (ICRP). This indicates that one can choose a drop material to meet a wide variety of objectives

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...

Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

Energy Technology Data Exchange (ETDEWEB)

Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

2017-06-01

In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

Recent progress in large grain/single crystal high RRR niobium

International Nuclear Information System (INIS)

Ganapati Rao Myneni; Peter Kneisel; Tadeu Carneiro; S.R. Agnew; F. Stevie

2005-01-01

High RRR bulk niobium Superconducting Radio Frequency (SRF) cavity technology is chosen for the International Linear Collider (ILC). The SRF community was convinced until now that fine grain polycrystalline RRR niobium sheets obtained via forging and cross rolling are essential for forming the SRF Cavities. However, it was recently discovered under a joint Reference Metals Company, Inc., - JLAB CRADA that large grain/single crystal RRR niobium sliced directly from ingots is highly ductile reaching 100 percent elongation. This discovery led to the successful fabrication of several SRF single and/or multi cell structures, formed with sliced RRR discs from the ingots, operating at 2.3, 1.5 and 1.3 GHz. This new exciting development is expected to offer high performance accelerator structures not only at reduced costs but also with simpler fabrication and processing conditions. As a result there is a renewed interest in the evaluation and understanding of the large grain and single crystal niobium with respect to their mechanical and physical properties as well as the oxidation behavior and the influence of impurities such as hydrogen and Ta. In this paper the results of many collaborative studies on large grain and single crystal high RRR niobium between JLAB, Universities and Industry are presented

Microimpurity composition of superconducting ceramics

International Nuclear Information System (INIS)

Zhiglov, Yu.S.; Poltoratskij, Yu.B.; Protsenko, A.N.; Tuchin, O.V.

1989-01-01

Using laser mass spectrometry, the microimpurity composition of YBa 2 Cu 3 O 7-y superconducting ceramics, prepared by routine solid-phase synthesis from extremely pure yttrium and copper oxides and BaCO 3 , is determined. The presence of F, Na, Al, P, Cl, S, K, Ca impurities, which concentration in specimens varies within 10 -3 +5x10 -3 at.% and also Si, Sr, Fe of about 1x10 -1 at.% is established. It is difficult to determine concentrations of C, N, H 2 O impurities because of the presence of background signals of residual gases in the chamber. Using the method of Auger electron spectroscopy, a surface layer of HTSC ceramics grain is studied. The availability of chlorine impurity, which amount considerably exceeds its volume concentration, is determined in near the surface layer. 2 refs.; 2 figs

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.)

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

PREFACE: EUCAS '09: The 9th European Conference on Applied Superconductivity (Dresden, Germany, 13-17 September 2009) EUCAS '09: The 9th European Conference on Applied Superconductivity (Dresden, Germany, 13-17 September 2009)

Science.gov (United States)

Holzapfel, Bernhard; Schultz, Ludwig; Schlörb, Heike

2010-03-01

During the 9th European Conference on Applied Superconductivity, 6 plenary, 22 invited, 206 oral and 429 poster contributions were presented on recent developments in the field of applied superconductivity. This issue of Superconductor Science and Technology contains plenary, invited and a selection of contributed oral papers of the four main EUCAS areas: materials, wires and tapes, large scale applications and electronics. The remaining contributed papers that were selected for the conference proceedings will be published in the Journal of Physics: Conference Series. The Dresden EUCAS conference, with 712 participants from 43 countries, continued the tradition of preceding EUCAS conferences of combining basic superconductivity research contributions with the discussion of recent material advances and new developments in large scale and electronic applications. In Dresden, contributions on the recently discovered Fe-based superconductors were presented for the first time during a EUCAS conference and their potential for applications was intensively discussed. Among all the high level papers of this issue we particularly want to highlight the plenary contribution of Praveen Chaudhari on grain boundaries in cuprate superconductors. In his paper Praveen discusses the Jc limitation in HTSC tapes and tunnelling spectroscopy in LSCO thin film bicrystals. Just a few weeks ago we received the sad news that Praveen had passed away on 13 January 2010. Already fighting with his serious illness, Praveen spent all his efforts last fall finishing his plenary talk and paper. This paper will remind us always of his contributions to basic and applied aspects of superconductivity in general and especially his important work on HTSC grain boundaries. Finally we want to acknowledge the help of the International Advisory and National Committees in setting up the scientific program and we would especially like to express our gratitude to all the members of the Local Organization

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 ...

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

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

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.

Surface and grain boundary modifications of YBa2Cu3O7-δ ceramics by plasma-enhanced fluorination

International Nuclear Information System (INIS)

Magro, C.; Heintz, J.M.; Etourneau, J.; Tressaud, A.; Cardinaud, C.; Turban, G.; Hudakova, N.

1994-01-01

The radiofrequency plasma technique involving mixtures of CF 4 + O 2 gases has been applied to the treatment of high T c superconducting oxides (YBa 2 Cu 3 O 7-δ ). The investigation of the various experimental parameters of the process has shown that the improvement of the critical current density J c mainly depends on the inlet precursor composition CF 4 + τ % O 2 , on the total pressure, and on the reaction time. The presence of fluorine in the bulk of the ceramics has been observed from electron microprobe analysis, together with an increase of the open-quotes Cu 3+ close quotes content. The plasma enhanced fluorination (PEF) treatment improves the superconducting properties of the materials: both values of the resistivity in the normal state and of the superconducting transition width are reduced and the critical transition temperature is improved of about 1 K. Mechanisms of interaction between the reactive species of the plasma and YBa 2 Cu 3 O 7-δ ceramics have been proposed through detailed angle resolved X-ray photoelectron spectroscopic analyses. At the surface of the outer grains, the plasma treatment removes (OH) - and (CO 3 ) 2- species contained in the degradation layer and gives rise to a fluoride-rich layer. In the bulk of the material the occurrence of metal-fluorine bonds in the superconducting phase has to be assumed. Moreover, interactions between atomic fluorine and grain boundaries result in an improvement of intergranular magnetic behavior, according to a.c. susceptibility measurements. An increase of the oxidation state of copper has also been detected, confirming the oxidizing effect of the plasma treatment

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

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

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

Microstructures and superconducting properties of Y-Ba-Cu and Bi-Sr-Ca-Cu oxide wires and coils prepared by the explosive compaction technique

International Nuclear Information System (INIS)

Hagino, S.; Suzuki, M.; Takeshita, T.; Takashima, K.; Tonda, H.

1989-01-01

It has been shown that explosive compaction technique can be used to densify metal, and ceramics powders and their mixtures. The authors discuss how they applied this technique to produce silver sheathed superconducting oxide wires and coils (Y-B-Cu-O and Bi-Sr-Ca-Cu-O). The wires and coils to be compacted were placed into metal tube and the tube was filled with SiC powder as a pressure propagating medium and the tube was compacted by a cylindrically axisymmetric method. The wires and coils compacted were then heat-treated in order to improve grain boundary connections of superconducting oxide crystalline grains. The oxide cores heat-treated were seen to be very dense, and a part of a Y-Ba-Cu oxide coil which was heat-treated optimally was found to have a critical current density higher than 13,000A/cm 2 at 77K

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)

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.

Growth orientation and superconducting properties of YBa2Cu3O7-δ films prepared by the low-fluorine sol-gel process

International Nuclear Information System (INIS)

Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan

2010-01-01

YBa 2 Cu 3 O 7-δ (YBCO) films were deposited on (100)-oriented LaAlO 3 (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF 2 and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)

Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

Energy Technology Data Exchange (ETDEWEB)

Kneisel, P., E-mail: kneisel@jlab.org [Jefferson Lab, Newport News, VA 23606 (United States); Ciovati, G.; Dhakal, P. [Jefferson Lab, Newport News, VA 23606 (United States); Saito, K. [Michigan State University, East Lansing, MI 48824 (United States); Singer, W.; Singer, X. [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Myneni, G.R., E-mail: rao@jlab.org [Jefferson Lab, Newport News, VA 23606 (United States)

2015-02-21

As a result of collaboration between Jefferson Lab and niobium manufacturer Companhia Brasileira de Metalurgia e Mineração (CBMM), ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large-grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This work triggered research activities in other SRF laboratories around the world. Large-grain (LG) niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this technology. Many single cell cavities made from material of different suppliers have been tested successfully and several multi-cell cavities have shown performances comparable to the best cavities made from standard fine-grain niobium. Several 9-cell cavities fabricated by Research Instruments and tested at DESY exceeded the best performing fine grain cavities with a record accelerating gradient of E{sub acc}=45.6 MV/m. The quality factor of those cavities was also higher than that of fine-grain (FG) cavities processed with the same methods. Such performance levels push the state-of-the art of SRF technology and are of great interest for future accelerators. This contribution reviews the development of ingot niobium technology and highlights some of the differences compared to standard FG material and opportunities for further developments.

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

Superconducting state mechanisms and properties

CERN Document Server

Kresin, Vladimir Z; Wolf, Stuart A

2014-01-01

'Superconducting State' provides a very detailed theoretical treatment of the key mechanisms of superconductivity, including the current state of the art (phonons, magnons, and plasmons). A very complete description is given of the electron-phonon mechanism responsible for superconductivity in the majority of superconducting systems, and the history of its development, as well as a detailed description of the key experimental techniques used to study the superconducting state and determine the mechanisms. In addition, there are chapters describing the discovery and properties of the key superconducting compounds that are of the most interest for science, and applications including a special chapter on the cuprate superconductors. It provides detailed treatments of some very novel aspects of superconductivity, including multiple bands (gaps), the "pseudogap" state, novel isotope effects beyond BCS, and induced superconductivity.

Microstructure of Josephson junctions: Effect on supercurrent transport in YBCO grain boundary and barrier layer junctions

International Nuclear Information System (INIS)

Merkle, K.L.; Huang, Y.

1998-01-01

The electric transport of high-temperature superconductors, such as YBa 2 Cu 3 O 7-x (YBCO), can be strongly restricted by the presence of high-angle grain boundaries (GB). This weak-link behavior is governed by the macroscopic GB geometry and the microscopic grain boundary structure and composition at the atomic level. Whereas grain boundaries present a considerable impediment to high current applications of high T c materials, there is considerable commercial interest in exploiting the weak-link-nature of grain boundaries for the design of microelectronic devices, such as superconducting quantum interference devices (SQUIDs). The Josephson junctions which form the basis of this technology can also be formed by introducing artificial barriers into the superconductor. The authors have examined both types of Josephson junctions by EM techniques in an effort to understand the connection between microstructure/chemistry and electrical transport properties. This knowledge is a valuable resource for the design and production of improved devices

New ideas on the detection of cold dark matter and magnetic monopoles

International Nuclear Information System (INIS)

Gonzalez-Mestres, L.; Perret-Gallix, D.

1988-05-01

Superheated superconducting granules (SSG) provide several interesting targets for cold dark matter detection, not only through coherent scattering off nuclei, but also for Majorana fermions through spin-spin interactions. The concept of 'localized micro-avalanche' should introduce crucial improvements in SSG devices and, eventually, make feasible a cold dark matter detector based on nucleus recoil. Recent results on the metastability of very large granules also suggest that a SSG large area monopole detector may be feasible, if the theoretically conjectured detection principle (destruction of the superheated state by two injected flux quanta) is checked experimentally. We also consider the use of special crystal scintillators to detect Majorana fermions through inelastic scattering

Enhanced superconductivity of fullerenes

Energy Technology Data Exchange (ETDEWEB)

Washington, II, Aaron L.; Teprovich, Joseph A.; Zidan, Ragaiy

2017-06-20

Methods for enhancing characteristics of superconductive fullerenes and devices incorporating the fullerenes are disclosed. Enhancements can include increase in the critical transition temperature at a constant magnetic field; the existence of a superconducting hysteresis over a changing magnetic field; a decrease in the stabilizing magnetic field required for the onset of superconductivity; and/or an increase in the stability of superconductivity over a large magnetic field. The enhancements can be brought about by transmitting electromagnetic radiation to the superconductive fullerene such that the electromagnetic radiation impinges on the fullerene with an energy that is greater than the band gap of the fullerene.

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.

Hole superconductivity

International Nuclear Information System (INIS)

Hirsch, J.E.; Marsiglio, F.

1989-01-01

The authors review recent work on a mechanism proposed to explain high T c superconductivity in oxides as well as superconductivity of conventional materials. It is based on pairing of hole carriers through their direct Coulomb interaction, and gives rise to superconductivity because of the momentum dependence of the repulsive interaction in the solid state environment. In the regime of parameters appropriate for high T c oxides this mechanism leads to characteristic signatures that should be experimentally verifiable. In the regime of conventional superconductors most of these signatures become unobservable, but the characteristic dependence of T c on band filling survives. New features discussed her include the demonstration that superconductivity can result from repulsive interactions even if the gap function does not change sign and the inclusion of a self-energy correction to the hole propagator that reduces the range of band filling where T c is not zero

Emergent Higgsless Superconductivity

Directory of Open Access Journals (Sweden)

Cristina Diamantini M.

2017-01-01

Full Text Available We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalizable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D-1-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact lowenergy effective BF theories. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2 and the topological order (4 are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D thi! s type of superconductivity is explicitly realized as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

Superconducting Fullerene Nanowhiskers

Directory of Open Access Journals (Sweden)

Yoshihiko Takano

2012-04-01

Full Text Available We synthesized superconducting fullerene nanowhiskers (C₆₀NWs by potassium (K intercalation. They showed large superconducting volume fractions, as high as 80%. The superconducting transition temperature at 17 K was independent of the K content (x in the range between 1.6 and 6.0 in K-doped C₆₀ nanowhiskers (K_xC₆₀NWs, while the superconducting volume fractions changed with x. The highest shielding fraction of a full shielding volume was observed in the material of K_3.3C₆₀NW by heating at 200 °C. On the other hand, that of a K-doped fullerene (K-C₆₀ crystal was less than 1%. We report the superconducting behaviors of our newly synthesized K_xC₆₀NWs in comparison to those of K_xC₆₀ crystals, which show superconductivity at 19 K in K₃C₆₀. The lattice structures are also discussed, based on the x-ray diffraction (XRD analyses.

Superconducting quantum electronics

International Nuclear Information System (INIS)

Kose, V.

1989-01-01

This book reviews recent accomplishments, presents new results and discusses possible future developments of superconducting quantum electronics and high T c superconductivity. The three main parts of the book deal with fundamentals, sensitive detectors, and precision metrology. New results reported include: correct equivalent circuits modelling superconducting electronic devices; exact solution of the Mattis-Bardeen equations describing various experiments for thin films; complete theoretical description and experimental results for a new broad band spectrum analyzer; a new Josephson junction potentiometer allowing tracing of unknown voltage ratios back to well-known frequency ratios; and fast superconducting SQUID shift registers enabling the production of calculable noise power spectra in the microwave region

Superheated emulsions for the detection of special nuclear material

International Nuclear Information System (INIS)

D’Errico, Francesco; Di Fulvio, Angela

2011-01-01

A novel solution for the detection and smuggling interdiction of special nuclear materials is presented here consisting of large detector modules which contain superheated emulsions and which are readout with an optical approach. The detectors can be produced to be fully sensitive to prompt fission neutrons and totally insensitive to the interrogation beam, whether X-rays or neutrons below a chosen energy threshold. Therefore, the detectors are able to operate while the selected interrogation beam is on and they will only pick up the signal from fission neutrons. A position-sensitive readout mechanism is used in our design, relying on the scattering of light by neutron-induced bubbles. A beam of coherent light crosses the active area of the detector, and local variations in scattered light due to the presence of bubbles are detected in real time by arrays of silicon planar photodiodes affixed along the whole length of the detector. The system may offer a variety of advantages compared to current approaches, such as the possibility of simultaneous irradiation and detection, i.e. a 100% duty cycle, without requiring complex signal analysis, and high signal-to-noise ratio, minimizing costly nuisance alarms, thanks to its inherent insensitivity to photons.

Superconductivity in graphite intercalation compounds

International Nuclear Information System (INIS)

Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P.M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

2015-01-01

Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC 6 and YbC 6 in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition

Superconductivity in graphite intercalation compounds

Energy Technology Data Exchange (ETDEWEB)

Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

2015-07-15

Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Science.gov (United States)

Sheikhzada, Ahmad K.

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Energy Technology Data Exchange (ETDEWEB)

Sheikhzada, Ahmad [Old Dominion Univ., Norfolk, VA (United States)

2017-05-01

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

A three-dimensional numerical study on dynamics behavior of a rising vapor bubble in uniformly superheated liquid by lattice Boltzmann method

International Nuclear Information System (INIS)

Sun, Tao; Sun, Jiangang; Ang, Xueye; Li, Shanshan; Su, Xin

2016-01-01

Highlights: • Dynamics of vapor bubble in uniformly superheated liquid is studied by a 3D LBM. • The growth rate reaches a maximum value and then decrease until a certain value. • The vapor bubble will take place a larger deformation at high ratio of Re/Eo. • The bubble wake has a great influence on motion and deformation of vapor bubble. • Ratio of Re/Eo has an important influence on evolution of temperature field. - Abstract: In this paper, dynamics behaviors of a rising vapor bubble in uniformly superheated liquid are firstly studied by a hybrid three-dimensional lattice Boltzmann model. In order to validate this model, two test cases regarding bubble rising in an isothermal system and vapor bubble growth in a superheated liquid are performed, respectively. The test results are consistent with existing results and indicate the feasibility of the hybrid model. The hybrid model is further applied to simulate growth and deformation of a rising vapor bubble in different physical conditions. Some physical parameters of vapor bubble such as equivalent diameter and growth rate are evaluated accurately by three-dimensional simulations. It is found that the growth rate of vapor bubble changes with time and temperature gradient. It reaches a maximum value at the initial stage and then decrease until a certain value. The growth and deformation of vapor bubble at different ratios of Re/Eo are discussed. The numerical results show the vapor bubble will take place a larger deformation at high ratio of Re/Eo at the middle and final stages. In addition, the hybrid model is also applied to predict the evolution of flow and temperature fields. The bubble wake has a great influence on the motion and deformation of vapor bubble during rising process. As far as the temperature field is concerned, a ratio of Re/Eo has an important influence on heat transfer and evolution of temperature field.

X-ray diffraction pattern and morphology of superconducting Nb/sub 3/Sn layer grown on a polycrystalline Nb substrate of (111) main texture

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B [Politechnika Wroclawska (Poland)

1983-01-16

A study is presented on structure and crystallographic orientation of Nb/sub 3/Sn layers formed in the process of interaction of polycrystalline Nb substrate with Cu/sub 0.2/Sn/sub 0.8/ solution at 980 /sup 0/C. Grain structure characterization of Nb/sub 3/Sn layers has been carried out with scanning electron microscopy and TV automatic image analysis. The superconducting layer is divided into a fine-grained FG and coarse-grained CG zone. The X-ray patterns of FG and CG zones did not differ from one another and were the same as in randomly oriented Nb/sub 3/Sn polycrystalline powder.

Modern high-temperature superconductivity

International Nuclear Information System (INIS)

Ching Wu Chu

1988-01-01

Ever since the discovery of superconductivity in 1911, its unusual scientific challenge and great technological potential have been recognized. For the past three-quarters of a century, superconductivity has done well on the science front. This is because sueprconductivity is interesting not only just in its own right but also in its ability to act as a probe to many exciting nonsuperconducting phenomena. For instance, it has continued to provide bases for vigorous activities in condensed matter science. Among the more recent examples are heavy-fermion systems and organic superconductors. During this same period of time, superconductivity has also performed admirably in the applied area. Many ideas have been conceived and tested, making use of the unique characteristics of superconductivity - zero resistivity, quantum interference phenomena, and the Meissner effect. In fact, it was not until late January 1987 that it became possible to achieve superconductivity with the mere use of liquid nitrogen - which is plentiful, cheap, efficient, and easy to handle - following the discovery of supercondictivity above 90 K in Y-Ba-Cu-O, the first genuine quaternary superconductor. Superconductivity above 90 K poses scientific and technological challenges not previously encountered: no existing theories can adequately describe superconductivity above 40 K and no known techniques can economically process the materials for full-scale applications. In this paper, therefore, the author recalls a few events leading to the discovery of the new class of quaternary compounds with a superconducting transition temperature T c in the 90 K range, describes the current experimental status of high-temperature superconductivity and, finally, discusses the prospect of very-high-temperature superconductivity, i.e., with a T c substantially higher than 100 K. 97 refs., 7 figs

Inhomogeneous superconductivity in a ferromagnet

International Nuclear Information System (INIS)

Kontos, T.; Aprili, M.; Lesueur, J.; Genet, F.; Boursier, R.; Grison, X.

2003-01-01

We have studied a new superconducting state where the condensate wave function resulting from conventional pairing, is modified by an exchange field. Superconductivity is induced into a ferromagnetic thin film (F) by the proximity effect with a superconducting reservoir (S). We observed oscillations of the superconducting order parameter induced in F as a function of the distance from the S/F interface. They originate from the finite momentum transfer provided to Cooper pairs by the splitting of the spin up and down bands. We measured the superconducting density of states in F by tunneling spectroscopy and the Josephson critical current when F is coupled with a superconducting counter-electrode. Negative values of the superconducting order parameter are revealed by capsized tunneling spectra in F and a negative Josephson coupling (π-junction)

Attentuation effect of sprinklers on a superheated environment using COMPACT

International Nuclear Information System (INIS)

Wills, M.E.

1991-01-01

As a result of a high-energy line break (HELB) in the auxiliary building of a pressurized water reactor, superheated steam is released through a 15.2-cm (6-in.) break in the main stream line. A sophisticated analytical tool is needed to simulate the effects of natural circulation airflow in the building. The COMPACT computer code was used for this study not only because of its ability to model natural circulation airflow but also because it is a recognized and approved tool for outside containment steam-line break applications. Two cases were analyzed in this study. The first case did not model the Appendix R fire protection sprinklers in the break node, while the second case did. Previous conservative analyses have shown that four sprinklers would be available, each providing a flow rate of ∼15 gal/min. A fusible link must fail in order to actuate the sprinklers, and conservative calculations show that the failure time would be 113 s from event initiation. Since the sprinkler headers are already full of water, there is no additional delay time for sprinkler flow to the break compartment

Cryogenic properties of austenitic stainless steels for superconducting magnet

International Nuclear Information System (INIS)

Nohara, K.; Kato, T.; Ono, Y.; Sasaki, T.; Suzuki, S.

1983-01-01

The present study examines the magnetic and mechanical properties of a variety of austenitic stainless steels and high maganese steel which are candidate materials for the superconducting magnet attached to high energy particle accelerators. The effect of a specified heat treatment for the precipitation of intermetallic compound Nb3Sn to be used as superconductor on ductility and toughness are especially examined. It is found that nitrogen-strengthened austenitic stainless steels have high strength and good ductility and toughness, but that these are destroyed by precipitation treatment. The poor ductility and toughness after precipitation are caused by a weakening of the grain boundaries due to the agglomerated chromium carbide percipitates. The addition of vanadium suppresses this effect by refining the grain. Austenitic steels are found to have low magnetic permeabilities and Neel temperatures, and show serrated flow in traction test due to strained martensitic transformation. High manganese steel has extremely low permeability, a Neel temperature about room temperature, and has a serrated flow in traction test due to adiabatic deformation at liquid helium temperature

WORKSHOP: Radiofrequency superconductivity

Energy Technology Data Exchange (ETDEWEB)

Anon.

1984-10-15

The Second Workshop on Radiofrequency Superconductivity was held at CERN from 23-27 July, four years after the first, organized at Karlsruhe. 35 invited talks were presented to the about 80 participants from Australia, Brazil, Europe, Japan and the United States. For the first time, ten Laboratories operating or planning superconducting accelerators for heavy ions participated and shared their experience with the community proposing the use of superconducting accelerating sections for electron accelerators.

WORKSHOP: Radiofrequency superconductivity

International Nuclear Information System (INIS)

Anon.

1984-01-01

The Second Workshop on Radiofrequency Superconductivity was held at CERN from 23-27 July, four years after the first, organized at Karlsruhe. 35 invited talks were presented to the about 80 participants from Australia, Brazil, Europe, Japan and the United States. For the first time, ten Laboratories operating or planning superconducting accelerators for heavy ions participated and shared their experience with the community proposing the use of superconducting accelerating sections for electron accelerators

Process for producing clad superconductive materials

International Nuclear Information System (INIS)

Cass, R.B.; Ott, K.C.; Peterson, D.E.

1992-01-01

This patent describes a process for fabricating superconducting composite wire. It comprises placing a superconductive precursor admixture capable of undergoing self propagating combustion in stoichiometric amounts sufficient to form a superconductive product within an oxygen-porous metal tube; sealing one end of the tube; igniting the superconductive precursor admixture whereby the superconductive precursor admixture endburns along the length of the admixture; and cross-section reducing the tube at a rate substantially equal to the rate of burning of the superconductive precursor admixture and at a point substantially planar with the burnfront of the superconductive precursor mixture, whereby a clad superconductive product is formed in situ

Organic superconductivity

International Nuclear Information System (INIS)

Jerome, D.

1980-01-01

We present the experimental evidences for the existence of a superconducting state in the Quasi One Dimensional organic conductor (TMTSF) 2 PF 6 . Superconductivity occuring at 1 K under 12 kbar is characterized by a zero resistance diamagnetic state. The anistropy of the upper critical field of this type II superconductor is consistent with the band structure anistropy. We present evidences for the existence of large superconducting precursor effects giving rise to a dominant paraconductive contribution below 40 K. We also discuss the anomalously large pressure dependence of T sb(s), which drops to 0.19 K under 24 kbar in terms of the current theories. (author)

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

Superconducting Wind Turbine Generators

Directory of Open Access Journals (Sweden)

Yunying Pan

2016-08-01

Full Text Available Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends to introduce the basic concept and principle of superconductivity, and compare form traditional wind turbine to obtain superiority, then to summary three proposed machine concept.While superconductivity have difficulty  in modern technology and we also have proposed some challenges in achieving superconducting wind turbine finally.

Superconducting cermets

International Nuclear Information System (INIS)

Goyal, A.; Funkenbusch, P.D.; Chang, G.C.S.; Burns, S.J.

1988-01-01

Two distant classes of superconducting cermets can be distinguished, depending on whether or not a fully superconducting skeleton is established. Both types of cermets have been successfully fabricated using non-noble metals, with as high as 60wt% of the metal phase. The electrical, magnetic and mechanical behavior of these composites is discussed

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.

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)

Rf superconducting devices

International Nuclear Information System (INIS)

Hartwig, W.H.; Passow, C.

1975-01-01

Topics discussed include (1) the theory of superconductors in high-frequency fields (London surface impedance, anomalous normal surface resistance, pippard nonlocal theory, quantum mechanical model, superconductor parameters, quantum mechanical calculation techniques for the surface, impedance, and experimental verification of surface impedance theories); (2) residual resistance (separation of losses, magnetic field effects, surface resistance of imperfect and impure conductors, residual loss due to acoustic coupling, losses from nonideal surfaces, high magnetic field losses, field emission, and nonlinear effects); (3) design and performance of superconducting devices (design considerations, materials and fabrication techniques, measurement of performance, and frequency stability); (4) devices for particle acceleration and deflection (advantages and problems of using superconductors, accelerators for fast particles, accelerators for particles with slow velocities, beam optical devices separators, and applications and projects under way); (5) applications of low-power superconducting resonators (superconducting filters and tuners, oscillators and detectors, mixers and amplifiers, antennas and output tanks, superconducting resonators for materials research, and radiation detection with loaded superconducting resonators); and (6) transmission and delay lines

Superconducting Ferromagnetic Nanodiamond.

Science.gov (United States)

Zhang, Gufei; Samuely, Tomas; Xu, Zheng; Jochum, Johanna K; Volodin, Alexander; Zhou, Shengqiang; May, Paul W; Onufriienko, Oleksandr; Kačmarčík, Jozef; Steele, Julian A; Li, Jun; Vanacken, Johan; Vacík, Jiri; Szabó, Pavol; Yuan, Haifeng; Roeffaers, Maarten B J; Cerbu, Dorin; Samuely, Peter; Hofkens, Johan; Moshchalkov, Victor V

2017-06-27

Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the electronic entanglement between superconducting and ferromagnetic states in hydrogenated boron-doped nanodiamond films, which have a superconducting transition temperature T c ∼ 3 K and a Curie temperature T Curie > 400 K. In spite of the high T Curie , our nanodiamond films demonstrate a decrease in the temperature dependence of magnetization below 100 K, in correspondence to an increase in the temperature dependence of resistivity. These anomalous magnetic and electrical transport properties reveal the presence of an intriguing precursor phase, in which spin fluctuations intervene as a result of the interplay between the two antagonistic states. Furthermore, the observations of high-temperature ferromagnetism, giant positive magnetoresistance, and anomalous Hall effect bring attention to the potential applications of our superconducting ferromagnetic nanodiamond films in magnetoelectronics, spintronics, and magnetic field sensing.

Superconductivity and its application

International Nuclear Information System (INIS)

Spadoni, M.

1988-01-01

This paper, after a short introduction to superconductivity and to multifilamentary superconducting composites is aiming to review the state of the art and the future perspective of some of the applications of the superconducting materials. The main interest is focussed to large scale applications like, for istance, magnets for accelerators or fusion reactors, superconducting system for NMR thomography, etc. A short paragraph is dedicated to applications for high sensitivity instrumentation. The paper is then concluded by some considerations about the potentialities of the newly discovered high critical temperature materials

Analysis of superconducting microstrip resonator at various microwave power levels

International Nuclear Information System (INIS)

Srivastava, G.P.; Jacob, M.V.; Jayakumar, M.; Bhatnagar, P.K.; Kataria, N.D.

1997-01-01

The real and imaginary parts of the surface impedance of YBCO superconductors have been studied at different microwave power levels. Using the relations for the critical current density and the grain boundary resistance, a relation for calculating the power dependence of the surface resistance has been obtained. Also, a relation to find the resonant frequency of a superconducting microstrip resonator at various input power levels has been derived. Measurements have been carried out on various microstrip resonators to study the variation of surface resistance and resonant frequency at different rf power levels. The experimental results are in good agreement with theoretical results. copyright 1997 American Institute of Physics

WORKSHOPS: Radiofrequency superconductivity

International Nuclear Information System (INIS)

Anon.

1992-01-01

In the continual push towards higher energy particle beams, superconducting radiofrequency techniques now play a vital role, highlighted in the fifth workshop on radiofrequency superconductivity, held at DESY from 19 - 24 August 1991

WORKSHOPS: Radiofrequency superconductivity

Energy Technology Data Exchange (ETDEWEB)

Anon.

1992-01-15

In the continual push towards higher energy particle beams, superconducting radiofrequency techniques now play a vital role, highlighted in the fifth workshop on radiofrequency superconductivity, held at DESY from 19 - 24 August 1991.

'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)

Superconductivity

International Nuclear Information System (INIS)

Buller, L.; Carrillo, F.; Dietert, R.; Kotziapashis, A.

1989-01-01

Superconductors are materials which combine the property of zero electric resistance with the capability to exclude any adjacent magnetic field. This leads to many large scale applications such as the much publicized levitating train, generation of magnetic fields in MHD electric generators, and special medical diagnostic equipment. On a smaller-scale, superconductive materials could replace existing resistive connectors and decrease signal delays by reducing the RLC time constants. Thus, a computer could operate at much higher speeds, and consequently at lower power levels which would reduce the need for heat removal and allow closer spacing of circuitry. Although technical advances and proposed applications are constantly being published, it should be recognized that superconductivity is a slowly developing technology. It has taken scientists almost eighty years to learn what they now know about this material and its function. The present paper provides an overview of the historical development of superconductivity and describes some of the potential applications for this new technology as it pertains to the electronics industry

Grain refinement of AZ31 magnesium alloy by electromagnetic ...

Indian Academy of Sciences (India)

to improve the mechanical properties of magnesium alloys. (Lahaie and Bouchard 2001; ... superheating, carbon inoculation, addition of solute elements ... microscope (SEM) for morphological characterization. 3. Results and ... C. Figures 2(d), (e) and (f) show the ... It is widely appreciated that the microstructure of a casting.

Superheated water pretreatment combined with CO2 activation/regeneration of the exhausted activated carbon used in the treatment of industrial wastewater.

Science.gov (United States)

Xiao, Jin; Yu, Bailie; Zhong, Qifan; Yuan, Jie; Yao, Zhen; Zhang, Liuyun

2017-10-01

This paper examines a novel method of regenerating saturated activated carbon after adsorption of complex phenolic, polycyclic aromatic hydrocarbons with low energy consumption by using superheated water pretreatment combined with CO 2 activation. The effects of the temperature of the superheated water, liquid-solid ratio, soaking time, activation temperature, activation time, and CO 2 flow rate of regeneration and adsorption of coal-powdered activated carbon (CPAC) were studied. The results show that the adsorption capacity of iodine values on CPAC recovers to 102.25% of the fresh activated carbon, and the recovery rate is 79.8% under optimal experimental conditions. The adsorption model and adsorption kinetics of methylene blue on regenerated activated carbon (RAC) showed that the adsorption process was in accordance with the Langmuir model and the pseudo-second-order kinetics model. Furthermore, the internal diffusion process was the main controlling step. The surface properties, Brunauer-Emmett-Teller (BET) surface area, and pore size distribution were characterized by Fourier transform infrared spectroscopy (FT-IR) and BET, which show that the RAC possesses more oxygen-containing functional groups with a specific surface area of 763.39 m 2 g -1 and a total pore volume of 0.3039 cm 3 g -1 . Micropores account for 79.8% and mesopores account for 20.2%.

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.

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

The stability of high-Tc BSCCO/Ag superconducting microcomposites in water, some inorganic solutions and organic solvents

International Nuclear Information System (INIS)

Gao, W.; Chen, J.; Yang, C.O.; McNabb, D.; Sande, J. vander

1992-01-01

Bi(Pb)-Sr-Ca-Cu-O/Ag (BSCCO/Ag) superconducting microcomposites with zero-resistance temperatures from 102 to 108 K and critical current densities of ∝600 A/cm 2 at 77 K were produced by oxidation and annealling of metallic precursor alloys. The stabilities and degradation behavior of BSCCO/Ag specimens in various environments were studied by a combination of mass loss measurement, electrical transport measurement and microstructural observation. The environmental conditions used in the present work were moist air, distilled water, aqueous solutions of NaCl, NaOH and acetic acid, and organic solvents methanol and acetone. Although there is a general tendency toward a decrease in critical current density after a long exposure to most of the testing conditions, the specimens containing a high percent of Ag (≥70 wt.%) showed very little decrease in Tc and J c up to 200 days of exposure in moist air and distilled water, and up to 20 days in NaCl solution, methanol and acetone. It was found that the superconducting ''2223'' phase is stable in water, neutral solutions and the organic solvents, reacts very slowly with basic solutions, and dissolves rapidly in acidic solutions. Some non-superconducting Ca-rich oxides dissolve in water and neutral and basic solutions and therefore damage the connection of the superconducting grains in low-Ag containing specimens. The excellent stability of the BSCCO/Ag superconducting microcomposites containing high Ag provides an important advantage for their potential industrial application. (orig.)

Structural and superconducting properties of YBa2Cu3-xMxOy (M=Ag, Al

Directory of Open Access Journals (Sweden)

S Falahati

2009-08-01

Full Text Available   Samples of YBa2Cu3-xAgxOy with x=0, 0.1, 0.15, 0.2, 0.3 and samples of YBa2Cu3-xAlxOy with x=0, 0.01, 0.02, 0.03 and 0.045 are prepared by the sol-gel method. Structural and superconducting properties of samples are studied by electrical resistivity (R-T, X-ray diffraction (XRD and scanning electron microscopy (SEM. All the samples show transition to superconducting state and the transition temperatures of the samples increased with increasing Ag doping up to x=0.15. R-T measurements show a small decrease of TC (zero with increasing Al doping up to x=0.02, and followed by a faster decrease with increasing doping concentration. YBCO grains are better linked with increasing Ag doping. So, Ag has positive effects in superconducting properties of YBCO. The crystal structure of samples was refined by MAUD. These results show tha, Ag is substituted for Cu(1 in YBCO. According to these analysis, we introduce x=0.15 as the optimum value for doping concentration .

Growth orientation and superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films prepared by the low-fluorine sol-gel process

Energy Technology Data Exchange (ETDEWEB)

Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan, E-mail: leili813@gmail.co [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China)

2010-08-15

YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films were deposited on (100)-oriented LaAlO{sub 3} (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF{sub 2} and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)

Superconductivity basics and applications to magnets

CERN Document Server

Sharma, R G

2015-01-01

This book presents the basics and applications of superconducting magnets. It explains the phenomenon of superconductivity, theories of superconductivity, type II superconductors and high-temperature cuprate superconductors. The main focus of the book is on the application to superconducting magnets to accelerators and fusion reactors and other applications of superconducting magnets. The thermal and electromagnetic stability criteria of the conductors and the present status of the fabrication techniques for future magnet applications are addressed. The book is based on the long experience of the author in studying superconducting materials, building magnets and numerous lectures delivered to scholars. A researcher and graduate student will enjoy reading the book to learn various aspects of magnet applications of superconductivity. The book provides the knowledge in the field of applied superconductivity in a comprehensive way.

Large-Grain Superconducting Gun Cavity Testing Program Phase One Closing Report

Energy Technology Data Exchange (ETDEWEB)

Hammons, L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Bellavia, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Belomestnykh, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ben-Zvi, I. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cullen, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Dai, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Degen, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hahn, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Masi, L. [Brookhaven National Lab. (BNL), Upton, NY (United States); McIntyre, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schultheiss, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Seda, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kellerman, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tallerico, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Todd, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tuozzolo, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xu, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Than, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States)

2013-10-31

This report details the experimental configuration and RF testing results for the first phase of a large-grained niobium electron gun cavity testing program being conducted in the Small Vertical Testing Facility in the Collider-Accelerator Department. This testing is meant to explore multi-pacting in the cavity and shed light on the behavior of a counterpart cavity of identical geometry installed in the Energy Recovery LINAC being constructed in the Collider-Accelerator Department at Brookhaven National Laboratory. This test found that the Q of the large-grained cavity at 4 K reached ~6.5 × 10⁸ and at 2 K reached a value of ~6 × 10⁹. Both of these values are about a factor of 10 lower than would be expected for this type of cavity given the calculated surface resistance and the estimated geometry factor for this half-cell cavity. In addition, the cavity reached a peak voltage of 0.6 MV before there was sig-nificant decline in the Q value and a substantial increase in field emission. This relatively low volt-age, coupled with the low Q and considerable field emission suggest contamination of the cavity interior, possibly during experimental assembly. The results may also suggest that additional chemical etching of the interior surface of the cavity may be beneficial. Throughout the course of testing, various challenges arose including slow helium transfer to the cryostat and cable difficulties. These difficulties and others were eventually resolved, and the re-port discusses the operating experience of the experiment thus far and the plans for future work aimed at exploring the nature of multipacting with a copper cathode inserted into the cavity.

Effect of a high heat flux on the corrosion of 2 1/4 Cr-1 Mo steel in superheated steam

International Nuclear Information System (INIS)

Griess, J.C.; DeVan, J.H.; Maxwell, W.A.

1977-01-01

A series of corrosion tests was conducted to determine the effect of heat flux on the corrosion of 2 1 / 4 Cr-1 Mo steel in superheated steam. The tests were conducted with a constant heat flux of (126 kW/m 2 ) 40,000 Btu hr -1 ft -2 and surface temperatures varying from 950 to 1000 0 F (510 to 541 0 C) on each specimen. Specimens were exposed for varying lengths of time, ranging from 500 to 6000 hr. Essentially all the corrosion product oxide remained on the steel during the first 2000 hr, but after that time, exfoliation of the oxide began. The percentage of corrosion product oxide lost from the specimen increased with exposure time; about 33 percent was missing after 6000 hr. After an initial period of rapid corrosion, the average corrosion rate was constant at 1.8 mils/year (45 μm/year). In contrast, isothermal specimens exposed to superheated steam at 930 0 F (499 0 C) in the same test facility corroded at a decreasing rate throughout the test. Metallographic sections showed that, with heat transfer across the specimen-steam interface, both cracks and porosity developed in the oxide, even on short exposure, a face that was undoubtedly responsible for the early exfoliation of the oxide and the constant corrosion rate

Superconductivity application technologies. Superconducting quadrupole magnet and cooling system for KEK B factory

International Nuclear Information System (INIS)

Tsuchiya, Kiyosumi; Yamaguchi, Kiyoshi; Sakurabata, Hiroaki; Seido, Masahiro; Matsumoto, Kozo.

1997-01-01

At present in National Laboratory for High Energy Physics (KEK), the construction of B factory is in progress. By colliding 8 GeV electrons and 3.5 GeV positrons, this facility generates large amounts of B mesons and anti-B mesons, and performs the elementary particle experiment of high accuracy. It is the collision type accelerator of asymmetric two-ring type comprising 8 GeV and 3.5 GeV rings. In the field of high energy physics, superconductivity technology has been put to practical use. As the objects of superconductivity technology, there are dipole magnet for bending beam, quadrupole magnet for adjusting beam, large solenoid magnet used for detector and so on. Superconducting magnets which are indispensable for high energy, superconducting wire material suitable to accelerators, and the liquid helium cooling system for maintaining superconducting magnets at 4.4 K are reported. The technologies of metallic conductors and making their coils have advanced rapidly, and also cooling technology has advanced, accordingly, superconductivity technology has reached the stage of practical use perfectly. (K.I.)

Superconducting magnets and cryogenics for the steady state superconducting tokamak SST-1

International Nuclear Information System (INIS)

Saxena, Y.C.

2000-01-01

SST-1 is a steady state superconducting tokamak for studying the physics of the plasma processes in tokamak under steady state conditions and to learn technologies related to the steady state operation of the tokamak. SST-1 will have superconducting magnets made from NbTi based conductors operating at 4.5 K temperature. The design of the superconducting magnets and the cryogenic system of SST-1 tokamak are described. (author)

Vector superconductivity in cosmic strings

International Nuclear Information System (INIS)

Dvali, G.R.; Mahajan, S.M.

1992-03-01

We argue that in most realistic cases, the usual Witten-type bosonic superconductivity of the cosmic string is automatically (independent of the existence of superconducting currents) accompanied by the condensation of charged gauge vector bosons in the core giving rise to a new vector type superconductivity. The value of the charged vector condensate is related with the charged scalar expectation value, and vanishes only if the latter goes to zero. The mechanism for the proposed vector superconductivity, differing fundamentally from those in the literature, is delineated using the simplest realistic example of the two Higgs doublet standard model interacting with the extra cosmic string. It is shown that for a wide range of parameters, for which the string becomes scalarly superconducting, W boson condensates (the sources of vector superconductivity) are necessarily excited. (author). 14 refs

Foreword: Focus on Superconductivity in Semiconductors

Directory of Open Access Journals (Sweden)

Yoshihiko Takano

2008-01-01

Full Text Available Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm−3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008, which was held at the National Institute for Materials Science (NIMS, Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1.The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al are discussed, and In2O3 (Makise et al is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high

Status of RF superconductivity at Argonne

International Nuclear Information System (INIS)

Shepard, K.W.

1990-01-01

Development of a superconducting slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first superconducting heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerator System). The Physics Division at ANL has continued to develop superconducting RF technology for accelerating heavy-ions, with the result that the linac has been in an almost continuous process of upgrade and expansion. In 1987, the Engineering Physics Division at ANL began developing of superconducting RF components for the acceleration of high-brightness proton and deuterium beams. The two divisions collaborate in work on several applications of RF superconductivity, and also in work to develop the technology generally. The present report briefly describes major features of the superconducting heavy-ion linac (very-low-velocity superconducting linac, positive ion injector), proton accelerating structures (superconducting resonant cavities for acceleration of high-current proton and deuteron beams, RF properties of oxide superconductors), and future work. Both divisions expect to continue a variety of studies, frequently in collaboration, to advance the basic technology of RF superconductivity. (N.K.)

Unconventional superconductivity in heavy-fermion compounds

Energy Technology Data Exchange (ETDEWEB)

White, B.D. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States); Thompson, J.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maple, M.B., E-mail: mbmaple@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States)

2015-07-15

Highlights: • Quasiparticles in heavy-fermion compounds are much heavier than free electrons. • Superconductivity involves pairing of these massive quasiparticles. • Quasiparticle pairing mediated by magnetic or quadrupolar fluctuations. • We review the properties of superconductivity in heavy-fermion compounds. - Abstract: Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion compounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates and iron-based superconductors. We conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.

Superconducting magnet development in Japan

International Nuclear Information System (INIS)

Yasukochi, K.

1983-01-01

The present state of R and D works on the superconducting magnet and its applications in Japan are presented. On electrical rotating machines, 30 MVA superconducting synchronous rotary condenser (Mitsubishi and Fuji) and 50 MVA generator are under construction. Two ways of ship propulsion by superconducting magnets are developing. A superconducting magnetically levitated and linear motor propelled train ''MAGLEV'' was developed by the Japan National Railways (JNR). The superconducting magnet development for fusion is the most active field in Japan. The Cluster Test program has been demonstrated on a 10 T Nb 3 Sn coil and the first coil of Large Coil Task in IEA collaboration has been constructed and the domestic test was completed in JAERI. These works are for the development of toroidal coils of the next generation tokamak machine. R and D works on superconducting ohmic heating coil are in progress in JAERI and ETL. The latter group has constructed 3.8 MJ pulsed coil. A high ramp rate of changing field in pulsed magnet, 200 T/s, has been tested successfully. High Energy Physics Laboratory (KEK) are conducting active works. The superconducting μ meson channel and π meson channel have been constructed and are operating successfully. KEK has also a project of big accelerator named ''TRISTAN'', which is similar to ISABELLE project of BNL. Superconducting synchrotron magnets are developed for this project. The development of superconducting three thin wall solenoid has been started. One of them, CDF, is progressing under USA-Japan collaboration

Superconducting joint of Bi-2223/Ag superconducting tapes by diffusion bonding

International Nuclear Information System (INIS)

Guo Wei; Zou Guisheng; Wu Aiping; Wang Yanjun; Bai Hailin; Ren Jialie

2009-01-01

61-Filaments Bi-2223/Ag superconducting tapes have been joined by diffusion bonding. The critical currents (I C s) of the joints are obtained by using standard four probe method under no magnetic field in the liquid nitrogen. The microstructures of the joints are evaluated by the electron microscope in electron backscatter diffraction mode and the phase compositions of the superconducting cores of the joint and the original tape are determined by X-ray diffraction (XRD). The results show diffusion bonding is effective bonding technique for HTS tapes, and the bonding time is reduced greatly from hundreds of hours to a few hours, and the bonding pressure also changes from 140-4000 MPa to 3 MPa. Furthermore, the diffusion bonding joints sustain superconducting properties, and the critical current ratios (CCR O ) of the joints are in the range of 35%-80%. Microstructures of the typical joint display a good bonding and some defects existed in traditional method are avoided. XRD results show that the phase compositions of the superconducting cores have no obvious changes before and after diffusion bonding, which offers physical and material bases for high superconducting property of the joints.

Superconductivity in the 1990's

International Nuclear Information System (INIS)

Stekly, Z.J.J.

1990-01-01

Superconducting magnets, coils or windings are the basis for a range of major applications in the energy area such as energy storage in superconducting coils, magnets for fusion research, and rotating machinery. Other major applications of superconductivity include high energy physics where 1000 superconducting magnets are operated continuously in the Tevatron at Fermilab in Illinois, over 12,000 superconducting magnets will be required for the superconducting Super Collider being build near Dallas. The largest commercial application of superconductors is in magnets for magnetic resonance imaging (MRI) - a new medical diagnostic imaging technique with about 2,000 systems installed worldwide. These form a sizable technology base on which to evaluate and push forward applications such as magneto hydrodynamic propulsion of seagoing vessels. The attractiveness of which depends ultimately on the characteristics of the superconducting magnet. The magnet itself is a combination of several technology areas - the conductors, magnetics, structures and cryogenics. This paper reviews state-of-the-art in each of the technology areas as they relate to superconductors

Superconductivity in doped Dirac semimetals

Science.gov (United States)

Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi

2016-07-01

We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.

Superconductivity: materials and applications

International Nuclear Information System (INIS)

Duchateau, J.L.; Kircher, F.; Leveque, J.; Tixador, P.

2008-01-01

This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

Superconductivity in power engineering

International Nuclear Information System (INIS)

1989-01-01

This proceedings volume presents 24 conference papers and 15 posters dealing with the following aspects: 1) Principles and elementary aspects of high-temperature superconductivity (3 plenary lectures); 2) Preparation, properties and materials requirements of metallic or oxide superconductors (critical current behaviour, soldered joints, structural studies); 3) Magnet technology (large magnets for thermonuclear fusion devices; magnets for particle accelerators and medical devices); 4) Magnetic levitation and superconductivity; 5) Cryogenics; 6) Energy storage systems using superconducting coils (SMES); 7) Superconducting power transmission cables, switches, transformers, and generator systems for power plant; 8) Supporting activities, industrial aspects, patents. There are thirty-eight records in the ENERGY database relating to individual conference papers. (MM) [de

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

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

Science.gov (United States)

Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

2016-06-01

Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0-values. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100-150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0-value of 2 × 1010 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

On the possibility of laser diagnostics of anisotropically superheated electrons in magnetic fusion systems

International Nuclear Information System (INIS)

Kukushkin, A.B.

1990-01-01

The anisotropically superheated electrons (ASE) are known to be generated by a resonance interaction of high-frequency electromagnetic waves with electron plasma. Under definite conditions the ASE energy may essentially exceed (by the order of magnitude or even more) thermal energies of background electron plasma, the ASE distribution in pitch-angle being concentrated around definite directions. This situation is typical for, e.g. electron cyclotron heating of magnetic mirror plasmas (generation of 'sloshing' electrons) and for current drive in tokamaks by means of lower-hybrid or, sometimes, electron cyclotron waves. In this work, an analysis of the possibility of the ASE laser diagnostics is based on the calculations of Thomson scattering of laser radiation by plasma electrons. The model electron velocity distribution functions, which provide qualitative description of the ASE peculiar features, were used in calculations. (author) 4 refs., 1 fig

The determination of superheated layer thickness for boiling incipience in a vertical thermosiphon reboiler

International Nuclear Information System (INIS)

Shamsuzzoha, M.; Kamil, M.; Alam, S.S.

2003-01-01

The characteristics of the incipient boiling for vertical thermosiphon reboiler were examined in detail. At the onset of boiling, liquid film adjacent to the heating surface, the super-heated layers thickness δ * , must attain a threshold value so that the critical bubble nuclei with radius r c can further grow to the point of detachment. Thus, the value of δ * /r c is of primary importance for the superheat calculation. In the present study a semi-empirical equation was proposed for the incipient point of boiling including the effect of submergence. The results predicted from theoretical analysis are consistent with the experimental data available in the literature. All the data for fluids namely, distilled water, toluene and ethylene glycol having different thermophysical properties were correlated with a unified correlation having mean absolute deviation 12.73%. (author)

Superconducting magnets for a muon collider

International Nuclear Information System (INIS)

Green, M.A.

1996-01-01

The existence of a muon collider will be dependent on the use of superconducting magnets. Superconducting magnets for the μ - μ + collider will be found in the following locations: the π - π + capture system, the muon phase rotation system, the muon cooling system, the recirculating acceleration system, the collider ring, and the collider detector system. This report describes superconducting magnets for each of these sections except the detector. In addition to superconducting magnets, superconducting RF cavities will be found in the recirculating accelerator sections and the collider ring. The use of superconducting magnets is dictated by the need for high magnetic fields in order to reduce the length of various machine components. The performance of all of the superconducting magnets will be affected the energy deposited from muon decay products. (orig.)

Superconducting wind turbine generators

DEFF Research Database (Denmark)

Abrahamsen, Asger Bech; Mijatovic, Nenad; Seiler, Eugen

2010-01-01

, the main challenge of the superconducting direct drive technology is to prove that the reliability is superior to the alternative drive trains based on gearboxes or permanent magnets. A strategy of successive testing of superconducting direct drive trains in real wind turbines of 10 kW, 100 kW, 1 MW and 10......We have examined the potential of 10 MW superconducting direct drive generators to enter the European offshore wind power market and estimated that the production of about 1200 superconducting turbines until 2030 would correspond to 10% of the EU offshore market. The expected properties of future...... offshore turbines of 8 and 10 MW have been determined from an up-scaling of an existing 5 MW turbine and the necessary properties of the superconducting drive train are discussed. We have found that the absence of the gear box is the main benefit and the reduced weight and size is secondary. However...

Three-terminal superconducting devices

International Nuclear Information System (INIS)

Gallagher, W.J.

1985-01-01

The transistor has a number of properties that make it so useful. The authors discuss these and the additional properties a transistor would need to have for high performance applications at temperatures where superconductivity could contribute advantages to system-level performance. These properties then serve as criteria by which to evaluate three-terminal devices that have been proposed for applications at superconducting temperatures. FETs can retain their transistor properties at low temperatures, but their power consumption is too large for high-speed, high-density cryogenic applications. They discuss in detail why demonstrated superconducting devices with three terminals -Josephson effect based devices, injection controlled weak links, and stacked tunnel junction devices such as the superconducting transistor proposed by K. Gray and the quiteron -- each fail to have true transistor-like properties. They conclude that the potentially very rewarding search for a transistor compatible with superconductivity in high performance applications must be in new directions

Korea's developmental program for superconductivity

Science.gov (United States)

Hong, Gye-Won; Won, Dong-Yeon; Kuk, Il-Hyun; Park, Jong-Chul

1995-04-01

Superconductivity research in Korea was firstly carried out in the late 70's by a research group in Seoul National University (SNU), who fabricated a small scale superconducting magnetic energy storage system under the financial support from Korea Electric Power Company (KEPCO). But a few researchers were involved in superconductivity research until the oxide high Tc superconductor was discovered by Bednorz and Mueller. After the discovery of YBaCuO superconductor operating above the boiling point of liquid nitrogen (77 K)(exp 2), Korean Ministry of Science and Technology (MOST) sponsored a special fund for the high Tc superconductivity research to universities and national research institutes by recognizing its importance. Scientists engaged in this project organized 'High Temperature Superconductivity Research Association (HITSRA)' for effective conducting of research. Its major functions are to coordinate research activities on high Tc superconductivity and organize the workshop for active exchange of information. During last seven years the major superconductivity research has been carried out through the coordination of HITSRA. The major parts of the Korea's superconductivity research program were related to high temperature superconductor and only a few groups were carrying out research on conventional superconductor technology, and Korea Atomic Energy Research Institute (KAERI) and Korea Electrotechnology Research Institute (KERI) have led this research. In this talk, the current status and future plans of superconductivity research in Korea will be reviewed based on the results presented in interim meeting of HITSRA, April 1-2, 1994. Taejeon, as well as the research activity of KAERI.

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.)

Superconductivity at the industrial scale

International Nuclear Information System (INIS)

Tixador, P.; Lebrun, Ph.

2011-01-01

The discovery of superconductivity is 100 years old but theoretical works are still necessary: the BCS theory does not apply to the new families of high temperature superconducting materials discovered after 1986. In 2001 it was discovered that MgB 2 is superconducting at 39 K, this critical temperature is not the highest but MgB 2 is easy to produce and cheap. Today's highest critical temperature under atmospheric pressure is that of the HgTlBaCaCuO compound: 138 K. The complexity and the cost of cryogenic systems restrain the applications of superconductivity. The author reviews the applications of superconducting in medical imaging, particle detectors, and in the safety systems of power networks. (A.C.)

Neutron detection using a planar array of superheated superconductors

International Nuclear Information System (INIS)

Meagher, G.

1996-01-01

A new thermal neutron detector consisting of an indium/mylar PASS array with a filler of boron powder has been tested successfully. A boron nucleus captures a neutron and the α-particle emitted in this reaction nucleates the transition to the normal state in a neighbouring grain. A PASS with grain radius r=12 μm showed very low response to irradiation by 835 keV γ-rays. The same PASS responded to α-particles with high efficiency, and thermal neutrons were detected with good efficiency and very low background. Thermal neutrons were also counted with an R=25 μm PASS. The use of large granules will allow spatial resolution to a single grain to be obtained and a read-out based on conventional inductive coupling and fast electronics to be utilized. (orig.)

Process of producing superconducting bar magnets

International Nuclear Information System (INIS)

Wilson, M.A.

1988-01-01

A method of forming a magnet having an established magnetic field is described comprising; (1) establishing a magnetic field of the desired extent and shape; (2) providing a superconducting material of desired shape; (3) positioning the material of (2) in field (1) while at a temperature above the critical temperature of the superconducting material so as to apply a magnetic field on the superconducting material; (4) cooling the superconducting material while in magnetic field (1) to below the critical temperature of the superconducting material; (5) removing the superconducting material from the magnetic field while in the supercooled condition; and (6) maintaining the material at or below the critical temperature

Modification of Oil Palm Mesocarp Fiber Characteristics Using Superheated Steam Treatment

Directory of Open Access Journals (Sweden)

Subbian Karuppuchamy

2013-07-01

Full Text Available In this study, oil palm mesocarp fiber (OPMF was treated with superheated steam (SHS in order to modify its characteristics for biocomposite applications. Treatment was conducted at temperatures 190–230 °C for 1, 2 and 3 h. SHS-treated OPMF was evaluated for its chemical composition, thermal stability, morphology and crystallinity. OPMF treated at 230 °C exhibited lower hemicellulose content (9% compared to the untreated OPMF (33%. Improved thermal stability of OPMF was found after the SHS treatment. Moreover, SEM and ICP analyses of SHS-treated OPMF showed that silica bodies were removed from OPMF after the SHS treatment. XRD results exhibited that OPMF crystallinity increased after SHS treatment, indicating tougher fiber properties. Hemicellulose removal makes the fiber surface more hydrophobic, whereby silica removal increases the surface roughness of the fiber. Overall, the results obtained herewith suggested that SHS is an effective treatment method for surface modification and subsequently improving the characteristics of the natural fiber. Most importantly, the use of novel, eco-friendly SHS may contribute to the green and sustainable treatment for surface modification of natural fiber.

Superconducting cavities developments efforts at RRCAT

International Nuclear Information System (INIS)

Puntambekar, A.; Bagre, M.; Dwivedi, J.; Shrivastava, P.; Mundra, G.; Joshi, S.C.; Potukuchi, P.N.

2011-01-01

Superconducting RE cavities are the work-horse for many existing and proposed linear accelerators. Raja Ramanna Centre for Advanced Technology (RRCAT) has initiated a comprehensive R and D program for development of Superconducting RF cavities suitable for high energy accelerator application like SNS and ADS. For the initial phase of technology demonstration several prototype 1.3 GHz single cell-cavities have been developed. The work began with development of prototype single cell cavities in aluminum and copper. This helped in development of cavity manufacturing process, proving various tooling and learning on various mechanical and RF qualification processes. The parts manufacturing was done at RRCAT and Electron beam welding was carried out at Indian industry. These cavities further served during commissioning trials for various cavity processing infrastructure being developed at RRCAT and are also a potential candidate for Niobium thin film deposition R and D. Based on the above experience, few single cell cavities were developed in fine grain niobium. The critical technology of forming and machining of niobium and the intermediate RF qualification were developed at RRCAT. The EB welding of bulk niobium cavities was carried out in collaboration with IUAC, New Delhi at their facility. As a next logical step efforts are now on for development of multicell cavities. The prototype dumbbells and end group made of aluminium, comprising of RF and HOM couplers ports have also been developed, with their LB welding done at Indian industry. In this paper we shall present the development efforts towards manufacturing of 1.3 GHz single cell cavities and their initial processing and qualification. (author)

Superconductivity and its devices

International Nuclear Information System (INIS)

Forbes, D.S.

1981-01-01

Among the more important developments that are discussed are cryotrons, superconducting motors and generators, and high-field magnets. Cryotrons will create faster and more economical computer systems. Superconducting motors and generators will cost much less to build than conventional electric generators and cut fuel consumption. Moreover, high-field magnets are being used to confine plasma in connection with nuclear fusion. Superconductors have a vital role to play in all of these developments. Most importantly, though, are the magnetic properties of superconductivity. Superconducting magnets are an integral part of nuclear fusion. In addition, high-field magnets are necessary in the use of accelerators, which are needed to study the interactions between elementary particles

Superconductivity

CERN Document Server

Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan

2014-01-01

Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.

The effect of nano-size ZrO2 powder addition on the microstructure and superconducting properties of single-domain Y-Ba-Cu-O bulk superconductors

International Nuclear Information System (INIS)

Iida, K; Babu, N H; Reddy, E S; Shi, Y-H; Cardwell, D A

2005-01-01

The effect of nano-size ZrO 2 powder addition on the microstructure and superconducting properties of Y-Ba-Cu-O single grain bulk superconductors has been investigated. Significant pushing phenomena of Y 2 BaCuO 5 (Y-211) particles, particularly in the c growth sector, were observed even with a small amount of ZrO 2 added to the precursor powder. An increase in Y-211 particle pushing was observed with increasing ZrO 2 content, leading to an inhomogeneous bulk microstructure. In addition, a growth cycle consisting of a Y-211 free layer-porous narrow layer-Y-211 high concentration layer was observed for samples prepared with 0.25 wt% ZrO 2 in both the a and c growth sectors. The extent of the growth of single grain Y-Ba-Cu-O (YBCO) decreased with increasing ZrO 2 content due to increased pushing of Y-211 particles towards molten liquid. The superconducting transition temperature, T c , of the ZrO 2 containing YBCO samples was sharp but depressed slightly (by up to 1 K) compared with an undoped YBCO grain, indicating a relative insensitivity of T c to ZrO 2 content. Finally, the sensitivity of critical current density, J c , to applied magnetic field in large grain bulk YBCO containing ZrO 2 was observed to depend critically on position due to the inhomogeneous sample microstructure

Effect of superconducting transition on microcreep of high-TC ceramics

International Nuclear Information System (INIS)

Soldatov, V.P.; Natsik, V.D.; Chajkovskaya, N.M.

1991-01-01

Influence of N-S and S-N transition on microplastic deformation kinetics of YBa 2 Cu 3 O 7-δ ceramic samples by there deformation in liquid nitrogen under microscreep conditions is studied. Superconductivity disruption in the sample was achieved by critical value currents. It is shown, that N-S transition increases creep rate,whereas S-N transition slows it down. Microplastic deformation rate by sample state change may very by two-eight times. Influence of heat expansion on creep kinetics as probable associated effect is analyzed. Assumption is expressed, that stimulated transition effect on microplastic deformation of ceramic samples is related to change of their electron state in the area of Josephson contacts between grains

Superconducting elliptical cavities

CERN Document Server

Sekutowicz, J K

2011-01-01

We give a brief overview of the history, state of the art, and future for elliptical superconducting cavities. Principles of the cell shape optimization, criteria for multi-cell structures design, HOM damping schemes and other features are discussed along with examples of superconducting structures for various applications.

Unconventional superconductivity in honeycomb lattice

Directory of Open Access Journals (Sweden)

P Sahebsara

2013-03-01

Full Text Available   ‎ The possibility of symmetrical s-wave superconductivity in the honeycomb lattice is studied within a strongly correlated regime, using the Hubbard model. The superconducting order parameter is defined by introducing the Green function, which is obtained by calculating the density of the electrons ‎ . In this study showed that the superconducting order parameter appears in doping interval between 0 and 0.5, and x=0.25 is the optimum doping for the s-wave superconductivity in honeycomb lattice.

2017 Gordon Conference on Superconductivity

Energy Technology Data Exchange (ETDEWEB)

Chubukov, Andrey [Univ. of Minnesota, Twin Cities, MN (United States)

2017-11-14

The DOE award was for a 2017 Gordon Research conference on Superconductivity (GRC). The objective of GRC is to interchange the information about the latest theoretical and experimental developments in the area of superconductivity and to select most perspective directions for future research in this area.The goal of the Gordon Conference on Superconductivity is to present and discuss the latest results in the field of modern superconductivity, discuss new ideas and new directions of research in the area. It is a long-standing tradition of the Gordon conference on Superconductivity that the vast majority of participants are junior scientists. Funding for the conference would primarily be used to support junior researchers, particularly from under-represented groups. We had more 10 female speakers, some of them junior researchers, and some funding was used to support these speakers. The conference was held together with Gordon Research Seminar on Superconductivity, where almost all speakers and participants were junior scientists.

Superconductivity and their applications

OpenAIRE

Roque, António; Sousa, Duarte M.; Fernão Pires, Vítor; Margato, Elmano

2017-01-01

Trabalho apresentado em International Conference on Renewable Energies and Power Quality (ICREPQ’17), 4 a 6 de Abril de 2017, Málaga, Espanha The research in the field of superconductivity has led to the synthesis of superconducting materials with features that allow you to expand the applicability of this kind of materials. Among the superconducting materials characteristics, the critical temperature of the superconductor is framing the range and type of industrial applications that can b...

Superconducting wind turbine generators

International Nuclear Information System (INIS)

Abrahamsen, A B; Seiler, E; Zirngibl, T; Andersen, N H; Mijatovic, N; Traeholt, C; Pedersen, N F; Oestergaard, J; Noergaard, P B

2010-01-01

We have examined the potential of 10 MW superconducting direct drive generators to enter the European offshore wind power market and estimated that the production of about 1200 superconducting turbines until 2030 would correspond to 10% of the EU offshore market. The expected properties of future offshore turbines of 8 and 10 MW have been determined from an up-scaling of an existing 5 MW turbine and the necessary properties of the superconducting drive train are discussed. We have found that the absence of the gear box is the main benefit and the reduced weight and size is secondary. However, the main challenge of the superconducting direct drive technology is to prove that the reliability is superior to the alternative drive trains based on gearboxes or permanent magnets. A strategy of successive testing of superconducting direct drive trains in real wind turbines of 10 kW, 100 kW, 1 MW and 10 MW is suggested to secure the accumulation of reliability experience. Finally, the quantities of high temperature superconducting tape needed for a 10 kW and an extreme high field 10 MW generator are found to be 7.5 km and 1500 km, respectively. A more realistic estimate is 200-300 km of tape per 10 MW generator and it is concluded that the present production capacity of coated conductors must be increased by a factor of 36 by 2020, resulting in a ten times lower price of the tape in order to reach a realistic price level for the superconducting drive train.

Project in fiscal 1989 for research and development of basic technologies in next generation industries. Research and development of superconducting materials and superconducting elements (Achievement report on forecast and research of superconducting element technology); 1989 nendo chodendo soshi gijutsu yosoku kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1990-03-01

Investigations were performed on the progress in elementary technologies common to the superconducting element technologies. This paper summarizes the achievements therein. For the most basic and important thin film technologies among the common elementary technologies, number of researches has increased as it entered in this fiscal year on the CVD process and the atomic layer control, resulting in the progress in film quality improvement and temperature reduction. With regard to the sputtering process and vacuum deposition process, findings were obtained on mechanisms and solutions for the reverse sputtering due to negative ions and oxygen activation which have been the issues. For electronic devices using high-temperature superconduction, the bridge type or tunnel type Josephson elements may be conceived. Elements for the SQUID magnetic flux meter have become to derive relatively high output by means of grain boundary bonding, suggesting a possibility of practical application in the near future. Tunnel bonding may be conceived for the switching elements, but the one operating at elevated temperatures has not been obtained. However, progress can be discovered in the proximity effects of high-temperature superconductors and silver, and the Josephson junction between high-temperature superconductors and metallic superconductors. (NEDO)

Superconductivity from magnetic elements under high pressure

International Nuclear Information System (INIS)

Shimizu, Katsuya; Amaya, Kiichi; Suzuki, Naoshi; Onuki, Yoshichika

2006-01-01

Can we expect the appearance of superconductivity from magnetic elements? In general, superconductivity occurs in nonmagnetic metal at low temperature and magnetic impurities destroy superconductivity; magnetism and superconductivity are as incompatible as oil and water. Here, we present our experimental example of superconducting elements, iron and oxygen. They are magnetic at ambient pressure, however, they become nonmagnetic under high pressure, then superconductor at low temperature. What is the driving force of the superconductivity? Our understanding in the early stages was a simple scenario that the superconductive state was obtained as a consequence of an emergence of the nonmagnetic states. In both cases, we may consider another scenario for the appearance of superconductivity; the magnetic fluctuation mechanism in the same way as unconventional superconductors

Analysis of mechanical characteristics of superconducting field coil for 17 MW class high temperature superconducting synchronous motor

International Nuclear Information System (INIS)

Kim, J. H.; Park, S. I.; Im, S. H.; Kim, H. M.

2013-01-01

Superconducting field coils using a high-temperature superconducting (HTS) wires with high current density generate high magnetic field of 2 to 5 [T] and electromagnetic force (Lorentz force) acting on the superconducting field coils also become a very strong from the point of view of a mechanical characteristics. Because mechanical stress caused by these powerful electromagnetic force is one of the factors which worsens the critical current performance and structural characteristics of HTS wire, the mechanical stress analysis should be performed when designing the superconducting field coils. In this paper, as part of structural design of superconducting field coils for 17 MW class superconducting ship propulsion motor, mechanical stress acting on the superconducting field coils was analyzed and structural safety was also determined by the coupling analysis system that is consists of commercial electromagnetic field analysis program and structural analysis program.

Superconducted tour

Energy Technology Data Exchange (ETDEWEB)

Anon.

1988-09-15

Superconductivity - the dramatic drop in electrical resistance in certain materials at very low temperatures - has grown rapidly in importance over the past two or three decades to become a key technology for high energy particle accelerators. It was in this setting that a hundred students and 15 lecturers met in Hamburg in June for a week's course on superconductivity in particle accelerators, organized by the CERN Accelerator School and the nearby DESY Laboratory.

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

Introduction to superconductivity

CERN Document Server

Darriulat, Pierre

1998-01-01

The lecture series will address physicists, such as particle and nuclear physicists, familiar with non-relativistic quantum mechanics but not with solid state physics. The aim of this introduction to low temperature superconductivity is to give sufficient bases to the student for him/her to be able to access the scientific literature on this field. The five lectures will cover the following topics : 1. Normal metals, free electron gas, chambers equation. 2. Cooper pairs, the BCS ground state, quasi particle excitations. 3. DC superconductivity, Meissner state, dirty superconductors.4. Self consistent approach, Ginsburg Landau equations, Abrikosov fluxon lattice. 5. Josephson effects, high temperature superconductivity.

The development of superconducting equipment

CERN Document Server

Ueda, T; Hiue, H

2003-01-01

Fuji Electric has been developing various types of superconducting equipment for over a quarter of a century. This paper describes the development results achieved for superconducting equipment and especially focuses on large-capacity current leads and superconducting transmission systems, the development of which is being promoted for application to the field of nuclear fusion. High temperature superconductor (HTS) is becoming the mainstream in the field of superconductivity, and the HTS floating coil and conduction-cooled HTS transformed are also introduced as recent developments for devices that utilize this technology. (author)

Materials and mechanisms of hole superconductivity

Energy Technology Data Exchange (ETDEWEB)

Hirsch, J.E., E-mail: jhirsch@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States)

2012-01-15

We study the applicability of the model of hole superconductivity to materials. Both conventional and unconventional materials are considered. Many different classes of materials are discussed. The theory is found suitable to describe all of them. No other theory of superconductivity can describe all these classes of materials. The theory of hole superconductivity proposes that there is a single mechanism of superconductivity that applies to all superconducting materials. This paper discusses several material families where superconductivity occurs and how they can be understood within this theory. Materials discussed include the elements, transition metal alloys, high T{sub c} cuprates both hole-doped and electron-doped, MgB{sub 2}, iron pnictides and iron chalcogenides, doped semiconductors, and elements under high pressure.

Molybdenum-rhenium superconducting suspended nanostructures

Energy Technology Data Exchange (ETDEWEB)

Aziz, Mohsin; Christopher Hudson, David; Russo, Saverio [Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)

2014-06-09

Suspended superconducting nanostructures of MoRe 50%/50% by weight are fabricated employing commonly used fabrication steps in micro- and nano-meter scale devices followed by wet-etching with Hydro-fluoric acid of a SiO{sub 2} sacrificial layer. Suspended superconducting channels as narrow as 50 nm and length 3 μm have a critical temperature of ≈6.5 K, which can increase by 0.5 K upon annealing at 400 °C. A detailed study of the dependence of the superconducting critical current and critical temperature upon annealing and in devices with different channel widths reveals that desorption of contaminants is responsible for the improved superconducting properties. These findings pave the way for the development of superconducting electromechanical devices using standard fabrication techniques.

Superconducting RF activities at Cornell University

International Nuclear Information System (INIS)

Kirchgessner, J.; Moffat, D.; Padamsee, H.; Rubin, D.; Sears, J.; Shu, Q.S.

1990-01-01

This paper outlines the RF superconductivity research and development work that has taken place at Cornell Laboratory of Nuclear Studies over the past years. The work that has been performed since the last RF superconductivity workshop is emphasized together with a discussion of the direction of future efforts. Past work is summarized first, focusing on research and development activities in the area of RF superconductivity. Superconducting TeV linear collider is then discussed focusing on the application of superconducting RF to a future TeV linear collider. Linear collider structure development is then described centering on the development of a simpler (thereby cheaper) structure for a TeV linear collider. B-factory with superconducting RF is outlined focusing on the formulation of a conceptual design for a B-factory. B-factory structure development is discussed in relation to the advancement in the capability of SC cavities to carry beam currents of several amperes necessary for a high luminosity storage ring. High gradients are discussed as the key to the realization of a high energy superconducting linac or a superconducting RF B-factory. (N.K.)

Frontiers in Superconducting Materials

CERN Document Server

Narlikar, Anant V

2005-01-01

Frontiers in Superconducting Materials gives a state-of-the-art report of the most important topics of the current research in superconductive materials and related phenomena. It comprises 30 chapters written by renowned international experts in the field. It is of central interest to researchers and specialists in Physics and Materials Science, both in academic and industrial research, as well as advanced students. It also addresses electronic and electrical engineers. Even non-specialists interested in superconductivity might find some useful answers.

Superconductivity in the actinides

International Nuclear Information System (INIS)

Smith, J.L.; Lawson, A.C.

1985-01-01

The trends in the occurrence of superconductivity in actinide materials are discussed. Most of them seem to show simple transition metal behavior. However, the superconductivity of americium proves that the f electrons are localized in that element and that ''actinides'' is the correct name for this row of elements. Recently the superconductivity of UBe 13 and UPt 3 has been shown to be extremely unusual, and these compounds fall in the new class of compounds now known as heavy fermion materials

Superconducting rotating machines

International Nuclear Information System (INIS)

Smith, J.L. Jr.; Kirtley, J.L. Jr.; Thullen, P.

1975-01-01

The opportunities and limitations of the applications of superconductors in rotating electric machines are given. The relevant properties of superconductors and the fundamental requirements for rotating electric machines are discussed. The current state-of-the-art of superconducting machines is reviewed. Key problems, future developments and the long range potential of superconducting machines are assessed

Status of superconducting power transformer development

Energy Technology Data Exchange (ETDEWEB)

Johnson, R.C.; McConnell, B.W.; Mehta, S.P. [and others

1996-03-01

Development of the superconducting transformer is arguably the most difficult of the ac power applications of superconductivity - this is because of the need for very low ac losses, adequate fault and surge performance, and the rigors of the application environment. This paper briefly summarizes the history of superconducting transformer projects, reviews the key issues for superconducting transformers, and examines the status of HTS transformer development. Both 630-kVA, three-phase and 1-MVA single phase demonstration units are expected to operate in late 1996. Both efforts will further progress toward the development of economical and performance competitive superconducting transformers.

Superconductive analogue of spin glasses

International Nuclear Information System (INIS)

Feigel'man, M.; Ioffe, L.; Vinokur, V.; Larkin, A.

1987-07-01

The properties of granular superconductors in magnetic fields, namely the existence of a new superconductive state analogue of the low-temperature superconductive state in spin glasses are discussed in the frame of the infinite-range model and the finite-range models. Experiments for elucidation of spin-glass superconductive state in real systems are suggested. 30 refs

Quenches in large superconducting magnets

International Nuclear Information System (INIS)

Eberhard, P.H.; Alston-Garnjost, M.; Green, M.A.; Lecomte, P.; Smits, R.G.; Taylor, J.D.; Vuillemin, V.

1977-08-01

The development of large high current density superconducting magnets requires an understanding of the quench process by which the magnet goes normal. A theory which describes the quench process in large superconducting magnets is presented and compared with experimental measurements. The use of a quench theory to improve the design of large high current density superconducting magnets is discussed

Development of superconducting wind turbine generators

DEFF Research Database (Denmark)

Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

2013-01-01

In this paper, the commercial activities in the field of superconducting machines, particularly superconducting wind turbine generators, are reviewed and presented. Superconducting generators have the potential to provide a compact and light weight drive train at high torques and slow rotational...... speeds, because high magnetic fields can be produced by coils with very little loss. Three different superconducting wind turbine generator topologies have been proposed by three different companies. One is based on low temperature superconductors; one is based on high temperature superconductors......; and one is a fully superconducting generator based on MgB2. It is concluded that there is large commercial interest in superconducting machines, with an increasing patenting activity. Such generators are, however, not without their challenges. The superconductors have to be cooled down to somewhere...

Development of Superconducting Wind Turbine Generators

DEFF Research Database (Denmark)

Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

2012-01-01

In this paper the commercial activities in the field of superconducting machines, particularly superconducting wind turbine generators, are reviewed and presented. Superconducting generators have the potential to provide a compact and light weight drive train at high torques and slow rotational...... speeds, because high magnetic fields can be produced by coils with very little loss. Three different superconducting wind turbine generator topologies have been proposed by three different companies. One is based on low temperature superconductors (LTS); one is based on high temperature superconductors...... (HTS); and one is a fully superconducting generator based on MgB2. It is concluded that there is large commercial interest in superconducting machines, with an increasing patenting activity. Such generators are however not without their challenges. The superconductors have to be cooled down...

Superconducting fault current-limiter with variable shunt impedance

Science.gov (United States)

Llambes, Juan Carlos H; Xiong, Xuming

2013-11-19

A superconducting fault current-limiter is provided, including a superconducting element configured to resistively or inductively limit a fault current, and one or more variable-impedance shunts electrically coupled in parallel with the superconducting element. The variable-impedance shunt(s) is configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a normal resistive state of the superconducting element. The superconducting element transitions from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto, the variable-impedance shunt(s) transitions from the first to the second impedance. The second impedance of the variable-impedance shunt(s) is a lower impedance than the first impedance, which facilitates current flow through the variable-impedance shunt(s) during a recovery transition of the superconducting element from the normal resistive state to the superconducting state, and thus, facilitates recovery of the superconducting element under load.

Superconducting magnetic energy storage and superconducting self-supplied electromagnetic launcher

Science.gov (United States)

Ciceron, Jérémie; Badel, Arnaud; Tixador, Pascal

2017-10-01

Superconductors can be used to build energy storage systems called Superconducting Magnetic Energy Storage (SMES), which are promising as inductive pulse power source and suitable for powering electromagnetic launchers. The second generation of high critical temperature superconductors is called coated conductors or REBCO (Rare Earth Barium Copper Oxide) tapes. Their current carrying capability in high magnetic field and their thermal stability are expanding the SMES application field. The BOSSE (Bobine Supraconductrice pour le Stockage d'Energie) project aims to develop and to master the use of these superconducting tapes through two prototypes. The first one is a SMES with high energy density. Thanks to the performances of REBCO tapes, the volume energy and specific energy of existing SMES systems can be surpassed. A study has been undertaken to make the best use of the REBCO tapes and to determine the most adapted topology in order to reach our objective, which is to beat the world record of mass energy density for a superconducting coil. This objective is conflicting with the classical strategies of superconducting coil protection. A different protection approach is proposed. The second prototype of the BOSSE project is a small-scale demonstrator of a Superconducting Self-Supplied Electromagnetic Launcher (S3EL), in which a SMES is integrated around the launcher which benefits from the generated magnetic field to increase the thrust applied to the projectile. The S3EL principle and its design are presented. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2016)", edited by Adel Razek

Stabilized superconducting materials and fabrication process

International Nuclear Information System (INIS)

Chevallier, B.; Dance, J.M.; Etourneau, J.; Lozano, L.; Tressaud, A.; Tournier, R.; Sulpice, A.; Chaussy, J.; Lejay, P.

1989-01-01

Superconducting ceramics are fluorinated at a temperature ≤ 120 0 C. Are also claimed new superconducting materials with a fluorine concentration gradient decreasing from the surface to the core. Superconductivity is stabilized and/or improved [fr

Superconductivity in MgB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Muranaka, Takahiro; Akimitsu, Jun [Aoyama Gakuin Univ., Kanagawa (Japan). Dept. of Physics and Mathematics

2011-07-01

We review superconductivity in MgB{sub 2} in terms of crystal and electronic structure, electron-phonon coupling, two-gap superconductivity and application. Finally, we introduce the development of new superconducting materials in related compounds. (orig.)

Superconducting materials and magnets

International Nuclear Information System (INIS)

1991-04-01

The Technical Committee Meeting on Superconducting Materials and Magnets was convened by the IAEA and held by invitation of the Japanese government on September 4-6, 1989 in Tokyo. The meeting was hosted by the National Research Institute for Metals. Topics of the conference related to superconducting magnets and technology with particular application to fusion and the superconducting supercollider. Technology using both high and low-temperature superconductors was discussed. This document is a compendium of the papers presented at the meeting. Refs, figs and tabs

Superconducting self-correcting harmonic coils for pulsed superconducting dipole or multipole magnets

International Nuclear Information System (INIS)

Dael, A.; Kircher, F.; Perot, J.

1975-01-01

Due to the zero resistance of a superconducting wire, an induced current in a closed superconducting circuit is continuously exactly opposed to its cause. This phenomenon was applied to the correction of the field harmonics of a pulsed magnet by putting short-circuited superconducting coils of particular symmetry in the useful aperture of the magnet. After a review of the main characteristics of such devices, the construction of two correcting coils (quadrupole and sextupole) is described. Experimental results of magnetic efficiency and time behavior are given; they are quite encouraging, since the field harmonics were reduced by one or two orders of magnitude

Effect of CuF2 on the Synthesis and Superconducting Properties of (Bi,Pb)2Sr2Ca2Cu3O10 Bulk Ceramic Samples

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Andersen, Niels Hessel

2013-01-01

precursors. In both cases, CuF2 resulted in a clear lowering of the reaction temperature. The superconducting and secondary phase grains are larger in the CuF2 doped samples but the critical transition temperature and the lattice parameters of the high T c phase are not affected. EDS analysis shows...

Development of superconducting ship propulsion system

International Nuclear Information System (INIS)

Sakuraba, Junji; Mori, Hiroyuki; Hata, Fumiaki; Sotooka, Koukichi

1991-01-01

When we plan displacement-type monohull high speed vessels, it is difficult to get the hull form with the wave-making resistance minimum, because the stern shape is restricted by arrangement of propulsive machines and shafts. A small-sized and light-weight propulsive machines will reduce the limit to full form design. Superconducting technology will have capability of realizing the small-sized and light-weight propulsion motor. The superconducting electric propulsion system which is composed of superconducting propulsion motors and generators, seems to be an ideal propulsion system for future vehicles. We have constructed a 480 kW superconducting DC homopolar laboratory test motor for developing this propulsion system. The characteristic of this motor is that it has a superconducting field winding and a segmented armature drum. The superconducting field winding which operates in the persistent current mode, is cooled by a condensation heat exchanger and helium refigerating system built into the cryostat of the superconducting field winding. The operating parameters of this motor agreed well with the design parameters. Using the design concepts of this motor, we have conceptually designed a 150,000-200,000 PS superconducting electric propulsive system for a displacement-type monohull high speed ship. (author)

Superconducting critical-current densities of commercial multifilamentary Nb3Sn(Ti) wires made by the bronze process

International Nuclear Information System (INIS)

Suenaga, M.; Tsuchiya, K.; Higuchi, N.; Tachikawa, K.

1985-01-01

Superconducting critical-current densities Jsub(c) in fields up to 24 T and at 4.2 and 1.8 K were measured for a number of commercial Nb 3 Sn wires which were alloyed with Ti. The best values of Jsub(c) at 20 T and at 4.2 and 1.8 K were 78 and 156 A mm -2 , respectively. In order to achieve these high current densities at H>20 T, it was shown that nonuniformity of the filaments had to be minimized. It was also shown that the grain size of Nb 3 Sn is not very important in determining Jsub(c) at these high magnetic fields, and that achieving high values of critical magnetic field Hsub(c2) is more important than small grain size. (author)

High power coupler issues in normal conducting and superconducting accelerator applications

Energy Technology Data Exchange (ETDEWEB)

Matsumoto, H. [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan)

2001-02-01

The ceramic material (Al{sub 2}O{sub 3}) commonly used for the klystron output coupler in normal conducting, and for an input coupler to superconducting cavities is one of the most troublesome parts in accelerator applications. But the performance can be improved very much by starting with high purity (>99.9%) alumina powder of controlled grain-size (0.1-0.5-{mu}m), and reducing the magnesium (Mg) sintering-binder to lower the dielectric loss to the order of 10{sup -4} at S-band frequencies. It has been confirmed that the new ceramic can stand a peak S-band frequency rf power of up to 300 MW and 2.5 {mu}sec pulse width. (author)

Superconductivity Engineering and Its Application for Fusion 3.Superconducting Technology as a Gateway to Future Technology

Science.gov (United States)

Asano, Katsuhiko

Hopes for achieving a new source of energy through nuclear fusion rest on the development of superconducting technology that is needed to make future equipments more energy efficient as well as increase their performance. Superconducting technology has made progress in a wide variety of fields, such as energy, life science, electronics, industrial use and environmental improvement. It enables the actualization of equipment that was unachievable with conventional technology, and will sustain future “IT-Based Quality Life Style”, “Sustainable Environmental” and “Advanced Healthcare” society. Besides coil technology with high magnetic field performance, superconducting electoronics or device technology, such as SQUID and SFQ-circuit, high temperature superconducting material and advanced cryogenics technology might be great significance in the history of nuclear fusion which requires so many wide, high and ultra technology. Superconducting technology seems to be the catalyst for a changing future society with nuclear fusion. As society changes, so will superconducting technology.

Superconductivity in doped insulators

International Nuclear Information System (INIS)

Emery, V.J.; Kivelson, S.A.

1995-01-01

It is shown that many synthetic metals, including high temperature superconductors are ''bad metals'', with such a poor conductivity that the usual meanfield theory of superconductivity breaks down because of anomalously large classical and quantum fluctuations of the phase of the superconducting order parameter. It is argued that the supression of a first order phase transition (phase separation) by the long-range Coulomb interaction leads to high temperature superconductivity accompanied by static or dynamical charge inhomogeneIty. Evidence in support of this picture for high temperature superconductors is described

Development of superconducting equipment for fusion device

International Nuclear Information System (INIS)

Konno, Masayuki; Ueda, Toshio; Hiue, Hisaaki; Ohgushi, Kouzou

1993-01-01

At Fuji Electric Co., Ltd., the development of superconductivity was started from 1960, and superconducting equipment for fusion device has been developed for ten years. The superconducting equipment, which is developed for fusion by Fuji Electric Co., Ltd., are able to be grouped in three categories which are current lead, superconducting coil and superconducting bus-line. The current lead is an electrical feeder between a superconducting coil and an electrical power supply. The rated current of developed current lead is 30kA at continuous use and 100kA at short time use respectively. The advanced disk type coil is developed for the toroidal field coil and some coils are developed for critical current measurement. Superconductor is applied to the superconducting bus-line between the superconducting coils and the current leads, and the bus-line is being developed for the Large Helical Device. This report describes an abstract of these equipment. (author)

Modulation of transport properties of optimally doped La{sub 1.85}Sr{sub 0.15}CuO{sub 4} thin films via electric field modification of the grain boundaries

Energy Technology Data Exchange (ETDEWEB)

Hassan, Muhammad Umair [Center for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan); Cavendish Laboratory, Cambridge (United Kingdom); Wimbush, Stuart C. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington (New Zealand)

2015-09-15

Modulation of the transport properties of a superconducting La{sub 1.85}Sr{sub 0.15}CuO{sub 4}-based ionic-liquid gated transistor has been achieved. For an applied gate bias V{sub g} ≥ 2 V, the characteristic sheet resistivity vs. temperature (R{sub s}-T) curves exhibit a fully reversible foot feature below the superconducting transition temperature (T{sub c}). In contrast to the behaviour expected from the large charge carrier density of this high-T{sub c} superconductor material, the normal state conductance above T{sub c} also exhibits a large modulation, indicating a larger charge screening length than that predicted from a simple Thomas-Fermi model. We regard these changes as due to electrostatic modification of the charge density at structural imperfections such as grain boundaries present within the sample. Such modification alters the coupling between superconducting domains and dictates the overall R{sub s}-T trend of the gated film. To explain our findings, we employ Mannhart's model of electronic band bending at the grain boundaries and propose that this band bending can be modulated by large electric fields resulting in the observed modulation of the transport properties of the device. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Superconducting magnets technologies for large accelerator

International Nuclear Information System (INIS)

Ogitsu, Toru

2017-01-01

The first hadron collider with superconducting magnet technologies was built at Fermi National Accelerator Laboratory as TEVATRON. Since then, the superconducting magnet technologies are widely used in large accelerator applications. The paper summarizes the superconducting magnet technologies used for large accelerators. (author)

Influence of Superheated Steam Temperature Regulation Quality on Service Life of Boiler Steam Super-Heater Metal

Directory of Open Access Journals (Sweden)

G. T. Kulakov

2009-01-01

Full Text Available The paper investigates influence of change in quality of superheated steam temperature regulations on service life of super-heater metal. А dependence between metal service life and dispersion value for different steel grades has been determined in the paper. Numerical values pertaining to increase of super-heater metal service life in case of transferring from manual regulation to standard system of automatic regulation (SAR have been determined and in case of transferring from standard SAR to improved SAR. The analysis of tabular data and plotted dependencies makes it possible to conclude that any change in conditions of convection super-heater metal work due to better quality of the regulation leads to essential increase of time period which is left till the completion of the service life of a super-heater heating surface.

Structural properties of superconducting Bi-2223/Ag tapes

Energy Technology Data Exchange (ETDEWEB)

Gottschalck Andersen, L.

2001-05-01

The structural properties of silver clad high-T{sub c} superconducting ceramic tapes of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) have been investigated by means of synchrotron X-ray diffraction (including the 3DXRD microscope setup), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). By synchrotron X-ray diffraction in situ studies of the phase development during the transformation of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} (Bi-2212) into Bi-2223, the stoichiometry changes and the texture have been performed during annealing in 8% O{sub 2} and in air. Furthermore, an annealing with two high temperature cycles has been performed to study the equilibrium phenomena. During heating (Ca,Sr){sub 2}PbO{sub 4} decomposes at temperatures between 700 deg. C and 840 deg.C. Simultaneously, the Bi-2212 lattice contracts, indicating an incorporation of Pb. Moreover, the grain mis-alignment decreases significantly. In air we have observed that Bi-2212 partly dissociates into (Ca,Sr){sub 2}CuO{sub 3} and a liquid at temperatures above 812 deg. C. At the annealing temperature Bi-2212 and (Ca,Sr){sub 2}CuO{sub 3} react with the liquid to form Bi-2223. The transformation mechanism is discussed. During cooling below {approx}750 deg.C (Ca,Sr){sub 2}CuO{sub 3} and the liquid mainly transform into Bi-2201. Below {approx}780 deg. C Bi-2223 decomposes to 3221. In addition, a two-step cooling experiment and a decomposition study have been performed in 8% O{sub 2}. By TEM the grain and colony size in the c-axis direction, the angles of c-axis tilt grain boundaries and the intergrowth content are investigated. A fully processed tape has on average 50% thicker grains than a tape after the 1st annealing. The angles of c-axis tilt grain boundaries are on average 14 deg. and 26 deg. for the fully processed tape and the tape after the 1st annealing, respectively. The intergrowth content (15%) and

The initial phase of sudden releases of superheated liquid

International Nuclear Information System (INIS)

Schmidli, J.; Yadigaroglu, G.

1994-01-01

Series of experiments were conducted with refrigerants-114, -12, propane and butane to investigate the initial phase of sudden releases of superheated liquids due to the catastrophic failure of the vessel containing them. The experiments were initiated by shattering spherical flasks of 100 to 2000 ml containing the liquefied, pressurized gases. The variable parameters were the initial superheat, the filling level, the height of the flask above ground, and the relative humidity of the surrounding air. It was found that the initial flashing process is not determined by homogeneous nucleation, but rather by surface instabilities which lead to an evaporation wave traveling from the initial surface towards the center of the released mass. Cloud shape and expansion velocity could be determined from high speed recordings covering the initial stage of the release during which gravity has no influence. When the internal energy was sufficient, it was observed that the expanding droplet/vapor cloud initially propagated spherically with a constant expansion velocity, until Rayleigh-Taylor type instabilities appeared at its surface. Information about the pool which can be formed on the ground, the pressure decay within the flask, the droplet size, and the cloud temperature was collected. The experimental findings for the expansion velocity, as well as for the pool fraction, were the base for a nondimensional analysis leading to correlations which describe the initial phase of such releases and can be used to define the ''source term'' for turbulent dispersion models. (author) 5 figs., 1 tab., 15 refs

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

International Nuclear Information System (INIS)

Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R

2016-01-01

Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0 -values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0 -value of 2 × 10 10 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching. (paper)

Meissner effect in superconducting microtraps

International Nuclear Information System (INIS)

Cano, Daniel

2009-01-01

This thesis investigates the impact of the Meissner effect on magnetic microtraps for ultracold atoms near superconducting microstructures. This task has been accomplished both theoretically and experimentally. The Meissner effect distorts the magnetic fields near superconducting surfaces, thus altering the parameters of magnetic microtraps. Both computer simulations and experimental measurements demonstrate that the Meissner effect shortens the distance between the magnetic microtrap and the superconducting surface, reduces the magnetic-field gradients and dramatically lowers the trap depth. A novel numerical method for calculating magnetic fields in atom chips with superconducting microstructures has been developed. This numerical method overcomes the geometrical limitations of other calculation techniques and can solve superconducting microstructures of arbitrary geometry. The numerical method has been used to calculate the parameters of magnetic microtraps in computer-simulated chips containing thin-film wires. Simulations were carried out for both the superconducting and the normal-conducting state, and the differences between the two cases were analyzed. Computer simulations have been contrasted with experimental measurements. The experimental apparatus generates a magnetic microtrap for ultracold Rubidium atoms near a superconducting Niobium wire of circular cross section. The design and construction of the apparatus has met the challenge of integrating the techniques for producing atomic quantum gases with the techniques for cooling solid bodies to cryogenic temperatures. By monitoring the position of the atom cloud, one can observe how the Meissner effect influences the magnetic microtrap. (orig.)

Meissner effect in superconducting microtraps

Energy Technology Data Exchange (ETDEWEB)

Cano, Daniel

2009-04-30

This thesis investigates the impact of the Meissner effect on magnetic microtraps for ultracold atoms near superconducting microstructures. This task has been accomplished both theoretically and experimentally. The Meissner effect distorts the magnetic fields near superconducting surfaces, thus altering the parameters of magnetic microtraps. Both computer simulations and experimental measurements demonstrate that the Meissner effect shortens the distance between the magnetic microtrap and the superconducting surface, reduces the magnetic-field gradients and dramatically lowers the trap depth. A novel numerical method for calculating magnetic fields in atom chips with superconducting microstructures has been developed. This numerical method overcomes the geometrical limitations of other calculation techniques and can solve superconducting microstructures of arbitrary geometry. The numerical method has been used to calculate the parameters of magnetic microtraps in computer-simulated chips containing thin-film wires. Simulations were carried out for both the superconducting and the normal-conducting state, and the differences between the two cases were analyzed. Computer simulations have been contrasted with experimental measurements. The experimental apparatus generates a magnetic microtrap for ultracold Rubidium atoms near a superconducting Niobium wire of circular cross section. The design and construction of the apparatus has met the challenge of integrating the techniques for producing atomic quantum gases with the techniques for cooling solid bodies to cryogenic temperatures. By monitoring the position of the atom cloud, one can observe how the Meissner effect influences the magnetic microtrap. (orig.)

The energizing of a NMR superconducting coil by a superconducting rectifier

International Nuclear Information System (INIS)

Sikkenga, J.; ten Kate, H.H.J.; van der Klundert, L.J.M.; Knoben, J.; Kraaij, G.J.; Spuorenberg, C.J.G.

1985-01-01

NMR magnets require a good homogeneity within a certain volume and an excellent field stability. The homogeneity can be met using a superconducting shim coil system. The field stability requires a constant current, although in many cases the current decay time constant is too low, due to imperfections in the superconducting wire and joints. This can be overcome using a rectifier. The rectifier can also be used to load the coil. The combination and interaction of the superconducting NMR coil (2.0 Tesla and 0.35 m cold bore) and the rectifier (20 W / 1 kA) is tested. The safety of the system is discussed. The shim coil system can compensate the strayfield of the rectifier. The field decay compensation will be discussed

Liquid phase sintered superconducting cermet

International Nuclear Information System (INIS)

Ray, S.P.

1990-01-01

This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

Japan. Superconductivity for Smart Grids

Energy Technology Data Exchange (ETDEWEB)

Hayakawa, K.

2012-11-15

Currently, many smart grid projects are running or planned worldwide. These aim at controlling the electricity supply more efficiently and more stably in a new power network system. In Japan, especially superconductivity technology development projects are carried out to contribute to the future smart grid. Japanese cable makers such as Sumitomo Electric and Furukawa Electric are leading in the production of high-temperature superconducting (HTS) power cables. The world's largest electric current and highest voltage superconductivity proving tests have been started this year. Big cities such as Tokyo will be expected to introduce the HTS power cables to reduce transport losses and to meet the increased electricity demand in the near future. Superconducting devices, HTS power cables, Superconducting Magnetic Energy Storage (SMES) and flywheels are the focus of new developments in cooperations between companies, universities and research institutes, funded by the Japanese research and development funding organization New Energy and Industrial Technology Development Organization (NEDO)

Low-velocity superconducting accelerating structures

International Nuclear Information System (INIS)

Delayen, J.R.

1990-01-01

The present paper reviews the status of RF superconductivity as applied to low-velocity accelerating properties. Heavy-ion accelerators must accelerate efficiently particles which travel at a velocity much smaller than that of light particles, whose velocity changes along accelerator, and also different particles which have different velocity profiles. Heavy-ion superconducting accelerators operate at frequencies which are lower than high-energy superconducting accelerators. The present paper first discusses the basic features of heavy-ion superconducting structures and linacs. Design choices are then addressed focusing on structure geometry, materials, frequency, phase control, and focusing. The report also gives an outline of the status of superconducting booster projects currently under way at the Argonne National Laboratory, SUNY Stony Brook, Weizmann Institute, University of Washington, Florida State, Saclay, Kansas State, Daresbury, Japanese Atomic Energy Research Institute, Legnaro, Bombay, Sao Paulo, ANU (Canberra), and Munich. Recent developments and future prospects are also described. (N.K.) 68 refs

Superconducting cyclotrons

International Nuclear Information System (INIS)

Blosser, H.G.; Johnson, D.A.; Burleigh, R.J.

1976-01-01

Superconducting cyclotrons are particularly appropriate for acceleration of heavy ions. A review is given of design features of a superconducting cyclotron with energy 440 (Q 2 /A) MeV. A strong magnetic field (4.6 tesla average) leads to small physical size (extraction radius 65 cm) and low construction costs. Operating costs are also low. The design is based on established technology (from present cyclotrons and from large bubble chambers). Two laboratories (in Chalk River, Canada and in East Lansing, Michigan) are proceeding with construction of full-scale prototype components for such cyclotrons

Superconducting phase transition in STM tips

Energy Technology Data Exchange (ETDEWEB)

Eltschka, Matthias; Jaeck, Berthold; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max Planck Institute for Solid State Research, Stuttgart (Germany); Kern, Klaus [Max Planck Institute for Solid State Research, Stuttgart (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland)

2015-07-01

The superconducting properties of systems with dimensions comparable to the London penetration depth considerably differ from macroscopic systems. We have studied the superconducting phase transition of vanadium STM tips in external magnetic fields. Employing Maki's theory we extract the superconducting parameters such as the gap or the Zeeman splitting from differential conductance spectra. While the Zeeman splitting follows the theoretical description of a system with s=1/2 and g=2, the superconducting gaps as well as the critical fields depend on the specific tip. For a better understanding of the experimental results, we solve a one dimensional Usadel equation modeling the superconducting tip as a cone with the opening angle α in an external magnetic field. We find that only a small region at the apex of the tip is superconducting in high magnetic fields and that the order of the phase transition is directly determined by α. Further, the spectral broadening increases with α indicating an intrinsic broadening mechanism due to the conical shape of the tip. Comparing these calculations to our experimental results reveals the order of the superconducting phase transition of the STM tips.

Sample of superconducting wiring (Niobium Titanium)

CERN Multimedia

About NbTi cable: The cable consists of 36 strands of superconducting wire, each strand has a diameter of 0.825 mm and houses 6300 superconducting filaments of niobium-titanium (Nb-Ti, a superconducting alloy). Each filament has a diameter of about 0.006 mm, i.e. 10 times smaller than a typical human hair. The filaments are embedded in a high-purity copper matrix. Copper is a normal conducting material. The filaments are in the superconductive state when the temperature is below about -263ºC (10.15 K). When the filaments leave the superconductive state, the copper acts as conductor transports the electrical current. Each strand of The NbTi cable (at superconducting state) has a current density of up to above 2000 A/mm2 at 9 T and -271ºC (2.15 K). A cable transport a current of about 13000 A at 10 T and -271ºC (2.15 K). About LHC superconducting wiring: The high magnetic fields needed for the LHC can only be reached using superconductors. At very low temperatures, superconductors have no electrical resistan...

Sample of superconducting wiring (Niobium Titanium)

CERN Multimedia

About NbTi cable: The cable consists of 36 strands of superconducting wire, each strand has a diameter of 0.825 mm and houses 6300 superconducting filaments of niobium-titanium (Nb-Ti, a superconducting alloy). Each filament has a diameter of about 0.006 mm, i.e. 10 times smaller than a typical human hair. The filaments are embedded in a high-purity copper matrix. Copper is a normal conducting material. The filaments are in the superconductive state when the temperature is below about -263ºC (10.15 K). When the filaments leave the superconductive state, the copper acts as conductor transports the electrical current. Each strand of The NbTi cable (at superconducting state) has a current density of up to above 2000 A/mm2 at 9 T and -271ºC (2.15 K). A cable transport a current of about 13000 A at 10 T and -271ºC (2.15 K). About LHC superconducting wiring: The high magnetic fields needed for the LHC can only be reached using superconductors. At very low temperatures, superconductors have no electrical resista...

New method of synthesis and physical properties of thick superconducting Er-123 films

International Nuclear Information System (INIS)

Muralidhar, M.; Sakai, N.; Machi, T.; Miyajiri, T.; Hirabayashi, I.; Tanaka, S.

2008-01-01

We have developed a low-cost, short time manufacturing process using a novel method, starting from a mixture of Er 2 BaO 4 , BaCuO 2 , and CuO, with an excess of Er at expense of Ba. Several micrometers thick films were prepared by the screen-printing technique, spreading the mixture paste on silver substrates, processed then in Ar-1% O 2 atmosphere. Using a double-step annealing process, we obtained good quality Er-123 thick films on silver substrates, with T c (onset) 92 K. Formation of large flat grains was observed by scanning electron microscope. According to XRD analysis, the films were preferentially c-axis oriented. The magnetic (induced), self-field J c measured at 77 K was above 32 kA/cm 2 . We observed a strong dependence of the transport current, I c , on the grain size. The maximum I c at 77 K as high as 10 A was observed in the sample with the average grain size around 40 μm. The present results indicate that our technology, enabling preparation of large-area superconducting thick films on Ag-based substrates in short processing times, is relatively cheap and appropriate for utilization in long-length RE-123 silver sheath wire production for commercial applications

Millimeter wave surface resistance of grain-aligned Y1Ba2Cu3O(x) bulk material

International Nuclear Information System (INIS)

Wosik, J.; Kranenburg, R.A.; Wolfe, J.C.; Selvamanickam, V.; Salama, K.

1990-04-01

Measurements are reported of the millimeter-wave surface resistance of grain-aligned YBa2Cu3O(x) bulk material grown by a liquid-phase process. The measurements were performed by replacing the endplate of a TE(011) cylindrical copper cavity with the superconducting sample. Surface resistance was measured for samples with surfaces oriented perpendicular and parallel to the c-axis of the grains. For the parallel configuration, the surface resistance at 77 K and 80 GHz is given. For a very well-aligned sample with a very low density of Y2BaCuO(y) precipitates, measured in the perpendicular configuration, the transition width (10-90 percent) is about 2 K and the surface resistance is derived at 88 K. The effect of microstructure on surface resistance is discussed. 19 refs

Superconducting quantum circuits theory and application

Science.gov (United States)

Deng, Xiuhao

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification. The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to an extra phase factor in wavefunction. We proposed a superconducting quantum Faraday cage to detect temporal interference effect as a consequence of scalar AB phase. Using the superconducting quantum circuit model, the physical system is solved and resulting AB effect is predicted. Further discussion in this chapter shows that treating the experimental apparatus quantum mechanically, spatial scalar AB effect, proposed by Aharanov-Bohm, can't be observed. Either a decoherent interference apparatus is used to observe spatial scalar AB effect, or a quantum Faraday cage is used to observe temporal scalar AB effect. The second study involves protecting a quantum system from losing coherence, which is crucial to any practical quantum computation scheme. We present a theory to encode any qubit, especially superconducting qubits, into a universal quantum degeneracy point (UQDP) where low frequency noise is suppressed significantly. Numerical simulations for superconducting charge qubit using experimental parameters show that its coherence time is prolong by two orders of magnitude using our universal degeneracy point approach. With this improvement, a set of universal quantum gates can be performed at high fidelity without losing too much quantum coherence. Starting in 2004, the use of circuit QED has enabled the manipulation of superconducting qubits with photons. We applied quantum optical approach to model coupled resonators and obtained a four-wave mixing toolbox to operate photons

Superconducting tin core fiber

International Nuclear Information System (INIS)

Homa, Daniel; Liang, Yongxuan; Hill, Cary; Kaur, Gurbinder; Pickrell, Gary

2015-01-01

In this study, we demonstrated superconductivity in a fiber with a tin core and fused silica cladding. The fibers were fabricated via a modified melt-draw technique and maintained core diameters ranging from 50-300 microns and overall diameters of 125-800 microns. Superconductivity of this fiber design was validated via the traditional four-probe test method in a bath of liquid helium at temperatures on the order of 3.8 K. The synthesis route and fiber design are perquisites to ongoing research dedicated all-fiber optoelectronics and the relationships between superconductivity and the material structures, as well as corresponding fabrication techniques. (orig.)

ESCAR superconducting magnet system

International Nuclear Information System (INIS)

Gilbert, W.S.; Meuser, R.B.; Pope, W.L.; Green, M.A.

1975-01-01

Twenty-four superconducting dipoles, each about 1 meter long, provide the guide field for the Experimental Superconducting Accelerator Ring proton accelerator--storage ring. Injection of 50 MeV protons corresponds to a 3 kG central dipole field, and a peak proton energy of 4.2 GeV corresponds to a 46 kG central field. Thirty-two quadrupoles provide focusing. The 56 superconducting magnets are contained in 40 cryostats that are cryogenically connected in a novel series ''weir'' arrangement. A single 1500 W refrigeration plant is required. Design and testing of the magnet and cryostat system are described. (U.S.)

Superconducting six-axis accelerometer

Science.gov (United States)

Paik, H. J.

1990-01-01

A new superconducting accelerometer, capable of measuring both linear and angular accelerations, is under development at the University of Maryland. A single superconducting proof mass is magnetically levitated against gravity or any other proof force. Its relative positions and orientations with respect to the platform are monitored by six superconducting inductance bridges sharing a single amplifier, called the Superconducting Quantum Interference Device (SQUID). The six degrees of freedom, the three linear acceleration components and the three angular acceleration components, of the platform are measured simultaneously. In order to improve the linearity and the dynamic range of the instrument, the demodulated outputs of the SQUID are fed back to appropriate levitation coils so that the proof mass remains at the null position for all six inductance bridges. The expected intrinsic noise of the instrument is 4 x 10(exp -12)m s(exp -2) Hz(exp -1/2) for linear acceleration and 3 x 10(exp -11) rad s(exp -2) Hz(exp -1/2) for angular acceleration in 1-g environment. In 0-g, the linear acceleration sensitivity of the superconducting accelerometer could be improved by two orders of magnitude. The design and the operating principle of a laboratory prototype of the new instrument is discussed.

Superconductivity

International Nuclear Information System (INIS)

Narlikar, A.V.

1993-01-01

Amongst the numerous scientific discoveries that the 20th century has to its credit, superconductivity stands out as an exceptional example of having retained its original dynamism and excitement even for more than 80 years after its discovery. It has proved itself to be a rich field by continually offering frontal challenges in both research and applications. Indeed, one finds that a majority of internationally renowned condensed matter theorists, at some point of their career, have found excitement in working in this important area. Superconductivity presents a unique example of having fetched Nobel awards as many as four times to date, and yet, interestingly enough, the field still remains open for new insights and discoveries which could undeniably be of immense technological value. 1 fig

On anyon superconductivity--

International Nuclear Information System (INIS)

Chen, Y.-H.; Wilczek, F.; Witten, E.; Halperin, B.I.

1989-01-01

We investigate the statistical mechanics of a gas of fractional statistics particles in 2 + 1 dimensions. In the case of statistics very close to Fermi statistics (statistical parameter θ = π(1 - 1/n), for large n), the effect of the statistics is a weak attraction. Building upon earlier RPA calculation for the case n = 2, the authors argue that for large n perturbation theory is reliable and exhibits superfluidity (or superconductivity after coupling to electromagnetism). They describe the order parameter for this superconductng phase in terms of spontaneous breaking of commutativity of translations as opposed to the usual pairing order parameters. The vortices of the superconducting anyon gas are charged, and superconducting order parameters of the usual type vanish. They investigate the characteristic P and T violating phenomenology

Radiation effects on superconductivity

International Nuclear Information System (INIS)

Brown, B.S.

1975-01-01

The effect of radiation on the superconducting transition temperature (T/sub c/), upper critical field (H/sub c2/), and volume-pinning-force density (F/sub p/) were discussed for the three kinds of superconducting material (elements, alloys, and compounds). 11 figures, 3 tables, 86 references

Superconductivity in borides and carbides

International Nuclear Information System (INIS)

Muranaka, Takahiro

2007-01-01

It was thought that intermetallic superconductors do not exhibit superconductivity at temperatures over 30 K because of the Bardeen-Cooper-Schrieffer (BCS) limit; therefore, researchers have been interested in high-T c cuprates. Our group discovered high-T c superconductivity in MgB 2 at 39 K in 2001. This discovery has initiated a substantial interest in the potential of high-T c superconductivity in intermetallic compounds that include 'light' elements (borides, carbides, etc.). (author)

An investigation of texturing by magnetic and mechanical techniques in high critical temperature superconducting ceramics

International Nuclear Information System (INIS)

Deschanels, X.

1992-11-01

The principal goal of this work is to quantify the influence of texture of ceramic superconductors ReBaCuO (Re=Dy, Y) on their critical current density (Jc). The magnetic alignment of particles at ambient temperature is the first technique who has allowed us to produce superconducting (Meissner effect) and textured ceramics. However, these materials are very brittle because of their porosity and this makes it impossible to measure their Jc. Press-forging (or creep sintering) is the second technique who has allowed us to prepare highly textured ceramics materials which are also dense. We have studied the influence of various conditions of thermomechanical treatment (sintering time and temperature, applied load, rate of deformation, density of the material at the beginning) on the texture quality. We have shown that at 900 deg, the eutectic liquid formed by BaCuO 2 , CuO and YBa 2 Cu 3 0 7-Y various mechanisms that help explain the formation of observed texture. After the oxidation stage which requires heat treatment under controlled atmospheres, we obtain superconducting ceramics (Tc=85 K). Moreover, this study also shows that the texture can improve the Jc by 400%, to 750 A/cm 2 at 77 K in the best specimens. This low value is explained by the presence of non-superconducting secondary phases and amorphous phases at the grain boundaries. (Author). 120 refs., figs., tabs

Superconductivity and magnet technology

International Nuclear Information System (INIS)

Lubell, M.S.

1975-01-01

The background theory of superconducting behavior is reviewed. Three parameters that characterize superconducting materials with values of commercial materials as examples are discussed. More than 1000 compounds and alloy systems and 26 elements are known to exhibit superconducting properties under normal conditions at very low temperatures. A wide variety of crystal structures are represented among the known superconductors. The most important ones do seem to have cubic symmetry such as the body-centered cubic (NbZr and NbTi), face-centered cubic (NbN), and the A15 or β-tungsten structures (Nb 3 Sn), V 3 Ga, Nb 3 Ge, Nb 3 Al, and V 3 Si). Attempts to understand some of the particular phenomena associated with superconductors as a necessary prelude to constructing superconducting magnets are discussed by the author. The origin of degradation is briefly discussed and methods to stabilize magnets are illustrated. The results of Oak Ridge National Laboratory design studies of toroidal magnet systems for fusion reactors are described

Hybrid superconducting magnetic suspensions

International Nuclear Information System (INIS)

Tixador, P.; Hiebel, P.; Brunet, Y.; Chaud, X.; Gautier-Picard, P.

1996-01-01

Superconductors, especially high T c ones, are the most attractive materials to design stable and fully passive magnetic suspensions which have to control five degrees of freedom. The hybrid superconducting magnetic suspensions present high performances and a simple cooling mode. They consist of a permanent magnet bearing, stabilized by a suitable magnet-superconductor structure. Several designs are given and compared in terms of forces and stiffnesses. The design of the magnet bearing plays an important part. The superconducting magnetic bearing participates less in levitation but must provide a high stabilizing stiffness. This is achieved by the magnet configuration, a good material in term of critical current density and field cooling. A hybrid superconducting suspension for a flywheel is presented. This system consists of a magnet thrust bearing stabilized by superconductors interacting with an alternating polarity magnet structure. First tests and results are reported. Superconducting materials are magnetically melt-textured YBaCuO

Millimeter wave surface resistance of grain-aligned Y1Ba2Cu3Ox bulk material

International Nuclear Information System (INIS)

Wosik, J.; Kranenburg, R.A.; Wolfe, J.C.; Selvamanickam, V.; Salama, K.

1991-01-01

We report measurements of the millimeter wave surface resistance of grain-aligned YBa 2 Cu 3 O x bulk material grown by a liquid phase process. The measurements were performed by replacing the endplate of a TE 011 cylindrical copper cavity with the superconducting sample. Surface resistance was measured for samples with surfaces oriented perpendicular and parallel to the c-axis of the grains. We show that, for the parallel configuration, the surface resistance at 77 K and 80 GHz is typically near 100 mΩ. For a very well-aligned sample with a very low density of Y 2 BaCuO y precipitates, measured in the perpendicular configuration, the transition width (10%--90%) is about 2 K and the surface resistance is less than 50 mΩ at 88 K. The effect of microstructure on surface resistance is discussed

Development of 50 MVA superconducting generator

International Nuclear Information System (INIS)

Ueda, Kiyotaka; Maki, Naoki; Takahashi, Noriyoshi; Ogata, Hisanao; Sanematsu, Toshihiro.

1984-01-01

Superconducting synchronous generators are expected to be the large capacity turbogenerators of next generation, but they have the structural features considerably different from conventional generators, such as low temperature multiple cylinder rotors and air gap armature winding. For the purpose of grasping the performance of superconducting generators and establishing the fundamental technology for their practical use, Hitachi Ltd. manufactured a 50 MVA superconducting generator. As the results of test, the precooling operation was smoothly finished for about 40 hours, and the superconducting rotor rotated stably at 3000 rpm. The steady and transient electrical characteristics were able to be grasped. It is intended to reflect these results to the development of a practical generator of 500 MVA class expected as the next step. When the superconducting exciting winding cooled by liquid helium is used, the reduction of weight, the improvement of efficiency and the improvement of the stability of power system can be expected. The structural features and the function of superconducting generators, the present state of the development in the world, the outline of the 50 MVA generator, the test results and the problems and the prospect hereafter are reported. The superconducting winding was made of NbTiZr alloy multicore wires. (Kako, I.)

Recent advances in fullerene superconductivity

CERN Document Server

Margadonna, S

2002-01-01

Superconducting transition temperatures in bulk chemically intercalated fulleride salts reach 33 K at ambient pressure and in hole-doped C sub 6 sub 0 derivatives in field-effect-transistor (FET) configurations, they reach 117 K. These advances pose important challenges for our understanding of high-temperature superconductivity in these highly correlated organic metals. Here we review the structures and properties of intercalated fullerides, paying particular attention to the correlation between superconductivity and interfullerene separation, orientational order/disorder, valence state, orbital degeneracy, low-symmetry distortions, and metal-C sub 6 sub 0 interactions. The metal-insulator transition at large interfullerene separations is discussed in detail. An overview is also given of the exploding field of gate-induced superconductivity of fullerenes in FET electronic devices.

Superconductivity in Layered Organic Metals

Directory of Open Access Journals (Sweden)

Jochen Wosnitza

2012-04-01

Full Text Available In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithiotetrathiafulvalene (BEDT-TTF or ET for short. In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity.

Interplay of magnetism and superconductivity

International Nuclear Information System (INIS)

Akhavan, M.

2006-01-01

After about two decades of intense research since the discovery of high-temperature superconductivity (HTSC) in cuprates, although many aspects of the physics and chemistry of these cuprate superconductors are now well understood, the underlying pairing mechanism remains elusive. Magnetism and superconductivity are usually thought as incompatible, but in number of special materials including HTSCs these two mutually excluding mechanisms are found to coexist. The presence in a system of superconductivity and magnetism, gives rise to a large number of interesting phenomenon. This article provides perspective on recent developments and their implications for our understanding of the interplay between magnetism and superconductivity in new materials. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Gauge Model of High-Tc Superconductivity

International Nuclear Information System (INIS)

Ng, Sze Kui

2012-01-01

A simple gauge model of superconductivity is presented. The seagull vertex term of this gauge model gives an attractive potential between electrons for the forming of Cooper pairs of superconductivity. This gauge model gives a unified description of superconductivity and magnetism including antiferromagnetism, pseudogap phenomenon, stripes phenomenon, paramagnetic Meissner effect, Type I and Type II supeconductivity and high-T c superconductivity. The doping mechanism of superconductivity is found. It is shown that the critical temperature T c is related to the ionization energies of elements and can be computed by a formula of T c . For the high-T c superconductors such as La 2-x Sr x CuO 4 , Y Ba 2 Cu 3 O 7 , and MgB 2 , the computational results of T c agree with the experimental results.

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

Superconducting linac booster

International Nuclear Information System (INIS)

Srinivasan, B.; Betigeri, M.G.; Pandey, M.K.; Pillay, R.G.; Kurup, M.B.

1997-01-01

The report on superconducting LINAC booster, which is a joint project of Bhabha Atomic Research Centre (BARC) and Tata Institute of Fundamental Research (TIFR), brings out the work accomplished so far towards the development of the technology of superconducting LINAC to boost the energy of ions from the 14UD Pelletron. The LINAC is modular in construction with each module comprising of a helium cryostat housing four lead-plated quarter wave resonators. The resonators are superconducting for temperatures below 7.19K. An energy boost of 2 MeV/q per module is expected to be achieved. The first module and the post-tandem superbuncher have been fabricated and tested on the LINAC beam line. This report gives a summary of the technological achievements and also brings out the difficulties encountered during the R and D phase. (author)

Superconducting super collider

International Nuclear Information System (INIS)

Limon, P.J.

1987-01-01

The Superconducting Super Collider is to be a 20 TeV per beam proton-proton accelerator and collider. Physically the SCC will be 52 miles in circumference and slightly oval in shape. The use of superconducting magnets instead of conventional cuts the circumference from 180 miles to the 52 miles. The operating cost of the SCC per year is estimated to be about $200-250 million. A detailed cost estimate of the project is roughly $3 billion in 1986 dollars. For the big collider ring, the technical cost are dominated by the magnet system. That is why one must focus on the cost and design of the magnets. Presently, the process of site selection is underway. The major R and D efforts concern superconducting dipoles. The magnets use niobium-titanium as a conductor stabilized in a copper matrix. 10 figures

Superconductivity in doped two-leg ladder cuprates

International Nuclear Information System (INIS)

Qin Jihong; Yuan Feng; Feng Shiping

2006-01-01

Within the t-J ladder model, superconductivity with a modified d-wave symmetry in doped two-leg ladder cuprates is investigated based on the kinetic energy driven superconducting mechanism. It is shown that the spin-liquid ground-state at the half-filling evolves into the superconducting ground-state upon doping. In analogy to the doping dependence of the superconducting transition temperature in the planar cuprate superconductors, the superconducting transition temperature in doped two-leg ladder cuprates increases with increasing doping in the underdoped regime, and reaches a maximum in the optimal doping, then decreases in the overdoped regime

Controllable manipulation of superconductivity using magnetic vortices

International Nuclear Information System (INIS)

Villegas, J E; Schuller, Ivan K

2011-01-01

The magneto-transport of a superconducting/ferromagnetic hybrid structure, consisting of a superconducting thin film in contact with an array of magnetic nanodots in the so-called 'magnetic vortex state', exhibits interesting properties. For certain magnetic states, the stray magnetic field from the vortex array is intense enough to drive the superconducting film into the normal state. In this fashion, the normal-to-superconducting phase transition can be controlled by the magnetic history. The strong coupling between superconducting and magnetic subsystems allows characteristically ferromagnetic properties, such as hysteresis and remanence, to be dramatically transferred into the transport properties of the superconductor.

Active gas discharge cleaning for superconducting lead-plated resonators

International Nuclear Information System (INIS)

Malev, M.D.; Weisser, D.C.

1985-06-01

Lead-plating for superconducting RF resonators historically has been directed toward reducing grain size and eliminating spikes on the surface. Investigations were made of degassing lead-plated surfaces under RF resonant electron discharge or multipacting. The mass-spectra of the residual atmosphere showed that decomposition of hydrocarbons on the surface took place. Discolouration of the lead surface, due to the formation of a carbon layer, was easily observed. A method of cleaning surfaces by ion bombardment employing chemically active gases, was proposed and tested. An RF discharge, initiated by multipacting at pressure 10 -2 - 10 -1 torr was used. The first step, discharge treatment in a CO 2 atmosphere, assures oxidation of carbon and hydrocarbons into gaseous compounds which are removed by pumping. During the second step, discharge treatment in a hydrogen atmosphere, lead oxides are reduced to metal

Superconducting pipes and levitating magnets.

Science.gov (United States)

Levin, Yan; Rizzato, Felipe B

2006-12-01

Motivated by a beautiful demonstration of the Faraday and the Lenz laws in which a small neodymium magnet falls slowly through a conducting nonferromagnetic tube, we consider the dynamics of a magnet falling coaxially through a superconducting pipe. Unlike the case of normal conducting pipes, in which the magnet quickly reaches the terminal velocity, inside a superconducting tube the magnet falls freely. On the other hand, to enter the pipe the magnet must overcome a large electromagnetic energy barrier. For sufficiently strong magnets, the barrier is so large that the magnet will not be able to penetrate it and will be levitated over the mouth of the pipe. We calculate the work that must done to force the magnet to enter a superconducting tube. The calculations show that superconducting pipes are very efficient at screening magnetic fields. For example, the magnetic field of a dipole at the center of a short pipe of radius a and length L approximately > a decays, in the axial direction, with a characteristic length xi approximately 0.26a. The efficient screening of the magnetic field might be useful for shielding highly sensitive superconducting quantum interference devices. Finally, the motion of the magnet through a superconducting pipe is compared and contrasted to the flow of ions through a trans-membrane channel.

Superconducting Metallic Glass Transition-Edge-Sensors

Science.gov (United States)

Hays, Charles C. (Inventor)

2013-01-01

A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

Cooldown of superconducting magnet strings

International Nuclear Information System (INIS)

Yuecel, A.; Carcagno, R.H.

1995-01-01

A numerical model for the cooldown of the superconducting magnet strings in the Accelerator System String Test (ASST) Facility at the Superconducting Super Collider (SSC) Laboratory is presented. Numerical results are compared with experimental data from the ASST test runs. Agreement between the numerical predictions and experiments is very good over the entire range from room temperature to liquid helium temperatures. The model can be readily adapted to predict the cooldown and warmup behavior of other superconducting magnets or cold masses

Superconductivity in bad metals

International Nuclear Information System (INIS)

Emery, V.J.; Kivelson, S.A.

1995-01-01

It is argued that many synthetic metals, including high temperature superconductors are ''bad metals'' with such a poor conductivity that the usual mean-field theory of superconductivity breaks down because of anomalously large classical and quantum fluctuations of the phase of the superconducting order parameter. Some consequences for high temperature superconductors are described

Mechanical Design of Superconducting Accelerator Magnets

International Nuclear Information System (INIS)

Toral, F

2014-01-01

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques

Mechanical Design of Superconducting Accelerator Magnets

CERN Document Server

Toral, Fernando

2014-07-17

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques.

Mechanical Design of Superconducting Accelerator Magnets

Energy Technology Data Exchange (ETDEWEB)

Toral, F [Madrid, CIEMAT (Spain)

2014-07-01

This paper is about the mechanical design of superconducting accelerator magnets. First, we give a brief review of the basic concepts and terms. In the following sections, we describe the particularities of the mechanical design of different types of superconducting accelerator magnets: solenoids, costheta, superferric, and toroids. Special attention is given to the pre-stress principle, which aims to avoid the appearance of tensile stresses in the superconducting coils. A case study on a compact superconducting cyclotron summarizes the main steps and the guidelines that should be followed for a proper mechanical design. Finally, we present some remarks on the measurement techniques.

Can magnetism and superconductivity coexist

International Nuclear Information System (INIS)

Ishikawa, M.

1982-01-01

Recent syntheses of rare earth (RE) ternary superconductors such as (RE)Mo 6 X 8 (X=S or Se) and (RE)Rh 4 B 4 have provided the first opportunity to explore the interaction between magnetism and superconductivity in detail owing to their particular crystal structure. The regular sublattice of the rare-earth ions in these new ternary compounds undergoes a ferro- or antiferromagnetic phase transition in the superconducting state. If the transition is antiferromagnetic, the superconductivity is preserved so that true coexistence results. If it is ferromagnetic, on the other hand, the superconductivity eventually gives way to uniform ferromagnetism at low temperatures. However, recent theories predict several possible states of coexistence even in ferromagnetic superconductors. This article reviews aspects of these new phase transitions in ternary superconductors. (author)

New world of Gossamer superconductivity

International Nuclear Information System (INIS)

Maki, Kazumi; Haas, Stephan; Parker, David; Won, Hyekyung; Dora, Balazs; Virosztek, Attila

2006-01-01

Since the discovery of the high-T c cuprate superconductor La 2-x BaCuO 4 in 1986 by Bednorz and Mueller, controversy regarding the nature or origin of this remarkable superconductivity has continued. However, d-wave superconductivity in the hole-doped cuprates, arising due to the anti-paramagnon exchange, was established around 1994. More recently we have shown that the mean field theory, like the BCS theory of superconductivity and Landau's Fermi liquid theory are adequate to describe the cuprates. The keys for this development are the facts that a) the pseudogap phase is d-wave density wave (dDW) and that the high-T c cuprate superconductivity is gossamer (i.e. it exists in the presence of dDW). (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Superconducting generator technology--an overview

International Nuclear Information System (INIS)

Edmonda, J.S.

1979-01-01

Application of superconducting technology to field windings of large ac generators provides virtually unlimited field capability without incurring resistive losses in the winding. Several small-scale superconducting generators have been built and tested demonstrating the feasibility of such concepts. For machines of much larger capacity, conceptual designs for 300 Mva and 1200 Mva have been completed. The development of a 300 Mva generator is projected. Designed, engineered and fabricated as a turbo generator, the superconducting machine is to be installed in a power plant, tested and operated in concert with a prime mover, the steam generator and the auxiliary support systems of the power plant. This will provide answers to the viability of operating a superconducting machine and its cryogenic handling systems in a full time, demanding environment. 21 refs

Heavy-ion superconducting linacs

International Nuclear Information System (INIS)

Delayen, J.R.

1989-01-01

This paper reviews the status of the superconducting heavy-ion accelerators. Most of them are linacs used as boosters for tandem electrostatic accelerators, although the technology is being extended to very low velocity to eliminate the need for an injector. The characteristics and features of the various superconducting heavy-ion accelerators are discussed. 45 refs

Heavy-ion superconducting linacs

Energy Technology Data Exchange (ETDEWEB)

Delayen, J.R.

1989-01-01

This paper reviews the status of the superconducting heavy-ion accelerators. Most of them are linacs used as boosters for tandem electrostatic accelerators, although the technology is being extended to very low velocity to eliminate the need for an injector. The characteristics and features of the various superconducting heavy-ion accelerators are discussed. 45 refs.

Critical current characteristics and history dependence in superconducting SmFeAsOF bulk

International Nuclear Information System (INIS)

Ni, B; Ge, J; Kiuchi, M; Otabe, E S; Gao, Z; Wang, L; Qi, Y; Zhang, X; Ma, Y

2010-01-01

The superconducting SmFeAsO 1-x F x (x=0.2) polycrystalline bulks were prepared by the powder-in-tube (PIT) method. The magnetic field and temperature dependences of critical current densities in the samples were investigated by resistive and ac inductive (Campbell's) methods. It was found that a fairly large shielding current density over 10 9 A/m 2 , which is considered to correspond to the local critical current density, flows locally with the perimeter size similar to the average grain size of the bulk samples, while an extremely low transport current density of about 10 5 A/m 2 corresponding to the global critical current density flows through the whole sample. Furthermore, a unique history dependence of global critical current density was observed, i.e., it shows a smaller value in the increasing-field process than that in the decreasing-field process. The history dependence of global critical current characteristic in our case can be ascribed to the existence of the weak-link property between the grains in SmFeAsO 1-x F x bulk.

Superconducting properties of modified YBa2Cu3O7-δ ceramics

International Nuclear Information System (INIS)

Kaleva, G.M.; Politova, E.D.; Kudinova, M.V.; Prutchenko, S.G.; Venevtsev, Yu.N.

1993-01-01

In connection with the promising practical applications of high temperature superconductors (HTSC) particular attention has been paid to studying the influence of dopant elements on the properties of HTSC ceramics. According to earlier work, replacement of the yttrium in the compound YBa 2 Cu 3 O 7-8 (1-2-3) by rare earth elements, excluding Ce, Pr, Tb, and Pm, has almost no influence on the superconducting transition temperature (T c ∼ 90 K). Of the alkaline metals, only Sr will displace Ba over a wide range of concentrations (up to 50 at %), but in this case T c is reduced to 86 K. The strongest influence on the superconducting properties results from replacement of copper by 3d transition metals. Introduction of 10 at.% Zn, Co, Fe, Ni, Ti, Mn, or Cr in place of the copper leads to a drastic lowering of T c . At the same time it has been reported that microadditions of individual elements (replacement of Cu by Pd, Ti, and Fe, at a level of 0.1-0.5 at.%,) may elevate conducting phase and improve the contacts between grains, so that, in particular, there is an increase in the critical current density. In view of the possible positive influence which introduction of small quantities of individual elements may have 1-2-3 compounds, in the present work, the authors have studied the action of dopant additions, including complex ones, on this phase, with the goal of improving its superconducting properties. Structural and superconducting properties were studied for samples of YBa 2 (Cu 1- x M x ) 3 O 7-δ , with M = Sb (I), Mn (II), and Sb 1/2 Mn 1/2 (III), and (1-x)Y 1/3 Ba 2/3 CuO 3-δ ·xSr(Sb 1/2 Mn 1/2 )O 3 (IV), using x-ray diffraction, electron microscopy, Mossbauer spectroscopy, as well as changes in the temperature dependence of the resistivity ρ(T)

RADIOFREQUENCY SUPERCONDUCTIVITY: Workshop

International Nuclear Information System (INIS)

Lengeler, Herbert

1989-01-01

Superconducting radiofrequency is already playing an important role in the beam acceleration system for the TRISTAN electron-positron collider at the Japanese KEK Laboratory and new such systems are being prepared for other major machines. Thus the fourth Workshop on Radiofrequency Superconductivity, organized by KEK under the chairmanship of local specialist Yuzo Kojima and held just before the International Conference on High Energy Accelerators, had much progress to review and even more to look forward to

Connectivity and superconductivity

CERN Document Server

Rubinstein, Jacob

2000-01-01

The motto of connectivity and superconductivity is that the solutions of the Ginzburg--Landau equations are qualitatively influenced by the topology of the boundaries, as in multiply-connected samples. Special attention is paid to the "zero set", the set of the positions (also known as "quantum vortices") where the order parameter vanishes. The effects considered here usually become important in the regime where the coherence length is of the order of the dimensions of the sample. It takes the intuition of physicists and the awareness of mathematicians to find these new effects. In connectivity and superconductivity, theoretical and experimental physicists are brought together with pure and applied mathematicians to review these surprising results. This volume is intended to serve as a reference book for graduate students and researchers in physics or mathematics interested in superconductivity, or in the Schrödinger equation as a limiting case of the Ginzburg--Landau equations.

Large Superconducting Magnet Systems

CERN Document Server

Védrine, P.

2014-07-17

The increase of energy in accelerators over the past decades has led to the design of superconducting magnets for both accelerators and the associated detectors. The use of Nb−Ti superconducting materials allows an increase in the dipole field by up to 10 T compared with the maximum field of 2 T in a conventional magnet. The field bending of the particles in the detectors and generated by the magnets can also be increased. New materials, such as Nb$_{3}$Sn and high temperature superconductor (HTS) conductors, can open the way to higher fields, in the range 13–20 T. The latest generations of fusion machines producing hot plasma also use large superconducting magnet systems.

Superconducting accelerator magnet design

International Nuclear Information System (INIS)

Wolff, S.

1994-01-01

Superconducting dipoles, quadrupoles and correction magnets are necessary to achieve the high magnetic fields required for big accelerators presently in construction or in the design phase. Different designs of superconducting accelerator magnets are described and the designs chosen at the big accelerator laboratories are presented. The most frequently used cosθ coil configuration is discussed in detail. Approaches for calculating the magnetic field quality including coil end fields are presented. Design details of the cables, coils, mechanical structures, yokes, helium vessels and cryostats including thermal radiation shields and support structures used in superconducting magnets are given. Necessary material properties are mentioned. Finally, the main results of magnetic field measurements and quench statistics are presented. (orig.)

Large Superconducting Magnet Systems

Energy Technology Data Exchange (ETDEWEB)

Védrine, P [Saclay (France)

2014-07-01

The increase of energy in accelerators over the past decades has led to the design of superconducting magnets for both accelerators and the associated detectors. The use of Nb−Ti superconducting materials allows an increase in the dipole field by up to 10 T compared with the maximum field of 2 T in a conventional magnet. The field bending of the particles in the detectors and generated by the magnets can also be increased. New materials, such as Nb3Sn and high temperature superconductor (HTS) conductors, can open the way to higher fields, in the range 13–20 T. The latest generations of fusion machines producing hot plasma also use large superconducting magnet systems.

Acoustic wave spread in superconducting-normal-superconducting sandwich

International Nuclear Information System (INIS)

Urushadze, G.I.

2004-01-01

The acoustic wave spread, perpendicular to the boundaries between superconducting and normal metals in superconducting-normal-superconducting (SNS) sandwich has been considered. The alternate current flow sound induced by the Green function method has been found and the coefficient of the acoustic wave transmission through the junction γ=(S 1 -S 2 )/S 1 , (where S 1 and S 2 are average energy flows formed on the first and second boundaries) as a function of the phase difference between superconductors has been investigated. It is shown that while the SNS sandwich is almost transparent for acoustic waves (γ 0 /τ), n=0,1,2, ... (where τ 0 /τ is the ratio of the broadening of the quasiparticle energy levels in impurity normal metal as a result of scattering of the carriers by impurities 1/τ to the spacing between energy levels 1/τ 0 ), γ=2, (S 2 =-S 1 ), which corresponds to the full reflection of the acoustic wave from SNS sandwich. This result is valid for the limit of a pure normal metal but in the main impurity case there are two amplification and reflection regions for acoustic waves. The result obtained shows promise for the SNS sandwich as an ideal mirror for acoustic wave reflection

Valence skipping driven superconductivity and charge Kondo effect

International Nuclear Information System (INIS)

Yanagisawa, Takashi; Hase, Izumi

2013-01-01

Highlights: •Valence skipping in metallic compounds can give rise to an unconventional superconductivity. •Several elements in the periodic table show valence skipping (or valence missing), for example, Bi forms the compounds in valence states +3 and +5. •The doping of valence skipping elements will induce superconductivity and this will lead to a possibility of high temperature superconductivity. •We consider the Wolf model with negative-U impurities, and show a phase diagram including superconducting phase. •There is a high temperature region near the boundary. -- Abstract: Valence skipping in metallic compounds can give rise to an unconventional superconductivity. Several elements in the periodic table show valence skipping (or valence missing), for example, Bi forms the compounds in valence states +3 and +5. The doping of valence skipping elements will induce superconductivity and this will lead to a possibility of high temperature superconductivity. We consider the Wolf model with negative-U impurities, and show a phase diagram including superconducting phase. The superconducting state is changed into a metallic state with a local singlet as the attractive interaction |U| increases. There is a high temperature region near the boundary

Superconducting magnet

Science.gov (United States)

1985-01-01

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

Millimeter wave surface resistance of grain-aligned Y1Ba2Cu3O(x) bulk material

Science.gov (United States)

Wosik, J.; Kranenburg, R. A.; Wolfe, J. C.; Selvamanickam, V.; Salama, K.

1991-01-01

Measurements of the millimeter wave surface resistance of grain-aligned YBa2Cu3O(x) bulk material grown by a liquid phase process are reported. The measurements were performed by replacing the endplate of a TE011 cylindrical copper cavity with the superconducting sample. Surface resistance was measured for samples with surfaces oriented perpendicular and parallel to the c-axis of the grains. It is shown that, for the parallel configuration, the surface resistance at 77 K and 80 GHz is typically near 100 milliohms. For a very well-aligned sample with a very low density of Y2BaCuO(y) precipitates, measured in the perpendicular configuration, the transition width (10-90 percent) is about 2 K, and the surface resistance is less than 50 milliohms at 88 K. The effect of microstructure on surface resistance is discussed.

Film grain synthesis and its application to re-graining

Science.gov (United States)

Schallauer, Peter; Mörzinger, Roland

2006-01-01

Digital film restoration and special effects compositing require more and more automatic procedures for movie regraining. Missing or inhomogeneous grain decreases perceived quality. For the purpose of grain synthesis an existing texture synthesis algorithm has been evaluated and optimized. We show that this algorithm can produce synthetic grain which is perceptually similar to a given grain template, which has high spatial and temporal variation and which can be applied to multi-spectral images. Furthermore a re-grain application framework is proposed, which synthesises based on an input grain template artificial grain and composites this together with the original image content. Due to its modular approach this framework supports manual as well as automatic re-graining applications. Two example applications are presented, one for re-graining an entire movie and one for fully automatic re-graining of image regions produced by restoration algorithms. Low computational cost of the proposed algorithms allows application in industrial grade software.

Dehumidification effects in the superheated region (SPR) of a direct expansion (DX) air cooling coil

International Nuclear Information System (INIS)

Xia Liang; Chan Mingyin; Deng Shiming; Xu Xiangguo

2009-01-01

A DX air cooling coil may normally be assumed to have two regions in its refrigerant side, according to refrigerant status, a two-phase region (TPR) and a superheated region (SPR). Dry air side surface of the SPR in a DX air cooling coil has been normally assumed in lumped-parameter mathematical models previously developed without however being validated. Therefore, an experimental study has been carried out to examine such an assumption under different operating conditions. The experimental results suggested that the air side surface of the SPR in a DX air cooling coil was either fully or partially wet under all experimental conditions and assuming dry air side of the SPR could lead to an underestimated total amount of water vapor condensed on the entire DX coil surface. Therefore, it is recommended that the assumption of dry air side in a SPR be no longer used in future lumped-parameter models to be developed for improved modeling accuracy.

Half-metallic superconducting triplet spin multivalves

Science.gov (United States)

Alidoust, Mohammad; Halterman, Klaus

2018-02-01

We study spin switching effects in finite-size superconducting multivalve structures. We examine F1F2SF3 and F1F2SF3F4 hybrids where a singlet superconductor (S) layer is sandwiched among ferromagnet (F) layers with differing thicknesses and magnetization orientations. Our results reveal a considerable number of experimentally viable spin-valve configurations that lead to on-off switching of the superconducting state. For S widths on the order of the superconducting coherence length ξ0, noncollinear magnetization orientations in adjacent F layers with multiple spin axes leads to a rich variety of triplet spin-valve effects. Motivated by recent experiments, we focus on samples where the magnetizations in the F1 and F4 layers exist in a fully spin-polarized half-metallic phase, and calculate the superconducting transition temperature, spatially and energy resolved density of states, and the spin-singlet and spin-triplet superconducting correlations. Our findings demonstrate that superconductivity in these devices can be completely switched on or off over a wide range of magnetization misalignment angles due to the generation of equal-spin and opposite-spin triplet pairings.

Fullerides - Superconductivity at the limit

NARCIS (Netherlands)

Palstra, Thomas T. M.

The successful synthesis of highly crystalline Cs3C60, exhibiting superconductivity up to a record temperature for fullerides of 38 K, demonstrates a powerful synthetic route for investigating the origin of superconductivity in this class of materials.

Fast superconducting magnetic field switch

Science.gov (United States)

Goren, Yehuda; Mahale, Narayan K.

1996-01-01

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

Fast superconducting magnetic field switch

International Nuclear Information System (INIS)

Goren, Y.; Mahale, N.K.

1996-01-01

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs

Superconductivity in compensated and uncompensated semiconductors

Directory of Open Access Journals (Sweden)

Youichi Yanase and Naoyuki Yorozu

2008-01-01

Full Text Available We investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature Tc around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si.

Dust grain charging in a wake of other grains

International Nuclear Information System (INIS)

Miloch, W. J.; Block, D.

2012-01-01

The charging of dust grain in the wake of another grains in sonic and supersonic collisionless plasma flows is studied by numerical simulations. We consider two grains aligned with the flow, as well as dust chains and multiple grain arrangements. It is found that the dust charge depends significantly on the flow speed, distance between the grains, and the grain arrangement. For two and three grains aligned, the charges on downstream grains depend linearly on the flow velocity and intergrain distance. The simulations are carried out with DiP3D, a three dimensional particle-in-cell code with both electrons and ions represented as numerical particles [W. J. Miloch et al., Phys. Plasmas 17, 103703 (2010)].

New world of Gossamer superconductivity

Energy Technology Data Exchange (ETDEWEB)

Maki, Kazumi; Haas, Stephan; Parker, David [Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484 (United States); Won, Hyekyung [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Str. 38, 01187, Dresden (Germany); Department of Physics, Hallym University, Chuncheon 200-702 (Korea); Dora, Balazs; Virosztek, Attila [Department of Physics, Budapest University of Technology and Economics, 1521 Budapest (Hungary)

2006-09-15

Since the discovery of the high-T {sub c} cuprate superconductor La{sub 2-x}BaCuO{sub 4} in 1986 by Bednorz and Mueller, controversy regarding the nature or origin of this remarkable superconductivity has continued. However, d-wave superconductivity in the hole-doped cuprates, arising due to the anti-paramagnon exchange, was established around 1994. More recently we have shown that the mean field theory, like the BCS theory of superconductivity and Landau's Fermi liquid theory are adequate to describe the cuprates. The keys for this development are the facts that a) the pseudogap phase is d-wave density wave (dDW) and that the high-T{sub c} cuprate superconductivity is gossamer (i.e. it exists in the presence of dDW). (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

Superconducting devices at Brookhaven National Laboratory

International Nuclear Information System (INIS)

Dahl, P.F.

1978-04-01

The various ongoing programs in applied superconductivity supported by BNL are summarized, including the development of high field ac and dc superconducting magnets for accelerators and other applications, of microwave deflecting cavities for high energy particle beam separators, and of cables for underground power transmission, and materials research on methods of fabricating new superconductors and on metallurgical properties affecting the performance of superconducting devices

Superconductivity and macroscopic quantum phenomena

International Nuclear Information System (INIS)

Rogovin, D.; Scully, M.

1976-01-01

It is often asserted that superconducting systems are manifestations of quantum mechanics on a macroscopic scale. In this review article it is demonstrated that this quantum assertion is true within the framework of the microscopic theory of superconductivity. (Auth.)

Superconductivity in heavily boron-doped silicon carbide

Directory of Open Access Journals (Sweden)

Markus Kriener, Takahiro Muranaka, Junya Kato, Zhi-An Ren, Jun Akimitsu and Yoshiteru Maeno

2008-01-01

Full Text Available The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

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

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.)

Thermal expansion of coexistence of ferromagnetism and superconductivity

International Nuclear Information System (INIS)

Hatayama, Nobukuni; Konno, Rikio

2010-01-01

The temperature dependence of thermal expansion of coexistence of ferromag-netism and superconductivity below the superconducting transition temperature T cu of a majority spin conduction band is investigated. Majority spin and minority spin superconducting gaps exist in the coexistent state. We assume that the Curie temperature is much larger than the superconducting transition temperatures. The free energy that Linder et al. [Phys. Rev. B76, 054511 (2007)] derived is used. The thermal expansion of coexistence of ferromagnetism and superconductivity is derived by the application of the method of Takahashi and Nakano [J. Phys.: Condens. Matter 18, 521 (2006)]. We find that we have the anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures.

Superconductivity in multilayer perovskite. Weak coupling analysis

International Nuclear Information System (INIS)

Koikegami, Shigeru; Yanagisawa, Takashi

2006-01-01

We investigate the superconductivity of a three-dimensional d-p model with a multilayer perovskite structure on the basis of the second-order perturbation theory within the weak coupling framework. Our model has been designed with multilayer high-T c superconducting cuprates in mind. In our model, multiple Fermi surfaces appear, and the component of a superconducting gap function develops on each band. We have found that the multilayer structure can stabilize the superconductivity in a wide doping range. (author)

Crystalline color superconductivity

International Nuclear Information System (INIS)

Alford, Mark; Bowers, Jeffrey A.; Rajagopal, Krishna

2001-01-01

In any context in which color superconductivity arises in nature, it is likely to involve pairing between species of quarks with differing chemical potentials. For suitable values of the differences between chemical potentials, Cooper pairs with nonzero total momentum are favored, as was first realized by Larkin, Ovchinnikov, Fulde, and Ferrell (LOFF). Condensates of this sort spontaneously break translational and rotational invariance, leading to gaps which vary periodically in a crystalline pattern. Unlike the original LOFF state, these crystalline quark matter condensates include both spin-zero and spin-one Cooper pairs. We explore the range of parameters for which crystalline color superconductivity arises in the QCD phase diagram. If in some shell within the quark matter core of a neutron star (or within a strange quark star) the quark number densities are such that crystalline color superconductivity arises, rotational vortices may be pinned in this shell, making it a locus for glitch phenomena

Monte Carlo evaluation of the neutron detection efficiency of a superheated drop detector

Energy Technology Data Exchange (ETDEWEB)

Gualdrini, G F [ENEA, Centro Ricerche ` Ezio Clementel` , Bologna (Italy). Dipt. Ambiente; D` Errico, F; Noccioni, P [Pisa, Univ. (Italy). Dipt. di Costruzioni Meccaniche e Nucleari

1997-03-01

Neuron dosimetry has recently gained renewed attention, following concerns on the exposure of crew members on board aircraft, and of workers around the increasing number of high energy accelerators for medical and research purpose. At the same time the new operational qualities for radiation dosimetry introduced by ICRU and the ICRP, aiming at a unified metrological system applicable to all types of radiation exposure, involved the need to update current devices in order to meet new requirements. Superheated Drop (Bubble) Detectors (SDD) offer an alternative approach to neutron radiation protection dosimetry. The SDDs are currently studied within a large collaborative effort involving Yale University. New Haven CT, Pisa (IT) University, the Physikalisch-Technische Bundesanstalt, Braunschweig D, and ENEA (Italian National Agency for new Technologies Energy and the Environment) Centre of Bologna. The detectors were characterised through calibrations with monoenergetic neutron beams and where experimental investigations were inadequate or impossible, such as in the intermediate energy range , parametric Monte Carlo calculations of the response were carried out. This report describes the general characteristic of the SDDs along with the Monte Carlo computations of the energy response and a comparison with the experimental results.

Kinetics of Texture and Colour Changes in Chicken Sausage during Superheated Steam Cooking

Directory of Open Access Journals (Sweden)

Abdulhameed Asmaa A.

2016-07-01

Full Text Available The aim of this study was to develop a kinetic model to describe the texture and colour changes of chicken sausage during superheated steam cooking. Chicken sausages were cooked at temperature ranging from 150-200°C with treatment times ranging from 2-6 mins. The texture profile was evaluated in terms of hardness, cohesiveness, gumminess, and chewiness, while the colour parameters were estimated in terms of lightness (L*, redness (a*, yellowness (b*, and total colour difference (∆E. Experimental data showed a gradual reduction in texture parameters as cooking times and temperatures increased. The L* value of the colour showed a linear reduction with cooking condition, while the a*, b*, and ∆E values showed a contrary effects. The decrease in texture parameters and L*-value of colour parameter followed the first-order kinetic model. While, zero-order kinetic model was adapted to fit the a* and b*. The modified first order kinetic showed a good fit for total ∆E. Significant correlations between colour and texture parameters were observed, which showed that a* alone could be used to predict the texture of chicken sausage.

Civilian applications for superconducting magnet technology developed for defense

International Nuclear Information System (INIS)

Johnson, R.A.; Klein, S.W.; Gurol, H.

1986-01-01

Seventy years after its discovery, superconducting technology is beginning to play an important role in the civilian sector. Strategic defense initiative (SDI)-related research in space- and ground-based strategic defense weapons, particularly research efforts utilizing superconducting magnet energy storage, magnetohydrodynamics (MHD), and superconducting pulsed-power devices, have direct applications in the civilian sector as well and are discussed in the paper. Other applications of superconducting magnets, which will be indirectly enhanced by the overall advancement in superconducting technology, include high-energy physics accelerators, magnetic resonance imaging, materials purifying, water purifying, superconducting generators, electric power transmission, magnetically levitated trains, magnetic-fusion power plants, and superconducting computers

Ac loss measurements on a superconducting transformer for a 25 kA superconducting rectifier

NARCIS (Netherlands)

ten Kate, Herman H.J.; Mulders, J.M.; de Reuver, J.L.; van de Klundert, L.J.M.

1984-01-01

Ac loss measurements have been performed on a superconducting transformer. The transformer is a part of a 25 kA thermally switched superconducting rectifier operating at a frequency of 0.1 Hz. The loss measurements have been automatized by means of a microcomputer sampling four relevant signals and

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

Controlling superconductivity by tunable quantum critical points.

Science.gov (United States)

Seo, S; Park, E; Bauer, E D; Ronning, F; Kim, J N; Shim, J-H; Thompson, J D; Park, Tuson

2015-03-04

The heavy fermion compound CeRhIn5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn5. Slight tin-substitution for indium in CeRhIn5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn5, which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn5.

Superconducting quantum circuits theory and application

OpenAIRE

Deng, Xiuhao

2015-01-01

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification.The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to a...

Superconducting Qubit Optical Transducer (SQOT)

Science.gov (United States)

2015-08-05

parts on optical signals and any quasiparticle loss caused by optical photons on microwave signals. Using a superconducting 3D cavity as the microwave...plasmonic and quasiparticle losses. 3. The electro-optic material should be easily integrable with superconducting circuits. A fully integrated

Superconducting bearings for flywheel applications

DEFF Research Database (Denmark)

Abrahamsen, A.B.

2001-01-01

A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...

Observation of weak coupling effects in Ba0.6 K0.4 Fe2 As2 junctions patterned across a naturally formed grain boundary

International Nuclear Information System (INIS)

Hong, Sung-Hak; Lee, Soon-Gul; Lee, Nam Hoon; Kang, Won Nam

2014-01-01

We have fabricated intergrain nanobridge junctions from a Ba 0.6 K 0.4 Fe 2 As 2 film and observed their weak coupling effects. We prepared the junction by patterning a nanobridge across a natural grain boundary by using a focused ion beam etching technique and studied their superconducting transition properties. The resistive transition showed three steps: the transitions of the bulk, the microbridge, and the junction grain boundary. Current–voltage curves showed typical Josephson junction characteristics, well-matched with the model of a resistively shunted junction incorporated with thermal fluctuations. Fitting data to theory revealed much larger current fluctuations than expected from the Johnson–Nyquist theorem. The junction showed a linear temperature dependence of the critical current and a constant normal-state resistance, indicating that the grain boundary played a role as a tunnel barrier with a very poor conductance. (paper)

Superconductivity, energy storage and switching

International Nuclear Information System (INIS)

Laquer, H.L.

1974-01-01

The phenomenon of superconductivity can contribute to the technology of energy storage and switching in two distinct ways. On one hand the zero resistivity of the superconductor can produce essentially infinite time constants so that an inductive storage system can be charged from very low power sources. On the other hand, the recovery of finite resistivity in a normal-going superconducting switch can take place in extremely short times, so that a system can be made to deliver energy at a very high power level. Topics reviewed include: physics of superconductivity, limits to switching speed of superconductors, physical and engineering properties of superconducting materials and assemblies, switching methods, load impedance considerations, refrigeration economics, limitations imposed by present day and near term technology, performance of existing and planned energy storage systems, and a comparison with some alternative methods of storing and switching energy. (U.S.)

Superconductivity in all its states

CERN Multimedia

Globe Info

2011-01-01

Temporary exhibition at the Saint-Genis-Pouilly Tourist Office. For the 100th anniversary of its discovery, take a plunge into the amazing world of superconductivity. Some materials, when cooled down to extreme temperatures, acquire a remarkable property -  they become superconducting. Superconductivity is a rare example of a quantum effect that can be witnessed on the macroscopic scale and is today at the heart of much research. In laboratories, researchers try to gain a better understanding of its origins, study new superconducting materials, explore the phenomenon at the nanometric scale and pursue their indefatigable search for new applications. Monday to Friday: 09:00 a.m. to 12:00 and 2:30 p.m. to 6:30 p.m. Saturday: 10:00 a.m. to 12:00 noon » Open to all – Admission free For further information: +33 (0)4 50 42 29 37

ASC 84: applied superconductivity conference. Final program and abstracts

International Nuclear Information System (INIS)

1984-01-01

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

ASC 84: applied superconductivity conference. Final program and abstracts

Energy Technology Data Exchange (ETDEWEB)

1984-01-01

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

Utilization of virtual reality for reading the superheated emulsion detector

International Nuclear Information System (INIS)

Santos Sobrinho, Jose C.; Santo, Andre C.E.; Pereira, Claudio M.N.A.; Mol, Antonio C.A.

2013-01-01

This paper presents a method based on Virtual Reality for reading the Superheated Emulsion Detector (Bubble Detector). The proposed method is an alternative to: automatic counters offered by the manufacturers of detectors, since they have a relatively high cost (acquisition, maintenance and periodic calibration), and visual counting of detectors, since it only has an advantage when there are a small number of bubbles. The method starts with the collection of detector's digital images in order to obtain a sequence of images to create an animation that is displayed with the help of Virtual Reality. To this end, it is modeled, using OpenGL graphics library, a virtual environment for visualizing and manipulating virtual detector. It is made, then a calibration of this virtual environment thus ensuring the correspondence of the model with reality. The reading of the detector (bubbles count) is made visually by the user with the assistance of stereo vision and a 3D cursor to navigation, marking and counting the bubbles. The user views a further auxiliary display that shows the three-dimensional cursor position, the labeled amount of bubbles and the measured dose. After testing, the following results were achieved: better precision in counting the bubbles compared with the 10% reported by the manufacturer of the automatic reader; achieving a low cost tool that requires no calibration constant in the process of maintenance and/or lifetime; minimizing the problem of manual counting for large number of bubbles and ease of use, because can be operated by a common user. (author)

Utilization of virtual reality for reading the superheated emulsion detector

Energy Technology Data Exchange (ETDEWEB)

Santos Sobrinho, Jose C.; Santo, Andre C.E.; Pereira, Claudio M.N.A.; Mol, Antonio C.A., E-mail: volksparati@hotmail.com, E-mail: cotelli.andre@gmail.com, E-mail: cmnap@ien.gov.br, E-mail: mol@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2013-07-01

This paper presents a method based on Virtual Reality for reading the Superheated Emulsion Detector (Bubble Detector). The proposed method is an alternative to: automatic counters offered by the manufacturers of detectors, since they have a relatively high cost (acquisition, maintenance and periodic calibration), and visual counting of detectors, since it only has an advantage when there are a small number of bubbles. The method starts with the collection of detector's digital images in order to obtain a sequence of images to create an animation that is displayed with the help of Virtual Reality. To this end, it is modeled, using OpenGL graphics library, a virtual environment for visualizing and manipulating virtual detector. It is made, then a calibration of this virtual environment thus ensuring the correspondence of the model with reality. The reading of the detector (bubbles count) is made visually by the user with the assistance of stereo vision and a 3D cursor to navigation, marking and counting the bubbles. The user views a further auxiliary display that shows the three-dimensional cursor position, the labeled amount of bubbles and the measured dose. After testing, the following results were achieved: better precision in counting the bubbles compared with the 10% reported by the manufacturer of the automatic reader; achieving a low cost tool that requires no calibration constant in the process of maintenance and/or lifetime; minimizing the problem of manual counting for large number of bubbles and ease of use, because can be operated by a common user. (author)

Color-symmetric superconductivity in a phenomenological QCD model

DEFF Research Database (Denmark)

Bohr, Henrik; Providencia, C.; Providencia, J. da

2009-01-01

In this paper, we construct a theory of the NJL type where superconductivity is present, and yet the superconducting state remains, in the average, color symmetric. This shows that the present approach to color superconductivity is consistent with color singletness. Indeed, quarks are free...... in the deconfined phase, but the deconfined phase itself is believed to be a color singlet. The usual description of the color superconducting state violates color singletness. On the other hand, the color superconducting state here proposed is color symmetric in the sense that an arbitrary color rotation leads...

Application of superconductivity to pulse fields

International Nuclear Information System (INIS)

Saito, Shigeo; Suzawa, Chizuru; Ohkura, Kengo; Nagata, Masayuki; Kawashima, Masao

1984-01-01

Numerous attempts to apply the superconductive phenomena of zero electrical resistivity to AC (pulsed) magnets in addition to conventional DC magnet fields are being made in the areas of poloidal coils of nuclear fusion, energy storage, rotary machines, and induction for stabilization of electric power systems. In pulsed superconductive magnets, the stability of the superconductivity and the generation of heat due to AC loss are serious problems. Based on the knowledge obtained through the development of various types of superconductors, magnets, cryostats, and other superconductive-related products, Cu-Ni/Cu/Nb-Ti mixed-matrix fine multifilamentary superconductor wire and the stable, low AC loss superconductors used therein, magnets, and FRP cryostats are developed and manufactured. (author)

Teledyne's historical contribution to developing superconductivity

International Nuclear Information System (INIS)

McDonald, W.K.

1986-01-01

Of the contributions made to superconductivity by Teledyne Wah Change Albany (TWCA), two have been outstanding. The first is the establishment of a stable and low cost NbTi alloy. Estimates of cost savings passed along to conductor manufacturers and, subsequently, to the applications of superconductivity range between $24,000,000 and $31,000,000 over the years from 1980 to present. Secondly, TWCA has understood the necessity of cooperating with the scientific community in order to understand critical relationships of metallurgy to superconductivity characteristics. The knowledge gained is integrated into alloy production on a commercial basis. The most notable example is the recent increase in current density prospects for the proposed Superconducting Super Collider

Application of superconductivity in cyclotron construction

International Nuclear Information System (INIS)

Blosser, H.G.

1982-01-01

This paper reviews major concepts and design features of the new class of cyclotrons which use superconducting coils to provide main magnet excitation. The discussion begins with a brief historical review tracing the evolution of these ''superconducting'' cyclotrons and the impact of this application of superconductivity in pushing back traditional cyclotron construction limits. This is followed by a review of the principal phenomena which come into play to set new limits on the operating regime, and the nature of these limits, some of which arise from orbit properties and some of which result from construction intricacies in the coil and in the rf system. Conclusions anticipate a future widely encompassing role in the application of superconductivity to cyclotron

Superconducting magnetic quadrupole

Energy Technology Data Exchange (ETDEWEB)

Kim, J.W.; Shepard, K.W.; Nolen, J.A.

1995-08-01

A design was developed for a 350 T/m, 2.6-cm clear aperture superconducting quadrupole focussing element for use in a very low q/m superconducting linac as discussed below. The quadrupole incorporates holmium pole tips, and a rectangular-section winding using standard commercially-available Nb-Ti wire. The magnet was modeled numerically using both 2D and 3D codes, as a basis for numerical ray tracing using the quadrupole as a linac element. Components for a prototype singlet are being procured during FY 1995.

Refinement of Crystalline Boron and the Superconducting Properties of MgB2 by Attrition Ball Milling

International Nuclear Information System (INIS)

Lee, J. H.; Shin, S. Y.; Park, H. W.; Jun, B. H.; Kim, C. J.

2008-01-01

We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the MgB 2 pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the MgB 2 that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the B 2 O 3 peak became stronger in the powders, resulting in an increase in the amount of MgO within the MgB 2 volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density (J c ), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

Grain-filling duration and grain yield relationships in wheat mutants

International Nuclear Information System (INIS)

Larik, A.S.

1987-01-01

Nine stable mutants of bread wheat along with their mother cultivars were investigated for grain-filling characteristics in relation to grain yield. Significant differences among mutants for grain-filling duration and grain-filling index were observed. Inspite of the consistent differences in grain-filling duration there was no significant association between grain-filling duration and grain yield in C-591 and Nayab mutants. Failure to detect an yield advantage due to differences in grain-filling duration in these genotypes suggests that any advantage derived from alteration of grain-filling period may have been outweighed by the coincident changes in length of the vegetative period. Other factors such as synchrony of anthesis may have limited out ability to find an association between grainfilling duration and grain yield. On the contrary, significant association between grain-filling duration and grain yield displayed by indus-66 indus-66 mutants derived from gamma rays, shows the ability of gamma rays to induce functional alternations in the pattern of gene arrangements controlling these traits. Thus, the vaability observed in these physiological traits suggests that selection for these traits could be useful in improving grain yield. (author)

Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites

Science.gov (United States)

Norem, James H.; Pellin, Michael J.

2013-06-11

Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.

High temperature interface superconductivity

International Nuclear Information System (INIS)

Gozar, A.; Bozovic, I.

2016-01-01

Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

Superconducting magnets for HERA

International Nuclear Information System (INIS)

Wolff, S.

1987-01-01

The Hadron-Electron-Ring Accelerator (HERA) presently under construction at DESY, Hamburg, consists of an electron storage ring of 30 GeV and a proton storage ring of 820 GeV. Superconducting magnets are used for the proton ring. There are 416 superconducting bending magnets of 4.698 T central field and 8.824 m magnetic length, 224 superconducting quadrupoles of 91.2 T/m central gradient and many superconducting correction dipoles, quadrupoles and sextupoles. The main dipoles and quadrupoles consist of two-layer coils of 75 mm inner diameter clammed with aluminium (for the dipoles) or stainless steel laminations (for the quadrupoles). The collared coils are surrounded by a laminated cold iron yoke and supported inside a low loss cryostat. The protection system uses cold diodes to bypass the current around a quenching magnet. The magnets are cooled with one phase helium supplied by a 3 block central refrigeration system of 20 kW refrigeration power at 4.3 K. Two helium is returned through the magnets in good thermal contact with the one phase helium in the dipoles for temperature control. This paper describes the magnet system and gives the results obtained for prototype magnets

Applied superconductivity. Handbook on devices and applications. Vol. 1 and 2

Energy Technology Data Exchange (ETDEWEB)

Seidel, Paul (ed.) [Jena Univ. (Germany). Inst. fuer Festkoerperphysik, AG Tieftemperaturphysik

2015-07-01

The both volumes contain the following 12 chapters: 1. Fundamentals; 2. Superconducting Materials; 3. Technology, Preparation, and Characterization (bulk materials, thin films, multilayers, wires, tapes; cooling); 4, Superconducting Magnets; 5. Power Applications (superconducting cables, superconducting current leads, fault current limiters, transformers, SMES and flywheels; rotating machines; SmartGrids); 6. Superconductive Passive Devices (superconducting microwave components; cavities for accelerators; superconducting pickup coils; magnetic shields); 7. Applications in Quantum Metrology (superconducting hot electron bolometers; transition edge sensors; SIS Mixers; superconducting photon detectors; applications at Terahertz frequency; detector readout); 8. Superconducting Radiation and Particle Detectors; 9. Superconducting Quantum Interference (SQUIDs); 10. Superconductor Digital Electronics; 11. Other Applications (Josephson arrays as radiation sources. Tunable microwave devices) and 12. Summary and Outlook (of the superconducting devices).

Applied superconductivity. Handbook on devices and applications. Vol. 1 and 2

International Nuclear Information System (INIS)

Seidel, Paul

2015-01-01

The both volumes contain the following 12 chapters: 1. Fundamentals; 2. Superconducting Materials; 3. Technology, Preparation, and Characterization (bulk materials, thin films, multilayers, wires, tapes; cooling); 4, Superconducting Magnets; 5. Power Applications (superconducting cables, superconducting current leads, fault current limiters, transformers, SMES and flywheels; rotating machines; SmartGrids); 6. Superconductive Passive Devices (superconducting microwave components; cavities for accelerators; superconducting pickup coils; magnetic shields); 7. Applications in Quantum Metrology (superconducting hot electron bolometers; transition edge sensors; SIS Mixers; superconducting photon detectors; applications at Terahertz frequency; detector readout); 8. Superconducting Radiation and Particle Detectors; 9. Superconducting Quantum Interference (SQUIDs); 10. Superconductor Digital Electronics; 11. Other Applications (Josephson arrays as radiation sources. Tunable microwave devices) and 12. Summary and Outlook (of the superconducting devices).

Color superconductivity

International Nuclear Information System (INIS)

Wilczek, F.

1997-01-01

The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken