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in subjects: "Superconducting Composites"

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Note on the cryostatic stability of superconducting composites

A careful discussion is given of the ''equal area condition'' developed by Maddock et al. In order to make the essential points as clear as possible, analytical solutions are derived under simplifying assumptions (simple model for heat transfer by nucleate and film boiling liquid helium; constant heat conduction and specific heat) instead of using more realistic but less controllable computer calculations. A quantitative definition of the concept of a long wire is given. Num… more

Date: February 1, 1978

Creator: Gauster, W. F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Cryogenic recovery analysis of forced flow supercritical helium cooled superconductors

A coupled heat conduction and fluid flow method of solution was presented for cryogenic stability analysis of cabled composite superconductors of large scale magnetic coils. The coils are cooled by forced flow supercritical helium in parallel flow channels. The coolant flow reduction in one of the channels during the spontaneous recovery transient, after the conductor undergoes a transition from superconducting to resistive, necessitates a parallel channel analysis. A way to simulate the parall… more

Date: August 1, 1977

Creator: Lee, A. Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fabrication of superconducting wire composites by directional solidification. Yearend report on project

Progress is reported for a program to develop a new process for producing composite Nb/sub 3/Sn/Cu superconducting wires and evaluating their critical current densities and the stress dependence of their critical currents. The process involves directional solidification of Cu--Nb or Cu--Nb--Sn alloys. (SDF)

Date: October 1, 1977

Creator: Verhoeven, J. D.; Gibson, E. D.; Finnemore, D. & Ostenson, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Magnetization of in situ multifilamentary superconducting Nb/sub 3/Sn-Cu composites

Magnetic properties are reported for in situ superconducting Nb/sub 3/Sn composites that have exhibited attractive electrical properties and superior mechanical characteristics. Magnetization measurements were conducted up to 4 T at 4.2 K on a variety of samples of different sizes and twist pitches, and the results are presented in absolute M-H curves and losses per cycle. It is observed that the magnetization of such composites is generally proportional to the size of the wire (approx. 0.25 to… more

Date: January 1, 1980

Creator: Shen, S. S. & Verhoeven, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stress and strain effects on the properties of composite superconductors

Practical superconductors for use in the production of high magnetic fields are generally in the form of composites of filaments of superconducting material embedded in a matrix of normally conducting material. Lorentz forces which arise during magnet operation are examples of sources of external stress, while internal stresses can arise during the fabrication of the composite superconductor, primarily due to differential thermal contraction between different materials in the composite. The pro… more

Date: January 1, 1982

Creator: Welch, D.O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Thermodynamics of the tantalum-carbon-chlorine-hydrogen system applied to the CVD of carbide/carbon composite materials

Complex equilibrium thermodynamic calculations using the computer code SOLGASMIX-PV were performed for the Ta-Cl-H and Ta-C-Cl-H systems in order to evaluate the chemistry associated with the chemical vapor deposition of Ta, Ta/sub 2/C, and TaC on graphite yarn and woven structures. Results of the thermodynamic calculations were compared with coated materials prepared by hydrogen reduction of TaCl/sub 5/(g) and C/sub 3/H/sub 6/(g) between 1025 and 1223/sup 0/K using a variety of reaction gas co… more

Date: April 1, 1980

Creator: Behrens, R. G.; Newkirk, L. R. & Wallace, T. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effects of cyclic strains on transport properties of a superconducting composite: phase I, degradation of electrical conductivity in copper at 4. 2 K

Aspects of superconducting composites for magnetic fusion applications are discussed.

Date: August 1, 1977

Creator: Fisher, E. S.; Kim, S. H.; Linz, R. J. & Turner, A. P. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Diffusion welding multifilament superconductive composites

Diffusion welding is shown to be a feasible method for joining composites of niobium-titanium superconductor alloy filaments in a pure copper matrix. Good results were repeatedly obtained using 15/sup 0/ scarf joints welded with externally heated tooling and simple uniaxial compression loading in a conventional hydraulic press. Weld cycles of less than one hour total elapsed time were readily attainable. Through proper closed-die design, it was possible to increase welding pressure sufficiently… more

Date: February 27, 1978

Creator: Witherell, C.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Mechanisms of the oxidation of metals and alloys with emphasis on superconductors

Research work performed at M.I.T. under this contract has had two major thrusts. One thrust deals with the oxidation processing of, and phase transformations in, the Yb{sub n}Ba{sub 2n}Cu{sub 3n+n}O{sub x} (n = 1, 2, {infinity}) superconducting oxide system while the second thrust deals with the optimization of the properties of oxidation processed Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y}/Ag superconducting microcomposites.

Date: January 1, 1991

Item Type: Report

Partner: UNT Libraries Government Documents Department

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a-c losses of 19-strand subcables for the ANL 3. 3-MJ coil

From the time constant and the hysteresis loss measurements of the subcables, it is estimated that approximately 60% of the ac losses of the ANL 3.3 MJ coil at 6 T/s of the central field are due to the losses within the 19-strand subcable itself. The remaining 40% of the losses seem to come mainly from the coupling among the weakly insulated 19-strand subcables in the final cable. The outer sheath copper wires of the subcable improve the stability of the subcable, especially when it is soldered… more

Date: January 1, 1983

Creator: Kim, S. H.; Dawson, J. W.; McGhee, D. G. & Shen, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanical behavior and stress effects in hard superconductors: a review

The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys niobium-titanium and niobium-zirconium exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2/sup 0/K revealed serrated stress-strain curves, nonlinear elastic effects and reduced ductility. The nonlinear behavior is probably due to twinning and detwinning or a reversib… more

Date: November 1, 1977

Creator: Koch, C. C. & Easton, D. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The effect of magnetic impurities and barriers on the magnetization and critical current of fine filament NbTi composites

It has been shown that the highest critical currents in fine filament NbTi conductors are obtained when the filaments are closely spaced. However, the filaments in a composite with a high purity copper matrix tend to be coupled via the ''proximity effect'' as the filament spacing is reduced leading to large magnetization at low fields. To reduce the ''proximity'' coupling, trial billets of NbTi have been fabricated with Cu-30% Ni matrix, Cu-0.5% Mn matrix and one with a Ni barrier around the fi… more

Date: January 1, 1987

Creator: Ghosh, A.K.; Sampson, W.B.; Gregory, E.; Kreilick, S. & Wong, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

MAXIMSUPER: a computer program to assist in the design of multifilamentary superconducting composites. [Nb/sub 3/Sn]

The strain degradation of critical current density has been analytically and experimentally investigated for multifilamentary superconducting composites produced in a bronze core geometry. Analytic results were obtained from a computer program (MAXIMSUPER) which predicts the stresses and strains in composites as a result of thermal and axial loading. Tensile test data for Nb/sub 3/Sn are described. It is believed that the strain dependence of the critical current found in Nb/sub 3/Sn is due to … more

Date: July 3, 1979

Creator: Hoard, R. W.; Scanlan, R. M. & Hirzel, D. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Processing of superconductive materials and high frequency

We do not know yet if superconductivity will become useful without refrigeration. Now, the superconductors are so different from copper that it is difficult to imagine replacing copper with such a brittle material. Superconductors conduct dc with no loss, ac with small losses, and microwaves in co-axial lines with almost no loss and with no dispersion from dc to the highest frequencies. They will probably allow us to close the gap between radio frequency and infrared optical transmission. Clear… more

Date: January 1, 1987

Creator: Smith, J.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Propagation of normal zones of finite size in large, composite superconductors

Very large, composite superconductors have been proposed for use in energy storage magnets. A typical conductor, rated at 230 kA, has been discussed by J. Waynert, Y. Eyssa, and X. Huang, namely, a 6-cm aluminum cylinder with superconducting filaments on its outer surface. Owing to its large size and nonuniform distribution of filaments, such a conductor can sustain normal zones of finite size that travel at a uniform velocity along the conductor. This paper presents a simple, analytical model … more

Date: January 1, 1989

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Accelerator magnet designs using superconducting magnetic shields

Superconducting dipoles and quadrupoles for existing accelerators have a coil surrounded by an iron shield. The shield limits the fringe field of the magnet while having minimal effect on the field shape and providing a small enhancement of the field strength. Shields using superconducting materials can be thinner and lighter and will not experience the potential of a large de-centering force. Boundary conditions for these materials, material properties, mechanical force considerations, cryosta… more

Date: October 1, 1990

Creator: Brown, B.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Flux jumps in a pinch

This paper discusses flux jumps, using solid-state physics. The forces on the outermost leptons due to the current flowing through the metal are small compared with the forces in the interatomic environment. The processing of NbTi used in superconducting cables creates defects that pin magnetic flux lines. If one of these pinning sites lets its flux line go, it starts a positive feedback event known as ''flux jump''. The heat generated can be conducted away before the material goes normal if th… more

Date: July 1, 1987

Creator: Kuchnir, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Practical superconductor development for electrical power applications

Development of useful high-critical-temperature (high-{Tc}) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes technical progress of research and development efforts aimed at producing superconducting components based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and Tl-Ba-Ca… more

Date: October 1, 1991

Creator: Goretta, K.C. (comp.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Superconducting current densities in bronze-processed Nb/sub 3/Sn multifilamentary wires

Five multifilamentary wires with diameters of 0.41 mm and different ratios of bronze to Nb (R = 2 to 3.7) were obtained from Airco. The superconducting critical currents were measured at 4.2/sup 0/K in magnetic fields of 8 to 19 T. Effects of heat treatments were investigated. 4 figures. (DLC)

Date: January 1, 1981

Creator: Okuda, S.; Suenaga, M. & Luhman, T.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Superconducting proximity effect for in situ and model layered systems

The primary drawback for in situ composites is that the ac losses are higher than for mechanically produced multifilamentary wire. To develop an understanding of the proximity effect so that analytical expressions will be available for design, a model system is developed based on PbCd. Items discussed include boundary conditions at SN interface, phonon spectral function, supercurrents through normal barriers, flux entry fields, and implications for in situ composites. (GHT)

Date: January 1, 1980

Creator: Finnemore, D.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Stability calculations for MHD magnets

When a cryostable composite conductor carrying current experiences a heat input from a mechanical perturbation, a normal region develops which initially propagates and then either collapses or continues to propagate. A computer model has been devised to study this phenomenon. The model incorporates initial or continuing heat input from mechanical perturbations, heat conducted to the neighboring elements of the conductor and, if appropriate, heat conducted through insulation to neighboring turns… more

Date: January 1, 1978

Creator: Turner, L. R.; Wang, S. T. & Harrang, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Continuum fluorescence of Cu in NbTi/Cu composite wires

Continuum fluorescence across interfaces separating regions of differing composition is difficult to calculate. This paper illustrates a case of continuum fluorescence in analysis of superconducting NbTi/Cu composite wire which could lead to erroneous compositions due to Cu fluorescence by continuum x rays generated in an NbTi alloy. An approximate treatment of the continuum fluorescence is presented. 3 figs, 4 refs.

Date: April 1, 1994

Creator: Hlava, P. F.; Michael, J. R.; Nelson, G. C. & Headley, T. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanisms of the oxidation of metals and alloys with emphasis on superconductors. A report for the period beginning December 1, 1990

Date: December 31, 1991

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors

The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (HTS). For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Josephson junction dissipation which dominates flux motion of the insulating regions betwe… more

Date: June 1, 1994

Creator: Gray, K. E.; Hettinger, J. D. & Kim, D. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department