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in subjects: "Current Density"

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Potential for use of high-temperature superconductors in fusion reactors

The present rate of development of high-temperature superconductors (HTSs) is sufficiently rapid that there may be opportunities for their use in contemporary fusion devices such as the International Thermonuclear Experimental Reactor (ITER). The most likely 1application is for delivering power to the superconducting magnets, especially in substituting for the current leads between the temperatures of 4 K and 77K. A second possible application of HTSs is as a liquid-nitrogen-cooled power bus, c… more

Date: January 1, 1991

Creator: Hull, J.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Extracted current densities from surface conversion sources of negative ions

The condition for extracting a maximum negative ion current density is found when the product of the radius of the negative ion conversion electrode, the cross-section for negative and positive ion recombination, and the density of positive ions in the ion source equals one. The optimum output is obtained at the highest positive ion density and the smallest electrode radius.

Date: February 10, 1982

Creator: Fink, J.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Detection of plasma equilibrium shifts with fiber optic sensing of image currents

The radial equilibrium position of Reverse Field Pinch experiments is determined by the j x B force on the plasma. The current density is that of the toroidal plasma current and the B field is the vertical magnetic field which is present in the plasma. This magnetic field is the result of several components. The main field, generated by the toroidal current windings, is corrected by adjustable trim windings to achieve a desired equilibrium position. There is an additional component to the field… more

Date: January 1, 1988

Creator: Forman, P.R.; Jahoda, F.C. & Miller, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Determination of optimum electrolyte composition for molten carbonate fuel cells

The objective of this study is to determine the optimum electrolyte composition for molten carbonate fuel cells. To accomplish this, the contractor will provide: (1) Comprehensive reports of on-going efforts to optimize carbonate composition. (2) A list of characteristics affected by electrolyte composition variations (e.g. ionic conductivity, vapor pressure, melting range, gas solubility, exchange current densities on NiO, corrosion and cathode dissolution effects). (3) Assessment of the overa… more

Date: January 1, 1987

Creator: Yuh, C. Y. & Pigeaud, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Polarization spectroscopy of tokamak plasmas

Measurements of polarization of spectral lines emitted by tokamak plasmas provide information about the plasma internal magnetic field and the current density profile. The methods of polarization spectroscopy, as applied to the tokamak diagnostic, are reviewed with emphasis on the polarimetry of motional Stark effect in hydrogenic neutral beam emissions. 25 refs., 7 figs.

Date: September 1, 1991

Creator: Wroblewski, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Incomplete relaxation and finite beta plasmas

The treatment of plasma relaxation presented in this paper is a natural generalization of the earlier treatment of Taylor and yields predictions of finite beta plasma confinement. The analysis yields predictions for global reversed-field pinch (RFP) parameters such as ..beta../sub theta/, F, and theta. In qualitative accordance with the experimental evidence that RFP discharges have a cool outer region of high resistivity, we present a plasma model which permits vanishing wall values of pressur… more

Date: January 1, 1980

Creator: Turner, L. & Christiansen, J.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-field superconducting accelerator magnets

The next generation of accelerators for high-energy physics will require high-field, small-bore dipole magnets: in the region of 10 T and 40-mm diam. For such magnets, there is a great incentive to attain high overall current density through increasing the current density within the superconductor and minimizing the copper stabilizer. Both Nb-Ti operating at 1.8 K and Nb/sub 3/sn at 4.2 are candidate superconductors. Two programs in the US and one in Japan are directed toward the development of… more

Date: May 1, 1982

Creator: Taylor, C.; Meuser, R.; Caspi, S.; Gilbert, W.; Hassenzahl, W.; Peters, C. et al.

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

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Recent advances in high-temperature superconductor wire fabrication and applications development

In this paper, recent advances in fabrication of HTS wires are summarized, and detailed discussion is provided for developments in near- and intermediate-term applications. Near-term applications, using presently obtainable current densities, include: liquid-nitrogen depth sensors, cryostat current leads, and magnetic bearings. Intermediate-term applications, using current densities expected to be available in the near future include fault-current limiters and short transmission lines. 25 refs.

Date: January 1, 1992

Creator: Hull, J.R. & Uherka, K.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Advances in materials science, Metals and Ceramics Division. Triannual progress report, February-May 1980

Research is reported in the magnetic fusion energy and laser fusion energy programs, aluminium-air battery and vehicle research, geothermal research, nuclear waste management, basic energy science, and chemistry and materials science. (FS)

Date: August 1, 1980

Creator: Truhan, J.J. & Gordon, K.M. (eds.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Determination of optimum electrolyte composition for molten carbonate fuel cells

Date: January 1, 1986

Creator: Pigeaud, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Development of high temperature superconductors for magnetic field applications

The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS mag… more

Date: January 1, 1991

Creator: Larbalestier, D.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Calculations of three-dimensional distributions of current density, electric field, and power deposition in externally sustained electrical discharges. [For calculating performance of CO/sub 2/ laser]

In the design of larger and larger CO/sub 2/ laser amplifiers, the problem of attaining the ideal uniform discharge in these large discharge volumes becomes increasingly difficult and expensive to solve. The practical solution is a compromise between uniformity and other design considerations. In order to judge the adequacy of each compromise, a method of predicting the distribution of current density and electric field throughout the discharge volume is needed. When these electrical distributi… more

Date: January 1, 1982

Creator: Leland, W. T. & Kircher, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effects of H/sub 2/S on molten carbonate fuel cells

This report summarizes the results of a literature survey conducted by the Institute of Gas Technology (IGT) under Phase I of a multi-phase program to investigate and identify the mechanism(s) responsible for molten carbonate fuel cell (MCFC) performance losses when operating on sulfur-containing gases. The objective of this literature survey was twofold: (1) to review the reported data on the interaction of H/sub 2/S with nickel-containing materials; and (2) to review reported investigations o… more

Date: April 1, 1984

Creator: Remick, R. J. & Anderson, G. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The giant ion sources of neutral-beam injectors for fusion

All large tokamak fusion experiments today use auxiliary heating by multi-megawatt beams of neutral isotopes of hydrogen injected with energies in the neighborhood of 100 keV per atom. This requires reliable operation of large ion sources, each delivering many tens of amperes of protons or deuterons, and soon even tritons. For meaningful experiments these sources must operate with pulse durations measured in seconds, although the duty factor may still be small. It is remarkable that the success… more

Date: July 1, 1989

Creator: Kunkel, W.B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Yttria-stabilized zirconia solid oxide electrolyte fuel cells, monolithic solid oxide fuel cells

Small cell size, thin ceramic components, and high operating temperature are the key features of the MSOFC. The small size of individual cells in the monolithic structure increases the active surface area. For example, an MSOFC with channels about 1 mm in diameter has a ratio of active surface area to volume of about 9.4 sq cm/cu cm. This is about seven times the ratio for conventional fuel cells. On this basis alone, an MSOFC with a channel diameter of 1 mm should produce the same power as a c… more

Date: January 1, 1989

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Development of a current collection loss management system for SDI homopolar power supplies

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operated continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved t… more

Date: January 1, 1987

Creator: Hannan, W.F. III.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Design desiderata for a laminar flow quadrupole-focused acceleration column

The Pierce design acceleration column has been widely used to accelerate high current beams. It operates well in the space charge limited condition, and will produce beams with a temperature comparable with that of the source. It is restricted in current density, however, by the Child-Langmuir relation. If the ion source itself is not the limiting constraint, then the achievable current density is limited by the electric field at which sparking occurs. One sees clearly that the achievable curre… more

Date: January 1, 1983

Creator: Maschke, A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Advances in materials science, Metals and Ceramics Division. Triannual progress report, October 1979-January 1980

Progress is summarized concerning magnetic fusion energy materials, laser fusion energy, aluminium-air battery and vehicle, geothermal research, oil-shale research, nuclear waste management, office of basic energy sciences research, and materials research notes. (FS)

Date: March 31, 1980

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Development of an ion source for long-pulse (30-s) neutral beam injection

This paper describes the development of a long-pulse positive ion source that has been designed to provide high brightness deuterium beams (divergence approx. = 0.25/sup 0/ rms, current density approx. = 0.15 A cm/sup -2/) of 40 to 45 A, at a beam energy of 80 keV, for pulse lengths up to 30 s. The design and construction of the ion source components are described with particular emphasis placed on the long-pulse cathode assembly and ion accelerator.

Date: January 1, 1982

Creator: Menon, M. M.; Barber, G. C.; Blue, C. W.; Dagenhart, W. K.; Gardner, W. L.; Haselton, H. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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BNL neutral beam development group. Progress report, FY 1979

The objective of the BNL Neutral Beam Program is to develop a 250 keV neutral beam system suitable for heating experiments in toroidal or mirror plasma devices. The system will be based on acceleration and neutralization of negative hydrogen ions produced in and directly extracted from a source. The objective of source studies is to develop a unit delivering 10 A of negative ion currents in pulses of 1 s duration or longer, operating with extracted current densities of at least 0.5 A/cm/sup 2/ … more

Date: January 15, 1980

Creator: Prelec, K. & Sluyters, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Irreversibility behavior in Ag-sheathed Bi-based superconducting wires

Irreversibility lines for Ag/(Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y}(2223) wires prepared through a phase formation- decomposition-recovery (PFDR) process and normal annealing process were determined using both AC susceptibility measurements under DC fields and magnetisation measurements. It was found that flux pinning was enhanced in the PFDR processed samples over the normal processed samples, in particular at temperature above 77 K. The PFDR process results in high mass density, gr… more

Date: April 1, 1992

Creator: Dou, S.X.; Liu, H.K.; Guo, Y.C.; Wang, J.; Jin, X.J.; Hu, Q.Y. (New South Wales Univ., Kensington (Australia)) et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Cell-module and fuel-conditioner development. 8th quarterly report, July-September 1981

Progress on the second Phase of a six Phase program to develop commercially viable on-site integrated energy systems (OS/IES) using phosphoric acid fuel cell (PAFC) modules to convert fuel to electricity is reported. Phase II is a planned two year effort to develop appropriate fuel cell module and fuel conditioner conceptual designs. The fuel cell module development effort comprises three coordinated tasks: (1) design of large cell stacks; (2) stack fabrication; and (3) stack testing. The resul… more

Date: October 1, 1981

Creator: Hoover, Jr., D. Q.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Assessment study of superconducting fault-current limiters operating at 77K

The possible impact of nitrogen-cooled superconductors on the design and cost of superconducting fault-current limiters is assessed by considering the technical specifications such devices must meet and by comparing material properties of 77-K and 4-K superconductors. The main advantage of operating superconductors at 77 K is that the refrigeration operating cost is reduced by a factor of up to 25, and the refrigeration capital cost is reduced by a factor of up to 10. The heat capacity of 77 K … more

Date: January 1, 1992

Creator: Giese, R. F. & Runde, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department