Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-12-21
2003-04-29
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C228S248100
Reexamination Certificate
active
06553646
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
FIELD OF THE INVENTION
This invention relates to a method for enclosing a ceramic filament, particularly enclosing same in a metallic sheath.
BACKGROUND OF THE INVENTION
The present invention relates to metal composite wire or sheet structures containing low-temperature (low-T
c
) or high-temperature (high-T
c
) superconducting (HTS
c
) ceramic oxides. In these structures, the superconductor is applied as a deposit, within a metal composite matrix with or without additional metallic, metal alloy, or ceramic filamentary components. The present invention relates, in particular, to the design, process fabrication and construction of HTSc-metal composite wires or sheets of finite or indefinite continuous length, in which the HTSc ceramic is embedded within or deposited on a metallic sheet that is used in the final composite structure. The superconducting ceramic is used either as a single filament (superconducting layer), or as multiple filaments, or as either in association with other metallic or ceramic filamentary components that provide greater mechanical, thermal or electrical stability to the function of the composite structure. Furthermore, each filamentary component containing HTSc ceramic is imparted a predetermined c-axis orientation relative to the longitudinal or radial axis of the wire, or planar axis of the sheet. Application of this c-axis textured ceramic sheet allows the designer to improve the electromagnetic performance characteristics of the composite structure.
Superconductors conduct electromagnetic power without resistive loss when cooled below an intrinsic thermodynamic transition temperature, commonly defined as the T
c
of the material. In addition to allowing the resistanceless transport of electromagnetic power, the superconductive state also nulls electric fields and expells magnetic flux (lines of force) from within the interior of the material. This combination of properties allows superconductors to be useful in a variety of electromagnetic systems that require electromagnetic power storage, power delivery, power regulation, low loss power transmission, power amplification, or electromagnetic shielding.
Electromagnetic power can be stored within a superconducting wire or sheet when it is wound or formed into a topological surface representative of a magnetic coil or solenoid. Power is supplied to the superconductor by driving an electrical current through it from an external source. This generates an electrical supercurrent within the superconductor. This is known as charging the superconductor. When the superconductor is sufficiently charged, a superconducting short circuit is activated between the ends of the coil structure, so the electrical supercurrents circulating within the coil may follow a closed loop continuous superconductive path. Since the superconducting path does not dissipate the electrical power, the supercurrents persist indefinitely. After the superconducting storage device as been charged, the stored power can be tapped to supply power to an electrical grid.
This same configuration can be used to regulate power to the grid when active electrical switches and relays that monitor the grid are configured to tap the electrical power in the superconductor when the grid is experiencing an electrical energy surplus. Since the superconductor is an extremely low loss electrical power conduit, cables, bus bars, or leads, can also be used to transmit power from an electrical energy source to the load with negligible power loss, or power loss that is significantly less than that of normally resistive power feeds. Since the superconductor has no dc electrical resistivity, it can be used to transfer electrical power in a cryogenic environment with negligible heat generation.
Radio frequency (rf) electrical power is amplified by a cavity resonator. The physical dimensions and dielectric constants of the materials used to construct the cavity determine the frequencies that will maximally experience power amplification within the resonator. Quality-factors (Q-factors) characterize the gain per unit frequency within the resonator structure. Q-factors can be greatly enhanced, allowing significant improvements to rf gain over a narrower band of rf frequencies. If the walls of the cavity structure are coated with a layer of superconducting material.
Since the superconducting state thermodynamically prevents electric and magnetic fields from penetrating its interior, a hollow superconducting surface enclosing field sensitive instrumentation can shield these devices from harmful external electromagnetic radiations. Likewise, if a magnetic field source or electromagnetic radiation source is placed within a hollow superconducting shell, the superconducting surface can be used to confine or constrain field emissions or to shape magnetic field emissions protruding out a hole in the superconducting shell.
These embodiments of superconducting topologies are useful in a variety of electrical systems that require the efficient utilization of the available power budget, such as an airborne or space-based system. They are also useful in devices that require the efficient manipulation, generation, or delivery of powerful electromagnetic pulses, for instances in electromagnetic weaponry or electromagnetic rail guns; or, the regulation, storage and transmission of electric power over an electrical grid; or, the amplification of an rf power source, for instance in electric countermeasure devices or radar systems; or to protect sensitive electronic equipment against electronic countermeasures or interfering radiation.
All of these applications require the superconducting material to be cooled to a temperature below its thermodynamic transition temperature. If the material is heated above its T
c
it will fail to operate as a superconductor and revert back to its state of normal resistance, causing the unique functionality of the material to be lost to the application. The application of magnetic fields and electrical currents to the superconductor can also stress the thermodynamic state of superconductivity. If the superconductor is maintained at the lowest possible temperature and no electrical currents are passing through it, a threshold magnetic field can be applied above which magnetic flux is no longer expelled from the material and it fails to remain superconducting. The value of magnetic field that causes the superconducting state to rupture is defined as the critical magnetic field (H
c
). If the temperature of the superconductor is increased to a value that is elevated but still below its T
c
the intensity of an applied magnetic field that will rupture the superconducting state is less than the H
c
measured at the lowest possible temperature The intensity of magnetic field that is needed to rupture the superconductor is an increasing function of decreasing temperature below T
c
of the superconductor. This relationship can also be interpreted as meaning the T
c
of the superconductor is a decreasing function of increasing applied magnetic field intensity.
The physical representation of this relationship can be mapped onto a graph using temperature and magnetic field intensity as axes, with a line defining the boundary between superconducting and normally resistive states of the material. This line is referred to as the irreversibility line of the superconductor. All values of field and temperature that are within this line (closer to the origin of the axes) allow the material to retain its superconductive properties. All values of field and temperature that are exterior to this line (further from the origin of the axes) rupture the superconductive state of the material.
A similar functionality is observed with electrical current traveling through the superconductor. At the lowest possible temperature, and in the absence of an applied or gen
Bryant David P.
Stover Thomas C.
The United States of America as represented by the Secretary of
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