Abstract: A high temperature superconductor fault current limiter and a method of using same. The fault current limiter comprises a high temperature superconductor material structure at least partially encapsulated in an epoxy having thermal conductivity properties that enable the superconductor to heat rapidly during a fault condition while preventing thermal runaway. The epoxy encapsulation decreases the critical current density of the superconductor material structure and increases the rate at which resistance increases with increasing current once the critical current density is exceeded. Preferably, the epoxy has thermal expansion properties approximately equal to the thermal expansion properties of the superconductor material structure.

Abstract: A method of measuring a cryogenic fluid level utilizing a high temperature ceramic superconductor material driven above its level of critical current density. A high temperature ceramic superconductor is placed in cryogenic fluid and a voltage is applied between two points on the superconductor. The voltage drop is then measured at a third point on the superconductor. This voltage drop corresponds to the change in cryogenic fluid level, and thus can be used to measure the fluid level. Sensitivity of the measurement is increased by driving the high temperature ceramic superconductor above its level of critical current density.

Abstract: A high temperature superconductor and composite structure. A superconductor is disposed on a silver substrate without interdiffusion. The superconductor is formed by heating to a temperature not exceeding the peritectic point of the superconductor material, providing an oxidizing atmosphere while not exceeding the melting point of silver and disposing the superconductor on the silver substrate.

Abstract: A cryogenic fluid level sensor utilizing a high temperature ceramic superconductor material driven above its level of critical current density, an exterior housing for holding the length of ceramic superconductor material, a support material disposed between the ceramic superconductor material and the exterior housing, and a resilient retention material disposed opposite the ceramic superconductor material for holding the superconductor material while allowing expansion and contraction thereof during thermal cycling. A method of producing a superconductor material having a low level of critical current density and favorable structural properties is also disclosed.

Abstract: A method of preparing a superconductor. The method includes preparing a mixture of superconductor material constituents, disposing the constituents on a silver containing substrate, heating the mixture of constituents on a silver containing substrate, heating the mixture in a first atmosphere having a partial pressure of CO.sub.2 to control decomposition of at least one of the superconductor material constituents and changing the first atmosphere to a second atmosphere consisting essentially of an oxidizing gas capable of allowing decomposition of at least one of the superconductor material constituents.

Abstract: An improved process for preparing superconducting ceramic powder includes calcining superconducting precursor compounds in an atmosphere having a controlled amount of oxygen, generally not more than that found in air, the remainder of the atmosphere composed of a gas or mixture of gases inert with respect to the ceramic. A preferred process includes forming the precursor compounds into a slurry, granulating the slurry, drying the granules (a binder can be added to the slurry to promote green strength), and calcining in the controlled atmosphere to provide the desired HTSC (high temperature superconductor) composition.