United States of America As Represented by the Secretary of the Air Force

Charles E Oberly

Gregory Kozlowski

Harold L Gegel

Rex L Schlicher

James C Ho

A new process for making a neodymium gallate (NGO) surface layer on the inside surface of a protective outer sheath of nickel surrounding a core of yttrium-based copper oxide (YBCO) superconductor material permits manufacture of very high performance superconducting wire and tape. The NGO surface layer acts as a diffusion barrier to prevent diffusion of nickel into the YBCO during high temperature melt-processing. The NGO is applied, preferably by slurry casting, to a flat strip of solid nickel and then sintered at temperatures above about 1000&deg; C. The sintering binds the NGO to the nickel strip and fixes it so that it will not react chemically with the YBCO during later melt-processing. The nickel strip and NGO diffusion barrier layer are next rolled into a trough and YBCO ceramic powder inserted inside the trough. The trough is then further rolled into a tube leaving an open seam for oxygen to penetrate during the oxygen anneal procedure of melt-processing. Finally, the tube sheath acts as a crucible for melt-processing of the YBCO to complete the manufacture of a high performance superconducting wire.

Neodymium gallate surface barrier for melt-processed YBa2Cu3Ox conductor with nickel sheath

Liquid hydrogen is used to completely cool all elements of the generator including bearings, stator conductor, rotor conductor, magnetic flux shield, and excitation mechanisms. By essentially immersing the generator in liquid hydrogen, cryogenic interface problems are minimized. The conductor windings will utilize pure metals such as aluminum to minimize the weight and the ohmic heat loss in the machine. Complications of liquid helium cooling for superconducting windings and quench phenomena due to thermal instabilities in the superconductors are eliminated. The use of extremely low resistance of liquid hydrogen cooled aluminum permits heat removal in the confined space of the rotor field winding at magnetic field and current density that can exceed that of superconductors. Because iron is not required in the generator, very high voltages can be generated.

Cryogenic wound rotor for lightweight, high voltage generators

A muzzle arc suppressor allowing rapid repetitive refiring of railguns. A varistor or varistors electrically connect the muzzle ends of a railgun. Resistive inserts are placed inside the rails near the muzzle end. When the railgun projectile reaches the resistive inserts, the voltage across the varistor increases to above the varistor breakdown voltage, thereby commutating the railgun current from the projectile to the varistor, and dissipating excess magnetic energy through resistance heating of the varistor. The varistor is preferably made of zinc oxide, which is temperature invariant over a wide temperature range. The varistor may be pre-cooled to increase its energy absorbtion ability. A specific embodiment of the arc suppressor has the zinc oxide varistor conformably shaped to surround the rails. The conformably shaped varistor includes coolant passages.

Muzzle arc suppressor for electromagnetic railgun

The conductor contains high-purity aluminum embedded in an aluminum-iron-cerium alloy matrix. It is not superconducting but still has extremely low electrical resistance at service temperatures. Selection of the aluminum-base alloy matrix with diffusionless alloying elements (iron and cerium) allows production of a multifilamentary conductor with the aluminum filaments maintaining their original high purity and consequently their very low electrical resistivity, even after a high temperature annealing cycle is applied. The composite conductor has good properties for both electromagnetic and thermal diffusion, which are critical to high-power, fast-pulse operation.

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Urbana, OH, United States of America

Charles E Oberly