Lance D. Cooley

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The discovery of superconductivity at 39 K in magnesium diboride, MgB2, raises many issues, a critical one being whether this material resembles a high-temperature copper oxide superconductor or a low-temperature metallic superconductor in terms of its behaviour in strong magnetic fields. Although the copper oxides exhibit very high transition temperatures,(More)
The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has(More)
We report a significant enhancement of the upper critical field Hc2 of different MgB2 samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities ρ, we show a clear trend of an increase in Hc2 as ρ increases. One particular high resistivity film had a zero-temperature Hc2(0) well above the Hc2 values of(More)
D.C. Larbalestier*, M. O. Rikel*, L.D. Cooley*, A.A. Polyanskii*, J.Y. Jiang*, S. Patnaik*, X.Y. Cai*, D.M. Feldmann*, A. Gurevich*, A.A. Squitieri*, M.T. Naus*, C. B. Eom* E.E. Hellstrom,* † * Applied Superconductivity Center, University of Wisconsin–Madison, 1500 Engineering Drive, Madison, WI 53706 † Department of Materials Science and Engineering,(More)
An important predicted, but so far uncharacterized, property of the new superconductor MgB2 is electronic anisotropy arising from its layered crystal structure. Here we report on three c-axis oriented thin films, showing that the upper critical field anisotropy ratio H ‖ c2/H ⊥ c2 is 1.8 to 2.0, the ratio increasing with higher resistivity. Measurements of(More)
High engineering critical current density JE of > 500A/mm 2 at 20T and 4.2K can be regularly achieved in Ag-sheathed multifilamentary Bi2Sr2CaCu2Ox (Bi-2212) round wire when the sample length is several centimeters. However, JE(20T) in Bi-2212 wires of several meters length, as well as longer pieces wound in coils, rarely exceeds 200A/mm. Moreover,(More)
Electron energy-loss spectroscopy (EELS) was combined with heat capacity measurements to probe changes of electronic structure and superconductivity in Mg(1-x)Al(x)B(2). A simultaneous decrease of EELS intensity from sigma-band hole states and the magnitude of the sigma gap was observed with increasing x, thus verifying that band filling results in the loss(More)
Niobium –titanium alloys have been widely used in superconducting applications since the early 1960s. The success of Nb – Ti has been due to its combination of excellent strength and ductility with high current-carrying capacity at magnetic fields sufficient for most applications. Moreover, these advantages are obtained with raw material and fabrication(More)
A magnetic interaction has been proposed as the dominant fluxon-defect interaction in conventional and artificial pinning center (APC) Nb–Ti, emphasizing the proximity length (ξN) of the pinning center as the important parameter for optimizing the high field critical current density. We have characterized APC composites containing 25 vol.% of Nb pins(More)
We describe a new type of bolometric detector for millimeter and submillimeter wavelengths. The detector is a variant of the Transition Edge Sensor (TES), which has recently been used to build bolometers. In this version of the TES, we couple radiation from a planar antenna to an absorbing normal metal film which is electrically connected to a(More)