Showing papers by "Evangelos Trifon Laskaris published in 1997"

Cooling arrangement for a superconducting coil

Abstract: A superconducting device, such as a superconducting rotor for a generator or motor. A vacuum enclosure has an interior wall surrounding a cavity containing a vacuum. A superconductive coil is placed in the cavity. A generally-annularly-arranged, thermally-conductive sheet has an inward-facing surface contacting generally the entire outward-facing surface of the superconductive coil. A generally-annularly-arranged coolant tube contains a cryogenic fluid and contacts a generally-circumferential portion of the outward-facing surface of the sheet. A generally-annularly-arranged, thermally-insulative coil overwrap generally circumferentially surrounds the sheet. The coolant tube and the inward-facing surface of the coil overwrap together contact generally the entire outward-facing surface of the sheet.

Compact MRI superconducting magnet

Abstract: A closed magnetic resonance imaging (MRI) magnet has a single superconductive coil assembly (12) including a coil housing (14) containing a cryogenic fluid dewar (28) containing a pair of longitudinally-outermost impregnated superconductive main coils (32,34) and at-least-one cryostable additional superconductive coil such as a pair of additional main coils (42,44), a pair of bucking coils (36,38), and/or a pair of shielding coils (46,48). An open MRI magnet has two spaced-apart superconductive coil assemblies and an imaging volume have a centre. Each coil assembly has a cryostable superconductive main coil and an impregnated bucking coil with the impregnated bucking coil being the closest superconductive coil to the centre of the imaging volume.

Mechanical stabilization of BSCCO-2223 superconducting tapes

Abstract: A system to provide mechanical stabilization to high temperature BSCCO-2223 superconducting tape by laminating 0.081 mm thick, spring hard, copper foil to both sides with lead-tin eutectic solder has been successfully optimized. This system has been applied as a method to create a strong, windable composite with a minimum of critical current (I/sub c/) degradation. The "as received" conductor is evaluated for physical consistency of width and thickness. Electrical degradation in the strengthened tape as a result of lamination was found to average 24 percent. This was less than the degradation that would have occurred in an unstrengthened tape during subsequent insulation and coil winding processes. The copper can double the ultimate tensile strength of the pure silver tapes. Additionally, pure silver and dispersion strengthened silver matrix tapes are laminated with 0.025 mm thick copper and 304 stainless steel foil to investigate minimization of the cross sectional area of the strengthening component. The stainless steel can increase the UTS of the pure silver tapes sixfold. Mechanical properties and critical currents of these tapes are also reported both before and after strengthening. The I/sub c/ is also measured as a function of strain on the laminated tapes.

Development and fabrication of a Bi-2223 racetrack coil for generator applications

Abstract: The development and fabrication of a layer-wound, epoxy-impregnated Bi-2223 high-temperature superconducting (HTS) racetrack coil which generates 40000 ampere-turns of magnetomotive force (MMF) at 25 K is described The coil was wound using Ag-sheathed Bi-2223 tape conductor laminated with copper foils for strength enhancement and insulated using a paper-wrap method After epoxy impregnation, the coil was tested over a range of 16-25 K in a vacuum dewar using a closed-cycle helium refrigeration system Descriptions of the tape lamination and insulation processing, the coil winding and impregnation, and the experimental test setup are given

Test results for a Bi-2223 HTS racetrack coil generator applications

Abstract: Testing, results and analysis of a Bi-2223 model superconducting generator coil produced under the DOE Superconductivity Partnership Initiative are presented. The test arrangement enables coil energization with DC and transient currents over a range of operating temperatures to explore coil performance under conditions analogous to those that would be experienced by a superconducting generator field coil. Analytic calculations of coil AC and ohmic losses and temperature rise compare well with experimental measurements. Good performance is predicted for a typical three-phase fault condition. Coil steady-state and transient performance can be predicted with confidence for full scale superconductor application.