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This content will become publicly available on February 2, 2017

Title: Quench degradation limit of multifilamentary AgBi2Sr2CaCu2Ox round wires

Understanding safe operating limits of composite superconducting wires is important for the design of superconducting magnets. Here we report measurements of quench-induced critical current density Jc degradation in commercial Ag/Bi2Sr2CaCu2Ox (Bi-2212) round wires using heater-induced quenches at 4.2 K in self magnetic field that reveal a general degradation behavior. Jc degradation strongly depends on the local hot spot temperature Tmax, and is nearly independent of operating current, the temperature gradient along the conductor dTmax/dx, and the temperature rising rate dTmax/dt. Both Jc and n value (where n is an index of the sharpness of the superconductor-to-normal transition) exhibit small but irreversible degradation when Tmax exceeds 400-450 K, and large degradation occurs when Tmax exceeds 550 K. This behavior was consistently found for a series of Bi-2212 wires with widely variable wire architectures and porosity levels in the Bi-2212 filaments, including a wire processed using a standard partial melt processing and in which Bi-2212 filaments are porous, an overpressure processed wire in which Bi-2212 filaments are nearly porosity-free and that has a Jc(4.2 K, self field) exceeding 8000 A/mm2, and a wire that has nearly no filament to filament bridges after reaction. Microstructural observations of degraded wires reveal cracks in themore » Bi-2212 filaments perpendicular to the wire axis, indicating that the quench-induced Ic degradation is primarily driven by strain. These results further suggest that the quench degradation temperature limit depends on the strain state of Bi-2212 filaments and this dependence shall be carefully considered when engineering a high-field Bi-2212 magnet.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); North Carolina State Univ., Raleigh, NC (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. North Carolina State Univ., Raleigh, NC (United States)
Publication Date:
OSTI Identifier:
1258288
Report Number(s):
FERMILAB-PUB--16-216-TD
Journal ID: ISSN 0953-2048; 1469367
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 29; Journal Issue: 3; Journal ID: ISSN 0953-2048
Publisher:
IOP Publishing
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS