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Quench degradation limit of multifilamentary AgBi2Sr2CaCu2Ox round wires

Journal Article · · Superconductor Science and Technology
 [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)
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 the 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.
Research Organization:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Organization:
USDOE; USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Grant/Contract Number:
AC02-07CH11359
OSTI ID:
1258288
Alternate ID(s):
OSTI ID: 1236650
OSTI ID: 22531971
Report Number(s):
FERMILAB-PUB--16-216-TD; 1469367
Journal Information:
Superconductor Science and Technology, Journal Name: Superconductor Science and Technology Journal Issue: 3 Vol. 29; ISSN 0953-2048
Publisher:
IOP PublishingCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (1)

Numerical simulation of quench initiation and propagation in multi-filamentary Bi 2 Sr 2 CaCu 2 O x round wires at high magnetic fields journal April 2019

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