Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: II. High-strength, laminated Ag-sheathed Bi-2223 tapes
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
In article I of this series, we described a spiral coil quench technique for probing the influence of the superconductor stress and strain state during normal operation on its margin to degradation during a quench and applied to a Bi-2212 round wire. Here we extend this technique to study the failure mechanisms and limits of high-strength Bi-2223 tapes experiencing a quench while carrying a large current in a high magnetic field. In contrast to Bi-2212 magnets made via a wind-and-react technique for which bending strains can be ignored, Bi-2223 magnets are made with a react-and-wind technique for which bending strain is significant. The critical tensile stress of Bi-2223 tapes (type HT-NX) decreases from >440 MPa for straight samples to 185 MPa after being bent to a diameter D of 50 mm. For HT-NX tapes with D = 50 mm, the quench degradation limit, measured using maximum allowable temperature during a quench T allowable, is greater than 300 K for axial tensile stress $${\sigma }_{a}$$ < 94 MPa; it decreases with increasing tensile axial stress $${\sigma }_{a}$$ nonlinearly, dropping to 230 K for $${\sigma }_{a}$$ = 125 MPa. T allow able $$({\sigma }_{a})$$ experimental data at D = 50 mm is consistently predicted by a general strain model that assumes that quench degradation in NX/Bi-2223 is driven by axial tensile strain in Bi-2223 filaments exceeding the irreversible strain limit. The T allowable $$({\sigma }_{a})$$ is then predicted for various D including D = 80 mm important for NMR magnets. In conclusion, the given T allowable $$(D,{\sigma }_{a})$$ is easy to use and important for finding the balance between operation stress, and therefore magnetic field generation efficiency, and operation margin when designing a superconducting magnet using Bi-2223 tapes.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1466715
- Alternate ID(s):
- OSTI ID: 22905461
- Journal Information:
- Superconductor Science and Technology, Journal Name: Superconductor Science and Technology Journal Issue: 1 Vol. 31; ISSN 0953-2048
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English