Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires
- Fermilab; LBL, Berkeley; North Carolina State U.
- Fermilab
- Natl. High Mag. Field Lab.
- North Carolina State U.
- Fermilab; LBL, Berkeley
The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, J E, of 550 A mm−2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. It is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.
- Research Organization:
- Natl. High Mag. Field Lab.; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); North Carolina State U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- US Department of Energy
- Grant/Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1423259
- Alternate ID(s):
- OSTI ID: 1334196
OSTI ID: 1574317
- Report Number(s):
- FERMILAB-PUB-17-642-TD; oai:inspirehep.net:1512387
- Journal Information:
- Supercond.Sci.Technol., Journal Name: Supercond.Sci.Technol. Journal Issue: 2 Vol. 30
- Country of Publication:
- United States
- Language:
- English
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