Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab)
- North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
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 Tallowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, JE, 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, Tallowable is greater than 450 K. With increasing axial tensile stress, σa, however, Tallowable decreases nonlinearly, dropping to 280 K for σa = 120 MPa and to 160 K for σa = 145 MPa. Tallowable(σa) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. Tallowable(σa) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing Tallowable, and therefore has important engineering value. It is also shown that Tallowable(σa) 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:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)
- Grant/Contract Number:
- AC02-07CH11359; AC02-05CH11231
- OSTI ID:
- 1423259
- Alternate ID(s):
- OSTI ID: 1334196; OSTI ID: 1574317
- Report Number(s):
- FERMILAB-PUB-17-642-TD; 1512387; TRN: US1801726
- Journal Information:
- Superconductor Science and Technology, Vol. 30, Issue 2; ISSN 0953-2048
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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