Speaker
Description
Addressing an NHMFL goal of developing high temperature superconductor (HTS) technology applied toward nuclear magnetic resonance (NMR) at high fields (~1 GHz), the work presented here focuses on the finite element analysis (FEA) led designs of Bi2Sr2CaCu2O8-x (Bi-2212) round wire prototype coils. With the goal of an HTS insert coil that produces a significant portion (>20 %) of a combined low temperature superconductor (LTS) & HTS magnet system’s total field, the required operating conditions approach the performance limits of the insert coil. Composed of filaments in a pure Ag matrix within an Ag-alloy sheath, Bi-2212 RW conductors experience mechanical strain generated from large Lorentz forces that stress the coil, and at the target high fields the integrity of the Bi-2212 superconducting filaments are pushed near their critical strain limits. Thus, a series of prototype coils has been designed to systematically address coil-level reinforcement, via stress/strain management schemes. Prototype designs are constrained to the size of the over-pressure furnace, in which the Bi-2212 coils are reacted, as well as the available size and field strength of the LTS outsert, in which experimental tests are performed. Multiphysics FEA was used to set prototype coil dimensions within these constraints, large enough to strain the conductors during in-field experimental tests to values similar to seen in the NMR demonstration coil, yet small enough to not become prohibitively expensive. Details of the complexity of the models, a predicted critical surface describing the prototype performance limits, and some experimental results are reported. Overall, high detail modeling has proven invaluable, and successful coil-level stress/strain management provides a roadmap towards making Bi-2212 a viable conductor for high field, high homogeneity magnet technologies.
| Submitters Country | United States of America |
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