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MSC Seminars
Key strategy in materials science to develop high Jc in Bi-2212 round wires and to realize affordable Fe-based high field superconducting wires
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Europe/Zurich
513/1-024 (CERN)
Description
Abstract
Future particle physics discoveries at the energy frontier rely on a next generation of high energy colliders of order 100 TeV. Such colliders require about twice the field possible from Nb-Ti, thus requiring new superconducting accelerator magnets of about 16 T field or beyond. Especially for long term vision in magnet developments, high temperature superconductors (HTS) are certainly very important. In this presentation, I will talk about the key nanostructural understandings in breakthrough for high Jc Bi-2212 round wires. I will also discuss about the scientific strategy for developing high Jc in polycrystalline Fe-based superconductors (FBS) so as to make them an alternative high field superconductor that can be far more affordable than Bi-2212 or REBCO. For both cases, the strong grain-to-grain superconducting connectivity is the crucial nanostructural factor for high Jc. In Bi-2212, strong a-axis grain growth which is induced by narrow filament cavities produces the quasi-biaxial grain texture to create the network of strongly coupled grain boundaries. On the other hand, FBS, particularly doped Ba(or Sr)Fe2As2 (122) have their GBs less obstructing against the supercurrent. We have found over several years of study that grain boundaries (GBs) in the highest Jc randomly oriented 122 samples have strong oxygen segregation at many GBs, demonstrating that a significant part of the GB problem in 122 is extrinsic, not intrinsic. Thus developing the methodology to make the GBs clean is highly desirable for realizing high Jc polycrystalline 122.