The influence of Nb3Sn strand geometry on filament breakage under bend strain as revealed by metallography

摘要: The non-Cu critical current density of Nb3Sn strands has been pushed towards 3000 A mm−2 (12 T, 4.2 K) by increasing the Sn content and reducing inter-filamentary Cu. We compare susceptibility to A15 filament breakage (under 0.5% bend strain) new high-Jc internal conductor geometries with both powder-in-tube (PIT) low hysteresis loss distributed ITER designs. In all but PIT designs, there was significant on tensile side strand cross-section little if any evidence for cracking compressive side. Where is Cu remaining after reaction highest frequency observed at edges packs. This suggests that most likely occur where filaments receive less mechanical support from filament-Cu matrix. very high Jc strands, individual Nb coalesce into large tubes during reaction, can across entire sub-element. design composite, did not strain. At 0.6% strain cracked in regions.