Pure bending behavior of Nb 3 Sn wire over a wide range of bending has been characterized. A previously developed test device designed to apply variable bending strains to Nb 3 Sn strands using a beam style sample holder was used. Based on finite element and experimental investigations, two sample holder beams were developed to cover pure bending strains up to 1.25% for ITER-type Nb 3 Sn wires. These newly designed beams were optimized to apply consistent and uniform pure bending strains to Nb 3 Sn strands over the entire bending range. Their performance was evaluated by testing two ITER-type Nb 3 Sn wires including one internal tin and one bronze route. The internal tin strands experienced around 55% critical current degradation at 1.25% bending strain while the critical current of the bronze route strands were only reduced by 40%. Upon removal of the bending load, the internal tin wires experienced significant permanent degradation whereas the bronze route wires were completely reversible. These critical current results were evaluated and explained using an existing integrated model accounting for neutral axis shift, current transfer length, filament breakage and uniaxial strain release under pure bending loads.
Abstract--We report the operating characteristics of the monolithic SMES conductor designed for operation at 60 kA, 5.1 tesla in a 1.8 K bath of subcooled helium.Details of the experimental arrangement and procedures are presented as background.At 1.85 K the conductor has been operated up to 75 kA, and with maximum field conditions of 4.25 tesla.
Conductor performance is compared to the load line and design point of the Engineering Test Model (ETM).Transient stability is also demonstrated.Maximum conditions experienced by the conductor were limited by facility operation rather than by the conductor i t s e l f .
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