Implications of the strain irreversibility cliff on the fabrication of particle-accelerator magnets made of restacked-rod-process Nb3Sn wires

Summary

This materials science study investigates the strain irreversibility cliff phenomenon in restacked-rod-process Nb₃Sn superconducting wires destined for the High-Luminosity LHC upgrade at CERN. The authors introduce a coupled electro-mechanical stability criterion accounting for both strain and electrical properties, and demonstrate that reduced-tin billet designs offer a significantly wider heat-treatment temperature window (680–695 °C) compared to standard-tin formulations, thereby permitting practical fabrication of magnets that maintain both mechanical integrity and the required residual resistivity ratio above 150. The findings suggest operational specifications for future LHC magnet production using specific wire geometries and processing parameters.

Key measures

Intrinsic irreversible strain limit (ε_irr,0), residual resistivity ratio (RRR), critical current, heat-treatment temperature (θ), strain-induced degradation

Outcomes reported

The study characterised the strain irreversibility cliff (SIC) phenomenon in Nb₃Sn superconducting wires and developed an electro-mechanical stability criterion balancing strain integrity and residual resistivity ratio requirements for Large Hadron Collider magnet conductors.

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