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Title: Microscopic origin of quench training in Nb3Sn accelerator magnets
Plain: Each premature quench lets the magnet reach a slightly higher current the next time, which suggests that small mechanical events in the coil release heat, but which events and where is not established.
Precise: Nb3Sn dipoles and quadrupoles operating at 1.1e5 to 1.5e5 G often require tens of training quenches to approach 80 to 90 percent of the conductor short-sample limit. Identify the energy-release events that start training quenches (epoxy cracking, conductor-insulation debonding, stick-slip friction at coil-structure interfaces), their energy spectrum relative to the minimum quench energy of the cable, and a model that predicts the training curve from coil prestress and material properties.
Settled by: Acoustic-emission and quench-antenna localization of initiating events across the training of several magnets, matched by a mechanical-thermal model that predicts the training curve of a new magnet before it is tested.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: Acoustic-emission localization of events during training was reported from 2015 onward; no model predicts training curves (moderate confidence, not rechecked for 2024-2026).
Posed since: (empty)