BEAMSTopic

Training and field limits of superconducting accelerator magnets

The magnets that steer high-energy beams are superconducting coils that often lose superconductivity (quench) below their design current and reach it only after many repeated quenches, called training. Why they train, and what limits their field, is not understood well enough to design around.

Why it matters

Reachable dipole field and training time set the energy reach and cost of future hadron colliders.

Review

D. Schoerling, A. V. Zlobin (editors), Nb3Sn Accelerator Magnets: Designs, Technologies and Performance, Springer, 2019. https://doi.org/10.1007/978-3-030-16118-7 reference checked

Proof

Signed record: a83e07dd6840…
Public log: Entry 74, in checkpoint 2,123
Bitcoin date: Block 969,698, 2026-10-03

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3 problems

Field errors from screening currents in REBCO accelerator magnets
Open

Magnets wound from flat high-temperature superconducting tape carry circulating currents inside the tape that distort the guiding field and drift in time.
Transverse-stress limit for irreversible degradation of Nb3Sn cables
Open

Nb3Sn is brittle, and the huge magnetic forces in a high-field magnet squeeze the cable until its ability to carry current is permanently damaged; where that threshold lies and what breaks first is uncertain.
Microscopic origin of quench training in Nb3Sn accelerator magnets
Open

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.

Training and field limits of superconducting accelerator magnets

Why it matters

Review

Proof

3 problems

Field errors from screening currents in REBCO accelerator magnets

Transverse-stress limit for irreversible degradation of Nb3Sn cables

Microscopic origin of quench training in Nb3Sn accelerator magnets