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BigBOX – a Nb3Sn demonstrator coil – reaches maximum performance without training

BigBOX, one of the CHART/MagDev R&D vehicles, is an Nb3Sn racetrack in a stress-management structure. Following one of our developments in impregnation systems, the first BigBOX was impregnated with paraffin wax. The primary goal of this experiment is to study the training behavior of a stress-managed coil-block under high magnetic fields and stress on the conductor.

The PSI and US-MDP/BNL teams collaborated to integrate the mechanically and magnetically coupled coil into BNL’s common-coil dipole DCC017. The demonstrator was designed and constructed at PSI in 2022 and underwent testing at BNL in 2023.

With background fields of approximately 7, 8, and 9 T, BigBOX consistently reached its predicted limit without any stress-induced performance reduction. During the experiment, the background field was varied, but no reduction in performance due to stress was observed. With the maximum background field, the computed total peak field on the conductor reached 12.3 T, and the maximum computed stress in the cross-section was 169 MPa.


Based on these results, we are encouraged to continue progressing along the CHART/MagDev roadmap toward stress-managed LTS and Hybrid LTS/HTS common coils.