Modeling Training in Nb3Sn Superconducting Magnets

Stress managed magnet designs allow to limit the strain and stresses applied to the conductor during assembly and operation. In canted cos(
$\theta$
) (CCT) designs, the conductor is wound around a mandrel: the impregnation process creates a bonding between the two, that can fail during magnet powering. The energy releases due to debonding are considered a potential cause of training quenches. In this study, we investigate these events modeling the mandrel-conductor interfaces by means of cohesive zone material models. The material properties were calibrated by means of measurements performed on representative interfaces, and the models were validated comparing the results with strain gauge measurements. A thermal model was used to compute the local temperature increase in the strands as a function of the energy released by debonding and frictional sliding across the newly formed interfaces. The result was then used to define a quench condition for the model, allowing to simulate the full training process of the CCT magnet. The obtained training curve is in reasonable agreement with the experimental results.