Training Studies of Epoxy-Impregnated Superconductor Windings

Instability in Super-Conducting Magnets — A Review of Heat Input from Mechanical Disturbances

“…Ekin et al [24] confirmed the beneficial effects on training of potting with wax and of 4 K pre-strain. The general conclusion from this work was that the observed behaviour could be explained by a "stress relief model in which the training is assumed to arise from a series of local fractures at stress concentrations".…”

“…Ekin et al [24,31] carried out a number of experiments on small epoxy impregnated magnets. These small solenoids could be energised in a 5T-background field and subjected to large hoop strains.…”

“…Using the same apparatus, Ekin et al [24] examined a number of other variables in the coil manufacturing process. Short 'milled' glass fibres were included within the coil, prior to impregnation with the aim of decreasing the thermal contraction of the resin and so reducing cracking.…”

“…In both reports [24,31] it was assumed that epoxy fracture is the mechanical event that is occurring at stress concentrations and releasing energy. The precision with which Ekin et al were able to reproduce training quenches and the precise 'memory effect' of pre-strained coils is an important factor.…”