Training in test samples of superconducting cables for accelerator magnets

In the critical current measurement of some high-current NbTi cables, the samples have to be `trained´ by repeated quenching to obtain a usable voltage-current curve for I_c determination. This training behavior is most pronounced when the applied field is perpendicular to the wide face of the conductor and is strongly dependent on the copper-to-superconductor ratio and the clamping pressure. Data are given for SSC (Superconducting Super Collider) prototype cables as well as for HERA production conductors. Although a quantitative understanding of the experimental data is still lacking, some speculations regarding stability are presented