Effect of thermo-mechanical stress during quench on Nb/sub 3/Sn cable performance

Abstract

Several high field magnets using Nb/sub 3/Sn superconductor are under development for future particle accelerators. The high levels of stored energy in these magnets can cause high peak temperatures during a quench. The thermo-mechanical stress generated in the winding during the fast temperature rise can result in a permanent damage of the brittle Nb/sub 3/Sn. Although there are several studies of the critical current degradation of Nb/sub 3/Sn strands due to strain, little is known about how to apply the strain limitations to define a maximum acceptable temperature in the coils during a quench. Therefore, an experimental program was launched, aimed at improving the understanding of the effect of thermo-mechanical stress in coils made from brittle Nb/sub 3/Sn. A first experiment, reported here, was performed on cables. The experimental results were compared to analytical and finite element models. The next step in our experimental program will be to repeat similar measurements in small racetrack coils and later in full size magnets.