Considerable stability increase in superconducting windings doped with extremely high specific heat substances

The influence of some rare-earth based intermetallic compounds with extremely high specific heat capacities on the transient stability of NbTi superconducting windings was experimentally investigated. The experiments were carried out with three NbTi wire wound small round coils doped with CeCu₆, HoCu₂, and (for comparison) with boron nitride usually used as an epoxy resin filler. The intermetallic compounds, CeCu₆ and HoCu₂, were introduced as filling powders into an epoxy resin based composite in a wet winding process. Doping of about 5.7 vol.% of such compounds increases minimum quench energies several times even for short (of order of 1 ms) electromagnetic disturbances. The first results are also reported of the training history comparison in three NbTi Rutherford cable wound oval-shaped windings doped with half amount (about 2.9 vol.%) of the same compounds. It is shown that even such doping is very helpful in increasing of the first quench current. The prospects and most promising applications are briefly discussed.