Investigation of considerable stability increase of composite superconductors doped with extremely large heat capacity substances

The influence of doping NbTi-based composite superconductors with extremely large capacity substances (LHCSs) on their stability towards electromagnetic disturbances was investigated both experimentally and numerically. The samples comprised of standard NbTi 0.85 mm diameter wires soft-soldered with copper wires of the same diameter that contained one or several LHCS filaments. Some compounds (CeCu6, HoCu2, CeAl2, PrB6, Gd2O2S) with extremely large heat capacities at 4.2 K were introduced into the copper matrix by the powder-in-tube (PIT) method. The comparison sample (without LHCS doping) was made by soft-soldering of the 0.85 mm diameter NbTi wire with the copper wire without any LHCSs. The samples were placed in a transverse magnetic field and at several values of the transport current were subjected to longitudinal electromagnetic disturbances. The typical disturbance times varied in a broad range: from 50 μs to 1.2 ms. It was found that the critical current densities for the samples with LHCS doping were considerably higher than those for the comparison sample. It was also shown that the gain in stability remains even when the samples were directly liquid helium (LHe) cooled