Specific Heats of Composite Bi2212, $\hbox{Nb}_{3} \hbox{Sn}$, and $\hbox{MgB}_{2}$ Wire Conductors

In this work, pulse calorimetry was used to measure the specihc heats of four superconducting materials at temperatures from 0 to 300 K and in magnetic helds from 0 to 14 T. Specihc heat measurements were performed on Bi2212 round wire samples with a two-dimensional random oriented single stack design, made by Supramagnetics Inc., and a conventional design made by Oxford Superconductor. Specihc heat measurements were also performed on a copper-stabilized MgB2 wire sample and a rod-in-tube type Nb3Sn wire sample made by Hyper Tech Research, which were subject to their appropriate heat treatments. All wire sample lengths were ~3 mm. The specihc heats of the Bi2212 samples were relatively independent of applied held; the zero held specihc heat of the two-dimensional random oriented single stack sample increased from 0.155 mJ/g-K at 4 K to 254 mJ/g-K at 250 K. At 2 K, the specific heat of the Nb
₃
Sn rod-in-tube strand increased from 0.0257 mJ/g-K at 0 T to 0.0716 mJ/g-K at 14 T. In zero held the specihc heat of the MgB
₂
sample increased from 0.623 mJ/g-K at 4 K to 382 mJ/g-K at 250 K.