We measured from 5 to 300 K the thermal conductance of different superconducting Bi-2212 thin rods and one superconducting module integrating a hybrid current lead based on such rods. The conductance values of the rods are lower than the measurable limits of the set-up and a detailed evaluation of the heat losses is required. The analysis of the heat exchanges permits to introduce a correction function to the measured values and allows to study low thermal conductivity materials. The dependence of the thermal conductivity of Bi-2212 rods on the sample microstructure is analyzed after this correction. We calculate analytically the time required to reach the steady-state for long bars for which extended relaxation times are expected. From the measured conductance data we estimate the heat load introduced by the current lead into a cryogenic bath in static conditions.

The authors are indebted to the Spanish Ministerio de Educación y Ciencia and to FEDER for financial support through the projects MAT2004-03395-C02-02 and MAT2002-04121-C03-02. Eva Natividad thanks the Spanish CSIC and the European Social Fund for her I3P contract.

10 pages, 7 figures, 1 table.

Peer reviewed