--Thermal conductivity of bulk high temperature superconducting materials is a very important property in the current lead applications because it determines the heat load of the lead at the low temperature end. The thermal conductivity of BSCCO-2212 superconducting material has been measured between 10 and 130 K.Our results compare favorably with other published results. The thermal contact conductance between a joint of BSCCO-2212 and copper has also been measured. Our results indicate that although this kind of joint provides a relatively poor thermal interface, the electrical resistance is small. This joint is still a good choice for making a easy joint which requires both thermal and electrical interfacing. I . IntroductionSoon after the discovery of high temperature superconducting materials, it was realized that they have advantages as current leads for conventional superconducting magnets operating at liquid helium temperature. The objective of a current lead design is to minimize the heat leak introduced by the transmission of a given current into the cryostat. This heat comes from two sources: it is conducted down the lead from room temperature and it is generated within the lead by ohmic loss. One therefore wishes to minimize both the thermal conductivity and electrical resistance of the lead material. For a high temperature superconducting current lead, the material of the upper stage (between the intermediate temperature and the room temperature) is usually conventional copper while superconducting material is used in the lower stage. When this lead is operating in the superconducting state, no heat is generated in the lower stage. Because of the relatively low thermal conductivity as compared to metals and no heat is generated in the superconductor part of the lead, high temperature superconducting current leads have the potential to reduce the heat load at liquid helium temperature to 1/5 of that of the best possible conventional current leads. Numerous investigations have been carried out in the last few years to address this possibility [l], [2].The heat conduction through a high temperature superconductor which spans the temperature range from To to (1) A Q = L jkdT where A is the cross section area and L is the length of the conductor, k is the thermal conductivity of the material, and TO where T(T0, 4.2K) = kdT is called the thermal 4.2K conductivity integral. For a given operating current, the heat load may be reduced by either a decrease in the thermal conductivity integral r, or by an increase in the critical current density, since in the later case a fixed current will allow a decrease in area A.Thermal conductivity of high temperature superconducting materials have been reported in many papers (11, [21, [41, [61. The typical values for thermal conductivity integral are as follows: for sintered BSCCO-2223 material, r(77K, 4.2K) = 80-130 W/m; for melt cast BSCCO-2212 material, r(77K, 4.2K) = 103 W/m; for sintered YBCO material, r(77K. 4.2K) = 234 W/m. Samples prepared by differe...

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As part of the U.S. Department of Energy's Superconductivity Technology Program, Argonne National Laboratory and Superconductivity, Inc., are developing high-temperature superconductor (HTS) current leads for application to micro-superconducting magnetic energy storage systems. Two 1500-A HTS leads have been designed and constructed. The performance of the current lead assemblies is being evaluated in a zero-magnetic-field test program that includes assembly procedures, tooling, and quality assurance; thermal and electrical performance; and flow and mechanical characteristics. Results of evaluations performed to date are presented.

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