Liquid helium boil-off measurements of heat leakage from sinter-forged BSCCO current leads under DC and AC conditions

Liquid helium boil-off experiments were conducted to determine the heat leakage rate of two sinter-forged BSCCO 2223 high-temperature superconductor current leads. The experiments were carried out under both DC and AC conditions and with and without an intermediate heat intercept. Current ranges were 0-500 A for DC tests and 0-1,000 Arms for AC tests. The leads were self-cooled. The results show that magnetic hysteresis (AC) losses for both the BSCCO leads and for a low-temperature superconductor current jumper were small for the current range covered in the present experiments. It has been demonstrated that significant reduction in heat leakage rate (liquid helium boil-off rate) is realized by using BSCCO superconductor leads. At 100 A, the measured heat leakage rate of the BSCCO/copper binary lead was ∼29% of that of a conventional copper lead. Further reduction in liquid helium boil-off rate was achieved by using an intermediate heat intercept. For example, At 500 A, the measured heat leakage rate of the BSCCO/copper binary lead was only 7% of that of the conventional copper lead when an intermediate heat intercept was employed