8-kA HTS current leads for 1.9 K test facility at KEK

A pair of 8 kA HTS current leads for an accelerator magnet test facility at KEK has been designed and fabricated. The HTS current lead is composed of a copper section in the high temperature region and a HTS section in the low temperature region. The copper section of the lead consists of copper wires bundled into a stainless steel pipe. The HTS section consists of 12 HTS tape units made by Bi2223/Ag-1 at% An tapes arrayed onto the outer surface of a stainless steel tube with a diameter of 54 mm. The whole length and the maximum diameter of the lead are 1465 mm and 71 mm, respectively. The entire length of the current lead is cooled with helium gas. The design heat load and the helium gas flow rate of the lead in a steady state 8 kA-operation are less than 0.2 W and 0.4 g/sec, respectively and temperatures of the high and low temperature ends of the HTS section under the condition are 50 K and 4.4 K, respectively. The thermal performance test was carried out, and the results agreed well with the calculated values. So, we verified the validity of the thermal analysis and design. The corresponding heat load is estimated to be 0.15 W. These values of 0.4 g/s and 0.15 W are only 89% and 1.5% of the conventional gas cooled current lead, respectively.