Performance test of current lead cooled by a cryocooler in low temperature superconducting magnet system

• The current lead with multi-contact connector in the joint was fabricated for performance test.
• The electrical contact resistance in the joint was measured during magnet charging.
• The resistances of the joint were 0.4–0.9 mΩ for 40–80 K.
• The heat generation due to electrical contact resistance was reduced below 1 W by multiple spring louvers.

In a low temperature superconducting magnet system, heat leakage through current leads is one of the major factors in cryogenic load. The semi-retractable current lead is a good option because the conductive heat leakage can be eliminated after the excitation of the magnet. It is composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and an HTS element, conducting the current down to liquid helium temperature. The normal metal element is disengaged from the HTS element through the multi-contact connector without disturbance to the insulating vacuum space and without requiring complete removal of the normal metal element. The intermediate block with a lockable set point is thermally connected to the first stage of cryocooler and carries current through a strip of louvered material. The electrical contact resistance of multi-contact connector in the intermediate block is measured during magnet charging process. The effects of current level as well as operating temperature on the heat generation in the joint block are also discussed.