Development of 4kA Current Leads Using Stacked REBCO Tapes for BESIII Detector Magnet

For the Beijing Spectrometer III (BESIII) superconducting solenoid magnet (SSM) backup valve box upgrade project, a pair of 4kA HTS current leads was designed, manufactured and tested. The baseline design of the current leads adopted a stacked REBCO (Rare-Earth Barium-Copper-Oxide) conductor solution to achieve a lower thermal load at 4 K, improve the stability of the magnet, and meet the requirements in the upgrade project such as leaving the existing cryogenic system and the internal space of the valve box unchanged. Owing to the adoption of REBCO conductor, the heat leakage was effectively controlled.Construction of offline test platform and a preliminary test result are discussed, verified the current capacity of the current lead prototype. The development of a novel soldered stacked REBCO conductor is also described.