Design and thermal behavior of vapor cooled current leads for the detector and IR magnets in BEPC II

A superconducting detector magnet and two sets of interaction region (IR) magnets are adopted in the upgrade project of Beijing Electron and Positron Collider (BEPC II). The operating currents of these magnets differ from 3.6 kA to 24 A. Totally 13 pairs of vapor cooled current leads (VCCL) were designed and fabricated for these magnets. After the successful test experiments, all the VCCL have been installed to BEPC II system and operate properly. This paper presents the detail of the design and the experimental behavior of these VCCL.