Analysis on vapor cooled current lead structures for the SuperKEKB IR SC correction coils

To energize the 40 superconducting (SC) correction coils of 50 A in the SuperKEKB interaction region (IR) magnet system, a compact 8-lead unit with two vapour cooled current lead structures is proposed. The theoretical derivation and solution of the general thermal balance equation based on one dimensional lead model are introduced in this paper. A numerical integration method to estimate the material optimum shape factor is presented, in which three materials are investigated for our R and D. Two structures are designed and their thermal and flow conditions are theoretically analyzed in this paper. The value of the heat transfer efficiency between helium and lead assumes minimum at the cold end and is calculated at 5 K for a conservative estimate. The influence on the heat leak to the cold end will be discussed. (author)