Design of the Cryogenic Bypass Line for the SIS100 Synchrotron

This paper presents the selected aspects of a superconducting cryogenic bypass line (BPL) design, a part of the international Facility for Antiproton and Ion Research (FAIR) SIS100 cryogenic system, currently under construction in Darmstadt, Germany. Design, manufacturing, and installation of the superconducting cryogenic bypass line is a part of a Polish in-kind contribution to the FAIR project, realized by the Wroclaw University of Science and Technology. The BPL is dedicated to transferring liquid helium and AC electric current between SIS100 arc sections and superconducting quadrupole magnets located in warm straight sections of the synchrotron. A main innovative feature of the cryogenic bypass line is transferring the electric current and liquid helium in one vacuum vessel, while in other similar projects, namely, the Large Hadron Collider at CERN (CH) or the Tevatron at FermiLab (USA), those functions are separated. The coexistence of superconducting busbars and liquid helium process pipes in one limited space, as well as numerous additional functional and technical requirements, was a source of the serious design and production challenges described in the paper, including two designs of the internal suspension system based on steel rods and aramid cables.