Specification and design of a 2 K helium system for cryomodule and cavity tests at FRIB

The Facility for Rare Isotope Beams (FRIB) will be a new User Facility for Nuclear Science. The facility is funded by the Department of Energy (DOE) Office of Science and Michigan State University (MSU) and will be constructed on the campus of MSU. The main accelerator for the FRIB project will be a superconducting linac constructed of 52 cryomodules, housing 344 superconducting radio frequency (SRF) cavities. All of the SRF cavities must be operated at superfluid helium temperatures of 2 K. During FRIB fabrication, and prior to the commissioning of the FRIB cryoplant, all cavities and cryomodules must be tested as part of the FRIB quality assurance program. To meet the requirements of FRIB production, upgrades to the existing SRF infrastructure at the National Superconducting Cyclotron Lab (NSCL) must be designed and commissioned. These upgrades include: two additional test Dewars, a FRIB cryomodule testing bay, and a cryogenic system capable of supporting the 2 K cryogenic load, including sub atmospheric pumps, heat exchangers, and JT valves. Transfer lines connecting these new additions will also be designed and fabricated. This paper describes these new systems and show that they will meet FRIB requirements as well as maintaining flexibility for future changes.