Proton Improvement Plan II Cryogenic Distribution System thermodynamic design

The Proton Improvement Plan II (PIPII) is a superconducting linear accelerator being built at Fermilab that will provide 800 MeV proton beams for neutrino production. The Linac requires cooling at 80 K, 5 K, and 2 K temperatures, which will be provided by cryogenic helium produced by a Helium Cryoplant and distributed by a Cryogenic Distribution System (CDS). Based primarily on the Linac heat load requirements at each temperature and the allowable pressure drop, we have made a preliminary thermodynamic design of the CDS. The design also incorporates special requirements such as controlled and or fast cooldown of the superconducting RF cavities and their dual maximum allowable working pressure. This paper presents the overall features of the PIPII CDS, sizing of helium process circuits, different operating modes, and calculated mass flow capacities that cater to these operating modes.