ESS accelerator cryogenic plant

The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration at Lund, Sweden. The ESS accelerator will deliver protons with 5 MW of power to the target at 2.5 GeV, with a nominal current of 50mA. The superconducting section of the ESS accelerator consists of a total of 208 SRF cavities in cryomodules (CMs) cooled with superfluid helium to 2K. The CM contains one thermal radiation shield operating from 40 to 50K. Additionally, 4.5-K gas helium is used to provide forced cooling to the fundamental power couplers for the cavities. The cryogenic cooling for these CMs is provided by one cryogenic plant connected to CMs via a cryogenic distribution line. This article describes the requirements and preliminary design decisions for the ESS accelerator cryoplant. The expected capacity, temperature levels and operating modes are given. Design choices to address important issues of turn-down capability, high availability, and timely restart after plant trips are discussed. Procurement options and schedules are described.