Specification of the ESS Accelerator Cryoplant

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 2.0 GeV, with a nominal current of 62.5 mA. The superconducting part of the accelerator is about 300 meters long and contains 43 cryomodules. The ESS accelerator cryoplant will provide the cooling for the cryomodules and the cryogenic distribution systeminterconnecting cryoplant and cryomodules. The cryoplant will cover three cryogenic circuits: bath cooling for the cavities at 2 K, the thermal shields at around 40-50 K and 4.5 K forced helium cooling for the power couplers. This paper describes project stages,the cryogenic architecture andthe design basis including cooling capacity, operation modes and interfaces. The important design choices comprising no liquid nitrogen pre-cooling,one integrated cold box, waste heat recovery and process control system strategy as well as the principles of evaluation are presented. All the topics above are implemented and addressed in the technical specification, which has been finished and issued in June 2014. That is a very important step in the development of the ESS cryogenics system.