ESS Target Moderator Cryogenic Plant : Process Design

The European Spallation Source (ESS) project is a neutron spallation source facility currently under construction outside Lund, Sweden. The ESS accelerator will deliver a 5 MW proton beam to a spallation target at 2.0 GeV with a nominal current of 62.5 mA to generate fast neutrons. The cooling of the spallation target with liquid hydrogen circulating in the cryogenic moderator system (CMS) transforms these fast neutrons to slow neutrons which compose the useful radiation. The liquid hydrogen itself is cooled by a helium refrigeration cycle, the target moderator cryogenic plant (TMCP) providing cooling capacity in a wide range of 2.3-31.8 kW at 15-20 K. TMCP's maximum cooling capacity of 31.8 kW will make it the world's largest plant of its kind. The TMCP project is challenging in many ways. The heat load of the CMS has to be removed precisely all the time by the TMCP. In addition the TMCP has to meet highly dynamic requirements as the heat load ceases quickly in case the proton beam trips off. Furthermore transitions within the wide cooling capacity range have to be achieved seamlessly. In this talk the progress of the TMCP engineering is summarized. Process design, control strategies, machine concept and layout are presented.