Liquid hydrogen for cold neutron production at European Spallation Source ERIC

The European Spallation Source (ESS) will be a 5 MW, long-pulsed spallation neutron research facility. One of the key feature is that ESS will use liquid hydrogen as a moderating media for the cold neutrons. The hydrogen operates at cryogenic temperatures at approximately 17K. The challenge for the cryogenic system is to meet the high neutronic heat load and maintain a narrow operational span. To handle the large variations in heat load a special developed pressure control device is designed. To maintain the hydrogen operating temperature, a Helium refrigerator with unique capabilities to control temperature in the hydrogen system is developed. It also has the capacity to react and compensate for a lower heat load than anticipated in the moderator system on short notice. Another key feature is the Ortho-Para catalyst and the in line OP measurement that verifies the high para content at all time, to optimize neutronic performance. This paper describes the process development, planned commissioning and operation of the cryogenic hydrogen and ancillary systems