Effect of a thermal fluctuation caused by a proton beam injection on the ESS large-scale 20 K helium refrigeration system

Abstract

In the European Spallation Source (ESS), a large-scale 20 K helium refrigeration system with a cooling capacity of 30.2 kW at 15 K, which is called Target Moderator CryoPlant (TMCP), has a function to cool the cryogenic moderator system (CMS) that provides subcooled liquid hydrogen with a temperature of 17.5 K to two hydrogen moderators (to be increased to four in the future) and remove nuclear heating generated of 6.7 kW and 17.2 kW for two and four moderators at the proton beam power of 5 MW. The commissioning has been completed by December 2022. We studied the stability of the TMCP operation when the heat load of 5.92 kW and 17.5 kW was rapidly applied and how to mitigate the propagation of the temperature fluctuation in order not to affect the CMS supply temperature.