Progress of the ESS monolith design and engineering solutions for target and moderator systems

The on-going project for construction of the European Spallation Source (ESS), the 5 MW long-pulsed neutron research facility in Lund, Sweden, has entered the phase in which design work and development are focused on realising solutions that shall satisfy well-defined requirements. The Target Station, which converts the pulsed proton beam delivered by the linear accelerator to cold and thermal neutron beams tailored for neutron science applications, consists of several systems. Each of these elements offers unique design challenges for the engineering teams both in terms of providing the necessary primary function and in satisfying complex requirements for physical and functional interfaces between systems. The monolith, which houses the target, the moderators and several other essential systems, shall provide sufficient radiation shielding and retain the internal helium atmosphere properties within specified limits. Some of the associated engineering challenges are to define and meet support and alignment requirements; to find solutions for safe, robust and efficient replacement of components; to choose appropriate yet cost effective materials for the shielding structures; and to create a design that allows the construction to respect a tight installation plan. Within the monolith, the moderator and target systems, whose optimal performance is critical to the overall performance of the facility, present similarly complex design challenges. This paper presents the progress and status of the design work for the ESS target monolith as well as summarising the engineering solutions adopted for the target, moderators and other components and parts of the monolith. (author)