Speaker
Description
The European Spallation Source (ESS) in Lund, Sweden, is designed to become the most powerful accelerator-driven spallation neutron source in the world. ESS is currently under construction and the first beam on target is planned for the second half of 2026, with first user operation expected to start in 2027. As a key component of neutron production, which was developed at the Institute of Technology and Engineering (ITE) of Forschungszentrum Juelich GmbH, the Moderator & Reflector Plug (MRP) slows down high-energy neutrons released from the spallation target. To gain maximum neutron brightness for condensed and soft matter research, an optimized low dimension liquid para-hydrogen moderator, the so-called Butterfly 1 (BF1), has been developed and integrated into the second generation MRP. Hydrogen with a pressure of up to 10 bar, a temperature of around 20 K and a para-hydrogen fraction of at least 0.995 will be utilized to interact with neutrons in a unique moderator vessel arrangement. This paper describes the engineering design and status of production of the second generation MRP for the ESS.