15 May 2023
The construction of the European Spallation Source (ESS) continues apace. The Jülich Central Institute of Engineering, Electronics and Analytics - Engineering and Technology (ZEA-1) is contributing several elementary components to the world's most powerful pulsed neutron source, which is currently being built in Lund, Sweden. These components include moderators that slow down the neutrons, which are also referred to as the "cold heart" of the ESS. The last Jülich components for the ESS target station arrived in Lund this spring.
The target station is essentially the hub of the entire neutron research facility. Protons, which were previously pushed to near the speed of light in a 500-metre-long linear accelerator, collide here with the heavy metal tungsten and knock nuclear fragments out of the tungsten atoms. The remaining highly excited residual nuclei emit 20 to 30 neutrons per incoming proton. However, these neutrons are still too fast for scientific use and have to be slowed down from 70 million to 12,000 kilometres per hour in tanks filled with hydrogen known as moderators. The moderators have to be cooled down to minus 250 °C and must also be able to withstand extreme thermal stresses.
The moderator and reflector system used for this purpose was developed and built at ZEA-1. The moderators contained within the system are also referred to as the "cold heart of the ESS" due to their shape. They are made of a special aluminium alloy from the aircraft construction industry. For a long time, the material was considered non-weldable, until the engineers at ZEA-1 developed a process over several years that made it possible to join the joints with sufficient quality using another, softer aluminium alloy.
Construction of the hydrogen cryostat at ZEA-1, which is designed to withstand a pressure load of up to 17 bar and a temperature of -253 °C, providing liquid parahydrogen to supply the moderator of the ESS.
Installation of the neutron beam port inserts (NBPI) for the neutron beam tubes at the ESS target station, the concept of which was validated and designed by ZEA-1 and manufactured by the Italian company Fantini. (Copyright: Ulrika Hammarlund/ESS)
The last Jülich components for the target station - 16 neutron beam port inserts for the neutron beam tubes - were delivered to Lund this spring. In the coming months and years until the launch of the ESS, the engineers of ZEA-1 will now work together with researchers from the Jülich Centre for Neutron Science (JCNS) on the further construction of three instruments for the ESS. The ESS was originally scheduled for completion in 2025, but this was most recently delayed to 2027 as a result of the coronavirus pandemic and technical difficulties.
Video: Target wheel - the heart of the ESS (length: 1:14 min)
Video of the installation of the ESS target wheel. The 6.5-metre-high, 13-tonne twister design, which contains the moderator and reflector system for slowing down the neutrons, can be seen in the video. Both key components were developed and manufactured at ZEA-1.
