One of the key components of the SKADI instrument, the heavy shutter, successfully passed the Site Acceptance Test (SAT) at ESS in March 2025.
SKADI is a small-angle neutron scattering (SANS) instrument that is to be constructed at the European Spallation Source (ESS, more here). SANS instruments enable the investigation of the structure of materials within the size range from Angstroms to micrometres. These highly versatile instruments cater to the scientific needs of a wide range of communities, including chemists, biologists, and physicists, and cover fields such as material and food sciences, as well as archaeology. They can analyse the micro- and mesoscopic structure of samples, as well as the spin states of magnetic samples, for example. As a broad-range instrument, SKADI offers features such as extremely flexible space for the sample environment to accommodate a wide range of experiments; a high-flux, optimised detector-collimation system to allow excellent resolution of the sample structure; and short measurement times to enable recording of internal kinetics during a sample transition.
The instrument is being developed and built through an in-kind collaboration between the Forschungszentrum Jülich and ESS, in partnership with the Laboratoire Léon Brillouin (LLB) in France.
One of the key components is the instrument shutter no. 1 (hereafter referred to as the 'heavy shutter'). Its main task is to shield and interrupt the neutron beam when necessary, for example during maintenance work on the instrument.
A vertical displacement unit raises the built-in neutron guide in the beam direction, thereby activating the beam. To interrupt the beam, the neutron guide is moved downwards, out of the beam direction, while a shielding element is positioned in the neutron beam direction.
The most significant technical challenges lie in achieving repeat positioning accuracy of ±0.05 mm for the neutron guide and enabling the displacement unit to be removed remotely. This allows maintenance and repair work on the shutter to be carried out outside the bunker. Direct access to the components in the bunker after the beam is on target cannot be guaranteed due to their high activation.
The Heavy Shutter was successfully and extensively tested at ITE. All the required parameters were met during testing. Installation at ESS took place in spring 2024. The component was successfully installed in the bunker. The ESS groups then installed and connected the necessary lines (compressed air, electrical cables, etc.) and vacuum pipes.
The site acceptance test took place in spring 2025. During this test, the functionality of all limit switches and electrical interlocks was checked.
Furthermore, a test involving 100 vertical movements (open and closed positions) was successfully carried out. The mechanics are working perfectly and the required repeat accuracy of ±0.05 mm was achieved. The SKADI Heavy Shutter is ready for operation with the neutron beam.
Access to the bunker will be restricted from July 2025 onwords. The components installed in the bunker will no longer be accessible.
