ESS can be likened to a microscope, but instead of light, neutrons are used. They penetrate the material and provide information about how the material is built up and how it works.
Hydrogen atomic nuclei – protons – are accelerated with the help of magnets. They reach up close to the speed of light in a 600 metre long accelerator tube. The protons are ejected into a target station, where mercury, lead, lead/bismuth alloy or tungsten/tantalum is enclosed in a vessel with several tight clasps. When the protons hit the atomic nuclei in the target material, neutrons are being knocked off from the atomic nuclei. This is what is known as the spallation process. These neutrons are then directed in tubes to the scattering instruments, where they are used for examining different material. Part of the target material that is used in the ESS facility will be radioactive, but it is kept in a closed system for the duration of the facility’s lifetime of a good 40 years. Only a small part of the metal is consumed during spallation. The amount that is put in at the start lasts for the facility’s entire lifetime.