The ESS will when in operation provide a user beam for 5000 hours annually with an uptime of more than 95%. Due to the large availability all components must be designed with lifetimes longer than the facility. The lifetime of the magnetic elements depends greatly on the amount of radiation they receive. For components far away from the target the radiation comes primarily from beam losses whereas close to the target it is a combination of beam losses and back-scattered neutrons.
The ESS high energy beam transport (HEBT) line is divided into three main sections. A section in line of sight of the linac which reserve space for a future upgrade scenario (= the upgrade section), a section transporting the beam from the level of the linac tunnel to the level of the main target (= the bending section), and a section providing the desired beam footprint at the target (= the expansion section). For the first two sections the radiation level will be determined by the beam losses and for the expansion section both beam losses and back-scattered neutrons contribute.