The optimisation of instruments to exploit the long pulse at the ESS results in a large fraction of the suite that is potentially affected by high energy neutron backgrounds, a.k.a. "the prompt pulse". In this talk, I will share the current knowledge about this phenomenon that has been accumulated from a collaboration between ESS, SNS, PSI, Lund University and MAX-IV, and describe the recent design features that the ESS is adopting to reduce these effects. The design goal is achievable with mostly minor changes to current practices, and will enable any instrument to measure across frame boundaries. The solution is a cross-functional effort, involving shielding geometry and materials, proton beam optics, neutron beam optics and facility layout, and represents a concerted effort from all parts of the organisation.
Original version given at ISIS. This version 2 days later has one extra slide showing collimator blocks from ISIS, after ISIS joined our collaboration.