PROTON BEAM MEASUREMENT STRATEGY FOR THE 5 MW EUROPEAN SPALLATION SOURCE TARGET

Approaching construction phase in Lund, Sweden, the European Spallation Source (ESS) consists of a superconducting linear accelerator that delivers a 2 GeV, 5 MW proton beam to a rotating tungsten target. As a long pulse neutron source, the ESS does not require an accumulator ring, so the 2.86 ms pulses, with repetition rate of 14 Hz arrive directly from the linear accelerator with low emittance. To avoid damage to target station components, this intense beam must be actively expanded by quadrupoles that produce a centimetre size beamlet, combined with a fast rastering system that paints the beamlet into a 160 mm by 60 mm footprint. Upstream of and within the target station, a suite of devices will measure the beam’s density, halo, position, current, and time-of-arrival. Online density measurements are particularly important for machine protection, but present significant challenges. Diverse techniques will provide this measurement within the target station, based upon secondary emission grids, ionisation monitors, luminescent coatings, and Helium gas luminescence. Requirements, system descriptions, and performance estimates will be presented.