Electron-cloud mitigation in the Spallation Neutron Source ring

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H^- injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz. At such beam intensity, electron-cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation.