Electron-cloud mitigation in the Spallation Neutron Source ring

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via Hinjection, protons of 2 MW beam power at 1 GeV kinetic energy at a repeti- tion rate of 60 Hz (1). At such beam intensity, electron- cloud is expected to be one of the intensity-limiting mech- anisms that complicate ring operations. This paper summa- rizes mitigation strategy adopted in the design, both in sup- pressing electron-cloud formation and in enhancing Lan- dau damping, including tapered magnetic field and moni- toring system for the collection of stripped electrons at in- jection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injec- tion region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation.