The future of the E-P Instability in the SNS Accumulator Ring

Abstract

Concerns about the e-p instability drove many decisions during the design of the accumulator ring for Oak Ridge’s Spallation Neutron Source. To date, these decisions seem justified since e-p activity has been observed at the mm scale as a broadband transverse excitation, but it has not been a limiting factor (or even a contributor to normal losses) during operation up to the design power of 1.4 MW. However, the proton power upgrade (PPU) [1] will increase beam energy from 1.0 GeV to 1.3 GeV to allow 2.0 MW operation on the first target station, and eventually the Second Target Station project (STS) [2] will require an increase in beam current in the ring of about 50% above current operation resulting in 2.8 MW beam. This paper explores the potential for e-p induced beam instability during PPU and STS operation, the predicted effectiveness of existing e-p mitigation measures in the SNS ring, and potential experiments to test these predictions within current operational limitations.