ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
We use the ORBIT particle tracking code to simulate the propagation of 545 keV electrons stripped from 1 GeV H- ions during injection into the Spallation Neutron Source accumulator ring. The electrons propagate in the field of the injection magnet and are subject to scattering at the bottom surface when they are not caught by the electron catcher in the design fashion. The scattered electrons have the potential to intercept and damage local hardware. We model the non-caught electrons and compare our simulated results with experimental observations.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
LANL, Los Alamos, New Mexico
BNL, Upton, Long Island, New York
The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H0 excited states created during the H− charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H− beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and contribute to foil and bracket failure. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we will detail these and other interesting failure mechanisms, and describe the improvements we have made to mitigate them.
