The front-end systems for the spallation neutron source

The Front-End Systems (FES) of the Spallation Neutron Source (SNS) project are being built by Berkeley Lab and will deliver a 52-mA H- ion beam at 2.5 MeV energy to the subsequent Drift-Tube Linac, to be built by Los Alamos National Laboratory. The FES comprise a volume-production, cesium-enhanced Ion Source, an electrostatic Low-Energy Beam Transport (LEBT), and RFQ accelerator, and a Medium-Energy Beam Transport (MEBT) that includes rebuncher cavities, magnetic quadrupoles, and beam diagnostics. The macro-pulse duty factor is 6%, and the macro pulses have to be chopped into a minipulse structure with a time scale of hundreds of ns, to reduce beam losses and component activation during extraction from the SNS Accumulator Ring. Delivery of the entire FES to the main SNS facility in Oak Ridge is planned for April 2002. This paper discusses the design features and status of the major FES subsystems with special emphasis on Ion Source and LEBT for which first experimental results have been obtained. After successful completion, the FES could be viewed as a prototype of a high-current, high duty-factor injector for other accelerator projects or, without the elaborate MEBT, as an independent 2.5-MeV accelerator for various applications