Ion Source Development at the SNS

The Spallation Neutron Source (SNS) now routinely operates near 1 MW of beam power on target with a highly-persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. The {approx}1 ms-long, 60 Hz, {approx}50 mA H{sup -} beam pulses are extracted from a Cs-enhanced, multi-cusp, RF-driven, internal-antenna ion source. An electrostatic LEBT (Low Energy Beam Transport) focuses the 65 kV beam into the RFQ accelerator. The ion source and LEBT have normally a combined availability of {approx}99%. Although much progress has been made over the last years to achieve this level of availability further improvements are desirable. Failures of the internal antenna and occasionally impaired electron dump insulators require several source replacements per year. An attempt to overcome the antenna issues with an AlN external antenna source early in 2009 had to be terminated due to availability issues. This report provides a comprehensive review of the design, experimental history, status, and description of recently updated components and future plans for this ion source. The mechanical design for improved electron dump vacuum feedthroughs is also presented, which is compatible with the baseline and both external antenna ion sources.