The development of a high-power, H- ion source for the sns based on an external antenna

The ion source originally developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp H- source, which utilizes an internal antenna immersed within the source plasma. To date, the source has been utilized successfully in commissioning of the SNS accelerator delivering 10 - 40 mA with duty-factors of ∼0.1% for periods of several weeks. In the near future, the SNS facility will require beam currents of ∼40-60 mA at ∼7% duty-factor. Tests have shown that the internal antenna is susceptible to failure at this high duty-factor. Currently, two ion sources are being developed which feature ceramic plasma chambers surrounded by an external antenna. The first is a simple, prototype source allowing beam extraction experiments to be performed at low duty-factor. This source has already produced considerably higher H- beam currents than the original SNS source when both are operated without Cs. The second ion source is a high-power version which features an integrated metallic Faraday shield - magnetic multicusp structure and is designed to operate at full dutyfactor. Details of this design and the measured performance of the prototype source are discussed.