Development Of The SNS External Antenna H- Ion Source

The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility currently in the process of ramping up neutron production. To meet present and future beam current and reliability requirements we are developing an RF-driven, H- ion source based on a ceramic aluminium nitride (AlN) plasma chamber surrounded by an external RF antenna. This report recounts the design of the prototype source, describes the Cs collar variations tested, enumerates recent modifications made to the source to prepare a production version, and summarizes the results of runs on the SNS test stand and Front End (FE) of the SNS accelerator. Up to ∼100 mA unanalyzed beam currents (60Hz, 1ms) have been measured on the SNS ion source test stand, and up to 42mA have been successfully accelerated by the RFQ on the SNS front-end at lower RF power.