A proposed helicon driver for the SNS ion source

The Spallation Neutron Source* (SNS) employs an RFdriven, multi-cusp, H^- ion source, which utilizes a helical antenna to inductively couple power into the source plasma. To date, the source has been successfully utilized in the commissioning of the SNS accelerator producing 10-40 mA of H^- with duty-factors of ~0.1%. In the coming years, the SNS ion source will be required to inject ~60 mA into the linac with a duty-factor of 7%. This may require extraction of currents of up to ~100 mA from the ion source depending on source emittance. To date, the SNS source has only delivered sustained currents of ~30 mA at this duty factor. We are therefore exploring the possibility of meeting these requirements by combining a helicon hydrogen plasma generator recently developed in the Fusion Energy Division (FED) at ORNL with the existing SNS H^- ion source. Both these systems have been highly optimized and reflect the current state of the art in high-density hydrogen plasma production and high-brightness H- generation. The helicon plasma generator has demonstrated the capability of producing H₂ plasma densities up to an order of magnitude greater than can be achieved in the current SNS source. This report describes the technique we will employ to couple these systems as well as our plans to realize a helicon driver for the SNS ion source.