H-Ion Sources for High Intensity Proton Drivers

Spallation neutron source user facilities require reliable, intense beams of protons. The technique of H- charge exchange injection into a storage ring or synchrotron has the potential to provide the needed beam currents. However, the facility operation is limited by the performance of H- ion sources with currents, brightness, reliability and availability that could still be improved. In this project we will develop an H- source design which will synthesize the most important developments in the field of negative ion sources to provide high current, small emittance, good lifetime, and high reliability, by improving power efficiency. Several versions of new plasma generators with different antennas and magnetic field configurations were designed, built and tested on a test stand, where a factor of 5 improvements in useful plasma flux generation was demonstrated. These plasma generators are compatible with the SNS RF H- Source and were tested on the SNS Test Stand. Stable H- beam production up to 56 kW RF power was demonstrated with a beam current up to 67 mA using a prototype saddle antenna. An H- ion generation efficiency of 1.6 mA/kW was also demonstrated. An advanced version of an RF H-source with an improved plasma generator (developed in Phase I) will be developed in full scale with the goal of having a long operational lifetime with improved beam parameters (pulsed H- beam current up to 70 mA, average H- beam current up to 5 mA with pulsed power <40 kW and beam normalized rms emittance <0.25 ! mm mrad). The primary application of the new source to be developed in this project is the next upgrade of the Oak Ridge Spallation Neutron Source to higher reliability at higher beam power levels. The source would also be an essential component of a proton driver that might be used for muon colliders. However, the source would be an upgrade path for all other existing and planned applications such as medical treatments (including cyclotrons with external ion injection for cancer therapy, and high current tandem accelerators for Boron Neutron Capture Therapy), homeland defense (e.g. production of muons for cargo scanning or resonant gamma ray techniques to detect explosives), and ion implantation for semiconductor development and material modification.