Long life Radio Frequency Surface Plasma Source

The development of high-performance H- ion sources is an effective method for improving the next generation of high power proton accelerators. The SNS at ORNL needs improved H- source performance to meet upgraded SNS requirements. The PIP-II Proton driver at Fermilab needs a CW H Ion Source to satisfy demanding performance specifications: 10 mA CW beam current with normalized transverse rms emittance 0.2 mm mrad, fast chopping capability, fast intensity variation, and high availability. Many other new accelerator projects need CW and pulsed H- beams with performance exceeding those achieved today. Currently, there is no H- source that satisfies such demands. In this project we propose to develop novel modifications of H- source designs which will satisfy these requirements. The new source is an advanced high duty factor (up to CW) version of a saddle antenna (SA) RF Surface Plasma Source (SPS) with improved efficiency, up to 15 mA average current, improved electrode cooling using new materials, new cesiation procedures for reduced cesium loss, longer lifetime by suppressing electrode sputtering, immunity to electrode shorting, and push button operation. The design of the advanced SPS with SA RF discharge was developed including optimized H- emitter, cesiation, beam extraction, formation, and transport. A prototype of the CW SA RF SPS has been developed and tested for validation of the feasibility to produce the necessary parameters. Relative to previous RF sources, the specific efficiency of positive ion generation was improved to 200 mA/cm2 kW (a factor of 40) and the specific efficiency of negative ion generation was improved to 20 mA/cm2 kW (a factor of8). An advanced version of the SA SPS H-source with an improved discharge cell developed in Phase I will be developed for highest intensity with the goal of having high availability and improved beam parameters: average H- beam current of 15 mA, 103 hours lifetime, integrated beam lifetime 10 A-hours. Commercial Applications and Other Benefits: The primary application of the new source to be developed in this project is for high intensity proton drivers that might be used for Spallation Neutron Sources and energy and intensity frontier discovery machines. The source is also an upgrade path for many existing and planned applications for medical treatments (including hundreds of cyclotrons with external injection for isotope production), cancer therapy, high-current tandem accelerators for Boron Neutron Capture Therapy, and homeland defense to produce resonant gamma ray techniques to detect explosives and Special Nuclear Materials.